1
|
Pichl L, Konietzko K, Hartmann L, Puscasu B, Jiménez Klingberg C. Moleculargenetic and in Addition Partly Discrepant Infection Serological Malaria Testing in Two Blood Donors. Transfus Med Hemother 2024; 51:119-121. [PMID: 38584697 PMCID: PMC10996037 DOI: 10.1159/000530141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 03/08/2023] [Indexed: 04/09/2024] Open
Abstract
Introduction According to the guidelines (GL) valid in Germany, persons born or raised in a malaria-endemic area or had continuously stayed in a malaria-endemic area for more than 6 months may only be admitted donating blood if, among other things, validated and quality-assured laboratory diagnostics show that there is no evidence of infectivity. In a statement of the Working Group "Blood" of the Federal Ministry of Health (WGB), a reduction of the deferral period from 4 to 3 years and an antibody test after the deferral period are recommended. Methods In accordance with the GL, nucleic acid testing (NAT) by means of PCR is carried out at our institution after a retention period of 4 years. In addition to the validated molecular biological testing, an infection serological examination was performed. Case Presentation In the present cases, Plasmodia genome was detected in the respective single PCR in two blood donors originating from malaria-endemic areas after the expiry of the deferral period. However, one donor tested negative for antibodies against Plasmodia. Discussion/Conclusion This observation is discussed in the context of a recommendation of the WGB. The question is addressed whether PCR testing is dispensable or whether a combination of infection serological testing and NAT should be favored.
Collapse
Affiliation(s)
- Lutz Pichl
- DRK-Blutspendedienst West gGmbH, Zentrallabor, Hagen, Germany
| | - Katja Konietzko
- DRK-Blutspendedienst West gGmbH, Zentrallabor, Hagen, Germany
| | - Ludwig Hartmann
- DRK-Blutspendedienst West gGmbH, Zentrallabor, Hagen, Germany
| | - Bogdan Puscasu
- DRK-Blutspendedienst West gGmbH, Zentrallabor, Hagen, Germany
| | | |
Collapse
|
2
|
Calderaro A, Piccolo G, Chezzi C. The Laboratory Diagnosis of Malaria: A Focus on the Diagnostic Assays in Non-Endemic Areas. Int J Mol Sci 2024; 25:695. [PMID: 38255768 PMCID: PMC10815132 DOI: 10.3390/ijms25020695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 12/26/2023] [Accepted: 01/03/2024] [Indexed: 01/24/2024] Open
Abstract
Even if malaria is rare in Europe, it is a medical emergency and programs for its control should ensure both an early diagnosis and a prompt treatment within 24-48 h from the onset of the symptoms. The increasing number of imported malaria cases as well as the risk of the reintroduction of autochthonous cases encouraged laboratories in non-endemic countries to adopt diagnostic methods/algorithms. Microscopy remains the gold standard, but with limitations. Rapid diagnostic tests have greatly expanded the ability to diagnose malaria for rapid results due to simplicity and low cost, but they lack sensitivity and specificity. PCR-based assays provide more relevant information but need well-trained technicians. As reported in the World Health Organization Global Technical Strategy for Malaria 2016-2030, the development of point-of-care testing is important for the improvement of diagnosis with beneficial consequences for prompt/accurate treatment and for preventing the spread of the disease. Despite their limitations, diagnostic methods contribute to the decline of malaria mortality. Recently, evidence suggested that artificial intelligence could be utilized for assisting pathologists in malaria diagnosis.
Collapse
Affiliation(s)
- Adriana Calderaro
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (G.P.); (C.C.)
| | | | | |
Collapse
|
3
|
Bechtold P, Wagner P, Hosch S, Gregorini M, Stark WJ, Gody JC, Kodia-Lenguetama ER, Pagonendji MS, Donfack OT, Phiri WP, García GA, Nsanzanbana C, Daubenberger CA, Schindler T, Vickos U. Development and evaluation of PlasmoPod: A cartridge-based nucleic acid amplification test for rapid malaria diagnosis and surveillance. PLOS GLOBAL PUBLIC HEALTH 2023; 3:e0001516. [PMID: 37756280 PMCID: PMC10529553 DOI: 10.1371/journal.pgph.0001516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 09/04/2023] [Indexed: 09/29/2023]
Abstract
Malaria surveillance is hampered by the widespread use of diagnostic tests with low sensitivity. Adequate molecular malaria diagnostics are often only available in centralized laboratories. PlasmoPod is a novel cartridge-based nucleic acid amplification test for rapid, sensitive, and quantitative detection of malaria parasites. PlasmoPod is based on reverse-transcription quantitative polymerase chain reaction (RT-qPCR) of the highly abundant Plasmodium spp. 18S ribosomal RNA/DNA biomarker and is run on a portable qPCR instrument which allows diagnosis in less than 30 minutes. Our analytical performance evaluation indicates that a limit-of-detection as low as 0.02 parasites/μL can be achieved and no cross-reactivity with other pathogens common in malaria endemic regions was observed. In a cohort of 102 asymptomatic individuals from Bioko Island with low malaria parasite densities, PlasmoPod accurately detected 83 cases, resulting in an overall detection rate of 81.4%. Notably, there was a strong correlation between the Cq values obtained from the reference RT-qPCR assay and those obtained from PlasmoPod. In an independent cohort, using dried blood spots from malaria symptomatic children living in the Central African Republic, we demonstrated that PlasmoPod outperforms malaria rapid diagnostic tests based on the PfHRP2 and panLDH antigens as well as thick blood smear microscopy. Our data suggest that this 30-minute sample-to-result RT-qPCR procedure is likely to achieve a diagnostic performance comparable to a standard laboratory-based RT-qPCR setup. We believe that the PlasmoPod rapid NAAT could enable widespread accessibility of high-quality and cost-effective molecular malaria surveillance data through decentralization of testing and surveillance activities, especially in elimination settings.
Collapse
Affiliation(s)
- Philippe Bechtold
- Institute for Chemical and Bioengineering, ETH Zurich, Zuerich, Switzerland
- Diaxxo AG, Zuerich, Switzerland
| | - Philipp Wagner
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Salome Hosch
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Michele Gregorini
- Institute for Chemical and Bioengineering, ETH Zurich, Zuerich, Switzerland
- Diaxxo AG, Zuerich, Switzerland
| | - Wendelin J. Stark
- Institute for Chemical and Bioengineering, ETH Zurich, Zuerich, Switzerland
- Diaxxo AG, Zuerich, Switzerland
| | - Jean Chrysostome Gody
- Paediatric Hospital and University Complex of Bangui, Bangui, Central African Republic
| | | | | | | | | | | | - Christian Nsanzanbana
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Claudia A. Daubenberger
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Tobias Schindler
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Ulrich Vickos
- Infectious and Tropical Diseases Unit, Department of Medicine, Amitié Hospital, Bangui, Central African Republic
- Microbiology and Diagnostic Immunology Unit, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy
| |
Collapse
|
4
|
van Bergen KJM, Stuitje AR, Akkers RC, Vermeer HJ, Castel R, Mank TG. Performance of a novel melting curve-based qPCR assay for malaria parasites in routine clinical practice in non-endemic setting. Malar J 2023; 22:191. [PMID: 37349789 DOI: 10.1186/s12936-023-04617-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Accepted: 06/06/2023] [Indexed: 06/24/2023] Open
Abstract
BACKGROUND High-quality malaria diagnosis is essential for effective treatment and clinical disease management. Microscopy and rapid diagnostic tests are the conventional methods performed as first-line malaria diagnostics in non-endemic countries. However, these methods lack the characteristic to detect very low parasitaemia, and accurate identification of the Plasmodium species can be difficult. This study evaluated the performance of the MC004 melting curve-based qPCR for the diagnosis of malaria in routine clinical practice in non-endemic setting. METHODS AND RESULTS Whole blood samples were collected from 304 patients with clinical suspicion of malaria and analysed by both the MC004 assay and conventional diagnostics. Two discrepancies were found between the MC004 assay and microscopy. Repeated microscopic analysis confirmed the qPCR results. Comparison of the parasitaemia of nineteen Plasmodium falciparum samples determined by both microscopy and qPCR showed the potential of the MC004 assay to estimate the parasite load of P. falciparum. Eight Plasmodium infected patients were followed after anti-malarial treatment by the MC004 assay and microscopy. The MC004 assay still detected Plasmodium DNA although no parasites were seen with microscopy in post-treatment samples. The rapid decline in Plasmodium DNA showed the potential for therapy-monitoring. CONCLUSION Implementation of the MC004 assay in non-endemic clinical setting improved the diagnosis of malaria. The MC004 assay demonstrated superior Plasmodium species identification, the ability to indicate the Plasmodium parasite load, and can potentially detect submicroscopic Plasmodium infections.
Collapse
Affiliation(s)
- Kim J M van Bergen
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands.
| | - Antoine R Stuitje
- MRC Holland, Willem Schoutenstraat 1, 1057 DL, Amsterdam, The Netherlands
| | - Robert C Akkers
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands
| | - Henricus J Vermeer
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands
| | - Rob Castel
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands
| | - Theo G Mank
- Regional Laboratory for Medical Microbiology and Public Health, Boerhaavelaan 26, 2035 RC, Haarlem, The Netherlands
| |
Collapse
|
5
|
Fontecha G, Escobar D, Ortiz B, Pinto A. A PCR-RFLP Technique to Assess the Geographic Origin of Plasmodium falciparum Strains in Central America. Trop Med Infect Dis 2022; 7:tropicalmed7080149. [PMID: 35893657 PMCID: PMC9394469 DOI: 10.3390/tropicalmed7080149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/23/2022] [Accepted: 07/25/2022] [Indexed: 11/20/2022] Open
Abstract
The elimination of malaria requires strengthening diagnosis and offering adequate and timely treatment. Imported cases of falciparum malaria represent a major challenge for pre-elimination areas, such as Central America, where chloroquine and primaquine continue to be used as first-line treatment. The pfs47 gene has been previously described as a precise molecular marker to track the geographic origin of the parasite. The aim of this study was to design a simple and low-cost technique using the polymorphic region of pfs47 to assess the geographic origin of P. falciparum strains. A PCR-RFLP technique was developed and evaluated using the MseI enzyme that proved capable of discriminating, with reasonable precision, the geographical origin of the parasites. This method could be used by national surveillance laboratories and malaria elimination programs in countries such as Honduras and Nicaragua in cases of malaria where an origin outside the Central American isthmus is suspected.
Collapse
|
6
|
Beshir KB, Parr JB, Cunningham J, Cheng Q, Rogier E. Screening strategies and laboratory assays to support Plasmodium falciparum histidine-rich protein deletion surveillance: where we are and what is needed. Malar J 2022; 21:201. [PMID: 35751070 PMCID: PMC9233320 DOI: 10.1186/s12936-022-04226-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 06/17/2022] [Indexed: 11/10/2022] Open
Abstract
Rapid diagnostic tests (RDTs) detecting Plasmodium falciparum histidine-rich protein 2 (HRP2) have been an important tool for malaria diagnosis, especially in resource-limited settings lacking quality microscopy. Plasmodium falciparum parasites with deletion of the pfhrp2 gene encoding this antigen have now been identified in dozens of countries across Asia, Africa, and South America, with new reports revealing a high prevalence of deletions in some selected regions. To determine whether HRP2-based RDTs are appropriate for continued use in a locality, focused surveys and/or surveillance activities of the endemic P. falciparum population are needed. Various survey and laboratory methods have been used to determine parasite HRP2 phenotype and pfhrp2 genotype, and the data collected by these different methods need to be interpreted in the appropriate context of survey and assay utilized. Expression of the HRP2 antigen can be evaluated using point-of-care RDTs or laboratory-based immunoassays, but confirmation of a deletion (or mutation) of pfhrp2 requires more intensive laboratory molecular assays, and new tools and strategies for rigorous but practical data collection are particularly needed for large surveys. Because malaria diagnostic strategies are typically developed at the national level, nationally representative surveys and/or surveillance that encompass broad geographical areas and large populations may be required. Here is discussed contemporary assays for the phenotypic and genotypic evaluation of P. falciparum HRP2 status, consider their strengths and weaknesses, and highlight key concepts relevant to timely and resource-conscious workflows required for efficient diagnostic policy decision making.
Collapse
Affiliation(s)
- Khalid B Beshir
- Faculty of Infectious Diseases, London School of Hygiene and Tropical Diseases, Keppel Street, London, WC1E 7HT, UK
| | - Jonathan B Parr
- Division of Infectious Diseases and Institute for Global Health and Infectious Diseases, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Jane Cunningham
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | - Qin Cheng
- Drug Resistance and Diagnostics, Australian Defence Force Malaria and Infectious Disease Institute, Brisbane, Australia.,QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Eric Rogier
- Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, 30029, USA.
| |
Collapse
|
7
|
Mooney JP, DonVito SM, Jahateh M, Bittaye H, Keith M, Galloway LJ, Ndow M, Cunnington AJ, D'Alessandro U, Bottomley C, Riley EM. 'Bouncing Back' From Subclinical Malaria: Inflammation and Erythrocytosis After Resolution of P. falciparum Infection in Gambian Children. Front Immunol 2022; 13:780525. [PMID: 35154104 PMCID: PMC8831762 DOI: 10.3389/fimmu.2022.780525] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 01/03/2022] [Indexed: 11/13/2022] Open
Abstract
Recent malaria is associated with an increased risk of systemic bacterial infection. The aetiology of this association is unclear but malaria-related haemolysis may be one contributory factor. To characterise the physiological consequences of persistent and recently resolved malaria infections and associated haemolysis, 1650 healthy Gambian children aged 8-15 years were screened for P. falciparum infection (by 18sRNA PCR) and/or anaemia (by haematocrit) at the end of the annual malaria transmission season (t1). P. falciparum-infected children and children with moderate or severe anaemia (haemoglobin concentration < 11g/dl) were age matched to healthy, uninfected, non-anaemic controls and screened again 2 months later (t2). Persistently infected children (PCR positive at t1 and t2) had stable parasite burdens and did not differ significantly haematologically or in terms of proinflammatory markers from healthy, uninfected children. However, among persistently infected children, IL-10 concentrations were positively correlated with parasite density suggesting a tolerogenic response to persistent infection. By contrast, children who naturally resolved their infections (positive at t1 and negative at t2) exhibited mild erythrocytosis and concentrations of pro-inflammatory markers were raised compared to other groups of children. These findings shed light on a 'resetting' and potential overshoot of the homeostatic haematological response following resolution of malaria infection. Interestingly, the majority of parameters tested were highly heterogeneous in uninfected children, suggesting that some may be harbouring cryptic malaria or other infections.
Collapse
Affiliation(s)
- Jason P Mooney
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Sophia M DonVito
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Maimuna Jahateh
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Haddy Bittaye
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Marianne Keith
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Lauren J Galloway
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Mortala Ndow
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Aubrey J Cunnington
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College London, London, United Kingdom
| | - Umberto D'Alessandro
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Christian Bottomley
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Eleanor M Riley
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| |
Collapse
|
8
|
Calderaro A, Montecchini S, Buttrini M, Piccolo G, Rossi S, Arcangeletti MC, Farina B, De Conto F, Chezzi C. Malaria Diagnosis in Non-Endemic Settings: The European Experience in the Last 22 Years. Microorganisms 2021; 9:microorganisms9112265. [PMID: 34835391 PMCID: PMC8620059 DOI: 10.3390/microorganisms9112265] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/25/2021] [Accepted: 10/26/2021] [Indexed: 11/16/2022] Open
Abstract
Accurate, prompt, and reliable tools for the diagnosis of malaria are crucial for tracking the successes or drawbacks of control and elimination efforts, and for future programs aimed at global malaria eradication. Although microscopy remains the gold standard method, the number of imported malaria cases and the risk of reappearance of autochthonous cases stimulated several laboratories located in European countries to evaluate methods and algorithms suited to non-endemic settings, where skilled microscopists are not always available. In this review, an overview of the field evaluation and a comparison of the methods used for the diagnosis of malaria by European laboratories is reported, showing that the development of numerous innovations is continuous. In particular, the combination of rapid diagnostic tests and molecular assays with microscopy represents a reliable system for the early diagnosis of malaria in non-endemic settings.
Collapse
Affiliation(s)
- Adriana Calderaro
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
- Correspondence: ; Tel.: +39-0521-033499; Fax: +39-0521-993620
| | - Sara Montecchini
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
| | - Mirko Buttrini
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
| | - Giovanna Piccolo
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
| | - Sabina Rossi
- Unit of Clinical Microbiology, University Hospital of Parma, Viale A. Gramsci 14, 43126 Parma, Italy;
| | - Maria Cristina Arcangeletti
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
| | - Benedetta Farina
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
| | - Flora De Conto
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
| | - Carlo Chezzi
- Department of Medicine and Surgery, University of Parma, Viale A. Gramsci 14, 43126 Parma, Italy; (S.M.); (M.B.); (G.P.); (M.C.A.); (B.F.); (F.D.C.); (C.C.)
| |
Collapse
|
9
|
van Bergen K, Stuitje T, Akkers R, Vermeer E, Castel R, Mank T. Evaluation of a novel real-time PCR assay for the detection, identification and quantification of Plasmodium species causing malaria in humans. Malar J 2021; 20:314. [PMID: 34247622 PMCID: PMC8274047 DOI: 10.1186/s12936-021-03842-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 07/03/2021] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND The entry of PCR-based techniques into malaria diagnostics has improved the sensitivity and specificity of the detection of Plasmodium infections. It has been shown that humans are regularly infected by at least six different Plasmodium species. The MC004 real-time PCR assay for malaria diagnosis is a novel single-tube assay that has been developed for the purpose of simultaneously detecting all Plasmodium species known to infect humans, and discrimination between Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale wallikeri, Plasmodium ovale curtisi, Plasmodium knowlesi (including differentiation of three strains) and Plasmodium cynomolgi (including differentiation of three strains). Detection and identification of Plasmodium species relies on molecular beacon probe-based melting curve analysis. In addition, this assay might be used to quantify the parasitaemia of at least P. falciparum by calculating the level of parasitaemia directly from the Cq-value. METHODS The samples used in this study comprised reference samples, patient samples, and synthetic controls. The following analytical performance characteristics of the MC004 assay were determined: analytical specificity, limit of detection, the ability to detect mixed infections, and the potential to determine the level of parasitaemia of P. falciparum, including assessment of within-run and between-run precisions. RESULTS No false positive or false negative results were observed. The limit of detection of P. falciparum was 1 × 10-3 IU/mL (WHO standard). Mixed infections with P. falciparum and non-falciparum species were correctly identified. A calibration curve could be established to quantify the parasitaemia of at least P. falciparum. The within-run and between-run precisions were less than 20% CV at the tested parasitaemia levels of 0.09%, 0.16%, 2.15% and 27.27%. CONCLUSION Based upon the analytical performance characteristics that were determined, the MC004 assay showed performance suitable for use in clinical settings, as well as epidemiological studies.
Collapse
Affiliation(s)
- Kim van Bergen
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands
| | - Toon Stuitje
- MRC Holland, Willem Schoutenstraat 1, 1057 DL, Amsterdam, The Netherlands
| | - Robert Akkers
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands
| | - Eric Vermeer
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands
| | - Rob Castel
- Result Laboratorium, Albert Schweitzer Hospital, Albert Schweitzerplaats 25, 3300 AK, Dordrecht, The Netherlands.
| | - Theo Mank
- Streeklaboratorium Voor de Volksgezondheid Kennemerland, Boerhaavelaan 26, 2035 RC, Haarlem, The Netherlands
| |
Collapse
|
10
|
Rocha D, de Melo GC, Carneiro JMH, Ribeiro M, Ribeiro S, de Godoy DT, Costa E, de Almeida ACG, de Andrade EF, Abrahim CMDM, Fraiji NA, Ferreira AGP, Monteiro WM, Brindeiro R, Tanuri A, de Lacerda MVG, Alvarez P. Use of a NAT-based assay to improve the surveillance system and prevent transfusion-transmitted malaria in blood banks. Malar J 2020; 19:275. [PMID: 32736625 PMCID: PMC7395345 DOI: 10.1186/s12936-020-03345-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 07/23/2020] [Indexed: 02/04/2023] Open
Abstract
Background Malaria can be transmitted by blood transfusion through donations collected from asymptomatic donors. Transfusion-transmitted malaria (TTM) poses a great risk to blood services worldwide. A good screening tool for Plasmodium spp. detection in blood banks must have a high sensitivity for prevention of TTM. However, in Brazilian blood banks, screening for malaria still relies on microscopy. Methods In Brazil, screening for human immunodeficiency virus type 1 (HIV), RNA/DNA for hepatitis C (HCV) and hepatitis B (HBV) viruses is mandatory for every blood donation and uses nucleic acid amplification testing (NAT). The aim of this study was to evaluate the inclusion of an assay for malaria to identify Plasmodium sp. from total nucleic acid (TNA; DNA/RNA) by targeting the 18S rRNA gene of the parasite. Results Considering the limitations of microscopy and the wide availability of the Brazilian NAT platform in the screening of blood units for HIV, HCV, and HBV, a molecular diagnostic tool was validated for detection of Plasmodium sp. in blood banks; a pilot study showed that using this novel NAT assay could reduce the risk of TTM. Conclusion The prototype HIV/HCV/HBV/malaria NAT assay was effective in detecting infected candidate donors and has good prospects to be applied in routine screening for preventing TTM.
Collapse
Affiliation(s)
- Daniele Rocha
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil.,Departamento de Genética, Universidade Federal do Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil
| | - Gisely Cardoso de Melo
- Instituto de Pesquisa Clínica Carlos Borborema, Fundação de Medicina Tropical Heitor Vieira Dourado, Manaus, Amazonas, Brazil.,Universidade do Estado do Amazonas, Manaus, Amazonas, Brazil
| | | | - Marisa Ribeiro
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil.,Departamento de Genética, Universidade Federal do Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil
| | - Sthefanie Ribeiro
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil
| | - Daniela Tupy de Godoy
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil
| | - Elaine Costa
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil
| | - Anne Cristine Gomes de Almeida
- Instituto de Pesquisa Clínica Carlos Borborema, Fundação de Medicina Tropical Heitor Vieira Dourado, Manaus, Amazonas, Brazil
| | - Elisabete Ferreira de Andrade
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil.,Departamento de Genética, Universidade Federal do Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil
| | | | - Nelson Abrahim Fraiji
- HEMOAM-Fundação Hospitalar de Hematologia e Hemoterapia do Amazonas, Manaus, Amazonas, Brazil
| | - Antonio Gomes Pinto Ferreira
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil
| | - Wuelton Marcelo Monteiro
- Instituto de Pesquisa Clínica Carlos Borborema, Fundação de Medicina Tropical Heitor Vieira Dourado, Manaus, Amazonas, Brazil.,Universidade do Estado do Amazonas, Manaus, Amazonas, Brazil
| | - Rodrigo Brindeiro
- Departamento de Genética, Universidade Federal do Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil
| | - Amilcar Tanuri
- Departamento de Genética, Universidade Federal do Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil
| | - Marcus Vinicius Guimarães de Lacerda
- Instituto de Pesquisa Clínica Carlos Borborema, Fundação de Medicina Tropical Heitor Vieira Dourado, Manaus, Amazonas, Brazil.,Universidade do Estado do Amazonas, Manaus, Amazonas, Brazil.,Instituto de Pesquisas Leônidas e Maria Deane, Fiocruz, Manaus, Amazonas, Brazil
| | - Patrícia Alvarez
- Institute of Technology in Immunobiology Bio-Manguinhos, Oswaldo Cruz Foundation/Fiocruz, Avenida Brasil 4365, Rio de Janeiro, Brazil.
| |
Collapse
|
11
|
Guirou EA, Schindler T, Hosch S, Donfack OT, Yoboue CA, Krähenbühl S, Deal A, Cosi G, Gondwe L, Mwangoka G, Masuki H, Salim N, Mpina M, Said J, Abdulla S, Hoffman SL, Nlavo BM, Maas C, Falla CC, Phiri WP, Garcia GA, Tanner M, Daubenberger C. Molecular malaria surveillance using a novel protocol for extraction and analysis of nucleic acids retained on used rapid diagnostic tests. Sci Rep 2020; 10:12305. [PMID: 32703999 PMCID: PMC7378824 DOI: 10.1038/s41598-020-69268-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 07/10/2020] [Indexed: 11/09/2022] Open
Abstract
The use of malaria rapid diagnostic tests (RDTs) as a source for nucleic acids that can be analyzed via nucleic acid amplification techniques has several advantages, including minimal amounts of blood, sample collection, simplified storage and shipping conditions at room temperature. We have systematically developed and extensively evaluated a procedure to extract total nucleic acids from used malaria RDTs. The co-extraction of DNA and RNA molecules from small volumes of dried blood retained on the RDTs allows detection and quantification of P. falciparum parasites from asymptomatic patients with parasite densities as low as 1 Pf/µL blood using reverse transcription quantitative PCR. Based on the extraction protocol we have developed the ENAR (Extraction of Nucleic Acids from RDTs) approach; a complete workflow for large-scale molecular malaria surveillance. Using RDTs collected during a malaria indicator survey we demonstrated that ENAR provides a powerful tool to analyze nucleic acids from thousands of RDTs in a standardized and high-throughput manner. We found several, known and new, non-synonymous single nucleotide polymorphisms in the propeller region of the kelch 13 gene among isolates circulating on Bioko Island, Equatorial Guinea.
Collapse
Affiliation(s)
- Etienne A Guirou
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Tobias Schindler
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Salome Hosch
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | | | - Charlene Aya Yoboue
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Silvan Krähenbühl
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Anna Deal
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Glenda Cosi
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Linda Gondwe
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Ifakara Health Institute, Bagamoyo Branch, United Republic of Tanzania
| | - Grace Mwangoka
- Ifakara Health Institute, Bagamoyo Branch, United Republic of Tanzania
| | - Heavenlight Masuki
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences, Dar Es Salaam, Tanzania
| | - Nahya Salim
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences, Dar Es Salaam, Tanzania
| | - Maxmillian Mpina
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Ifakara Health Institute, Bagamoyo Branch, United Republic of Tanzania
| | - Jongo Said
- Ifakara Health Institute, Bagamoyo Branch, United Republic of Tanzania
| | - Salim Abdulla
- Ifakara Health Institute, Bagamoyo Branch, United Republic of Tanzania
| | | | | | - Carl Maas
- Marathon EG Production Ltd, Malabo, Equatorial Guinea
| | | | - Wonder P Phiri
- Medical Care Development International, Malabo, Equatorial Guinea
| | | | - Marcel Tanner
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Claudia Daubenberger
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| |
Collapse
|
12
|
Cunningham JA, Thomson RM, Murphy SC, de la Paz Ade M, Ding XC, Incardona S, Legrand E, Lucchi NW, Menard D, Nsobya SL, Saez AC, Chiodini PL, Shrivastava J. WHO malaria nucleic acid amplification test external quality assessment scheme: results of distribution programmes one to three. Malar J 2020; 19:129. [PMID: 32228615 PMCID: PMC7106789 DOI: 10.1186/s12936-020-03200-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 03/23/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The World Health Organization (WHO) recommends parasite-based diagnosis of malaria. In recent years, there has been surge in the use of various kinds of nucleic-acid amplification based tests (NAATs) for detection and identification of Plasmodium spp. to support clinical care in high-resource settings and clinical and epidemiological research worldwide. However, these tests are not without challenges, including lack (or limited use) of standards and lack of reproducibility, due in part to variation in protocols amongst laboratories. Therefore, there is a need for rigorous quality control, including a robust external quality assessment (EQA) scheme targeted towards malaria NAATs. To this effect, the WHO Global Malaria Programme worked with the UK National External Quality Assessment Scheme (UK NEQAS) Parasitology and with technical experts to launch a global NAAT EQA scheme in January 2017. METHODS Panels of NAAT EQA specimens containing five major species of human-infecting Plasmodium at various parasite concentrations and negative samples were created in lyophilized blood (LB) and dried blood spot (DBS) formats. Two distributions per year were sent, containing five LB and five DBS specimens. Samples were tested and validated by six expert referee laboratories prior to distribution. Between 37 and 45 laboratories participated in each distribution and submitted results using the online submission portal of UK NEQAS. Participants were scored based on their laboratory's stated capacity to identify Plasmodium species, and individual laboratory reports were sent which included performance comparison with anonymized peers. RESULTS Analysis of the first three distributions revealed that the factors that most significantly affected performance were sample format (DBS vs LB), species and parasite density, while laboratory location and the reported methodology used (type of nucleic acid extraction, amplification, or DNA vs RNA target) did not significantly affect performance. Referee laboratories performed better than non-referee laboratories. CONCLUSIONS Globally, malaria NAAT assays now inform a range of clinical, epidemiological and research investigations. EQA schemes offer a way for laboratories to assess and improve their performance, which is critical to safeguarding the reliability of data and diagnoses especially in situations where various NAAT methodologies and protocols are in use.
Collapse
Affiliation(s)
| | | | - Sean C Murphy
- Seattle Malaria Clinical Trials Center, Fred Hutchinson Cancer Research Center, Seattle, USA
| | - Maria de la Paz Ade
- Department of Communicable Diseases and Health Analysis, Pan American Health Organization/World Health Organization, Washington, DC, USA
| | - Xavier C Ding
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | | | - Eric Legrand
- Biology of Host-Parasite Interactions Unit, Institut Pasteur, INSERM U1201/CNRS ERL9195, Paris, France
| | - Naomi W Lucchi
- Malaria Branch, Division of Parasitic Diseases and MalariaCenter for Global Health, Centers for Disease Control and Prevention, Atlanta, USA
| | - Didier Menard
- Biology of Host-Parasite Interactions Unit, Institut Pasteur, INSERM U1201/CNRS ERL9195, Paris, France
| | - Samuel L Nsobya
- Department of Pathology, School of Biomedical Science, Makerere University, Kampala, Uganda
| | - Agatha C Saez
- UK NEQAS Parasitology, Public Health England, London, UK
| | - Peter L Chiodini
- UK NEQAS Parasitology, Public Health England, London, UK
- The Hospital for Tropical Diseases, London, UK
| | - Jaya Shrivastava
- UK NEQAS Parasitology, Public Health England, London, UK
- The Hospital for Tropical Diseases, London, UK
| |
Collapse
|
13
|
Molecular quantification of Plasmodium parasite density from the blood retained in used RDTs. Sci Rep 2019; 9:5107. [PMID: 30911048 PMCID: PMC6434039 DOI: 10.1038/s41598-019-41438-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 03/05/2019] [Indexed: 12/27/2022] Open
Abstract
Most malaria-endemic countries are heavily reliant upon rapid diagnostic tests (RDT) for malaria case identification and treatment. RDT previously used for malaria diagnosis can subsequently be used for molecular assays, including qualitative assessment of parasite species present or the carriage of resistance markers, because parasite DNA can be extracted from the blood inside the RDT which remains preserved on the internal components. However, the quantification of parasite density has not previously been possible from used RDT. In this study, blood samples were collected from school-age children in Western Kenya, in the form of both dried blood spots on Whatman filter paper, and the blood spot that is dropped into rapid diagnostic tests during use. Having first validated a robotic DNA extraction method, the parasite density was determined from both types of sample by duplex qPCR, and across a range of densities. The methods showed good agreement. The preservation of both parasite and human DNA on the nitrocellulose membrane inside the RDT was stable even after more than one year's storage. This presents a useful opportunity for researchers or clinicians wishing to gain greater information about the parasite populations that are being studied, without significant investment of resources.
Collapse
|
14
|
Paper-based microfluidics for DNA diagnostics of malaria in low resource underserved rural communities. Proc Natl Acad Sci U S A 2019; 116:4834-4842. [PMID: 30782834 PMCID: PMC6421471 DOI: 10.1073/pnas.1812296116] [Citation(s) in RCA: 192] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Populations living in remote rural communities would benefit from rapid, highly sensitive molecular, DNA-based diagnostics to inform the correct and timely treatment of infectious diseases. Such information is also becoming increasingly relevant in global efforts for disease elimination, where the testing of asymptomatic patients is now seen as being important for the identification of disease reservoirs. However, healthcare workers face practical and logistical problems in the implementation of such tests, which often involve complex instrumentation and centralized laboratories. Here we describe innovations in paper microfluidics that enable low-cost, multiplexed DNA-based diagnostics for malaria, delivered, in a first-in-human study, in schools in rural Uganda. Rapid, low-cost, species-specific diagnosis, based upon DNA testing, is becoming important in the treatment of patients with infectious diseases. Here, we demonstrate an innovation that uses origami to enable multiplexed, sensitive assays that rival polymerase chain reactions (PCR) laboratory assays and provide high-quality, fast precision diagnostics for malaria. The paper-based microfluidic technology proposed here combines vertical flow sample-processing steps, including paper folding for whole-blood sample preparation, with an isothermal amplification and a lateral flow detection, incorporating a simple visualization system. Studies were performed in village schools in Uganda with individual diagnoses being completed in <50 min (faster than the standard laboratory-based PCR). The tests, which enabled the diagnosis of malaria species in patients from a finger prick of whole blood, were both highly sensitive and specific, detecting malaria in 98% of infected individuals in a double-blind first-in-human study. Our method was more sensitive than other field-based, benchmark techniques, including optical microscopy and industry standard rapid immunodiagnostic tests, both performed by experienced local healthcare teams (which detected malaria in 86% and 83% of cases, respectively). All assays were independently validated using a real-time double-blinded reference PCR assay. We not only demonstrate that advanced, low-cost DNA-based sensors can be implemented in underserved communities at the point of need but also highlight the challenges associated with developing and implementing new diagnostic technologies in the field, without access to laboratories or infrastructure.
Collapse
|
15
|
Almeida-de-Oliveira NK, Moreira OC, de Lavigne AR, Mendonça-Lima L, Werneck GL, Daniel-Ribeiro CT, Ferreira-da-Cruz MDF. Analytical validation of real-time quantitative PCR assays for optimum diagnosis of vivax malaria. Mem Inst Oswaldo Cruz 2019; 114:e180350. [PMID: 30726341 PMCID: PMC6358008 DOI: 10.1590/0074-02760180350] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 12/26/2018] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND The prompt diagnosis of plasmodial species for effective treatment prevents
worsening of individual health and avoids transmission maintenance or even
malaria reintroduction in areas where Plasmodium does not
exist. Polymerase chain reaction (PCR) allows for the detection of parasites
below the threshold of microscopic examination. OBJECTIVE Our aim was to develop a real-time PCR test to reduce diagnostic errors and
increase efficacy. METHODS The lower limit of quantification and the linearity/analytical sensitivity
to measure sensitivity or limit of detection (LoD) were determined.
Intra-assay variations (repeatability) and alterations between assays,
operators, and instruments (reproducibility) were also assessed to set
precision. FINDINGS The linearity in SYBR™ Green and TaqMan™ systems was 106 and
102 copies and analytical sensitivity 1.13 and 1.17
copies/μL, respectively. Real-time PCR was more sensitive than conventional
PCR, showing a LoD of 0.01 parasite (p)/μL. Reproducibility and
repeatability (precision) were 100% for up to 0.1 p/μL in SYBR™ Green and 1
p/μL in TaqMan™ and conventional PCR. CONCLUSION Real-time PCR may replace conventional PCR in reference laboratories for
P. vivax detection due to its rapidity. The TaqMan™
system is the most indicated when quantification assays are required.
Performing tests in triplicate when diagnosing
Plasmodium-infected-asymptomatic individuals is recommended
to minimise diagnostic errors.
Collapse
Affiliation(s)
| | - Otacílio C Moreira
- Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Biologia Molecular e Doenças Endêmicas, Rio de Janeiro, RJ, Brasil
| | - Aline Rosa de Lavigne
- Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Pesquisa em Malária, Rio de Janeiro, RJ, Brasil
| | - Leila Mendonça-Lima
- Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Genômica Funcional e Bioinformática, Rio de Janeiro, RJ, Brasil
| | - Guilherme Loureiro Werneck
- Universidade do Estado do Rio de Janeiro, Instituto de Medicina Social, Departamento de Epidemiologia, Rio de Janeiro, RJ, Brasil
| | - Cláudio Tadeu Daniel-Ribeiro
- Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Pesquisa em Malária, Rio de Janeiro, RJ, Brasil
| | | |
Collapse
|
16
|
Standardization of Nucleic Acid Tests: the Approach of the World Health Organization. J Clin Microbiol 2019; 57:JCM.01056-18. [PMID: 30257900 DOI: 10.1128/jcm.01056-18] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The first World Health Organization (WHO) international standards (ISs) for nucleic acid amplification techniques were established two decades ago, with the initial focus on blood screening for three major viral targets, i.e., hepatitis C virus, hepatitis B virus, and human immunodeficiency virus 1. These reference materials have subsequently found utility in the diagnosis and monitoring of a wide range of infectious diseases in clinical microbiology laboratories worldwide. WHO collaborating centers develop ISs and coordinate international studies for their evaluation. The WHO Expert Committee on Biological Standardization is responsible for the endorsement of new standardization projects and the establishment of new and replacement ISs. Potencies of ISs are defined in international units (IU); the reporting in IU for assays calibrated with an IS (or secondary standards traceable to the IS) facilitates comparability of results for different assays and determination of assay parameters such as analytical sensitivities.
Collapse
|
17
|
Controlled Infection Immunization Using Delayed Death Drug Treatment Elicits Protective Immune Responses to Blood-Stage Malaria Parasites. Infect Immun 2018; 87:IAI.00587-18. [PMID: 30323025 PMCID: PMC6300636 DOI: 10.1128/iai.00587-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 09/23/2018] [Indexed: 01/27/2023] Open
Abstract
Naturally acquired immunity to malaria is robust and protective against all strains of the same species of Plasmodium. This develops as a result of repeated natural infection, taking several years to develop. Naturally acquired immunity to malaria is robust and protective against all strains of the same species of Plasmodium. This develops as a result of repeated natural infection, taking several years to develop. Evidence suggests that apoptosis of immune lymphocytes due to uncontrolled parasite growth contributes to the slow acquisition of immunity. To hasten and augment the development of natural immunity, we studied controlled infection immunization (CII) using low-dose exposure to different parasite species (Plasmodium chabaudi, P. yoelii, or P. falciparum) in two rodent systems (BALB/c and C57BL/6 mice) and in human volunteers, with drug therapy commencing at the time of initiation of infection. CIIs with infected erythrocytes and in conjunction with doxycycline or azithromycin, which are delayed death drugs targeting the parasite’s apicoplast, allowed extended exposure to parasites at low levels. In turn, this induced strong protection against homologous challenge in all immunized mice. We show that P. chabaudi/P. yoelii infection initiated at the commencement of doxycycline therapy leads to cellular or antibody-mediated protective immune responses in mice, with a broad Th1 cytokine response providing the best correlate of protection against homologous and heterologous species of Plasmodium. P. falciparum CII with doxycycline was additionally tested in a pilot clinical study (n = 4) and was found to be well tolerated and immunogenic, with immunological studies primarily detecting increased cell-associated immune responses. Furthermore, we report that a single dose of the longer-acting drug, azithromycin, given to mice (n = 5) as a single subcutaneous treatment at the initiation of infection controlled P. yoelii infection and protected all mice against subsequent challenge.
Collapse
|
18
|
Stanisic DI, Fink J, Mayer J, Coghill S, Gore L, Liu XQ, El-Deeb I, Rodriguez IB, Powell J, Willemsen NM, De SL, Ho MF, Hoffman SL, Gerrard J, Good MF. Vaccination with chemically attenuated Plasmodium falciparum asexual blood-stage parasites induces parasite-specific cellular immune responses in malaria-naïve volunteers: a pilot study. BMC Med 2018; 16:184. [PMID: 30293531 PMCID: PMC6174572 DOI: 10.1186/s12916-018-1173-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 09/11/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The continuing morbidity and mortality associated with infection with malaria parasites highlights the urgent need for a vaccine. The efficacy of sub-unit vaccines tested in clinical trials in malaria-endemic areas has thus far been disappointing, sparking renewed interest in the whole parasite vaccine approach. We previously showed that a chemically attenuated whole parasite asexual blood-stage vaccine induced CD4+ T cell-dependent protection against challenge with homologous and heterologous parasites in rodent models of malaria. METHODS In this current study, we evaluated the immunogenicity and safety of chemically attenuated asexual blood-stage Plasmodium falciparum (Pf) parasites in eight malaria-naïve human volunteers. Study participants received a single dose of 3 × 107 Pf pRBC that had been treated in vitro with the cyclopropylpyrolloindole analogue, tafuramycin-A. RESULTS We demonstrate that Pf asexual blood-stage parasites that are completely attenuated are immunogenic, safe and well tolerated in malaria-naïve volunteers. Following vaccination with a single dose, species and strain transcending Plasmodium-specific T cell responses were induced in recipients. This included induction of Plasmodium-specific lymphoproliferative responses, T cells secreting the parasiticidal cytokines, IFN-γ and TNF, and CD3+CD45RO+ memory T cells. Pf-specific IgG was not detected. CONCLUSIONS This is the first clinical study evaluating a whole parasite blood-stage malaria vaccine. Following administration of a single dose of completely attenuated Pf asexual blood-stage parasites, Plasmodium-specific T cell responses were induced while Pf-specific antibodies were not detected. These results support further evaluation of this chemically attenuated vaccine in humans. TRIAL REGISTRATION Trial registration: ACTRN12614000228684 . Registered 4 March 2014.
Collapse
Affiliation(s)
- Danielle I Stanisic
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia.
| | - James Fink
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Johanna Mayer
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Sarah Coghill
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Letitia Gore
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Xue Q Liu
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Ibrahim El-Deeb
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Ingrid B Rodriguez
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Jessica Powell
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Nicole M Willemsen
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Sai Lata De
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Mei-Fong Ho
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | | | - John Gerrard
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Michael F Good
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia.
| |
Collapse
|
19
|
Martín-Díaz A, Rubio JM, Herrero-Martínez JM, Lizasoain M, Ruiz-Giardin JM, Jaqueti J, Cuadros J, Rojo-Marcos G, Martín-Rabadán P, Calderón M, Campelo C, Velasco M, Pérez-Ayala A. Study of the diagnostic accuracy of microbiological techniques in the diagnosis of malaria in the immigrant population in Madrid. Malar J 2018; 17:314. [PMID: 30157862 PMCID: PMC6116490 DOI: 10.1186/s12936-018-2459-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 08/17/2018] [Indexed: 11/16/2022] Open
Abstract
Background Malaria is currently the most important human parasitic disease in the world responsible for high morbidity and mortality. Appropriate diagnostic methods are essential for early detection. Microscopy examination remains the gold standard, although molecular techniques have higher sensitivity and are very useful in cases of low parasitaemia and mixed infections. The objective of this study was to evaluate a new commercial molecular diagnostic technique. Methods A prospective, observational, multicentre study was performed between January 2015 and April 2017. All participants were immigrants from malaria-endemic areas, who were divided into two groups: asymptomatic group and symptomatic. Samples from both groups were evaluated by a rapid diagnostic test (ImmunoQuick® Malaria + 4 RDT), microscopy examination, and two commercial molecular malaria tests (FTD Malaria and FTD Malaria Differentiation), then compared against an in-house reference PCR technique. Results In all, 250 patients were included: 164 (65.6%) in the asymptomatic group, and 86 (34.4%) in the symptomatic group. There were seven cases of asymptomatic parasitaemia (prevalence = 2.8%) that were detected only by molecular methods. In the symptomatic group, there were seven cases of submicroscopic malaria. The main species detected was Plasmodium falciparum (96.6%). The commercial molecular technique had higher sensitivity than the other methods (S = 96%) and a high rate of concordance with the in-house reference PCR technique (Kappa score = 0.93). Conclusions The molecular techniques, although slower than microscopy, have adequate diagnostic accuracy and are very useful for the detection of P. falciparum in cases with low parasitaemia.
Collapse
Affiliation(s)
- Ariadna Martín-Díaz
- Department of Clinical Microbiology, Hospital Universitario 12 de Octubre, Avenida de Córdoba, s/n, 28041, Madrid, Spain
| | - José Miguel Rubio
- Malaria & Emerging Parasitic Diseases Laboratory, Parasitology Department, National Microbiology Centre, Instituto de Salud Carlos III, Madrid, Spain
| | | | - Manolo Lizasoain
- Internal Medicine and Infectious Diseases Department, Hospital Universitario 12 de Octubre, Madrid, Spain
| | | | | | - Juan Cuadros
- University Hospital Príncipe de Asturias, Alcalá de Henares, Madrid, Spain
| | | | | | | | | | - María Velasco
- University Hospital Fundación Alcorcón, Madrid, Spain
| | - Ana Pérez-Ayala
- Department of Clinical Microbiology, Hospital Universitario 12 de Octubre, Avenida de Córdoba, s/n, 28041, Madrid, Spain.
| |
Collapse
|
20
|
Brugman VA, Kristan M, Gibbins MP, Angrisano F, Sala KA, Dessens JT, Blagborough AM, Walker T. Detection of malaria sporozoites expelled during mosquito sugar feeding. Sci Rep 2018; 8:7545. [PMID: 29765136 PMCID: PMC5954146 DOI: 10.1038/s41598-018-26010-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 05/03/2018] [Indexed: 12/17/2022] Open
Abstract
Malaria is a severe disease of global importance transmitted by mosquitoes of the genus Anopheles. The ability to rapidly detect the presence of infectious mosquitoes able to transmit malaria is of vital importance for surveillance, control and elimination efforts. Current methods principally rely on large-scale mosquito collections followed by labour-intensive salivary gland dissections or enzyme-linked immunosorbent (ELISA) methods to detect sporozoites. Using forced salivation, we demonstrate here that Anopheles mosquitoes infected with Plasmodium expel sporozoites during sugar feeding. Expelled sporozoites can be detected on two sugar-soaked substrates, cotton wool and Whatman FTA cards, and sporozoite DNA is detectable using real-time PCR. These results demonstrate a simple and rapid methodology for detecting the presence of infectious mosquitoes with sporozoites and highlight potential laboratory applications for investigating mosquito-malaria interactions. Our results indicate that FTA cards could be used as a simple, effective and economical tool in enhancing field surveillance activities for malaria.
Collapse
Affiliation(s)
- V A Brugman
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
- Evolution Biotechnologies, Colworth Science Park, Sharnbrook, Bedford, MK44 1LZ, UK.
| | - M Kristan
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - M P Gibbins
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - F Angrisano
- Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, Imperial College Road, South Kensington, London, SW7 2AZ, UK
| | - K A Sala
- Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, Imperial College Road, South Kensington, London, SW7 2AZ, UK
| | - J T Dessens
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - A M Blagborough
- Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, Imperial College Road, South Kensington, London, SW7 2AZ, UK
| | - T Walker
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| |
Collapse
|
21
|
Beshir KB, Sepúlveda N, Bharmal J, Robinson A, Mwanguzi J, Busula AO, de Boer JG, Sutherland C, Cunningham J, Hopkins H. Plasmodium falciparum parasites with histidine-rich protein 2 (pfhrp2) and pfhrp3 gene deletions in two endemic regions of Kenya. Sci Rep 2017; 7:14718. [PMID: 29116127 PMCID: PMC5677122 DOI: 10.1038/s41598-017-15031-2] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 10/19/2017] [Indexed: 01/12/2023] Open
Abstract
Deletions of the Plasmodium falciparum hrp2 and hrp3 genes can affect the performance of HRP2-based malaria rapid diagnostic tests (RDTs). Such deletions have been reported from South America, India and Eritrea. Whether these parasites are widespread in East Africa is unknown. A total of 274 samples from asymptomatic children in Mbita, western Kenya, and 61 genomic data from Kilifi, eastern Kenya, were available for analysis. PCR-confirmed samples were investigated for the presence of pfhrp2 and pfhrp3 genes. In samples with evidence of deletion, parasite presence was confirmed by amplifying three independent genes. We failed to amplify pfhrp2 from 25 of 131 (19.1%) PCR-confirmed samples. Of these, only 8 (10%) samples were microscopic positive and were classified as pfhrp2-deleted. Eight microscopically-confirmed pfhrp2-deleted samples with intact pfhrp3 locus were positive by HRP2-based RDT. In addition, one PCR-confirmed infection showed a deletion at the pfhrp3 locus. One genomic sample lacked pfhrp2 and one lacked pfhrp3. No sample harbored parasites lacking both genes. Parasites lacking pfhrp2 are present in Kenya, but may be detectable by HRP-based RDT at higher parasitaemia, possibly due to the presence of intact pfhrp3. These findings warrant further systematic study to establish prevalence and diagnostic significance.
Collapse
Affiliation(s)
| | - Nuno Sepúlveda
- London School of Hygiene and Tropical Medicine, London, UK
- Centre for Statistics and Applications of University of Lisbon, Lisbon, Portugal
| | - Jameel Bharmal
- London School of Hygiene and Tropical Medicine, London, UK
| | - Ailie Robinson
- London School of Hygiene and Tropical Medicine, London, UK
| | | | - Annette Obukosia Busula
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
- Kaimosi Friends University College, Kaimosi, Kenya
| | - Jetske Gudrun de Boer
- Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
- Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6708 PB, Wageningen, The Netherlands
| | | | - Jane Cunningham
- Global Malaria Programme, World Health Organization (WHO-GMP), Geneva, Switzerland
| | - Heidi Hopkins
- London School of Hygiene and Tropical Medicine, London, UK
| |
Collapse
|
22
|
Perera RS, Ding XC, Tully F, Oliver J, Bright N, Bell D, Chiodini PL, Gonzalez IJ, Polley SD. Development and clinical performance of high throughput loop-mediated isothermal amplification for detection of malaria. PLoS One 2017; 12:e0171126. [PMID: 28166235 PMCID: PMC5293265 DOI: 10.1371/journal.pone.0171126] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 01/16/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Accurate and efficient detection of sub-microscopic malaria infections is crucial for enabling rapid treatment and interruption of transmission. Commercially available malaria LAMP kits have excellent diagnostic performance, though throughput is limited by the need to prepare samples individually. Here, we evaluate the clinical performance of a newly developed high throughput (HTP) sample processing system for use in conjunction with the Eiken malaria LAMP kit. METHODS The HTP system utilised dried blood spots (DBS) and liquid whole blood (WB), with parallel sample processing of 94 samples per run. The system was evaluated using 699 samples of known infection status pre-determined by gold standard nested PCR. RESULTS The sensitivity and specificity of WB-HTP-LAMP was 98.6% (95% CI, 95.7-100), and 99.7% (95% CI, 99.2-100); sensitivity of DBS-HTP-LAMP was 97.1% (95% CI, 93.1-100), and specificity 100% against PCR. At parasite densities greater or equal to 2 parasites/μL, WB and DBS HTP-LAMP showed 100% sensitivity and specificity against PCR. At densities less than 2 p/μL, WB-HTP-LAMP sensitivity was 88.9% (95% CI, 77.1-100) and specificity was 99.7% (95% CI, 99.2-100); sensitivity and specificity of DBS-HTP-LAMP was 77.8% (95% CI, 54.3-99.5) and 100% respectively. CONCLUSIONS The HTP-LAMP system is a highly sensitive diagnostic test, with the potential to allow large scale population screening in malaria elimination campaigns.
Collapse
Affiliation(s)
- Rushini S. Perera
- Department of Clinical Parasitology, Hospital for Tropical Diseases, University College London Hospitals NHS Foundation Trust, Mortimer Market, London, United Kingdom
- * E-mail:
| | | | - Frank Tully
- 42 Technology Ltd., Cambridgeshire, United Kingdom
| | - James Oliver
- 42 Technology Ltd., Cambridgeshire, United Kingdom
| | | | - David Bell
- Global Good Fund, Intellectual Ventures Laboratory, Bellevue, Washington, United States of America
| | - Peter L. Chiodini
- Department of Clinical Parasitology, Hospital for Tropical Diseases, University College London Hospitals NHS Foundation Trust, Mortimer Market, London, United Kingdom
- London School of Hygiene and Tropical Medicine, Keppel Street, London, United Kingdom
- Department of Clinical Parasitology, Health Services Laboratories LLP, Hospital for Tropical Diseases, Mortimer Market, London, United Kingdom
| | | | - Spencer D. Polley
- Department of Clinical Parasitology, Health Services Laboratories LLP, Hospital for Tropical Diseases, Mortimer Market, London, United Kingdom
| |
Collapse
|
23
|
Xu G, Nolder D, Reboud J, Oguike MC, van Schalkwyk DA, Sutherland CJ, Cooper JM. Paper-Origami-Based Multiplexed Malaria Diagnostics from Whole Blood. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606060] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Gaolian Xu
- Division of Biomedical Engineering, School of Engineering; University of Glasgow; Oakfield Avenue Glasgow G12 8LT UK
| | - Debbie Nolder
- Public Health England Malaria Reference Laboratory (PHE MRL); Faculty of Infectious & Tropical Diseases; London School of Hygiene & Tropical Medicine; UK
| | - Julien Reboud
- Division of Biomedical Engineering, School of Engineering; University of Glasgow; Oakfield Avenue Glasgow G12 8LT UK
| | - Mary C. Oguike
- Dept of Immunology & Infection; Faculty of Infectious & Tropical Diseases; London School of Hygiene & Tropical Medicine; UK
| | - Donelly A. van Schalkwyk
- Dept of Immunology & Infection; Faculty of Infectious & Tropical Diseases; London School of Hygiene & Tropical Medicine; UK
| | - Colin J. Sutherland
- Public Health England Malaria Reference Laboratory (PHE MRL); Faculty of Infectious & Tropical Diseases; London School of Hygiene & Tropical Medicine; UK
- Dept of Immunology & Infection; Faculty of Infectious & Tropical Diseases; London School of Hygiene & Tropical Medicine; UK
| | - Jonathan M. Cooper
- Division of Biomedical Engineering, School of Engineering; University of Glasgow; Oakfield Avenue Glasgow G12 8LT UK
| |
Collapse
|
24
|
Xu G, Nolder D, Reboud J, Oguike MC, van Schalkwyk DA, Sutherland CJ, Cooper JM. Paper-Origami-Based Multiplexed Malaria Diagnostics from Whole Blood. Angew Chem Int Ed Engl 2016; 55:15250-15253. [PMID: 27554333 PMCID: PMC5132111 DOI: 10.1002/anie.201606060] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Indexed: 12/22/2022]
Abstract
We demonstrate, for the first time, the multiplexed determination of microbial species from whole blood using the paper‐folding technique of origami to enable the sequential steps of DNA extraction, loop‐mediated isothermal amplification (LAMP), and array‐based fluorescence detection. A low‐cost handheld flashlight reveals the presence of the final DNA amplicon to the naked eye, providing a “sample‐to‐answer” diagnosis from a finger‐prick volume of human blood, within 45 min, with minimal user intervention. To demonstrate the method, we showed the identification of three species of Plasmodium, analyzing 80 patient samples benchmarked against the gold‐standard polymerase chain reaction (PCR) assay in an operator‐blinded study. We also show that the test retains its diagnostic accuracy when using stored or fixed reference samples.
Collapse
Affiliation(s)
- Gaolian Xu
- Division of Biomedical Engineering, School of Engineering, University of Glasgow, Oakfield Avenue, Glasgow, G12 8LT, UK
| | - Debbie Nolder
- Public Health England Malaria Reference Laboratory (PHE MRL), Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, UK
| | - Julien Reboud
- Division of Biomedical Engineering, School of Engineering, University of Glasgow, Oakfield Avenue, Glasgow, G12 8LT, UK
| | - Mary C Oguike
- Dept of Immunology & Infection, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, UK
| | - Donelly A van Schalkwyk
- Dept of Immunology & Infection, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, UK
| | - Colin J Sutherland
- Public Health England Malaria Reference Laboratory (PHE MRL), Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, UK.,Dept of Immunology & Infection, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, UK
| | - Jonathan M Cooper
- Division of Biomedical Engineering, School of Engineering, University of Glasgow, Oakfield Avenue, Glasgow, G12 8LT, UK
| |
Collapse
|
25
|
Infectivity of Plasmodium falciparum in Malaria-Naive Individuals Is Related to Knob Expression and Cytoadherence of the Parasite. Infect Immun 2016; 84:2689-96. [PMID: 27382019 DOI: 10.1128/iai.00414-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 06/27/2016] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum is the most virulent human malaria parasite because of its ability to cytoadhere in the microvasculature. Nonhuman primate studies demonstrated relationships among knob expression, cytoadherence, and infectivity. This has not been examined in humans. Cultured clinical-grade P. falciparum parasites (NF54, 7G8, and 3D7B) and ex vivo-derived cell banks were characterized. Knob and knob-associated histidine-rich protein expression, CD36 adhesion, and antibody recognition of parasitized erythrocytes (PEs) were evaluated. Parasites from the cell banks were administered to malaria-naive human volunteers to explore infectivity. For the NF54 and 3D7B cell banks, blood was collected from the study participants for in vitro characterization. All parasites were infective in vivo However, infectivity of NF54 was dramatically reduced. In vitro characterization revealed that unlike other cell bank parasites, NF54 PEs lacked knobs and did not cytoadhere. Recognition of NF54 PEs by immune sera was observed, suggesting P. falciparum erythrocyte membrane protein 1 expression. Subsequent recovery of knob expression and CD36-mediated adhesion were observed in PEs derived from participants infected with NF54. Knobless cell bank parasites have a dramatic reduction in infectivity and the ability to adhere to CD36. Subsequent infection of malaria-naive volunteers restored knob expression and CD36-mediated cytoadherence, thereby showing that the human environment can modulate virulence.
Collapse
|
26
|
Kobayashi T, Gamboa D, Ndiaye D, Cui L, Sutton PL, Vinetz JM. Malaria Diagnosis Across the International Centers of Excellence for Malaria Research: Platforms, Performance, and Standardization. Am J Trop Med Hyg 2015; 93:99-109. [PMID: 26259937 PMCID: PMC4574279 DOI: 10.4269/ajtmh.15-0004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 06/23/2015] [Indexed: 12/14/2022] Open
Abstract
Diagnosis is “the act of identifying a disease, illness, or problem by examining someone or something.” When an individual with acute fever presents for clinical attention, accurate diagnosis leading to specific, prompt treatment often saves lives. As applied to malaria, not only individual patient diagnosis is important but also assessing population-level malaria prevalence using appropriate diagnostic methods is essential for public health purposes. Similarly, identifying (diagnosing) fake antimalarial medications prevents the use of counterfeit drugs that can have disastrous effects. Therefore, accurate diagnosis in broad areas related to malaria is fundamental to improving health-care delivery, informing funding agencies of current malaria situations, and aiding in the prioritization of regional and national control efforts. The International Centers of Excellence for Malaria Research (ICEMR), supported by the U.S. National Institute of Allergy and Infectious Diseases, has collaborated on global efforts to improve malaria diagnostics by working to harmonize and systematize procedures across different regions where endemicity and financial resources vary. In this article, the different diagnostic methods used across each ICEMR are reviewed and challenges are discussed.
Collapse
Affiliation(s)
- Tamaki Kobayashi
- *Address correspondence to Tamaki Kobayashi, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, W4612, Baltimore, MD 21205, E-mail: or Joseph M. Vinetz, Division of Infectious Diseases, Department of Medicine, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093-0760, E-mail:
| | | | | | | | | | - Joseph M. Vinetz
- *Address correspondence to Tamaki Kobayashi, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, W4612, Baltimore, MD 21205, E-mail: or Joseph M. Vinetz, Division of Infectious Diseases, Department of Medicine, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093-0760, E-mail:
| |
Collapse
|
27
|
Baylis SA, Chudy M, Nübling CM. Standardization of NAT for Blood-Borne Pathogens. Transfus Med Hemother 2015; 42:211-8. [PMID: 26557812 DOI: 10.1159/000435872] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 05/31/2015] [Indexed: 12/15/2022] Open
Abstract
Assays based on nucleic acid amplification technology (NAT) are increasingly used for screening of blood and for diagnosis or monitoring of patients. Both regulatory requirements for blood screening and international recommendations for the treatment of patients are based on common reference materials available globally for the standardization of NAT assays. World Health Organization International Standards (WHO ISs) and International Reference Panels (WHO IRPs) are primary reference materials. The characterization and manufacture of WHO reference materials as well as their evaluation is performed on behalf of the WHO by collaborating centers; their establishment is decided upon by the WHO Expert Committee on Biological Standardization (ECBS). The potency of the first WHO IS is defined by the 'international unit' (IU) which should be maintained upon replacement of the IS. The IU, unlike copy number or genome equivalent, is defined by the IS with a physical existence, is available worldwide, and allows traceability and comparability of results. The anticipated use of WHO ISs is the calibration of secondary standards or the validation of essential assay features, e.g. limit of detection.
Collapse
Affiliation(s)
- Sally A Baylis
- Department of Virology, Paul-Ehrlich-Institut, Langen, Germany
| | - Michael Chudy
- Department of Virology, Paul-Ehrlich-Institut, Langen, Germany
| | - C Micha Nübling
- Department of Virology, Paul-Ehrlich-Institut, Langen, Germany ; World Health Organization, Essential Medicines and Health Products Department, Geneva, Switzerland
| |
Collapse
|
28
|
Hofmann N, Mwingira F, Shekalaghe S, Robinson LJ, Mueller I, Felger I. Ultra-sensitive detection of Plasmodium falciparum by amplification of multi-copy subtelomeric targets. PLoS Med 2015; 12:e1001788. [PMID: 25734259 PMCID: PMC4348198 DOI: 10.1371/journal.pmed.1001788] [Citation(s) in RCA: 239] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 01/08/2015] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Planning and evaluating malaria control strategies relies on accurate definition of parasite prevalence in the population. A large proportion of asymptomatic parasite infections can only be identified by surveillance with molecular methods, yet these infections also contribute to onward transmission to mosquitoes. The sensitivity of molecular detection by PCR is limited by the abundance of the target sequence in a DNA sample; thus, detection becomes imperfect at low densities. We aimed to increase PCR diagnostic sensitivity by targeting multi-copy genomic sequences for reliable detection of low-density infections, and investigated the impact of these PCR assays on community prevalence data. METHODS AND FINDINGS Two quantitative PCR (qPCR) assays were developed for ultra-sensitive detection of Plasmodium falciparum, targeting the high-copy telomere-associated repetitive element 2 (TARE-2, ∼250 copies/genome) and the var gene acidic terminal sequence (varATS, 59 copies/genome). Our assays reached a limit of detection of 0.03 to 0.15 parasites/μl blood and were 10× more sensitive than standard 18S rRNA qPCR. In a population cross-sectional study in Tanzania, 295/498 samples tested positive using ultra-sensitive assays. Light microscopy missed 169 infections (57%). 18S rRNA qPCR failed to identify 48 infections (16%), of which 40% carried gametocytes detected by pfs25 quantitative reverse-transcription PCR. To judge the suitability of the TARE-2 and varATS assays for high-throughput screens, their performance was tested on sample pools. Both ultra-sensitive assays correctly detected all pools containing one low-density P. falciparum-positive sample, which went undetected by 18S rRNA qPCR, among nine negatives. TARE-2 and varATS qPCRs improve estimates of prevalence rates, yet other infections might still remain undetected when absent in the limited blood volume sampled. CONCLUSIONS Measured malaria prevalence in communities is largely determined by the sensitivity of the diagnostic tool used. Even when applying standard molecular diagnostics, prevalence in our study population was underestimated by 8% compared to the new assays. Our findings highlight the need for highly sensitive tools such as TARE-2 and varATS qPCR in community surveillance and for monitoring interventions to better describe malaria epidemiology and inform malaria elimination efforts.
Collapse
Affiliation(s)
- Natalie Hofmann
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Felista Mwingira
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Biological Sciences Department, Dar es Salaam University College of Education, Dar es Salaam, Tanzania
| | | | - Leanne J. Robinson
- Papua New Guinea Institute of Medical Research, Madang and Maprik, Papua New Guinea
- Walter and Eliza Hall Institute, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Ivo Mueller
- Walter and Eliza Hall Institute, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- Centre de Recerca en Salut Internacional de Barcelona, Barcelona, Spain
| | - Ingrid Felger
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
| |
Collapse
|
29
|
The design and evaluation of a shaped filter collection device to sample and store defined volume dried blood spots from finger pricks. Malar J 2015; 14:45. [PMID: 25652763 PMCID: PMC4327959 DOI: 10.1186/s12936-015-0558-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 01/10/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Dried blood spots are a common medium for collecting patient blood prior to testing for malaria by molecular methods. A new shaped filter device for the quick and simple collection of a designated volume of patient blood has been designed and tested against conventional blood spots for accuracy and precision. METHODS Shaped filter devices were laser cut from Whatman GB003 paper to absorb a 20 μl blood volume. These devices were used to sample Plasmodium falciparum infected blood and the volume absorbed was measured volumetrically. Conventional blood spots were made by pipetting 20 μl of the same blood onto Whatman 3MM paper. DNA was extracted from both types of dried blood spot using Qiagen DNA blood mini or Chelex extraction for real-time PCR analysis, and PURE extraction for malaria LAMP testing. RESULTS The shaped filter devices collected a mean volume of 21.1 μl of blood, with a coefficient of variance of 8.1%. When used for DNA extraction by Chelex and Qiagen methodologies the mean number of international standard units of P. falciparum DNA recovered per μl of the eluate was 53.1 (95% CI: 49.4 to 56.7) and 32.7 (95% CI: 28.8 to 36.6), respectively for the shaped filter device, and 54.6 (95% CI: 52.1 to 57.1) and 12.0 (95% CI: 9.9 to 14.1), respectively for the 3MM blood spots. Qiagen extraction of 200 μl of whole infected blood yielded 853.6 international standard units of P. falciparum DNA per μl of eluate. CONCLUSIONS A shaped filter device provides a simple way to quickly sample and store a defined volume of blood without the need for any additional measuring devices. Resultant dried blood spots may be employed for DNA extraction using a variety of technologies for nucleic acid amplification without the need for repeated cleaning of scissors or punches to prevent cross contamination of samples and results are comparable to traditional DBS.
Collapse
|
30
|
Abstract
Light microscopy of stained blood films is still the mainstay of malaria diagnosis in many regions, but its pre-eminence is threatened by accurate and sensitive rapid diagnostic tests (RDTs) based on immunochromatography which are now widely used in the field. In well-resourced regions, nucleic acid detection easily out performs microscopy and RDTs. This paper reviews the main in vitro methods for parasite detection and considers future trends in diagnostics, both for sophisticated laboratory settings and for field use.
Collapse
|
31
|
Characterization and multicentric validation of a common standard for Toxoplasma gondii detection using nucleic acid amplification assays. J Clin Microbiol 2014; 52:3952-9. [PMID: 25187637 DOI: 10.1128/jcm.01906-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The molecular diagnosis of toxoplasmosis essentially relies upon laboratory-developed methods and suffers from lack of standardization, hence the large diversity of performances between laboratories. Moreover, quantifications of parasitic loads differ among centers, a fact which prevents the possible prediction of the severity of this disease as a function of parasitic loads. The objectives of this multicentric study performed in eight proficient laboratories of the Molecular Biology Pole of the French National Reference Center for Toxoplasmosis (NRC-T) were (i) to assess the suitability of a lyophilized preparation of Toxoplasma gondii as a common standard for use in this PCR-based molecular diagnosis and (ii) to make this standard available to the community. High-quality written procedures were used for the production and qualification of this standard. Three independent batches of this standard, containing concentrations ranging from 10(4) to 0.01 T. gondii genome equivalents per PCR, were first assessed: the linear dynamic range was ≥ 6 log, the intra-assay coefficients of variation (CV) from a sample containing 10 T. gondii organisms per PCR were 0.3% to 0.42%, and the interassay CV over a 2-week period was 0.76% to 1.47%. A further assessment in eight diagnostic centers showed that the standard is stable, robust, and reliable. These lyophilized standards can easily be produced at a larger scale when needed and can be made widely available at the national level. To our knowledge, this is the first quality control assessment of a common standard which is usable both for self-evaluation in laboratories and for accurate quantification of parasitic loads in T. gondii prenatal infections.
Collapse
|
32
|
Plasmodium falciparum parasites lacking histidine-rich protein 2 and 3: a review and recommendations for accurate reporting. Malar J 2014; 13:283. [PMID: 25052298 PMCID: PMC4115471 DOI: 10.1186/1475-2875-13-283] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 06/27/2014] [Indexed: 11/21/2022] Open
Abstract
Malaria rapid diagnostic tests (RDTs) play a critical role in malaria case management, surveillance and case investigations. Test performance is largely determined by design and quality characteristics, such as detection sensitivity, specificity, and thermal stability. However, parasite characteristics such as variable or absent expression of antigens targeted by RDTs can also affect RDT performance. Plasmodium falciparum parasites lacking the PfHRP2 protein, the most common target antigen for detection of P. falciparum, have been reported in some regions. Therefore, accurately mapping the presence and prevalence of P. falciparum parasites lacking pfhrp2 would be an important step so that RDTs targeting alternative antigens, or microscopy, can be preferentially selected for use in such regions. Herein the available evidence and molecular basis for identifying malaria parasites lacking PfHRP2 is reviewed, and a set of recommended procedures to apply for future investigations for parasites lacking PfHRP2, is proposed.
Collapse
|
33
|
External quality assurance of malaria nucleic acid testing for clinical trials and eradication surveillance. PLoS One 2014; 9:e97398. [PMID: 24838112 PMCID: PMC4023973 DOI: 10.1371/journal.pone.0097398] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/18/2014] [Indexed: 11/19/2022] Open
Abstract
Nucleic acid testing (NAT) for malaria parasites is an increasingly recommended diagnostic endpoint in clinical trials of vaccine and drug candidates and is also important in surveillance of malaria control and elimination efforts. A variety of reported NAT assays have been described, yet no formal external quality assurance (EQA) program provides validation for the assays in use. Here, we report results of an EQA exercise for malaria NAT assays. Among five centers conducting controlled human malaria infection trials, all centers achieved 100% specificity and demonstrated limits of detection consistent with each laboratory's pre-stated expectations. Quantitative bias of reported results compared to expected results was generally <0.5 log10 parasites/mL except for one laboratory where the EQA effort identified likely reasons for a general quantitative shift. The within-laboratory variation for all assays was low at <10% coefficient of variation across a range of parasite densities. Based on this study, we propose to create a Molecular Malaria Quality Assessment program that fulfills the need for EQA of malaria NAT assays worldwide.
Collapse
|
34
|
Kamau E, Alemayehu S, Feghali KC, Juma DW, Blackstone GM, Marion WR, Obare P, Ogutu B, Ockenhouse CF. Sample-ready multiplex qPCR assay for detection of malaria. Malar J 2014; 13:158. [PMID: 24767409 PMCID: PMC4026594 DOI: 10.1186/1475-2875-13-158] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 04/10/2014] [Indexed: 11/17/2022] Open
Abstract
Background Microscopy and antigen detecting rapid diagnostic tests are the diagnostic tests of choice in management of clinical malaria. However, due to their limitations, the need to utilize more sensitive methods such as real-time PCR (qPCR) is evident as more studies are now utilizing molecular methods in detection of malaria. Some of the challenges that continue to limit the widespread utilization of qPCR include lack of assay standardization, assay variability, risk of contamination, and the need for cold-chain. Lyophilization of molecular assays can overcome some of these limitations and potentially enable widespread qPCR utilization. Methods A recently published multiplex malaria qPCR assay was lyophilized by freezing drying into Sample-Ready™ format (MMSR). MMSR assay contained all the required reagents for qPCR including primers and probes, requiring only the addition of water and sample to perform qPCR. The performance of the MMSR assay was compared to the non-freeze dried, “wet” assay. Stability studies were done by maintaining the MMSR assays at four different ambient temperatures of 4°C, room temperature (RT), 37°C and 42°C over a period of 42 days, tested at seven-day intervals. Plasmodium falciparum and Plasmodium vivax DNAs were used for analysis of the MMSR assay either as single or mixed parasites, at two different concentrations. The CT values and the standard deviations (SD) were used in the analysis of the assay performance. Results The limit of detection for the MMSR assay was 0.244 parasites/μL for Plasmodium spp. (PLU) and P. falciparum (FAL) assay targets compared to “wet” assay which was 0.39 and 3.13 parasites/μL for PLU and FAL assay targets, respectively. The MMSR assay performed with high efficiencies similar to those of the “wet” assay and was stable at 37°C for 42 days, with estimated shelf-life of 5 months. When used to analyse field clinical samples, MMSR assay performed with 100% sensitivity and specificity compared to the “wet” assay. Conclusion The MMSR assay has the same robust performance characteristics as the “wet” assay and is highly stable. Availability of MMSR assay allows flexibility and provides an option in choosing assay for malaria diagnostics depending on the application, needs and budget.
Collapse
Affiliation(s)
- Edwin Kamau
- Walter Reed Army Institute of Research, Military Malaria Research Program, Malaria Vaccine Branch, 503 Robert Grant Ave, Silver Spring, Maryland, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
35
|
A quality control program within a clinical trial Consortium for PCR protocols to detect Plasmodium species. J Clin Microbiol 2014; 52:2144-9. [PMID: 24740073 DOI: 10.1128/jcm.00565-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Malaria parasite infections that are only detectable by molecular methods are highly prevalent and represent a potential transmission reservoir. The methods used to detect these infections are not standardized, and their operating characteristics are often unknown. We designed a proficiency panel of Plasmodium spp. in order to compare the accuracy of parasite detection of molecular protocols used by labs in a clinical trial consortium. Ten dried blood spots (DBSs) were assembled that contained P. falciparum, P. vivax, P. malariae, and P. ovale; DBSs contained either a single species or a species mixed with P. falciparum. DBS panels were tested in 9 participating laboratories in a masked fashion. Of 90 tests, 68 (75.6%) were correct; there were 20 false-negative results and 2 false positives. The detection rate was 77.8% (49/63) for P. falciparum, 91.7% (11/12) for P. vivax, 83.3% (10/12) for P. malariae, and 70% (7/10) for P. ovale. Most false-negative P. falciparum results were from samples with an estimated ≤ 5 parasites per μl of blood. Between labs, accuracy ranged from 100% to 50%. In one lab, the inability to detect species in mixed-species infections prompted a redesign and improvement of the assay. Most PCR-based protocols were able to detect P. falciparum and P. vivax at higher densities, but these assays may not reliably detect parasites in samples with low P. falciparum densities. Accordingly, formal quality assurance for PCR should be employed whenever this method is used for diagnosis or surveillance. Such efforts will be important if PCR is to be widely employed to assist malaria elimination efforts.
Collapse
|
36
|
Alemayehu S, Feghali KC, Cowden J, Komisar J, Ockenhouse CF, Kamau E. Comparative evaluation of published real-time PCR assays for the detection of malaria following MIQE guidelines. Malar J 2013; 12:277. [PMID: 23927553 PMCID: PMC3750446 DOI: 10.1186/1475-2875-12-277] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 08/02/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The use of malaria-specific quantitative real-time PCR (qPCR) is increasing due to its high sensitivity, speciation and quantification of malaria parasites. However, due to the lack of consensus or standardized methods in performing qPCR, it is difficult to evaluate and/or compare the quality of work reported by different authors for a cross-study and/or cross-platform assay analysis. METHODS The performances of seven published qPCR assays that detect Plasmodium spp or Plasmodium falciparum were compared using standard DNA and samples from a clinical trial. Amplification and qPCR measurements were performed using the Applied Biosystems 7500 Fast Real-Time PCR System. All the analyses were automatically established using the default settings. For the TaqMan probe format, the assays were performed in the background of QuantiFast Probe Master Mix whereas in SYBR Green format, the assays were performed in the background of QuantiFast SYBR Green Master Mix and QuantiTect SYBR Green Master Mix background. RESULTS Assays with high PCR efficiencies outperformed those with low efficiencies in all categories including sensitivity, precision and consistency regardless of the assay format and background. With the exception of one assay, all assays evaluated showed lower sensitivity compared to what have been published. When samples from a malaria challenge study were analysed, the qPCR assay with the overall best performance detected parasites in subjects earliest and with most consistency. CONCLUSION The data demonstrate the need for increased consensus and guidelines that will encourage better experimental practices, allowing more consistent and unambiguous interpretation of qPCR results.
Collapse
Affiliation(s)
- Saba Alemayehu
- Military Malaria Research Program, Malaria Vaccine Branch, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD, USA
| | | | | | | | | | | |
Collapse
|
37
|
Mosha JF, Sturrock HJW, Greenhouse B, Greenwood B, Sutherland CJ, Gadalla N, Atwal S, Drakeley C, Kibiki G, Bousema T, Chandramohan D, Gosling R. Epidemiology of subpatent Plasmodium falciparum infection: implications for detection of hotspots with imperfect diagnostics. Malar J 2013; 12:221. [PMID: 23815811 PMCID: PMC3701503 DOI: 10.1186/1475-2875-12-221] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 06/26/2013] [Indexed: 01/28/2023] Open
Abstract
Background At the local level, malaria transmission clusters in hotspots, which may be a group of households that experience higher than average exposure to infectious mosquitoes. Active case detection often relying on rapid diagnostic tests for mass screen and treat campaigns has been proposed as a method to detect and treat individuals in hotspots. Data from a cross-sectional survey conducted in north-western Tanzania were used to examine the spatial distribution of Plasmodium falciparum and the relationship between household exposure and parasite density. Methods Dried blood spots were collected from consenting individuals from four villages during a survey conducted in 2010. These were analysed by PCR for the presence of P. falciparum, with the parasite density of positive samples being estimated by quantitative PCR. Household exposure was estimated using the distance-weighted PCR prevalence of infection. Parasite density simulations were used to estimate the proportion of infections that would be treated using a screen and treat approach with rapid diagnostic tests (RDT) compared to targeted mass drug administration (tMDA) and Mass Drug Administration (MDA). Results Polymerase chain reaction PCR analysis revealed that of the 3,057 blood samples analysed, 1,078 were positive. Mean distance-weighted PCR prevalence per household was 34.5%. Parasite density was negatively associated with transmission intensity with the odds of an infection being subpatent increasing with household exposure (OR 1.09 per 1% increase in exposure). Parasite density was also related to age, being highest in children five to ten years old and lowest in those > 40 years. Simulations of different tMDA strategies showed that treating all individuals in households where RDT prevalence was above 20% increased the number of infections that would have been treated from 43 to 55%. However, even with this strategy, 45% of infections remained untreated. Conclusion The negative relationship between household exposure and parasite density suggests that DNA-based detection of parasites is needed to provide adequate sensitivity in hotspots. Targeting MDA only to households with RDT-positive individuals may allow a larger fraction of infections to be treated. These results suggest that community-wide MDA, instead of screen and treat strategies, may be needed to successfully treat the asymptomatic, subpatent parasite reservoir and reduce transmission in similar settings.
Collapse
Affiliation(s)
- Jacklin F Mosha
- National Institute for Medical Research, NIMR, Mwanza Medical Research Centre, Mwanza, Tanzania.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
El Chaar M, Atwal S, Freimanis GL, Dinko B, Sutherland CJ, Allain JP. Inactivation of Plasmodium falciparum in whole blood by riboflavin plus irradiation. Transfusion 2013; 53:3174-83. [PMID: 23656538 DOI: 10.1111/trf.12235] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 02/01/2013] [Accepted: 02/04/2013] [Indexed: 11/29/2022]
Abstract
BACKGROUND Malaria parasites are frequently transmitted by unscreened blood transfusions in Africa. Pathogen reduction methods in whole blood would thus greatly improve blood safety. We aimed to determine the efficacy of riboflavin plus irradiation for treatment of whole blood infected with Plasmodium falciparum. STUDY DESIGN AND METHODS Blood was inoculated with 10(4) or 10(5) parasites/mL and riboflavin treated with or without ultraviolet (UV) irradiation (40-160 J/mL red blood cells [mL(RBCs)]). Parasite genome integrity was assessed by quantitative amplification inhibition assays, and P. falciparum viability was monitored in vitro. RESULTS Riboflavin alone did not affect parasite genome integrity or parasite viability. Application of UV after riboflavin treatment disrupted parasite genome integrity, reducing polymerase-dependent amplification by up to 2 logs (99%). At 80 J/mL(RBCs), riboflavin plus irradiation prevented recovery of viable parasites in vitro for 2 weeks, whereas untreated controls typically recovered to approximately 2% parasitemia after 4 days of in vitro culture. Exposure of blood to 160 J/mL(RBCs) was not associated with significant hemolysis. CONCLUSIONS Riboflavin plus irradiation treatment of whole blood damages parasite genomes and drastically reduces P. falciparum viability in vitro. In the absence of suitable malaria screening assays, parasite inactivation should be investigated for prevention of transfusion-transmitted malaria in highly endemic areas.
Collapse
Affiliation(s)
- Mira El Chaar
- Department of Haematology, University of Cambridge, Cambridge, United Kingdom; Department of Immunology & Infection, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom; HPA Malaria Reference Laboratory, London School of Hygiene & Tropical Medicine, London, United Kingdom; Faculty of Health Sciences, University of Balamand, Beirut, Lebanon
| | | | | | | | | | | |
Collapse
|
39
|
Polley SD, González IJ, Mohamed D, Daly R, Bowers K, Watson J, Mewse E, Armstrong M, Gray C, Perkins MD, Bell D, Kanda H, Tomita N, Kubota Y, Mori Y, Chiodini PL, Sutherland CJ. Clinical evaluation of a loop-mediated amplification kit for diagnosis of imported malaria. J Infect Dis 2013; 208:637-44. [PMID: 23633403 PMCID: PMC3719897 DOI: 10.1093/infdis/jit183] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Background. Diagnosis of malaria relies on parasite detection by microscopy or antigen detection; both fail to detect low-density infections. New tests providing rapid, sensitive diagnosis with minimal need for training would enhance both malaria diagnosis and malaria control activities. We determined the diagnostic accuracy of a new loop-mediated amplification (LAMP) kit in febrile returned travelers. Methods. The kit was evaluated in sequential blood samples from returned travelers sent for pathogen testing to a specialist parasitology laboratory. Microscopy was performed, and then malaria LAMP was performed using Plasmodium genus and Plasmodium falciparum–specific tests in parallel. Nested polymerase chain reaction (PCR) was performed on all samples as the reference standard. Primary outcome measures for diagnostic accuracy were sensitivity and specificity of LAMP results, compared with those of nested PCR. Results. A total of 705 samples were tested in the primary analysis. Sensitivity and specificity were 98.4% and 98.1%, respectively, for the LAMP P. falciparum primers and 97.0% and 99.2%, respectively, for the Plasmodium genus primers. Post hoc repeat PCR analysis of all 15 tests with discrepant results resolved 4 results in favor of LAMP, suggesting that the primary analysis had underestimated diagnostic accuracy. Conclusions. Malaria LAMP had a diagnostic accuracy similar to that of nested PCR, with a greatly reduced time to result, and was superior to expert microscopy.
Collapse
Affiliation(s)
- Spencer D Polley
- Department of Clinical Parasitology, Walk-in Clinic, Hospital for Tropical Diseases, University London Colleges NHS Foundation Trust, Mortimer Market, London WC1E 6JB, UK
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Hopkins H, González IJ, Polley SD, Angutoko P, Ategeka J, Asiimwe C, Agaba B, Kyabayinze DJ, Sutherland CJ, Perkins MD, Bell D. Highly sensitive detection of malaria parasitemia in a malaria-endemic setting: performance of a new loop-mediated isothermal amplification kit in a remote clinic in Uganda. J Infect Dis 2013; 208:645-52. [PMID: 23633405 PMCID: PMC3719898 DOI: 10.1093/infdis/jit184] [Citation(s) in RCA: 212] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Current malaria diagnostic tests, including microscopy and antigen-detecting rapid tests, cannot reliably detect low-density infections. Molecular methods such as polymerase chain reaction (PCR) are highly sensitive but remain too complex for field deployment. A new commercial molecular assay based on loop-mediated isothermal amplification (LAMP) was assessed for field use. METHODS Malaria LAMP (Eiken Chemical, Japan) was evaluated for samples from 272 outpatients at a rural Ugandan clinic and compared with expert microscopy, nested PCR, and quantitative PCR (qPCR). Two technicians performed the assay after 3 days of training, using 2 alternative blood sample-preparation methods and visual interpretation of results by fluorescence assay. RESULTS Compared with 3-well nested PCR, the sensitivity of both LAMP and single-well nested PCR was 90%; the microscopy sensitivity was 51%. For samples with a Plasmodium falciparum qPCR titer of ≥ 2 parasites/µL, LAMP sensitivity was 97.8% (95% confidence interval, 93.7%-99.5%). Most false-negative LAMP results involved samples with parasitemia levels detectable by 3-well nested PCR but very low or undetectable by qPCR. CONCLUSIONS Malaria LAMP in a remote Ugandan clinic achieved sensitivity similar to that of single-well nested PCR in a United Kingdom reference laboratory. LAMP dramatically lowers the detection threshold achievable in malaria-endemic settings, providing a new tool for diagnosis, surveillance, and screening in elimination strategies.
Collapse
Affiliation(s)
- Heidi Hopkins
- Foundation for Innovative New Diagnostics, Uganda Ministry of Health, Kampala, Uganda
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Chew CH, Lim YAL, Lee PC, Mahmud R, Chua KH. Hexaplex PCR detection system for identification of five human Plasmodium species with an internal control. J Clin Microbiol 2012; 50:4012-9. [PMID: 23035191 PMCID: PMC3502955 DOI: 10.1128/jcm.06454-11] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 09/24/2012] [Indexed: 11/20/2022] Open
Abstract
Malaria remains one of the major killers of humankind and persists to threaten the lives of more than one-third of the world's population. Given that human malaria can now be caused by five species of Plasmodium, i.e., Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, and the recently included Plasmodium knowlesi, there is a critical need not only to augment global health efforts in malaria control but also, more importantly, to develop a rapid, accurate, species-sensitive/species-specific, and economically effective diagnostic method for malaria caused by these five species. Therefore, in the present study, a straightforward single-step hexaplex PCR system targeting five human Plasmodium 18S small-subunit rRNAs (ssu rRNAs) was designed, and the system successfully detected all five human malaria parasites. In addition, this system enables the differentiation of single infection as well as mixed infections up to the two-species level. This assay was validated with 50 randomly blinded test and 184 clinical samples suspected to indicate malaria. This hexaplex PCR system is not only an ideal alternative for routine malaria diagnosis in laboratories with conventional PCR machines but also adds value to diagnoses when there is a lack of an experienced microscopist or/and when the parasite morphology is confusing. Indeed, this system will definitely enhance the accuracy and accelerate the speed in the diagnosis of malaria, as well as improve the efficacy of malaria treatment and control, in addition to providing reliable data from epidemiological surveillance studies.
Collapse
Affiliation(s)
- Ching Hoong Chew
- Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Yvonne Ai Lian Lim
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Ping Chin Lee
- School of Science and Technology, Universiti Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia
| | - Rohela Mahmud
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Kek Heng Chua
- Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| |
Collapse
|
42
|
Polley SD, Sutherland CJ, Regan F, Hassan M, Chiodini PL. Increased sensitivity for detecting malaria parasites in human umbilical cord blood using scaled-up DNA preparation. Malar J 2012; 11:62. [PMID: 22390576 PMCID: PMC3325849 DOI: 10.1186/1475-2875-11-62] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Accepted: 03/05/2012] [Indexed: 11/26/2022] Open
Abstract
Background All mothers donating umbilical cord blood units to the NHS cord blood bank undergo an assessment for the likelihood of prior exposure to malaria infection. Those deemed at risk due to a history of travel to, or residence in, malaria endemic regions are screened serologically to detect anti-malaria antibodies. A positive result excludes the use of the cord blood for transplant therapy unless a risk assessment can ensure that malaria transmission is extremely unlikely. This paper details the screening of cord blood units from malaria serology positive mothers to detect malaria parasite DNA using a highly sensitive nested PCR. Methods Uninfected blood from a healthy volunteer was spiked with known quantities of malaria parasites and 5 millilitre and 200 microlitre aliquots were subjected to DNA extraction using QIAamp DNA maxi and DNA mini kits respectively. Nested PCR, to detect malarial SSU rRNA sequences, was performed on the purified DNA samples to determine the limit of detection for this assay with both extraction methodologies. Following assay validation, 54 cord blood units donated by mothers who were positive for anti-malaria antibodies were screened by this approach. Results When DNA was purified from 5 millilitres of blood it was possible to routinely detect as few as 50 malaria parasites per millilitre using nested PCR. This equates to a significant increase in the sensitivity of the current gold standard nucleic acid amplification technique used to detect malaria parasites (routinely performed from > 200 microlitre volumes of blood). None of the 54 donated cord blood units from serology positive mothers tested positive for malaria parasites using this scaled up DNA preparation method. Conclusion Serological testing for malaria parasites may be overly conservative, leading to unnecessary rejection of cord blood donations that lack malaria parasites and which are, therefore, safe for use in stem cell therapy.
Collapse
Affiliation(s)
- Spencer D Polley
- Department of Clinical Parasitology, Hospital for Tropical Diseases, University College London Hospitals NHS Foundation Trust, London, UK.
| | | | | | | | | |
Collapse
|
43
|
Hwang SY, Kim SH, Lee GY, Hang VTT, Moon CS, Shin JH, Koo WL, Kim SY, Park HJ, Park HO, Kho WG. A novel real-time PCR assay for the detection of Plasmodium falciparum and Plasmodium vivax malaria in low parasitized individuals. Acta Trop 2011; 120:40-5. [PMID: 21664340 DOI: 10.1016/j.actatropica.2011.05.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 04/13/2011] [Accepted: 05/16/2011] [Indexed: 11/18/2022]
Abstract
The rapid, accurate diagnosis of Plasmodium spp. is essential for the effective control of malaria, especially in asymptomatic infections. In this study, we developed a sensitive, genus-specific, real-time quantitative PCR assay. It was compared with the microscopic examination of Giemsa-stained blood smears and two different molecular diagnostic techniques: nested PCR and multiplex PCR. For the effective quantitative detection of malaria parasites, all reagents were designed with a lyophilized format in one tube. Plasmodium was detected successfully in all 112 clinically suspected malaria patients, including 32 individuals with low parasitemia (1-100 parasites/μl). The sensitivity threshold was 0.2 parasites/μl and no PCR-positive reaction occurred when malaria parasites were not present. This may be a useful method for detecting malaria parasites in endemic areas.
Collapse
Affiliation(s)
- Seung-Young Hwang
- Department of Parasitology, Inje University College of Medicine, Busan 614-735, South Korea
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Abstract
Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal.
Collapse
|
45
|
Waitumbi JN, Gerlach J, Afonina I, Anyona SB, Koros JN, Siangla J, Ankoudinova I, Singhal M, Watts K, Polhemus ME, Vermeulen NM, Mahoney W, Steele M, Domingo GJ. Malaria prevalence defined by microscopy, antigen detection, DNA amplification and total nucleic acid amplification in a malaria-endemic region during the peak malaria transmission season. Trop Med Int Health 2011; 16:786-93. [PMID: 21447064 DOI: 10.1111/j.1365-3156.2011.02773.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To determine the malaria prevalence by microscopy, antigen detection and nucleic acid detection in a defined subpopulation in a Plasmodium falciparum-endemic region during the peak transmission season. METHODS Blood specimens were collected in a cross-sectional study involving children aged 5-10 years (n = 195) presenting with acute fever to two clinics in Western Kenya. All specimens underwent microscopy, HRP2 and aldolase antigen detection by enzyme immunoassay (EIA), parasite-specific DNA and total nucleic acid (RNA and DNA) by real-time PCR (qPCR) and reverse-transcriptase PCR (qRT-PCR). RESULTS Microscopy detected 65/195 cases of malaria infection [95% confidence interval (CI) 52-78]. HRP2 and aldolase EIA had similar sensitivity levels detecting antigen in 65/195 (95% CI, 52-78) and 57/195 (95% CI, 45-70) cases. Discordants in antigen detection vs. microscopy occurred at <470 parasites/μl and <4900 parasites/μl for HRP2 and aldolase, respectively. Detection of total nucleic acid allowed a 3 log lower limit of detection than just DNA detection by real-time PCR in vitro. In clinical specimens, 114/195 (95% CI, 100-127) were qPCR positive (DNA), and 187/195 (95% CI, 179-191) were qRT-PCR positive (DNA plus RNA). CONCLUSIONS The prevalence of submicroscopic malaria infection was significantly higher when detecting total nucleic acid than just DNA in this outpatient population during the high transmission season. Defining standards for submicroscopic infection will be important for control programmes, diagnostics development efforts and molecular epidemiology studies.
Collapse
Affiliation(s)
- John N Waitumbi
- Walter Reed Project, Kenya Medical Research Institute, Kisumu, Kenya
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Beshir KB, Hallett RL, Eziefula AC, Bailey R, Watson J, Wright SG, Chiodini PL, Polley SD, Sutherland CJ. Measuring the efficacy of anti-malarial drugs in vivo: quantitative PCR measurement of parasite clearance. Malar J 2010; 9:312. [PMID: 21054863 PMCID: PMC2992070 DOI: 10.1186/1475-2875-9-312] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 11/05/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Artemisinin-based combination therapy, currently considered the therapy of choice for uncomplicated Plasmodium falciparum malaria in endemic countries, may be under threat from newly emerging parasite resistance to the artemisinin family of drugs. Studies in Southeast Asia suggest some patients exhibit an extended parasite clearance time in the three days immediately following treatment with artesunate monotherapy. This phenotype is likely to become a more important trial endpoint in studies of anti-malarial drug efficacy, but currently requires frequent, closely spaced blood sampling in hospitalized study participants, followed by quantitation of parasite density by microscopy. METHODS A simple duplex quantitative PCR method was developed in which distinct fluorescent signals are generated from the human and parasite DNA components in each blood sample. The human amplification target in this assay is the β tubulin gene, and the parasite target is the unique methionine tRNA gene (pgmet), which exhibits perfect sequence identity in all six Plasmodium species that naturally infect humans. In a small series of malaria cases treated as hospital in-patients, the abundance of pgmet DNA was estimated relative to the human DNA target in daily peripheral blood samples, and parasite clearance times calculated. RESULTS The qPCR assay was reproducibly able to replicate parasite density estimates derived from microscopy, but provided additional data by quantification of parasite density 24 hours after the last positive blood film. Robust estimates of parasite clearance times were produced for a series of patients with clinical malaria. CONCLUSIONS Large studies, particularly in Africa where children represent a major proportion of treated cases, will require a simpler blood sample collection regime, and a method capable of high throughput. The duplex qPCR method tested may fulfil these criteria, and should now be evaluated in such field studies.
Collapse
Affiliation(s)
- Khalid B Beshir
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine (LSHTM), Keppel St, London, WC1E 7HT, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Mitochondrial DNA targets increase sensitivity of malaria detection using loop-mediated isothermal amplification. J Clin Microbiol 2010; 48:2866-71. [PMID: 20554824 DOI: 10.1128/jcm.00355-10] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Loop-mediated isothermal amplification (LAMP) of DNA offers the ability to detect very small quantities of pathogen DNA following minimal tissue sample processing and is thus an attractive methodology for point-of-care diagnostics. Previous attempts to diagnose malaria by the use of blood samples and LAMP have targeted the parasite small-subunit rRNA gene, with a resultant sensitivity for Plasmodium falciparum of around 100 parasites per microl. Here we describe the use of mitochondrial targets for LAMP-based detection of any Plasmodium genus parasite and of P. falciparum specifically. These new targets allow routine amplification from samples containing as few as five parasites per microl of blood. Amplification is complete within 30 to 40 min and is assessed by real-time turbidimetry, thereby offering rapid diagnosis with greater sensitivity than is achieved by the most skilled microscopist or antigen detection using lateral flow immunoassays.
Collapse
|
48
|
Collier S, Manser M, Chiodini PL. External quality assessment scheme for parasite serology; a review of the scheme design and performance. J Clin Pathol 2010; 63:441-4. [DOI: 10.1136/jcp.2009.071597] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BackgroundAn external quality assessment (EQA) scheme for parasite serology was introduced in April 2005 as a tool to measure how well laboratories were performing in parasite serodiagnosis.Aim and MethodsTo review the scheme design and performance from its beginning until January 2008.ResultsThe numbers of participating laboratories gradually increased during the review period and was 28 in January 2008. The results showed that the standard of reporting was extremely high and there was an encouraging trend towards improvement in the overall percentage of correct reports. The most common error made was the returning of false negative results for Strongyloides antibodies.ConclusionIt is hoped that this scheme will lead to a more standardised approach to the serological diagnosis of parasitic infection.
Collapse
|
49
|
Gadalla NB, Elzaki SE, Mukhtar E, Warhurst DC, El-Sayed B, Sutherland CJ. Dynamics of pfcrt alleles CVMNK and CVIET in chloroquine-treated Sudanese patients infected with Plasmodium falciparum. Malar J 2010; 9:74. [PMID: 20226032 PMCID: PMC2848148 DOI: 10.1186/1475-2875-9-74] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Accepted: 03/12/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Parasite resistance to the anti-malarial drug chloroquine is common in eastern Sudan. Dynamic within-host changes in the relative abundance of both sensitive and resistant Plasmodium falciparum parasites were examined in a cohort of chloroquine-treated patients presenting with uncomplicated falciparum malaria, using a novel allele-specific quantitative approach. METHODS Treatment outcomes were determined for 93 patients of all ages in a per protocol cohort using a modified 14-day WHO protocol. Parasite DNA samples at days 0, 1, 2, 3, 7 and 14 following treatment were analysed using real-time quantitative PCR methods that distinguished resistant and sensitive genotypes at amino acids 72-76 of the pfcrt locus. RESULTS Chloroquine treatment was not efficacious, and of 93 assessable patients, only 10 individuals (10.7%; 95% C.I. 4.34-17.2%) enjoyed an adequate clinical and parasitological response. Resistant parasites with the haplotype CVIET at codons 72-76 of the pfcrt locus were dominant in the starting population. Chloroquine sensitive parasites with the haplotype CVMNK were detected in 19 individuals prior to treatment (20.43%; 95% C.I. 5.14-18.5%). In these patients, CQ treatment rapidly selected CVIET parasites, and this haplotype overwhelmingly dominated the parasite population in each individual by day 2 after treatment. CONCLUSIONS Such rapid intra-host selection of particular genotypes after the introduction of drug will cause frequent misidentification of parasite genotypes present in the starting population. This will have a potentially serious confounding effect on clinical trials which employ PCR-corrected estimates of treatment failure, as resistant parasites below the detection threshold in the pre-treatment sample can be erroneously classified as "new" infections during follow-up, over-estimating drug efficacy.
Collapse
Affiliation(s)
- Nahla B Gadalla
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK
| | | | | | | | | | | |
Collapse
|
50
|
Madej RM, Davis J, Holden MJ, Kwang S, Labourier E, Schneider GJ. International standards and reference materials for quantitative molecular infectious disease testing. J Mol Diagn 2010; 12:133-43. [PMID: 20075208 DOI: 10.2353/jmoldx.2010.090067] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The utility of quantitative molecular diagnostics for patient management depends on the ability to relate patient results to prior results or to absolute values in clinical practice guidelines. To do this, those results need to be comparable across time and methods, either by producing the same value across methods and test versions or by using reliable and stable conversions. Universally available standards and reference materials specific to quantitative molecular technologies are critical to this process but are few in number. This review describes recent history in the establishment of international standards for nucleic acid test development, organizations involved in current efforts, and future issues and initiatives.
Collapse
|