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Tapaopong P, Chainarin S, Mala A, Rannarong A, Kangkasikorn N, Kusolsuk T, Roobsoong W, Cui L, Nguitragool W, Sattabongkot J, Bantuchai S. Declining Genetic Polymorphisms of the C-terminus Merozoite Surface Protein-1 Amidst Increased Plasmodium knowlesi Transmission in Thailand. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.27.600943. [PMID: 38979329 PMCID: PMC11230454 DOI: 10.1101/2024.06.27.600943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Recent reports from Thailand reveal a substantial surge in Plasmodium knowlesi cases over the past decade, with a more than eightfold increase in incidence by 2023 compared to 2018. This study investigates temporal changes in genetic polymorphism associated with the escalating transmission of P. knowlesi malaria in Thailand over the past two decades. Twenty-five P. knowlesi samples collected in 2018-2023 were sequenced for the 42-kDa region of pkmsp1 and compared with 24 samples collected in 2000-2009, focusing on nucleotide diversity, natural selection, recombination rate, and population differentiation. Seven unique haplotypes were identified in recent samples, compared to 15 in earlier samples. Nucleotide and haplotype diversities were lower in recent samples (π = 0.016, Hd = 0.817) than in earlier samples (π = 0.018, Hd = 0.942). Significantly higher synonymous substitution rates were observed in both sample sets (dS - dN = 2.77 and 2.43, p < 0.05), indicating purifying selection and reduced genetic diversity over time. Additionally, 8 out of 17 mutation points were located on B-cell epitopes, suggesting an adaptive response by the parasites to evade immune recognition. Population differentiation analysis using the fixation index (Fst) revealed high genetic differentiation between parasite populations in central and southern Thailand or Malaysia. Conversely, the relatively lower Fst value between southern Thailand and Malaysia suggests a closer genetic relationship, possibly reflecting historical gene flow. In conclusion, our findings highlight a decline in genetic diversity and evidence of purifying selection associated with the recently increased incidence of P. knowlesi malaria in Thailand. The minor genetic differentiation between P. knowlesi populations from southern Thailand and Malaysia suggests a shared recent ancestry of these parasites and underscores the need for coordinated efforts between the two countries for the elimination of P. knowlesi.
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Affiliation(s)
- Parsakorn Tapaopong
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Sittinont Chainarin
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | | | | | | - Teera Kusolsuk
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Wanlapa Roobsoong
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Liwang Cui
- Division of Infectious Diseases and International Medicine, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Wang Nguitragool
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Sirasate Bantuchai
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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Plasmodium knowlesi Duffy binding protein alpha region II (PkDBPαII) in clinical isolates from Peninsular Malaysia and Malaysian Borneo exhibit different immune responses in animal models. Parasitol Res 2022; 121:3443-3454. [PMID: 36152079 DOI: 10.1007/s00436-022-07665-7] [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: 03/09/2022] [Accepted: 09/09/2022] [Indexed: 10/14/2022]
Abstract
Plasmodium knowlesi utilizes the Duffy binding protein alpha (PkDBPα) to facilitate its invasion into human erythrocytes. PkDBPα region II (PkDBPαII) from Peninsular Malaysia and Malaysian Borneo has been shown to occur as distinct haplotypes, and the predominant haplotypes from these geographical areas demonstrated differences in binding activity to human erythrocytes in erythrocyte binding assays. This study aimed to determine the effects of genetic polymorphisms in PkDBPαII to immune responses in animal models. The recombinant PkDBPαII (~ 45 kDa) of Peninsular Malaysia (PkDBPαII-H) and Malaysian Borneo (PkDBPαII-S) were expressed in a bacterial expression system, purified, and used in mice and rabbit immunization. The profile of cytokines IL-1ra, IL-2, IL-6, IL-10, TNF-α, and IFN-γ in immunized mice spleen was determined via ELISA. The titer and IgG subtype distribution of raised antibodies was characterized. Immunized rabbit sera were purified and used to perform an in vitro merozoite invasion inhibition assay. The PkDBPαII-immunized mice sera of both groups showed high antibody titer and a similar IgG subtype distribution pattern: IgG2b > IgG1 > IgG2a > IgG3. The PkDBPαII-H group was shown to have higher IL-1ra (P = 0.141) and IL-6 (P = 0.049) concentrations, with IL-6 levels significantly higher than that of the PkDBPαII-S group (P ≤ 0.05). Merozoite invasion inhibition assay using purified anti-PkDBPαII antibodies showed a significantly higher inhibition rate in the PkDBPαII-H group than the PkDBPαII-S group (P ≤ 0.05). Besides, anti-PkDBPαII-H antibodies were able to exhibit inhibition activity at a lower concentration than anti-PkDBPαII-S antibodies. PkDBPαII was shown to be immunogenic, and the PkDBPαII haplotype from Peninsular Malaysia exhibited higher responses in cytokines IL-1ra and IL-6, antibody IgM level, and merozoite invasion inhibition assay than the Malaysian Borneo haplotype. This suggests that polymorphisms in the PkDBPαII affect the level of immune responses in the host.
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Grigg MJ, Lubis IN, Tetteh KKA, Barber BE, William T, Rajahram GS, Tan AF, Sutherland CJ, Noviyanti R, Drakeley CJ, Britton S, Anstey NM. Plasmodium knowlesi detection methods for human infections-Diagnosis and surveillance. ADVANCES IN PARASITOLOGY 2021; 113:77-130. [PMID: 34620386 DOI: 10.1016/bs.apar.2021.08.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Within the overlapping geographical ranges of P. knowlesi monkey hosts and vectors in Southeast Asia, an estimated 1.5 billion people are considered at risk of infection. P. knowlesi can cause severe disease and death, the latter associated with delayed treatment occurring from misdiagnosis. Although microscopy is a sufficiently sensitive first-line tool for P. knowlesi detection for most low-level symptomatic infections, misdiagnosis as other Plasmodium species is common, and the majority of asymptomatic infections remain undetected. Current point-of-care rapid diagnostic tests demonstrate insufficient sensitivity and poor specificity for differentiating P. knowlesi from other Plasmodium species. Molecular tools including nested, real-time, and single-step PCR, and loop-mediated isothermal amplification (LAMP), are sensitive for P. knowlesi detection. However, higher cost and inability to provide the timely point-of-care diagnosis needed to guide appropriate clinical management has limited their routine use in most endemic clinical settings. P. knowlesi is likely underdiagnosed across the region, and improved diagnostic and surveillance tools are required. Reference laboratory molecular testing of malaria cases for both zoonotic and non-zoonotic Plasmodium species needs to be more widely implemented by National Malaria Control Programs across Southeast Asia to accurately identify the burden of zoonotic malaria and more precisely monitor the success of human-only malaria elimination programs. The implementation of specific serological tools for P. knowlesi would assist in determining the prevalence and distribution of asymptomatic and submicroscopic infections, the absence of transmission in certain areas, and associations with underlying land use change for future spatially targeted interventions.
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Affiliation(s)
- Matthew J Grigg
- Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia; Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia.
| | - Inke N Lubis
- Faculty of Medicine, Universitas Sumatera Utara, Medan, Sumatera Utara, Indonesia
| | - Kevin K A Tetteh
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Bridget E Barber
- Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia; Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia; QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Timothy William
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia; Clinical Research Centre, Queen Elizabeth Hospital 1, Kota Kinabalu, Malaysia; Gleneagles Medical Centre, Kota Kinabalu, Malaysia
| | - Giri S Rajahram
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia; Clinical Research Centre, Queen Elizabeth Hospital 1, Kota Kinabalu, Malaysia; Queen Elizabeth Hospital 2, Kota Kinabalu, Malaysia
| | - Angelica F Tan
- Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia; Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
| | - Colin J Sutherland
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | - Chris J Drakeley
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Sumudu Britton
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Nicholas M Anstey
- Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia; Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
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Yap NJ, Vythilingam I, Hoh BP, Goh XT, Muslim A, Ngui R, Rajoo Y, Choy SH, William T, Yeo TW, Lim YAL. Genetic polymorphism and natural selection in the C-terminal 42 kDa region of merozoite surface protein-1 (MSP-1) among Plasmodium knowlesi samples from Malaysia. Parasit Vectors 2018; 11:626. [PMID: 30518419 PMCID: PMC6282282 DOI: 10.1186/s13071-018-3234-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/26/2018] [Indexed: 12/19/2022] Open
Abstract
Background The merozoite surface protein-1 (MSP-1) gene encodes for a leading malaria vaccine candidate antigen. However, its extensive polymorphic nature represents a major obstacle to the development of a protective vaccine. Previously, a pilot study was carried out to explore the sequence variation of the C-terminal 42 kDa fragment within P. knowlesi MSP-1 gene (PkMSP-142) based on 12 clinical samples; however, further study on an adequate sample size is vital in estimating the genetic diversity of the parasite population. Methods In the present study, we included a larger sample size of P. knowlesi (83 samples) covering eight states of Malaysia to determine the genetic polymorphism, natural selection and haplotype groups of the gene fragment coding PkMSP-142. The region flanking PkMSP-142 was amplified by PCR and directly sequenced. Genetic diversity, haplotype diversity, population genetic differentiation and natural selection were determined in order to study the polymorphic characteristic of PkMSP-142. Results A high level of genetic diversity (Hd = 0.970 ± 0.007; л = 0.01079 ± 0.00033) was observed among the 83 P. knowlesi samples, confirming the extensive genetic polymorphism exhibited among the P. knowlesi population found in Malaysia. A total of 18 distinct haplotypes with 17 amino acid changes were identified, whereby 15 were new haplotypes. High population differentiation values were observed within samples from Peninsular Malaysia and Malaysian Borneo. The 42 kDa fragments of P. knowlesi from Malaysian Borneo were found to be acting on balancing selection whilst purifying selection was suggested to act on isolates from Peninsular Malaysia. The separation of PkMSP-142 haplotypes into two main groups based on geographical separation has further supported the existence of two distinct P. knowlesi lineages. Conclusions A high level of genetic diversity was observed among PkMSP-142 in Malaysia, whereby most of the polymorphisms were found within the 33 kDa region. Taken together, these data will be useful in order to understand the nature of P. knowlesi population in Malaysia as well as the design and development of a MSP-142 based knowlesi malaria vaccine. Electronic supplementary material The online version of this article (10.1186/s13071-018-3234-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Nan Jiun Yap
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Indra Vythilingam
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Boon Peng Hoh
- Faculty of Medicine & Health Sciences, UCSI University Kuala Lumpur Campus, Cheras, Kuala Lumpur, Malaysia
| | - Xiang Ting Goh
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Azdayanti Muslim
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.,Department of Medical Microbiology and Parasitology, Faculty of Medicine, Universiti Teknologi MARA (Sungai Buloh Campus), Sungai Buloh, Selangor, Malaysia
| | - Romano Ngui
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Yamuna Rajoo
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.,International Medical University, Bukit Jalil, Kuala Lumpur, Malaysia
| | - Seow Huey Choy
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Timothy William
- Jesselton Medical Centre, 88300, Kota Kinabalu, Sabah, Malaysia
| | - Tsin Wen Yeo
- Communicable Diseases Centre, Institute of Infectious Disease and Epidemiology, Tan Tock Seng Hospital, Moulmein Road, Singapore, 308433, Singapore.,Lee Kong Chian School of Medicine, Nanyang Technological University, 11 Mandalay Road, Singapore, 308232, Singapore
| | - Yvonne Ai-Lian Lim
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. .,Centre of Excellence for Research in AIDS (CERiA), University of Malaya, 50603, Kuala Lumpur, Malaysia.
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Ahmed MA, Chu KB, Vythilingam I, Quan FS. Within-population genetic diversity and population structure of Plasmodium knowlesi merozoite surface protein 1 gene from geographically distinct regions of Malaysia and Thailand. Malar J 2018; 17:442. [PMID: 30497496 PMCID: PMC6267868 DOI: 10.1186/s12936-018-2583-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 11/21/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The C-terminal 42 kDa domain of Plasmodium knowlesi merozoite surface protein 1 (PkMSP1) is a potential asexual blood-stage vaccine candidate, however, only a limited number of clinical isolates have been analysed from Malaysia and no inter-country comparative diversity study has been conducted. In the present study, nucleotide diversity, haplotypes and natural selection levels of pkmsp1 in clinical samples from geographically distinct regions of Malaysia and Thailand were investigated. The overall population structure of the parasite from the region was determined. METHODS Eleven full-length pkmsp1 sequences obtained from clinical isolates of Malaysia along with the H-strain were downloaded from the database for domain wise characterization of pkmsp1 gene. Additionally, 76 pkmsp-142 sequences from Thailand and Malaysia were downloaded from the database for intra and inter-population analysis. DnaSP 5.10 and MEGA 5.0 software were used to determine genetic diversity, polymorphism, haplotypes and natural selection. Genealogical relationships were determined using haplotype network tree in NETWORK software v5.0. Population genetic differentiation index (FST) of parasites were analysed using Arlequin v3.5. RESULTS Sequence analysis of 11 full-length pkmsp1 sequences along with the H-strain identified 477 (8.4%) polymorphic sites, of which 107 were singleton sites. The overall diversity observed in the full-length genes were high in comparison to its ortholog pvmsp1 and the 4 variable domains showed extensive size variations. The nucleotide diversity was low towards the pkmsp1-42 compared to the conserved domains. The 19 kDa domain was less diverse and completely conserved among isolates from Malaysian Borneo. The nucleotide diversity of isolates from Peninsular Malaysia and Thailand were higher than Malaysian Borneo. Network analysis of pkmsp1-42 haplotypes showed geographical clustering of the isolates from Malaysian Borneo and grouping of isolates from Peninsular Malaysia and Thailand. Population differentiation analysis indicated high FST values between parasite populations originating from Malaysian Borneo, Peninsular Malaysia and Thailand attributing to geographical distance. Moderate genetic differentiation was observed for parasite populations from Thailand and Peninsular Malaysia. Evidence of population expansion and purifying selection were observed in all conserved domains with strongest selection within the pkmsp1-42 domain. CONCLUSIONS This study is the first to report on inter country genetic diversity and population structure of P. knowlesi based on msp1. Strong evidence of negative selection was observed in the 42 kDa domain, indicating functional constrains. Geographical clustering of P. knowlesi and moderate to high genetic differentiation values between populations identified in this study highlights the importance of further evaluation using larger number of clinical samples from Southeast Asian countries.
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Affiliation(s)
- Md Atique Ahmed
- Department of Medical Zoology, School of Medicine, Kyung Hee University, Seoul, 02447, Republic of Korea
| | - Ki-Back Chu
- Department of Biomedical Science, Graduate School, Kyung Hee University, Seoul, 02447, Republic of Korea
| | - Indra Vythilingam
- Parasitology Department, University of Malaya, Kuala Lumpur, Malaysia
| | - Fu-Shi Quan
- Department of Medical Zoology, School of Medicine, Kyung Hee University, Seoul, 02447, Republic of Korea. .,Biomedical Science Institute, Kyung Hee University, Seoul, 02447, Republic of Korea.
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Tengku-Idris TIN, Fong MY, Lau YL. Seroprevalence of sarcocystosis in the local communities of Pangkor and Tioman Islands using recombinant surface antigens 3 (rSAG3) of Sarcocystis falcatula. Trop Med Int Health 2018; 23:1374-1383. [PMID: 30286271 DOI: 10.1111/tmi.13160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To investigate the seroprevalence of Sarcocystosis in the local communities of Pangkor and Tioman islands, Malaysia, by using antigenic recombinant surface antigens 2 and 3 from Sarcocystis falcatula (rSfSAG2 and rSfSAG3) as the target proteins via Western blot and ELISA assays. METHODS SfSAG2 and SfSAG3 genes were isolated from S. falcatula and expressed in Escherichia coli expression system. A total of 348 serum samples [volunteers from both islands (n = 100), non-Sarcocystis parasitic infections patients (n = 50) and healthy donors (n = 100)] were collected and tested with purified SfSAGs in Western blot and ELISA assays to measure the seroprevalence of human sarcocystosis. RESULTS None of the sera in this study reacted with rSfSAG2 by Western blot and ELISA. For rSfSAG3, relatively high prevalence of sarcocystosis was observed in Tioman Island (75.5%) than in Pangkor Island (34%) by Western blot. In ELISA, the different prevalence rate was observed between Tioman Island (43.8%) and Pangkor Island (37%). The prevalence rate in other parasitic infections (amoebiasis, cysticercosis, filariasis, malaria, toxocariasis and toxoplasmosis) was 30% by Western blot and 26% by ELISA. Only 8% (by Western blot) and 10% (by ELISA) of healthy donors showed reactivity towards rSfSAG3. CONCLUSION This is the first study reporting a seroprevalence of sarcocystosis in Pangkor and Tioman Islands, Malaysia. The combination of Western blot and ELISA is suitable to be used for serodiagnosis of sarcocystosis. With further evaluations, SfSAG3 can potentially be used to confirm infection, asymptomatic screening, surveillance and epidemiological studies.
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Affiliation(s)
| | - Mun Yik Fong
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Yee Ling Lau
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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Domingos J, Casimiro A, Portugal-Calisto D, Varandas L, Nogueira F, Silva MS. Clinical, laboratorial and immunological aspects of severe malaria in children from Guinea-Bissau. Acta Trop 2018; 185:46-51. [PMID: 29684356 DOI: 10.1016/j.actatropica.2018.04.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 04/17/2018] [Accepted: 04/17/2018] [Indexed: 11/15/2022]
Abstract
Malaria is a parasitic disease of which Plasmodium falciparum causes the most severe form of the disease. The immune response against Plasmodium spp. is complex and remains unclear. The present report aimed to better understand the humoral immune response in severe malaria and analyse new immunodominant antigen candidates as possible serological marker in severe malaria in children. This study included children aged 0-16 years from Guinea-Bissau with clinical signs of severe malaria. Serological and immunochemical characterisation of different anti-P. falciparum antibodies were made by ELISA and immunoblotting using a crude protein extract of P. falciparum. Sera from 12 children with severe malaria were analysed. Nine samples were positive for total anti-P. falciparum antibodies, seven for IgM and eight for total IgG anti-P. falciparum. There was a predominance of IgG1 response, suggesting a cytophilic action in severe malaria and a major role of IgG1 over other immunoglobulins. The antigenic profile of P. falciparum showed a consistent immunoblotting pattern of approximately 180 kDa, 100 kDa and around 50-40 kDa. The serological reactivity found in protein bands makes them as immunodominant antigens and promising candidates for serological markers in the context of severe malaria.
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Affiliation(s)
- Janine Domingos
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Portugal
| | - Anaxore Casimiro
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Portugal
| | - Daniela Portugal-Calisto
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Portugal; Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Luís Varandas
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Portugal; Infectious Disease Unit, Hospital Dona Estefânia. Lisbon, Portugal
| | - Fátima Nogueira
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Portugal
| | - Marcelo Sousa Silva
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Portugal; Imunoparasitology Laboratory, Department of Clinical and Toxicological Analysis, Health Sciences Centre, Federal University of Rio Grande do Norte, Natal, Brazil; Programa de Pós-graduação em Bioquímica, Universidade Federal do Rio Grande do Norte, Natal, Brazil; Programa de Pós-graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Norte, Natal, Brazil.
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Herman LS, Fornace K, Phelan J, Grigg MJ, Anstey NM, William T, Moon RW, Blackman MJ, Drakeley CJ, Tetteh KKA. Identification and validation of a novel panel of Plasmodium knowlesi biomarkers of serological exposure. PLoS Negl Trop Dis 2018; 12:e0006457. [PMID: 29902183 PMCID: PMC6001954 DOI: 10.1371/journal.pntd.0006457] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 04/17/2018] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Plasmodium knowlesi is the most common cause of malaria in Malaysian Borneo, with reporting limited to clinical cases presenting to health facilities and scarce data on the true extent of transmission. Serological estimations of transmission have been used with other malaria species to garner information about epidemiological patterns. However, there are a distinct lack of suitable serosurveillance tools for this neglected disease. METHODOLOGY/PRINCIPAL FINDINGS Using in silico tools, we designed and expressed four novel P. knowlesi protein products to address the distinct lack of suitable serosurveillance tools: PkSERA3 antigens 1 and 2, PkSSP2/TRAP and PkTSERA2 antigen 1. Antibody prevalence to these antigens was determined by ELISA for three time-points post-treatment from a hospital-based clinical treatment trial in Sabah, East Malaysia (n = 97 individuals; 241 total samples for all time points). Higher responses were observed for the PkSERA3 antigen 2 (67%, 65/97) across all time-points (day 0: 36.9% 34/92; day 7: 63.8% 46/72; day 28: 58.4% 45/77) with significant differences between the clinical cases and controls (n = 55, mean plus 3 SD) (day 0 p<0.0001; day 7 p<0.0001; day 28 p<0.0001). Using boosted regression trees, we developed models to classify P. knowlesi exposure (cross-validated AUC 88.9%; IQR 86.1-91.3%) and identified the most predictive antibody responses. CONCLUSIONS/SIGNIFICANCE The PkSERA3 antigen 2 had the highest relative variable importance in all models. Further validation of these antigens is underway to determine the specificity of these tools in the context of multi-species infections at the population level.
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Affiliation(s)
- Lou S. Herman
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Kimberly Fornace
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jody Phelan
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Matthew J. Grigg
- Menzies School of Health Research and Charles Darwin University, Darwin, Northern Territory, Australia
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
| | - Nicholas M. Anstey
- Menzies School of Health Research and Charles Darwin University, Darwin, Northern Territory, Australia
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
| | - Timothy William
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
- Clinical Research Centre, Queen Elizabeth Hospital, Kota Kinabalu, Sabah, Malaysia
- Jesselton Medical Centre, Kota Kinabalu, Sabah, Malaysia
| | - Robert W. Moon
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Michael J. Blackman
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Chris J. Drakeley
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Kevin K. A. Tetteh
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Yap NJ, Goh XT, Koehler AV, William T, Yeo TW, Vythilingam I, Gasser RB, Lim YAL. Genetic diversity in the C-terminus of merozoite surface protein 1 among Plasmodium knowlesi isolates from Selangor and Sabah Borneo, Malaysia. INFECTION GENETICS AND EVOLUTION 2017. [PMID: 28634105 DOI: 10.1016/j.meegid.2017.06.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Plasmodium knowlesi, a malaria parasite of macaques, has emerged as an important parasite of humans. Despite the significance of P. knowlesi malaria in parts of Southeast Asia, very little is known about the genetic variation in this parasite. Our aim here was to explore sequence variation in a molecule called the 42kDa merozoite surface protein-1 (MSP-1), which is found on the surface of blood stages of Plasmodium spp. and plays a key role in erythrocyte invasion. Several studies of P. falciparum have reported that the C-terminus (a 42kDa fragment) of merozoite surface protein-1 (MSP-142; consisting of MSP-119 and MSP-133) is a potential candidate for a malaria vaccine. However, to date, no study has yet investigated the sequence diversity of the gene encoding P. knowlesi MSP-142 (comprising Pk-msp-119 and Pk-msp-133) among isolates in Malaysia. The present study explored this aspect. Twelve P. knowlesi isolates were collected from patients from hospitals in Selangor and Sabah Borneo, Malaysia, between 2012 and 2014. The Pk-msp-142 gene was amplified by PCR and directly sequenced. Haplotype diversity (Hd) and nucleotide diversity (л) were studied among the isolates. There was relatively high genetic variation among P. knowlesi isolates; overall Hd and л were 1±0.034 and 0.01132±0.00124, respectively. A total of nine different haplotypes related to amino acid alterations at 13 positions, and the Pk-MSP-119 sequence was found to be more conserved than Pk-msp-133. We have found evidence for negative selection in Pk-msp-42 as well as the 33kDa and 19kDa fragments by comparing the rate of non-synonymous versus synonymous substitutions. Future investigations should study large numbers of samples from disparate geographical locations to critically assess whether this molecule might be a potential vaccine target for P. knowlesi.
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Affiliation(s)
- Nan Jiun Yap
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia; Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, Australia
| | - Xiang Ting Goh
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Anson V Koehler
- Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, Australia
| | - Timothy William
- Jesselton Medical Centre, Kota Kinabalu, 88300, Sabah, Malaysia
| | - Tsin Wen Yeo
- Communicable Diseases Centre, Institute of Infectious Disease and Epidemiology, Tan Tock Seng Hospital, Moulmein Road, 308433 Singapore, Singapore; Lee Kong Chian School of Medicine, Nanyang Technological University, 11 Mandalay Road, Singapore, 308232, Singapore
| | - Indra Vythilingam
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Robin B Gasser
- Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, Australia; State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.
| | - Yvonne A L Lim
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
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10
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Collins AM. IgG subclass co-expression brings harmony to the quartet model of murine IgG function. Immunol Cell Biol 2016; 94:949-954. [PMID: 27502143 DOI: 10.1038/icb.2016.65] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 07/12/2016] [Accepted: 07/14/2016] [Indexed: 12/24/2022]
Abstract
A model of murine IgG function is presented in which the co-expression of the IgG subclasses is a central feature, class switching occurs before the commencement of somatic hypermutation, and there is little switching between subclasses. It is named the quartet model to emphasize the harmony that comes from the simultaneous presence of the four subclasses. In this model, IgG3 and IgG2b antibodies are particularly important early in the response, when T-cell help may be limiting. IgG3 initiates inflammation through complement fixation, whereas IgG2b provides early FcγR-mediated effector functions. As T-cell help strengthens, IgG2a antibodies increase the power of the response, whereas IgG1 production helps limit the inflammatory drive and limits immunopathology. The model highlights the fact that murine IgG subclasses function quite differently to human IgG subclasses. This allows them to serve the special immunological needs of a species that is vulnerable because of its small size.
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Affiliation(s)
- Andrew M Collins
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia
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11
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De Silva JR, Lau YL, Fong MY. Expression and Evaluation of Recombinant Plasmodium knowlesi Merozoite Surface Protein-3 (MSP-3) for Detection of Human Malaria. PLoS One 2016; 11:e0158998. [PMID: 27391270 PMCID: PMC4938616 DOI: 10.1371/journal.pone.0158998] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 06/24/2016] [Indexed: 11/30/2022] Open
Abstract
Malaria remains a major health threat in many parts of the globe and causes high mortality and morbidity with 214 million cases of malaria occurring globally in 2015. Recent studies have outlined potential diagnostic markers and vaccine candidates one of which is the merozoite surface protein (MSP)-3. In this study, novel recombinant Plasmodium knowlesi MSP-3 was cloned, expressed and purified in an Escherichia coli system. Subsequently, the recombinant protein was evaluated for its sensitivity and specificity. The recombinant pkMSP-3 protein reacted with sera from patients with P. knowlesi infection in both Western blot (61%) and ELISA (100%). Specificity-wise, pkMSP-3 did not react with healthy donor sera in either assay and only reacted with a few non-malarial parasitic patient sera in the ELISA assay (3 of 49). In conclusion, sensitivity and specificity of pkMSP-3 was found to be high in the ELISA and Western Blot assay and thus utilising both assays in tandem would provide the best sero-diagnostic result for P. knowlesi infection.
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Affiliation(s)
- Jeremy Ryan De Silva
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Yee-Ling Lau
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
- Tropical Disease Research and Education Centre, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
- * E-mail:
| | - Mun-Yik Fong
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
- Tropical Disease Research and Education Centre, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
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12
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Cheong FW, Fong MY, Lau YL. Identification and characterization of epitopes on Plasmodium knowlesi merozoite surface protein-142 (MSP-142) using synthetic peptide library and phage display library. Acta Trop 2016; 154:89-94. [PMID: 26624919 DOI: 10.1016/j.actatropica.2015.11.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 10/07/2015] [Accepted: 11/09/2015] [Indexed: 10/22/2022]
Abstract
Plasmodium knowlesi can cause potentially life threatening human malaria. The Plasmodium merozoite surface protein-142 (MSP-142) is a potential target for malaria blood stage vaccine, and for diagnosis of malaria. Two epitope mapping techniques were used to identify the potential epitopes within P. knowlesi MSP-142. Nine and 14 potential epitopes were identified using overlapping synthetic peptide library and phage display library, respectively. Two regions on P. knowlesi MSP-142 (amino acid residues 37-95 and residues 240-289) were identified to be the potential dominant epitope regions. Two of the prominent epitopes, P10 (TAKDGMEYYNKMGELYKQ) and P31 (RCLLGFKEVGGKCVPASI), were evaluated using mouse model. P10- and P31-immunized mouse sera reacted with recombinant P. knowlesi MSP-142, with the IgG isotype distribution of IgG2b>IgG1>IgG2a>IgG3. Significant higher level of cytokines interferon-gamma and interleukin-2 was detected in P31-immunized mice. Both P10 and P31 could be the suitable epitope candidates to be used in malaria vaccine designs and immunodiagnostic assays, provided further evaluation is needed to validate the potential uses of these epitopes.
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13
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Sonaimuthu P, Cheong FW, Chin LC, Mahmud R, Fong MY, Lau YL. Detection of human malaria using recombinant Plasmodium knowlesi merozoire surface protein-1 (MSP-1₁₉) expressed in Escherichia coli. Exp Parasitol 2015; 153:118-22. [PMID: 25812552 DOI: 10.1016/j.exppara.2015.03.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 03/10/2015] [Accepted: 03/20/2015] [Indexed: 01/30/2023]
Abstract
Malaria remains one of the world's most important infectious diseases and is responsible for enormous mortality and morbidity. Human infection with Plasmodium knowlesi is widely distributed in Southeast Asia. Merozoite surface protein-1₁₉ (MSP-1₁₉), which plays an important role in protective immunity against asexual blood stage malaria parasites, appears as a leading immunogenic antigen of Plasmodium sp. We evaluated the sensitivity and specificity of recombinant P. knowlesi MSP-1₁₉ (rMSP-1₁₉) for detection of malarial infection. rMSP-1₁₉ was expressed in Escherichia coli expression system and the purified rMSP-1₁₉ was evaluated with malaria, non-malaria and healthy human serum samples (n = 215) in immunoblots. The sensitivity of rMSP-1₁₉ for detection of P. knowlesi, Plasmodium falciparum, Plasmodium vivax and Plasmodium ovale infection was 95.5%, 75.0%, 85.7% and 100%, respectively. rMSP-1₁₉ did not react with all the non-malaria and healthy donor sera, which represents 100% specificity. The rMSP-1₁₉ could be used as a potential antigen in serodiagnosis of malarial infection in humans.
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Affiliation(s)
| | - Fei Wen Cheong
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Lit Chein Chin
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Rohela Mahmud
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; Tropical Disease Research and Education Centre (TIDREC), Faculty of Medicine, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Mun Yik Fong
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; Tropical Disease Research and Education Centre (TIDREC), Faculty of Medicine, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Yee Ling Lau
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; Tropical Disease Research and Education Centre (TIDREC), Faculty of Medicine, University of Malaya, Kuala Lumpur 50603, Malaysia.
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14
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Sheikh IH, Kaushal DC, Singh V, Kumar N, Chandra D, Kaushal NA. Cloning, overexpression and characterization of soluble 42kDa fragment of merozoite surface protein-1 of Plasmodium vivax. Protein Expr Purif 2014; 103:64-74. [PMID: 25195175 DOI: 10.1016/j.pep.2014.08.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/19/2014] [Accepted: 08/25/2014] [Indexed: 11/24/2022]
Abstract
Plasmodium vivax represents the second most prevalent malaria species of major public health importance and the global eradication of malaria requires the development of vaccines to prevent infection. The lack of in vitro culture and a suitable animal model for P. vivax malaria are the major problems for the delay in developing a functional vivax vaccine. A number of antigens have been identified for P. vivax as potential malaria vaccine candidates and among these 42kDa fragment of merozoite surface protein-1 (MSP-142) is one of most promising antigen of asexual blood stage. In most of the earlier studies, the MSP-142 of malaria parasites was expressed as insoluble protein in inclusion bodies and it is difficult to get purified protein in conformation form. In the present study, we have cloned, overexpressed and characterized the 42kDa fragment of P. vivax MSP-1 as soluble protein in Escherichiacoli. The 42kDa gene fragment of P. vivax MSP-1 was PCR amplified using specific primers, sequenced and subcloned into pTriEx-4 expression vector. The optimum expression of recombinant P. vivax protein was obtained in SOC growth medium by inducing with 0.2mM IPTG at 37°C for 4h. The SDS-PAGE analysis showed a fusion protein of 55kDa and about 80% was present in soluble form. The purified P. vivax MSP-142 was characterized and found to be correctly folded and in conformation form as evident by CD spectroscopy, presence of 1 free -SH group and the reactivity with reduction sensitive conformational monoclonals against P. vivax MSP-142.
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Affiliation(s)
- Inayat Hussain Sheikh
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India; Department of Biochemistry, Lucknow University, Lucknow, India
| | - Deep C Kaushal
- Amity University Uttar Pradesh, Lucknow Campus, Lucknow 226010, India
| | - Vandana Singh
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Niraj Kumar
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Deepak Chandra
- Department of Biochemistry, Lucknow University, Lucknow, India
| | - Nuzhat A Kaushal
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India.
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15
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Murphy JR, Weiss WR, Fryauff D, Dowler M, Savransky T, Stoyanov C, Muratova O, Lambert L, Orr-Gonzalez S, Zeleski KL, Hinderer J, Fay MP, Joshi G, Gwadz RW, Richie TL, Villasante EF, Richardson JH, Duffy PE, Chen J. Using infective mosquitoes to challenge monkeys with Plasmodium knowlesi in malaria vaccine studies. Malar J 2014; 13:215. [PMID: 24893777 PMCID: PMC4070636 DOI: 10.1186/1475-2875-13-215] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 03/03/2014] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND When rhesus monkeys (Macaca mulatta) are used to test malaria vaccines, animals are often challenged by the intravenous injection of sporozoites. However, natural exposure to malaria comes via mosquito bite, and antibodies can neutralize sporozoites as they traverse the skin. Thus, intravenous injection may not fairly assess humoral immunity from anti-sporozoite malaria vaccines. To better assess malaria vaccines in rhesus, a method to challenge large numbers of monkeys by mosquito bite was developed. METHODS Several species and strains of mosquitoes were tested for their ability to produce Plasmodium knowlesi sporozoites. Donor monkey parasitaemia effects on oocyst and sporozoite numbers and mosquito mortality were documented. Methylparaben added to mosquito feed was tested to improve mosquito survival. To determine the number of bites needed to infect a monkey, animals were exposed to various numbers of P. knowlesi-infected mosquitoes. Finally, P. knowlesi-infected mosquitoes were used to challenge 17 monkeys in a malaria vaccine trial, and the effect of number of infectious bites on monkey parasitaemia was documented. RESULTS Anopheles dirus, Anopheles crascens, and Anopheles dirus X (a cross between the two species) produced large numbers of P. knowlesi sporozoites. Mosquito survival to day 14, when sporozoites fill the salivary glands, averaged only 32% when donor monkeys had a parasitaemia above 2%. However, when donor monkey parasitaemia was below 2%, mosquitoes survived twice as well and contained ample sporozoites in their salivary glands. Adding methylparaben to sugar solutions did not improve survival of infected mosquitoes. Plasmodium knowlesi was very infectious, with all monkeys developing blood stage infections if one or more infected mosquitoes successfully fed. There was also a dose-response, with monkeys that received higher numbers of infected mosquito bites developing malaria sooner. CONCLUSIONS Anopheles dirus, An. crascens and a cross between these two species all were excellent vectors for P. knowlesi. High donor monkey parasitaemia was associated with poor mosquito survival. A single infected mosquito bite is likely sufficient to infect a monkey with P. knowlesi. It is possible to efficiently challenge large groups of monkeys by mosquito bite, which will be useful for P. knowlesi vaccine studies.
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16
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Jeremiah S, Janagond AB, Parija SC. Challenges in diagnosis of Plasmodium knowlesi infections. Trop Parasitol 2014; 4:25-30. [PMID: 24754023 PMCID: PMC3992798 DOI: 10.4103/2229-5070.129156] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Accepted: 03/20/2014] [Indexed: 11/15/2022] Open
Abstract
Plasmodium knowlesi is the fifth species of Plasmodium recently identified to cause human malaria. Infections with P. knowlesi are currently being reported from South-East Asian countries and the incidence is on the rise with a possibility of spread to the geographically contiguous countries. P. knowlesi infections can result in a high degree of parasitemia causing severe malaria in a larger proportion of infected individuals. If detected early and treated with appropriate antimicrobials, these infections show a significant clinical improvement. The widely used microscopic methods usually misidentify P. knowlesi as the less pathogenic Plasmodium malariae leading to inadequate therapy and adverse clinical outcomes. The currently popular rapid immuno-chromatographic card tests have a very low sensitivity in diagnosing knowlesi malaria and can erroneously report P. knowlesi as other Plasmodia and vice-versa. At present molecular methods are the most efficacious in diagnosing P. knowlesi infections, but these tests can produce a false positive report in Plasmodium vivax infections and require expensive equipment and trained personnel. An ideal diagnostic test for P. knowlesi infections, which is potent, cost-effective and practically feasible in the resource limited setting is yet to be developed.
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Affiliation(s)
- Ss Jeremiah
- Department of Microbiology, Velammal Medical College Hospital and Research Institute, Madurai, Tamil Nadu, India
| | - Anand B Janagond
- Department of Microbiology, Velammal Medical College Hospital and Research Institute, Madurai, Tamil Nadu, India
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