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Prah DA, Laryea-Akrong E. Asymptomatic Low-Density Plasmodium falciparum Infections: Parasites Under the Host's Immune Radar? J Infect Dis 2024; 229:1913-1918. [PMID: 38349649 PMCID: PMC11175676 DOI: 10.1093/infdis/jiad581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 12/18/2023] [Indexed: 06/15/2024] Open
Abstract
A large body of evidence suggests that low parasite carriage in Plasmodium falciparum asymptomatic infection is required for the maintenance of malaria immunity. However, the fact that treating such infections has little to no impact on subsequent clinical malaria is rarely noted. In this paper, we review data and argue that low-density parasite carriage in asymptomatic infection may not support host immune processes and that parasites are virtually under the host's immunological radar. We also discuss factors that may be constraining parasitemia in asymptomatic infections from reaching the threshold required to cause clinical symptoms. A thorough understanding of this infectious reservoir is essential for malaria control and eradication because asymptomatic infections contribute significantly to Plasmodium transmission.
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Affiliation(s)
- Diana Ahu Prah
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
- Faculty of Applied Sciences, Department of Science Laboratory Technology, Accra Technical University, Accra, Ghana
| | - Elizabeth Laryea-Akrong
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
- Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, Legon, Ghana
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Johnson AE, Upadhye A, Knight V, Gaskin EL, Turnbull LB, Ayuku D, Nyalumbe M, Abuonji E, John CC, McHenry MS, Tran TM, Ayodo G. Subclinical Inflammation in Asymptomatic Schoolchildren With Plasmodium falciparum Parasitemia Correlates With Impaired Cognition. J Pediatric Infect Dis Soc 2024; 13:288-296. [PMID: 38512283 DOI: 10.1093/jpids/piae025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 03/19/2024] [Indexed: 03/22/2024]
Abstract
BACKGROUND Subclinical inflammation and cognitive deficits have been separately associated with asymptomatic Plasmodium falciparum infections in schoolchildren. However, whether parasite-induced inflammation is associated with worse cognition has not been addressed. We conducted a cross-sectional pilot study to better assess the effect of asymptomatic P. falciparum parasitemia and inflammation on cognition in Kenyan schoolchildren. METHODS We enrolled 240 children aged 7-14 years residing in high malaria transmission in Western Kenya. Children performed five fluid cognition tests from a culturally adapted NIH toolbox and provided blood samples for blood smears and laboratory testing. Parasite densities and plasma concentrations of 14 cytokines were determined by quantitative PCR and multiplex immunoassay, respectively. Linear regression models were used to determine the effects of parasitemia and plasma cytokine concentrations on each of the cognitive scores as well as a composite cognitive score while controlling for age, gender, maternal education, and an interaction between age and P. falciparum infection status. RESULTS Plasma concentrations of TNF, IL-6, IL-8, and IL-10 negatively correlated with the composite score and at least one of the individual cognitive tests. Parasite density in parasitemic children negatively correlated with the composite score and measures of cognitive flexibility and attention. In the adjusted model, parasite density and TNF, but not P. falciparum infection status, independently predicted lower cognitive composite scores. By mediation analysis, TNF significantly mediated ~29% of the negative effect of parasitemia on cognition. CONCLUSIONS Among schoolchildren with PCR-confirmed asymptomatic P. falciparum infections, the negative effect of parasitemia on cognition could be mediated, in part, by subclinical inflammation. Additional studies are needed to validate our findings in settings of lower malaria transmission and address potential confounders that could affect both inflammation and cognitive performance.
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Affiliation(s)
- Alexander E Johnson
- Division of Infectious Diseases, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Aditi Upadhye
- Division of Infectious Diseases, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Veronicah Knight
- Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
| | - Erik L Gaskin
- Division of Infectious Diseases, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Lindsey B Turnbull
- Ryan White Center for Pediatric Infectious Disease and Global Health, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - David Ayuku
- Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya
- Department of Mental Health & Behavioral Sciences, Moi University School of Medicine, Eldoret, Kenya
| | - Mark Nyalumbe
- Department of Mental Health & Behavioral Sciences, Moi University School of Medicine, Eldoret, Kenya
| | - Emily Abuonji
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Chandy C John
- Ryan White Center for Pediatric Infectious Disease and Global Health, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Megan S McHenry
- Ryan White Center for Pediatric Infectious Disease and Global Health, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
- Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya
| | - Tuan M Tran
- Division of Infectious Diseases, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
- Ryan White Center for Pediatric Infectious Disease and Global Health, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - George Ayodo
- Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
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Mooney JP, DonVito SM, Jahateh M, Bittaye H, Bottomley C, D'Alessandro U, Riley EM. Dry season prevalence of Plasmodium falciparum in asymptomatic gambian children, with a comparative evaluation of diagnostic methods. Malar J 2022; 21:171. [PMID: 35672850 PMCID: PMC9172138 DOI: 10.1186/s12936-022-04184-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/10/2022] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Subclinical infection with Plasmodium falciparum remains highly prevalent, yet diagnosing these often low-density infections remains a challenge. Infections can be subpatent, falling below the limit of detection for conventional thick-film microscopy and rapid diagnostic testing (RDT). In this study, the prevalence of subclinical P. falciparum infections in school-aged children was characterised at the start of the dry season in the Upper River Region of The Gambia in 2017/2018, with a goal to also compare the utility of different diagnostic tools. METHODS In a cross-sectional survey of children living in 29 villages on the south bank of the Gambia river (median age of 10 years), matched microscopy, rapid diagnostic test (RDT, detecting histidine-rich protein 2) and polymerase chain reaction (PCR, targeting either 18S rRNA or var gene acidic terminal sequence) were used to determine the prevalence of patent and subpatent infections and to compare the performance of the different diagnostic methods. RESULTS The prevalence of var gene acidic terminal sequence (varATS) qPCR-detectable infections was 10.2% (141/1381) with a median density of 3.12 parasites/µL. Malaria prevalence was highly heterogeneous across the region, ranging from < 1% to ~ 40% prevalence in different village clusters. Compared to varATS, 18S rRNA PCR detected fewer low-density infections, with an assay sensitivity of 50% and specificity of 98.8%. Parasite prevalence in the cohort was 2.9% by microscopy and 1.5% by RDT. Compared to varATS qPCR, microscopy and RDT had sensitivities of 11.5% and 9.2%, respectively, although both methods were highly specific (> 98%). Samples that were positive by all three tests (varATS qPCR, RDT and microscopy) had significantly higher parasite densities (median = 1705 parasites/µL) than samples that were positive by varATS qPCR only (median = 2.4 parasites/µL). CONCLUSIONS The majority of subclinical malaria infections in school-aged children were of extremely low parasite density and detectable only by ultra-sensitive PCR analysis. Understanding the duration of these low density infections, their physiological impact and their contribution to sustained parasite transmission is necessary to inform malaria elimination strategies.
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Affiliation(s)
- Jason P Mooney
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, Kings Buildings, Charlotte Auerbach Rd, Edinburgh, EH9 3FL, UK.
| | - Sophia M DonVito
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, Kings Buildings, Charlotte Auerbach Rd, Edinburgh, EH9 3FL, UK
| | - Maimuna Jahateh
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Haddy Bittaye
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Christian Bottomley
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - Umberto D'Alessandro
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Eleanor M Riley
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, Kings Buildings, Charlotte Auerbach Rd, Edinburgh, EH9 3FL, UK
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Kamau E, Chaudhury S, Bolton JS, Slike BM, Jian N, Eller MA, Eller LA, Ake J, Robb ML, Krebs SJ, Bergmann-Leitner ES. Susceptibility to HIV-1 Acquisition linked to Malaria Exposure: A Case-control Study. Clin Infect Dis 2022; 75:1834-1837. [PMID: 35594548 DOI: 10.1093/cid/ciac384] [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: 01/24/2022] [Indexed: 11/13/2022] Open
Abstract
HIV and malaria infection rates overlap across sub-Saharan Africa, but factors influencing their co-occurrence are unclear. In a case-control study, we investigated whether malaria exposure increases risk of HIV-1 acquisition. Prior to seroconverting, HIV-positive cases had significantly higher malaria-associated antibodies compared to HIV-negative controls, linking malaria exposure to HIV-1 acquisition.
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Affiliation(s)
- Edwin Kamau
- U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA.,Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Sidhartha Chaudhury
- Center for Enabling Capabilities, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Jessica S Bolton
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,Biologics Research and Development, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Bonnie M Slike
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Ningbo Jian
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Michael A Eller
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Leigh Anne Eller
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Julie Ake
- U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Merlin L Robb
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Shelly J Krebs
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Elke S Bergmann-Leitner
- Biologics Research and Development, Walter Reed Army Institute of Research, Silver Spring, MD, USA
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