Biochemistry and Molecular Biology

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Hyperparasitaemia during clinical malaria episodes in infants aged 0–24 months and its association with in utero exposure to Plasmodium falciparum
(BMC research notes, 2018) Sylvester, Boniphace
Existing information has shown that infants who are prenatally exposed to P. falciparum are susceptible to subsequent malaria infections. However, the effect of prenatal exposure to P. falciparum on parasite density during clinical malaria episodes has not been fully elucidated. This study is a component of a prospective cohort study for which initial results have been published. This component was designed to determine the effect of prenatal exposure to P. falciparum on parasite density during clinical malaria episodes in the first 24 months of life. A total of 215 infants were involved and monitored for clinical malaria episodes defined by fever (≥ 37 °C) and parasitaemia. The geometric mean parasite counts between exposed and unexposed infants were compared using independent samples t test. The effect of in utero exposure to P. falciparum on parasite density was assessed using binary logistic regression. Results The geometric mean parasite count per µl of blood during clinical malaria episodes in exposed infants was 24,889 (95% CI 18,286–31,490) while in unexposed infants it was 14,035 (95% CI 12,111–15,960), P < 0.05. Prenatal exposure to P. falciparum was associated with hyperparasitaemia during clinical malaria episodes (OR 7.04, 95% CI 2.31–21.74), while other factors were not significantly associated (P > 0.05).
Interferon-γ and Interleukin-10 Responses during Clinical Malaria Episodes in Infants Aged 0–2 Years Prenatally Exposed to Plasmodium falciparum: Tanzanian Birth Cohort
(Journal of tropical medicine, 2018) Sylvester, Boniphace
Background. Infants born to mothers with placental malaria are prenatally exposed to Plasmodium falciparum antigens. However, the effect of that exposure to subsequent immune responses has not been fully elucidated. This study aimed at determining the effect of prenatal exposure to P. falciparum on Interleukin-10 and Interferon-γ responses during clinical malaria episodes in the first 24 months of life. Methods. This prospective cohort study involved 215 infants aged 0-2 years born to mothers with or without placental malaria. Enzyme-linked immunosorbent assay (ELISA) was used to determine levels of IL-10 and IFN-γ in infants and detect IgM in cord blood. Data were analyzed using SPSS version 20. Findings. Geometric mean for IFN-γ in exposed infants was 557.9 pg/ml (95% CI: 511.6-604.1) and in unexposed infants it was 634.4 pg/ml (95% CI: 618.2-668.5) (P=0.02). Mean IL-10 was 22.4 pg/ml (95% CI: 19.4-28.4) and 15.1 pg/ml (95%CI: 12.4-17.6), respectively (P=0.01). Conclusions. Prenatal exposure to P. falciparum antigens significantly affects IL-10 and IFN-γ responses during clinical malaria episodes in the first two years of life.
Prenatal exposure to Plasmodium falciparum increases frequency and shortens time from birth to first clinical malaria episodes during the first two years of life: Prospective birth cohort study
(Malaria journal, 2016) Sylvester, Boniphace
Background: Prenatal exposure to Plasmodium falciparum affects development of protective immunity and sus- ceptibility to subsequent natural challenges with similar parasite antigens. However, the nature of these effects has not been fully elucidated. The aim of this study was to determine the effect of prenatal exposure to P. falciparum on susceptibility to natural malaria infection, with a focus on median time from birth to first clinical malaria episode and frequency of clinical malaria episodes in the first 2 years of life. Methods: A prospective birth cohort study was conducted in Rufiji district in Tanzania, between January 2013 and December 2015. Infants born to mothers with P. falciparum in the placenta at time of delivery were defined as exposed, and infants born to mothers without P. falciparum parasites in placenta were defined as unexposed. Placen- tal infection was established by histological techniques. Out of 206 infants recruited, 41 were in utero exposed to P. falciparum and 165 infants were unexposed. All infants were monitored for onset of clinical malaria episodes in the first 2 years of life. The outcome measure was time from birth to first clinical malaria episode, defined by fever (≥37 °C) and microscopically determined parasitaemia. Median time to first clinical malaria episode between exposed and unexposed infants was assessed using Kaplan–Meier survival analysis and comparison was done by log rank. Associa- tion of clinical malaria episodes with prenatal exposure to P. falciparum was assessed by multivariate binary logistic regression. Comparative analysis of mean number of clinical malaria episodes between exposed and unexposed infants was done using independent sample t test. Results: The effect of prenatal exposure to P. falciparum infection on clinical malaria episodes was statistically signifi- cant (Odds Ratio of 4.79, 95 % CI 2.21–10.38, p < 0.01) when compared to other confounding factors. Median time from birth to first clinical malaria episode for exposed and unexposed infants was 32 weeks (95 % CI 30.88–33.12) and 37 weeks (95 % CI 35.25–38.75), respectively, and the difference was statistically significant (p = 0.003). The mean number of clinical malaria episodes in exposed and unexposed infants was 0.51 and 0.30 episodes/infant, respec- tively, and the difference was statistically significant (p = 0.038). Conclusions: Prenatal exposure to P. falciparum shortens time from birth to first clinical malaria episode and increases frequency of clinical malaria episodes in the first 2 years of life.
Prenatal Exposure to Plasmodium Falciparum Lowers Humoral Responses during Clinical Malaria Episodes
(African Journal of Applied Research, 2018) Sylvester, Boniphace
Prenatal exposure to Plasmodium falciparum infection affects the development of fetal immune cells in utero by inducing immunotolerance or immunosensitization of fetal immune cells to P.falciparum antigens. This study aimed at determining the effect of prenatal exposure to P.falciparum on specific humoral responses, with a focus on immunoglobulin M (IgM) and total IgG against blood stage Plasmodium falciparum merozoite surface protein 1 (PfMSP1-19) and Plasmodium falciparum merozoite surface protein2 (PfMSP2) during clinical malaria episodes in the first 24 months of life. A birth cohort study was conducted in Rufiji district, between January 2013 and June 2017. Infants (n=215) were recruited after delivery from mothers who were diagnosed of placental malaria (pm+) and without placental malaria (pm-). Total IgG against P.fMSP2 in peripheral blood of exposed and unexposed infants were 49.4 (95% CI 43.5-55.4) and 64.6 (95% CI 61.1-68.2) antibody units respectively, and the difference was statistically significant (P<0.01). The levels of IgM against PfMSP2 in exposed and unexposed infants during clinical malaria episodes were 47.9 (42.8-52.9) and 58.8 (56.1-61.6 respectively, and the difference was statistically significant (P<0.01). Prenatal exposure to Plasmodium falciparum modulates humoral immune response to specific Pf MSP1-19 and PfMSP2 with characteristically low total IgG and IgM in infants aged 0-2 years during clinical malaria episodes
Prevalence and factors associated with persistent transmission of Schistosoma haematobium among primary school children after five rounds of mass drug administration using praziquantel: A cross sectional study in Mkuranga district,Tanzania
(Tropical Doctor, 2022-08-02) Sylvester, Boniphace
Despite a human schistosomiasis control programme through praziquantel mass drug administration (MDA) between 2011 and 2015,there was still persistent transmission among primary schoolchildren (PSC) in Mkuranga district, Tanzania. Our cross-sectional study was conducted among 396 PSC who provided urine for diagnosis of Schistosoma haematobium infection. Observations were conducted to determine PSC water contact activities. Logistic regression was used to test association between dependent and independent variables. We found MDA uptake among PSC as 72.5%, and the prevalence of Schistosoma haematobium infection 5.8%. The risk of infection increased among PSC engaged in fetching water and adjusted odds ratio (AOR) for swimming, bathing, fishing, crossing ponds and paddy fields were 0.123, 0.166, 0.232, 0.202 and 0.093 respectively. Thus we conclude that multiple water contact activities and low participation in MDA is responsible for persistent Schistosoma transmission.
Reports on plasmodium falciparum histidine rich protein 2/3 gene deletions among african countries between January 2010 and december 2021 employed different methodological approaches: A systematic review
(International Journal of Tropical Disease and Health, 2023-04-01) Sylvester, Boniphace
Background: Plasmodium falciparum histidine rich protein 2/3 gene deletions (Pfhrp2/3gd) threatens usefulness of mRDT in diagnosing malaria cases. This review was performed to assess the methods used to report findings on those deletions between January 2010 and December 2021. Methods: Present search was performed using Medline, Google Scholar and PubMed. Results: Out of 94 articles identified, 19% (n=18) were included. Reviewed articles varied in methods employed to report those deletions. Conclusion: Methodological approaches for the Reports between January 2010 and December 2021 on Pfhrp2/3gd are varying and this implies that the findings may not be generalized. Prospective studies aiming at assessing Pfhrp2/3gd need to consider WHO guidelines since such studies are important in assessing the magnitude of Pfhrp2/3gd and therefore provide information towards formulating and change of policies aiming at malaria control.

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