Zakaria Seidu

Background: IgG-mediated effector functions are modulated by the antibody Fc-region glycan composition, and the absence of core fucose is a strong modifier of NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC). Most plasma IgG is fully Fc-fucosylated, but antigens displayed on host-derived membranes can selectively induce Fc-afucosylated IgG. These antigens include alloantigens, enveloped virus surface proteins, and PfEMP1, a malaria parasite protein expressed on the surface of Plasmodium falciparum-infected erythrocytes (IEs). Methods: We determined levels and Fc-fucosylation of IgG specific for several P. falciparum antigens in plasma from children naturally exposed to P. falciparum and from vaccinated adults. Results: IgG specific for PfEMP1 (known to be exposed on the IE surface) and PfGARP, a putative IE surface antigen, were markedly Fc-afucosylated, whereas IgG specific for antigens on parasite membranes (merozoites, gametocytes/gametes, and sporozoites) were fully Fc-fucosylated in most of the children naturally exposed to P. falciparum studied here. Immunization of adults with recombinant proteins (MSP1, Pfs230, and CSP) also consistently induced fully Fc-fucosylated IgG. Children with Fc-afucosylated PfGARP-specific IgG had reduced risk of carrying P. falciparum parasites, independent of levels of PfGARP-specific IgG. Conclusions: These results reinforce the hypothesis that Fc-afucosylation of antigen-specific IgG requires exposure of the antigen on a host membrane (context) and is a function of antigen exposure. Host-specific factors appear to play a minor role in this context.

Toxic metals (TMs) are metallic contaminants that cause adverse health effects even at low exposure levels. Arsenic (As), Manganese (Mn), Lead (Pb), and Cadmium (Cd) are among these contaminants of concern, causing irreversible developmental damage to children (Pb), as well as cardiovascular disease (Pb) and cancers (As) in adults. Arsenic and Manganese are primarily geogenic groundwater contaminants that can also be introduced to drinking water systems by localized anthropogenic contamination sources. Corrosion of lead-containing plumbing components contributes to much of the Lead in drinking water, while localized anthropogenic pollution can leach into some otherwise clean water sources as well. Cadmium is often used in fertilizers and can be an indicator of anthropogenic contamination. We reviewed published studies reporting on concentrations of As, Mn, Pb, and Cd in Ghanaian drinking water quality to assess the occurrence and potential health implications of these TMs. As part of a larger systematic review, we searched for peer-reviewed literature from PubMed, EBSCO Global Health, and the Web of Science, between November 2019 and March 17, 2025, to retrieve studies published in English after 1968 that assessed toxic metals levels or contamination in drinking water in Low- and Middle-Income Countries. This generated 20,552 studies from the initial search, which were screened down to 3,993 studies for extraction. We selected the 93 studies that measured a TM in Ghanaian drinking water for full-text review and data extraction. We focused on Arsenic, Manganese, Lead, and Cadmium, for which we had the most data on metals with WHO limits. 79 studies reported concentrations of Arsenic, Manganese, Lead, and/or Cadmium. A quality evaluation was carried out for these studies by assessing the suitability of reported sample collection, analysis, and quality assurance/quality control practices, and by extracting information on the source of drinking water, GPS coordinates, and observed concentrations for each TM. This resulted in the inclusion of 93 studies comprising 82,111 samples, with 8,124, 11,882, 6,079, and 6,679 observations for Arsenic, Manganese, Lead, and Manganese, respectively. We found that 18%, 34%, 17%, and 15% of included Ghanaian drinking water samples exceeded the WHO Guideline Values for Arsenic, Manganese, Lead, and Cadmium, respectively. Data were widespread across Ghana, though we found few studies in the regions north of Kumasi. These findings comprise sufficient evidence to recommend preventative action to eliminate such contamination in new drinking water systems in Ghana, as well as to explore potential interventions to progressively prioritize and remediate the most serious existing exposures to TMs in existing drinking water systems.

Lead (Pb) in drinking water causes organ damage, cardiovascular disease, cancers, and lifelong neurological and developmental impairment, disproportionately harming infants and developing fetuses. However, evidence on lead in drinking water in low- and middle-income countries (LMICs) is limited and lacks robust synthesis, impeding action. We conducted a systematic review and meta-analysis of peer-reviewed studies reporting lead in drinking water in LMICs, according to PRISMA guidelines. We searched PubMed, Scopus, and Web of Science for studies published in English since 1969 reporting lead concentrations in drinking water. Study relevance was ranked using supervised clustering and machine learning. Relevant studies were manually screened for inclusion; data were manually extracted from included studies. Within-study risk of bias was scored using quality items defined in this work. Between-study bias was assessed based on continuity and symmetry of the (roughly lognormal) distribution of data included in the review. Of approximately 40,000 search results (for both lead and other TMs), 16,868 scored relevant using a trained machine learning algorithm; of these, 3,187 met inclusion criteria. Approximately one third (n=1,088) reported on lead. Central and Southern Asia accounted for 45% of included datasets, while 31% of LMICs were unrepresented. Many studies (45%) had sites purposively selected for known or suspected contamination; after excluding such “targeted” studies, metaregression indicated that >20% (95% CI: 20-27%) of samples exceeded World Health Organization (WHO) guideline values for lead (n=523). Potential sources of bias within studies include sample collection and analysis limitations (lower quality studies) and purposive site selection (“targeted” studies); potential sources of bias among studies include language limitations, exclusion of grey literature, geographic heterogeneity of datasets, and potential publication bias. This work suggests that lead contaminates drinking water at levels of health concern in LMICs worldwide, and that increased collective efforts to prevent, manage, and monitor such contamination are merited.

Microbial contamination of drinking water contributes to disease burdens that disproportionately impact infants and children and are largely preventable through suitable design, operation, monitoring, and management of improved water systems. The World Health Organization (WHO) has published guidance on water safety planning, water quality monitoring, and management approaches, including recommendations on sanitary inspection (SI) of water systems to detect and manage microbial hazards associated with fecal contamination. SI is a low-cost risk assessment tool for water systems based on observable risk factors (RFs) associated with potential water safety hazards. While SI has been previously studied, much of the literature has not quantitatively explored rainfall interactions with SI risk as drivers of fecal contamination. We merged remote-sensing rainfall estimates with SI and water quality data collected from 966 rural boreholes in Ethiopia, Ghana, and Burkina Faso. Logistic regressions (binary and ordinal) were used to characterize associations of total SI score, as well as individual risk factors (RFs), and classes of RFs (i.e., “Source,” “Transport,” and “Barrier” risks) with fecal indicator bacteria (FIB) occurrence, controlling for rainfall (over the past 1–15 days before sampling). We found associations (P < 0.05, OR: 3.5, 95% CI 1.05-11.66) between SI scores and E. coli risk categories controlling for fifteen-day total rainfall. Furthermore, interactions between rainfall and risk factors in the “barrier” category, and the “transport” category were associated with E. coli occurrence. Several individual RFs were also significantly associated with microbial contamination. Incorporating precipitation into models improved model fit characteristics (improved Pseudo R squared and AIC value); specifically, accounting for cumulative rainfall during the fifteen days before sampling improved model fit (increased pseudo-R² from 0.035 to 0.05) for E. coli contamination. These findings can inform design, construction, maintenance, and monitoring of boreholes and prompt timely remediation of defects in such systems, potentially enhancing water safety.

Protective immunity to malaria depends on acquisition of parasite-specific antibodies, with Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) being one of the most important target antigens. The effector functions of PfEMP1-specific IgG include inhibition of infected erythrocyte (IE) sequestration and opsonization of IEs for cell-mediated destruction. IgG glycosylation modulates antibody functionality, with increased affinity to FcγRIIIa for IgG lacking fucose in the Fc region (Fc-afucosylation). We report here that selective Fc-afucosylation of PfEMP1-specific IgG1 increases with age in P. falciparum-exposed children and is associated with reduced risk of anemia, independent of the IgG levels. A similar association was found for children having PfEMP1-specific IgG1 inducing multiple effector functions against IEs, particularly those associated with antibody-dependent cellular cytotoxicity (ADCC) by NK cells. Our findings provide new insights regarding protective immunity to P. falciparum malaria and highlight the importance of cell-mediated destruction of IgG-opsonized IEs.

Microbial contamination of drinking water contributes to a substantive and preventable burden of enteric disease that disproportionately impacts infants and children. The World Health Organization (WHO) has published guidance on water safety and water quality monitoring, including sanitary inspection (SI) of water systems to detect and manage hazards such as fecal contamination. Sanitary inspection is a low-cost, on-site risk assessment tool for water supply systems based on observable risk factors (RFs) associated with potential hazards or defects. While water quality sampling and analysis methods are well characterized, SI as a tool for risk management in drinking water systems is under-studied. We used SI and water quality data from 966 rural boreholes in Ethiopia, Ghana, and Burkina Faso and merged these with remote-sensing rainfall estimates based on household location. Logistic regressions (binary and ordinal) were used to characterize associations of total SI risk score, as well as individual risk factors (RFs), and classes of RFs (i.e., “Source,” “Transport,” and “Barrier” risks) with fecal indicator bacteria (FIB) occurrence as the outcome, controlling for estimated cumulative rainfall (over the past 1-15 days before sampling). We found associations (P<0.05, OR: 3.5, 95% CI 1.05-11.66) between SI scores and E. coli risk categories controlling for fifteen-day cumulative rainfall. Furthermore, risk factors in the “barrier” category, such as the presence and adequacy of fencing around boreholes, concrete pads, and walls extending below the ground, were associated with the E. coli risk category. When examining individual RFs in the regression models, the presence of human excreta 10 m from the source (OR: 2.53), absence of cement floor (OR: 0.16), handpumps that were loosely attached at the base (OR:1.57), adequate fencing to keep animals out (OR: 0.57) and the presence of stagnant water (OR:1.39) were significantly associated with microbial contamination. Incorporating precipitation into models improved model fit characteristics (improved Pseudo R squared and AIC value); specifically, accounting for cumulative rainfall during the fifteen days before sampling improved model fit (increased pseudo-R2 from 0.035 to 0.05) for E. coli contamination. These findings can inform the design, construction, maintenance, and monitoring of boreholes and prompt timely remediation of critical hazards in such systems, potentially enhancing water safety.

Protective immunity to malaria depends on acquisition of parasite-specific antibodies, with Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) being one of the most important target antigens. The effector functions of PfEMP1-specific IgG include inhibition of infected erythrocyte (IE) sequestration and opsonization of IEs for cell-mediated destruction. IgG glycosylation modulates antibody functionality, with increased affinity to FcγRIIIa for IgG lacking fucose in the Fc region (Fc-afucosylation). We report here that selective Fc‑afucosylation of PfEMP1-specific IgG1 increases with age in P. falciparum-exposed children and is associated with reduced risk of anemia and parasitemia, independent of the IgG levels. A similar association was found for children having PfEMP1-specific IgG1 inducing multiple effector functions against IEs. Our findings provide new mechanistic insights regarding protective immunity to malaria and highlight the importance of cell-mediated destruction of IgG-opsonized IEs.

Members of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family are important targets for protective immunity. Abnormal display of PfEMP1 on the surfaces of infected erythrocytes (IEs) and reduced cytoadhesion have been demonstrated in hemoglobin (Hb) AS and HbAC, inherited blood disorders associated with protection against severe P. falciparum malaria. We found that Ghanaian children with HbAS had lower levels of immunoglobulin G against several PfEMP1 variants and that this reactivity increased more slowly with age than in their HbAA counterparts. Moreover, children with HbAS have lower total parasite biomass than those with HbAA at comparable peripheral parasitemias, suggesting impaired cytoadhesion of HbAS IEs in vivo and likely explaining the slower acquisition of PfEMP1-specific immunoglobulin G in this group. In contrast, the function of acquired antibodies was comparable among Hb groups and appears to be intact and sufficient to control parasitemia via opsonization and phagocytosis of IEs.

In vitro culture of asexual blood stages of Plasmodium falciparum is essential to study the parasite biology, and several aspects need to be addressed to successfully cultivate the parasites, including the requirements for red blood cells and specific nutrients. Since Trager and Jensen established the technique in 1976, some modifications have been introduced to improve the growth rate and yield. In brief, the method is based on the use of human red blood cells suspended in RPMI-1640 culture medium supplemented with a source of lipids and maintained at 37 °C in a low-oxygen atmosphere. In this protocol, a description of thawing, culturing, and cryopreservation of asexual blood stages of P. falciparum is presented. Key words Asexual blood stages Cryopreservation In vitro culture Malaria P. falciparum Red blood cells Thawing