Biology subjects

Ssewanyana, I.

Publications and source records attributed to Ssewanyana, I..

17 recordsLinked to original sources

bioRxiv2026

Repeated malaria exposure reprograms Vδ2+ γδT cell chromatin accessibility and immune function toward a reversible hyporesponsive state

V{delta}2+ {gamma}{delta} T cells contribute to antimalarial immunity via pro-inflammatory and cytotoxic mechanisms. Among children who have experienced repeated episodes of malaria, V{delta}2+ T cells develop reduced pro-inflammatory function through mechanisms that remain unknown. We hypothesized that recurrent malaria drives coordinated epigenetic and transcriptional remodeling of these semi-innate cells. Using PBMC from Ugandan children in cohorts spanning high and low transmission (10 children) and longitudinally across a marked decline in transmission (20 children, 3 timepoints), we profiled the epigenome and transcriptome of V{delta}2+ T cells by paired bulk ATAC-seq and RNA-seq and by CITE-seq. Higher malaria exposure was associated with reduced V{delta}2+ T cell TNF and IFN{gamma} production and with thousands of differentially accessible chromatin regions. Immunoregulatory genes including LYN, PLCG2, and HAVCR2 (Tim-3) showed increased chromatin accessibility and/or expression at high exposure, whereas pro-inflammatory gene (IFNG, GZMK, IL7R) and AP-1 (JUN/FOS) motif accessibility were increased at low exposure; linkage of regulatory elements with target genes corroborated these associations. Single-cell transcriptional analysis identified a cytotoxic CD8+CD16+CD57+ V{delta}2+ T cell subset. In our in vitro model, repeated stimulation with malaria-infected red blood cells or the phosphoantigen HMBPP was similarly associated with reduced V{delta}2+ T cell degranulation and cytokine production. Diminished responsiveness was predominantly TCR-dependent, accompanied by heightened p38 signaling, and was partially reversed by rest induced by the tyrosine kinase inhibitor dasatinib. Together these data reveal how repeated malaria may reshape cellular immunity by reprogramming V{delta}2+ T cells toward a reversible, hyporesponsive state and highlight targets for therapeutically restoring their function.

immunology↗

bioRxiv2026

Whole-genome characterization of Plasmodium falciparum population structure and drug resistance across Uganda and neighboring countries

Uganda has one of the world's highest malaria burdens, but parasite population structure and connectivity have not been characterized nationally with whole-genome data. We analyzed 249 monoclonal Plasmodium falciparum genomes from 26 sentinel sites across Uganda in 2023 and compared them with publicly available genomes from five neighboring countries. Genetic diversity was high and differentiation low in Uganda, but identity-by-descent detected limited structure. This was most pronounced in the low-transmission southwest, where parasites shared ancestry and recent relatedness with isolates from western Tanzania. Selection scans identified signals at loci associated with resistance to artemisinins and their partner drugs, and to chloroquine and antifolates. The strongest signal was at PfPX1 where the PIN haplotype (L1222P, M1701I, D1705N) reached 70% prevalence nationwide, but selection was carried by PIN haplotypes that had additionally acquired D384A, largely confined to northern and eastern Uganda. A second substitution at the same codon, D384Y, formed a haplotype shared across the Tanzanian border. PfKelch13 variants were partitioned across multiple backgrounds, consistent with repeated independent emergence, and C469Y was enriched on the PfPX1 D384A-PIN background. These genomes provide a 2023 baseline for tracking potential mediators of drug resistance and support coordinated genomic surveillance across Uganda and its neighbors.

genomics↗

bioRxiv2026

PfPHAST: Plasmodium falciparum Public Health Amplicon Sequencing Tool, a Streamlined Panel for Malaria Genomic Surveillance

Genomic tools can support malaria control policy through surveillance of Plasmodium falciparum populations, tracking antimalarial drug resistance, pfhrp2/3 deletions that compromise rapid diagnostic tests, and selection at the circumsporozoite protein (PfCSP) vaccine target, as well as through molecular correction of therapeutic efficacy studies (TES). Multiplex Amplicons for Drug, Diagnostic, Diversity, and Differentiation Haplotypes using Targeted Resequencing (MAD4HatTeR), a comprehensive amplicon sequencing panel covering up to 276 targets, supports these applications but is tailored to research rather than routine programmatic use. We developed P. falciparum Public Health Amplicon Sequencing Tool (PfPHAST), a 56-target derivative of MAD4HatTeR spanning drug resistance loci, pfhrp2/3 deletion, PfCSP genotyping, non-falciparum species identification, and 20 high-heterozygosity microhaplotype loci for TES classification. We compared PfPHAST and MAD4HatTeR using laboratory strain controls, including two-strain dilution series and a five-strain mixture, across parasite densities of 100 to 10,000 parasites/L. At matched per-target depth, PfPHAST achieved a higher quality-control pass rate than MAD4HatTeR (94.4% versus 90.0%) and distributed reads more evenly across targets. The panels showed comparable recall and precision for drug resistance codons and microhaplotypes, reaching near-complete recall above 40% within-sample allele frequency (WSAF) at all densities, with reduced sensitivity for minor alleles below 10% WSAF at low parasite density in both panels. Observed and expected WSAF correlated strongly for both panels, and both resolved a five-strain polyclonal mixture, including a 5% minor strain. By concentrating sequencing capacity on targets of greatest programmatic relevance, PfPHAST offers a scalable, lower-cost alternative to comprehensive research panels without sacrificing performance on shared targets, complementing MAD4HatTeR for routine molecular malaria surveillance.

genomics↗

bioRxiv2026

Circulating T-follicular helper and type I regulatory T cells have overlapping phenotypes in P. falciparum malaria and are maintained by parasite exposure.

Immunity to P. falciparum malaria develops slowly, requiring repeated infection in areas of high transmission, and wanes rapidly in the absence of parasite exposure. Key to this immunity, is the development of antibodies which is supported by CD4 T follicular helper (Tfh) cells that drive robust germinal centre responses. However, in malaria, the malaria-specific CD4 T cell compartment in peripheral blood is dominated by Type 1 regulatory T cells (Tr1), which produce high levels of IL-10 in response to parasites. Tr1-like Tfh cells (Tfh10) have been reported in several settings of repeated antigen stimulation but have not been investigated in malaria. Here we used single-cell RNA sequencing and multiparameter flow cytometry to characterise malaria-specific Tfh and Tr1 cells in a longitudinal cohort of highly exposed individuals and assessed their persistence after transmission interruption. Malaria-specific Tfh and Tr1 cells shared overlapping profiles, and Tr1 cell-like transcriptional signatures and phenotypes were detectable within the Tfh cell compartment. Tfh10 cell subsets were the dominant phenotype of malaria-specific Tfh cells. Following disruption of malaria transmission, the frequencies of malaria-specific Tr1 and Tfh10 cells declined. These findings highlight a close relationship between Tfh and Tr1 cells and show that the Tfh cell compartment in malaria is dominated by Tfh10 cells. The rapid waning of these cells in the absence of continuous exposure is consistent with requirements of persistent antigen in maintaining regulatory CD4 T cell phenotypes.

immunology↗

bioRxiv2026

Maternal malaria and early-life infections shape humoral immunity to P. falciparum in infants

Placental malaria may negatively impact acquisition of immunity to malaria in infants. To study the effect of maternal antibodies on early-life infections, a birth cohort of infants were enrolled in a prospective observational study in Busia, Uganda. We measured P. falciparum-specific antibody responses to 19 P. falciparum antigens and tetanus toxoid in 183 infants using a Luminex multiplex bead array. We also assessed the frequency and phenotype of peripheral T follicular helper cells and B cells using flow cytometry. Placental malaria and lower gestational age adversely impacted antibody transfer overall. Maternal antibodies present in cord blood were not associated with protection in the first year of life, and neither was maternal malaria status. Infants generated antibodies against P. falciparum antigens in response to infection, but these were also not associated with protection, only exposure. Interestingly, infections in the first six months of life correlated with decreased levels of antibodies to P. falciparum antigen at one year of age. Early-life infections were not clearly associated with circulating follicular T cell or B cell phenotypic composition. These data suggest the infant antibody response has little, if any, impact on preventing clinical malaria or patent parasitemia in the first year of life.

immunology↗

bioRxiv2025

The N-terminal region of malaria vaccine candidate Plasmodium falciparum asparagine-rich merozoite antigen is immunodominant and targeted by polyreactive antibodies

The development of malaria blood-stage vaccines has been hampered by sequence variation in many Plasmodium falciparum proteins involved in erythrocyte invasion. In the past few years, asparagine-rich merozoite antigen (PfARMA) has emerged as a potential vaccine candidate due to its low amino acid sequence diversity and the association between anti-PfARMA antibody levels and protection to malaria. Here, we used samples from P. falciparum-exposed individuals to study naturally acquired B cell and antibody responses to PfARMA. B cell responses to PfARMA were dominated by IgM+ B cells that recognized the N-terminal intrinsically disordered region 1 (IDR1) of PfARMA. A human monoclonal antibody (hmAb) to IDR1 was non-neutralizing, while a second hmAb binding to the folded domain showed weak neutralizing activity. Both PfARMA-specific plasma IgM and IgG responses predominately targeted IDR1 and their levels increased with P. falciparum exposure. However, in contrast to previous reports, these antibody responses did not correlate with protection in age and exposure-matched children. Interestingly, approximately 30% of unexposed individuals had IgG that also targeted IDR1 and was polyreactive, binding to regions with high asparagine content. Finally, we determined that PfARMA is located in or near PfEBA-175+ micronemes. These data suggest that while IgG to the folded domain of PfARMA may inhibit parasite growth, antibody responses to PfARMA are primarily directed to IDR1 and may not directly contribute to protection against malaria.

immunology↗

bioRxiv2025

CXCR6⁺ CD127- Tr1 Cells Balance Immunity and Persistence in Plasmodium falciparum Infection

Plasmodium falciparum (Pf) induces the clonal expansion of antigen-specific type 1 regulatory T (Tr1) cells with a capacity for long-term memory. Tr1 cells comprise nearly 90% of the Pf blood stage antigen-specific CD4+ T cell pool in children. Though, whether Tr1 cells contribute to protection from malaria remains undetermined. To address this critical gap in knowledge, we first performed scRNAseq on gated cell populations to validate CXCR6+ CD127- as new phenotypic markers to enrich for bona-fide Tr1 cells. Importantly, these Tr1 cells potently suppressed the proliferation of other CD4+ T cells in vitro via IL-10 secretion. Among children living in malaria-endemic Uganda, CXCR6+ CD127- Tr1 cells were the dominant responding subset to Pf-infected red blood cell stimulation in vitro. They also rapidly expanded following malaria and expressed IL-10 and IFNg during infection in vivo. Tr1 abundance correlated with plasma concentrations of granzyme A, IFNg, IL-10, and LAG3, suggesting that these cells act systemically. Higher CXCR6+ CD127- Tr1 cell frequencies correlated with a lower probability of symptoms given parasitemia but were also associated with delayed parasite clearance among untreated, asymptomatic children. These data suggest that Tr1 cells help mediate clinical immunity to malaria but may also facilitate parasite persistence through mechanisms of immune regulation.

immunology↗

bioRxiv2024

Sensitive and modular amplicon sequencing of Plasmodium falciparum diversity and resistance for research and public health

BackgroundTargeted amplicon sequencing is a powerful and efficient tool for interrogating the Plasmodium falciparum genome, generating actionable data from infections to complement traditional malaria epidemiology. For maximum impact, genomic tools should be multi-purpose, robust, sensitive, and reproducible. MethodsWe developed, characterized, and implemented MAD4HatTeR, an amplicon sequencing panel based on Multiplex Amplicons for Drug, Diagnostic, Diversity, and Differentiation Haplotypes using Targeted Resequencing, along with a bioinformatic pipeline for data analysis. Additionally, we introduce an analytical approach to detect gene duplications and deletions from amplicon sequencing data. Laboratory control and field samples were used to demonstrate the panels high sensitivity and robustness. ResultsMAD4HatTeR targets 165 highly diverse loci, focusing on multiallelic microhaplotypes, key markers for drug and diagnostic resistance (including duplications and deletions), and csp and potential vaccine targets. The panel can also detect non-falciparum Plasmodium species. MAD4HatTeR successfully generated data from low-parasite-density dried blood spot and mosquito midgut samples, and detected minor alleles at within-sample allele frequencies as low as 1% with high specificity in high-parasite-density dried blood spot samples. Gene deletions and duplications were reliably detected in mono- and polyclonal controls. Data generated by MAD4HatTeR were highly reproducible across multiple laboratories. ConclusionsThe successful implementation of MAD4HatTeR in five laboratories, including three in malaria-endemic African countries, showcases its feasibility and reproducibility in diverse settings. MAD4HatTeR is thus a powerful tool for research and a robust resource for malaria public health surveillance and control.

genomics↗

bioRxiv2024

Differences in phenotype between long-lived memory B cells against Plasmodium falciparum merozoite antigens and variant surface antigens

Plasmodium falciparum infections elicit strong humoral immune responses to two main groups of antigens expressed by blood-stage parasites: merozoite antigens that are involved in the erythrocyte invasion process and variant surface antigens that mediate endothelial sequestration of infected erythrocytes. Long-lived B cells against both antigen classes can be detected in the circulation for years after exposure, but have not been directly compared. Here, we studied the phenotype of long-lived memory and atypical B cells to merozoite antigens (MSP1 and AMA1) and variant surface antigens (the CIDR1 domain of PfEMP1) in Ugandan adults before and after local reduction of P. falciparum transmission. After a median of 1.7 years without P. falciparum infections, the percentage of antigen-specific activated B cells declined, but long-lived antigen-specific B cells were still detectable in all individuals. The majority of MSP1/AMA1-specific B cells were CD95+CD11c+ memory B cells, which are primed for rapid differentiation into antibody-secreting cells, and FcRL5-T-bet- atypical B cells. On the other hand, most CIDR1-specific B cells were CD95-CD11c- memory B cells. CIDR1-specific B cells were also enriched among a subset of atypical B cells that seem poised for antigen presentation. These results point to differences in how these antigens are recognized or processed by the immune system and how P. falciparum-specific B cells will respond upon re-infection.

immunology↗

bioRxiv2024

Broadly inhibitory antibodies against severe malaria virulence proteins

Plasmodium falciparum pathology is driven by the accumulation of parasite-infected erythrocytes in microvessels. This process is mediated by the parasites polymorphic erythrocyte membrane protein 1 (PfEMP1) adhesion proteins. A subset of PfEMP1 variants that bind human endothelial protein C receptor (EPCR) through their CIDR1 domains is responsible for severe malaria pathogenesis. A longstanding question is whether individual antibodies can recognize the large repertoire of circulating PfEMP1 variants. Here, we describe two broadly reactive and binding-inhibitory human monoclonal antibodies against CIDR1. The antibodies isolated from two different individuals exhibited a similar and consistent EPCR-binding inhibition of 34 CIDR1 domains, representing five of the six subclasses of CIDR1. Both antibodies inhibited EPCR binding of both recombinant full-length and native PfEMP1 proteins as well as parasite sequestration in bioengineered 3D brain microvessels under physiologically relevant flow conditions. Structural analyses of the two antibodies in complex with two different CIDR1 antigen variants reveal similar binding mechanisms that depend on interactions with three highly conserved amino acid residues of the EPCR-binding site in CIDR1. These broadly reactive antibodies likely represent a common mechanism of acquired immunity to severe malaria and offer novel insights for the design of a vaccine or treatment targeting severe malaria.

immunology↗

bioRxiv2023

Novel hypervariable erythrocyte surface expressed recombinant proteins show promise as serological markers of exposure to Plasmodium falciparum infection.

Malaria caused by Plasmodium spp. leads to significant morbidity and mortality, particularly in Sub-Saharan African countries with Plasmodium falciparum being the predominant infectious species. The pathogenesis of P. falciparum depends on multiple host and parasitic factors, one of which is the evasion of host immune response due to antigenic variability during the blood stage of infection. The understudied infected erythrocyte expressed protein families STEVOR and RIFIN characterize with antigenic hypervariability and are associated with clinical outcome of the infection and protective acquired immunity based on their topology and localization. We have used two molecular tag methods for successful expression of members of STEVOR and RIFIN protein families as recombinant proteins in E. coli expression system. We have further established the antigenicity of those recombinants and have used Ugandan cohort samples with various P. falciparum infectious status and have compared the seropositivity rate to those recombinants in different age groups against already established short- and long-term markers of infection. We have demonstrated age-dependent immunity acquisition against the tested recombinants, and we have suggested the potential use of STEVOR and RIFIN recombinants as novel markers of P. falciparum infection in serosurveillance. Due to the hypervariability of those protein members we propose that further, more extensive research using a library of expressed variants is needed to strengthen the conclusions made in this study.

immunology↗

bioRxiv2022

Single-cell sequencing identifies novel atypical B cell subsets with distinct effector functions

Atypical B cells are a population of activated B cells that are commonly enriched in individuals with chronic immune activation, but are also part of a normal immune response to infection or vaccination. Prior studies to determine the function of these cells have yielded conflicting results, possibly due to functional heterogeneity among this B cell population. To better define the role(s) of atypical B cells in the host adaptive immune response, we performed single-cell sequencing of transcriptomes, cell surface markers, and B cell receptors in individuals with chronic Plasmodium falciparum exposure, a condition known to lead to accumulation of circulating atypical B cells. Our studies identified three previously uncharacterized populations of atypical B cells with distinct transcriptional and functional profiles, that separate into two differentiation pathways. We identified a set of cell surface markers to distinguish these atypical B cell subsets and confirmed their presence in malaria-experienced children and adults using flow cytometry. Plasmodium falciparum-specific cells were present in equal proportions within each of these atypical B cell populations, indicating that all three subsets develop in response to antigen stimulation. However, we observed marked differences among the three subsets in their ability to produce IgG upon T-cell-dependent activation. Collectively, our findings help explain the conflicting observations in prior studies on the functions of atypical B cells and provide a better understanding of their role in the adaptive immune response in chronic inflammatory conditions. One sentence summaryAtypical B cells consist of three subsets that may play distinct roles in the host adaptive immune response.

immunology↗

bioRxiv2022

Proteome-wide antigenic profiling in Ugandan cohorts identifies associations between age, exposure intensity, and responses to repeat-containing antigens in Plasmodium falciparum

Protection against Plasmodium falciparum, which is primarily antibody-mediated, requires recurrent exposure to develop. The study of both naturally acquired limited immunity and vaccine induced protection against malaria remains critical for ongoing eradication efforts. Towards this goal, we deployed a customized P. falciparum PhIP-seq T7 phage display library containing 238,068 tiled 62-amino acid peptides, covering all known coding regions, including antigenic variants, to systematically profile antibody targets in 198 Ugandan children and adults from high and moderate transmission settings. Repeat elements - short amino acid sequences repeated within a protein - were significantly enriched in antibody targets. While breadth of responses to repeat-containing peptides was twofold higher in children living in the high versus moderate exposure setting, no such differences were observed for peptides without repeats, suggesting that antibody responses to repeat-containing regions may be more exposure dependent and/or less durable in children than responses to regions without repeats. Additionally, short motifs associated with seroreactivity were extensively shared among hundreds of antigens, potentially representing cross- reactive epitopes. PfEMP1 shared motifs with the greatest number of other antigens, partly driven by the diversity of PfEMP1 sequences. These data suggest that the large number of repeat elements and potential cross-reactive epitopes found within antigenic regions of P. falciparum could contribute to the inefficient nature of malaria immunity.

immunology↗

bioRxiv2021

Age dependent changes in circulating Tfh cells influence the development of functional antibodies to malaria in children.

T-follicular helper (Tfh) cells are key drivers of antibodies that protect from malaria. However, little is known regarding the host and parasite factors that influence Tfh and functional antibody development. Here, we use samples from a large cross-sectional study of children residing in an area of high malaria transmission in Uganda to characterize Tfh cells and functional antibodies to multiple parasites stages. We identify a dramatic re-distribution of the Tfh cell compartment with age that is independent of malaria exposure, with Th2-Tfh cells predominating in early childhood, while Th1-Tfh cell gradually increase to adult levels over the first decade of life. Functional antibody acquisition is age-dependent and hierarchical acquired based on parasite stage, with merozoite responses followed by sporozoite and gametocyte antibodies. Antibodies were boosted in children with current infection, and were higher in females. The children with the very highest antibody levels had increased Tfh cell activation and proliferation, consistent with a key role of Tfh cells in antibody development. Together, these data reveal a complex relationship between the circulating Tfh compartment, antibody development and protection from malaria.

immunology↗

bioRxiv2021

A comparative analysis of memory B cell and antibody responses against Plasmodium falciparum merozoite surface protein 1 in children and adults from Uganda

Memory B cells (MBCs) and plasma antibodies against Plasmodium falciparum merozoite antigens are important components of the protective immune response against malaria. To gain understanding of how responses against P. falciparum develop in these two arms of the humoral immune system, we evaluated MBC and antibody responses against the most abundant merozoite antigen, merozoite surface protein 1 (MSP1), in individuals from a region in Uganda with high P. falciparum transmission. Our results showed that MSP1-specific B cells in adults with immunological protection against malaria were predominantly IgG+ classical MBCs, while children with incomplete protection mainly harbored IgM+ MSP1-specific classical MBCs. In contrast, anti-MSP1 plasma IgM reactivity was minimal in both children and adults. Instead, both groups showed high plasma IgG reactivity against MSP1 and whole merozoites, with broadening of the response against non-3D7 strains in adults. The antibodies encoded by MSP1-specific IgG+ MBCs carried high levels of amino acid substitutions and recognized relatively conserved epitopes on the highly variable MSP1 protein. Proteomics analysis of MSP119-specific IgG in plasma of an adult revealed a limited repertoire of anti-MSP1 antibodies, most of which were IgG1 or IgG3. Similar to MSP1- specific MBCs, anti-MSP1 IgGs had relatively high levels of amino acid substitutions and their sequences were predominantly found in classical MBCs, not atypical MBCs. Collectively, these results showed evolution of the MSP1-specific humoral immune response with cumulative P. falciparum exposure, with a shift from IgM+ to IgG+ B cell memory, diversification of B cells from germline, and stronger recognition of MSP1 variants by the plasma IgG repertoire.

immunology↗

bioRxiv2020

Plasmodium falciparum serology: A comparison of two protein production methods for analysis of antibody responses by protein microarray

The evaluation of protein antigens as putative serologic biomarkers of infection has increasingly shifted to high-throughput, multiplex approaches such as the protein microarray. In vitro transcription/translation (IVTT) systems - a similarly high-throughput protein expression method - are already widely utilised in the production of protein microarrays, though purified recombinant proteins derived from more traditional whole cell based expression systems also play an important role in biomarker characterisation. Here we have performed a side-by-side comparison of antigen-matched protein targets from an IVTT and purified recombinant system, on the same protein microarray. The magnitude and range of antibody responses to purified recombinants was found to be greater than that of IVTT proteins, and responses between targets from different expression systems did not clearly correlate. However, responses between amino acid sequence-matched targets from each expression system were more closely correlated. Despite the lack of a clearly defined relationship between antigen-matched targets produced in each expression system, our data indicate that protein microarrays produced using either method can be used confidently, in a context dependent manner, though care should be taken when comparing data derived from contrasting approaches. Statement of significance of the studyProtein microarray technology is increasingly being realised as a powerful tool in disease biomarker identification. Protein-based, serologic arrays are already well utilised in the characterisation of antibody responses to the malarial Plasmodium spp., drastically improving throughput and efficiency compared to more typical experimental assays. Such approaches have commonly made use of in vitro transcription/translation (IVTT) protein expression systems, though other protein expression methods are regularly employed. In this study we have directly compared antibody responses in a malaria endemic population, to matched protein antigens derived from both an IVTT and purified bacterial recombinant system in the same protein microarray. We demonstrated that the magnitude of measured antibody response to matched protein antigens tends to be greater to purified recombinants, rather than IVTT products. Further, our analysis showed highly variable levels of correlation of response between antigen-matched targets derived from each expression system, although relationships in antibody response were stronger between proteins with overlapping amino acid sequences. This study highlights the importance of considering the strengths and weaknesses of each expression system in the context of a protein microarray according to experimental hypotheses, and illustrates the need for attention when comparing data generated by these different methodologies.

immunology↗

bioRxiv2020

Impact of a rapid decline in malaria transmission on antimalarial IgG subclasses and avidity

Understanding how immunity to malaria is affected by declining transmission is important to aid vaccine design and understand disease resurgence. Both IgG subclasses and avidity of antigen-specific responses are important components of an effective immune response.Using a multiplex bead array assay, we measured the total IgG, IgG subclasses, and avidity profiles of responses to 18 P. falciparum blood stage antigens in samples from 160 Ugandans collected at 2 time points during high malaria transmission and 2 time points following a dramatic reduction in transmission.Results demonstrated that, for the antigens tested, (i) the rate of decay of total IgG following infection declined with age and was driven consistently by the decrease in IgG3 and occasionally the decrease in IgG1; (ii) the proportion of IgG3 relative to IgG1 in the absence of infection increased with age; (iii) the increase in avidity index (the strength of association between the antibody and antigen) following infection was largely due to a rapid loss of non-avid compared to avid total IgG; and (iv) both avid and non-avid total IgG in the absence of infection increased with age.Further studies are required to understand the functional differences between IgG1 and IgG3 in order to determine their contribution to the longevity of protective immunity to malaria. Measuring changes in antibody avidity may be a better approach of detecting affinity maturation compared to avidity index due to the differential expansion and contraction of high and low avidity total IgG.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗