Biology subjects

Mazhari, R.

Publications and source records attributed to Mazhari, R..

4 recordsLinked to original sources

bioRxiv2025

Navigating parasite antigen genetic diversity in the design of Plasmodium vivax serological exposure markers for malaria

BackgroundPlasmodium vivax poses a major obstacle to malaria elimination because it can lie dormant in the liver for weeks or months before reactivating and causing a relapse of infection. These dormant forms (hypnozoites) cannot be detected using standard diagnostics, but recent P. vivax exposure and by proxy, hypnozoite carriage, can be inferred using antibody-based tests (serological markers). In this study, we examined how genetic variation in P. vivax affects the utility of these antibody markers, and whether redesigned antigens could improve performance. MethodsWe analysed global P. vivax genetic data to assess variation in leading serological markers. Based on this, we produced new antigen versions (haplotypes) that better reflect global sequence diversity, compared to the commonly used reference strain (Sal-1). Antibody responses against these new constructs were then tested using samples from well-characterised cohorts in Brazil and Thailand. Antibody levels were assessed in relation to how recently participants had a qPCR-detectable blood-stage P. vivax infection. We compared the ability of the haplotypes and reference constructs to correctly identify individuals infected within the prior 9-months. FindingsExtensive genetic diversity was identified in two P. vivax antigens, DBPII and MSP5. Several antigens had large numbers of circulating haplotypes globally, with the percentage with similar sequence identity to the reference Sal-1 ranging from 0.4% (MSP5) to 99% (S16). Two antigens exhibited strong differences in immunogenicity by region and construct (RBP2a and DBPII). However, for most proteins (5 out of 8), these differences had little impact on the accuracy of identifying recent exposure. In cases where performance was affected (e.g. RBP2a), this could be overcome by adding multiple antigens into the classification model. InterpretationEven highly diverse antigens can be effective serological exposure markers. Our findings highlight the importance of testing the impact of genetic diversity when designing serological tests and suggest practical strategies, such as using a mix of antigens, to ensure consistent performance across regions.

microbiology↗

bioRxiv2025

Cryo-EM structure of endogenous Plasmodium falciparum Pfs230 and Pfs48/45 fertilization complex

Plasmodium falciparum Pfs230 and Pfs48/45, part of a core fertilization complex, are leading malaria transmission-blocking vaccine candidates. However, how the two proteins interact is unknown. Here we report a 3.36 [A] resolution cryo-electron microscopy structure of the endogenous Pfs230-Pfs48/45 complex. We show that Pfs48/45 interacts with Pfs230 domains 13 and 14, domains that are not included in current Pfs230 vaccine immunogens. Using a transgenic parasite line with a domain 13 to 14 deletion, we show that these domains are essential for Pfs230 localization on the gamete surface. Furthermore, this line significantly reduced oocyst formation in the mosquito midgut, showing that the presence of Pfs230 domains 13 and 14 is critical for successful fertilization. Nanobodies against domains 13 and 14 inhibit Pfs230-Pfs48/45 complex formation, reduce transmission and structural analyses reveal their binding epitopes. Furthermore, domains 13 and 14 are targets of naturally acquired immunity and when delivered as mRNA-LNP immunizations induce potent immune responses and blocked transmission of malaria parasites. Our comprehensive structural insights on a core P. falciparum fertilization complex will guide the design of novel transmission-blocking vaccine candidates against malaria.

microbiology↗

bioRxiv2020

A comparison of non-magnetic and magnetic beads for measuring IgG antibodies against P. vivax antigens in a multiplexed bead-based assay using Luminex(R) technology (Bio-Plex(R)200 or MAGPIX(R))

Multiplexed bead-based assays that use Luminex xMAP(R) technology have become popular for measuring antibodies against proteins of interest in many fields, including malaria and more recently SARS-CoV-2/COVID-19. There are currently two formats that are widely used: non-magnetic beads or magnetic beads. Data is lacking regarding the comparability of results obtained using these two types of beads, and for assays run on different instruments. Whilst non-magnetic beads can only be run on flow-based instruments (such as the Luminex(R) 100/200 or Bio-Plex(R) 200), magnetic beads can be run on both these and the newer MAGPIX(R) instruments. In this study we utilized a panel of purified recombinant Plasmodium vivax proteins and samples from malaria-endemic areas to measure P. vivax-specific IgG responses using different combinations of beads and instruments. We directly compared: i) non-magnetic versus magnetic beads run on a Bio-Plex(R) 200, ii) magnetic beads run on the Bio-Plex(R) 200 versus MAGPIX(R) and iii) non-magnetic beads run on a Bio-Plex(R) 200 versus magnetic beads run on the MAGPIX(R). We also performed an external validation of our optimized assay. We observed that IgG antibody responses, measured against our panel of P. vivax proteins, were strongly correlated in all three of our comparisons, however higher amounts of protein were required for coupling to magnetic beads. Our external validation indicated that results generated in different laboratories using the same coupled beads are also highly comparable, particularly if a reference standard curve is used.

immunology↗

bioRxiv2020

Transcriptional memory-like imprints and enhanced functional activity in γδ T cells following resolution of malaria infection

{gamma}{delta} T cells play an essential role in the immune response to malaria infection. However, long-lasting effects of malaria infection on the {gamma}{delta} T cell population still remain inadequately understood. This study investigated transcriptional changes and memory-like functional capacity of malaria pre-exposed {gamma}{delta} T cells using a Plasmodium chabaudi infection model. We show that multiple genes associated with effector function (chemokines, cytokines and cytotoxicity) and antigen-presentation were upregulated in P. chabaudi-exposed {gamma}{delta} T cells compared to {gamma}{delta} T cells from naive mice. This transcriptional profile was positively correlated with profiles observed in conventional memory CD8+ T cells and was accompanied by enhanced reactivation upon secondary encounter with Plasmodium-infected red blood cells in vitro. Collectively our data demonstrate that Plasmodium exposure result in "memory-like imprints" in the {gamma}{delta} T cell population and also promotes {gamma}{delta} T cells that can support antigen-presentation during subsequent infections.

immunology↗