Biology subjects

Kappe, S.

Publications and source records attributed to Kappe, S..

4 recordsLinked to original sources

bioRxiv2026

Prenatal immune priming to Plasmodium falciparum is characterized by multi-lineage T-cell responses that are influenced by maternal microchimerism and predict malaria outcomes

In malaria endemic settings, the fetus may be exposed to Plasmodium falciparum (Pf) antigens leading to prenatal immune primming (PIP). The fetus also acquires a graft of maternal cells in utero, a phenomenon known as maternal microchimerism (MMc). We have previously identified that MMc at birth predicts altered malaria susceptibility in early childhood, and we hypothesized that this association may be mediated via two potential mechanisms. First, the fetus may acquire Pf-specific MMc T-cells that directly respond to postnatal parasitemia. Alternatively, MMc may indirectly influence the quantity or quality of PIP. To investigate this hypothesis, infant cord bloods from 97 Malian primigravidae were screened for MMc using qPCR. A subset of ten cord blood mononuclear cells with variable MMc levels were stimulated with purified Pf merozoite extract and activated T-cells were sorted by flow cytometry for scRNAseq analysis. Transcriptional profile was used to differentiate Pf-responsive versus bystander activated T-cells, and MMc cells were identified using the Cellector algorithm. Among Pf-responsive cells, we identified four key populations: activated CD4 T-cells, ZBTB16+ CD4 T-cells, activated V{delta}1+ {gamma}{delta} T-cells, and cytotoxic V{gamma}9V{delta}2+ {gamma}{delta} T-cells. The minority of sorted cells were of MMc origin; however, there was a strong association between the presence of MMc and the quantity and quality of PIP. MMc+ infants had significantly fewer Pf-responsive T-cells, as well as a shifted distribution of these cells with fewer ZBTB16+ CD4 and cytotoxic V{gamma}9V{delta}2+ {gamma}{delta} T-cells. Clinically, MMc was protective from incident parasitemia and febrile malaria, whereas the frequencies of ZBTB16+ CD4 and activated CD4 T-cells were associated with increased risk. Together, these data demonstrate that MMc influences malaria outcomes through regulation of offspring inflammatory responses to Pf.

immunology↗

bioRxiv2020

Bulk Segregant Approaches to Nutritional Genomics in Plasmodium falciparum

What genes determine growth and nutrient utilization in asexual blood-stage malaria parasites? Competition experiments between a lab-adapted African parasite (NF54), and a recently isolated Asian parasite (NHP4026) reveal contrasting outcomes in different media: NF54 outcompetes NHP4026 in media containing human serum, while NHP4026 outcompetes NF54 in media containing AlbuMAX, a lipid-rich bovine serum formulation. We conducted parasite genetic crosses and compared genome-wide allele frequency changes in progeny populations cultured in media containing serum or AlbuMAX: this bulk segregant analysis (BSA) reveals three quantitative trait loci (QTL) underlying differential growth. The strongest QTL (chromosome 13) contains EBA-140: competition experiments between EBA-140-knockout and isogenic wildtype parasites showed fitness reversals in the two media types, validating this locus as the causative gene. These results (i) demonstrate the effectiveness of BSA for dissecting fitness traits in Plasmodium falciparum, and (ii) reveal an intimate link between red blood cell invasion and nutrient composition of growth media.

genetics↗

bioRxiv2019

Genetic mapping of fitness determinants across the malaria parasite Plasmodium falciparum life cycle

Malaria is transmitted through female Anopheline mosquitoes where gamete fusion and meiosis occurs, and humans where parasites proliferate asexually. We describe a powerful approach to identify the genetic determinants of parasite fitness across both invertebrate and vertebrate life-cycle stages in human malaria parasite Plasmodium falciparum using bulk segregant analysis (BSA). We combined experimental genetic crosses using humanized mice, with selective whole genome amplification and BSA at multiple developmental stages in both mosquito and vertebrate host to examine parasite competition and identify genomic regions under selection. We generated crosses between artemisinin resistant (ART-R, kelch13-C580Y) and ART-sensitive (ART-S, kelch13-WT) parasite clones recently isolated from Southeast Asian patients. We then quantified genome-wide changes in allele frequency in the parasite progeny population from infected midgut and salivary glands of Anopheles stephensi mosquitoes, infected livers, emerging merozoites and aliquots of in vitro cultured progeny parasites at intervals over 30 days. Three striking results emerge: we observed (i) a strong skew (>80%) towards alleles from the ART-R parent in the mosquito stage, that dropped to [~]50% in the blood stage as selfed ART-R parasites were selected against; (ii) highly repeatable skews in allele frequencies across the genome in blood stage parasites; (iii) particularly strong selection (selection coefficient (s) [≤] 0.18/asexual cycle) against alleles from the ART-R parent at loci on chromosome 12 containing MRP2 and chromosome 14 containing ARPS10. This approach robustly identifies selected loci and has strong potential for identifying parasite genes that interact with the mosquito vector or compensatory loci involved in drug resistance.

evolutionary biology↗

bioRxiv2017

Integrated transcriptomic, proteomic and epigenomic analysis of Plasmodium vivax salivary-gland sporozoites

Plasmodium vivax is the key obstacle to malaria elimination in Asia and Latin America, largely attributed to its ability to form resilient hypnozoites (sleeper-cells) in the host liver that escape treatment and cause relapsing infections. The decision to form hypnozoites is made early in the liver infection and may already be set in sporozoites prior to invasion. To better understand these early stages of infection, we undertook a comprehensive transcriptomic and histone epigenetic characterization of P. vivax sporozoites. The salivary-gland sporozoite transcriptome is heavily composed of transcripts associated with functions needed for early infection of the vertebrate host and development within hepatocytes. Through comparisons to recently published proteome data for the P. vivax sporozoite, our study finds that although highly transcribed, these transcripts are not detectable as proteins and may be regulated through translational repression; a finding we test for a small subset of transcripts and proteins through immunofluorescent microscopy of sporozoites and liver stages in humanized mice. We identify differential transcription between the sporozoite and published transcriptomes of asexual blood-stages and mixed versus hypnozoite-enriched liver stages. These comparisons point to multiple layers of transcriptional, post-transcriptional and post-translational control that appear active in sporozoites and to a lesser extent hypnozoites, but largely absent in replicating liver schizonts or mixed blood-stages. Common transcripts up-regulated in sporozoites and hypnozoites compared to mixed (i.e., schizont) liver-stages identify genes linked to dormancy/persistence in bacteria, amoebae and plants. We also characterise histone epigenetic modifications in the P. vivax sporozoite and explore their role in regulating transcription. Collectively, these data support the hypothesis that the sporozoite as a tightly programmed stage primed to infect the human host and identifies potential mechanisms for hypnozoite-formation that may be further explored in liver stage models.

microbiology↗