What will studies of Fulani individuals naturally exposed to malaria teach us about protective immunity to malaria?

Single-cell transcriptomics reveals inter-ethnic variation in immune response to Falciparum malaria

Africa's environmental, cultural, and genetic diversity can profoundly shape population responses to infectious diseases, including malaria caused by Plasmodium falciparum. Differences in malaria susceptibility among populations are documented, but the underlying mechanisms remain poorly understood. Notably, the Fulani ethnic group in Africa is less susceptible to malaria compared to other sympatric groups, such as the Mossi. They exhibit lower disease rates and parasite load as well as enhanced serological protection. However, elucidating the molecular and cellular basis of this protection has been challenging in part due to limited immunological characterization at the cellular level. To address this question, we performed single-cell transcriptomic profiling of peripheral blood mononuclear cells from 126 infected and non-infected Fulani and Mossi children in rural Burkina Faso. This analysis generated over 70,000 single-cell transcriptomes and identified 30 distinct cell subtypes. We report a profound effect of ethnicity on the transcriptional landscape, particularly within monocyte populations. Differential expression analysis across cell subtypes revealed ethnic-specific immune signatures under both infected and non-infected states. Specifically, monocytes and T cell subtypes of the Fulani exhibited reduced pro-inflammatory responses, while their B cell subtypes displayed stronger activation and inflammatory profiles. Furthermore, single-cell expression quantitative trait locus (eQTL) analysis in monocytes of infected children revealed several significant regulatory variants with ethnicity-specific effects on immune-related genes, including CD36 and MT2A. Overall, we identify ethnic, cell-type-specific, and genetic regulatory effects on host immune responses to malaria and provide valuable single-cell eQTL and transcriptomic datasets from under-represented populations.

The impact of interethnic lipidomic variation in falciparum malaria

BACKGROUND

Shifts in dietary patterns during lifestyle transitions are integral components of the dynamic interactions between humans and their environments. Investigating the link between dietary diversity, the composition of the human lipidome and infection is key to understanding the interplay between diet and susceptibility to pathogens.

METHODS

Here we address this question by performing a comparative study of two ethnic groups with divergent dietary patterns: Fulani, who are nomad pastoralists with a dairy-centric diet, and Mossi, who are farmers with a plant-based diet. We generate 196 paired global lipidomes (927 lipid molecules) from both groups before and during natural Plasmodium falciparum infection.

RESULTS

Our analysis revealed 211 significantly differentially abundant lipid molecules between the two ethnic groups in both infection states. We show that ethnicity has a greater impact on the lipidome of these children than do P. falciparum infection and report inter-ethnic differences that impact pathogenesis. We highlight elevated levels of pentadecanoic acid (C15:0)-containing phospholipids in Fulani and experimentally demonstrate the suppressive effects of lysophosphatidylcholine LysoPC (15:0) on P. falciparum gametocyte production.

CONCLUSION

These findings link the Fulani's dairy-centric diet and lower P. falciparum gametocyte densities reported in this group and underscore the intricate links between dietary lipids and the host response to infection.

The dichotomy between probiotic lactic acid bacteria and Plasmodium: A promising therapeutic avenue

Our understanding of gut microbial populations and their immense influence on host immunity, health, and diseases has increased deeply in recent years. Numerous reports have identified the role of mosquito and mammalian gut microbiota in the modulation of host susceptibility to Plasmodium infection. Artemisinin resistance in malaria-endemic regions necessitates the development of new, safer, and more affordable treatments to supplement existing therapies. In this review, we compiled a colossal amount of data from numerous studies that have assessed the roles played by gut microbial communities in Plasmodium infection, progression, transmission, and severity. Most interestingly, our study points to the overwhelming evidence from experimental studies in mural malaria to human trials, suggesting that the presence of lactic acid bacteria in the gut microbiota of mammalian hosts provides a great degree of protection against malaria. Therefore, our study provides a compelling narrative for probiotic administration as an adjunct therapy for combatting malaria.

Exploiting integrative metabolomics to study host-parasite interactions in Plasmodium infections

Despite years of research, malaria remains a significant global health burden, with poor diagnostic tests and increasing antimalarial drug resistance challenging diagnosis and treatment. While 'single-omics'-based approaches have been instrumental in gaining insight into the biology and pathogenicity of the Plasmodium parasite and its interaction with the human host, a more comprehensive understanding of malaria pathogenesis can be achieved through 'multi-omics' approaches. Integrative methods, which combine metabolomics, lipidomics, transcriptomics, and genomics datasets, offer a holistic systems biology approach to studying malaria. This review highlights recent advances, future directions, and challenges involved in using integrative metabolomics approaches to interrogate the interactions between Plasmodium and the human host, paving the way towards targeted antimalaria therapeutics and control intervention methods.

ATP2B4 regulatory genetic variants are associated with mild malaria

BACKGROUND

Genome-wide association studies have identified ATP2B4 as a severe malaria resistance gene. Recently, 8 potential causal regulatory variants have been shown to be associated with severe malaria.

METHODS

Genotyping of rs10900585, rs11240734, rs1541252, rs1541253, rs1541254, rs1541255, rs10751450, rs10751451 and rs10751452 was performed in 154 unrelated individuals (79 controls and 75 mild malaria patients). rs10751450, rs10751451 and rs10751452 were genotyped by Taqman assays, whereas the fragment of the ATP2B4 gene containing the remaining SNPs was sequenced. Logistic regression analysis was used to assess the association between the SNPs and mild malaria.

RESULTS

The results showed that mild malaria was associated with rs10900585, rs11240734, rs1541252, rs1541253, rs1541254, rs1541255, rs10751450, rs10751451 and rs10751452. The homozygous genotypes for the major alleles were associated with an increased risk of mild malaria. Furthermore, the haplotype containing the major alleles and that containing the minor alleles were the most frequent haplotypes. Individuals with the major haplotypes had a significantly higher risk of mild malaria compared to the carriers of the minor allele haplotype.

CONCLUSIONS

ATP2B4 polymorphisms that have been associated with severe malaria are also associated with mild malaria.

Susceptibility to malaria in fulani, Bariba, Otamari and gando individuals living in sympatry in Benin: Role of opsonizing antibodies to Plasmodium falciparum merozoites

Objectives

Fulani in Africa are known to be less susceptible to Plasmodium falciparum (Pf) malaria. This study explored a potential involvement of antibody-mediated merozoite phagocytosis mechanism in this natural protection against malaria.

Methods

Before the start of the malaria transmission season (MTS) in Benin, the functionality of antibodies against Pf merozoites was determined by the opsonic phagocytosis (OP) assay in plasma samples from Fulani, Bariba, Otamari and Gando groups. These individuals were actively followed-up for malaria detection from the beginning to the end of MTS. Anti-GLURP Immunoglobulin G antibody quantification, malaria Rapid Diagnostic Test (RDT) and spleen palpation were performed before and after MTS.

Results

In Bariba, Otamari and Gando, but not in Fulani, plasma from adults promoted higher levels of OP than the children (P = 0.003; P = 0.012; P = 0.031 and P = 0.122). A high proportion of Fulani children had higher OP and anti-GLURP (P < 0.0001) antibody levels as compared to non-Fulani children; whereas this was not observed for Fulani adults (P = 0.223). High OP levels before MTS were significantly related to negative RDT after MTS (P = 0.011).

Conclusion

Our results highlight the ability of opsonizing antibodies to potentially enhance natural protection of young Fulani individuals against Pf malaria in Benin.

Mouse Models for Unravelling Immunology of Blood Stage Malaria

Malaria comprises a spectrum of disease syndromes and the immune system is a major participant in malarial disease. This is particularly true in relation to the immune responses elicited against blood stages of Plasmodium-parasites that are responsible for the pathogenesis of infection. Mouse models of malaria are commonly used to dissect the immune mechanisms underlying disease. While no single mouse model of Plasmodium infection completely recapitulates all the features of malaria in humans, collectively the existing models are invaluable for defining the events that lead to the immunopathogenesis of malaria. Here we review the different mouse models of Plasmodium infection that are available, and highlight some of the main contributions these models have made with regards to identifying immune mechanisms of parasite control and the immunopathogenesis of malaria.

What will studies of Fulani individuals naturally exposed to malaria teach us about protective immunity to malaria?

There are an estimated over 200 million yearly cases of malaria worldwide. Despite concerted international effort to combat the disease, it still causes approximately half a million deaths every year, the majority of which are young children with Plasmodium falciparum infection in sub‐Saharan Africa. Successes are largely attributed to malaria prevention strategies, such as insecticide‐treated mosquito nets and indoor spraying, as well as improved access to existing treatments. One important hurdle to new approaches for the treatment and prevention of malaria is our limited understanding of the biology of Plasmodium infection and its complex interaction with the immune system of its human host. Therefore, the elimination of malaria in Africa not only relies on existing tools to reduce malaria burden, but also requires fundamental research to develop innovative approaches. Here, we summarize our discoveries from investigations of ethnic groups of West Africa who have different susceptibility to malaria.