Résumé
Human populations living in areas endemic for malaria develop protective immunity which is predominantly mediated by antibodies against Plasmodium falciparum. This immunity can be modulated by various factors relating to the host, the parasite and the environment. The human populations are frequently exposed to bites from blood-feeding insects, in particular to the different species of Anopheles, Culex and Aedes mosquitoes. Certain salivary components, contained in the saliva injected into the host at each blood meal, have immunomodulatory properties, and are therefore able to modulate the host's immune system. This work is interested in host-vector-pathogen immunological relationships and our objective was to assess the influence of exposure to mosquito bites on antibody responses specific to Plasmodium falciparum in human populations residing in endemic areas for malaria.Blood samples taken during two multidisciplinary studies carried out in Bouaké (Côte d'Ivoire) were used to assess the IgG and isotypic responses (IgG1 and IgG3) to certain candidate vaccine antigens (PfAMA1, PfMSP1, PfMSP3 and PfGLURP-R0) and extracts of schizonts (Pfshz) of Plasmodium falciparum. Exposure to mosquito bites was defined at the individual level by a serological approach based on the quantification of the IgG response to certain salivary antigens specific to each mosquito genus and which represent a proxy for the level of exposure to these mosquitoes. The relationship between antibody responses to P. falciparum antigens and demographic, parasitic, and environmental factors has been determined through the use of univariate and multivariate analyzes.In the first cross-sectional study, the anti-Plasmodium falciparum antibody responses were different depending on the level of exposure of the children, those highly exposed to Anopheles had significantly lower IgG and IgG3 responses to PfMSP1. We did not find an association between antibody responses to PfAMA1 and the level of exposure to Anopheles. In the second study, we followed the evolution of the anti-P. falciparum IgG response up to 42 days after infection. People who were more exposed to Anopheles or Aedes bites (considering exposure at single genus exposure) had a greater increase in the anti-PfShz IgG response compared to less exposed people. A positive association between the IgG response to PfShz and the individual level of exposure to the two genera of mosquitoes combined was also observed during follow-up. The evolution of the immune response was also associated with age, parasite density and pre-existing anti-Plasmodium immune response at inclusion. Mosquito exposure (single or combined) did not appear to influence the dynamics of evolution of specific responses to merozoite Ags.Taken together, these results suggest that exposure to mosquito bites, and their immunomodulatory components are associated to the acquisition and dynamic of antibody responses directed against certain Plasmodium falciparum antigens. These “field” observations can be the starting point for further work to further explore the role of mosquito saliva on malaria transmission by combining field and ex-vivo immunological studies.