Human IgG response to a salivary peptide, gSG6-P1, as a new immuno-epidemiological tool for evaluating low-level exposure to Anopheles bites

International audienceBackground : Human populations exposed to low malaria transmission present particular severe risks of malariamorbidity and mortality. In addition, in a context of low-level exposure to Anopheles vector, conventional entomologicalmethods used for sampling Anopheles populations are insufficiently sensitive and probably under-estimate the real risk ofmalaria transmission. The evaluation of antibody (Ab) responses to arthropod salivary proteins constitutes a novel toolfor estimating exposure level to insect bites. In the case of malaria, a recent study has shown that human IgG responsesto the gSG6-P1 peptide represented a specific biomarker of exposure to Anopheles gambiae bites. The objective of thisstudy was to investigate if this biomarker can be used to estimate low-level exposure of individuals to Anopheles vector.Methods : The IgG Ab level to gSG6-P1 was evaluated at the peak and at the end of the An. gambiae exposure season inchildren living in Senegalese villages, where the Anopheles density was estimated to be very low by classical entomologicaltrapping but where malaria transmission occurred during the studied season.Results : Specific IgG responses to gSG6-P1 were observed in children exposed to very low-level of Anopheles bites. Inaddition, a significant increase in the specific IgG Ab level was observed during the Anopheles exposure season whereasclassical entomological data have reported very few or no Anopheles during the studied period. Furthermore, thisbiomarker may also be applicable to evaluate the heterogeneity of individual exposure.Conclusion : The results strengthen the hypothesis that the evaluation of IgG responses to gSG6-P1 during the seasonof exposure could reflect the real human contact with anthropophilic Anopheles and suggest that this biomarker of lowexposure could be used at the individual level. This promising immuno-epidemiological marker could represent a usefultool to assess the risk to very low exposure to malaria vectors as observed in seasonal, urban, altitude or travellerscontexts. In addition, this biomarker could be used for the surveillance survey after applying anti-vector strategy