First-in-human evaluation of cutaneous innate and adaptive immunomodulation by mosquito bites

Mosquito-borne viruses are a growing global threat. Initial viral inoculation occurs in the skin via the mosquito bite, eliciting immune responses that shape the establishment of infection and pathogenesis. We aimed to cutaneous innate and adaptive immune responses to mosquito bites in individuals from endemic areas. In this single-arm, cross-sectional interventional study, we enrolled 30 healthy adult participants aged 18 to 45 years of age from Cambodia between October 2020 and January 2021. We performed 3-mm skin biopsies at baseline as well as 30 minutes, 4 hours, and 48 hours after a controlled feeding by uninfected Aedes aegypti mosquitos. The primary endpoints were measurement of changes in early and late innate responses in bitten vs unbitten skin by gene expression profiling, immunophenotyping, and cytokine profiling. Results revealed induction of neutrophil degranulation and recruitment of skin-resident dendritic cells and M2-macrophages in bitten skin. As the immune reaction progressed over time, T cell priming and regulatory pathways were upregulated along with a shift to a Th2-driven response and CD8+ T cell activation. In accordance, participants bitten skin cells produced less pro-inflammatory cytokines when stimulated by Ae. aegypti salivary gland extract. No unexpected adverse events occurred, and one patient was lost to follow-up at Day 14. These results identify key immune genes, cell types, and pathways in the human response to mosquito bites that can be leveraged to develop novel therapeutics and vector-targeted vaccine candidates to arboviral diseases. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=132 SRC="FIGDIR/small/489145v2_ufig1.gif" ALT="Figure 1"> View larger version (77K): org.highwire.dtl.DTLVardef@1ba2eaaorg.highwire.dtl.DTLVardef@4d9dd6org.highwire.dtl.DTLVardef@1b54dc8org.highwire.dtl.DTLVardef@5a104_HPS_FORMAT_FIGEXP M_FIG Panel shows evolution of the human skin response to Aedes aegypti bites over time. C_FIG