Proteogenomic analysis of Anopheles gambiae phagocytic hemocyte populations reveals an anticipatory innate immune response in the absence of pathogen challenge

The innate immune response to a broad class of pathogens is highly conserved across all eukaryotes and has been studied in great detail at the cellular and transcriptomic level in several insect species. However, the commensurate cellular proteomic response, especially of hemocytes, the primary immune cell population in insects, has remained poorly understood. We report on the comprehensive proteogenomic analysis of a phagocyte subpopulation from Anopheles gambiae, the primary malaria mosquito vector in Sub-Saharan Africa. We leveraged the innate phagocytic response of mosquito granulocytes to achieve targeted enrichment for these cells to facilitate the examination of their proteomic response profiles following sugar feeding, as well as non-infectious and infectious blood feeding with Plasmodium falciparum. A comparative integrative-OMICs analysis of existing transcriptomic profiles combined with these proteomic data permitted the delineation of the functional genome of anopheline granulocytes. We observed that phagocytosis, blood feeding, and P. falciparum infection induced dramatic shifts in granulocyte protein expression indicative of broad changes in cellular proliferation and innate immune response priming. Importantly, we identified a large number of hemocyte immune proteins that respond to blood feeding alone, suggesting that granulocytes may play an integral role in an anticipatory immune response prior to immune challenge.