During blood feeding hematophagous arthropods inject into their hosts a cocktail of salivary proteins whose main role is to counteract vertebrate responses to tissue injury, namely hemostasis, inflammation and immunity. However, animal body fluids, including saliva of the few blood sucking arthropods analyzed so far, also carry miRNAs. We recently analyzed the salivary miRNA repertoire of the malaria vector Anopheles coluzzii and found an enrichment of specific miRNAs in saliva as compared to salivary glands. Interestingly, eleven of the most abundant An. coluzzii saliva miRNAs mimicked human endogenous miRNAs targeting host genes involved in immune and inflammatory responses. Overall, these findings raise the intriguing hypothesis that specific miRNAs, perhaps incorporated within exosomes, may be selectively directed toward the secretory pathway and saliva and, injected into vertebrates, may contribute to host manipulation, with potential implications for vector-host interaction and pathogen transmission. To follow-up these initial observations, we plan to characterize salivary exosome-like vesicles and verify whether vector miRNAs can be detected into the host after mosquito blood feeding. Moreover, since anopheline mosquitoes are vectors of Plasmodium parasites, we intend to investigate whether infection by the murine malaria parasite P. berghei modulates Anopheles salivary gland miRNA composition. Finally, we aim to extend our initial observations from Anopheles to Aedes mosquitoes, that are vectors of arboviruses of large relevance for human health. To this end we will perform a small RNA-Seq analysis on both salivary glands and saliva of Aedes aegypti mosquitoes infected and non-infected with the chikungunya virus. We expect the research work proposed here to shed some light on the possible role of mosquito salivary miRNAs in the intricate molecular interactions taking place between mosquitoes, the pathogens they transmit and their vertebrate hosts.
