Distinct roles of mosquito hemocytes during human pathogens infection

Mosquitoes transmit several infectious diseases such as Malaria and Dengue fever, causing around 1 million deaths and hundreds of millions of cases each year. During the past decades, many mechanisms of immunity and host-pathogen interactions have been revealed in mosquitoes; however, most of this research has been performed using animal models. Hemocytes are the most important cell type of the mosquito immune system since they produce several immune factors that limit the infection by diverse pathogens such as Plasmodium parasites and arbovirus; nevertheless, the role of hemocytes in fighting human pathogens is poorly understood. Here we evaluated the role of hemocytes during the early and late stages of P. falciparum and Dengue virus infection in the mosquitoes Anopheles gambiae and Aedes aegypti respectively. We found that Ae. aegypti hemocytes do not influence dengue virus replication in the midgut, however, they play an antagonist role during dengue virus dissemination from the midgut to other tissues. In contrast, and unexpectedly, we found that An. gambiae hemocytes are agonists of P. falciparum infection in the midgut. Contrary to previous studies using the P. berghei model where hemocytes participate in parasite elimination, our results suggest that hemocytes protect the human malaria parasites. Our work is elucidating new facets of mosquito hemocyte function in infection.