The dengue virus NS1 protein alters Aedes aegypti midgut permeability and favors virus dissemination

The dengue virus is an arbovirus of public health importance transmitted by Aedes aegypti mosquitoes. The NS1 protein is a multifunctional glycoprotein, highly conserved among Orthoflaviviruses, that is secreted from infected cells, circulate in the sera of dengue patients at high concentrations and has been involved with pathogenesis by several mechanisms, including vascular leakage and immune evasion. However, the role of NS1 within the mosquito vector is not fully understood. In this study, we observed that feeding female Aedes aegypti mosquitoes with blood meals supplemented with recombinant NS1 resulted in increased midgut permeability, as evaluated by the diffusion of the non-toxic dye Brilliant Blue FCF into the hemocoel. Histological and transmission electron microscopy analysis revealed epithelial damage and disruption of the midgut cellular junctions. Immunofluorescence assays further demonstrated the delocalization of septate junction proteins essential for epithelial integrity. In addition, metalloproteinase expression in the midgut was also reduced. All these effects were abolished when NS1 was heat-inactivated indicating that they were NS1-dependent. Significantly, virus blood meals containing NS1 resulted in enhanced dissemination of DENV to secondary organs and earlier virus presence in the mosquito salivary glands, in comparison with meals treated with specific NS1 antibodies. Our findings reveal a novel function for NS1 in mosquitoes, and expand the understanding of NS1 functions beyond its human pathophysiological role. In addition, highlight NS1 as a strategic intervention point to reduce transmission efficiency in mosquitoes.