Sindbis virus induces transport processes and alters expression of innate immunity pathway genes in the midgut of the disease vector, Aedes aegypti.

The midgut of hematophagous insects is the initial site of infection by arthropod-borne viruses (arboviruses) and plays a crucial role in vector competence. To further understand processes that occur in the midgut in response to infection by an arbovirus, DNA microarrays were used to analyze gene expression changes following infection by the alphavirus, Sindbis (MRE16 Malaysian strain). Midgut transcription profiles from mosquitoes fed blood containing 10(8)pfu/ml of virus were compared with those from mosquitoes ingesting blood meals having no virus. Transcription profiles from both experimental groups were analyzed at 1, 4, and 8 days post-feeding. Among the many transcription changes observed by microarray analysis, the most dramatic involved three genes that had 25-40-fold increases in transcript levels in virus infected mosquitoes at 4 days post-infection. These genes were synaptic vesicle protein-2 (SV2), potassium-dependent sodium/calcium exchanger (NCKX), and a homologue of Caenorhabditis elegans Unc-93, a putative component of a two-pore potassium channel. We speculate that these changes represent changes in vesicle transport processes. In addition to these observations, transcript changes were observed in infected mosquitoes that suggested involvement of Toll and c-jun amino terminal kinase immune cascades as a response to viral infection.