Screening for differentially expressed miRNAs in Aedes albopictus (Diptera: Culicidae) exposed to DENV-2 and their effect on replication of DENV-2 in C6/36 cells.

Background: The mosquito Aedes albopictus is an important vector for dengue virus (DENV) transmission. The midgut is the first barrier to mosquito infection by DENV, and this barrier is a critical factor affecting the vector competence of the mosquito. However, the molecular mechanism of the interaction between midgut and virus is unknown.

Results: Six small libraries of Ae. albopictus midgut RNAs were constructed, three of which from mosquitoes that were infected with DENV-2 after feeding on infected blood, and another three that remained uninfected with DENV-2 after feeding on same batch of infected blood. A total of 46 differentially expressed miRNAs were identified of which 17 significant differentially expressed miRNAs were selected. Compared to microRNA expression profiles of mosquitoes that were uninfected with DENV-2, 15 microRNAs were upregulated and two were downregulated in mosquitoes that were infected with DENV-2. Among these differentially expressed microRNAs, miR-1767, miR-276-3p, miR-4448 and miR-622 were verified by stem-loop qRT-PCR in samples from seven-day-infected and uninfected midguts and chosen for an in vitro transient transfection assay. miR-1767 and miR-276-3p enhanced dengue virus replication in C6/36 cells, and miR-4448 reduced dengue virus replication.

Conclusions: To our knowledge, this study is the first to reveal differences in expression levels between mosquitoes infected and uninfected with DENV-2 after feeding on an infected blood meal. It provides useful information on microRNAs expressed in the midgut of Aedes albopictus after exposure to the virus.