Vav proteins do not influence dengue virus replication but are associated with induction of phospho-ERK, IL-6, and viperin mRNA following DENV infection in vitro

Vav proteins are guanine exchange factors that activate Rac1/RhoA signaling to regulate many biological processes including inflammatory responses. Here, the expression and functional significance of Vav's were investigated during dengue virus (DENV) infection. In primary monocyte-derived macrophages, Vav1, -2, and -3 mRNA levels demonstrate variable responses to DENV infection and correlate with DENV-induced host inflammatory (IL-6 and TNF-alpha), antiviral (viperin), or cell adhesion [intercellular cell adhesion molecule (ICAM-1)] mRNA induction. Strong positive correlations were seen in particular for Vav2 with TNF-alpha and Vav3 with IL-6 mRNA. In the retinal pigmented epithelial cell line, ARPE-19, Vav2 was the main Vav expressed and was not affected by DENV infection. Heterologous Vav1 expression in ARPE-19 cells induced an increase in basal IL-6 mRNA but did not enhance DENV-induced mRNA responses. DENV RNA and DENV-induced viperin and IL-6 mRNA responses were also unaffected by Vav2 siRNA knockdown. Treatment of DENV-infected ARPE-19 cells with EHop-016 to block Vav signaling did not affect DENV RNA levels but increased DENV-mediated induction of IL-6 mRNA. More detailed assessment of DENV-induced responses to azathioprine, a clinically used immunosuppressant that can also block Vav signaling and act as a nucleoside analog, similarly demonstrated no change in DENV RNA levels but resulted in inhibition of DENV-induced phospho-ERK and increased DENV-induced-IL-6 and viperin mRNA in ARPE-19 cells. Thus, levels of Vav are associated with DENV-induced inflammatory responses, and blocking Vav signaling pathways does not compromise control of viral replication but may influence DENV-induced host responses.