Assessing Aedes aegypti candidate genes during viral infection and Wolbachia-mediated pathogen blocking

The symbiont <i>Wolbachia</i> limits viral replication in <i>Aedes aegypti</i> and significantly reduces dengue fever incidence in humans following field release. Despite plans for its widespread use, <i>Wolbachia</i>’s mode of action remains poorly understood. Many studies suggest that the mechanism of viral blocking is likely multifaceted, involving aspects of immunity, cellular stress, and nutritional competition. A previous study from our group used artificial selection to identify a new mosquito candidate gene related to viral blocking; <i>alpha-mannosidase-2a</i> (<i>alpha-Mann-2a</i>) with a predicted role in protein glycosylation. Protein glycosylation pathways tend to be involved in complex host-viral interactions; however, the function of alpha-mannosidases has not been described in mosquito-virus interactions. We examined the expression of <i>alpha-Mann-2a</i> in response to virus and <i>Wolbachia</i> infections and whether reduced gene expression, caused by RNA interference (RNAi), affected viral loads. We show that dengue virus (DENV) infection affects the expression of <i>alpha-Mann-2a </i>in a tissue and time dependent manner, whereas <i>Wolbachia</i> infection had no effect. In the midgut, DENV prevalence increased following knockdown of <i>alpha-Mann-2a</i> expression in <i>Wolbachia</i>-free mosquitoes, suggesting that <i>alpha-Mann-2a</i> interferes with infection. Expression knockdown had the same effect on the Togavirus chikungunya (CHIKV), indicating that <i>alpha-Mann-2a</i> may have broad antivirus effects in the midgut. Interestingly, we were unable to knockdown the expression in <i>Wolbachia</i>-infected mosquitoes. We also provide evidence that <i>alpha-Mann-2a</i> may affect the transcriptional level of another gene predicted to be involved in viral blocking and cell adhesion; <i>cadherin87a</i>. These data support the hypothesis that glycosylation and adhesion pathways may broadly be involved in viral infection in <i>Ae. aegypti.</i>