Mosquito host background impacts microbiome-Zika virus interactions in field- and laboratory-reared Aedes aegypti.

Mosquito microbiota abundance and composition are modulated by a variety of factors, including pathogen exposure. The microbiome can also influence pathogen infection of the host and thus harbours considerable potential to impact transmission of pathogens. As such, there is a growing interest in using particular bacterial members of the microbiota for novel vector-control strategies. However, before novel microbiota-based approaches can move towards translation, a more complete understanding of the interactions between mosquitoes, their microbiome, and the pathogens they transmit, is required to better appreciate how variation in the microbiome of field mosquitoes affects these interactions. To examine the impact of the mosquito background and the associated diversity of bacterial microbiota within distinct hosts, we exposed several laboratory-reared and field-collected Aedes aegypti mosquito lines to Zika virus (ZIKV) and examined their bacterial load and composition in response to pathogen exposure and viral infection success. Intriguingly, we show that ZIKV exposure and infection had distinct impacts on microbiome composition and density within different mosquito lines. In one laboratory-reared line ZIKV exposure and infection reduced the bacterial load, while conversely in another line load was increased by the virus. Distinct responses of the microbiome were also seen in mosquitoes collected from the field. Sampling site-specific differences in the microbiome of mosquitoes were observed as virus infection altered microbiome alpha and beta diversities in one cohort, while in mosquitoes from other sampling sites, viral progression through the mosquito had minimal effect on the microbiome. We also identified bacterial taxa correlating with either ZIKV infection or a lack of infection. These taxa are potential candidates for future follow-up studies disentangling functional mechanisms and directionality of interactions. Overall, our study highlights that interactions between mosquito, virus, and microbiota are variable and context dependent, and that tripartite interactions among distinct mosquito cohorts and their microbiomes are not universal.