Bacteria and antiviral immunity in insects

• Bacteria isolated from mosquitoes modulate virus infection, including dengue and La Crosse virus.
• Wolbachia mediates antiviral protection in both mosquitoes and Drosophila.
• Interactions between bacteria and viruses may impact natural insect populations.
• Interactions between bacteria and arboviruses may be exploited to reduce insect vectored viruses of humans.

Tripartite interactions between viruses, bacteria and hosts can have significant implications for the outcome of infections. In insects recent studies have shown that these interactions can greatly influence the transmission of vector borne disease, including transmission of dengue virus. Mosquito gut bacteria modulate arbovirus infection of the mosquito host and specific bacterial isolates have been identified that negatively impact the outcome of infection. In addition, an endosymbiotic bacterium Wolbachia, which is very common in insects, protects flies and mosquitoes from virus infection. This antiviral protection has implications for both naturally infected insects and for use in disease control. This review summarises the current state of knowledge for each of these interactions with an emphasis on natural interactions.