Insect-specific viruses: infection rates and routes of transmission in Aedes aegypti mosquitoes

Abstract

Insect-specific viruses (ISVs) are viruses that are described to only infect and replicate in insect cells. Viruses such as cell fusing agent virus (CFAV), Phasi Charoen-like virus (PCLV) and Negev virus (NEGV) are ISVs that are often found in wild mosquitoes and have been shown to suppress the replication and transmission of arthropod-borne viruses (arboviruses), like dengue, chikungunya, and Zika viruses. In particular, it has been shown that wild-type and modified negeviruses can suppress, in vitro, the replication of chikungunya virus and Venezuelan equine encephalitis virus. ISVs have been indicated as a potential biological tool for pathogen control because of this ability to inhibit the replication of arboviruses. To be able to use ISVs to decrease the spread of arboviruses, their routes of transmission and infection rates among insects need to be understood. In this thesis, experiments were used to determine if mosquitoes could be infected with ISVs during their larval aquatic life stage and during their adult life stage. The larval stage of Aedes aegypti mosquitoes, a major vector of arboviruses, was exposed to cell cultures co-infected with CFAV, PCLV and NEGV, as well as to cell cultures infected with NEGV alone. Our results indicate that NEGV can be horizontally transmitted to the mosquitoes during their aquatic stage of development during coinfections with other ISVs and when alone. Next adult mosquitoes were exposed to NEGV through sugar meals that were spiked with NEGV. This method also resulted in successful infection, which was followed by the confirmation of vertical transmission, from the infected parents to their offspring, as well. These experiments revealed desirable characteristics for ISVs that can be used as biological control agents and makes NEGV a potential candidate to combat mosquito- borne pathogens.