[Show abstract][Hide abstract] ABSTRACT: Wolbachia as an endosymbiont is widespread in insects and other arthropods and is best known for reproductive manipulations of the host. Recently, it has been shown that wMelpop and wMel strains of Wolbachia inhibit replication of several RNA viruses, including Dengue virus, and other vector-borne pathogens (e.g. Plasmodium and filarial nematodes) in mosquitoes providing an alternative approach to limit transmission of vector-borne pathogens. In this study, we tested the effect of Wolbachia on the replication of West Nile Virus (WNV). Surprisingly, accumulation of the genomic RNA of WNV for all the three strains of WNV tested (New York 99, Kunjin and New South Wales) was enhanced in Wolbachia-infected Aedes aegypti cells (Aag2). However, the amount of secreted virus was significantly reduced in the presence of Wolbachia. Intrathoracic injections showed that replication of WNV in A. aegypti mosquitoes infected with wMel strain of Wolbachia was not inhibited; while wMelPop strain of Wolbachia significantly reduced replication of WNV in mosquitoes. Further, when wMelPop mosquitoes were orally inoculated with WNV, virus infection, transmission and dissemination rates were very low in Wolbachia-free mosquitoes and these were completely inhibited in the presence of Wolbachia. The results suggest that (i) despite enhancement of viral genomic RNA replication in the Wolbachia-infected cell line, production of secreted virus was significantly inhibited, (ii) the anti-viral effect in intrathoracically-infected mosquitoes depends on the strain of Wolbachia, and (iii) replication of the virus in orally infected mosquitoes was completely inhibited in wMelPop strain of Wolbachia.
[Show abstract][Hide abstract] ABSTRACT: Wolbachia are maternally inherited intracellular bacterial symbionts that are estimated to infect more than 60% of all insect species. While Wolbachia is commonly found in many mosquitoes it is absent from the species that are considered to be of major importance for the transmission of human pathogens. The successful introduction of a life-shortening strain of Wolbachia into the dengue vector Aedes aegypti that halves adult lifespan has recently been reported. Here we show that this same Wolbachia infection also directly inhibits the ability of a range of pathogens to infect this mosquito species. The effect is Wolbachia strain specific and relates to Wolbachia priming of the mosquito innate immune system and potentially competition for limiting cellular resources required for pathogen replication. We suggest that this Wolbachia-mediated pathogen interference may work synergistically with the life-shortening strategy proposed previously to provide a powerful approach for the control of insect transmitted diseases.