The bacterium Wolbachia exploits host innate immunity to establish a symbiotic relationship with the dengue vector mosquito Aedes aegypti

Abstract

A host’s immune system plays a central role in shaping the composition of the microbiota and, in return, resident microbes influence immune responses. Symbiotic associations of the maternally transmitted bacterium Wolbachia occur with a wide range of arthropods. It is, however, absent from the dengue and Zika vector mosquito Aedes aegypti in nature. When Wolbachia is artificially forced to form symbiosis with this new mosquito host, it boosts the basal immune response and enhances the mosquito’s resistance to pathogens, including dengue, Zika virus and malaria parasites. The mechanisms involved in establishing a symbiotic relationship between Wolbachia and A. aegypti, and the long-term outcomes of this interaction, are not well understood. Here, we have demonstrated that both the immune deficiency (IMD) and Toll pathways are activated by the Wolbachia strain wAlbB upon its introduction into A. aegypti. Silencing the Toll and IMD pathways via RNA interference reduces the wAlbB load. Notably, wAlbB induces peptidoglycan recognition protein (PGRP)-LE expression in the carcass of A. aegypti, and its silencing results in a reduction of symbiont load. Using transgenic mosquitoes with stage-specific induction of the IMD and Toll pathways, we have shown that elevated wAlbB infection in these mosquitoes is maintained via maternal transmission. These results indicate that host innate immunity is utilized to establish and promote host-microbial symbiosis. Our results will facilitate a long-term projection of the stability of the Wolbachia–A. aegypti mosquito system that is being developed to control dengue and Zika virus transmission to humans.

Wolbachia pipientis occurs in Aedes aegypti populations in New Mexico and Florida, USA

“…aegypti population was not investigated in that study (Coon et al, 2016). Interestingly, the Toll and IMD pathways favor establishment and maintenance of wAlbB infection in the line; the knockdown of Toll and IMD by RNA interference reduces the wAlbB load, while the transgenic activation of Toll and IMD increases the load (Pan et al, 2018). aegypti, respectively, collected in the suburb and urban areas of Thailand (Thongsripong et al, 2017).…”

“…aegypti to form a line with inherited infection (Xi, Khoo, & Dobson, 2005). Interestingly, the Toll and IMD pathways favor establishment and maintenance of wAlbB infection in the line; the knockdown of Toll and IMD by RNA interference reduces the wAlbB load, while the transgenic activation of Toll and IMD increases the load (Pan et al, 2018). It appears that transinfected Wolbachia can exploit host immunity for a symbiotic association.…”

Wolbachia pipientisoccurs inAedes aegyptipopulations in New Mexico and Florida, USA

“…aegypti to form a line with inherited infection (Xi, Khoo, & Dobson, 2005). Interestingly, the Toll and IMD pathways favor establishment and maintenance of w AlbB infection in the line; the knockdown of Toll and IMD by RNA interference reduces the w AlbB load, while the transgenic activation of Toll and IMD increases the load (Pan et al, 2018). It appears that transinfected Wolbachia can exploit host immunity for a symbiotic association.…”

Complete Genome Sequence of the Wolbachia wAlbB Endosymbiont of Aedes albopictus

“…It is a significant public health concern as it is a competent vector of several arboviruses that 92 cause severe diseases in humans such as dengue, chikungunya and zika (Gratz 2004 whereas it blocks transmission of dengue (Mousson et al 2012) and chikungunya (Raquin et al 101 2015). The interplay between wAlbB and its host is also particularly important as it impacts the 102 stability of wAlbB following its introduction into new hosts such as Aedes aegypti mosquitoes to 103 control dengue and zika transmission to humans (Pan et al 2018). 1997).…”