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West Nile virus (WNV) is the leading cause of mosquito-borne illness in the USA. There are currently no human vaccines or therapies available for WNV, and vector control is the primary strategy used to control WNV transmission. The WNV vectorCulex tarsalisis also a competent host for the insect-specific virus (ISV) Eilat virus (EILV). ISVs such as EILV can interact with and cause superinfection exclusion (SIE) against human pathogenic viruses in their shared mosquito host, altering vector competence for these pathogenic viruses. The ability to cause SIE and their host restriction make ISVs a potentially safe tool to target mosquito-borne pathogenic viruses. In the present study, we tested whether EILV causes SIE against WNV in mosquito C6/36 cells andC. tarsalismosquitoes. The titres of both WNV strains – WN02-1956 and NY99 – were suppressed by EILV in C6/36 cells as early as 48–72 h post-superinfection at both m.o.i. values tested in our study. The titres of WN02-1956 at both m.o.i. values remained suppressed in C6/36 cells, whereas those of NY99 showed some recovery towards the final timepoint. The mechanism of SIE remains unknown, but EILV was found to interfere with NY99 attachment in C6/36 cells, potentially contributing to the suppression of NY99 titres. However, EILV had no effect on the attachment of WN02-1956 or internalization of either WNV strain under superinfection conditions. InC. tarsalis, EILV did not affect the infection rate of either WNV strain at either timepoint. However, in mosquitoes,EILV enhanced NY99 infection titres at 3 days post-superinfection, but this effect disappeared at 7 days post-superinfection. In contrast, WN02-1956 infection titres were suppressed by EILV at 7 days post-superinfection. The dissemination and transmission of both WNV strains were not affected by superinfection with EILV at either timepoint. Overall, EILV caused SIE against both WNV strains in C6/36 cells; however, inC. tarsalis, SIE caused by EILV was strain specific potentially owing to differences in the rate of depletion of shared resources by the individual WNV strains.
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Alpha‐mannosidase‐2 modulates arbovirus infection in a pathogen‐ and Wolbachia ‐specific manner in Aedes aegypti mosquitoes
Abstract MultipleWolbachiastrains can block pathogen infection, replication and/or transmission inAedes aegyptimosquitoes under both laboratory and field conditions. However,Wolbachiaeffects on pathogens can be highly variable across systems and the factors governing this variability are not well understood. It is increasingly clear that the mosquito host is not a passive player in whichWolbachiagoverns pathogen transmission phenotypes; rather, the genetics of the host can significantly modulateWolbachia‐mediated pathogen blocking. Specifically, previous work linked variation inWolbachiapathogen blocking to polymorphisms in the mosquito alpha‐mannosidase‐2 (αMan2) gene. Here we use CRISPR‐Cas9 mutagenesis to functionally test this association. We developed αMan2 knockouts and examined effects on bothWolbachiaand virus levels, using dengue virus (DENV;Flaviviridae) and Mayaro virus (MAYV;Togaviridae).Wolbachiatitres were significantly elevated in αMan2 knockout (KO) mosquitoes, but there were complex interactions with virus infection and replication. InWolbachia‐uninfected mosquitoes, the αMan2 KO mutation was associated with decreased DENV titres, but in aWolbachia‐infected background, the αMan2 KO mutation significantly increased virus titres. In contrast, the αMan2 KO mutation significantly increased MAYV replication inWolbachia‐uninfected mosquitoes and did not affectWolbachia‐mediated virus blocking. These results demonstrate that αMan2 modulates arbovirus infection inA. aegyptimosquitoes in a pathogen‐ andWolbachia‐specific manner, and thatWolbachia‐mediated pathogen blocking is a complex phenotype dependent on the mosquito host genotype and the pathogen. These results have a significant impact for the design and use ofWolbachia‐based strategies to control vector‐borne pathogens.
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- Award ID(s):
- 1645331
- PAR ID:
- 10521983
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Insect Molecular Biology
- Volume:
- 33
- Issue:
- 4
- ISSN:
- 0962-1075
- Format(s):
- Medium: X Size: p. 362-371
- Size(s):
- p. 362-371
- Sponsoring Org:
- National Science Foundation
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