The Effects of Midgut Serine Proteases on Dengue Virus Type 2 Infectivity of Aedes aegypti

Abstract

Dengue viruses (DENV) cause significant morbidity and mortality worldwide and are transmitted by the mosquito Aedes aegypti. Mosquitoes become infected after ingesting a viremic bloodmeal, and molecular mechanisms involved in bloodmeal digestion may affect the ability of DENV to infect the midgut. We used RNA interference (RNAi) to silence expression of four midgut serine proteases and assessed the effect of each RNAi phenotype on DENV-2 infectivity of Aedes aegypti. Silencing resulted in significant reductions in protease mRNA levels and correlated with a reduction in activity except in the case of late trypsin. RNA silencing of chymotrypsin, early and late trypsin had no effect on DENV-2 infectivity. However, silencing of 5G1 or the addition of soybean trypsin inhibitor to the infectious bloodmeals significantly increased midgut infection rates. These results suggest that some midgut serine proteases may actually limit DENV-2 infectivity of Ae. aegypti.

West Nile Virus: Biology, Transmission, and Human Infection

“…Genes involved in transcription and ion binding were found to be downregulated, and genes coding for proteases and cuticle proteins were found to be upregulated, during infection with all three viruses (42). Serine proteases had previously been shown to be important for viral propagation and blood digestion, though there have been varying reports regarding their impact on flaviviral infection in the mosquito (22,138). Another global study of flaviviral infection in Drosophila identified many insect host factors relevant during dengue virus infection of the mosquito, including a putative NADH dehydrogenase and proteins involved in vesicular transport and endocytosis (193).…”

Influence of mosquito genotype on transcriptional response to dengue virus infection

“…Moreover, several genes related to serine protease (AAEL011622), innate immunity (AAEL007642), apoptosis (AAEL012143) and proteolytic activities (AAEL011016 and AAEL005112) were activated in the Moyo-D strain but not in the D2S3 strain, suggesting a possible role of these genes in defense response to DENV in A. aegypti . Proteases, Toll pathway genes and apoptosis inducing genes have been indicated to regulate dengue susceptibility in A. aegypti from previous studies (Molina-Cruz et al 2005, Brackney et al 2008, Xi et al 2008, Behura et al 2011, Liu et al 2013). …”

“…2008). The innate immunity of the mosquito plays the key role in defending against DENV infection which is likely to be orchestrated by multiple factors including apoptotic and proteolytic processes (Brackney et al 2008, Liu et al 2013). …”

“…A candidate protein of A. aegypti has also been identified that binds to dengue virus and contributes to dengue infectivity in the mosquito (Mercado-Curiel et al 2008). Differential expression of mid-gut serine protease and trypsin genes have also been suggested as having role in DENV-2 infectivity in A. aegypti (Molina-Cruz et al 2005, Brackney et al 2008). However, the potential for differential response of these genes or pathways to DENV infection in refractory versus susceptible mosquito genotypes is unclear.…”

Transcriptome Analysis of the Midgut of the Chinese Oak Silkworm Antheraea pernyi Infected with Antheraea pernyi Nucleopolyhedrovirus

“…In the midgut of Aedes aegypti , silencing of 5G1, which belongs to the midgut serine protease family, or the soybean trypsin inhibitor significantly increased midgut infection rates of Dengue virus 2 (DENV-2), suggesting that some midgut serine proteases may limit DENV-2 infectivity of A . aegypti [4]. Smartt et al .…”