Argonaute 2 Suppresses Japanese Encephalitis Virus Infection in <i>Aedes aegypti</i>

Abstract

SUMMARY: There are three main innate immune mechanisms against viruses in mosquitoes. Infection with the flavivirus dengue virus is controlled by RNA interference (RNAi) and the JAK-STAT and Toll signaling pathways. This study showed that another flavivirus, Japanese encephalitis virus (JEV), did not invade the salivary glands of Aedes aegypti and that this may be a result of the innate immune resistance to the virus. Argonaute 2 (Ago2) plays a critical role in the RNAi pathway. To understand the mechanism of JEV resistance, we focused on Ago2 as a possible target of JEV. Here, we show that the expression of MyD88 (a mediator of Toll signaling) and Ago2 mRNAs was induced by JEV in the salivary glands of Ae. aegypti mosquitoes and that Ago2, JAK, and domeless (DOME ) mRNAs were induced by JEV in the bodies of Ae. aegypti mosquitoes. Double-stranded (ds) Ago2 RNA enhanced JEV infection, and the virus was detected in salivary glands by immunofluorescence assay. In contrast, MyD88 dsRNA had no effect on JEV infection. These data suggest that Ago2 plays a crucial role in mediating the innate immune response of Ae. aegypti to JEV in a manner similar to that employed by dengue virus.

An Aedes aegypti-Derived Ago2 Knockout Cell Line to Investigate Arbovirus Infections

“…For many mosquito-borne flaviviruses, replication increases in Ae. aegypti or D. melanogaster in vitro as well as in vivo in the absence of an exo-siRNA response [11,21,44]. In addition, previous studies observed ZIKV-specific siRNAs in infected mosquito cells and increased ZIKV replication in a Dcr2 knockout cell line, which provided supporting evidence for the antiviral activity of the exo-siRNA pathway against ZIKV [16,46].…”

“…The exo-siRNA pathway is the main antiviral defense pathway in mosquitoes, with Dcr2 and Ago2 having major roles [19,21,[42][43][44][45]. Silencing one of these key proteins during infection leads to an increase in viral replication for most arboviruses tested, including CHIKV, DENV and RVFV [7].…”

“…Surprisingly, ZIKV seems to be an exception as silencing of Ago2 has no effect on ZIKV infection, suggesting that unlike Dcr2, Ago2 does not exert any antiviral activity [16][17][18]. Moreover, the magnitude of the observed increase during Ago2 knockdown for different viruses can vary, suggesting either differences in the importance of Ago2 antiviral activity between viruses [16,[19][20][21][22], or effects of an incomplete knockdown and therefore residual activity of the target protein. Interestingly, Ago2 antiviral activity has always been linked to the siRNA pathway, with the incorporation of vsiRNAs used as guides to cleave complementary viral RNA.…”

Proteomics Study on the Cerebrospinal Fluid of Patients with Encephalitis

“…Additionally, the findings on Jak-STAT signaling pathway associated with the encephalitis were also supported by previous reports. 19 − 21 …”

In Silico Validation of D7 Salivary Protein-derived B- and T-cell Epitopes of Aedes aegypti as Potential Vaccine to Prevent Transmission of Flaviviruses and Togaviruses to Humans

“…Also, exposure to sequential bites of uninfected mosquitoes altered the immune response favorably with increased participation of T-helper cells [ 41 ]. It is potentially possible that JE virus, which could be transmitted, by Culex and Aedes species [ 42 ] may also be interfered with human host immune response to D7 short forms. Indeed, in this context a concern would be the role of enhancing antibodies in the increased virulence of Dengue virus infection resulting in complications like Dengue hemorragic fever and Dengue shock syndrome.…”