Abstract
Mosquito-transmitted flavivirus Rocio (ROCV) was responsible for an outbreak of encephalitis in the Ribeira Valley, located in the south coast of Sao Paulo State, Brazil, in 1975–1976. ROCV also causes fatal encephalitis in adult mice. Seroprevalence studies in humans, horses and water buffaloes in different regions of Brazil have suggested that ROCV is still circulating in the country, indicating the risk of re-emergence of this virus. West Nile virus (WNV) is also a mosquito-transmitted encephalitic flavivirus, however, WNV strains circulating in Australia have not been associated with outbreaks of disease in humans and exhibit low virulence in adult mice. To identify viral determinants of ROCV virulence, we have generated reciprocal chimeric viruses between ROCV and the Australian strain of WNV by swapping structural prM and E genes. Chimeric WNV containing ROCV prM-E genes replicated more efficiently than WNV or chimeric ROCV containing WNV prM-E genes in mammalian cells, was as virulent as ROCV in adult mice, and inhibited type I IFN signaling as efficiently as ROCV. The results show that ROCV prM and E proteins are major virulence determinants and identify unexpected function of these proteins in inhibition of type I interferon response.
Highlights
Rocio virus (ROCV) is a member of the genus Flavivirus in the family Flaviviridae
Recovered virus was passaged once in HEK293T cells (p1) and compared with wt ROCV isolate. Both viruses produced plaques of similar size and morphology in BHK cells (Fig. 1b), and replicated with similar efficiencies in mouse embryonic fibroblasts (MEF) (Fig. 1c). These results demonstrate that ROCV was successfully recovered using circular polymerase extension cloning (CPEC), and the CPEC-generated ROCV is indistinguishable from the parental virus
We have previously shown that CPEC methodology allows recovery of a virus that accurately represents the original virus population[27]; deep sequencing of the ROCV isolate used for CPEC recovery was deemed unnecessary
Summary
Rocio virus (ROCV) is a member of the genus Flavivirus in the family Flaviviridae. Like other members of the family Flaviviridae, ROCV is an enveloped virus containing positive-sense RNA genome of approximately 11 kb[1]. The American WNVNY99 strain was shown to be more virulent in mice than the Australian Kunjin virus (KUNV), a naturally attenuated subtype of WNV, and this was attributed to the more efficient inhibition of type I IFN response mediated by non-structural proteins, including NS5520,23,24. We employed the CPEC method to generate infectious cDNA of ROCV and reciprocal prM-E chimeric viruses between ROCV and Australian strain of WNV. We employed these chimeric viruses to show that ROCV prM-E proteins are the major contributors to the virulence of ROCV and identified unexpected role of ROCV prM-E proteins in inhibition of IFN-α/βsignaling
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
