Development of molecular tools and mouse models to study neglected Sindbis virus genotypes and their epidemic potential

About This Grant

PROJECT SUMMARY Sindbis virus (SINV) is a mosquito-borne alphavirus with a single-stranded positive-sense RNA genome. SINV is transmitted between mosquitoes and birds which serve as reservoir hosts for the virus but can cause spillover infections in other vertebrate hosts including humans. SINV can be classified into distinct genotypes (G1-G6) which aligns with their zoogeographical distribution. SINV causes frequent epidemic outbreaks of polyarthritis disease in Northern Europe and has also been associated with outbreaks in Africa. Epidemics in both these regions are caused by G1 viruses. SINV is widely distributed geographically but is not associated with epidemics elsewhere in the world. Despite being prevalent in mosquito populations in Australia, the SINV strains in this region (G2/3 and G6) have never been associated with epidemics of polyarthritis disease here, though isolated human cases have been reported, and serological data shows the occurrence of human infections. The Australian genotypes of SINV (G2/3, G6) are significantly divergent from the G1 viruses which cause frequent epidemics, suggesting that genetic differences between these genotypes may explain why G1 viruses have a propensity to cause epidemics but other genotypes do not. Most of the genetic tools available to study SINV are derived from G1 viruses, and there is only a single non-G1 cDNA clone (for the G4 virus XJ-160). There currently exists no molecular clones for studying other genotypes of SINV, including the divergent Australian G2 and G6 viruses. In this R03 we propose to construct cDNA clones for G2 and G6 SINV and characterize the in vitro replication properties of these clones and compare pathogenesis profiles of virus derived from these clones versus characterized G1 strains in a small animal model. We have established a subcutaneous model of SINV infection and shown that replicating virus can be detected in the skin and joints of adult mice, which reflects the pathogenesis observed in humans. Thus, this serves as a good model for examining the genetic determinants that underlie the epidemic potential of neglected SINV genotypes. These tools will be available to the research community and thus aid in further investigations of other key aspects of arbovirus transmission and pathogenesis including virus-mosquito interactions, species-specific determinants of transmission, and viral immunity.