Division of Virology, Defence Research & Development Establishment, Gwalior-474 002, India.
Abstracts of the papers presented at the XVIII National Conference of Indian Virological Society at Post Graduate Institute of Medical Education and Research, Chandigarh, India, December 11–13, 2008.
Chikungunya has shown an explosive emergence in several parts of Indian Ocean islands, India and Italy since 2005. In India alone, an estimated 1.4 million inhabitants have been infected in 2006. Chikungunya outbreaks were also reported in 2007 and 2008 from India. Many atypical symptoms including meningoencephalitis, myocarditis and acute hepatitis were recorded during these outbreaks suggesting the severity and fatality of this reemerging infection. So far, no effective antiviral or licensed vaccine is available against Chikungunya infection. RNA interference mediated inhibition of viral replication has recently emerged as a promising antiviral strategy. In this study, we examined the in vitro effectiveness of small interfering RNAs (siRNAs) against the inhibition of Chikungunya virus replication in Vero cells. Two siRNAs against the conserved regions of nsP3 and E1 genes of Chikungunya virus were designed. The siRNA activity was assessed by detecting both the infectious virus and its genome. The results indicated a reduction of virus titer up to 99.6% in siRNA transfected cells compared to control. The viral inhibition was most significant at 24 h (99%), followed by 48 h (65%) post infection. These results were also supported by the quantitative RT-PCR assay revealing 95% reduction in Chikungunya viral genomic RNA. No escape mutants were observed during the long term passage of virus under siRNA pressure. The siRNAs used had no effect on the expression of house keeping gene indicating non-interference in cellular mechanism. The specific and marked reduction in viral replication against rapidly replicating Chikungunya virus achieved in this study offers a potential new therapeutic approach. This is the first report demonstrating the effectiveness of siRNA against in vitro replication of Chikungunya virus.
