Strain-dependent disease and response to favipiravir treatment in mice infected with Chikungunya virus.

Antiviral countermeasures are needed to reduce the morbidity associated with Chikungunya virus (CHIKV) infection. This arbovirus reemerged in 2004 and causes periodic outbreaks in various areas throughout the world. While infection is rarely lethal, the majority of people infected with the virus develop a hallmark arthralgia as well as other disease manifestations. The virus is classified within three phylogenetic groups, namely, West African, East/Central/South African (ECSA), and Asian. Six strains of CHIKV covering the three phylogenetic groups were studied for their replication in cell culture, their ability to cause disease in susceptible mouse strains and susceptibility to antiviral treatment. Differential replication kinetics were observed for various CHIKV isolates in cell culture, which coincided with a decreased sensitivity to antiviral treatment as compared with ECSA and Asian clade viruses. This was confirmed in mouse infection studies with severe disease observed in mice infected with West African clade viruses, mild disease phenotype after infection with Asian clade viruses and an intermediate disease severity associated with ECSA virus infection. We also tested a broadly active antiviral, Favipiravir (T-705), which activity was inversely proportional to disease severity. These data suggest that some clades of CHIKV may cause more severe disease and may be more difficult to treat.