containing an RDD triplet in the receptor-binding site was obtained from the serotype Asia 1 field isolate after a single cattle-to-pig transmission and subsequent BHK-21 in vitro passage. Sequence analysis of 10 biological clones of the VP1 encoding region of this population demonstrated that RDD viruses instead of the original RGD virus became predominant at an early phase of Asia1/JS/CHA/05 quasispecies evolution. Unexpectedly, however, both RGD and RSD viruses were obtained from the Asia1/JSM4 population that were generated after four serial passages of the Asia1/JS/CHA/05 field isolate in suckling mice, via intraperitoneal inoculation. The population equilibrium of RSD mutant and ancestor viruses selleck chemical was maintained after 20 passages of the Asia1/JSM6 population in BHK-21 cells. Although RDD- or RSD-containing FMDV are unusual, they were genetically stable upon extended replication in cell culture. Our results suggest that, in the context of the capsid proteins of Asia1/JS/CHA/05, a highly conserved RGD motif is not essential for replication in vitro and in vivo, suggesting functional flexibility of FMDV to enter cells
in response to environmental modifications. Like other RNA viruses, FMDV exists as closely related but non-identical genomes, termed viral quasispecies [30, 31]. Genetic diversity is an intrinsic property of the quasispecies, which arise due to the lack of proofreading Selleck NVP-HSP990 activity during viral genome replication, a short replication cycle, and other environmental selective pressures [32, 33]. Our observations showed that evolution of FMDV population exhibited receptor binding motif diversity (genetic diversity) subjected to short-term passage of field isolate in different environments. From the standpoint of RNA virus population evolution, one possible scenario could explain this observation. The early interactions between viruses and host cells exert major selective force on virus populations, thus, the Selleck Vorinostat variants (RSD- and RDD-containing viruses) may already be
present at low frequency in the natural population that are possibly more fit in new environments and become dominant strains. While this presumption is contrary to the view that the RGD triplet is highly conserved among natural isolates of FMDV, there is direct evidence that an RDD containing field virus was isolated from pigs during a type Asia 1 FMD outbreak in China. RDD-containing FMDV VP1 genes were amplified from sheep oesophageal-pharyngeal fluids (OP-fluids) collected during 2006 from a sheep herd in the region of China that had endemic Asia 1 serotype FMDV [34, 35]. The emergence of these check details non-RGD mutants in nature is likely to be influenced by specific epidemiological and immunological aspects of host-virus interaction as well as the quasispecies composition of the viral population [36–39].