Since other FMDV lack the RGD motif, host cell recognition may be mediated through another integrin receptor or a non-integrin Selinexor pathway, or use a third receptor (neither integrin-based nor HS) for entry into the host cell [18, 21, 40]. Further studies are required to analyze the interaction of these mutants with the major FMDV integrin receptors αvβ3, αvβ6, αvβ1 and αvβ8 identified to date, and to understand

whether these viruses obtain alteration of cell tropism, antigenicity, and virulence. To examine the influence of single amino acid substitutions in the receptor binding site of RDD-containing FMD viral genome on virus viability and the ability of non-RGD viruses to cause disease in susceptible animals, we constructed an FMDV Asia1/JS/p1c8 full-length clone and derived mutant molecules with RGD or RSD receptor recognition motifs. Following transfection of BSR cells with these clones, three recombinant viruses were rescued, in particular, six other amino acid differences in the P1 capsid region of Asia1/JS/CHA/05 and Asia1/JSM4 (compared with Asia1/JS/p1c8) did not affect rescue of viable RGD- and RSD-harboring viruses. Furthermore, in vitro growth

properties of these viruses did not differ significantly. Our results showed that Asia1/JS/p1c8 viral genome can beta-catenin cancer tolerate substitutions in the receptor binding site with no other changes in the capsid. The ability of the Asia1/JS/p1c8 viral genome to tolerate substitution of receptor binding sites may depend on the capsid sequence, because the Asp-143 Gly change of receptor recognition

site aminophylline was lethal in the context of the capsid proteins of FMDV C-S8c1. However, the same replacement yielded viable viruses in the context of the capsid protein of FMDV C-S8c1p100 and C-S8c1p213 [21, 41]. To assess the ability of non-RGD FMD viruses to cause disease in naturally susceptible animals, we performed experiment infections of cattle and pigs using the Asia1/JS/p1c8 and two non-RGD recombinant viruses. Subsequent experiments showed that all viruses were able to cause disease in cattle and pigs and produce rapid onset of clinical signs, characteristic of infection with RGD field strains. The disease was characterized by viremia in all inoculated animals, including the individuals that did not generate vesicular lesions. Amongst these viruses, the RSD virus produced less tissue damage at the inoculation sites and induced fever and vesicles a day later than in the animals inoculated with RDD-containing viruses, which indicated a different degree of disease severity. The different virulence of these viruses was also supported by the maintenance of original receptor recognition sequence in vesicle samples obtained from infected animals.