Foot-and-mouth disease virus can utilize the C-terminal extension of coxsackievirus A9 VP1 for cell infection

Foot-and-mouth disease virus (FMDV) is known to employ the conserved Arg-Gl y-Asp (RGD) tripeptide located on the variable betaG-betaH loop of the VP1 capsid protein for binding to cells. Coxsackievirus A9 (CAV9) also carries an RGD sequence, but on a short C-terminal extension of its VP1 and in a di fferent amino acid context. This apparent relationship raised the question of whether insertion of the heterologous CAV9 sequence into FMDV would infl uence infection by the genetically modified FMDV. Four VP1 mutants were gen erated by PCR mutagenesis of a full-length FMDV cDNA plasmid. After transfe ction of BHK-21 cells, viral protein synthesis and virus particle formation could be detected. Two of the four mutants, mV9b and mV9d, could be propag ated in BHK-21 cells, but not in CV-1 cells. Bath of these mutants containe d 17 amino acids of the C terminus of CAV9 VP 1. Infection of BHK cells cou ld be specifically inhibited by rabbit immune serum raised against a synthe tic peptide representing the amino acid sequence of the C-terminal extensio n of CAV9 VP 1. This demonstrated the direct involvement of the inserted se quence in cell infection. In fact, genetically modified FMDV O(1)Kwas capab le of employing the VP 1 C-terminal RGD region of CAV9 for infection of BHK cells. In addition, these results show that, even in cell culture-adapted viruses, the RGD-containing betaG-betaH loop plays an important role in vir us infectivity.