Point mutations within the betaG-betaH loop of foot-and-mouth disease virus O1K affect virus attachment to target cells.

The amino acid sequence Arg-Gly-Asp (RGD) is a highly conserved region located on the P1D protein of most sero- and subtypes of foot-and-mouth disease virus (FMDV)and participates in binding of FMDV to their target cells. In order to analyze the role of the RGD sequence in FMDV infection of cells in more detail, 13 mutations within or near the RGD sequence of virus type O1Kaufbeuren were designed by using a full-length cDNA plasmid. Transfection of baby hamster kidney cells (BHK-21) with in vitro-transcribed cRNAs containing mutations bordering the RGD sequence led to the production of infectious virus in most cases. In contrast, almost all of the mutants containing changes within the RGD sequence produced noninfectious viral particles indistinguishable from wild-type virus by electron microscopy. In order to demonstrate that these noninfectious progeny from the RGD mutants were defective only in their cell adsorption, the respective cRNAs were cotransfected together with a cRNA expressing the wild-type P1 protein. The resulting virus particles were able to infect BHK-21 cells. These results demonstrate the important role of the RGD sequence in FMDV binding to cells but also emphasize the influence of other amino acids in the bordering region.