Foot-and-mouth disease virus forms a highly stable, EDTA-resistant complex with its principal receptor, integrin alpha v beta 6: Implications for infectiousness

The initial stage of foot-and-mouth disease virus (FMDV) infection is virus binding to cell surface integrins via the RGD motif in the GH loop of the VP1 capsid protein. As for all ligand/integrin interactions, the initial contact between FMDV and its integrin receptors is cation dependent and hence inhibited by EDTA. We have investigated this binding process with RGD-containing peptides derived from the VP1 capsid protein of FMDV and discovered that, upon binding, some of these peptides form highly stable, EDTA-resistant associations with integrin alpha v beta 6. Peptides containing specific substitutions show that this stable binding is dependent on a helical structure immediately C terminal to the RGD and, specifically, two leucine residues at positions RGD +1 and RGD +4. These observations have a biological consequence, as we show further that stable, EDTA-resistant binding to alpha v beta 6 is a property also exhibited by FMDV particles. Thus, the integrin-binding loop of FMDV appears to have evolved to form very stable complexes with the principal receptor of FMDV, integrin alpha v beta 6. An ability to induce such stable complexes with its cellular receptor is likely to contribute significantly to the high infectiousness of FMDV.