Evaluation of genetically engineered derivatives of a Chinese strain of foot-and-mouth disease virus reveals a novel cell-binding site which functions in cell culture and in animals

Adaptation of field isolates of foot-and-mouth disease virus (FMDV) to grow in cells in culture can result in changes in viral properties that include acquisition of the ability to bind to cell surface heparan sulfate (HS). After 13 passages on BHK cells to produce a vaccine, a Cathay topotype isolate of FMDV serotype O from China (O/CHA/90) extended its cell culture host range and bound to heparin-Sepharose, although it did not require cell surface HS as a receptor molecule. To understand these phenomena, we constructed chimeric viruses by using a type A(12) infectious cDNA and the capsid protein-coding regions of O/CHA/90 and its cell culture-adapted derivative (vac-O/CHA/90). Using a set of viruses derived from these chimeras by exchanging portions of the capsid-coding regions, we discovered that a group of amino acid residues that surround the fivefold axis of the icosahedral virion determine host range in cell culture and influence pathogenicity in pigs. These residues included aromatic amino acids at positions 108 and 174 and positively charged residues at positions 83 and 172 in protein 1D. To test if these residues participated in non-integrin-dependent cell binding, the integrin-binding RGD sequence in protein 1D was changed to KGE in two different chimeras. Evaluation of these KGE viruses indicated that growth in cell culture was not dependent on HS. One of these viruses was tested in pigs, where it produced a mild disease and maintained its KGE sequence. These results are discussed in terms of receptor utilization and pathogenesis of this important pathogen.