CHARACTERIZATION OF MONOCLONAL-ANTIBODIES AGAINST A TYPE SAT-2 FOOT-AND-MOUTH-DISEASE VIRUS

This paper is the first to describe characterization of monoclonal ant ibodies (MAbs) against a South African Territories 2 (SAT 2) foot-and- mouth disease virus (isolate Rho 1/48). Twelve MAbs which neutralized homologous virus were characterized in indirect and sandwich ELISA usi ng purified Rho 1/48 virus particles, subunits, trypsin-treated, and c hemically denatured virus. All the Mabs inhibited haemagglutination by parental virus. Binding of the MAbs to 73 SAT 2 field isolates was me asured in a sandwich ELISA and defined four distinct antigenic regions . Preliminary characterization of escape mutants selected with some of the MAbs using virus neutralization tests, ELISA, and amino acid sequ encing is included. MAbs 2, 25, 40, 48 and 64, reacted with a linear e pitope on the VP1 loop region. An amino acid change at position 149 (v aline to glutamic acid) was detected in mutants selected by MAb 2 and 40 and this eliminated binding and neutralization by all the other MAb . This epitope was conformation-dependent and was conserved in all 73 isolates of SAT 2 examined. Escape mutants isolated with MAb 41 and 44 , had changes at positions 156 (glycine to aspartic acid), or 158 (ser ine to leucine) respectively. These MAbs bound with Rho 1/48 only out of 73 field strain viruses studies and the reactions of MAbs from the other groups was unaltered. MAb 27, 28 and 37 reacted with a conformat ion-dependent epitope on VP1 which was not conserved in field isolates . All mutants selected by these MAbs had a single amino acid substitut ion at position 149 (valine to alanine). The same change was always fo und in field isolates which did not bind MAbs from this group. MAb 11 reacted with a linear epitope associated with amino acids 147 or 148 o n VP1 and showed similar binding characteristics to a conformation dep endent MAb 7, no amino acid residue changes were found within VP1 for monoclonal antibody 7 mutants.