Characterization of monoclonal antibodies against a type SAT 2 foot-and-mouth disease virus

Abstract

SummaryThis paper is the first to describe characterization of monoclonal antibodies (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 using purified Rho 1/48 virus particles, subunits, trypsin-treated, and chemically denatured virus. All the Mabs inhibited haemagglutination by parental virus. Binding of the MAbs to 73 SAT 2 field isolates was measured 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 sequencing is included. MAbs 2, 25, 40, 48 and 64, reacted with a linear epitope on the VP1 loop region. An amino acid change at position 149 (valine 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 (serine 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 conformation-dependent epitope on VP1 which was not conserved in field isolates. All mutants selected by these MAbs had a single amino acid substitution at position 149 (valine to alanine). The same change was always found 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 on VP1 and showed similar binding characteristics to a conformation dependent MAb 7, no amino acid residue changes were found within VP1 for monoclonal antibody 7 mutants.

Antigenic analysis of SAT 2 serotype foot-and-mouth disease virus isolates from Zimbabwe using monoclonal antibodies

“…This epitope was highly conserved, Figure 1 The MAb RHO 7, 11, 27, 28, 37 and ZIM 108 formed another group. Crowther and colleagues [2] showed that MAb RHO 7, 27, 28 and 37 react with the same conformational epitope and it is likely that ZIM 108, a neutralizing MAb, also reacts at this site; this was strongly indicated in the MAb escape mutant study where ZIM 108 did not bind to escape mutants produced by MAb Rho 1/48, 7, 11, 27, 28 or 37, but bound to all other mutants. Fifty-three (85%) of the viruses in the study bound MAb from this group.…”

“…The binding of the South African MAb with selected RHO 1/48 MAb escape mutants, produced as described elsewhere [2], was also measured using the sandwich ELISA.…”

“…The isolates from buffalo in Botswana- Figure 5. Analysis of MAb was also made with reference to the studies made on the binding of the MAb to selected RHO 1/48 MAb escape mutants as described previously [2] and to the virus neutralization activity of the MAb. These data are summarized below the cluster analysis in Figure 5 and allow the initial characterization of the MAb from Onderstepoort, in terms of the MAb produced at Pirbright.…”

“…MAb Rho 2, 40, 48, SAR 27a, 62 and 68, respectively, formed a cluster. Crowther and colleagues [2] established that MAb RHO 2, 40 and 48 recognize the same linear epitope. This epitope was highly conserved, Figure 1 The MAb RHO 7, 11, 27, 28, 37 and ZIM 108 formed another group.…”

“…This is important to ensure that vaccine strains share antigens with the potential outbreak strains and therefore induce immunity through the stimulation of cross-reactive antibodies. The primary objective of this study was to examine epitopes shared by viruses using monoclonal antibodies (MAb) in an attempt to assess the likely protection afforded by SAT 2 …”