Foot-and-mouth disease virus epitope dominance in the antibody response of vaccinated animals

Abstract

Five neutralizing antigenic sites have been identified on the surface of serotype O foot-and-mouth disease virus (FMDV). A set of mAb neutralization-escape mutant viruses was used for the first time to evaluate the relative use of known binding sites by polyclonal antibodies from three target species: cattle, sheep and pigs. Antibodies to all five neutralizing antigenic sites were detected in all three species, with most antibodies directed against antigenic site 2, followed by antigenic site 1. In 76 % of cattle, 65 % of sheep and 58 % of pigs, most antibodies were directed against site 2. Antibodies specific to antigenic sites 3, 4 and 5 were found to be minor constituents in the sera of each of the target species. This implies that antigenic site 2 is a dominant neutralization immunogenic site in serotype O FMDV and may therefore be a good candidate for designing novel vaccines.Foot-and-mouth disease (FMD) is a severe, clinically acute vesicular disease of cloven-hoofed domestic and wild animals and is present in all continents except Australasia and North America. The causative agent of FMD is Footand-mouth disease virus (FMDV), the prototype member of the genus Aphthovirus in the family Picornaviridae. There are seven distinct serotypes of FMDV (O, A, C, Asia-1, SAT-1, SAT-2 and SAT-3) and multiple strains, indicating significant antigenic variability. Currently, immunization with conventional inactivated whole-virus vaccine is the main method of FMD control, but strain composition of vaccines must be selected with care. The humoral immune response has been generally accepted as the most important factor in conferring vaccine-induced protection against the disease, as a strong correlation has been reported between the levels of virus-neutralizing antibody produced after vaccination and subsequent protection of cattle, one of the main target species (Pay & Hingley, 1987). The mechanism by which antibodies protect against FMDV is poorly understood, and different factors may be involved in vivo compared with the situation measured in vitro (Dunn et al., 1998;McCullough et al., 1992). Several studies have been carried out in the last two decades to identify the targets on the virus surface for the binding of neutralizing antibodies, and mAbs have been powerful tools for identifying the amino acid footprint of different antigenic sites, mainly by sequencing mAb-resistant (mar) mutants. This approach has been used successfully to delineate the neutralizing antigenic sites of viruses representing serotypes O (Aktas & Samuel, 2000;Barnett et al., 1998;Crowther et al., 1993b), A (Baxt et al., 1989;Bolwell et al., 1989;Mahapatra et al., 2011;Thomas et al., 1988a), C (Mateu et al., 1990, Asia-1 (Grazioli et al., 2003) and SAT (Crowther et al., 1993a; Grazioli et al., 2006). FMDV serotype O is the most prevalent globally and has been studied most extensively. Five neutralizing antigenic sites (1-5), involving three of the capsid proteins (VP1-3), have been identified on the surface of serotype O FMDV (Aktas & Samue...

Novel antibody binding determinants on the capsid surface of serotype O foot-and-mouth disease virus

“…A contributory factor might be that only a single mutation had been introduced at each of the sites 2–5 in the 5M virus, whereas four mutations had been introduced in the G–H loop (site 1). Considering this, and that antigenic site 2 has been reported to be immunodominant in the polyclonal response of FMD-vaccinated animals (Mahapatra et al , 2012), it is not surprising that guinea pigs were protected in cross-challenge experiments carried out by Dunn et al (1998).…”

Genetic basis of antigenic variation in foot-and-mouth disease serotype A viruses from the Middle East

“…Moreover VP2-70 has been reported to be critical in neutralising antigenic site 2 of serotype O viruses [7]. In addition, epitopes present in this area have recently been reported to be dominant within the polyclonal response of serotype O vaccinated animals and mutations in this area resulted in significant reduction in neutralising antibody titres [34].…”

Determining the Epitope Dominance on the Capsid of a Serotype SAT2 Foot-and-Mouth Disease Virus by Mutational Analyses

“…Control of FMD has been reliant on large-scale vaccinations with inactivated whole-virus vaccines (7). However, the extensive antigenic diversity within the FMDV serotypes impedes the efficacy of vaccines; therefore, the strain composition of FMD vaccines must be selected with caution (8,9).…”