Several recombinant capsid proteins of equine rhinitis a virus show potential as diagnostic antigens.

Equine rhinitis A virus (ERAV) is a significant pathogen of horses and is also closely related to Foot-and-mouth disease virus (FMDV). Despite these facts, knowledge of the prevalence and importance of ERAV infections remains limited, largely due to the absence of a simple, robust diagnostic assay. In this study, we compared the antigenicities of recombinant full-length and fragmented ERAV capsid proteins expressed in Escherichia coli by using sera from experimentally infected and naturally exposed horses. We found that, from the range of antigens tested, recombinant proteins encompassing the C-terminal region of VP1, full-length VP2, and the N-terminal region of VP2 reacted specifically with antibodies present in sera from each of the five experimentally infected horses examined. Antibodies to epitopes on VP2 (both native and recombinant forms) persisted longer postinfection (>105 days) than antibodies specific for epitopes on other fragments. Our data also suggest that B-cell epitopes within the C terminus of VP1 and N terminus of VP2 contribute to a large proportion of the total reactivity of recombinant VP1 and VP2, respectively. Importantly, the reactivity of these VP1 and VP2 recombinant proteins in enzyme-linked immunosorbent assays (ELISAs) correlated well with the results from a range of native antigen-based serological assays using sera from 12 field horses. This study provides promising candidates for development of a diagnostic ERAV ELISA.