B-cell epitope mapping of the VapA protein of Rhodococcus equi: Implications for early detection of R-equi disease in foals

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p> Linear B-cell epitopes of the <jats:italic>Rhodococcus equi</jats:italic> virulence-associated protein (VapA) were mapped using a synthetic peptide bank in this study. The peptides were screened in an enzyme-linked immunosorbent assay (ELISA) with a total of 70 sera from foals with current <jats:italic>R. equi</jats:italic> disease (51 sera), as well as from foals that had either recovered from <jats:italic>R. equi</jats:italic> infection 10 months previously (3 sera) or that had no known history of <jats:italic>R. equi</jats:italic> disease (16 sera). An epitope with the sequence NLQKDEPNGRA was identified and was universally recognized by all 51 sera from foals with <jats:italic>R. equi</jats:italic> disease and was not recognized by any of the other sera. There was poor reactivity between all sera and peptides relating to other areas of the VapA protein. It is proposed that an ELISA based upon a defined peptide epitope may be used in an improved serological diagnostic test for <jats:italic>R. equi</jats:italic> infection in foals. </jats:p>