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Immunogenic Streptococcus equi cell surface proteins identified by ORFeome phage display | mSphere
This work utilized an ORFeome phage display platform to systematically identify antigenic epitopes produced by Streptococcus equi subspecies equi (S. equi), an important equine pathogen and the causative agent of horses strangles. Three major S. equi surface proteins were identified: a novel proline-rich repeat domain protein, a serine peptidase, and the M-like protein SeM. The proline-rich repeat protein and serine peptidase were confirmed to be immunogenic in horses with strangles, and their sequences were shown to be conserved in global S. equi genomes, in contrast to their diversity in S. equi subsp. zooepidemicus. With the well-characterized S. equi immunogenic protein SeM, this paper identified an immunogenic region outside of the reported critical IgG-binding region. This work provides novel insights to the understanding of the S. equi immunogenic proteins and provides peptide regions that could serve as vaccine candidates against S. equi or as diagnostic markers to specifically identify S. equi infections.
