Immunogenic Streptococcus equi cell surface proteins identified by ORFeome phage display

Area of Science:

• Veterinary Microbiology
• Immunology
• Molecular Biology

Background:

• Equine strangles, caused by Streptococcus equi subspecies equi (S. equi), is a major cause of illness and death in horses.
• Current diagnostic and vaccination strategies for S. equi require improvement.

Purpose of the Study:

• To identify antigenic proteins of S. equi using an ORFeome phage display platform.
• To evaluate the potential of identified proteins as vaccine candidates and diagnostic markers.

Main Methods:

• Construction and screening of an S. equi ORFeome phage display library using serum from exposed horses.
• Identification of antigenic proteins: a novel proline-rich repeat domain protein, a serine peptidase, and the M-like protein SeM.
• Confirmation of immunogenicity using ELISA and analysis of protein conservation in S. equi genomes.

Main Results:

• Three major S. equi surface proteins (proline-rich repeat protein, serine peptidase, SeM) were identified as antigenic.
• The proline-rich repeat protein and serine peptidase were confirmed as immunogenic and highly conserved in S. equi.
• An immunogenic region of SeM was identified, distinct from its known IgG-binding region.

Conclusions:

• The identified proline-rich repeat protein and serine peptidase are promising candidates for S. equi vaccines and diagnostics.
• These proteins are conserved in S. equi, suggesting broad applicability.
• This study provides novel insights into S. equi immunogenic proteins and potential diagnostic/vaccine targets.