Proline-glutamic acid-proline-lysine peptide set as a specific antigen for the serological diagnosis of strangles.
Authors: Hobo S, Niwa H, Anzai T
Journal: The Veterinary record
Summary
# Editorial Summary Streptococcus equi diagnosis has historically suffered from cross-reactivity issues with the closely related S. zooepidemicus, complicating serological identification of strangles infections. Hobo and colleagues synthesised a panel of peptide epitopes derived from M-like proteins (SeM and SzPSe) and tested their reactivity against sera from 17 experimentally infected horses, 25 convalescent cases, and 1,945 control animals using ELISA methodology. Whilst most SeM-derived peptides showed problematic cross-reactivity with S. zooepidemicus-infected horses, the proline-glutamic acid-proline-lysine (PEPK) repeat peptide—derived from the SzPSe protein—demonstrated strong specific reactivity with both experimentally infected and convalescent S. equi cases whilst showing minimal reactions to S. zooepidemicus and control sera. This finding offers equine practitioners a more specific serological diagnostic tool for strangles, potentially improving confirmation of infection status and reducing false positives that could confound herd health decisions and treatment protocols.
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Practical Takeaways
- •PEPK peptide-based ELISA offers a specific serological test for confirming strangles infection in horses with minimal false positives from S. zooepidemicus exposure
- •This peptide-based approach could improve diagnostic accuracy for strangles compared to broader bacterial antigen tests that cross-react with other streptococcal species
- •The test may be useful for identifying convalescent horses and documenting previous strangles exposure in herd health and purchasing decisions
Key Findings
- •The PEPK (proline-glutamic acid-proline-lysine) repeats peptide set showed strong reactivity with sera from horses experimentally infected with S. equi and convalescent strangles cases
- •PEPK peptide set demonstrated minimal cross-reactivity with S. zooepidemicus-infected and control horse sera, indicating high specificity for S. equi
- •Other SeM peptide sets showed variable reactivity and cross-reactivity with both S. equi and S. zooepidemicus sera, making them less suitable for diagnosis
- •The PEPK peptide antigen derived from SzPSe M-like protein areas provides a specific serological marker for strangles diagnosis