The equine immune response to Streptococcus equi subspecies zooepidemicus during uterine infection.
Authors: Causey Robert C, Weber James A, Emmans Erin E, Stephenson Lisa A, Homola Alma D, Knapp Kiley R, Crowley Ian F, Pelletier Danielle C, Wooley Nicole A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Streptococcus equi subspecies zooepidemicus causes significant reproductive disease in mares, yet the specificity of immune responses to different strains remained poorly characterised until this work. Causey and colleagues inoculated eight mares with two different strains of S. zooepidemicus sequentially over repeated oestrous cycles, using bactericidal testing and immunoblotting to track antibody responses across eight cycles and reversing strain order between groups to control for sequence effects. The research revealed that immune responses to each strain developed at distinctly different timepoints, with significantly greater antibody binding to the first-inoculated strain compared to the second (P < 0.05), demonstrating that protection is strain-specific rather than broadly protective across isolates. These findings have direct implications for vaccine development and infection control strategies in breeding programmes, suggesting that exposure to one S. zooepidemicus strain does not reliably protect against subsequent infection with different strains and that previous infection history may influence susceptibility patterns in naive mares. Understanding this strain-specific immunity is essential for farriers and veterinarians managing endometritis cases and for stud managers developing biosecurity protocols, particularly when mares are moved between facilities where different strains may be circulating.
Read the full abstract on PubMed
Practical Takeaways
- •S. zooepidemicus strains causing uterine infections in mares elicit different immune responses, meaning prior exposure to one strain may not provide complete protection against other strains
- •Vaccination or immunization strategies against S. zooepidemicus should consider strain variability to ensure adequate protection across multiple circulating strains
- •Recurrent or persistent uterine infections with S. zooepidemicus may involve different strains rather than treatment failure, warranting bacterial culture and strain identification
Key Findings
- •Five isolates of S. zooepidemicus were differentiated into four distinct strains by bactericidal testing and pulsed-field gel electrophoresis
- •Immune responses to each strain arose at different times, demonstrating strain-specific immune dynamics
- •Immunoblots showed significantly greater antibody binding to the first inoculated strain compared to the second strain (P < 0.05)
- •Immune responses to S. zooepidemicus during uterine infection are partly strain-specific rather than uniformly cross-reactive