Comparison of specificities of serum antibody responses of horses to clinical infections caused by Streptococcus equi or zooepidemicus.

This research article explores the differences in immune responses in horses when infected by two closely related bacteria, Streptococcus equi and Streptococcus zooepidemicus. Detection of distinct antibodies elicited by each infection could be used to differentiate between the two infections.

Objective and Methodology

• The study aim was to identify the unique immune response of horses, specifically their serum (the component of blood that houses antibodies) response, to infections by Streptococcus equi (Se) and Streptococcus zooepidemicus (Sz).
• Streptococcus equi and Streptococcus zooepidemicus share more than 96% of their DNA and many common proteins that trigger immune responses; hence differentiating their infections can be challenging.
• To investigate this, the researchers measured the antibody levels in response to sets of recombinant proteins of Se and Sz. This was done before and after experimental infections in horses and ponies. They also measured the responses to Se extract vaccine.
• The testing was thorough, with each serum sample diluted and assayed in triplicate, using optimal concentrations of known immunoreactive proteins of Se and Sz.

Results

• The results showed that certain antibodies were produced in response to Se infection, but not to Sz infection. These include antibodies for proteins dubbed SeM-N2, IdeE2, Se42.0 and Se75.3 (SEQ2190).
• The commercially available Se extract vaccine, on the other hand, did not elicit responses to proteins IdeE2 or Se75.3.
• Sz infections triggered significant (p<0.01) responses to proteins named Sz115, SzM, ScpC, SzP, MAP and streptokinase, indicating these proteins' role during Sz infections.
• The study discovered antibodies response unique to Sz infection, specifically FSR and HylC.

Conclusion

• The study concluded that antibodies to IdeE2, Se75.3 and SeM-N2 can be used to differentiate an infection caused by Se from a Sz-caused infection.
• Interestingly, the study highlighted that an infection by Se, but not vaccination with Se extract, elicits antibody to IdeE2 and Se75.3.
• This research might contribute to the development of more accurate diagnostic methods for these types of infections in horses. It may also be significant for understanding the immunity function in response to Se and Sz infections.