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

• Published in: Veterinary microbiology 2015-11, Vol.180 (3-4), p.253-259
• Main Authors: Velineni, Sridhar, DeNegri, Rafaela, Artiushin, Sergey C., Timoney, John F.
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Bacterial - blood; Antibody Formation; Antibody responses; Antibody Specificity; Extract vaccine; FSR; Horse Diseases - immunology; Horses - immunology; Horses - microbiology; HylC; IdeE2; Recombinant Proteins; Se75.3; SeM-N2; Streptococcal Infections - immunology; Streptococcal Infections - veterinary; Streptococcus equi; Streptococcus equi - classification; Streptococcus zooepidemicus
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2015.09.004

•S. equi and S. zooepidemicus share 96% DNA identity and express many proteins in common.•Only 3 of 23 proteins of S. equi and S. zooepidemicus elicited antibody unique to S. equi infection.•These are platelet activating peptidase IdeE2, antiphagocytic SeM and Se75.3 of unknown function.•Immunization with extract vaccine does not stimulate IdeE2 and Se75.3 specific antibodies.•HylC (hyaluronidase C) specific antibody is elicited by S. zooepidemicus but not by S. equi. Streptococcus zooepidemicus (Sz) and its clonal derivative Streptococcus equi (Se) share greater than 96% DNA identity and elicit immune responses to many shared proteins. Identification of proteins uniquely targeted by the immune response to each infection would have diagnostic value. The aim of the study was to compare serum antibody responses of horses infected by Se or Sz. Antibody levels were measured to panels of recombinant proteins of Sz and Se in sera of horses and ponies before and after experimental and naturally occurring invasive infections by these organisms. Antibody responses to an Se extract vaccine were also measured. Sera diluted 1:200 were assayed in triplicate using optimum concentrations of 9 and 14 immunoreactive proteins of Se and Sz, respectively. Bound IgG was detected using HRP-Protein G conjugate. Antibodies specific for SeM-N2, IdeE2, Se42.0 and Se75.3 (SEQ2190) were elicited by Se but not by Sz infection. Commercial Se extract vaccine did not elicit responses to IdeE2 or Se75.3. Sz infections resulted in significant (p