Research Accomplishment Reports 2007

Novel, Protectively Immunogenic, Surface Exposed, and Secreted Proteins of Streptococcus equi

J.F. Timoney, S. Artiushin
Department of Veterinary Sciences

 

Project Description

a) Se18.9, a potent mucosal immunogen of S. equi was evaluated as a vector for SeM and P3, two virulence proteins unique to S. equi. Pony groups 1, 2 and 3 were immunized intranasally with recombinant chimaeric Se18.9-P3, Se18.9-SeM and Se18.9 respectively. Strong serum IgG responses to Se18.9, SeM and P3 were detected in all ponies 14 days later. However, although mucosal IgA responses to Se18.9 were evident, no SeM or P3 specific IgA was detected. Thus, Se18.9 was an effective intranasal vector of exogenous peptides for equine systemic but not mucosal humoral responses.

b) In vivo studies of the pathogenesis of strangles utilizing biotin-labelled S. equi have shown that a) the crypts of the oro and nasopharyngeal tonsils are portals of entry, b) only few organisms penetrate, and c) interiorization and transport to regional lymph nodes occurs in 1 to 3 hours. Lymph node infection required expression of each of the virulence factors SeM, capsule and streptolysin S. Later, as fever develops, tonsils and lymph nodes have become heavily infiltrated with neutrophils and microcolonies of long chains of extracellular cocci. Horses recovered from strangles were shown to resist tonsillar invasion, an indication that acquired immunity in the tonsils involves potent mechanisms for bacterial inactivation/clearance.

Impact

a) recombinant Se18.9 from S. equi has been shown to be an effective subunit mucosal vector of immunogenic peptides for stimulation of systemic serum antibody in the horse. It may therefore have utility as the basis of a novel vaccine modality.

b) The equine tonsillar complex is the site of uptake of S. equi and of the acquired immune response that clears infection. This confirms previous findings that improved strangles vaccination modalities should target the tonsillar complex.

Publications

Timoney, J.F., Yang, J., Liu, J, and Merant, C. (2007). IdeE reduces the Bactericidal Activity of Equine Neutrophils for Streptococcus equi, Veterinary Immunology & Immunopathology., doi:10.1016/jvetimm.2007.10.017.

Timoney, J.F., Qin, A., Muthupalani, S., Artiushin, S. (2007). Vaccine Potential of Novel Surface Exposed and Secreted Proteins of Streptococcus equi, Vaccine, 25: 5583-5590.

Prescott, J.F., and Timoney, J.F. (2007). Could We Eradicate Strangles in Equids, Journal of the American Veterinary Medical Association, 231: 377-378.

Timoney, J.F. (2007). Strangles Vaccines in Trouble Again, Equine Veterinary Journal, 39: 196.