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Characterization and immunogenicity of pyrogenic mitogens SePE-H and SePE-I of Streptococcus equi
S C Artiushin1, J F Timoney, A S Sheoran
1Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546, USA.
Abstract:
Two pyrogenic mitogens, SePE-H and SePE-I, were characterized in Streptococcus equi, the cause of equine strangles. SePE-H and SePE-I have molecular masses of 27.5 and 29.5 kDa, respectively, and each is almost identical to its counterpart in Streptococcus pyogenes M1. Both genes are adjacent to a gene encoding a phage muramidase of 49.7 kDa and are located immediately downstream from a phage genomic sequence almost identical to a similar phage sequence in S. pyogenes M1. Strong mitogenic responses were elicited by both proteins from horse peripheral blood mononuclear cells. However, although both were pyrogenic for rabbits, only SePE-I was pyrogenic in ponies. Convalescent sera contained antibody to each mitogen and horses recovered from strangles or immunized with SePE-I were resistant to the pyrogenic effect of SePE-I. The immunogenicity of SePE-I suggests that it should be included in new generation strangles vaccines. In isolates of S. equi sepe-I and sepe-H were consistently present but they were absent from the closely related Streptococcus zooepidemicus, suggesting that phage mediated transfer was an important event in the formation of the clonal, more virulent, S. equi from its putative S. zooepidemicus ancestor.
Insights
Two pyrogenic mitogens, Streptococcus equi pyrogenic exotoxin-H (SePE-H) and SePE-I, were identified in the bacteria causing equine strangles. SePE-I is immunogenic and may be valuable for developing new strangles vaccines.
Area of Science:
- Microbiology
- Immunology
- Veterinary Science
Background:
- Streptococcus equi causes equine strangles, a contagious upper respiratory tract infection.
- Pyrogenic exotoxins are virulence factors in some Streptococcus species.
Purpose of the Study:
- To characterize two pyrogenic mitogens, SePE-H and SePE-I, from Streptococcus equi.
- To investigate their role in equine strangles and potential for vaccine development.
Main Methods:
- Molecular mass determination of SePE-H and SePE-I.
- Gene sequencing and comparison with Streptococcus pyogenes.
- Testing mitogenic and pyrogenic responses in horse peripheral blood mononuclear cells and ponies.
- Assessing antibody responses in convalescent horses and evaluating pyrogenic resistance after immunization.
Main Results:
- SePE-H (27.5 kDa) and SePE-I (29.5 kDa) are highly similar to Streptococcus pyogenes counterparts.
- Both SePE-H and SePE-I induced strong mitogenic responses in horse cells.
- SePE-I was pyrogenic in ponies, while SePE-H was not.
- Horses developed antibodies to SePE-I and became resistant to its pyrogenic effects.
- SePE-I and SePE-H genes were present in S. equi but absent in Streptococcus zooepidemicus, suggesting phage-mediated transfer.
Conclusions:
- SePE-I is immunogenic in horses and a potential candidate for new strangles vaccines.
- Phage-mediated transfer of pyrogenic exotoxin genes may have contributed to the evolution of virulent S. equi strains.
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