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Molecular basis of variation in protective SzP proteins of Streptococcus zooepidemicus
1Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington 40546-0099, USA.
Objectives:
To characterize, on a molecular basis, variable regions of the SzP proteins of the Moore and Bryans serovars of Streptococcus zooepidemicus and specificity of opsonic responses.
Sample Population:
14 Moore and Bryans serovars of S zooepidemicus.
Procedure:
Using polymerase chain reaction analysis and primers from the 5' and 3' sequences of the prototype gene SzPW60, the SzP genes of each Moore and Bryans serovar were sequenced and translated, then the amino acid sequences were compared.
Results:
Comparison of the amino acid sequences revealed 2 variations at the N terminus; a hypervariable (HV) region from residue 106 to 166, approximately; and proline-glutamic acid-proline-lysine repeats in the carboxy terminus that ranged in number from 7 to 12. Five distinct motifs, HV 1 to 5, which varied independently of the N termini were found in the internal HV region. All serovars were opsonized by antiserum to the prototype SzPW60 protein, indicating that opsonogenic epitopes are on the conserved regions of the protein.
Conclusion And Clinical Relevance:
Variant motifs may be valuable in epizootiologic and pathogenesis studies of S zooepidemicus infections of the respiratory tract of young horses and in determining whether there are populations of S zooepidemicus unique to specific animal hosts. It is also clear from the opsonic responses to SzP that at least a portion of the protective responses are probably not serovar specific.
Insights
Molecular characterization of Streptococcus zooepidemicus SzP proteins reveals variable regions and conserved opsonogenic epitopes. These findings aid in understanding horse respiratory infections and host-specific bacterial populations.
Area of Science:
- Veterinary Microbiology
- Molecular Biology
- Immunology
Background:
- Streptococcus zooepidemicus causes respiratory tract infections in young horses.
- The SzP protein is a key virulence factor in S. zooepidemicus.
- Understanding SzP variability is crucial for diagnosing and controlling infections.
Purpose of the Study:
- To molecularly characterize variable regions of SzP proteins in Moore and Bryans serovars of S. zooepidemicus.
- To investigate the specificity of opsonic responses to SzP proteins.
Main Methods:
- Sequencing of SzP genes from 14 Moore and Bryans serovars using polymerase chain reaction (PCR).
- Amino acid sequence comparison to identify variations.
- Opsonization assays using antiserum to the prototype SzPW60 protein.
Main Results:
- Identified two N-terminal variations and a hypervariable (HV) region (residues 106-166) in SzP proteins.
- Discovered proline-glutamic acid-proline-lysine repeats (7-12) in the carboxy terminus.
- Found five distinct HV motifs (HV 1-5) that varied independently.
- Demonstrated that all serovars were opsonized by antiserum to SzPW60, indicating conserved opsonogenic epitopes.
Conclusions:
- Variant SzP motifs can be valuable for epizootiologic and pathogenesis studies of S. zooepidemicus.
- These findings may help determine if S. zooepidemicus populations are unique to specific animal hosts.
- Opsonic responses suggest that protective immunity against SzP is not entirely serovar-specific.