Affects of N-terminal variation in the SeM protein of Streptococcus equi on antibody and fibrinogen binding.
Abstract: The clonal Streptococcus equi causes equine strangles, a highly contagious suppurative lymphadenopathy and rhinopharyngitis. An important virulence factor and vaccine component, the antiphagocytic fibrinogen binding SeM of S. equi is a surface anchored fibrillar protein. Two recent studies of N. American, Japanese and European isolates have revealed a high frequency of N-terminal amino acid variation in SeM of S. equi CF32 that suggests this region of the protein is subject to immunologic selection pressure. The aims of the present study were firstly to map regions of SeM reactive with convalescent equine IgG and IgA and stimulatory for lymph node cells and secondly to determine effects of N-terminal variation on the functionality of SeM. Variation did not significantly affect fibrinogen binding or susceptibility of S. equi to an opsonic equine serum. Linear epitopes reactive with convalescent IgG and mucosal IgA were concentrated toward the conserved center of SeM. However, IgA but not IgG from every horse reacted with at least one peptide that contained variable sequence. Lymph node cells (CD4+) from horses immunized with SeM were strongly responsive to a peptide (alphaalpha36-138) encoding the entire variable region. SeM (CF32) specific mouse Mab 04D11 which reacted strongly with this larger peptide but not with shorter peptides within that sequence reacted strongly with whole cells of S. equi CF32 but only weakly with cells of any of 14 isolates of S. equi expressing different variants of SeM. These results in combination suggest that N-terminal variation alters a conformational epitope of significance in mucosal IgA and systemic T cell responses but does not affect antibody mediated phagocytosis and killing.
Copyright (c) 2009 Elsevier Ltd. All rights reserved.
Publication Date: 2009-12-14 PubMed ID: 20005857DOI: 10.1016/j.vaccine.2009.11.064Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research focuses on understanding the impact of variations in the N-terminal section of the SeM protein of Streptococcus equi, a bacterium causing a severe equine disease, on its interaction with antibodies and fibrinogen. The study concluded that N-terminal variation appears to influence the immune response but does not affect the bacteria’s susceptibility to certain defenses.
Aim of the Study
- The research aimed to identify areas of the SeM protein that respond to specific equine antibodies (IgG and IgA) and stimulates lymph node cells.
- It also aimed to understand the impact of N-terminal variations in the SeM protein on its ability to function normally.
Characteristics of SeM Protein
- SeM is a surface protein found in Streptococcus equi that binds fibrinogen, a blood-clotting protein, and plays a significant role in the bacterium’s resistance to immune clearance (being a part of the virulence factor).
- The N-terminal section of this protein was found to have frequent amino acid variations in different isolates of the bacteria; the research suggested that this region of the protein might be under immunologic selection pressure.
Impact of N-terminal Variation
- The study concluded that the variation in the N-terminal section didn’t affect fibrinogen binding or the bacterium’s susceptibility to opsonic equine serum, a substance that enhances phagocytosis.
- Antibody-binding areas (epitopes) were found to be in the conserved center of SeM. Some peptides with variable sequences reacted with at least one type of antibody in every studied horse, but only with IgA and not IgG.
- Lymph node cells from horses immunized with SeM responded strongly to a peptide encoding the entire variable region, pointing towards its immunological importance.
- The study confirmed that N-terminal variation alters the structure of an epitope, which is significant in triggering immune responses, but does not impact the process of phagocytosis and killing by antibodies.
Cite This Article
APA
Timoney JF, DeNegri R, Sheoran A, Forster N.
(2009).
Affects of N-terminal variation in the SeM protein of Streptococcus equi on antibody and fibrinogen binding.
Vaccine, 28(6), 1522-1527.
https://doi.org/10.1016/j.vaccine.2009.11.064 Publication
Researcher Affiliations
- Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546, USA. jtimoney@uky.edu
MeSH Terms
- Animals
- Antibodies, Bacterial / immunology
- Antibodies, Bacterial / metabolism
- Antigens, Bacterial / genetics
- Antigens, Bacterial / immunology
- Antigens, Bacterial / metabolism
- Bacterial Proteins / genetics
- Bacterial Proteins / immunology
- Bacterial Proteins / metabolism
- CD4-Positive T-Lymphocytes / immunology
- Epitopes / immunology
- Female
- Fibrinogen / metabolism
- Genetic Variation
- Horse Diseases / immunology
- Horses
- Immunoglobulin A / immunology
- Immunoglobulin G / immunology
- Mice
- Mice, Inbred BALB C
- Opsonin Proteins / immunology
- Opsonin Proteins / metabolism
- Polymorphism, Genetic
- Protein Binding
- Streptococcal Infections / immunology
- Streptococcal Infections / veterinary
- Streptococcus equi / genetics
- Streptococcus equi / immunology
- Virulence Factors / genetics
- Virulence Factors / immunology
- Virulence Factors / metabolism
Citations
This article has been cited 6 times.- Frosth S, Morris ERA, Wilson H, Frykberg L, Jacobsson K, Parkhill J, Flock JI, Wood T, Guss B, Aanensen DM, Boyle AG, Riihimäki M, Cohen ND, Waller AS. Conservation of vaccine antigen sequences encoded by sequenced strains of Streptococcus equi subsp. equi. Equine Vet J 2023 Jan;55(1):92-101.
- Xu S, Liu Y, Gao J, Zhou M, Yang J, He F, Kastelic JP, Deng Z, Han B. Comparative Genomic Analysis of Streptococcus dysgalactiae subspecies dysgalactiae Isolated From Bovine Mastitis in China. Front Microbiol 2021;12:751863.
- Kanagavel M, Shanmughapriya S, Anbarasu K, Natarajaseenivasan K. B-cell-specific peptides of leptospira interrogans LigA for diagnosis of patients with acute leptospirosis. Clin Vaccine Immunol 2014 Mar;21(3):354-9.
- Velineni S, Timoney JF. Characterization and protective immunogenicity of the SzM protein of Streptococcus zooepidemicus NC78 from a clonal outbreak of equine respiratory disease. Clin Vaccine Immunol 2013 Aug;20(8):1181-8.
- Moloney E, Kavanagh KS, Buckley TC, Cooney JC. Lineages of Streptococcus equi ssp. equi in the Irish equine industry. Ir Vet J 2013;66(1):10.
- Wan J, Weldon E, Ganser G, Morris ERA, Hughes EV, Bordin AI, Heine PA, Hust M, Cohen ND, Gill JJ, Liu M. Immunogenic Streptococcus equi cell surface proteins identified by ORFeome phage display. mSphere 2025 Dec 23;10(12):e0062625.
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