RESEARCH ARTICLE


The Two-Component Regulatory System VicRK is Important to Virulence of Streptococcus equi Subspecies equi



Mengyao Liu, Michael J McClure, Hui Zhu, Gang Xie, Benfang Lei*
Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana 59717, USA


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© Liu et al.; Licensee Bentham Open

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.5/), which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.

* Address correspondence to this author at Department of Veterinary Molecular Biology, Montana State University, P.O. Box 173610, Bozeman, Montana 59717, USA; E-mail: blei@montana.edu


Abstract

This study aims at evaluating the importance of the two-component regulatory system VicRK to virulence of the horse pathogen Streptococcus equi subspecies equi and the potential of a vicK mutant as a live vaccine candidate using mouse infection models. The vicK gene was deleted by gene replacement. The ΔvicK mutant is attenuated in virulence in both subcutaneous and intranasal infections in mice. ΔvicK grows less slowly than the parent strain but retains the ability of S. equi to resist to phagocytosis by polymorphoneuclear leukocytes, suggesting that the vicK deletion causes growth defect. ΔvicK infection protects mice against reinfection with a wild-type S. equi strain. Intranasal ΔvicK infection induces production of anti-SeM mucosal IgA and systemic IgG. These results indicate that VicRK is important to S. equi growth and virulence and suggest that ΔvicK has the potential to be developed as a live S. equi vaccine.