Development of a live, attenuated, potential vaccine strain of R. equi expressing vapA and the virR operon, and virulence assessment in the mouse

Ashley E. Whitehead, Valeria R. Parreira, Joanne Hewson, Johanna L Watson, John F. Prescott

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

Pneumonia caused by Rhodococcus equi remains a significant problem in foals. The objective of this study was to develop a safe and efficacious attenuated strain of R. equi for eventual use in oral immunization of foals. The approach involved expression of vapA in a live, virulence plasmid-negative, strain of R. equi (strain 103-). PCR-amplified fragments of the vapA gene, with and without the upstream genes virR, orf5, vapH, orf7 and orf8 (orf4-8), were cloned into a shuttle vector pNBV1. These plasmids, named pAW48A and pAWVapA respectively, were electroporated into strain 103-. The presence of the recombinant vectors in the attenuated strain (103-) and the integrity of the inserted genes were confirmed, and both constructs expressed VapA. The virulence of the two strains was compared to that of wild type R. equi 103+ and negative controls by their intravenous inoculation into mice, followed by examination of liver clearance 4 days later. Mice inoculated with R. equi 103-, 103-/pAWVapA and 103-/pNBV1 completely cleared infection, whereas strain 103-/pAW48A persisted in 47% of mice.

Original languageEnglish (US)
Pages (from-to)479-484
Number of pages6
JournalVeterinary Immunology and Immunopathology
Volume145
Issue number1-2
DOIs
StatePublished - Jan 15 2012

Keywords

  • Mice
  • Plasmid construct
  • Rhodococcus equi
  • Vaccination
  • VapA
  • VirR operon

ASJC Scopus subject areas

  • Immunology
  • veterinary(all)

Fingerprint Dive into the research topics of 'Development of a live, attenuated, potential vaccine strain of R. equi expressing vapA and the virR operon, and virulence assessment in the mouse'. Together they form a unique fingerprint.

  • Cite this