Mechanism of the Rhodococcus equi virulence plasmid-encoded Vap proteins in intramacrophage survival and host tropism

Rhodococcus equi is a soil-dwelling actinobacterium with the ability to parasitize host macrophages and cause pyogranulomatous disease in animals and people. Work from our laboratory determined the complete genome sequence of the pathogen and discovered that it can carry three distinct types of conjugative virulence plasmids designated pVAPA, pVAPB and pVAPN, each associated with a specific animal host (horses, pigs, and ruminants). Epidemiological and experimental evidence using isogenic R. equi bacteria indicated that the virulence plasmid mediates R. equi host tropism. The three virulence plasmid types carry a pathogenicity island (PAI) encoding several members of a virulence-associated protein (Vap) family. One of the Vaps, exemplified by VapA from pVAPA, is essential for virulence by interfering with the maturation of the R. equi-containing vacuole (RCV) and thus promoting intracellular survival. However, the mechanism remains unknown. Each host-associated plasmid type contains a homologous vap PAI which differs in the specific set of vap genes, suggesting that the the different vap gene complement could be at the basis of the species-specific infectivity. The proposed project has two aims: (i) Explore the mechanism of VapA (and its porcine and bovine allelic variants) in intracellular survival in macrophages; and (ii) determine the role of the species-specific vap PAI and the vap multigene family in host tropism. For aim (i) cell biological approaches including Vap protein targeting/localization, co/immunoprecipitation, characterization of the RCV with endosomal markers and proteomic analysis, confocal microscopy and in vivo cell imaging, siRNA knockdown assays, cell knock-out and knock-ins, underpinned by previous data on Vap host cell targets by high-throughput Y2H screens and pathway analysis, protein biochemistry, and bacterial genetics, will be used. For aim (ii) a detailed mutational analysis using genetic constructs with specific components deleted or added, mobilised via conjugation (with an in-house developed technique) to an isogenic context, will be tested in cellular and animal models.

Funding: This project is eligible for a University of Edinburgh 3year PhD studentship or Principal’s Career Development Studentship. ( http://www.ed.ac.uk/schools-departments/student-funding/postgraduate/uk-eu/university-scholarships/development)

International students should also apply for an Edinburgh Global Research Studentship (http://www.ed.ac.uk/schools-departments/student-funding/postgraduate/international/global/research).

Applications including a statement of interest and full CV with names and addresses (including email addresses) of two academic referees, should be sent to: Liz Archibald, The Roslin Institute, The University of Edinburgh, Easter Bush, Midlothian, EH25 9RG or emailed to [Email Address Removed].

When applying for the studentship please state clearly the title of the studentship and the supervisor/s in your covering letter.

All applicants should also apply through the University’s on-line application system for September 2017 entry via http://www.ed.ac.uk/studying/postgraduate/degrees/index.php?r=site/view&id=831


Applicants for the Principal’s career development studentship must also complete the specific on-line application form at http://www.ed.ac.uk/schools-departments/student-funding/postgraduate/uk-eu/university-scholarships/development