Publications

Enterohaemorrhagic Escherichia coli (EHEC) comprise a group of animal and zoonotic pathogens of worldwide importance. Our previous research established that intestinal colonization of calves by EHEC serotypes O5?:?H– and O111?:?H– requires EHEC factor for adherence (Efa-1), also known as lymphostatin (LifA). Towards an understanding of the mode of action of Efa-1/LifA, chromosomal in-frame deletions of predicted glycosyltransferase (DXD) and cysteine protease (CHD) motifs were created in a ?stx1 derivative of EHEC O26?:?H–. The magnitude and duration of faecal excretion of EHEC O26?:?H– were significantly reduced by null mutation of efa-1/lifA, but were not impaired by ?DXD or ?CHD mutations, in contrast to observations made with truncated Efa-1/LifA mutants of Citrobacter rodentium in mice. Although C. rodentium Efa-1/LifA influences the induction of colonic hyperplasia in mice, EHEC O26?:?H– Efa-1/LifA was not required for fluid accumulation or neutrophil recruitment in bovine ileal loops. In contrast to observations with EHEC O5?:?H– or O111?:?H– mutants, inactivation of efa-1/lifA in EHEC O26?:?H– did not significantly affect adherence or secretion of type III secreted proteins that play pivotal roles in calf colonization. Lymphostatin activity could not be reliably demonstrated in lysates of EHEC O26?:?H–; however, deletion of the glycosyltransferase and cysteine protease motifs in Efa-1/LifA from enteropathogenic E. coli O127?:?H6 abolished lymphostatin activity. Our data uncouple the role of Efa-1/LifA in calf colonization from effects on type III secretion and reinforce the potential for pathotype- and serotype-specific phenotypes.

The early identification of classical swine fever epizootics is hampered by difficulties in recognising early signs of infection, due to a lack of specific clinical signs. In addition many textbook descriptions of CSF are based on observations of disease caused by historic, mainly genotype 1, strains. Our objective was to improve our knowledge of the diverse range of signs that different CSFV strains can cause by characterising the experimental infection of domestic pigs with both a recent strain of CSFV and a divergent strain. Conventional pigs were inoculated with a genotype 2.1 isolate, that caused an outbreak in the UK in 2000, and a genotype 3.3 strain that is genetically divergent from European strains. This latter strain is also antigenically distinct as it is only poorly recognised by the CSFV-specific monoclonal antibody, WH303. Transmission was monitored by use of in-contact animals. Clinical, virological and haematological parameters were observed and an extended macro- and histopathological scoring system allowed detailed characterisation of pathological lesions. Infection with the genotype 2.1 isolate resulted in a similar outcome to other recent genotype 2 European strains, whereas the genotype 3.3 strain produced fewer and delayed clinical signs, notably with little fever. This strain would therefore be particularly difficult to detect in the early stages of infection and highlights the importance of encouraging early submission of samples for laboratory diagnosis. As representatives of recent and divergent CSFV isolates, these strains are good candidates to study the pathogenesis of current CSFV isolates and as challenge models for vaccine development.

A lateral flow device (LFD) for the detection of swine vesicular disease (SVD) virus (SVDV) and differential diagnosis from foot-and-mouth disease (FMD) was developed using a monoclonal antibody (Mab C70). The performance of the LFD was evaluated in the laboratory on suspensions of vesicular epithelia and cell culture passage derived supernatants of SVDV and porcine teschovirus (enterovirus; PEV). The collection of test samples included 157 which were positive for SVDV (84 vesicular epithelial suspensions and 73 cell culture antigens) from suspected cases of vesicular disease in pigs collected from 14 countries between 1966 and 2008 and 663 samples which were either shown to be negative for SVDV and FMD virus (FMDV) or else collected from healthy pigs or demonstrated to be positive for FMDV, PEV or vesicular exanthema (VEV) and collected from 16 countries between 1965 and 2008 or else were derived from experimental animals. Three further samples containing vesicular stomatitis virus (VSV) were also tested. The diagnostic sensitivity of the LFD for SVDV was similar at 82% compared to 86% obtained by the reference method of antigen ELISA, and the diagnostic specificity was 100% compared to 99.7% for the ELISA. The device recognized virus strains of each of the known genotypes of the sole SVDV serotype. Reactions with FMDV, VEV, VSV and PEV which can produce clinically indistinguishable syndromes in pigs, did not occur. These data illustrate the potential for the LFD to be used next to the animal for providing rapid and objective support to veterinarians in their clinical judgment of vesicular disease in pigs and for the specific pen-side diagnosis of SVD and differential diagnosis from FMD.

Equine rhinitis A virus (ERAV) shares many features with foot-and-mouth disease virus (FMDV) and both are classified within the genus Aphthovirus of the family Picornaviridae. ERAV is used as a surrogate for FMDV research as it does not require high-level biosecurity. In contrast to FMDV, which uses integrins as cellular receptors, the receptor for ERAV has been reported to involve the sugar moiety sialic acid. This study confirmed the importance of sialic acid for cell entry by ERAV and reports the crystal structure of ERAV particles complexed with the receptor analogue 3?-sialyllactose. The receptor is attached to the rim of a capsid pit adjacent to the major immunogenic site and distinct from the sialic acid binding site used by a related picornavirus, the cardiovirus Theiler's murine encephalitis virus. The structure of the major antigenic determinant of the virus, previously identified from antibody escape mutations, is also described as the EF loop of VP1, which forms a hairpin stretching across the capsid surface close to the icosahedral fivefold axis, neighbouring the receptor-binding site, and spanning two protomeric units.