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Biomedical subjects

G Hewinson

Publications and source records attributed to G Hewinson.

10 recordsLinked to original sources
PubMed2006

Introduction of bovine tuberculosis to north-east England by bought-in cattle.

The source of bovine tuberculosis was investigated in 31 herds in north-east England that experienced confirmed breakdowns between January 2002 and June 2004; nine of the herds had been restocked after the UK outbreak of foot-and-mouth disease in 2001. In all but one of the breakdowns the most likely source of infection was identified as one or more purchased animals. In 17 of the breakdowns, reactor animals were traced to herds from which the same combination of spoligotype and variable number tandem repeats was isolated, and in five breakdowns a different spoligotype was isolated. The most likely sources were located in Wales and the west and north of England, and included a Cheshire herd that was the most likely source of nine of the breakdowns. Three breakdowns were traced to Irish imports. Reactors in five of the breakdowns included homebred as well as purchased animals, providing evidence for the likely spread of the disease within the herds. The lack of geographical clustering of molecular types pointed to the overwhelming source of infection being cattle that had been bought-in.

Animals↗
PubMed2005

Advanced granulomatous lesions in Mycobacterium bovis-infected cattle are associated with increased expression of type I procollagen, gammadelta (WC1+) T cells and CD 68+ cells.

The pathognomonic characteristic of tuberculosis (TB) is the formation of a tuberculous granuloma. The objective of this study was to classify lymph node granulomas from experimentally infected calves into different histopathological stages and characterize them further by studying cell types and markers of fibrosis associated with each of the stages. Four stages of granuloma were identified and mRNA and protein expression for cell markers, cytokines and pro-fibrotic markers were studied by immunohistochemistry (IHC) and in-situ hybridization (ISH). In advanced stage granulomas, there was an increase in the expression of TGF-beta, and of type I procollagen as demonstrated by IHC and ISH. As the granulomas advanced, there were fewer CD3+T cells and they tended to be more prominent towards the periphery of the lesions, with a steady increase in the number of CD68+ cells and gammadelta (WC1+) T cells. Granuloma classification and application of cell cytokine markers will assist in improving understanding of the pathogenesis of bovine TB and may help to identify the immunopathology of active disease versus contained or inactive disease. Such disease correlates may help to inform the development of improved diagnostic methods and support vaccine development programmes.

Animals↗
PubMed2004

First isolation of Mycobacterium microti (Llama-type) from a dog.

We report the first isolation of Mycobacterium microti from a dog with lesions of acute peritonitis. The isolate was demonstrated to be M. microti of Llama-Type by spoligotyping. Epidemiological implications of the isolation of this possibly zoonotic agent from a dog are discussed.

Acute Disease↗
PubMed2003

DNA injection in combination with electroporation: a novel method for vaccination of farmed ruminants.

Injection of plasmid DNA encoding antigens into rodents followed by electroporation improved the immune response when compared with injection without electroporation (Widera et al. J Immunol 2000;164:4635-40; Zucchelli et al. J Virol 2000;74:11598-607; Kadowaki et al. Vaccine 2000;18:2779-88). The present study describes the extension of this technology to farm animals, by injecting plasmid DNA encoding mycobacterial antigens (MPB70, Ag85B and Hsp65) into the muscles of goats and cattle using two different types of electrodes, both allowing DNA delivery at the site of electroporation. The animals were vaccinated under local anaesthesia without any observed immediate or long-term distress or discomfort, or any behavioural signs of muscle damage or pathological changes after the electroporation. DNA-injected and electroporated goats showed increased humoral response after the primary vaccination when compared with nonelectroporated animals. Improved T-cell responses following electroporation were observed in hsp65 DNA-vaccinated cattle. DNA injection with or without electroporation did not compromise the specificity of the tuberculin skin test. In conclusion, a protocol applying in vivo electroporation free of side effects to farmed ruminants was established. In addition, we show that DNA vaccination in combination with electroporation can improve the primary immune responses to the encoded antigens.

Animals↗
PubMed2002

A new evolutionary scenario for the Mycobacterium tuberculosis complex.

The distribution of 20 variable regions resulting from insertion-deletion events in the genomes of the tubercle bacilli has been evaluated in a total of 100 strains of Mycobacterium tuberculosis, Mycobacterium africanum, Mycobacterium canettii, Mycobacterium microti, and Mycobacterium bovis. This approach showed that the majority of these polymorphisms did not occur independently in the different strains of the M. tuberculosis complex but, rather, resulted from ancient, irreversible genetic events in common progenitor strains. Based on the presence or absence of an M. tuberculosis specific deletion (TbD1), M. tuberculosis strains can be divided into ancestral and "modern" strains, the latter comprising representatives of major epidemics like the Beijing, Haarlem, and African M. tuberculosis clusters. Furthermore, successive loss of DNA, reflected by region of difference 9 and other subsequent deletions, was identified for an evolutionary lineage represented by M. africanum, M. microti, and M. bovis that diverged from the progenitor of the present M. tuberculosis strains before TbD1 occurred. These findings contradict the often-presented hypothesis that M. tuberculosis, the etiological agent of human tuberculosis evolved from M. bovis, the agent of bovine disease. M. canettii and ancestral M. tuberculosis strains lack none of these deleted regions, and, therefore, seem to be direct descendants of tubercle bacilli that existed before the M. africanum-->M. bovis lineage separated from the M. tuberculosis lineage. This observation suggests that the common ancestor of the tubercle bacilli resembled M. tuberculosis or M. canettii and could well have been a human pathogen already.

Base Sequence↗
PubMed2001

Molecular typing of Mycobacterium bovis isolates from Cameroon.

In order to gain a better understanding of the molecular epidemiology of Mycobacterium bovis isolates in Cameroon, 75 isolates of M. bovis collected in three provinces of northern Cameroon were studied by spoligotyping. For 65 of these isolates, typing was also carried out by pulsed-field gel electrophoresis (PFGE) with DraI, and 18 of the isolates were also typed by restriction fragment length polymorphism (RFLP) analysis with probe IS6110-RHS. Molecular typing of the isolates by these techniques revealed a high degree of homogeneity, with 10 spoligotypes for 75 isolates, four PFGE profiles for 65 isolates, and three RFLP types for 18 isolates. Some types were present in the three different provinces, while some were confined to one or two areas. These results suggest that geographical mapping of M. bovis strains could be helpful for the control of bovine tuberculosis at the regional level. An interesting feature of all the spoligotypes was the absence of spacer 30, suggesting a common origin for all of the Cameroon isolates tested; an evolutionary scenario for the isolates is discussed. In addition, a comparison of the three techniques showed that for M. bovis strain differentiation in Cameroon and in surrounding countries, spoligotyping would be a more discriminating and practical tool for molecular typing than the other two techniques used in this study.

Animals↗
PubMed2001

Genetic diversity among Mycobacterium bovis isolates: a preliminary study of strains from animal and human sources.

Mycobacterium bovis has the broadest host range of species in the Mycobacterium tuberculosis complex and is responsible for disease in humans and diverse animal species. We report on genotypic differences at multiple loci among 13 isolates derived from a range of human and animal infections. All isolates were classified as M. bovis by phenotypic analysis but could be subdivided into five distinct genotypes based on polymorphisms at the pncA and oxyR loci, the status of the RD5 deletion region, and the spoligotype pattern. These findings suggest the existence of a spectrum of strains with genotypic characteristics between those of M. tuberculosis and M. bovis.

Aged↗
PubMed1997

Mutagenesis of an immunodominant T cell epitope can affect recognition of different T and B determinants within the same antigen.

The effects of mutagenesis of residues of a major T cell epitope were investigated in order to expand knowledge from synthetic peptides to the naturally processed antigen. The impact of substitutions within the core of the immunodominant p61-80/PT19 mycobacterial epitope was ascertained in respect of this epitope per se, or of a C-terminal (140-159) overlapping T/B epitope and of a conformational B epitope. The core substitution A71L impaired T immunogenicity of the target epitope within the protein, but not in the peptide, whereas the N73A substitution impaired the responses in both instances. Notably, each of these single amino acid mutations abrogated the T but not the B immunogenicity of the C-terminal epitope. Furthermore, mutation of five core residues (71-76) also ablated expression of a monoclonal antibody defined conformational B epitope. In conclusion, immunological analysis of mutated proteins revealed functional associations between topographically distinct antigenic determinants which may account for the previously observed differences in the specificity of immune responses between immunised and infected hosts.

Animals↗