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Title: Molecular characterisation of a novel lipoglycoprotein from Mycobacterium tuberculosis and Mycobacterium bovis
Author: Michell, Stephen Lloyd
Awarding Body: Imperial College London (University of London)
Current Institution: Imperial College London
Date of Award: 1999
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In Great Britain a recent independent scientific review into bovine tuberculosis concluded that the best prospect for control of TB in the national herd is to develop a vaccine. The secreted antigens of the Mycobacterium tuberculosis complex have received much interest as possible vaccine candidates due to their ability to confer protection against tuberculosis in small animal models. The recent discovery that some of these mycobacterial antigens are glycosylated, a modification ubiquitous in eukaryotic proteins, may provide some novel insights into the properties of these antigens. The antigen MPB70 is the major secreted protein of Mycobacterium bovis, the causative agent of tuberculosis in cattle. It has previously been reported that this antigen, encoded for by the gene mpb70, is present in at least two forms, a 22 kDa unglycosylated form and a 25 kDa glycosylated form. A clone was isolated from an M. tuberculosis H37Rv mycobacterial shuttle cosmid library which expressed both the 22 and 25 kDa antigens. Genetic analysis of this cosmid revealed that the two antigens were encoded by separate genes. The gene encoding the 25 kDa antigen (MPT83), subsequently designated mpt83, is situated 2.4 kb upstream of mpt70 and transcribed in the same direction. Using a mycobacterial expression system and alkaline phosphate (PhoA) fusions, it was shown that MPT83 but not MPT70 is glycosylated by Mycobacterium smegmatis. Moreover, neither fusion protein was glycosylated in E. cW demonstrating that glycosylation of MPT83 was specific to the mycobacterial species. The use of site directed mutagenesis in conjunction with the PhoA reporter system identified both 0 and N-linked glycosylation sites within MPT83. Preliminary investigations into the role of glycosylation in the alteration of immune recognition showed a possible influence of cilycosylation on a T cell epitope of MPT83.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available