Extensive sequence homology between the Mycobacterium leprae LSR (12 kDa) antigen and its Mycobacterium tuberculosis counterpart

The Mycobacterium leprae LSR (12 kDa) protein antigen has been reported to mimic whole cell M. leprae in T cell responses across the leprosy spectrum. In addition, B cell responses to specific sequences within the LSR antigen have been shown to be associated with immunopathological responses in lepr osy patients with erythema nodosum leprosum. We have in the present study a pplied the M. lepiae LSR DNA sequence as query to search for the presence o f homologous genes within the recently completed Mycobacterium tuberculosis genome database (Sanger Centre, UK). By using the BLASTN search tool, a ho mologous M. tuberculosis open reading frame (336 bp), encoding a protein an tigen of 12.1 kDa, was identified within the cosmid MTCY07H7B.25. The gene is designated Rv3597c within the M. tuberculosis H37Rv genome. Sequence ali gnment revealed 93% identity between the M. lepiae and M. tuberculosis anti gens at the amino acid sequence level. The finding that some B and T cell, epitopes were localized to regions with amino acid substitutions may accoun t for the putative differential responsiveness to this antigen in tuberculo sis and leprosy. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.