Molecular and immunological analysis of a fibronectin‐binding protein antigen secreted by Mycobacterium leprae

Abstract

By screening a Mycobacterium leprae lambda gt11 genomic DNA library with leprosy-patient sera we have previously identified 50 recombinant clones that expressed novel M. leprae antigens (Sathish et al., 1990). In this study, we show by DNA sequencing and immunoblot analysis that three of these clones express a M. leprae homologue of the fibronectin-binding antigen 85 complex of mycobacteria. The complete gene was characterized and it encodes a 327-amino-acid polypeptide, consisting of a consensus signal sequence of 38 amino acids followed by a mature protein of 289 amino acids. This is the first sequence of a member of the M. leprae antigen 85 complex, and Southern blotting analysis indicated the presence of multiple genes of the 85 complex in the genome of M. leprae. The amino acid sequence displays 75-85% sequence identity with components of the antigen 85 complex from M. tuberculosis, M. bovis BCG and M. kansasii. Furthermore, antibodies to the antigen 85 complex of M. tuberculosis and M. bovis BCG reacted with two fusion proteins containing the amino acid regions 55-266 and 266-327 of the M. leprae protein. The M. leprae 30/31 kDa protein induces strong humoral and cellular responses, as judged by Western blot analysis with patient sera and proliferation of T cells derived from healthy individuals and leprosy patients. Amino acid regions 55-266 and 265-327 both were shown to bind to fibronectin, indicating the presence of at least two fibronectin-binding sites on the M. leprae protein. These data indicate that this 30/31 kDa protein is not only important in the immune response against M. leprae, but may also have a biological role in the interaction of this bacillus with the human host.

Gamma Interferon Responses Induced by a Panel of Recombinant and Purified Mycobacterial Antigens in Healthy, Non-Mycobacterium bovisBCG-Vaccinated Malawian Young Adults

“…Members of the Ag85 complex, which function as fibronectin-binding proteins (55) and as mycolyl transferases (5), are highly conserved in M. bovis BCG, M. leprae, and M. tuberculosis (55). Homologues of Ag85 have been found in all the mycobacterial species from which the PPD preparations tested here were derived (56).…”

Identification of HLA class II-restricted determinants ofMycobacteriumtuberculosis-derived proteins by using HLA-transgenic, class II-deficient mice

“…M. bovis BCG was purchased from the Statens Serum Institut (Copenhagen), recombinant hsp65 of M. tuberculosis was obtained from J. Van Embden (RIVM, Bilthoven, The Netherlands), M. tuberculosis from P. Klatser (Royal Tropical Institute, Amsterdam) and Dick van Soolingen (RIVM), and Ag85 was purified from an early culture filtrate of M. tuberculosis (28).…”

“…Early culture filtrate Ags of mycobacteria, such as the Ag85 family, have been proposed as important candidate vaccine Ags. Like hsp65, Ag85 is frequently recognized by human T cells (28). Therefore, we first analyzed T cell responses to Ag85 in immunized DR3.Ab 0 mice.…”

Fibronectin Attachment Protein Homologue Mediates Fibronectin Binding by Mycobacterium avium subsp. paratuberculosis

“…The antigen 85 complex was the first family of mycobacterial proteins to be identified as having FN-binding activity (1,2,30). Members of this complex are 30-to 31-kDa mycolyltransferase isozymes found within the outer envelope and culture supernatants of mycobacteria.…”