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Infect. Immun., 01 1997, 16-23, Vol 65, No. 1
C Manca, K Lyashchenko, HG Wiker, D Usai, R Colangeli and ML Gennaro
Proteins that are actively secreted by Mycobacterium tuberculosis generate
immune responses in the infected host. This has prompted the
characterization of protein components of mycobacterial culture filtrates
to develop subunit vaccines and immunodiagnostic reagents. Fractionation of
filtrates of M. tuberculosis cultures has yielded an abundant protein
called MPT63, which has an apparent molecular mass of 18 kDa. We report the
molecular cloning and nucleotide sequence of the mpt63 gene, purification
of recombinant MPT63 antigen from Escherichia coli cells, and serological
characterization of MPT63. Nucleotide sequence analysis of mpt63 identified
an open reading frame encoding a protein of 159 amino acids (aa) consisting
of a 29-aa secretion signal peptide and a 130-aa mature MPT63 protein.
Recombinant MPT63 protein, purified from E. coli cells, and native MPT63,
purified from M. tuberculosis culture filtrates, were indistinguishable in
serological assays. Thus, the recombinant protein constitutes a valuable
reagent for immunological studies. MPT63 evoked humoral immune responses in
guinea pigs infected with virulent M. tuberculosis by the aerosol route.
The mpt63 gene is found only in species of the M. tuberculosis complex, as
shown by DNA hybridization experiments. Moreover, polyclonal antibody
against MPT63 does not cross-react with proteins of a common environmental
mycobacterial species, Mycobacterium avium. The absence of cross-reactive
epitopes makes MPT63 an attractive candidate as an M. tuberculosis
complex-specific diagnostic reagent. In particular, evaluation of MPT63 as
an M. tuberculosis complex-specific reagent for diagnostic skin testing is
under way.
Copyright © 1997, American Society for Microbiology
Molecular cloning, purification, and serological characterization of MPT63, a novel antigen secreted by Mycobacterium tuberculosis
Public Health Research Institute, New York, New York 10016, USA.
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