New polypeptide comprises an immunogenic portion of a Mycobacterium tuberculosis antigen (or a variant of the antigen differing only by conservative substitutions and/or modifications), in which the antigen comprises one of the 23 amino acid sequences (given in the specification) or the antigen is encoded by: (i) one of the 23 DNA sequences (given in the specification) encoding the 23 amino acid sequences； (ii) sequences hybridising to (i) under moderately stringent conditions, or (iii) sequences complementary to (i) or (ii). Also claimed are: (1) DNA molecules encoding the polypeptide； (2) expression vectors comprising (1)； (3) host cells (optionally E. coli, yeast or mammalian) comprising vector； (4) compositions comprising DNA molecule with one of the 11 nucleotide sequences (given in the specification) and a carrier； (5) fusion proteins comprising polypeptide and known M. tuberculosis antigen or comprising at least two of polypeptides, and (6) vaccines comprising non-specific immune response enhancer (optionally an adjuvant) and polypeptide/DNA/fusion protein/DNA sequence of (C)/polypeptide encoded by sequences of (4) or complementary or hybridising sequences.
