Proteins expressed by mycobacterium tuberculosis and not by BCG and their use as diagnostic reagents and vaccines

A method of in vitro diagnosis that discriminates between infection by Mycobacterium tuberculosis-complex and vaccination by Bacille Calmette Guerin (BCG) strain of Mycobacterium bovis comprising:

• providing a population of cells comprising CD4 T lymphocytes from a subject and antigen presenting cells (APC) expressing at least one major histocompatibility complex (MHC) class II molecule expressed by said subject;
• contacting cells of the population with at least two different antigens, wherein the antigens are isolated polypeptides of the Mycobacterium tuberculosis-complex that are not encoded by BCG, including at least one isolated polypeptide selected from the group consisting of (i) a first amino acid sequence comprising the sequence of MTBN4 (SEQ ID NO:
• 4), (ii) a second amino acid sequence that is an antigenic segment of MTBN4 and (iii) a third amino acid sequence that is identical to said first or second amino acid sequence but that has conservative substitutions and that retains Mycobacterium tuberculosis-complex specific antigenic properties;
• and
• determining whether or not there has been an immune response to said at least two antigens.