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;
• contacting cells of the population with at least two different antigens, wherein the antigens are isolated antigenic segments of two different polypeptides of the Mycobacterium tuberculosis-complex that are not encoded by BCG, including at least one isolated polypeptide antigenic segment selected from the group consisting of (i) a first amino acid sequence that is an antigenic segment of MTBN4 (SEQ ID NO:
• 4) and (ii) a second amino acid sequence that is identical to said first 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 different antigens, wherein CD4 T lymphocytes from a subject that has been infected by Mycobacterium tuberculosis-complex respond to the contacting with said at least two different antigens, and CD4 T lymphocytes from a subject vaccinated with the BCG strain of Mycobacterium bovis but not infected by Mycobacterium tuberculosis-complex do not respond to the contacting with said at least two different antigens.