Cloning of a Mycobacterium tuberculosis gene encoding a purifed protein derivative protein that elicits strong tuberculosis-specific delayed-type hypersensitivity

The purified protein derivative (PPD) skin test has been used for the diagn osis of tuberculosis for more than 75 years. However, the test lacks specif icity because all mycobacteria share antigens present in PPD, Therefore, se nsitization with nontuberculous pathogenic or with environmental nonpathoge nic mycobacteria can lead to positive skin tests. This communication descri bes a novel PPD protein present only in tuberculous complex mycobacteria, A recombinant protein was obtained and named DPPD on the basis of the first 4 amino acids of its N-terminus sequence, DPPD elicited delayed-type hypers ensitivity (DTH) in 100% of Mycobacterium tuberculosis-infected guinea pigs but in no animals sensitized with several organisms representative of all members of the Mycobacterium genus. Preliminary results indicate that DPPD induces strong and specific DTH in humans. This work points to the definiti on of a single recombinant M, tuberculosis protein that may be an alternati ve to the PPD test.