Although the
tuberculin test has aided in the diagnosis of
tuberculosis for more than 85 years, its interpretation is difficult particularly because sensitization with non-tuberculous mycobacteria leads to false positive tests. Using the guinea pig model of
tuberculosis, we have recently described a recombinant
antigen (
DPPD) that could circumvent this problem. The
DPPD gene is unique to the M.
tuberculosis complex organisms and is absent in the organisms representative of all other members of the Mycobacterium genus. Moreover,
DPPD induced strong DTH in 100% of the guinea pigs infected with M.
tuberculosis and in none of the guinea pigs immunized with nine different species of Mycobacterium. Here we present results of a clinical investigation using
DPPD. Mantoux test using both
PPD and
DPPD was initially performed in 26 patients with confirmed
pulmonary tuberculosis and in 25 healthy
PPD negative individuals. The results indicated that both
PPD and
DPPD elicited DTH in 24 out of the 26 patients. No DTH was observed in any of the
PPD negative individuals. In addition, a small clinical trial was performed in a population of 270 clinically healthy and randomly selected individuals.
DPPD produced a bimodal histogram of skin reaction size and
PPD produced a skewed histogram. Because the
DPPD gene is not present in non-tuberculous bacilli, these results suggest that this molecule can be an additional tool for a more specific diagnosis of
tuberculosis.