GUINEA-PIG CELLULAR IMMUNE-RESPONSES TO PROTEINS SECRETED BY MYCOBACTERIUM-TUBERCULOSIS

To study the immunological activity of proteins secreted by Mycobacter ium tuberculosis, we carried out comparative studies in guinea pigs in fected intravenously with 2.5 x 10(3) CFU of this organism or with 2.5 x 10(4) CFU of Mycobacterium bovis BCG. Groups of infected guinea pig s were skin tested with fractions of secreted proteins covering well-d efined narrow-molecular-mass regions, or such fractions were used for lymphocyte stimulation experiments. The lymphocyte stimulation experim ents showed that the fraction containing proteins with molecular masse s below 10 kDa had a superior stimulating capacity in tuberculous guin ea pigs whereas the 24- to 30-kDa fraction gave significantly higher s kin reactions in this group compared with BCG-vaccinated guinea pigs. A precise mapping within the region from 23 to 35 kDa by using a combi nation of narrow overlapping fractions and purified proteins enabled t he identification of the 24-kDa antigen MPT64 asa molecule specific fo r tuberculous infection. Thus, MPT64 is a promising candidate for a sp ecific diagnostic skin test reagent for human tuberculosis.