CHARACTERIZATION OF THE DELAYED-TYPE HYPERSENSITIVITY-INDUCING EPITOPE OF MPT64 FROM MYCOBACTERIUM-TUBERCULOSIS

Mycobacterium tuberculosis secretes several proteins into the extracel lular environment, some of which are restricted to the M. tuberculosis complex. One of these antigens is MPT64. Recently, the authors showed that native as well as recombinant MPT64 is able to distinguish betwe en an M. tuberculosis infection and a BCG Danish 1331 vaccination. Imp roved distinction between tuberculin purified protein derivative (PPD) sensitivity conferred by an M. tuberculosis infection and that induce d by a BCG vaccination or infection with environmental mycobacteria wo uld be useful in the control of tuberculosis. In this study, the autho rs report the mapping and characterization of a Dth-inducing epitope b y the use of synthetic peptides in guinea-pigs vaccinated with BCG Dan ish 1331 or Tokyo. Studies with overlapping synthetic peptides have pi npointed the biological activity to a single Dth-inducing epitope at t he carboxyterminal region of MPT64 consisting of 15 residues between a mino acids Gly-173 and Ala-187, the core epitope (CE15). A fine mappin g using truncated versions of CE15 indicates the epitope is restricted to 13 residues between amino acids Val-174 to Glu-186. However, the o ptimal Dth reactivity is obtained by CE15. Different modifications of CE15 revealed that a lysine tree construction improves the skin reacti vity to a maximum level approaching that of the reactivity to tubercul in PPD.