Recognition of ESAT-6 sequences by antibodies in sera of tuberculous nonhuman primates.

Previous work in our laboratory showed that the ESAT-6 protein of Mycobacterium tuberculosis and Mycobacterium bovis induces strong antibody responses in a large proportion ( approximately 90%) of experimentally or naturally infected nonhuman primates. Here, the antibody response to ESAT-6 in tuberculous monkeys was characterized at the epitope level by measuring antibodies to overlapping, synthetic peptides spanning the ESAT-6 sequence. The antibody response against the COOH-terminal portion of the protein was the strongest in both experimentally and naturally infected animals. Moreover, these antibodies became detectable the earliest during experimental infection, suggesting an ordered expansion of ESAT-6-specific B-cell clones in the course of infection. The data support use of synthetic peptides in lieu of the full-length ESAT-6 protein in diagnostic antibody detection assays.