Distribution of antibody titres against phenolic glycolipids from Mycobacterium tuberculosis in the sera from tuberculosis patients and healthy controls.

Sera from tuberculosis (TB) patients and healthy controls were tested by ELISA for their antibody titres against the two major phenolic glycolipids (PGLs) of Mycobacterium tuberculosis, PGL-tbO (a 1:3 mixture of PGL-tb1 and its analogue whose phthiocerol moiety is phenolphthiotriol A) and PGL-tbK. Both PGL-tbs were shown to be specific to M. tuberculosis, and the profiles of serum anti-PGL-tbK titres revealed that PGL-tbK, like PGL-tb1, was fairly widely distributed among strains of M. tuberculosis. Even when these two PGL-tbs were used, however, the rate of ELISA-positives was not very high among TB patients, which is probably explained by the nature of the disease. Moreover, a considerable number of sera from healthy controls, especially from younger age groups, had high anti-PGL-tb titres, which implies that environmental exposure to M. tuberculosis is much higher than has been estimated from the actual TB cases. The ELISA system using these species-specific PGL-tb antigens may be useful for the survey of TB infection, since it gives more direct information on TB infection than the PPD skin test.