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Five distinct glycolipids were readily detected in isolates of Mycobacterium tuberculosis. Spectroscopic methods and chemical degradation techniques allowed the structural identification of four of these glycolipids. The specific phenolic glycolipid antigen previously characterized from the Canetti strain was found in all the strains examined, with identical structural features (triglycosyl phenol phthiocerol dimycocerosate). The other three glycolipids identified were acylated trehaloses: penta-acyl trehalose (containing phthienoyl substituents), tetra-acyl trehalose 2'-sulphate (with C40-C50 hydroxyphthioceranoyl substituents) and diacyl trehalose 2'-sulphate (with C16 and C18 substituents). The two latter glycolipids as well as the phenolic glycolipid immunoreacted with whole-cell antiserum, indicating their surface location. The occurrence of these glycolipid antigens in recent clinical isolates suggests their possible utilization in the serodiagnosis of tuberculosis and the rapid identification of M. tuberculosis with specific antisera.

Immunoglobulin G (IgG) and IgM antibodies against the SL-IV antigen of Mycobacterium tuberculosis in the sera of patients with tuberculosis with negative serology for human immunodeficiency virus (HIV) infection (TB group; n = 97), patients with tuberculosis with positive serology for HIV infection (TB-HIV group; n = 59), and healthy controls (n = 289) were determined by enzyme-linked immunosorbent assay. All sera were obtained at the onset of tuberculosis, i.e., when clinical symptoms appeared. Clinical specimens were collected and cultured for the isolation of M. tuberculosis, and treatment with antituberculous drugs was started. Sera were also obtained from patients in the TB group at fixed intervals during treatment; sera were available from 13 patients in the TB-HIV group before the onset of tuberculosis. The best specificity and positive predictive value were obtained with the IgG assays. In the IgG assays at specificities above 96.0%o, the sensitivities of the tests were 45.3 and 72.8% for the TB and TB-HIV groups, respectively, and the sensitivity was 51.9% when data from both groups were combined for analysis. For the TB group, results of this study indicated that the levels of IgG antibodies remain high during treatment. Thus, repetitive serological assays may not be useful for treatment follow-up. In the TB-HIV group, 12 of 13 patients had IgG-specific antibodies against the SL-IV antigen between 1 and 30 months before the onset of tuberculosis, so we suggest that the IgG antibody assay against SL-IV may be helpful for identifying tuberculosis in patients infected with HIV.

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