PRELIMINARY EVALUATION OF A MYCOBACTERIUM-TUBERCULOSIS LIPOOLIGOSACCHARIDE (LOS) ANTIGEN IN THE SEROLOGICAL DIAGNOSIS OF TUBERCULOSIS IN HIV-SEROPOSITIVE AND SERONEGATIVE PATIENTS

Objective: To assess the value of detection of specific IgG or IgM antibodies against three polar glycolipids of Mycobacterium tuberculosis in HIV seropositive and seronegative patients with documented active tuberculosis. Design: Using an ELISA test, concentrations of IgM and IgG antibodies against phenolic glycolipid Tb1 (PGL Tb1), 2.3 diacyl trehalose (DAT) and polar lipooligosaccharide (LOS) were measured in the serum of 36 patients with active tuberculosis: 16 tuberculosis patients were coinfected with HIV (TB HIV+), and 20 were HIV seronegative (TB HIV-). 104 control sera were tested: they were collected from 50 healthy blood donors and from 54 asymptomatic HIV seropositive patients. Specificity, sensitivity and predictive positive and negative values were calculated. Results: For the LOS antigen tested, sensitivity, specificity and predictive positive value of specific IgG antibodies were 75%, 95% and 84% respectively among the 36 tuberculosis patients. No significant results were obtained either with the IgM against the LOS antigen or with IgG against the DAT and PGL Tb-1 antigens. Significant sensitivity and positive predictive values were demonstrated only with the ELISA test measuring specific IgG against the LOS antigen. The sensitivity was greater in the TB HIV+ subgroup (94%) as compared with the TB HIV- (60%) subgroup. These results were not related to different potential factors such as the site of disease (pulmonary or extrapulmonary) or by the acid-fast bacteria load as detected by the smear microscopic (Ziehl-Neelsen) examination. Conclusions: The results suggest that of the 3 antigens tested, only the LOS antigen is a potential marker for detecting the development of tuberculosis in HIV patients.