B-cell immune responses in HIV positive and HIV negative patients with tuberculosis evaluated with an ELISA using a glycolipid antigen.

The diagnostic value of the PGL-Tb1 enzyme-linked immunosorbent assays (ELISA) was established following a survey study using sera from 220 Tuberculosis patients (including 69 HIV coinfected) and 324 controls. A higher percentage (76.8%) of the HIV-seropositive compared to the HIV-seronegative (58.9%) TB patients were ELISA positive (p=0.02) with a specificity of 94%. In HIV-positive TB patients, ELISA sensitivity was identical for all sites of disease and antibody levels were not affected by the CD4+ counts, PPD results, age or bacterial yield. Combining data for both the smear microscopy and ELISA maximized sensitivity. The kinetics of anti-PGL-Tb1 antibody was evaluated in cohort studies using sera collected before, during and after treatment for clinical TB for 79 TB patients (including 39 HIV coinfected). Statistically significant ELISA signals were observed in 51.3% of HIV-seropositive TB patients prior to the diagnosis of clinical TB and elevated antibody levels persisting 18 months after the end of antituberculous chemotherapy. Asymptomatic development of antibody also occurred in 22.7% of a cohort of 44 HIV-positive patients with a high risk of tuberculosis, but no correlation was found between persisting elevated antibody levels and progression to active disease. This antibody response in absence of disease, might reflect the control of an incipient tuberculosis infection by antituberculous prophylaxis or through an improved protective immune response associated with antiretroviral therapy.