Lack of Response to HBHA in HIV-Infected Patients with Latent Tuberculosis Infection.

Heparin-binding haemagglutinin ( HBHA) has been proposed as an immunological biomarker for discriminating active tuberculosis ( TB) from latent TB infection ( LTBI) and to identify those at higher risk of progressing to active disease. Few data are available in immune-compromised patients, which are those with increased risk of TB reactivation. The aim of this stusy was to evaluate the immune response to HBHA in HIV-infected subjects with LTBI ( HIV- LTBI) or active TB ( HIV- TB) in comparison with the immune response to additional Mycobacterium tuberculosis ( Mtb) or HIV and CMV antigens. The responses are evaluated in relation to TB status and in the LTBI subjects with the progression to active TB within 2 years. Forty-one HIV-infected antiretroviral-naïve subjects were prospectively enrolled: 18 were HIV- TB and 23 HIV- LTBI. Whole blood was in vitro stimulated overnight with several antigens and mitogen. Interferon- γ response in the harvested plasma was evaluated by ELISA. Despite that CD4 cell count was significantly different between HIV- LTBI and HIV- TB, no differences were observed in response to Mtb- or HIV-specific antigens. Differently, low responses to HBHA were observed in both HIV- LTBI and HIV- TB subjects. Importantly, none of the six HIV- LTBI responding to HBHA developed TB, while two of 17 non- HBHA responders developed active disease. HIV- TB-coinfected subjects, regardless of their TB status, showed low responses to HBHA despite maintaining detectable responses to other antigens; moreover, among the HIV- LTBI, the lack of HBHA responses indicated an increased risk to develop active TB. These results, although preliminary, suggest that a positive response to HBHA in HIV- LTBI correlates with Mtb containment. [ABSTRACT FROM AUTHOR]