Lung and blood mononuclear cell responses of tuberculosis patients to mycobacterial proteins

Abstract

The differences in specificity of human lung and peripheral lymphocytes for mycobacterial antigens (Ag) need to be evaluated in order to identify vaccine candidates against pulmonary tuberculosis (TB). Therefore, the present study examined the response to low molecular weight secretory proteins of Mycobacterium tuberculosis in bronchoalveolar lavage (BAL) and peripheral blood mononuclear cells (PBMCs) from minimal pulmonary TB and non-TB patients. Ag85A, Ag85B, culture filtrate protein (CFP)-31, CFP-22.5, CFP-21, M. tuberculosis protein-64 and an as yet uncharacterised 19 kDa protein were found to be predominantly recognised by BAL cells of TB patients on the basis of lymphocyte proliferation and significant interferon-gamma release. However, recognition of CFP-8, 6-kDa early secreted antigenic target, CFP-10, CFP-14.5, M. tuberculosis secretory protein-17 and five other as yet uncharacterised low molecular weight polypeptides was found to be high on the basis of lymphocyte proliferation at the level of PBMCs. Furthermore, BAL macrophages, and not blood monocytes, were found to produce nitric oxide (NO) in response to mycobacterial Ags. Among polypeptides predominantly recognised by BAL lymphocytes, only Ag85A and Ag85B were found to induce both NO and interleukin-12 (p40) by alveolar macrophages. In conclusion, the present results indicate heterogeneity in antigen recognition by bronchoalveolar lavage cells and peripheral mononuclear blood cells of minimal tuberculosis patients, and also suggest the utility of antigen 85 complex polypeptides for the development of a future mucosal antituberculous vaccine.