T-cell recognition of iron-regulated culture filtrate proteins of Mycobacterium tuberculosis in tuberculosis patients and endemic normal controls

• Published in: Indian journal of medical microbiology 2012-07, Vol.30 (3), p.323-331
• Main Authors: Duggirala, S, Venu, K, Subhakar, K, Sritharan, M
• Format: Article
• Language: English
• Subjects: Colleges & universities; Culture filtrate proteins; Cytokines; Disease; ESAT proteins; Free radicals; gamma -Interferon; Geographical distribution; Hospitals; IFN-γ; Immune response; Influence; Iron; Life sciences; Lung; lymphocyte transformation test; Lymphocytes T; M. tuberculosis; Monoclonal antibodies; Mycobacterium tuberculosis; Nitric oxide; Proteins; Statistical analysis; Tuberculosis; Vaccines
• ISSN: 0255-0857; 1998-3646
• DOI: 10.4103/0255-0857.99495

Background: Culture filtrate proteins (CFPs) of Mycobacterium tuberculosis are potential vaccine candidates. Objective: The aim was to study the influence of iron levels on CFPs and assess the immuno-protective potential of defined antigenic fractions from high (8 μg Fe/mL) and low iron (0.02 μg Fe / mL) cultures of M. tuberculosis. Materials and Methods: The CFPs of M. tuberculosis from high (CFP-high) and low (CFP-low) iron conditions were first compared to identify iron-regulated proteins and then fractionated to obtain ten antigen pools (CF-Ags H1- H5 and L1-L5) that were used to assess the immune response of TB patients and normal healthy controls. Results: Iron limitation resulted in the up-regulation of two novel iron-regulated low-molecular-weight proteins Irp-1 (in CF-Ag L4) and Irp-2 (in CF-Ag L5) and repression of two ESAT proteins (identified with monoclonal antibody HYB 76.8). The median stimulation indices (SIs) against most of the CF-Ags were high in pulmonary TB patients. The CF-Ags L1 and L2 showed statistically significant SI (P values of 0.0027 and 0.0029 respectively); the % case recognition was high with these antigens as well as with L4 (P = 0.0275). IFN-γ in response to these CF-Ags was significantly high in the endemic normals; maximal expression was seen with CF-Ag L5 (median value of 233 pg mL-1) that was higher than the corresponding H5 (140 pg mL-1) and H3 and L3 (205 and 206 pg mL-1 respectively). Conclusions: CF-Ags L5, H3 and L3 showed immuno-protective potential in this geographical location.