Humoral immune responses of normals and tuberculosis patients to multiple sonicate antigens prepared from the most prevalent strains of Mycobacterium tuberculosis harbouring single copy of IS6110 from South India

The search for newer species-specific antigens from prevalent strains of Mycobacterium tuberculosis (Mtb) associated with active disease will add substantially to improve the presently available diagnostic tools. We studied the protein profiles of 13 sonicate antigens (S1– S13) prepared from the prevalent strains. The humoral immune response was also studied in 30 normal and 30 tuberculosis (TB) patients. The sonicate antigens S10 and S12 showed maximum differential protein bands in low molecular mass region of 10–30 kDa on SDS–PAGE. Our ELISA results showed significant increase in Mtb-specific IgG antibodies in TB plasma for H37Rv, followed by PPD, S1 and S10 antigens. Immunoblot analysis of S10 antigen showed specific recognition pattern at low molecular mass region by TB plasma alone with 12–77% positivity of protein bands. Thus the sonicate antigen S10 was found to be discriminatory by ELISA and Western blot and hence a good candidate for further purification of its individual proteins to be evaluated for diagnosis