Abstract
BackgroundAntigens encoded in the region of difference (RD) of Mycobacterium tuberculosis constitute a potential source of specific antigens for immunodiagnosis. In the present study, recombinant protein Rv1985c from RD2 was cloned, expressed, purified, immunologically characterized and investigated for its potentially diagnostic value for tuberculosis (TB) infection among BCG-vaccinated individuals.MethodsT-cell response to Rv1985c was evaluated by IFN-γ ELISPOT in 56 TB patients, 20 latent TB infection (LTBI) and 30 BCG-vaccinated controls in comparison with the commercial T-SPOT. TB kit. Humoral response was evaluated by ELISA in 117 TB patients, 45 LTBI and 67 BCG-vaccinated controls, including all those who had T-cell assay, in comparison with a commercial IgG kit.ResultsRv1985c was specifically recognized by cellular and humoral responses from both TB and LTBI groups compared with healthy controls. Rv1985c IgG-ELISA achieved 52% and 62% sensitivity respectively, which outperformed the sensitivity of PATHOZYME-MYCO kit (34%) in detecting active TB (P = 0.011), whereas IFN-γ Rv1985c-ELISPOT achieved 71% and 55% sensitivity in detecting active and LTBI, respectively. Addition of Rv1985c increased sensitivities of ESAT-6, CFP-10 and ESAT-6/CFP-10 combination in detecting TB from 82.1% to 89.2% (P = 0.125), 67.9% to 87.5% (P < 0.001) and 85.7% to 92.9% (P = 0.125), respectively.ConclusionsIn conclusion, Rv1985c is a novel antigen which can be used to immunologically diagnose TB infection along with other immunodominant antigens among BCG-vaccinated population.
Highlights
Antigens encoded in the region of differentiation (RD) of M. tuberculosis constitute a potential source of specific antigens for immunodiagnosis [5,6,7,8,9,10]
Specific T-cell response to Rv1985c in TB and latent TB infection (LTBI) groups compared with healthy controls The spot forming units (SFU) of TB and LTBI groups were significantly higher than that of HC group (P < 0.001) (Figure 2), Figure 2 ELISPOT showed that peripheral blood mononuclear cells (PBMC) from both TB and LTBI groups developed stronger IFN-g producing response to Rv1985c antigens than those from HC group
Serological response to Rv1985c in TB and LTBI groups compared with healthy controls Figure 4 showed the IgG (4A) and IgM (4B) antibody optical density (OD) values to Rv1985c obtained from 117 TB patients, 45 LTBI and 67 healthy controls
Summary
Antigens encoded in the region of difference (RD) of Mycobacterium tuberculosis constitute a potential source of specific antigens for immunodiagnosis. Recombinant protein Rv1985c from RD2 was cloned, expressed, purified, immunologically characterized and investigated for its potentially diagnostic value for tuberculosis (TB) infection among BCG-vaccinated individuals. One-third of the world population is infected with Mycobacterium tuberculosis. Among people infected with TB bacilli, about 5-10% will become sick or infectious at some time during their life [2]. People with HIV and TB infection are much more likely to develop active TB [1]. Antigens encoded in the region of differentiation (RD) of M. tuberculosis constitute a potential source of specific antigens for immunodiagnosis [5,6,7,8,9,10].
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