Open Access Research article

Rv1985c, a promising novel antigen for diagnosis of tuberculosis infection from BCG-vaccinated controls

Jiazhen Chen123, Sen Wang1, Ying Zhang3, Xiaodi Su2, Jing Wu2, Lingyun Shao1, Feifei Wang2, Shu Zhang1, Xinhua Weng1, Honghai Wang2* and Wenhong Zhang14*

Author Affiliations

1 Department of Infectious Diseases, Huashan Hospital, Fudan University, Shanghai, 200040, China

2 State Key Laboratory of Genetic Engineering, Institute of Genetics, Fudan University, Shanghai, 200433, China

3 Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, 21205, USA

4 Institutes of Biomedical Sciences, Fudan University, Shanghai, 200040, China

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BMC Infectious Diseases 2010, 10:273  doi:10.1186/1471-2334-10-273

Published: 17 September 2010



Antigens 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.


T-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.


Rv1985c 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.


In conclusion, Rv1985c is a novel antigen which can be used to immunologically diagnose TB infection along with other immunodominant antigens among BCG-vaccinated population.