Comparison of antibody responses to seventeen antigens from Mycobacterium tuberculosis

The detection of Mycobacteriumtuberculosis (MTB)-specific human antibodies has been an important diagnostic aid in the diagnosis of TB, especially for the bacterium-negative TB. The humoral antibody responses to different antigens of M.tuberculosis (MTB) are heterogeneous in active TB patients. Hence, detection of antibody responses to several MTB antigens may improve the sensitivity and specificity of serological diagnosis of active TB.

Seventeen MTB antigens (38kD, 16kD, Ag85A, Ag85B, MPT32, MPT63, MPT64, Mtb39, MTB48, Mtb81, MTC28, Rv1009, ESAT6, CFP10, CFP10-ESAT6, katG, and LAM) were prepared by cloning, expression, and purification from E. coli, and their antigenicities were evaluated in the antibody responses of 210 active TB patients (103 sera from smear- or culture-positive patients, and 107 from smear- or culture-negative patients) and 192 healthy control (95 sera from purified protein derivative-negative healthy donors, and 97 sera from BCG-vaccinated individuals) by an enzyme-linked immunosorbent assay (ELISA).

The levels of antibodies against these antigens in bacterium-negative TB patients were significantly higher than that in healthy controls (p<0.001). The sensitivity with individual antigens to detect antibody responses ranged from 55.7 to 82.9%, with the specificity from 62.0 to 92.2%. Importantly, the sensitivity with five antigens (LAM, 38kD, katG, 16kD, and MPT63 or Mtb39) to detect antibody responses reached 69.5% (146/210), with a specificity of 91.1% (17/192), and the sensitivity with another five antigens (LAM, katG, 16kD, Mtb39 and Mtb81) to detect antibody responses reached 67.1% (141/210), with a specificity of 92.7% (14/192).

The combination of optimal multiple antigens to detect anti-MTB antibody responses increased the sensitivity and specificity. Therefore, detection of anti-MTB antibody responses with multiple antigens may be valuable in the clinical diagnosis of TB patients.