Abstract

Although the delayed-type hypersensitivity (DTH) skin reaction to tuberculin is used worldwide for tuberculosis (TB) detection, it has poor diagnostic specificity due to the presence of common antigens in tuberculin shared by many mycobacterial species. The problem is noticed, especially in countries where the Bacillus Calmette-Gue´rin (BCG) vaccination is widely practiced. Thus, a new skin test antigen specific for the diagnosis of Mycobacterium tuberculosis (MTB) infection is urgently needed. CFP-10, a mycobacterial secretary protein that is absent inMycobacterium bovis BCG and most other mycobacterial species includingMycobacterium avium, Mycobacterium intracellulare, has been shown to elicit cellular immune responses in MTB infected individuals and can be a good candidate for MTB specific diagnosis. We prepared recombinant MTB CFP-10, rCFP-10, and its utility as specific antigen for TB diagnosis was evaluated by skin testing in guinea pigs sensitized with M. tuberculosis, M. bovis, and M. bovis BCG. Our results show that the purified MTB rCFP-10 antigen elicits a positive skin response only in the guinea pigs sensitized with M. tuberculosis and M. bovis, and not in the animals sensitized with M. bovis BCG vaccine. The data presented in this study supports further testing of the use rCFP-10 as the specific antigen in the skin test for the diagnosis of MTB infection in humans.

Key words: Recombinant CFP-10 protein, skin test, delayed-type hypersensitivity,tuberculosis infection, Mycobacterium tuberculosis, Mycobacterium bovis, Bacillus Calmette-Gue´rin.

Abbreviation

DTH, Delayed-type hypersensitivity; TB, tuberculosis; BCG,Bacillus Calmette-Gue´rin; MTB, Mycobacterium tuberculosis; PPD, purified protein derivative; RD1, region of difference 1; NTM, non-tuberculousmycobacteria; HLA, humam leucocyte antigen; PCR, polymerase chain reaction;LB, Luria-Bertani; X-Gal, 5-bromo-4-chloro-3-indolyl β-D- galactopyranoside;BLAST, basic local alignment search tool; IPTG, isopropyl-b-D-thiogalactopyranoside; PBS, phosphate-buffered saline; GMP, good manufacturing practices. that 45% of Chinese population are latently infected