Recombinant antigens in diagnosis of TB Fig. 4: Frequency of IFN-γ SFCs in a million of PBMCs responding to recombinant proteins in different individual groups. A dotted horizontal line is included to show the cutoff value for a positive response for ESAT-6/CFP-10 (A), ESAT-6 (B), CFP-0 (C), commercial ESAT-6 (D), and PPD (E). diagnosis of TB. Our results indicated higher sensitiv- ity and specificity of fusion protein and poor sensitiv- ity of PPD in the diagnosis of TB patients which is in agreement with other findings.6,8,20,22 These recombi- nant proteins offer a realistic and cost effective alter- native to PPD and their availability in pure form will facilitate this application. In conclusion, we cloned, expressed and purified large amounts of recombinant secretory antigens ESAT-6, CFP-10 and ESAT- 6/CFP-10. These proteins were purified easily by af- finity chromatography and checked with western blotting and circular dichroism methods. Due to higher sensitivity and specificity, recombi- nant antigens ESAT-6, CFP-10 and ESAT-6/CFP-10 can be better candidates for detection of TB when compared with conventional diagnostic methods such as PPD skin test. Since there was a high similarity in sensitivity of ELISPOT test between commercial WWW.ircmj.com Vol 13 August 2011 561