Evaluation of gamma interferon immune response elicited by the newly constructed PstS-1(285-374):CFP10 fusion protein to detect Mycobacterium tuberculosisinfection.

摘要

The PstS1 antigen is highly immunogenic, principally when combined with CFP10during both latent and active TB infection. In the present study, a selectedpstS1 gene fragment was cloned, fused with CFP10, and expressed in Escherichiacoli. The product [PstS-1(285-374):CFP10] was compared to the recombinant fusedRD1 (region of deletion 1) protein (ESAT-6:CFP10) in detecting Mycobacteriumtuberculosis infection in 108 recent contacts of pulmonary tuberculosis (TB)cases, considering a positive tuberculin skin test (TST) to be the baseline. The release of gamma interferon (IFN-γ) in 22-h whole-blood and 5-day lymphocytestimulation assays primed with each antigen was determined. All contacts wereclinically followed for up to 1 year, and 87% of the tuberculin skintest-positive (TST(positive)) patients accepted preventative treatment.Concerning the IFN-γ response to PstS-1(285-374):CFP10 in the 22-h and 5-dayassays, a slight increase in contact-TST(positive) detection was observed (23/54 and 26/54) compared to the level seen with the RD1 protein (18/54 and 24/54)whereas in the TST(negative) group, similarly lower numbers (≤5/48) of responderswere achieved for both antigens, except for RD1 in the 5-day assay (8/48). Bycombining the IFN-γ responders to both antigens in the 5-day assays, slightlyhigher increases in positivity were found in the TST(positive) (32/54) andTST(negative) (10/48) groups. Two of 12 untreated TST(positive) contactsprogressed to active TB and were concordantly positive in all assays, except for one contact who lacked positivity in the RD1 5-day assay. We demonstrated for thefirst time that PstS-1(285-374):CFP10 slightly increased contact positivity anddetection of active disease progression, suggesting its potential application as a TB infection marker.