ifn-γ and il-2 responses to recombinant aladh against esat-6/cfp-10 fusion antigens in the diagnosis of latent versus active tuberculosis infection

background: discriminating latent tuberculosis infection (ltbi) from active tbi may be challenging. the objective of this study was to produce the recombinant l-alanine dehydrogenase (aladh) antigen and evaluate individuals with ltbi, those with active tbi, and uninfected individuals by enzyme-linked immunospot assay (elispot) in order to distinguish ltbi from active tbi. methods: this exploratory study was performed in the iranian city of shiraz from 2014 to 2015. the study population (n=99) was divided into 3 groups: individuals with newly diagnosed active tbi (n=33), their household contacts (n=33), and controls (n=33). aladh was produced through pcr and cloning methods. the diagnostic characteristics of aladh vs. esat-6/cfp-10 were evaluated in responses to interferon-γ (ifn-γ) and interleukin-2 (il-2) with elispot. differences between the groups were assessed with the kruskal–wallis and mann–whitney tests for nonparametric data analysis. the statistical analyses were performed with spss, version 16. results: ifn-γ responses to both esat-6/cfp-10 (p=0.81) and aladh (p=0.18) revealed that there were no significant differences between the individuals with ltbi and those with active tbi. the same results were determined for il-2 responses to esat-6/cfp-10 between the 2 groups, while significantly higher il-2 responses to aladh were observed in ltbi than in active tbi. according to the roc curve analysis, a cutoff value of 275 sfc showed sensitivity of 75.8% and specificity of 78.8% for distinguishing ltbi from active tbi by il-2 responses to aladh. conclusion: the current study suggests that it may be possible to discriminate ltbi from active tbi by il-2 responses to aladh.