NEW MICROBIOLOGICA, 37, 153-161, 2014 Corresponding author Ilaria Sauzullo, PhD Department of Public Health and Infectious Diseases Sapienza University, Rome Piazzale Aldo Moro, 1 - 00185 Rome, Italy E-mail: ilariasauzullo@libero.it INTRODUCTION The World Health Organization (WHO) esti- mates that there were 8.7 million new cases of tuberculosis (TB) in 2011, including 1.1 million cases (13%) among human immunodeficiency SUMMARY Received August 11, 2014 Accepted March 4, 2014 The objective of the study was to: 1) investigate the performance of QuantiFERON-TB Gold In-Tube (QFT-GIT) in HIV-infected patients with active tuberculosis (TB); 2) evaluate the sequential changes in QFT-GIT assay during the treatment response; 3) investigate the direct in vitro effects of antituberculous drugs on both secretion of IFN-g and apoptosis of T cells. Forty-four HIV-patients with active TB were enrolled and tested with QFT-GIT. Thirteen of them were followed longitudinally by QFT-GIT, performed at baseline and six and nine months after TB-treatment onset. For in vitro experiments, cells from healthy donors and HIV-naive subjects were pretreated with four antituberculous-drugs, and then examined for IFN-g secretion and apoptosis of T-cells. The QFT-GIT was positive in 66%, negative in 11.3% and indeterminate in 22.7%. Longitudinal analysis in 13 HIV-TB subjects showed that at therapy completion a reversion to negative response was found only in 38.4% of patients, but in 30.7% the QFT-GIT remained positive. Overall, during the anti-TB treatment no significant decrease in average IFN-g response was observed in these patients (p<0.001). In vitro experiments showed that the four antitubercu- lous-drugs, within the range of therapeutically achievable concentrations, did not exert any down-regulatory effect on IFN-g production and did not have any effect on apoptosis of T cells from HIV naïve subjects. Despite the high rate of indeterminate results, QFT-GIT assay may represent a good tool in the diagnostic workup for active TB in HIV-patients. Although the antituberculous drugs do not have any direct effect on host immune response to mycobacterial antigen, changes in longitudinal IGRA response have been found during in vivo anti-TB treatment. KEY WORDS: Tuberculosis, HIV, QFT-GIT, anti-TB treatment. Interferon-g release assay in HIV-infected patients with active tuberculosis: impact of antituberculous drugs on host immune response Ilaria Sauzullo 1 , Fabio Mengoni 1 , Angela Ermocida 1 , Anna P. Massetti 1 , Claudia D’Agostino 1 , Gianluca Russo 1 , Alessandra Salotti 1 , Mario Falciano 1 , Vincenzo Vullo 1 , Claudio M. Mastroianni 2 1 Department of Public Health and Infectious Diseases, ‘Sapienza’ University, Rome, Italy; 2 Infectious Diseases Unit, Fondazione Eleonora Lorillard Spencer Cenci, Sapienza University, Latina, Italy virus (HIV)-infected people, and an additional 0.4 million deaths among HIV-positive TB cas- es (WHO, 2012). Prevention and treatment of TB in people liv- ing with HIV is an urgent priority for both HIV/ AIDS and TB programmers. HIV infection sub- stantially increases the risk of developing TB once infected with the bacillus, shortens the time to development of the active disease (Cor- bett et al., 2003; Shafer et al., 1996) and also in- creases the risk of multidrug-resistant tubercu- losis compared to people not infected with HIV (Narain et al., 2004; Pelly et al., 2004). Tuber-