BASIC AND TRANSLATIONAL SCIENCE Tuberculosis After Commencing Antiretroviral Therapy for HIV Infection Is Associated With Elevated CXCL9 and CXCL10 Responses to Mycobacterium tuberculosis Antigens Benjamin G. Oliver, BSc (Hons),* Julian H. Elliott, MBBS, PhD,†‡§ Patricia Price, MSc, PhD,* Michael Phillips, BSc (Hons), MMed Sci,k David A. Cooper, MBBS, MD,¶ and Martyn A. French, MB ChB, MD* Background: Commencing antiretroviral therapy (ART) in human immunodeficiency virus-infected patients with treated or unrecognized Mycobacterium tuberculosis disease may trigger tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) or ART– associated tuberculosis (ART-TB). We have shown that whole-blood interferon-gamma release assays may aid in the prediction and diagnosis of ART-TB. Here, we investigate interferon-gamma–inducible chemo- kines CXCL9 and CXCL10. Methods: CXCL9 and CXCL10 responses to region of difference 1 (RD1) antigens and purified protein derivative (PPD) were assayed in plasma from whole-blood cultures collected before and after 4, 12, and 24 weeks of ART from 15 TB-IRIS cases, 11 ART-TB cases, and matched controls. Results: Relative to matched controls, ART-TB cases had elevated CXCL10 responses to RD1 antigens pre-ART (P = 0.02) and to PPD and RD1 antigens over 24 weeks of ART (P # 0.02 and P # 0.03). In contrast, TB-IRIS cases had higher CXCL10 responses to RD1 antigens before and after 4 weeks of ART only (P = 0.04 for both). CXCL9 responses to PPD and RD1 antigens were similar but less pronounced in ART-TB cases and did not differ between TB-IRIS cases and controls. CXCL10 responses to RD1 antigens performed as well as, or better than, IFN-g responses in the prediction and diagnosis of ART-TB. Conclusions: Tuberculosis after commencing ART is associated with increased CXCL10 and, to a lesser extent, CXCL9 responses to M. tuberculosis antigens. Assessment of antigen-induced CXCL10 responses to RD1 antigens may assist in the prediction and diagnosis of ART-TB. Key Words: human immunodeficiency virus, antiretroviral therapy, tuberculosis-associated immune reconstitution inflammatory syn- drome, antiretroviral therapy–associated tuberculosis, CXCL10, CXCL9, IFN-g (J Acquir Immune Defic Syndr 2012;61:287–292) INTRODUCTION Mycobacterium tuberculosis disease is the leading cause of illness and death in patients with human immunode- ficiency virus (HIV) infection. 1 M. tuberculosis–specific Th1 cells are depleted during HIV infection 2,3 but are partly re- stored by antiretroviral therapy (ART). 4,5 In some HIV- infected patients, the restored immune response to M. tuber- culosis may cause immunopathology known as immune res- toration disease (IRD). 6 Paradoxical worsening of treated tuberculosis (TB) after ART is a form of IRD known as TB-associated immune reconstitution inflammatory syndrome (TB-IRIS). 7 Tuberculosis presenting during the first 3 months of ART might also be a form of IRD. Many cases present as ‘unmasking TB-IRIS’ whereby previously subclinical TB is ‘unmasked’ after starting ART. However, newly acquired TB may also present after ART initiation, so cases of TB that present after ART are referred to as ART-associated tubercu- losis (ART-TB). 7 ART-TB has been associated with increased interferon-gamma (IFN-g) responses to mycobacterial anti- gens compared with HIV patients with no history of TB. 8 Data from large prospective studies indicate that mortality associated with TB-IRIS is low but morbidity is substantial in HIV/TB-infected patients who have pre-ART CD4 + T cell counts ,50 cells per microliter and initiate ART within 4 weeks of starting TB treatment. 9,10 Morbidity and mortality from ART-TB are also significant, as HIV-infected patients who present with TB during the first 3 months of ART are 3.25 times more likely to die than HIV-infected patients presenting with TB at other times. 11 Prediction and diagnosis of TB-IRIS and ART-TB might be improved by a better understanding of their Received for publication January 25, 2012; accepted June 8, 2012. From the *School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia; †Infectious Diseases Unit, Alfred Hospital, Melbourne, Australia; ‡Department of Infectious Diseases, Monash Univer- sity, Melbourne, Australia; §Centre for Population Health, Burnet Institute, Melbourne, Australia; kWestern Australia Institute for Medical Research, University of Western Australia, Perth, Australia; and ¶Kirby Institute, University of New South Wales, Sydney, Australia. Supported by the Australian Agency for International Development (AusAID), the Australian National Centre in HIV Epidemiology and Clinical Research and an Australian Government National Health and Medical Research Council program grant (grant number 510448). This work has been presented in part at the 23rd Annual Conference of the Australasian Society for HIV Medicine, Canberra, September 26–28, 2011 (Paper Number: 503). The authors have no conflicts of interest to disclose. Correspondence to: Martyn A. French, MB ChB, MD, School of Pathology and Laboratory Medicine, Level 2 MRF Building, Rear 50 Murray Street, Perth, 6000, Australia (e-mail: martyn.french@uwa.edu.au). Copyright © 2012 by Lippincott Williams & Wilkins J Acquir Immune Defic Syndr  Volume 61, Number 3, November 1, 2012 www.jaids.com | 287