Effect of Chemotherapy on Whole-Blood Cytokine Responses to Mycobacterium tuberculosis Antigens in a Small Cohort of Patients with Pulmonary Tuberculosis

Abstract

The development of genomic and proteomic tools has enabled studies that begin to characterize the molecular targets of an effective host immune response to Mycobacterium tuberculosis, including understanding the specific immune responses associated with tuberculosis (TB) disease progression, disease resolution, and the development of latency. One application of such tools is the development of diagnostic reagents and assays useful as a test of cure. Such a test could be of considerable importance for the evaluation of new therapeutics. We and others have previously described immunodominant proteins of M. tuberculosis, including both vaccine and diagnostic candidates. In the present study, we describe the changes in immune responses to a panel of 71 M. tuberculosis antigens in six patients during the course of therapy. The levels of six cytokines were measured in 24-h whole-blood assays with these antigens, revealing that gamma interferon (IFN-␥), tumor necrosis factor (TNF), and interleukin-10 (IL-10) were differentially regulated in response to a subset of antigens. Therefore, measuring the production of these three cytokines in response to a panel of carefully selected M. tuberculosis proteins during the course of TB therapy might be a promising path toward the development of a test of cure and warrants further validation in larger cohorts of pulmonary TB patients. Tuberculosis (TB) caused by Mycobacterium tuberculosiscomplex bacilli is one of the leading causes of death worldwide (42). Upon exposure to M. tuberculosis, 30 to 40% of close contacts will develop TB infection, of whom 5% would be expected to develop active disease within a 24-month period while the other 95% enter a state of controlled latent TB infection (LTBI), which can reactivate later in life following decreased immunocompetence of the host. T cells, both CD4 ϩ and CD8 ϩ , and the cytokines gamma interferon (IFN-␥) and tumor necrosis factor (TNF) play important roles in the prevention of active disease and the control of LTBI, as demonstrated by gene-knockout animal models and human subjects with mutations affecting the expression of these two cytokines (17).The traditional diagnosis of active TB disease relies on positive identification of acid-fast bacilli (AFB) in a sputum smear or M. tuberculosis identified in culture and is supported by delayed-type hypersensitivity reactions to intradermal injection of M. tuberculosis-specific and nonspecific purified protein derivative (PPD). The tuberculin skin test (TST) utilizes PPD and has a number of drawbacks, notably that TST cross-reacts with the Mycobacterium bovis vaccine strain bacillus CalmetteGuérin (BCG) and other environmental mycobacteria, increasing the number of false positives (37). As IFN-␥ is required for a T helper 1 (Th1) response to M. tuberculosis, this cytokine has been measured ex vivo in serum (35, 39), sputum (35), bronchoalveolar lavage fluid (4), pleural effusions of TB patients (21, 25), or culture supernatants of peripheral blood mononuclear cells (PBMC) after in vitro...

Cytokines for monitoring anti-tuberculous therapy: A systematic review

“…In addition to difference in laboratory methods, there were disparities between studies in patient selection, and timing of sampling. For TB-antigen stimulated TNF-a, for example, four of the eight studies included less than 20 patients with active TB [28,31,38,44]. The study design also varied.…”

“…All five studies found an increase in polyfunctional T cells producing IL-2 and other cytokines at the end of treatment [31,36,38,40,44]. One small pilot study (including only 6 participants), using xMAP Luminex to determine cytokine levels, found no change in IL-2 responses with treatment [28].…”

“…Two studies, one using ELISA and the other flow cytometry, found no change in TNF-a responses during treatment [28,37].…”

“…Of these, two were cross-sectional studies [35,37]. Three studies found a reduction in IL-10 responses with treatment [39,41,43], one study found an increase [30] and three found no change [28,35,37]. Amongst the larger, better-designed studies, …”

“…Of the 17 studies that investigated cytokines after in vitro stimulation, eight were small pilot studies with fewer than 10 [28,31,42,43] or fewer than 20 [29,32,34,38] patients with active TB. Six of the studies were cross-sectional [29,35,37,38,40,44], rather than longitudinal.…”