Antigen-Specific Interferon-Gamma Responses and Innate Cytokine Balance in TB-IRIS

Abstract

Background Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) remains a poorly understood complication in HIV-TB patients receiving antiretroviral therapy (ART). TB-IRIS could be associated with an exaggerated immune response to TB-antigens. We compared the recovery of IFNγ responses to recall and TB-antigens and explored in vitro innate cytokine production in TB-IRIS patients. Methods In a prospective cohort study of HIV-TB co-infected patients treated for TB before ART initiation, we compared 18 patients who developed TB-IRIS with 18 non-IRIS controls matched for age, sex and CD4 count. We analyzed IFNγ ELISpot responses to CMV, influenza, TB and LPS before ART and during TB-IRIS. CMV and LPS stimulated ELISpot supernatants were subsequently evaluated for production of IL-12p70, IL-6, TNFα and IL-10 by Luminex. Results Before ART, all responses were similar between TB-IRIS patients and non-IRIS controls. During TB-IRIS, IFNγ responses to TB and influenza antigens were comparable between TB-IRIS patients and non-IRIS controls, but responses to CMV and LPS remained significantly lower in TB-IRIS patients. Production of innate cytokines was similar between TB-IRIS patients and non-IRIS controls. However, upon LPS stimulation, IL-6/IL-10 and TNFα/IL-10 ratios were increased in TB-IRIS patients compared to non-IRIS controls. Conclusion TB-IRIS patients did not display excessive IFNγ responses to TB-antigens. In contrast, the reconstitution of CMV and LPS responses was delayed in the TB-IRIS group. For LPS, this was linked with a pro-inflammatory shift in the innate cytokine balance. These data are in support of a prominent role of the innate immune system in TB-IRIS.

Robust Reconstitution of Tuberculosis-Specific Polyfunctional CD4+T-Cell Responses and Rising Systemic Interleukin 6 in Paradoxical Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome

“…Furthermore, to evaluate the broader hypothesis that TB-IRIS is associated with greater immune recovery on ART, a secondary analysis used a generalized estimating equation (GEE) model with an independent correlation structure and robust standard error estimators to evaluate the association between TB-IRIS and CD4 count changes on ART during 6 months of follow-up, including all available CD4 counts and adjusting for potential confounders. Additionally, some control patients have rapid recovery of tuberculosisspecific T-cell function similar to TB-IRIS patients, but do not progress to IRIS [15][16][17]. In an exploratory analysis, we tested the hypothesis that increases in IL-6 levels, which have been associated with IRIS [11,13,15,20], would be less in control patients who also had rapid recovery of cellular immune function compared to TB-IRIS patients using previously determined IL-6 concentrations [15] and rank-sum tests.…”

“…Improved cellular immune recovery in those with TB-IRIS is further suggested by the significantly greater increases in CD4 counts on ART during longer-term follow-up. Most immunologic investigations of TB-IRIS have focused on IFN-γ responses, yielding inconsistent results [9,16,17]. Although very few studies have evaluated polyfunctional T-cell responses, our finding that increases in tuberculosis-specific IFN-γ + /IL-2 + /TNF-α + CD4 + T-cells on ART are independently associated with paradoxical TB-IRIS is consistent with a report where patients with several different types of opportunistic infections (including 2 with paradoxical TB-IRIS) were evaluated [28].…”

“…Immunologically, higher pre-ART levels of immune activation and rapid increases in tuberculosis-specific interferon gamma (IFN-γ)-producing cells after ART initiation in HIV-infected adults have been associated with development of TB-IRIS [7,[9][10][11][12]. However, in several recent studies, levels of pre-ART immune activation were actually lower in TB-IRIS patients vs controls [13][14][15], and multiple reports have indicated that patients without TB-IRIS may also have robust increases in levels of pathogen-specific immune responses on ART [16,17]. Existing data are therefore inconclusive about whether higher levels of pre-ART immune activation predispose to TB-IRIS and whether tuberculosis-specific T-cells are involved in TB-IRIS pathogenesis.…”

“…One important limitation is that previous studies relating immune recovery on ART to TB-IRIS have primarily focused on IFN-γ responses alone [9,16,17]; however, multiple cytokines including interleukin 2 (IL-2) and tumor necrosis factor alpha (TNF-α), which are involved in T-cell proliferation and host protection in tuberculosis disease, may also be associated with TB-IRIS [18,19]. Furthermore, innate immune responses involving rapid increases in proinflammatory cytokines such as interleukin 6 (IL-6) on ART have also been relatively consistently implicated in the pathogenesis of TB-IRIS [11,20].…”

The IGRA Tests: Where Are We Now?

“…Some studies indicated lower sensitivity of QFN-GIT with CD4 bellow 200 cells/ /mm 3 [7], while the others did not find any differences [8] or even reported higher sensitivity in patients with CD4 T lymphocytes below 200 cells/ /mm 3 (T-SPOT.TB ) [9]. Also Gooovaerts et al, who examined IFN-gamma responses to ESAT-6 and CFP-10, did not find any differences between those with TB-associated immune reconstitution inflammatory syndrome (TB-IRIS) and non-IRIS controls [10].…”