Natural killer cell activation distinguishes Mycobacterium tuberculosis-mediated immune reconstitution syndrome from chronic HIV and HIV/MTB coinfection

Abstract

Background: With increased access to antiretroviral treatment (ART), immune reconstitution inflammatory syndrome (IRIS) in Mycobacterium tuberculosis (MTB)-infected populations remains a clinical challenge. We studied a cross-sectional cohort of HIV-infected subjects in Johannesburg (South Africa) to help define the immune correlates that best distinguish IRIS from ongoing MTB cases.

Methods: We studied HIV+ subjects developing MTB-related unmasking tuberculosis-related immune reconstitution inflammatory syndrome (uTB-IRIS) after ART initiation; control groups were subjects with HIV and HIV/tuberculosis-coinfected subjects with comparable ART treatment. Testing was conducted with whole blood-based 4-color flow cytometry and plasma-based Luminex cytokine assessment.

Results: Natural killer cell activation, C-reactive protein, and interleukin 8 serum concentration were significantly higher in uTB-IRIS subjects compared with both control groups. In addition, all MTB-coinfected subjects, independent of clinical presentation, had higher neutrophils and T-cell activation, together with lower lymphocytes, CD4⁺ T-cell, and myeloid dendritic cell counts. Using conditional inference tree analysis, we show that elevated natural killer cell activation in combination with lymphocyte count characterizes the immunological profile of uTB-IRIS.

Conclusion: Our results support a role for innate immune effectors in the immunopathogenesis of unmasking MTB-related IRIS and identify new immune parameters defining this pathology.

Figure 1

Variables associated with unmasking M. tuberculosis IRIS Distribution of Flow cytometry (top panels) and multiplex array (middle and bottom panels)-derived variables in HIV-infected subjects (group 1), HIV/MTB-co-infected subjects (group 2) and uTB-IRIS subjects (group 3). For all indicated variables, boxes represent median, 25^th and 75^th percentiles and whiskers represent 5^th and 95^th percentiles. Brackets indicate significant differences between groups (unadjusted Wicoxon test p < 0,05). Benjamini-Yekutieli FDR-adjusted Kruskal-Wallis test p < 0.1 for all variables.

Figure 2

Variables associated with M. tuberculosis infection Distribution of hematology, Flow cytometry and multiplex array-derived variables in study groups (see Fig. 1). For all indicated variables, boxes represent median, 25^th and 75^th percentiles and whiskers represent 5^th and 95^th percentiles. Full and dashed brackets indicate differences between groups with unadjusted Wicoxon test p < 0,05 and < 0.07, respectively. Benjamini-Yekutieli FDR-adjusted Kruskal-Wallis test p < 0.1 for all variables.

Figure 3

Conditional partitioning inference tree (ctree) classification Graphical representation of recursive conditional inference tree classification analysis: nodes 1, 2 and 4 represent significant (Bonferroni-adjusted p < 0.05) splits at the indicated thresholds (for CD69⁺ NK cells, values represent % of total NK cells). The relative frequency and numbers for each study group (see also fig. 1) are provided for the distal nodes (3, 5, 6 and 7) and illustrated by histograms; the percentages above the bars represent the relative frequency of subjects in group 1 (HIV control), group 2 (MTB-HIV co-infection) and 3 (uTB-IRIS) for each node.