Mortality in severe human immunodeficiency virus-tuberculosis associates with innate immune activation and dysfunction of monocytes

Background: Case fatality rates among hospitalized patients diagnosed with human immunodeficiency virus (HIV)-associated tuberculosis remain high, and tuberculosis mycobacteremia is common. Our aim was to define the nature of innate immune responses associated with 12-week mortality in this population. Methods: This prospective cohort study was conducted at Khayelitsha Hospital, Cape Town, South Africa. Hospitalized HIV-infected tuberculosis patients with CD4 counts <350 cells/µL were included; tuberculosis blood cultures were performed in all. Ambulatory HIV-infected patients without active tuberculosis were recruited as controls. Whole blood was stimulated with Escherichia coli derived lipopolysaccharide, heat-killed Streptococcus pneumoniae, and Mycobacterium tuberculosis. Biomarkers of inflammation and sepsis, intracellular (flow cytometry) and secreted cytokines (Luminex), were assessed for associations with 12-week mortality using Cox proportional hazard models. Second, we investigated associations of these immune markers with tuberculosis mycobacteremia. Results: Sixty patients were included (median CD4 count 53 cells/µL (interquartile range [IQR], 22-132); 16 (27%) died after a median of 12 (IQR, 0-24) days. Thirty-one (52%) grew M. tuberculosis on blood culture. Mortality was associated with higher concentrations of procalcitonin, activation of the innate immune system (% CD16+CD14+ monocytes, interleukin-6, tumour necrosis factor-ɑ and colony-stimulating factor 3), and antiinflammatory markers (increased interleukin-1 receptor antagonist and lower monocyte and neutrophil responses to bacterial stimuli). Tuberculosis mycobacteremia was not associated with mortality, nor with biomarkers of sepsis. Conclusions: Twelve-week mortality was associated with greater pro- and antiinflammatory alterations of the innate immune system, similar to those reported in severe bacterial sepsis.