Immune markers measured before treatment predict outcome of intensive phase tuberculosis therapy

Abstract

The development of a statistical model based on simple immunological markers which could predict the response to tuberculosis treatment would facilitate clinical trials of new anti-tuberculosis drugs. We have examined the ability of immunological biomarkers, measured at diagnosis and after 4 weeks of treatment, to predict sputum smear status at week 8. Eighteen tuberculosis patients with positive Ziehl-Nielsen (ZN)-stained sputum smears 8 weeks after initiation of treatment (slow response) were matched for age, gender, sputum smear grade and extent of disease on chest radiograph to 18 patients with negative sputum smears at week 8 (fast response). In addition to total white blood cell (WBC) counts and absolute lymphocyte, monocyte and neutrophil numbers, concentrations of six serum markers were measured by enzyme-linked immunosorbent assay (ELISA) in all patients (soluble interleukin-2 receptor alpha (sIL-2Ralpha), granzyme B, soluble tumour necrosis factor alpha receptors 1 and 2 (sTNF-R1 and -2), nitrotyrosine and interferon-gamma (IFN-gamma). At diagnosis, 4 biomarkers (sTNF-R1, total WBC, absolute monocyte and absolute neutrophil numbers) were significantly higher in slow response patients. At week 4, total WBC count and absolute monocyte and neutrophil numbers remained significantly higher in slow responders. Discriminant analysis of the diagnosis and week 4 data provided models for classification of slow response patients with 67% and 83% predictive accuracy. We suggest that treatment response phenotypes can be determined before the start of treatment. Reliable predictive models would allow targeted interventions for patients at risk for slow treatment response to standard tuberculosis therapy.

Fig. 1

Study profile. Of the 220 patients who were recruited, 112 met the inclusion criteria. Twenty-one had a positive sputum smear result at week 8 (‘slow responders’), of whom 18 were suitable for matching with ‘fast responders’ who had negative smears at week 8.

Fig. 2

Serum biomarker concentrations in community controls and in tuberculosis (TB) patients with fast and slow responses to TB treatment. The median serum levels, 25th and 75th percentiles and minimum and maximum values of four biomarkers as determined by enzyme-linked immunosorbent assay (ELISA) at one time-point in controls and at diagnosis and after 4 weeks of TB treatment in fast and slow responders to treatment are shown. Soluble interleukin-2 receptor alpha (sIL-2Rα) (a), granzyme B (b), soluble tumour necrosis factor alpha receptor 1 (sTNF-R1) (c) and sTNF-R2 (d) are represented. C = community controls; FR = fast responder TB patients [negative Ziehl–Nielsen (ZN)-stained sputum smear after 8 weeks of therapy]; SR = slow responder TB patients. †Statistically significant differences between patient groups and controls; *statistically significant differences between FR and SR groups at a single time-point; #significant differences between diagnosis and the 4-week time-point within a treatment response group. The data for interferon (IFN)-γ and nitrotyrosine are not shown, as the mean values were all below the lower limit of detection for the assay at all the time-points.

Fig. 3

Peripheral blood white cell counts in community controls and in TB patients with fast and slow responses to TB treatment. Median cell counts, 25th and 75th percentiles and minimum and maximum values of absolute numbers of total white blood cells (WBC) (a), lymphocytes (b), monocytes (c) and neutrophils (d) are shown at one time-point for community controls and at diagnosis and 4 weeks after start of tuberculosis (TB) treatment in fast and slow responders as determined by week 8 sputum smear status. C = community controls; FR = fast responder TB patients [negative Ziehl–Nielsen (ZN)-stained sputum smear after 8 weeks of therapy]; SR = slow responder TB patients. †Statistically significant differences between patient groups and controls; *statistically significant difference between FR and SR groups at a single time-point; #significant differences between diagnosis and the 4-week time-point within a treatment response group.