Tuberculosis: a missed opportunity for early diagnosis at the front line?

INTRODUCTION: The incidence of tuberculosis (TB) has increased over the last two decades. Many patients with TB preferentially access healthcare via the emergency department (ED) prediagnosis, presenting an early opportunity for diagnosis. METHODS: We looked at the number of patients who presented to ED in the 3 months prior to TB notification, and their outcomes. RESULTS: 42% of all notifications had accessed ED prior to notification. The majority were hospitalised, with a proportion of these patients previously attending ED only to be discharged. 37% of patients were discharged from ED with many having TB symptoms, and only a minority referred onto TB clinic. CONCLUSIONS: The ED is often the first contact that urban TB patients have with healthcare. Healthcare professionals should ensure this diagnosis is not missed in high incidence areas as it has significant clinical and infection control consequences.

Ethnic variation in inflammatory profile in tuberculosis.

Distinct phylogenetic lineages of Mycobacterium tuberculosis (MTB) cause disease in patients of particular genetic ancestry, and elicit different patterns of cytokine and chemokine secretion when cultured with human macrophages in vitro. Circulating and antigen-stimulated concentrations of these inflammatory mediators might therefore be expected to vary significantly between tuberculosis patients of different ethnic origin. Studies to characterise such variation, and to determine whether it relates to host or bacillary factors, have not been conducted. We therefore compared circulating and antigen-stimulated concentrations of 43 inflammatory mediators and 14 haematological parameters (inflammatory profile) in 45 pulmonary tuberculosis patients of African ancestry vs. 83 patients of Eurasian ancestry in London, UK, and investigated the influence of bacillary and host genotype on these profiles. Despite having similar demographic and clinical characteristics, patients of differing ancestry exhibited distinct inflammatory profiles at presentation: those of African ancestry had lower neutrophil counts, lower serum concentrations of CCL2, CCL11 and vitamin D binding protein (DBP) but higher serum CCL5 concentrations and higher antigen-stimulated IL-1 receptor antagonist and IL-12 secretion. These differences associated with ethnic variation in host DBP genotype, but not with ethnic variation in MTB strain. Ethnic differences in inflammatory profile became more marked following initiation of antimicrobial therapy, and immunological correlates of speed of elimination of MTB from the sputum differed between patients of African vs. Eurasian ancestry. Our study demonstrates a hitherto unappreciated degree of ethnic heterogeneity in inflammatory profile in tuberculosis patients that associates primarily with ethnic variation in host, rather than bacillary, genotype. Candidate immunodiagnostics and immunological biomarkers of response to antimicrobial therapy should be derived and validated in tuberculosis patients of different ethnic origin.

Vitamin D accelerates resolution of inflammatory responses during tuberculosis treatment.

Calcidiol, the major circulating metabolite of vitamin D, supports induction of pleiotropic antimicrobial responses in vitro. Vitamin D supplementation elevates circulating calcidiol concentrations, and thus has a potential role in the prevention and treatment of infection. The immunomodulatory effects of administering vitamin D to humans with an infectious disease have not previously been reported. To characterize these effects, we conducted a detailed longitudinal study of circulating and antigen-stimulated immune responses in ninety-five patients receiving antimicrobial therapy for pulmonary tuberculosis who were randomized to receive adjunctive high-dose vitamin D or placebo in a clinical trial, and who fulfilled criteria for per-protocol analysis. Vitamin D supplementation accelerated sputum smear conversion and enhanced treatment-induced resolution of lymphopaenia, monocytosis, hypercytokinaemia, and hyperchemokinaemia. Administration of vitamin D also suppressed antigen-stimulated proinflammatory cytokine responses, but attenuated the suppressive effect of antimicrobial therapy on antigen-stimulated secretion of IL-4, CC chemokine ligand 5, and IFN-α. We demonstrate a previously unappreciated role for vitamin D supplementation in accelerating resolution of inflammatory responses during tuberculosis treatment. Our findings suggest a potential role for adjunctive vitamin D supplementation in the treatment of pulmonary infections to accelerate resolution of inflammatory responses associated with increased risk of mortality.

High-dose vitamin D(3) during intensive-phase antimicrobial treatment of pulmonary tuberculosis: a double-blind randomised controlled trial.

BACKGROUND: Vitamin D was used to treat tuberculosis in the pre-antibiotic era, and its metabolites induce antimycobacterial immunity in vitro. Clinical trials investigating the effect of adjunctive vitamin D on sputum culture conversion are absent. METHODS: We undertook a multicentre randomised controlled trial of adjunctive vitamin D in adults with sputum smear-positive pulmonary tuberculosis in London, UK. 146 patients were allocated to receive 2·5 mg vitamin D(3) or placebo at baseline and 14, 28, and 42 days after starting standard tuberculosis treatment. The primary endpoint was time from initiation of antimicrobial treatment to sputum culture conversion. Patients were genotyped for TaqI and FokI polymorphisms of the vitamin D receptor, and interaction analyses were done to assess the influence of the vitamin D receptor genotype on response to vitamin D(3). This trial is registered with ClinicalTrials.gov number NCT00419068. FINDINGS: 126 patients were included in the primary efficacy analysis (62 assigned to intervention, 64 assigned to placebo). Median time to sputum culture conversion was 36·0 days in the intervention group and 43·5 days in the placebo group (adjusted hazard ratio 1·39, 95% CI 0·90-2·16; p=0.14). TaqI genotype modified the effect of vitamin D supplementation on time to sputum culture conversion (p(interaction)=0·03), with enhanced response seen only in patients with the tt genotype (8·09, 95% CI 1·36-48·01; p=0·02). FokI genotype did not modify the effect of vitamin D supplementation (p(interaction)=0·85). Mean serum 25-hydroxyvitamin D concentration at 56 days was 101·4 nmol/L in the intervention group and 22·8 nmol/L in the placebo group (95% CI for difference 68·6-88·2; p<0·0001). INTERPRETATION: Administration of four doses of 2·5 mg vitamin D(3) increased serum 25-hydroxyvitamin D concentrations in patients receiving intensive-phase treatment for pulmonary tuberculosis. Vitamin D did not significantly affect time to sputum culture conversion in the whole study population, but it did significantly hasten sputum culture conversion in participants with the tt genotype of the TaqI vitamin D receptor polymorphism. FUNDING: British Lung Foundation.

Neutrophil-mediated innate immune resistance to mycobacteria.

Neutrophils contain antimicrobial peptides with antituberculous activity, but their contribution to immune resistance to tuberculosis (TB) infection has not been previously investigated to our knowledge. We determined differential white cell counts in peripheral blood of 189 adults who had come into contact with patients diagnosed with active TB in London, United Kingdom, and evaluated them for evidence of TB infection and capacity to restrict mycobacterial growth in whole-blood assays. Risk of TB infection was inversely and independently associated with peripheral blood neutrophil count in contacts of patients diagnosed with pulmonary TB. The ability of whole blood to restrict growth of Mycobacterium bovis bacille Calmette Guérin and Mycobacterium tuberculosis was impaired 7.3- and 3.1-fold, respectively, by neutrophil depletion. In microbiological media, human neutrophil peptides (HNPs) 1-3 killed M. tuberculosis. The neutrophil peptides cathelicidin LL-37 and lipocalin 2 restricted growth of the organism, the latter in an iron-dependent manner. Black African participants had lower neutrophil counts and lower circulating concentrations of HNP1-3 and lipocalin 2 than south Asian and white participants. Neutrophils contribute substantially to innate resistance to TB infection, an activity associated with their antimicrobial peptides. Elucidation of the regulation of neutrophil antimicrobial peptides could facilitate prevention and treatment of TB.

A single dose of vitamin D enhances immunity to mycobacteria.

RATIONALE: Vitamin D was used to treat tuberculosis (TB) in the preantibiotic era. Prospective studies to evaluate the effect of vitamin D supplementation on antimycobacterial immunity have not previously been performed. OBJECTIVES: To determine the effect of vitamin D supplementation on antimycobacterial immunity and vitamin D status. METHODS: A double-blind randomized controlled trial was conducted in 192 healthy adult TB contacts in London, United Kingdom. Participants were randomized to receive a single oral dose of 2.5 mg vitamin D or placebo and followed up at 6 weeks. MEASUREMENTS AND MAIN RESULTS: The primary outcome measure was assessed with a functional whole blood assay (BCG-lux assay), which measures the ability of whole blood to restrict luminescence, and thus growth, of recombinant reporter mycobacteria in vitro; the readout is expressed as a luminescence ratio (luminescence postinfection/baseline luminescence). IFN-gamma responses to the Mycobacterium tuberculosis antigens early secretory antigenic target-6 and culture filtrate protein 10 were determined with a second whole blood assay. Vitamin D supplementation significantly enhanced the ability of participants' whole blood to restrict BCG-lux luminescence in vitro compared with placebo (mean luminescence ratio at follow-up, 0.57, vs. 0.71, respectively; 95% confidence interval for difference, 0.01-0.25; p=0.03) but did not affect antigen-stimulated IFN-gamma secretion. CONCLUSIONS: A single oral dose of 2.5 mg vitamin D significantly enhanced the ability of participants' whole blood to restrict BCG-lux luminescence in vitro without affecting antigen-stimulated IFN-gamma responses. Clinical trials should be performed to determine whether vitamin D supplementation prevents reactivation of latent TB infection. Clinical trial registered with www.clinicaltrials.gov (NCT 00157066).