Candidate biomarkers for discrimination between infection and disease caused by Mycobacterium tuberculosis

Abstract

Infection with Mycobacterium tuberculosis is controlled by an efficacious immune response in about 90% of infected individuals who do not develop disease. Although essential mediators of protection, e.g., interferon-gamma, have been identified, these factors are insufficient to predict the outcome of M. tuberculosis infection. As a first step to determine additional biomarkers, we compared gene expression profiles of peripheral blood mononuclear cells from tuberculosis patients and M. tuberculosis-infected healthy donors by microarray analysis. Differentially expressed candidate genes were predominantly derived from monocytes and comprised molecules involved in the antimicrobial defense, inflammation, chemotaxis, and intracellular trafficking. We verified differential expression for alpha-defensin 1, alpha-defensin 4, lactoferrin, Fcgamma receptor 1A (cluster of differentiation 64 [CD64]), bactericidal permeability-increasing protein, and formyl peptide receptor 1 by quantitative polymerase chain reaction analysis. Moreover, we identified increased protein expression of CD64 on monocytes from tuberculosis patients. Candidate biomarkers were then assessed for optimal study group discrimination. Using a linear discriminant analysis, a minimal group of genes comprising lactoferrin, CD64, and the Ras-associated GTPase 33A was sufficient for classification of (1) tuberculosis patients, (2) M. tuberculosis-infected healthy donors, and (3) noninfected healthy donors.

Human gene expression profiles of susceptibility and resistance in tuberculosis

“…Previous studies using microarray analysis in TB patients have identified gene patterns, which identify subjects at risk for recurrent disease among patients with cured TB 25 and a distinct subset of genes to classify TB patients and LTBI in a Caucasian population. 17 TB patients and healthy household control subjects (both latently infected and uninfected) included in this study were recruited from a cohort with high incidence of infection and disease. Accordingly, the recruitment of NID proved difficult, as almost all individuals in this cohort were found to give a positive result in a tuberculin skin test.…”

“…An earlier study by our group had identified CD64 (alias FCGR1A; Fc gamma receptor 1A) as one of the highest ranking differentially expressed genes in TB-diseased versus latently infected Caucasian subjects. 17 Despite of their different annotations, these genes have remarkably similar sequences. The oligonucleotide probes on the microarray chips used in both studies, were 100% complementary to the sequences of the probes used in either study.…”

“…Increased expression of the CD64 gene in monocytes from TB patients was also confirmed at the protein level in our previous study. 17 A major function of the family of Fc receptors for IgG (FcgRs) is binding of antibodies by their constant domain. The role of antibodies has long been considered to be of minor importance in TB, 26 although more recent studies indicate that antibodies may have a role in control against M. tuberculosis infections.…”

“…An earlier study by our group had identified a minimal set of three genes (CD64, RAB33A and LTF (lactoferrin)), whose combined expression patterns showed a discriminating power between TB and LTBI in Caucasians. 17 These candidate biomarker genes were also included in our RT-PCR validation to investigate whether this subset of genes could discriminate between TB and LTBI individuals from the South African cohort studied herein as well. Similar to those previous findings, CD64 and LTF showed a significant difference in gene expression between the study groups, whereas RAB33A expression levels were similar between TB and LTBI ( Figure 2b).…”

Increased expression of host iron-binding proteins precedes iron accumulation and calcification of primary lung lesions in experimental tuberculosis in the guinea pig

“…Only the heavy chain of ferritin has ferroxidase activity and therefore the anti-oxidant activity of ferritin is attributed only to the heavy chain subunit. The close association between H ferritin expression and the presence of necrosis suggests that H ferritin expression along with lactoferrin may be useful as a biomarker with prognostic or predictive value in determining the clinical outcome of tuberculosis (54).…”