Messenger RNA expression of IL-8, FOXP3, and IL-12β differentiates latent tuberculosis infection from disease

Differentiation of active from latent tuberculosis (TB) is a major challenge in the control of TB. In this study, PBMC from latent TB-infected subjects, TB patients, and tuberculin skin test-negative donors stimulated with the Mycobacterium tuberculosis (Mtb)-specific Ag, early secretory antigenic target 6, and mRNA for 45 immune-related genes was measured by quantitative real-time PCR. Univariate analysis showed significant differences in the expression of 10 genes (IFN-γ, FOXP3, IL-1α, IL-1β, IL-2, IL-6, IL-8, IL-12α, IL-12β, and IL-24) in PBMC from TB patients vs latent TB-infected subjects (p < 0.01). Multivariate logistic regression and classification and regression tree analyses revealed that expression of three genes, IL-8, FOXP3, and IL-12β, is predictive for TB vs latent Mtb infection. Thus, measurement of Ag-spetific expression of these three genes may offer a specific and noninvasive means of differentiating between latent Mtb infection and TB.