Microarray analysis of gene expression associated with extrapulmonary dissemination of tuberculosis

Although extrapulmonary organs are involved in 20% of patients with tuberculosis, the host genetic factors associated with the extrapulmonary dissemination of tuberculosis are not yet known. The aim of this study was to identify the host genetic factors associated with the extrapulmonary dissemination of tuberculosis by comparing gene expression profiles of patients who had recovered from extrapulmonary tuberculosis and those who had recovered from pulmonary tuberculosis.

Five patients from each group were enrolled. Total RNA was extracted from peripheral blood mononuclear cells that had been incubated for 48 h with whole lysate of Mycobacterium tuberculosis (H37Rv, 0.5 microg/mL). Gene expression profiles were acquired using the GeneChip array and its applied systems. Gene expression profiles from five patients with previous extrapulmonary tuberculosis and one pooled control sample from five patients with previous pulmonary tuberculosis were analysed and compared. Genes that were expressed concordantly in more than 80% of arrays and that showed more than twofold changes in at least one array among samples from patients who had recovered from extrapulmonary tuberculosis were identified.

Compared with the control sample, the expression of 16 genes, including those for tumour necrosis factor (TNF)-alpha and cathepsin W, was increased, and the expression of 45 genes including that for TNF-receptor superfamily member 7 (TNFRSF7), was decreased in the extrapulmonary tuberculosis patients. The altered expression of the TNF-alpha, cathepsin W and TNFRSF7 genes was confirmed by quantitative RT-PCR.

Altered expression of the genes for TNF-alpha, cathepsin W and TNFRSF7 may be risk factors for the extrapulmonary dissemination of tuberculosis in humans.