Methylation status of alu repetitive elements in children with tuberculosis disease.

Background: Investigation of DNA methylation in Alu repetitive elements (REs) was shown to be a promising field to explore transcriptional changes in human genome under disease condition. To scrutinize the association between Alu methylation and tuberculosis (TB) disease in children, the difference in Alu DNA methylation level was compared with healthy controls.

Methods: Whole-blood genomic DNA from 36 TB-infected children and 32 healthy controls was isolated, and the level of Alu repeat DNA methylation was examined by methylation-specific polymerase chain reaction.

Results: The median Alu methylation level in TB patients was 30% (Interquartile range [IQR], 25-30%), whereas in healthy controls, it was 75% (IQR, 50-75%) (P < 0.0001). The median level of DNA methylation of Alu RE in TB cases was significantly lower than healthy controls. Receiver operating characteristic curve analysis showed that the area under the curve for diagnosis was 0.969 (95% confidence interval, 0.936-1) (P < 0.0001), with 100% sensitivity and 84% specificity.

Conclusion: Our results point out that detection of Alu DNA methylation in whole-blood DNA may be clinically useful tool for the diagnosis and prognosis of TB disease in children.