Global cell-free DNA methylation in patients with active tuberculosis and tuberculosis contacts with latent tuberculosis infection.

Introduction: To investigate whether the methylation of circulating cell-free DNA (cfDNA) differentiates active tuberculosis (TB) from latent TB infection (LTBI).

Methods: Patients with pulmonary TB, contacts with LTBI, and healthy controls were enrolled (2018-2021). Plasma cfDNA was extracted, and using a 5-methylcytosine (5mC) DNA ELISA kit, the global methylation of cfDNA (5mC-cfDNA) was measured.

Results: 59 TB, 63 LTBI, 39 healthy controls were included. The 5mC-cfDNA level was higher in TB (6.4 %) than LTBI (4.1 %) and healthy controls (4.9 %) (both p<0.05). Independent TB factors were 5mC-cfDNA ≥6.6 % and CRP ≥0.32 mg/dL (adjusted odds ratio (aOR) 4.594 [95 % CI:1.628-12.965], p=0.004 and 5.338 [1.659-17.176], p=0.005). Having one or both factors increased TB odds 8- and 16-fold (aOR 8.688 [3.229-23.378], p <0.001 and 16.080 [3.092-83.632], p =0.001).

Conclusion: The global cfDNA methylation level was higher in TB than contacts without TB and helped differentiate patients with TB from contacts with LTBI.