TGFB1 and chronic hepatitis C virus infection: This study’s main objective was to investigate the possible association between chronic hepatitis C virus infection susceptibility and cytokine gene polymorphism for interleukin-10 (IL-10) (rs1800896 and rs1800871), interleukin 6 (IL-6) rs1800795, TNF-α rs1800629, and TGF-β1 rs1800471 in Malay male drug abusers.