Abstract： Objective To study the impact of HIV and hepatitis C virus ( HCV ) infection on peripheral expression of antiviral protein A3G and plasma IFN-αlevels.Methods Untreated patients with chronic hepatitis C(HCV infection group, n=43), AIDS(HIV infection group, CD4 +T<200 cells/μL, n=45) and HIV/HCV co-infection (CD4 +T<200 cells/μL, n=45) were recruited in the study, and 23 healthy subjects were also enrolled as controls.A3G mRNA in peripheral blood mononuclear cells (PBMC) was measured by quantificational real-time PCR, and plasma IFN-αlevel was determined by enzyme linked immunosorbent assay (ELISA).Rank-sum test and Spearman rank correlation analysis were performed. Results A3G mRNA levels in HIV infected group, HIV/HCV co-infected group, HCV infected group and&nbsp;healthy control group were 4.89 (0.59), 4.85 (0.71), 3.89 (1.08) and 3.69 (0.81) lg copies/mL, respectively.A3G mRNA levels in HIV infected group and HIV/HCV co-infected group were much higher than those in healthy control group (Z=-6.306 and -6.280, P<0.01) and HCV infected group (Z=-7.358 and -7.275, P<0.01).Plasma IFN-αlevels in HIV infected group, HIV/HCV co-infected group, HCV infected group and healthy control group were 2.79 (1.25), 2.05 (1.29), 2.32 (1.84) and 2.16 (2.19) pg/mL, respectively.Plasma level of IFN-αin HIV infected group was higher than that in the HIV/HCV co-infected group (Z=-2.332, P<0.05), but no significant difference was observed among other groups (all P>0.05).There was no significant correlation between plasma IFN-αlevel and A3G mRNA expression (rs =0.04, P>0.05), and the levels of A3G mRNA and IFN-αshowed no correlation with HIV RNA and HCV RNA (all P>0.05).Conclusions A3G is highly expressed in PBMCs from HIV infected patients, and it may not be affected by the infection of HCV.A3G mRNA is not closely correlated with IFN-α, and it has not significant influence on HIV RNA and HCV RNA replication.