Association between TLR7 copy number variations and hepatitis B virus infection outcome in Chinese

AIM: To explore whether copy number variations (CNVs) of toll-like receptor 7 (TLR7) are associated with susceptibility to chronic hepatitis B virus (HBV) infection. METHODS: This study included 623 patients (495 males and 128 females) with chronic hepatitis B virus infection (CHB) and 300 patients (135 females and 165 males) with acute hepatitis B virus infection (AHB) as controls. All CHB patients were further categorized according to disease progression after HBV infection (CHB, liver cirrhosis, or hepatocellular carcinoma). Copy numbers of the TLR7 gene were measured using the AccuCopy method. χ(2) tests were used to evaluate the association between TLR7 CNVs and infection type. P values, odds ratios, and 95% confidence intervals (CIs) were used to estimate the effects of risk. RESULTS: Among male patients, there were significant differences between the AHB group and CHB group in the distribution of TLR7 CNVs. Low copy number of TLR7 was significantly associated with chronic HBV infection (OR = 0.329, 95%CI: 0.229-0.473, P < 0.001). Difference in TLR7 copy number was also found between AHB and CHB female patients, with low copy number again associated with an increased risk of chronic HBV infection (OR = 0.292, 95%CI: 0.173-0.492, P < 0.001). However, there were no significant differences in TLR7 copy number among the three types of chronic HBV infection (CHB, liver cirrhosis, or hepatocellular carcinoma). In addition, there was no association between TLR7 copy number and titer of the HBV e antigen. CONCLUSION: Low TLR7 copy number is a risk factor for chronic HBV infection but is not associated with later stages of disease progression.