Genetic Analysis of Complement Component 9 (C9) Polymorphisms with Clearance of Hepatitis B Virus Infection

Background The complement component 9 ( C9 ), a major cytolytic protein in the complement system, plays an important role in the immunological process. However, associations between genetic variations of the complement factor and chronic hepatitis B virus infection still need to be investigated. Aims We hypothesized that genetic variations in the complement component 9 gene can influence the clearance of chronic hepatitis B virus infection, hepatocellular carcinoma occurrence, and onset age of hepatocellular carcinoma. To investigate the relationship between complement component 9 variations and these disease phenotypes, we performed a case–control association analysis in a Korean population. Methods Genetic variations were identified through direct DNA sequencing and genotyped using TaqMan assay ( n = 1,103). In order to investigate the relationship of complement component 9 with chronic hepatitis B virus clearance and hepatocellular carcinoma occurrence, differences in SNP and haplotype frequency distributions were analyzed using logistic and multiple regression analyses with adjusted age and gender as covariates. Results Although + 23189C > T polymorphism in exon 4 and C9_ht2 [T - G - C - A - C] were significantly associated with clearance of chronic hepatitis B virus infection and hepatocellular carcinoma occurrence, the association signals were not retained after multiple testing corrections. Conclusions We conclude that variations in the complement component 9 gene are unlikely to influence clearance of chronic hepatitis B virus infection and hepatocellular carcinoma occurrence. Although this preliminary result provides meaningful information, further functional investigations in other genetic factors for pathway analyses are required.