MHC class II genes influence the susceptibility to chronic active hepatitis C

Background/Aims: Chronic hepatitis C develops in more than 70% of hepatitis C virus infected subjects. Viral factors influence the disease course, but little is known about the importance of host factors. Methods: Frequencies of major histocompatibility complex (MHC) class I and class I antigens were analyzed in two groups of patients with chronic hepatitis C virus infection and in control subjects. MHC class I typing was done by standard microlymphocytotoxicity assays. DRB1 and DQA1 genotyping was done by PCR based typing methods. Results: DRB1*0301 was found in 26 of 75 patients with chronic hepatitis C virus infection (34.7%) and in 12 of 101 control subjects (11.9%) (relative risk 3.9; p<0.001). Homozygosity for this allele appeared to confer a stronger risk. In contrast, DRB1*1301 was detected in three subjects with persistent infection (4.0%) compared to 21 control subjects (20.8%) (relative risk 0.2; p<0.008). This allele was linked with DQA1*0103, which was found in 10 patients (13.3%) compared to 34 control subjects (33.7%) (relative risk 0.31; p<0.003). An even stronger protective effect was provided by the presence of DRB1*1301 and DQA1*0103 (relative risk 0.08; p<0.005). These findings were confirmed in a second group of chronic hepatitis C virus infected patients. Conclusions: The MHC class II allele DRB1*0301 appears to predispose to progression to chronic active hepatitis C, whereas the class II alleles DRB1*1301 and DQA1*0103 appear to provide protection against chronic active infection with hepatitis C virus.