The HCV infection is considered a multifactorial disease influenced by environmental and host factors. Host factors such as the innate and adaptive immune response play a crucial role in the outcomes of HCV infection (
6,
29). It has been proposed that HLA molecules are the host factors that may influence the efficiency of the antiviral immune response to HCV infection. Various studies have confirmed that polymorphisms in HLA loci are associated with the outcome of HCV infection (
6). Identifying these polymorphisms may help better understand the immune mechanisms of HCV clearance or persistence. The objective of this meta-analysis was to establish the updated information about the association of HLA class II alleles with clearance or persistence of HCV infection. The results showed that subjects carrying HLA-DQB1*0301, HLA-DQB1*0501, HLA-DRB1*1303, HLA-DRB1*1201, HLA-DRB1*0401, HLA-DRB1*0101, and HLA- DRB1*1101 alleles were significantly associated with higher spontaneous HCV clearance. These findings are almost similar to a previous systematic review conducted by Gauthiez et al. that reported HLA-DRB1*1101, HLA-DRB1*1201, HLA-DRB1*0101, and HLA-DQB1*0301 alleles were associated with HCV clearance (
30). For HLA-DQB1*0501, HLA-DQB1*0603, and HLA-DRB1*1301 alleles, in contrast to our study, Gauthiez et al. reported a lack of association with HCV clearance (
30). These inconsistent results may be due to the differences in the number of studies and the number of populations included in the meta-analysis. For example, for the HLA-DRB1*1301 polymorphism, we included four additional investigations in our meta-analysis compared to the meta-analysis published by Gauthiez et al. in 2017 (
30). In addition, in 2005, a meta-analysis evaluated the association of HLA-DQB1*0301 and HLA-DRB1*1101 alleles with the outcome of HCV infection and reported that subjects carrying HLA-DQB1*0301 and HLA-DRB1*1101 alleles showed a reduced risk of developing chronic HCV infection (
31), which is similar to this study and Gauthiez et al.'s meta-analysis (
30). The results of our study also are in agreement with the results of studies by McKiernan et al. (
18) and Thio et al. (
19) that found the HLA-DQB1*0501 allele was associated with HCV clearance; however, in contrast to our study, Romero et al. reported that this allele was associated with persistent HCV infection (
22). These contradictory results may be due to sample size and ethnic differences. It has been proposed that both viral genotype and host ethnicity can influence immunity against HCV infection. The relationship between HCV clearance and certain HLA alleles appears to be racially and geographically specific (
19,
32). Therefore, well-designed studies in multiple regions are needed to confirm these results.
Some limitations exist in the present study that should be noted. First, the sample size in some of the included studies was small; therefore, further studies are needed to confirm the results. Second, the studies included in the present meta-analysis varied in the HLA typing technique, which may have affected the obtained results of this study. Third, some data were not included in the analysis since their original language was not English. Finally, some HLA class II polymorphisms were assessed in only two or three studies; therefore, more studies are needed to determine the association of HLA class II alleles with HCV outcome.
Taken together, the present meta-analysis provides detailed data on the association of HLA class II polymorphisms with HCV outcome. In the current meta-analysis, HLA-DQB1*0301, HLA-DQB1*0501, HLA- DRB1*1303, HLA-DRB1*1201, HLA-DRB1*0401, HLA-DRB1*1101, and HLA-DRB1*0101 alleles were significantly associated with higher spontaneous HCV clearance, whereas HLA-DQA1*0601, HLA-DQB1*0603, HLA-DQB1*0502, HLA-DQB1*0201, HLA-DRB1*1301, HLA-DRB1*1302, HLA-DRB1*0701, and HLA-DRB1*0301 alleles were associated with lower probability of spontaneous HCV clearance. Identifying an association between HLA class II polymorphisms and HCV outcome may open new insights to better understand the immune mechanisms of HCV clearance or persistence.