HLA association with hepatitis C virus infection

Hepatitis is one of the most important infectious diseases in Thailand. The knowledge of host factors that influence the course of the disease is still limited. In this study, the HLA class I and class II phenotypes were analyzed in the 2 groups of HCV-infected Thai populations. The first group included 43 individuals with transient HCV infection (HCV antibody positive, HCV RNA PCR negative), and the second included 57 individuals with persistent chronic HCV infection (HCV antibody positive, PCR positive). HLA class I typing was performed by 2-stage microlymphocytotoxicity test, and HLA class II typing, by PCR-SSO. No significant difference in the frequencies of HLA-A and -B antigens was observed between the 2 groups of HCV-infected individuals. The frequency of DRB1*0301 and DQB1*0201 was significantly higher in the persistent-infection group than in the transient-infection group (Pc = 0.03, Pc = 0.04, respectively). In addition, DRB1*0701 and DQA1*0201 were significantly decreased in all the HCV-infected patients compared with levels in the normal controls (Pc = 0.003, Pc = 0.001, respectively). This study demonstrated that DRB1*0301 and DQB1*0201 are associated with persistent HCV infection, whereas DRB1*0701 and DQA*0201 are associated with protection against HCV infection.

HLA-A, -B, -DRB1, -DQA1, and -DQB1 polymorphism in Thais

In this study we examined HLA-A, -B, -DRB1, -DQA1, and -DQB1, gene allele, and haplotype frequencies in two ethnic Thai populations. We compared these frequencies to the known HLA class I and II allele profiles of non-Thai mainland and insular Southeast (SE) Asians. HLA-A locus gene and allele frequencies, are comparatively homogeneous in both Thai and non-Thai SE Asians. In contrast, HLA-B; -DRB1, -DQA1, and -DQB1 gene and allele frequencies, show more ethnic and geographic variation in SE Asians. Conserved haplotypes, or combinations of linked HLA class I and II alleles were detected in Thais, but at relatively low frequencies. It would appear that ethnic Thais, reflect an admixture of peoples from both the northern mainland and southern island groups of SE Asia.

HLA class I typing by one-dimensional isoelectric focusing and identification of the new variants in Thai population

One-dimensional isoelectric focusing (1D-IEF) is the technique to define HLA class I antigens based on difference in isoelectric point of HLA molecules. Different IEF subtypes are shown in different populations. In this study, 1D-IEF was employed to study HLA-A and -B subtypes in Thai population. A panel of 117 samples including all serologically defined HLA-A and -B antigens in Thai population were typed by 1D-IEF. Serological specificities and subtypes correlated well with IEF results and some antigens with unclear serological specificities could be confirmed by IEF. In addition, more subtypes could be obtained by IEF than by serology. A total of 17 IEF subtypes from HLA-A and 31 IEF subtypes from HLA-B could be identified. The subtypes predominantly found in Thai population were A2.3, A24.2, A11.1, A33.2, B15.2, B7.1 and B13.1. In addition, new IEF variants were identified in HLA-B35, B5, B56 and B48. The band positions of these variants were different from those previously described. These IEF subtypes are HLA gene products which may be important in transplantation. The combination of IEF and serology for HLA typing can provide a better definition of each allelic product of HLA-A and -B.