HLA-DRB1 and HIV-1 infection: In the 3-locus haplotypes, frequencies of several common haplotypes such as A*11-B*46-DRB1*09, A*02-B*46-DRB1*08, A*02-B*46-DRB1*14, A*11-B*4001G- DRB1*15, A*02-B*4001G-DRB1*04, A*11-B*1501G-DRB1*04, A*11-B*46-DRB1*08 and A*02-B*4001G-DRB1*12 were observed to be higher in the HIV-1 positive group, suggesting these haplotypes could be susceptible factors for HIV-1 infection in Chongqing Han.