Antiretroviral therapy (ART) aims at suppressing viral replication and strengthening immune system in patients with HIV-1. Human Leukocyte Antigens (HLA) are among factors responsible for effectiveness of ART. The aim of this study was to determine the effect of HLA Class II alleles on the response to long-time ART, assessed by a change in CD4+ T-cell count in relation to viral load. The sample included 69 patients (17 females and 52 males) aged 20 to 50 with HIV-1 infection, who were undergoing ART in the Latvian Centre of Infectious Diseases. The median period of observation was 5.7 years. CD4+ T-cell count and viral load were analysed at the baseline and end of the period of observation. HLA typing was performed by polymerase chain reaction with low resolution sequence specific primers. Multiple hierarchical linear regression analysis confirmed that an increase in HIV-1 viral load was associated with a decrease in the level of CD4+ T-cell count. In addition, HLA-DRB1*04 and HLA-DQB1*06:01 alleles contributed negatively to the level of CD4+ T-cell count.