Objective:To study the expression of human leukocyte antigen G (HLA-G) during human T lymphocytic leukemia virus type 1 (HTLV-1) infection, and to investigate the function and mechanism of HLA-G in HTLV-1 immune escape.Methods:HeLa and THP-1 cells were infected by MT2, a stable HTLV-1 infected cell line. Expression of HLA-G isomers at mRNA and protein levels was detected by qRT-PCR and Western blot, respectively. Flow cytometry was used to detect the expression of HLA-G1. Moreover, transfection and siRNA gene were respectively used to up-regulate and silence HLA-G expression in HeLa cells to observe the changes in the expression of HTLV-1-featured protein Tax on protein level after HTLV-1 infection.Results:HTLV-1 infection could induce differential expression of HLA-G isomers, mainly HLA-G1 and HLA-G5, in HeLa and THP-1 cells. HLA-G expression at both mRNA and protein levels was significantly up-regulated 24 h after HTLV-1 infection. Moreover, the expression of HTLV-1 protein Tax was significantly enhanced in HTLV-1-infected HeLa cells overexpressing HLA-G. An opposite result was obtained when the HLA-G gene in HeLa cells was silenced by siRNA.Conclusions:The immune-tolerant molecule HLA-G was significantly increased in HTLV-1-infected cells, thereby promoting the expression of HTLV-1 viral protein, which led to persistent viral infection.