Human immunodeficiency virus 1 downregulates cell surface expression of the non-classical major histocompatibility class I molecule HLA-G1

Human immunodeficiency virus 1 (HIV-1) downregulates cell surface expression of HLA-A and HLA-B but not HLA-C or HLA-E to ultimately escape immune defences. Here, it is shown that cell surface expression of the non-classical HLA-G1 is also downregulated by HIV-1, by using co-transfection experiments and infection with cell-free HIV-1 of HLA-G1-expressing U87 glioma cells or macrophages in primary culture. Moreover, co-transfection experiments using proviruses; deleted in either nef or vpu or plasmids encoding HIV-1 Nef and Vpu mixed together with a HLA-G1-expressing construct demonstrated that HLA-G1 downregulation is Nef-independent and Vpu-dependent, contrasting with the Nef- and Vpu-dependent HLA-A2 downregulation. Together, these results show that the decrease of HLA-A2 and HLA-G1 caused by HIV-1 occurs through distinct mechanisms.