. . . . . . "HIV-1 Vpu binds to NK-T- and -B cell antigen (NTB-A) through its transmembrane region (residues 4-28)" . "HIV-1 Vpu downregulates NTB-A on infected T cells. Vpu does not increase NTB-A endocytosis or degradation within lysosomes. Vpu-mediated downregulation of NTB-A protects the HIV infected cell from lysis by NK cells" . "downregulates" . "binds" .