The immunosuppressive peptide of HIV-1 gp41 like human type I interferons up-regulates MHC class I expression on H9 and U937 cells

Abstract

Based on our findings that the immunosuppressive peptide (ISP, amino acids (aa) 583–599) of human immunodeficiency virus type 1 (HIV-1) gp41 shows sequence-similarity with human type I interferons (IFN- α and IFN- β) and HIV-1 soluble gp41 (sgp41, aa 539–684) enhanced cell surface expression of major histocompatibility complex (MHC) class I molecule on human H9 (T cells), Raji (B cells) and U937 (monocytic cells) cells, we examined the effect of HIV-1 immunosuppressive peptide on the surface expression of MHC class I molecules on H9 and U937 cells. Flow cytometry analysis demonstrated that ISP-BSA (conjugate) could enhance MHC class I expression by about 40% on H9 cells and by about 45% on U937 cells, while monomer ISP (not conjugated) and EDCI-treated carrier protein (BSA-EDCI) did not increase the expression. By comparison, human type I interferons, IFN- α and IFN- β, showed similar effects (enhanced the expression by about 40–60%) to ISP-BSA on the MHC class I expression on H9 and U937 cells. The results suggest that HIV-1 gp41 in a polymerized form by its immunosuppressive domain upregulates human MHC class I expression. The basis for this similar effect of HIV-1 gp41 and IFN- α and - β, i.e. upregulation of MHC class I molecule expression, may be based on the sequence-similarity between these otherwise different molecules.