Human immunodeficiency virus type 2 envelope glycoprotein binds to CD8 as well as to CD4 molecules on human T cells

Abstract

We report here that human immunodeficiency virus type 2 (HIV-2) envelope glycoprotein (gp105), but not HIV-1 gp120, can bind to CD8 molecules as well as to CD4 molecules on human T cells. This phenomenon may lead to differences in the life cycles of HIV-1 and HIV-2, and it may be related to the differences in disease manifestations of HIV-1 and HIV-2 infection, including longer survival of HIV-2-infected patients.

Binding of HIV‐2 envelope glycoprotein to CD8 molecules and related chemokine production

“…We recently reported that HIV‐2/gp105 (but not HIV‐1/gp120) bound to CD8 + T cells as well as CD4 + T cells purified from PBMC in a HIV‐2/gp105 concentration‐dependent fashion. 10 This HIV‐2/gp105 binding was observed in a CD4 − CD8 + human T‐cell line (a variant of MOLT‐4 cells) and a human CD8‐transfected mouse T‐cell hybridoma, in addition to human CD8 + T cells. We also reported that the binding site of HIV‐2/gp105 was located on the α‐chain of CD8 and not the β‐chain, and that it overlapped with the site for a Leu 2a antibody.…”

“…We also reported that the binding site of HIV‐2/gp105 was located on the α‐chain of CD8 and not the β‐chain, and that it overlapped with the site for a Leu 2a antibody. 10 The decrease of Leu 2a antibody binding to CD8 + T cells treated with HIV‐2/gp105 was thought to be due to competition for binding between HIV‐2/gp105 and the antibody ( Fig. 1f).…”

“…Unlabelled and fluorescein isothiocyanate (FITC)‐labelled recombinant HIV‐2 envelope glycoprotein gp105 (HIV‐2rod) (HIV‐2/gp105) and HIV‐1 envelope glycoprotein gp120 (HIV‐1iiib) (HIV‐1/gp120) were obtained from a baculovirus‐expression system (Intracel Co., Issaquah, WA). Our previous experiments showed that 1 μg/ml of these envelope proteins was sufficient to occupy all the cell surface receptors, 10–13 so this concentration was used in the present study.…”

“…9 In addition, we recently reported that the envelope glycoprotein of HIV‐2 (but not HIV‐1) can bind to CD8 molecules on human T cells, and that the binding site of this HIV‐2 envelope glycoprotein is situated on the α‐chain of CD8 molecules. 10 In this report, we provide information on the relationship between binding of the HIV‐2 envelope glycoprotein to CD8 and the production of β‐chemokines in vitro . In comparison to HIV‐1, HIV‐2 has a lower potential to cause disease.…”

Monocyte‐mediated T cell suppression by HIV‐2 envelope proteins

“…A more "open" structure of gp105 is thought to explain the broader range of co-receptor usage by HIV-2 than HIV-1 isolates [21] and the higher levels of neutralizing antibodies documented in HIV-2infected patients [22]. Moreover, gp105 ROD was shown to bind to the CD8 molecule with high affinity, whereas HIV-1 IIIB gp120 was unable to [23]. We show here that HIV-2 Env markedly suppresses TCR-mediated responses through a mechanism dependent upon the contact between monocytes and T cells.…”