AEGiS-07IAC: HIV-1 gp120 and full length (FL) gp160 can bind to cells by different mechanisms.

7th International AIDS Conference

Florence, Italy — June 16-21, 1991

HIV-1 gp120 and full length (FL) gp160 can bind to cells by different mechanisms.

Int Conf AIDS 1991 Jun 16-21; 7:93 (abstract no. M.A.1007)
Kelker HC, Georgescu R, Valentine FT; NYU Medical Center, New York, NY 10016

OBJECTIVE: To compare the binding of several recombinant gp120s and gp160s to CD4 in an ELISA and a cellular system.

METHODS: We have examined the binding of env proteins to: 1) solid phase CD4 (Biogen) using an ELISA assay which we have developed, and 2) CD4+ cells (flow cytometry). Binding of gp120 produced by American Biotechnologies, Celltech, Chiron or MicroGeneSys (MGS), as well as FL gp160s produced by MGS or Repligen and a gp160 missing much of the transmembrane region (Pasteur Merieux) were assessed utilizing HIV+ immune globulin or a monoclonal antibody to gp41 to detect binding.

RESULTS: gp120 and FL gp160 bind to cells by different mechanisms, even though saturable binding was observed with both molecules. The modified gp160 binds to CD4 in the same manner as gp120. gp120s bind to solid phase CD4 in ELISA whereas FL gp160s bind poorly in this assay. Binding of all gp120 preparations to either recombinant CD4 or to CD4+ cells is blocked by OKT4A or preincubation with rCD4. Binding of modified gp160 also is inhibited by OKT4A. By contrast, binding of FL gp160, measured either by flow cytometry or by ELISA, is not inhibited by OKT4A. Preincubation of CD4+ cells with a saturating concentration of gp120 fails to block binding of FL gp160 suggesting that gp120 and FL gp160 bind to CD4+ cells at different sites. gp120 binds to CD4+ cells only, while FL gp160 binds also to some cells that do not express CD4, or have lost CD4. Half saturation of binding of MGS gp120 and FL gp160 to CD4 cells occurs at approximately the same concentrations. Half saturation of binding occurs at 5x10(-10)M Celltech gp120.

CONCLUSIONS: Binding characteristics of gp120 to CD4 are identical in an ELISA assay and a CD4+ cell assay. gp120 and FL gp160 bind to CD4+ cells by different mechanisms, whereas gp160 without some of the transmembrane region binds to the same determinants as gp120.

Keywords: AEGIS, Antigens, CD4, HIV-1, Gene Products, env, Receptors, HIV, HIV Antigens, HIV Antibodies, HIV, Antibodies, Monoclonal, HIV Seropositivity, HIV Infections, Recombinant Proteins, CD4-Positive T-Lymphocytes, Cells, Giant Cells, SK&F 106528, OKT4A, ICA7
910616
MA1007