MULTIBRANCHED PEPTIDE CONSTRUCTS DERIVED FROM THE V3 LOOP OF ENVELOPEGLYCOPROTEIN GP120 INHIBIT HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTION THROUGH INTERACTION WITH CD4

The V3 loop of the gp120 of human immunodeficiency virus type 1 (HIV-1 ) is assumed to be involved in HIV-1-mediated membrane fusion. V3-deri ved peptides have been shown either to enhance or to prevent HIV-1 inf ection. Multibranched peptide constructs (MBPCs) derived from the vs N orth American/European consensus sequence were designed to sort out th ese conflicting findings. At 5 mu M, MBPC1 (8-branched GPGRAF) totally , and MBPC2 ([RKSIHIGPGRAFYT]4) partially, inhibited HIV-1(1A1) infect ion, whereas the GPGRAF monomer had only a limited effect. A peptide o f the entire V3 consensus loop and a control MBPC had no detectable ac tivity. The 5 mu M MBPC1 HIV-1-inhibiting concentration was not cytoto xic, nor did it alter T lymphocyte allogeneic, antigen-, or mitogen-in duced reactivities, and it was about 5- to 50-fold lower (MBPC2 and MB PC1, respectively) than that resulting in 50% cell death. Analysis of MBPC immunoreactivity showed that MBPC2, but not MBPC1, strongly react ed with human HIV-1 positive sera. Only MBPC2 elicited significant ant ibody responses in rabbits. The V3-derived MBPCs bound to CD4(+) cells , as determined by immunofluorescence analysis. The binding was inhibi ted either by soluble CD4 or by CD4 monoclonal antibody (mAb) MT151, w hich recognizes the CDR3 region of the D1 domain of CD4, but not by ot her CD4 mAbs Leu3a, OKT4A, Q4021, 13B8-2, 5A8, RFT4, nor by the CD26 m Ab BA5. Therefore, it appears likely that MBPCs inhibit HIV-1 infectio n by interacting with the CDR3 region of CD4 or with a region in its v icinity. (C) 1995 Academic Press, Inc.