The
glycosphingolipid galactosylceramide (GalCer), which binds gp120 with high affinity and specificity, is a potential alternative receptor for human immunodeficiency virus type 1 (HIV-1) in some CD4-negative neural and epithelial human cells, including the human colonic epithelial cell line HT-29. In the present study, we demonstrate that synthetic multibranched
peptides derived from the consensus sequence of the HIV-1 V3 loop block HIV-1
infection in HT-29 cells. The most active
peptide was an eight-branched multimer of the motif
Gly-Pro-Gly-Arg-Ala-Phe which at a concentration of 1.8 microM induced a 50% inhibition of HIV-1
infection in competition experiments. This
peptide was not toxic to HT-29 cells, and preincubation with HIV-1 did not affect viral infectivity, indicating that the
antiviral activity was not due to a nonspecific virucidal effect. Using a high-performance thin-layer chromatography binding assay, we found that multibranched V3
peptides recognized GalCer and inhibited binding of recombinant gp120 to the
glycosphingolipid. In addition, these
peptides abolished the binding of an anti-GalCer
monoclonal antibody to GalCer on the surface of live HT-29 cells. These data provide additional evidence that the V3 loop is involved in the binding of gp120 to the GalCer receptor and show that multibranched V3
peptides are potent inhibitors of the GalCer-dependent pathway of HIV-1
infection in CD4-negative mucosal epithelial cells.