Vaccine-induced antibodies to the native, oligomeric envelope glycoproteins of primary HIV-1 isolates.

A simple and sensitive method for measuring antibodies to primary human immunodeficiency virus type 1 (HIV-1) isolates has been developed. The flow cytometric immuno-fluorescence assay detects antibodies that bind to the native, oligomeric form of the envelope glycoprotein (gp120) expressed on the surface of PM-1 cells infected with primary isolates of HIV-1. Sera from people infected with HIV-1 or those immunized with recombinant gp120 vaccines were tested. Significant correlation was observed between neutralizing activity and oligomeric gp120 binding activity. Thirteen to 100% of individuals immunized with the subtype B bivalent vaccine AIDSVAX B/B developed oligomeric gp120 binding antibodies against a variety of subtype B primary isolates. For several isolates, AIDSVAX B/B sera reacted better than monovalent AIDSVAX B sera, suggesting that addition of the second immunogen improved the breadth of the antibody response. Cross-subtype binding activities, induced by AIDSVAX B/B, were lower than activities to subtype B isolates, suggesting that additional immunogen(s) may be desirable in vaccine(s) formulated for geographic regions where non-B subtypes are dominant.

A region of the Yersinia pseudotuberculosis invasin protein that contributes to high affinity binding to integrin receptors.

The entry of Yersinia pseudotuberculosis into cultured mammalian cells is mediated by the bacterial protein invasin. The mammalian receptors for invasin are five beta1 chain integrins. Site-directed mutagenesis of the aspartate and lysine residues in the 192-amino acid integrin binding domain of invasin was performed to identify regions, in addition to the previously characterized 903-913 region, that are important for integrin binding. One mutation, D811A, resulted in depressed ability of invasin to bind purified alpha5beta1 and to promote bacterial entry. Further mutational analysis of Asp-811 indicated that an oxygen-containing side chain is required at this position. A second nearby residue, Phe-808, was also shown to be important for integrin binding, as an alanine substitution at this site had properties similar to the Asp-811 mutation. This mutational analysis has therefore identified a second region that, in conjunction with residues 903-913, is required for wild type levels of integrin binding. The contribution to binding by two noncontiguous sites in the primary sequence parallels results that indicate two domains of fibronectin are involved in integrin binding.