Delimiting a conserved vaccine target on HIV-1

HIV-1 gp41 contains highly conserved regions that are involved in mediating virus entry into cells by promoting membrane fusion. One such region is the membrane-proximal external region (MPER) of gp41, and the human monoclonal antibodies (mAbs) that bind to it, 2F5, 4E10 and Z13e1, neutralize primary isolates of HIV-1 from different clades. These results emphasize gp41 as an attractive candidate for HIV-1 vaccine development. However, eliciting neutralizing Abs against gp41 has been problematic. This is due in part to heterogeneity in gp41 structure and a poor understanding of the specific structure and presentation of the neutralizing epitopes on HIV-1 gp41. A series of gp41 mimetics that specifically present the minimal neutralizing epitopes on the MPER of gp41 have been designed at the Zwick laboratory. These gp41 mimetics will be used to immunize rabbits. In order to gain specific knowledge about the immunogenicity of the neutralizing epitopes, rabbit mAbs that were elicited to these epitopes will be rescued by phage display and tested individually for neutralizing activity (Aim 1). The mAb panels will be used to probe the gp41 mimetics, and then modifications will be introduced so as to favorably display the neutralizing epitopes and occlude the non-neutralizing ones (Aim 2). In addition, in a collaborative effort with the Wilson group at TSRI, the structure of the human Fab Z13e1, in complex with its cognate epitope peptide, will be determined using Xray crystallography (Aims 3). In these ways, antibody access to the MPER of gp41 will be precisely evaluated, which in turn should lead to improved gp41-based immunogens that elicit more potent neutralizing Abs against HIV-1.