Humbert, MichaelRasmussen, RobertOng, HelenaKaiser, Fabian M. P.Hu, Shiu-LokRuprecht, Ruth Margrit2011-06-142008Humbert, Michael, Robert A. Rasmussen, Helena Ong, Fabian M. P. Kaiser, Shiu-Lok Hu, and Ruth M. Ruprecht. 2008. Inducing Cross-Clade Neutralizing Antibodies against HIV-1 by Immunofocusing. PLoS ONE 3(12): e3937.1932-6203http://nrs.harvard.edu/urn-3:HUL.InstRepos:4911721Background: Although vaccines are important in preventing viral infections by inducing neutralizing antibodies (nAbs), HIV-1 has proven to be a difficult target and escapes humoral immunity through various mechanisms. We sought to test whether HIV-1 Env mimics may serve as immunogens. Methodology/Principal Findings: Using random peptide phage display libraries, we identified the epitopes recognized by polyclonal antibodies of a rhesus monkey that had developed high-titer, broadly reactive nAbs after infection with a simian-human immunodeficiency virus (SHIV) encoding env of a recently transmitted HIV-1 clade C (HIV-C). Phage peptide inserts were analyzed for conformational and linear homology using computational analysis; some peptides mimicked various domains of the original HIV-C Env, such as conformational V3 loop epitopes and the conserved linear region of the gp120 C-terminus. Next, we devised a novel prime/boost strategy to test the immunogenicity of such phage-displayed peptides and primed mice only once with HIV-C gp160 DNA followed by boosting with mixtures of recombinant phages. Conclusions/Significance: This strategy, which was designed to focus the immune system on a few Env epitopes (immunofocusing), not only induced HIV-C gp160 binding antibodies and cross-clade nAbs, but also linked a conserved HIV Env region for the first time to the induction of nAbs: the C-terminus of gp120. The identification of conserved antigen mimics may lead to novel immunogens capable of inducing broadly reactive nAbs.en-USimmunologyinfectious diseasesvirologyJournal Article2011-06-1410.1371/journal.pone.0003937