The Journal of biological chemistry 2017 11 29() pii 10.1074/jbc.M117.816447
Recent discoveries of broadly neutralizing antibodies (bnAbs) in HIV-1-infected individuals have led to the identification of several major ″vulnerable sites″ on the HIV-1 envelope (Env) glycoprotein. These sites have provided precise targets for HIV-1 vaccine development, but identifying and utilizing many of these targets remains technically challenging. Using a yeast surface display-based approach, we sought to identify epitope-focused antigenic domains (EADs) containing one of the ″vulnerable sites″, the CD4-binding site (CD4bs), through screening and selection of a combinatorial antigen library of the HIV-1 Env glycoprotein with the CD4bs bnAb VRC01. We isolated multiple EADs and found that their trimeric forms have biochemical and structural features that preferentially bind and activate B cells that express VRC01 in vitro. More importantly, these EADs could induce detectable levels of neutralizing antibodies against genetically related autologous and heterologous subtype B viruses in guinea pigs. Our results demonstrate that an epitope-focused approach involving a screen of a combinatorial antigen library is feasible. The EADs identified here represent a promising collection of possible targets in the rational design of HIV-1 vaccines and lay the foundation for harnessing the specific antigenicity of CD4bs for protective immunogenicity in vivo.