Most vaccines provide protection by inducing the production of antibodies that can bind to a pathogen and block infection. Unfortunately, there are many dangerous viruses in which the development of a vaccine has been elusive despite decades of intense research. These failures highlight gaps in knowledge about the type of cell that can produce antibodies, the B cell. The Taylor lab aims to inform vaccine design by gaining a deeper understanding about the mechanisms limiting the generation of a protective B cell response. To do this, we study B cell responses in humans and murine models beginning with the rare pathogen-specific ³naive² B cells present prior to the vaccination using an enrichment method we recently developed. These approaches allow for the phenotypic and functional analysis of naive and activated B cells that target protective epitopes on candidate vaccine antigens such as HIV Envelope.