ABSTRACT: Core 2. Analytical Resources Core The Analytical Resources Core (Core 2) will contribute to the overall Program goals and to each Project by exploring the specific hypothesis that the structural and biophysical/chemical features of antibody recognition will define mechanisms associated with potent or weak effector function and similarities and differences in antibody biology between species relevant to vaccine and antibody therapy outcomes. The Core will provide key services for biophysical, biochemical, and structural characterization of Ab interactions, complemented by central analysis of data collected through Projects 1, 2, and 3, for synthesis to define key similarities and differences between NHP and humans in terms of Ab and effector cell biology. The specific aims of this core are as follows: AIM 1. Determine and optimize FcR binding profiles of Program antibodies and immune complexes. AIM 2. Determine co-crystal structures of relevant Program Ab:antigen and Ab:Fc receptor pairs. AIM 3. Model the knowledge of paratope and Fc function to define optimal antibody features for Fc- mediated antiviral activities. Through these aims, this Core will serve the needs of all three Projects and provide key contributions to achieving the shared goals of this Program.