This project resulted in two peer-reviewed journal publications in FY2014. We established an improved humanized mouse model for the study of immune responses to HIV infection and vaccination. The model utilizes severely immunocompromised mice reconstituted with human thymic and liver tissue, which establishes human lymphocytic and monocytic populations susceptible to HIV infection. The mice support both intravenous and mucosal HIV infection and develop HIV-specific B and T cell immunity. A distinct advantage of this model is that the mice do not develop graft versus host disease and can therefore be used in long-term studies of HIV infection not previously possible.