Centralized administration is critical for efficient project management, coordination, and execution. Core A (Administrative Core) will provide all the logistic, scientific, managerial, financial, and biostatistics support to facilitate and to coordinate the studies described in this Consortium. The Administrative Core will ensure that all the Projects and Cores function optimally and adhere to the timelines described in the individual sections of this grant. The Administrative Core will establish a Scientific Leadership Committee as the primary decision making committee for this Consortium, organize conference calls every two weeks and regular in-person meetings, maintain regulatory approvals, provide fiscal and logistic oversight, manage subcontracts, and coordinate meetings with the Scientific Advisory Board and DAIDS Program Officials. This detailed administration and management structure will ensure that all the studies remain focused on the overall objective to evaluate the early events of acute mucosal SIV/SHIV infection and the capacity of vaccines to impact these events. To accomplish these goals, we propose the following five Specific Aims: 1. To coordinate communications, interactions, and operations among investigators, Projects, and Cores to facilitate the overall progress and goals of this Consortium; 2. To ensure and to maintain regulatory compliance; 3. To provide detailed financial oversight and management; 4. To coordinate meetings with the Scientific Advisory Board and DAIDS Program Officials; and 5. To provide biostatistics support for all Projects and Cores.