Project Summary The specific objective of the Clinical Core is to provide human specimens for the studies outlined in Research Projects (RP) 1-3. These human specimens will supplement the existing extensive collection of unique banked specimens that are future-use consented and which will be available for use in RP1-3. These specimens include specimens from unique immunization and/or challenge studies conducted at Maryland, against S. Typhi, Non- Typhoidal Salmonella, and Shigella species. Of particular note, as specified in RFA-AI-22-069, support is requested to obtain additional human specimens only from clinical studies involving subjects who are receiving licensed vaccines. Blood and duodenal and/or terminal ileum biopsies, from subjects undergoing medically indicated endoscopy who consent to receive the Ty21a oral typhoid vaccine, will be collected under Protocol CVD 38000. Blood will also be collected from un-vaccinated controls (Blood Donor CVD 4000) and Ty21a vaccinated individuals (Blood Donor CVD 5000). The Clinical Core will provide the infrastructure to collect these unique human clinical specimens, which will supplement the already extensive existing specimen bank. The leadership of the clinical core are composed of two experienced physician-scientists who also provide patient care within the University of Maryland Medical Center (UMMC) or as part of the Faculty Practice Office of the University of Maryland School of Medicine (UMSOM). The clinical core is also staffed by experienced nurse s that have been trained in GCP and are well acquainted with the research protocols to be utilized for our studies. The resources being made available through the clinical core and the patient volumes (clinical activity) of the involved clinics should ensure that sufficient human specimens will be provided for the in-depth immunological studies proposed in this CCHI application.