This project focuses on the immunology, immunoprophylaxis, and microbiology of acute intestinal infections: viral, bacterial and parasitic. Environmental antigens, especially in the gut, have been shown to be required for clonal expansion of B-cells; these primed cells are found both at mucosal surfaces and systemically. Further studies will address the role of T-cells in mucosal priming of B-cells and in isotype preference and idiotype control. Intestinal inflammation by Nippostrongylus brasiliensis has been shown to have distinct, possibly immune-mediated, effects of granulopoeisis. Lymphocyte migration during primary and secondary types of mucosal immune responses has been more fully defined. The mucosal immune system displays disseminated priming but focused IgA antibody production. This has relevance for approaches to topical immunization. Parenteral immunization is usually suppressive of the mucosal immune response and mechanisms for this effect have been partly defined. An adult rabbit model for studying immune responses to killed or live antigens of V. cholerae and toxigenic E. coli has been developed. This will be used in studies of potential live E. coli vaccines. live cholera vaccines, and for investigation of basic immune mechanisms which protect the intestinal mucosa. The biologic properties of SA-11, a rotavirus, have been studied. The proteins of the rotaviruses, SA-11 and a porcine rotavirus have been compared. Serologic studies of persons with traveller's diarrhea suggest that rotavirus infection occurs frequently during such episodes.