VACCINE-SPECIFIC T-CELLS IN HUMAN PERIPHERAL-BLOOD AFTER ORAL IMMUNIZATION WITH AN INACTIVATED ENTEROTOXIGENIC ESCHERICHIA-COLI VACCINE

We have examined whether oral immunization of adult Swedish volunteers with a prototype enterotoxigenic Escherichia call vaccine would induc e antigen-specific T-cell responses in blood. Volunteers were given on e to three doses ofthe whole-cell component of the vaccine, which cons isted of formalin-inactivated bacteria expressing the fimbrial coloniz ation factor antigens I and II. Following immunization, in vitro stimu lation of blood mononuclear cells with the colonization factor antigen s resulted in modest proliferative responses which were accounted for mainly by CD4(+) T cells and, to a lesser extent, by CD8(+) T cells. A main finding of this study was that a majority of the orally immunize d volunteers had circulating T cells capable of producing large quanti ties of gamma interferon following in vitro exposure to either of the colonization meter antigens. No interleukin 2 production could be dete cted in the cell cultures. These results suggest that oral immunizatio n of humans induces the migration of specific mucosal T immunocytes fr om the intestine into peripheral blood.