Regional Immune Response to Immunization with Escherichia coli O157:H7-Derived Intimin in Cattle

Escherichia coliO157:H7 is an enteric pathogen of animals and humans that can result in deadly sequelae. Cattle are asymptom-atic carriers and shedders of the bacteria and serve as an important reservoir of human infection. E. coliO157:H7 colonizes the gastrointestinal tract, most frequently at the rectoanal junctionmucosa in cattle. Vaccination is a potentially highly effective means of decreasing cattle colonization and shedding and thereby decreasing human infections. Currently available vaccines are administered subcutaneously or intramuscularly, and immune responses have been evaluated solely by systemic immunoglobu-lin responses. This study evaluated local and systemic lymphoproliferative responses in addition to immunoglobulin responses following subcutaneous or mucosal (rectal) immunization with E. coliO157:H7 outer membrane protein intimin over three tri-als. In all three trials, significant local and systemic lymphoproliferative responses (P< 0.05) occurred following immunization in the majority of animals, as well as significant immunoglobulin responses (P< 0.001) in all animals. Surprisingly, local re-sponses in the mesorectal lymph nodes were very similar between the subcutaneous andmucosal immunization groups. More-over, the responses in mesorectal lymph nodes appeared targeted rather than generalized, as minimal or no significant responses were observed in the associated prescapular lymph nodes of subcutaneously immunized animals. The results indicate that both subcutaneous and mucosal immunizations are effective methods of inducing immune responses against E. coliO157:H7 in cattle. Enterohemorrhagic Escherichia coli (EHEC) is an importantzoonotic pathogen in humans, causing self-limiting to sever