The effects of oral and combined parenteral/oral immunization against an experimental Escherichia coli urinary tract infection in mice.

A double oral immunization (PO/PO) with an outer membrane protein (OMP) from a human uropathogenic strain of Escherichia coli, resulted in the partial protection of mice infected per urethrally with the same strain. Complete protection was achieved by immunizing with OMP in Freund's complete adjuvant (FCA), intramuscularly (i.m.), followed by an oral boost (i.m./PO). The PO/PO protocol stimulated mainly local urinary antibody synthesis, particularly IgA, whilst the i.m./PO regimen resulted in the appearance of both serum and urine antibodies. A single dose of OMP, 6 days after infection, rendered the mice resistant to reinfection, in contrast to non-immunized mice, and led to a significant increase in urine, serum and bile IgA anti-OMP levels. Our results confirm previous reports that the urinary tract forms part of the common mucosal immune system and provides further evidence for immunological memory in mucosal immunity. These results also demonstrate that our OMP preparation is a highly effective immunizing antigen, and that such preparations may be suitable as oral vaccines against urinary tract infection in humans.