Studies on the immunogenicity of an Escherichia coli extract after oral application in mice.

A bacterial extract (IBEC, OM-89, Uro-Vaxom), consisting of immunostimulating components derived from 18 Escherichia coli (E. coli) bacterial strains, is used for the treatment of recurrent infections of the urinary tract. Previously it was demonstrated that IBEC constitutes an active immunogen after parenteral administration to mice. Here, the immunogenic properties of IBEC after oral administration to mice are demonstrated. It was shown that, after repeated oral administrations of the extract, an IBEC-specific serum immunoglobulin (Ig), IgA and IgG response was obtained. A weak increase of IBEC-specific faecal IgA was also observed. The sera also bound to the bacterial strains used for the preparation of the extract. Moreover they recognized the bacterial cell wall components muramyl dipeptide (MDP) protein I (porin) and lipopeptide (P3C). In addition to the increase of bacteria-specific Ig, a rise in total serum IgA was demonstrated. Also in supernatants of splenocyte cultures of IBEC-immunized mice an increased level of IgA could be determined. These findings on the immunostimulating properties of IBEC after oral administration, which is also the application route in human patients, might partially explain the therapeutic effect of the extract shown in clinical studies.