Biological activity of bacterial cell wall components. Immunogenicity of an immunostimulating bacterial extract

An immunostimulating bacterial extract (IBE, Broncho-Vaxom) used for the prevention and treatment of recurrent respiratory tract infections consists of lyophilized fractions derived from 21 bacterial strains occurring in these infections. The immunogenic properties of IBE were determined in vivo in a murine model. It could be demonstrated that the extract constitutes an active immunogen in Balb/c mice. As shown by ELISA, IBE-specific antisera could be obtained after repeated i.p. immunizations; the antibodies were mainly of the IgG and IgM isotypes. The antibodies also bound - to a variable degree - to the bacterial strains used for the preparation of the extract. Additionally the antisera were shown to recognize the bacterial cell wall components porin, lipoprotein/lipopeptide and murein. Thus, IBE constitutes an active immunogen in vivo inducing antibodies directed against bacterial cell wall components; this could be of importance for understanding the therapeutic effect of the extract.