Expression of a poliovirus neutralization epitope at the surface of recombinant bacteria: first immunization results

We devised a procedure to construct strains of Escherichia coli which expose at their surface a foreign antigen genetically inserted into LamB, an outer membrane protein. In particular, we showed that amino acid residues 93-103 of poliovirus type 1 capsid polypeptide VP1, which correspond to the C3 neutralization epitope, when inserted into two different external loops of LamB (after residues 153 and 374 of the mature protein), yielded the synthesis of stable hybrid proteins named, respectively, 153-C3 and 374-C3. The poliovirus epitope was accessible to monoclonal antibody C3 at the cell surface. In the present work, these two hybrid proteins were injected into rabbits by the intravenous route in the form of live recombinant bacteria, and the humoral response to the poliovirus epitope was studied. With construction 153-C3, the subcutaneous route was also assayed using solubilized hybrid protein. The C3 viral sequence inserted in the two different regions of LamB were found to be immunogenic. Different types of antibodies specific to the C3 peptide were raised with the two construction: anti-peptide and antiviral particle antibodies. These first results indicate that the LamB presentation vector system constitutes a mode of peptide coupling which may lead to the elaboration of a new type of live vaccine.