Modulating the immunological properties of a linear B-cell epitope by insertion into permissive sites of the MalE protein.

In a previous study, a set of positions in the MalE protein from Escherichia coli were identified, which tolerated short insertions or deletions without compromising the maltose binding activity of the protein. It is now shown that these sites accommodate an insert of 13 amino acids and are, therefore, permissive. Eleven sites were used, including eight permissive sites, to display a linear neutralization B-cell epitope of poliovirus (C3 epitope) at different positions on the surface of MalE. The affinity of a monoclonal neutralizing anti-poliovirus antibody (anti-C3 mAb) for the hybrid proteins varied from undetectable, to more than 1000 times higher than for the synthetic peptide. Therefore, some MalEC3 proteins mimic interactions of the viral epitope with the monoclonal antibody more efficiently than the free peptide. The results are interpreted in terms of the mobility of the insert and its flanking regions. It was further shown that some of the purified hybrid proteins are able to induce high titer anti-C3-peptide antibodies in mice. A strong correlation exists between the capacity of a MalEC3 protein to induce anti-C3-peptide antibodies and the antigenicity of the inserted peptide, measured with a polyclonal serum raised against the synthetic peptide.