Outer membrane PhoE protein of Escherichia coli as a carrier for foreign antigenic determinants: immunogenicity of epitopes of foot-and-mouth disease virus

Outer membrane protein PhoE of Escherichia coli was used for the expression of antigenic determinants of foot-and-mouth disease virus. Five hybrid PhoE proteins were constructed containing different combinations of two antigenic determinants of VP1 protein of the virus. The hybrid proteins were expressed in two E. coli strains and the proteins were correctly assembled into the outer membrane. The inserted epitopes were exposed at the surface of the cell and were antigenic in this PhoE-associated conformation. Immunization experiments, performed with partially purified protein, resulted in all cases in a significant anti-peptide antibody titre. In one case in which the hybrid protein with the largest insert was used, a neutralizing antibody response was detected.