Targeting vaccinia virus-expressed secretory beta subunit of human chorionic gonadotropin to the cell surface induces antibodies.

We carried out experiments designed to study the effect of a protein's localization on its immunogenicity. A novel cell-surface protein was generated from a small, glycosylated secretory protein. The DNA sequence encoding the entire precursor of the human chorionic gonadotropin beta (beta hCG) subunit was fused in the correct reading frame to the DNA sequence encoding the transmembrane and cytoplasmic domains of vesicular stomatitis virus glycoprotein. This chimeric gene was introduced into the vaccinia virus genome to generate a recombinant virus. The recombinant virus, when used to infect animal cells, expressed a 135-amino-acid beta hCG subunit anchored in cellular membranes by the 48 carboxy-terminal amino acids of vesicular stomatitis virus glycoprotein. The immunogenicity of this recombinant virus with respect to its ability to generate anti-hCG antibodies was compared with that of a second recombinant vaccinia virus expressing the native secretory form of beta hCG. All animals immunized with the vaccinia virus expressing beta hCG on the cell surface elicited high titers of anti-hCG antibodies. Even after a single immunization with the recombinant vaccinia virus, the anti-hCG antibody titers persisted for a long period of time (more than 6 months). None of the animals immunized with vaccinia virus expressing the native secretory form of beta hCG showed any hCG-specific antibody response.