Expression and characterization of the gD protein of HSV-2 fused to the tetramerization domain of the transcription factor p53

The highly immunogenic glycoprotein D (gD) of herpes simplex virus type 2 (HSV-2) is a very important element for entry of this virus into host cells. These characteristics have made this protein a very interesting HSV-2 subunit vaccine candidate. Despite efforts to prevent genital herpes using gD-based subunit vaccines, to date, clinical trials using this antigen have failed. Therefore, using a small animal model, we sought to determine if a tetramerized truncated form of gD subunit vaccine, produced by recombinant baculovirus infected insect larvae, would elicit better protection against genital herpes than a monomeric gD-2 subunit vaccine. Three out of 5 mice immunized with the tetramerized antigen produced in a baculovirus expression vector system, survived a lethal challenge with a wild type HSV-2 strain (for more than 3 weeks after challenge). In contrast, all the mice (5) immunized with the truncated protein, produced by the same methodology, died within 2 weeks after challenge. These results suggest that multimerization (increasing the structural complexity) of the truncated gD antigen might be more likely protective than the monomer form. Also the use of an alternative cost-efficient eukaryotic expression system is described.