A novel tetrameric gp350^1-470 as a potential Epstein-Barr virus vaccine

Infectious mononucleosis and B-cell transformation in response to infection with Epstein-Barr virus (EBV) is dependent upon binding of the EBV envelope glycoprotein gp350 to CD21 on B-cells. Gp350-specific antibody comprises most of the EBV neutralizing activity in the serum of infected patients, making this protein a promising target antigen for a prophylactic EBV vaccine. We describe a novel, tetrameric gp350-based vaccine that exhibits markedly enhanced immunogenicity relative to its monomeric counterpart. Plasmid DNA was constructed for synthesis, within transfected CHO cells, of a tetrameric, truncated (a.a. 1-470) gp350 protein (gp350^1-470). Tetrameric gp350^1-470 induced ~20-fold higher serum titers of gp350^1-470-specific IgG and >19-fold enhancements in neutralizing titers at the highest dose, and was >25-fold more immunogenic on a per-weight basis than monomeric gp350^1-470. Further, epidermal immunization with plasmid DNA encoding gp350^1-470 tetramer induced 8-fold higher serum titers of gp350^1-470-specific IgG relative to monomer. Tetrameric gp350^1-470 binding to human CD21 was >24-fold more efficient on a per-weight basis than monomer, but neither tetramer nor monomer mediated polyclonal human B-cell activation. Finally, the introduction of strong, universal tetanus toxoid (TT)-specific CD4+ T-cell epitopes into the tetrameric gp350^1-470 had no effect on the gp350^1-470-specific IgG response in naïve mice, and resulted in suppressed gp350^1-470-specific IgG responses in TT-primed mice. Collectively, these data suggest that tetrameric gp350^1-470 is a potentially promising candidate for testing as a prophylactic EBV vaccine, and that protein multimerization, using the approach described herein, is likely to be clinically relevant for enhancing the immunogenicity of other proteins of vaccine interest.