Jul 15, 2003 - thank Andrew Gelman, Ronald Harty, and Phillip Scott for careful ... Fulton, R. W., A. W. Confer, L. J. Burge, L. J. Perino, J. M. d'Offay, M. E..
Fusion to C3d Enhances the Immunogenicity of the E2 Glycoprotein of Type 2 Bovine Viral Diarrhea Virus Lingshu Wang, J. Oriol Sunyer, and Leonard J. Bello* Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 Received 15 July 2003/Accepted 21 October 2003
The use of DNA and protein subunit vaccines in animals provides an opportunity to introduce vaccines that are arguably the safest that can be developed. For that reason, considerable effort is under way to devise methods of enhancing the immunogenicity of such vaccines. Seven years ago it was shown that fusing complement fragment C3d to hen egg lysozyme (HEL) enhanced the immunogenicity of HEL 10,000-fold. Based on this observation, we decided to evaluate the effect of C3d on the immunogenicity of the E2 protein of bovine viral diarrhea virus (BVDV). E2 is the major target of neutralizing antibody during BVDV infection. To test the effect of C3d on E2 immunogenicity, expression cassettes encoding a secreted form of E2 alone (E2s) or E2 fused to three copies of murine C3d (E2s-C3d) were constructed. The proteins were purified from the supernatants of transfected cells and used to immunize mice. The immune response was monitored by an enzyme-linked immunosorbent assay (ELISA) for E2s-specific antibody and by a virus neutralization test. The ELISA results indicated that the E2s-C3d protein is 10,000-fold more immunogenic than the E2s protein alone. The maximum primary immune response was elicited with
