Efficacy of a DNA vaccine encoding the E2 glycoprotein of bovine viral diarrhea virus 1 fused to mouse lysosome-associated membrane protein 1.

The E2 protein of bovine viral diarrhea virus (BVDV) is a known protective antigen and a major target for DNA vaccines. DNA vaccines have various advantages; however, their immunogenicity needs to be enhanced by using adjuvants or drug delivery systems. In this study, we used mouse lysosome-associated membrane protein 1 (mLAMP1) as a molecular adjuvant and developed a DNA vaccine encoding an mLAMP1-BVDV E2 chimeric protein (pVax-mLAMP1-E2). We constructed DNA plasmids in which the E2 gene was inserted within the hinge region (H) or membrane proximal domain (D) of the mLAMP1 gene. Transfection of these plasmids into cultured cells led to high expression of E2 antigen from pVax-mLAMP1-E2 (H). Intradermal immunization of mice with pVax-mLAMP1-E2 (H) induced sufficient neutralizing antibodies and splenocytes with E2 antigen-specific IFN-γ production compared with pVax-mLAMP1-E2 (D). However, the immunogenicity of pVax mLAMP1-E2 (H) in mice did not differ from that of a control plasmid without the LAMP1 molecule (pVax-E2). In cattle, geometric mean serum neutralizing antibody titers after intradermal or intramuscular injection tended to be higher with pVax-mLAMP1-E2 (H) than with pVax that expressed E2 without mLAMP1. In addition, E2 antigen-specific IFN-γ production in peripheral blood mononuclear cells from cattle immunized intradermally with pVax-mLAMP1-E2 (H) was not significantly different from that of pVax-E2. These results suggest that mLAMP1 fusion antigens effectively induce humoral and cellular immunity in mice and cattle, especially when the antigen is inserted in the hinge region of mLAMP1. The LAMP1-E2 fusion antigen may be a useful candidate for a BVDV DNA vaccine in cattle.