A recombinant plasmid containing CpG motifs as a novel vaccine adjuvant for immune protection against herpes simplex virus 2

The aim of the present study was to evaluate the efficacy of a herpes simplex virus type 2 (HSV-2) DNA vaccine co-immunized with a plasmid adjuvant containing CpG motifs. A novel eukaryotic expression plasmid vector containing kanamycin resistance gene (pcDNA3Kan) was acquired from pET-28a(+) and pcDNA3 plasmids. A gene encoding full length HSV-2 glycoprotein D (gD) was amplified from the pcDNA3-gD plasmid, which was cloned into pcDNA3Kan resulting in the construction of the recombinant plasmid pcDNA3Kan-gD (pgD). A DNA segment containing 8 CpG motifs was synthesized, and cloned into pcDNA3Kan, resulting in the recombinant plasmid pcDNA3Kan-CpG (pCpG). Mice were co-inoculated with pgD (used as a DNA vaccine) and pCpG (used as an adjuvant) by bilateral intramuscular injection. Mice inoculated with pgD+pCpG showed higher titers of antibodies than those inoculated with the DNA vaccine alone (P<0.05). In addition, mice inoculated with pgD+pCpG showed the highest percentage of CD4(+) T cells in the blood of all the groups (P<0.05). Thus, the present study demonstrated that pCpG could stimulate the HSV-2 DNA vaccine to induce a stronger cell-mediated immune response than the DNA vaccine alone. The aim of the present study was to evaluate the efficacy of a HSV-2 DNA vaccine (pgD) co-immunized with a plasmid adjuvant containing CpG motifs (pCpG). Whether the pCpG would be able to stimulate the pgD to induce a stronger immune response compared with pgD alone.