A DNA vaccine containing inverted terminal repeats from adeno-associated virus increases immunity to HIV.

Background: DNA vaccines have been used to induce both humoral and cellular immune responses against infectious microorganisms. This study explores whether DNA vaccine immunogenicity can be improved by introducing inverted terminal repeats (ITRs) from adeno-associated virus (AAV) into the regulatory region of the DNA plasmid.

Methods: CMV promoter-driven HIV Env expressing plasmid (pCMV-HIV) and the pCMV-HIV plasmid introduced ITRs (pITR/CMV-HIV) were transfected in HEK293 cells with LipofectAmine. The HIV Env expression was quantified with Western blot. Fifty micro g of pCMV-HIV or pITR/CMV-HIV plasmid with RIBI adjuvant were immunized to BALB/c mice on days 0, 14 and 28 by intramuscular route, and HIV-specific serum IgG titer was detected 2, 6, 10, 14 and 18 weeks after the first immunization. HIV-specific tetramer assay and HIV-specific IFN-gamma ELIspot assay were performed 1 week after the last immunization. The immune mice were intravenously challenged with a vaccinia virus expressing the HIV env gene 1 week after the last immunization.

Results: Significantly higher level of HIV Env expression was achieved by pITR/CMV-HIV plasmid. BALB/c mice immunized with pITR/CMV-HIV plasmid generated significantly higher HIV-specific antibody, higher cellular immune responses and lower viral loading than animals immunized with pCMV-HIV plasmid.

Conclusions: AAV ITRs enhance CMV-dependent up-regulation of transgene expression and immunogenicity of DNA vaccine.