AEGiS-15IAC: Enhancement of immunogenicity of DNA vaccine by incorporating a 72-bp element from sv40 enhancer in the plasmid vector.

15th International AIDS Conference

Bangkok, Thailand - July 11-16, 2004

Enhancement of immunogenicity of DNA vaccine by incorporating a 72-bp element from sv40 enhancer in the plasmid vector.

Int Conf AIDS 2004 Jul 11-16; 15:(abstract no. ThOrC1343)

Shao Y, Li H, Liu Y, Tang H, Zhang R, Liu Y, Peng H, Duan D, Hong K
Division of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Beijing, China

BACKGROUND: The relatively weak immunogenicity limits the widespread application of DNA vaccine. The purpose of this study is to investigate whether a 72-bp element from SV40 enhancer has any effect on the magnitude and balance of the immune responses induced by DNA vaccine when this element is incorporated into the plasmid backbone.

METHOD: DNA vaccine vector pDRVISV1.0 was constructed by inserting the 72-bp element of SV40 enhancer in the upstream of CMV enhancer/promoter of plasmid pVRC2000 (kindly gifted by Prof. Gary Nabel in NIH). DNA vaccines carrying codon-optimized gag gene of HIV-1 CN54, a prevailing strain in many areas of China, was constructed using pVRC2000 and pDRVISV1.0, respectively. Balb/c mice were i.m. immunized with DNA vaccines pVRC2000-gag and pDRVISV1.0-gag (100mug) on days 0, 14, 28, 42. Levels of Gag-specific IgG responses and IgG1/IgG2a ratios were measured by ELISA. IFN-γ production was determined by quantitive EIA. Splenic IFN-γ-positive CD8[+] T lymphocytes stimulated by p55 peptide were evaluated by flow cytometry and ELISPOT.

RESULTS: Intensities of IgG responses induced by DNA vaccine pDRVISV1.0-gag was 2-fold higher than those induced by pVRC2000-gag. The ratio of IgG2a/ IgG1 in both groups were about 1.5. The serum IFN-γ concentrations in mice immunized with pDRVISV1.0-gag (375.6pg/ml) was significantly higher than those in mice immunized with pVRC2000-gag (174.5pg/ml) (P<0.05). Gag-specific splenic CD8+ effector cells in mice immunized with pDRVISV1.0-gag (1.48% of the total CD8+ T cells), measured by intracellular cytokine staining, was significantly higher than those observed in mice immunized with pVRC2000-gag (1.02% of the total CD8+ T cells). ELISPOT assay revealed that the mean value of Gag-specific CD8+ T cells in the spleens of mice immunized with pDRVISV1.0-gag and pVRC2000-gag was 1040 and 648.5 Spots per million splenocytes, respectively. Conclusion Gag-specific immune responses induced by DNA vaccination were enhanced by incorporation of a 72-bp element from SV40 enhancer in the plasmid vector.

Keywords: AEGIS, Vaccines, DNA, Genes, gag, Plasmids, Simian virus 40, Enhancer Elements (Genetics), HIV-1, CD8-Positive T-Lymphocytes, T-Lymphocytes, Antigens, CD8, Codon, Cytokines, Immunoglobulin G, China, Animal, Mice, immunology, genetics

040711
ThOrC1343