Enhancing immune responses against HIV-1 DNA vaccine by coinoculating IL-6 expression vector.

DNA vaccines have a demonstrated ability to induce humoral and cellular immune responses in animal models and humans. To analyze the immunogenicity of HIV-1 DNA vaccine which expressing the chimeric gene gag-gp120 of Chinese prevalent HIV-1 strain and the immunoregulatory activity of IL-6, DNA vaccine plasmid pVAX1-gag-gp120 and eukaryotic expression plasmid pVAX1-IL6 were constructed and the expression in vitro was detected by RT-PCR and Western blotting, the results showed that the gene of interest expressed in the transfected HeLa cells. To explore the immune response in mice coinoculated with HIV-1 DNA vaccine and IL-6 expression plasmid, BALB/c mice were injected i.m. with eukaryotic expression plasmid pVAX1-IL6 and DNA vaccine plasmid pVAX1-gag-gp120. The specific humoral and cellular immunity in mice could be induced by inoculating separately HIV-1 DNA vaccine plasmid or coinoculating with IL-6 expression plasmid, and the specific killing activities of spleen CTL and the level of serum antibodies in the coinoculation group were significantly higher than those in the separate inoculation group. These results strongly support the use of IL-6 as a cytokine adjuvant in DNA vaccination.