Interleukin-12 gene adjuvant increases the immunogenicity of virus-like particles of human papillomavirus type 16 regional variant strain

OBJECTIVES: To analyze the immunogenicity of virus-like particles (VLP) of human papillomavirus type 16 (HPV16) isolated in East China and the adjuvant potential of interleukin-12 (IL-12). METHODS: The variant HPV16 L1VLP expressed in sf9 insect cells were purified with cesium chloride gradient centrifugation. BALB/c mice were vaccinated with VLP (L1N), VLP with Freund's adjuvant (L1A) or VLP with IL-12 recombinant plasmid (L1P). HPV16 VLP specific IgG and IFN-γ level in the serum were detected by ELISA, and the percentage of CD4(+) and CD8(+) in spleen cells was detected with flow cytometry. RESULTS: The titers of serum IgG antibodies in vaccinated groups were higher than in negative control and the serum antibodies mainly recognized conformation-dependent HPV16 VLP epitopes. Splenic CD4(+) and CD8(+) T cell subsets increased after vaccination in every experimental group, and CD8(+) increased obviously in L1P group. The ratio of CD4(+)/CD8(+) decreased in L1P group and increased in the other two groups, compared to control group. Vaccination induced specific secretion of IFN-γ in the serum of vaccinated group (p < 0.05), especially in the L1P group. CONCLUSIONS: VLP of HPV16 variant strain isolated in East China could induce humoral immunity and cellular immunity in mice, and IL-12 recombinant plasmid can enhance cellular immunity.