Adjuvant effect of granulocyte-macrophage colony-stimulating factor coding gene on cellular immunity of Japanese encephalitis virus DNA vaccine / 中华传染病杂志

ABSTRACT

Objective To study the adjuvant effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) coding gene on cellular immunity induced by Japanese encephalitis (JE) virus DNA vaccine. Methods GM-CSF coding gene was amplified by nested-reverse transcriptase-polymerase chain reaction (RT-PCR) technique from BALB/c murine spleen cells. Recombinant plasmids pJME/GM-CSF and pGM-CSF were constructed by JE virus (JEV) prM-E protein with GM-CSF coding gene or GM-CSF coding gene only, respectively. The plasmids were transfected into China hamster ovary (CHO) cells by Lipofectamine 2000. The coding protein expressions and distributions were detected by immunofluorescence. The BALB/c mice were vaccinated with indicated immunogens with or without GM-CSF gene. The changes of T lymphocyte subsets in the spleen and levels of intracellular cytokines, such as interferon (IFN)-γ and interleukin (IL)-4 of splenic cells from mice immunized with different immunogens were evaluated by flow cytometry. The cytotoxicity T lymphocyte (CTL) activity was assessed by lactate dehydrogenase (LDH). The data were compared by one-factor analysis of variance and least significant difference. Results The constructed recombinant pGM-CSF and pJME/GM-CSF were confirmed by restrict enzyme digestion and DNA sequencing. The expressions of the above proteins were mainly in the cytoplasm and minor on cell membrane. The percentage of CD4+ T lymphocytes in pJME/GM-CSF vaccinated group was (33.90±0.79)%, which was significantly higher than that of in other groups (t values were 9. 818, 6. 804, 6.594, 10.061, 9.380, and 17.675, all P<0.05). The percentages of CD4+T lymphocytes in pJME +pGM-CSF (0) and pJME+pGM-CSF (-3) vaccinated groups were (29.83±0.61)% and (29.70±0.51)%, respectively, which were both higher than that in pJME+pGM-CSF (+3) vaccinated group of (27.69+0.50)% (t=3.466, t=3.255, both P<0.05). The percentages of CD8+ T cells in pJME/GM-CSF and pJME+pGM-CSF vaccinated groups were both higher than that in empty vector (pcDNA 3.1+) group and JE inactivated vaccine vaccinated group (t values were 3.811, 2.627, 10.537, and 3.811, all P<0.05). The CTL activity in pJME/GM-CSF vaccinated group was (51.48±0.10)%, which was higher than those in other groups (t values were 22.868, 13.823, 5.377, 32.287, 34.632, and 53.795, all P<0.05). The IFN-γ/IL-4 ratios in pJME/GM-CSF, pJME+pGM-CSF (0) and pJME + pGM-CSF (-3) vaccinated groups were (19.13±1.36), (12.32±0.82) and (7.05±0.43), respectively, which were higher than those in other groups (P<0.05). Conclusion GM-CSF coding gene could enhance the cellular immune response induced by Japanese encephalitis DNA vaccine.