Construction of DNA vaccine with Neisseria gonorrhoeae porin B fused with B subunit of Escherichia coli heat-labile enterotoxin and study on its immune responses in mouse / 中华传染病杂志

ABSTRACT

Objective To investigate the specific humoral immune response and cellular immune response induced by DNA vaccine with Neisseria gonorrhoeae porin B (PorB) fused with B subunit of Escherichia coli heat-labile enterotoxin B (LTB) in mice. Methods Target genes of porB, ltB and ltB-porB were amplified by polymerase chain reaction (PCR) and cloned into eukaryotic vector pcDNA3.1(-). The recombinants were identified by PCR, enzyme digestion and DNA sequencing.The vectors were transfected into Hela cells, and expressed proteins were checked by cytoimmunofluorescence. Female BALB/c mice were intranasally immunized with recombination vectors. The humoral immune response and cellular immune response were detected by enzyme linked immunosorbent assay (ELISA) and methyl thiazolyl tetrazolium (MTT) colorimetric assay. The expressions of recombination vectors in intranasal mucosal tissues of the immunized mice were detected by immunohistochemistry. The means between groups were compared by analysis of variance. Results All the three recombinants were expressed in Hela cells and intranasal mucosal tissues. The PorB specific IgG in serum and sIgA in vaginal secretions in DNA vaccine immunized mice were significantly higher than those in controls (P＜0.01 ; P＜0.05). Moreover, the sIgA level in pcDNA3.1 (-)/ltB-porB group was higher than that in peDNA3, 1(-)/porB group (P＝0. 002). The levels of interferon-gamma (IFN-γ) and interleukin-4 (IL-4) in the supernatants and stimulation index (SI) of spleen lymphocyte culture in pcDNA3, 1(-)/porB group were (170.04±23.89) pg/mL, (114.68±14.27) pg/mL and 1. 68±0.19, respectively; and those in pcDNA3, 1(-)/ltB-porB group were (161.42±27.50) pg/mL, (124.16±19.04) pg/mL and 1.73±0.28, respectively; which were both higher than those in pcDNA3.1(-)/ phosphate buffered saliae (PBS) group (P＜0. 01; P＜0.05) and pcDNA3.1 (-)/ltB group (all P＜0.05), while there was no significant difference between pcDNA3.1 (-)/ltB-porB group and pcDNA3. 1 (-)/porB group (0. 998, 0. 696, 0. 994; all P＞0.05). Conclusions The constructed DNA vaccines are all successfully expressed in Hela cells and murine intranasal mucosal tissues. The mucosal immunization of the vaccines [pcDNA3. 1 (- )/porB and pcDNA3.1 ( -)/ltBporB] could induce humoral immune response and cellular immune response, especially mucosal immune response. It is confirmed that mucosal adjuvant LTB could promote PorB to induce higher level of mucosal immune response in mice.