Dynamic observation of splenocyte apoptosis in mice immunized with recombinant vaccine Bifidobacterium bifidum pGEX-Sj14-3-3 of Schistosoma japonicum

Abstract

Objective To investigate the effects of recombinant vaccine Bifidobacterium bifidum (Bb) pGEX-Sj14-3-3 on splenocyte apoptosis in BALB/c mice.Methods Ninety-six BALB/c mice were randomly divided into two groups according to their body mass:per os group (PO) and intranasal immunization group (IN),with 48 mice in each group.All mice were orally and intranasally immunized with recombinant vaccine Bb(pGEX-Sj14-3-3).Four mice in each group were sacrificed on weeks 0,2,4,6,8,10,12,14,16,18,20 and 22,respectively,after immunization,and splenocytes were separated and cultured with or without ConA stimulation.The apoptotic rates of splenocytes were detected by flow cytometry.Results It showed that apoptotic level of splenocytes in both groups remarkably increased after 2-4 weeks without ConA stimulation (PO:0.069 ± 0.005,0.076 ± 0.010; IN:0.037 ± 0.002,0.075 ± 0.002),and the value reached the peak on the 4th week,and the differences were statistically significant compared with that of week 0(all P ＜ 0.05).Apoptotic level of splenocytes in both groups with ConA stimulation increased after 2-6 weeks(PO:0.089± 0.006,0.098 ± 0.010,0.060±0.007; IN:0.054 ± 0.001,0.093 ± 0.003,0.058 ± 0.012),and the value also reached the peak after 4 week,respectively.The differences were statistically significant compared with that of week 0 (all P ＜ 0.05).Apoptotic level of splenocytes in each group with ConA stimulation was significantly higher than that without ConA stimulation.Conclusion It is suspected that the recombinant vaccine Bb(pGEX-Sj14-3-3) may inhibit apoptosis of splenocytes in mice immunized orally or intranasally. Key words: Schistosoma japonicum; Bifidobacterium bifidum; Vaccines; Apoptosis; Plasmids