关键词: 日本血吸虫, 密码子优化, 免疫保护

Abstract: Objective To study the protective effect of codon optimized TPI DNA vaccine against Schistosoma japonicum infection. Methods Sixty female BALB/c mice were randomly divided into 5 groups. The mice were injected through musculus quadriceps fexoris with 100 μg pcDNA 3.1 control（Group A），pcDNA3.1-TPI（Group B），pcDNA 3.1-TPI-mHSP70（Group C），pcDNA3.1-TPI.opt（Group D），and pcDNA3.1-TPI.opt-mHSP70（Group E）respectively. All mice were immunized for three times with an interval of two weeks. The mice were challenged with（40±1） cercariae of S. japonicum per mouse by abdominal skin penetration 4 weeks after the last immunization，and sacrificed at 42 days post-challenge，the number of worms or hepatic eggs was counted. Blood was taken for the detection of IgG，IgG₁，and IgG_2a 2 days before immunization and before challenge，respectively. Spleen cells of 2 mice from each group were cultured and stimulated with ConA and rSjCTPI peptide，and the supernatant was collected for detection of IL-2，IL-4，IL-5，IFN-γ，and TNF by flow cytometry. Results ELISA showed that the mice in groups B，C，D，and E produced specific IgG and IgG₁，IgG_2a antibody isotypes，and the ratio of IgG_2a/IgG₁ was 1.73，2.06，2.44，and 3.09，respectively. The levels of IL-2，IFN-γ and TNF in groups D and E were higher than that of groups B and C. The worm reduction rate and hepatic egg reduction rate in groups D（36.03%，41.7%） and E（39.03%，46.85%）were higher than those of groups B（26.28%，28.35%） and C（28.38%，31.39%）（P＜0.01）. Conclusions The codon optimized TPI DNA vaccine induces higher level of protective effect and Th1-biased cellular immune response than those of non-optimized TPI DNA vaccine.

Key words: Schistosoma japonicum, Codon optimization, Protective immunity