[Effect of epitope-based peptide-DNA dual vaccines against Schistosoma japonicum in mice].

A C-T-B PDDV mixture of the three constructed epitope-based peptide-DNA dual vaccines (PDDV) containing the CTL (C), Th (T) and B-cell (B) epitopes from Sj22.6 tegument (C-PDDV, T-PDDV and B-PDDV) with a 1:1:1 ratio was prepared. Thirty-six mice were randomly divided into six groups averagely named as 18K group, PBS group, C-PDDV group, T-PDDV group, B-PDDV group, and C-T-B PDDV group. All the mice received three immunizations at 2-week intervals with the same dose of antigen (10 microg DNA+28 microg peptide). One week after the last immunization, the mice were sacrificed, the spleens were removed and splenocytes were collected. Splenocyte proliferation was assayed by[3H] TdR incorporation after stimulation with soluble worm antigen (SWA). Levels of IFN-gamma and IL-4 in the splenocyte culture supernatants were determined by ELISA. The results showed that IFN-gamma content in T-PDDV group [(76.0 +/- 11.2) pg/ml] was higher than that of PBS [(13.0 +/- 2.1) pg/ml] and 18K control groups [(14.0 +/- 3.2) pg/ml] (P<0.01). IL-4 level in T-PDDV [(152.0 +/- 21.1) pg/ml] and C-T-B mixture groups [(86.0 +/- 12.2) pg/ml] was higher than others (P<0.01 and P<0.05). The splenocytes from T-PDDV group showed a significant increase in proliferation compared with PBS and 18K control groups after stimulation by SWA (P<0.01). However, there was no significant difference in splenocyte proliferation among C-T-B, PBS and 18K control groups (P>0.05). These findings indicate that T-PDDV and C-T-B PDDV mixture induces stronger immune response than that of C-PDDV or B-PDDV.