[The effects of inoculation route and adjuvant type on the immunizing potency of CVB3 VP1 protein]

To explore the effects of inoculation route and adjuvant type on the immunizing potency of coxsackievrus B type 3 (CVB3) VP1 protein.

The recombinant plasmid pET-His/VP1 expressed CVB3 VP1 was transformed into E.coli BL21(DE3) pLysS and induced to express VP1 protein by IPTG, and verified by Western blot analysis. The fusion VP1 protein was purified with Ni affinity chromatography. Firstly, BALB/c mice were administered via different inoculation route(subcutaneous, intraperitoneal, intramuscular), with twelves mice in each group. Secondly, combined with various adjuvants (Alum, Freund's adjuvant, Montanide ISA720), with eighteen mice in each group. The mice were immunized three times at a three week interval with 50 μg of VP1 protein. The titers of sera IgG and neutralizing antibody were detected by ELISA and neutralization assay. Cell mediated immune response was tested by the lymphocytes proliferation activity and specific CTL cytotoxic activity. The mice were challenged with lethal dose of CVB3, the titers of the sera virus were titrated. Furthermore, the survival rates of mice were observed.

The VP1 protein was expressed in E.coli successfully and the fusion protein was purified. In different inoculation route, the titers of neutralizing antibody and specific IgG in intramuscular injection group was much higer than other groups (P<0.01). VP1 protein in combination with Montanide ISA720 and Freund's adjuvant elicit higher titer antibodies and cell mediated immune response, and the virus titers in blood were lower in comparison to Alum adjuvant group (P<0.05).The survival rate of Freund' adjuvant group was better than adjuvant AL(OH)(3); group (P<0.05).

The VP1 protein combined with ISA720 and Freund's adjuvant given by intramuscular injection may induce an improved immune responses and the better survival rates of the mice after virus challenge.