[Cloning, Expression and Immungenicity Analysis of Antigen Eg-01883 Screened from Protoscoleces of Echinococcus granulosus].
Objective
To screen for the Echinococcus granulosus 01883（Eg-01883） specifically expressed at the protoscolex period, clone and express this molecule as well as analyse its immunogenicity.


Methods
Eg-01883, which is highly expressed at the protoscolex period but not in oncosphere， was screened by analysing the published mRNA sequences of E. granuolosus. Total RNA of E. granuolosus was extracted, Eg-01883 was cloned by RT-PCR, and the recombinant plasmid pET28a-Eg-01883 was constructed. Expression of the recombinant protein rEg-01883 was induced by isopropyl-β-D-thiogalactoside （IPTG）. ICR mice were randomized into 3 groups （n=12 in each group）. Mice in the immunization group received subcutaneous injections of 10 μg rEg-01883 in 100 μl PBS emulsified in Freund’s adjuvant at multiple sites, followed by immune enhancement after 2 weeks. Mice in the adjuvant group were injected with PBS and adjuvant. Mice in the control group received no treatment. Blood was obtained through caudal vein before immunization, and at 1, 2, and 4 weeks after the first immunization, and through the eyeball at 6 weeks after immunization. Serum levels of IgG, IFN-γ and IL-4 were determined by ELISA. The immunogenicity of rEg-01883 was identified by Western blotting.


Results
Eg-01883 was screened, cloned, expressed and purified to obtain the recombinant protein rEg-01883, which mainly existed as the inclusion body. ELISA results showed that immunization with rEg-01883 induced production of specific IgG antibody. The serum IgG level in the immunization group increased from 1 week after the first immunization, peaked at 6 weeks（2.344±0.153）, which was significantly higher than those of the adjuvant group（0.206 1±0.006） and the control group （0.241±0.01） （P<0.01）. At 6 weeks after the first immunization, the serum levels of IFN-γ （43.23 pg/ml） and IL-4（24.88 pg/ml） in the immunization group were significantly higher than those in the adjuvant group（21.77 pg/ml, 13.27 pg/ml） and the control group（17.40 pg/ml, 12.25 pg/ml）（P<0.05）. Western blot showed that the recombinant protein rEg-01883 could be recognized by His-Tag antibodies, serum of immunized mice, and serum of mice with secondary infection.


Conclusion
The recombinant protein rEg-01883 shows good immunogenicity in ICR mice.