[Immunological characteristics induced in mice by nucleic acid vaccine harboring the gene encoding GAPDH in Schistosoma japonicum].

OBJECTIVE: To study the immunological characteristics induced in C57BL/6 mice by nucleic acid vaccine harboring the gene encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of Schistosoma japonicum. METHODS: The gene encoding GAPDH of S. japonicum from screening of cDNA library was amplified using universal primer T3 promoter and T7 promoter, the PCR product was cloned into the T-A vector pT-Adv. GAPDH-pT-Adv and eukaryotic expression vector pcDNA3 were digested by restriction endonucleases Hind III and Xho I, and the nucleic acid vaccine harboring the gene encoding GAPDH was then constructed by ligating the digested products. C57BL/6 mice were immunized using the purified pcDNA3-SjGAPDH. The expression of GAPDH in local muscle in mice was examined by immunofluorescence assay. The specific characteristics induced by pcDNA3-SjGAPDH were analyzed using SDS-PAGE, Western blotting, and ELISA respectively. RESULTS: Light green fluorescence was observed in local muscle cell under the fluoroscope 24 and 48 hours after immunization, which indicated the expression of GAPDH. The recombinant plasmid induced specific anti-GAPDH IgG, predominantly IgG2a, IgG2b and IgG3. Cytokines IFN-gamma, IL-2 but IL-4 were detected in C57BL/6 mice vaccinated with the vaccine. CONCLUSION: The DNA vaccine, pcDNA3-SjGAPDH induces Th1 type immune response in mice.

Conservation of epidermal growth factor receptor function in the human parasitic helminth Schistosoma mansoni.

The epidermal growth factor receptor (EGF-R) plays an important role in development and cell differentiation, and homologues of EGF-R have been identified in a broad range of vertebrate and invertebrate organisms. This work concerns the functional characterization of SER, the EGF-R-like molecule previously identified in the helminth parasite Schistosoma mansoni. Transactivation assays performed in epithelial Madin-Darby canine kidney cells co-transfected with SER and a Ras-responsive reporter vector indicated that SER was able to trigger a Ras/ERK pathway in response to human epidermal growth factor (EGF). These results were confirmed in Xenopus oocytes showing that human EGF induced meiosis reinitiation characterized by germinal vesicle breakdown in SER-expressing oocytes. Germinal vesicle breakdown induced by EGF was dependent on receptor kinase activity and shown to be associated with phosphorylation of SER and of downstream ERK proteins. (125)I-EGF binding experiments performed on SER-expressing oocytes revealed high affinity (2.9 x 10(-9) M) of the schistosome receptor for human EGF. Phosphorylation of the native SER protein present in S. mansoni membranes was also shown to occur upon binding of human EGF. These data demonstrate the ability of the SER schistosome receptor to be activated by vertebrate EGF ligands as well as to activate the classical ERK pathway downstream, indicating the conservation of EGF-R function in S. mansoni. Moreover, human EGF was shown to increase protein and DNA synthesis as well as protein phosphorylation in parasites, supporting the hypothesis that host EGF could regulate schistosome development. The possible role of SER as a receptor for host EGF peptides and its implication in host-parasite signaling and parasite development are discussed.