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Objective:To construct the recombinant DNA E.coli ghosts (EBGs) expressing Treponema pallidum adhesin Tp0751 (pcD/Tp0751-BG) and determine its immunocompetence in immunized mice,and provide a potential novel method for syphilis vaccine developing.Methods:The recombinant eukaryotic expression plasmid pcDNA3.1(+)/Tp0751 was constructed and loaded into empty EBGs to create pcD/Tp0751-BG.The loading rate was determined accordingly.Macrophages cell line RAW264.7 was transfected with pcD/Tp0751-BG,and the expression of recombinant Tp0751(rTp0751) protein was detected by Western blot(WB).For immuno-competence in mice,the female BALB/c mice were randomly divided into 6 groups,including three control groups,A (PBS),B (EBG),C (empty pcDNA),and experimental group D(naked pcD/Tp0751),E (pcD/Tp0751-BG) and F (pcD/Tp0751-BG+rTp0751).All the mice were immunized as indicated for three times by intramuscular injection at two weeks intervals.The levels of specific IgG in sera and SIgA in genital tract lavage fluid were measured by ELISA.Levels of lymphocyte proliferation and IFN-γ secretion in spleen cells were measured by CCK-8 Cell Counting Kit and ELISA as well,respectively.Results:The loading rate of pcD/Tp0751 to EBGs was 76.1%.WB showed that the target recombinant protein pcD/Tp0751 expressed in RAW264.7 cells was active with Tp-infected rabbit sera.The titers of specific IgG and SIgA in group D,E,F gradually increased to significantly higher level as compared to the control groups (P<0. 01),which reached its peak at wk 8 after last immunization(the titers of IgG and SIgA were 1 :102 400 and 1 :12 800 in group F,respectively). Higher levels of specific IgG and SIgA were observed in groups E and F as compared to group D after first boost (P<0. 01),with groups F higher than group E after last boost(P<0. 01). At wk 8 after the last boost,the stimulation index (SI) and levels of IFN-γ in group D,E,F were all significant higher than the control groups (P<0. 01), with group E and F higher than group D (P<0. 01),and group E higher than group F (P<0. 05). Conclusion: The recombinant DNA EBGs of T. pallidum adhesin Tp0751 (pcD/ Tp0751-BG) possesses the immunocompetence to induce not only strong mucosal and systemic humoral immune response but also systemic cellular immune response in BALB/ c mice. The heterologous boost can be more efficient than homologous boost during immunization process.
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Objective To trace changes in the transcript level of the Treponema pallidum(Tp)protein Tp0751 in skin lesions of a rabbit model of early syphilis. Methods Three New Zealand white rabbits were intracutaneously injected with 0.1 ml of Tp (Nichols Seattle strains)suspensions (107 treponemes/ml)at 10 sites on the shaved back to establish a model of early syphilis. All the rabbits received a single injection with the total amount of treponemes being 107. Then, skin changes at injection sites were observed, and the size of skin rashes was recorded on a daily basis. Skin specimens sized 0.4 cm × 0.4 cm were excised from an injection site and a non-injection site(negative control)separately every 3 days for the detection of Tp0751 and Tp0574 mRNAs. The whole experiment lasted 30 days, and a total of 11 skin biopsies were carried out. Fluorescence-based quantitative PCR was performed to measure the mRNA expressions of Tp0751 and Tp0574 continuously and dynamically during the development of chancre. Results After intracutaneous injection of Tp suspensions, red papules occurred on the back of rabbits on day 6, and reached maximum size on day 19 with the formation of ulcer and chancre. On day 25, disseminated secondary syphilides gradually appeared all over the body surface of the rabbits. The mRNA expression levels of Tp0574 and Tp0751 increased at the early stage, peaked onday 15 (compared with the other time points, all P < 0.05), thereafter rapidly declined, but rose slightly on day 27. The standardized expression level of Tp0751 mRNA increased gradually after day 15, and peaked on day 24 (compared with the other time points, all P < 0.05). Conclusion The transcript level of Tp0751 was high in rabbits at the late stage of Tp clearance when generalized disseminated secondary syphilides had not appeared, suggesting that Tp0751 may be involved in the systemic spread of Tp.
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Objective To express Tp0751 laminin-binding adhesion of Treponema pallidum (T. pallidum) ,and assess the immunocompetence. Methods The Tp0751 ORF without upstream non-cod-ing region was ligated into the expression vector pET-28a( + ), and expressed in E. coli R2566. Its immuno-gen was analyzed by Western blot and ELISA. Results A fusion protein with molecular weight about 26×103 was attained after expression and purification. Western blot proved that the recombinant protein can specifically react with T. palliclum IgG positive sera. Specific humoral response were elicited after introducing recombinant protein in Zealand rabbit and the specific antibody titer was above 1:10 2400 detected by indi-rect ELISA. Conclusion The expressed recombinant protein showed excellent immunoeompetence, and the results lay the foundation for the research on its function to T. paUidum infection.
