Immunogenicity of a recombinant chimeric antigen using Aβ1-15 epitope fused to a T helper epitope / 军事医学

Objective To explore the immunogenicity of recombinant chimeric 6Aβ15-T including the Aβ1-15 epitope and a T-helper epitope formulated with different adjuvants and to evaluate its feasibility as a candidate vaccine for Alzheimer disease (AD).Methods The recombinant chimeric antigen 6Aβ15-T formulated with Al adjuvant, Freund′s adjuvant or MF59 adjuvant was administered to two strains of mice .The 6Aβ15-T-immunized group without adjuvants ( Mock) and non-immunized group (Control) were included in this study as control groups .The specific antibody and cellular immune response of the chimeric antigen were evaluated .Results In BALB/c strain mice, three types of adjuvants could substan-tially boost the immunogenicity of chimeric antigen 6Aβ15-T and produce a high level of specific-Aβ(β-amyloid) antibod-ies.In C57BL/6 strain mice, the existence of adjuvants enhanced the immune response of 6Aβ15-T antigen, but the mice in Mock group also produced a strong antibody response .In two strains of mice, prevalence of anti-AβIgG1, which was an indicator of Th2 polarization, was observed in the 6Aβ15-T-immunized mice.Additionally, the Al adjuvant induced a high-er level of IgG1 antibody titers, and the ratio of IgG1/IgG2a was the largest.As expected, the 6Aβ15-T antigen formulated with or without adjuvants induced PADRE-specific, but not Aβ42-specific T cellular immune response .Conclusion The 6Aβ15-T antigens formulated with different types of adjuvants could induce strong Th 2-polarized Aβ42-specific antibody re-sponses without activating self-reactive Aβ42-specific T cells in two strains of mice .The results suggested that the recombi-nant chimeric antigen 6Aβ15-T is a good candidate vaccine for AD .

Influence of Japanese enciphalitis virus capsid protein on the self-replicate ability of JEV replicon vectors / 生物工程学报

To optimize a self-replicate Japanese enciphalitis virus (JEV) replicon, and to make it as an efficient vector to express the heterologous protein, we constructed three JEV replicons by PCR-based shortening the length of capsid genes. The vectors remained full or part of C gene, based on the JEV replicon pCTCJEV. Lac Z was selected as the reporter gene to verify the self-replicate ability of these DNA-based replicons. While transfected into the cell lines CME-4, which continuously expressing the JEV structure proteins C-prM-E, the JEV replicons pCMW-2M-1LACZ, pCMW-2M-3LACZ, which remained the first 23aa and 68aa of C protein, can express the reporter protein as the same level as pCMW-2M-LACZ with the full-length C protein. These results illustrated that the JEV replicon vector with 69-nt of the C gene can retain the self-replicate ability, and provide valuable tools to construct a possible vector for a long-lasting JEV RNA virus expression system.

Immunogenicity and antigenicity of Japanese encephalitis virus envelope protein domain III / 生物工程学报

To express the domain III gene of Japanese encephalitis virus (JEV) and to learn the possibility of developing the Dil protein as a subunit vaccine, we amplified the JEV DIII gene by PCR and constructed the expression plasmid pET-JE DIII by inserting JEV DIII gene into the prokaryotic expression vector pET-32a(+). The domain III protein of the attenuated strain SA14-14-2 was expressed as a thioredoxin (Trx) fusion protein, which was unique in forming a large fraction of the soluble recombinant protein. We immunized the rabbits and mice with the purified protein, tested the antigenicity and immunogenicity of JEV DIII protein by ELISA, Western blotting, plaque reduction test and observed the protective efficacy on challenged weanling mice with JEV. Rabbits immunized with the purified JEV DIII protein generated 1: 7 x 10(5) anti-JEV specific antibody titers. BALB/c mice immunized with the purified JEV E DIII protein generated 1: 8.2 x 10(4) anti-JEV specific antibody titers. And the neutralized antibody titer can reach 1:256, the survival rate of the immunized weanling mice was approximately 75%. Overall, this study highlighted that recombinant JEV E DIII protein delivered in mice and rabbits can generate high antibody titers against JEV, and protect some mice challenged with JEV. These studies can provide useful information for further developing the domain III recombinant protein as subunit vaccine against JEV.

Eukaryotic expression of P-selectin functional segment on the membrane of CHO / 生物工程学报

Cell adhesive molecular P-selectin was cloned, expressed and anchored on CHO cell membrane through GPI for selection specific antibodies. Total human platelet RNA was extracted and the functional segment of P-selectin gene was cloned by RT-PCR. The P-selectin functional segment gene was cloned into a eukaryotic expression vector pMCEw2-GPI containing an attenuated neo gene together with a downstream GPI, which was synthesized by overlapping PCR. The recombinant plasmid pMCEw2-GPI-P-selectin was then transfected to CHO(dhfr-) cells and screened with G418. ELISA, western-blot and immunofluorescence were carried out to detect the stability of P-selection expression on cell membrane. These results provided a necessary basis for the following study of selection the antibodies targeting P-selectin.

High-level Expression of Foreign Genes In vivo and In vitro by Improved DNA-Based Replicon Vector Derived From Semliki Forest Virus / 生物化学与生物物理进展

The design of DNA-based alphavirus vectors significantly improves the utility of these replicon vectors. The DNA-based replicon vectors can be used in expressing foreign genes and preparing RVP in virto efficiently, also in developing replicon vaccines and gene therapy vectors in vivo. The approach involved the conversion a RNA-based replicon vector into a layered DNA-based replicon vector by the RNA polymerase Ⅱ promoter and transcription termination/polyadenylation signal transcribed replicon RNA from DNA. When DNA-based alphavirus vector tranfected into cells, the first layer includes a eukaryotic RNA polymerase Ⅱ expression cassette that initiates transcription of RNA in nucleus. Following transport of this RNA from the nucleus to the cytoplasm, the second layer, autocatalytic amplification of the RNA vector corresponds to virus RNA replication cycle and results in high level expression of foreign gene. DNA and RNA-based bifunctional replicon expression vector pSCTA and helper vector pSHCTA were successfully constructed by replacing the SP6 promoter used in the original system pSFV1 and pSFV-helper2 derived from Semliki Forest virus (SFV) with CMV promoter and T7 promoter, and inserting BGH transcription termination and polyadenylation signal downstream 3′-untranslated region (UTR). In order to obtain DNA-based highly efficient replicon vectors, they were further modified to construct additional three DNA-based SFV replicon expression vectors and corresponding helper vectors. To investigate the efficiency of foreign gene expression level by the four different DNA-based SFV expression vectors and recombinant virus particle (RVP) prepared by cotranfecting with corresponding helper vectors, improved DNA-based replicon vectors pSCAR and pSHCAR derived from SFV were developed. high level protein could be generated using the new vector system by transfecting DNA into BHK21 cells and High titer of RVP produced by cotranfecting with helper vector. Antigen genes were also expressed in cells by the replicon expression vector. Additionally, reporter gene expression was observed in mice muscle following injection with SFV DNA vector. Anti-?-Gal antibody response and cell-mediated immune response were induced after intramuscular inoculation of the ?-Gal-encoding SFV replicon DNA. The results suggested that highly efficient DNA-based replicon vectors pSCAR and pSHCAR were constructed by modifying the SFV vectors. The improved DNA-based replicon vectors enhance the utility of them, and can be developed as potentially replicon vaccines and gene therapy vectors.

Effects of co-expression of protein folding modulators on activity of urokinase expressed in E. coli / 第三军医大学学报

Objective To study the coexpression of protein folding modulators,including chaperones(DnaK,DnaJ,and GroEL-GroES) and disulfide isomerase Dsb molecules(DsbA and DsbC) on the bioactivity of eukaryotic expressed urokinase(UK).Methods The gene sequences of DnaK,DnaJ,GroEL-GroES,DsbA and DsbC were isolated from the chromosome of E.coli by PCR.The obtained fragments mentioned above were cloned into the plasmid pBAD-1 under the control of araB promoter and then the plasmids were transformed into E.coli BW25113 and HB101 together with a compatible vector pQE-UK.The amount of expressed UK was measured by Bradford method and its activity was analyzed by fibrin plate method for its fibrinolysis.Results The activity of expressed UK was increased by co-expressing with DnaK,GroEL-GroES,DsbA,and DsbC in BW25113.Among them,the highest activity was achieved by co-expressing with GroEL-GroES.Conclusion Co-expressing of chaperones or disulfide isomerase can improve the bioactivity of UK expressed in E.coli.