Design, expression, and characterization of a novel dendritic cell-targeted proteins.

In vivo approaches to inducing an effective immune response focus on targeted antigen (Ag) delivery to dendritic cells (DCs). In this study, we developed a new method of targeting plasmid DNA and/or the antigen (Ag)-antibody (Ab) complex to DCs via the DC receptor DEC-205, also known as cluster of differentiation CD205. We cloned and expressed a recombinant protein composed of mouse DEC-205-specific single-chain fragment variable region (mDEC-205-scFv), the streptococcal protein G (SPG) IgG-binding domain and cationic peptide (CP), which named mDEC205-scFv-SPG-CP (msSC). In vitro, the recombinant protein msSC can specifically bind to DCs through the section of mDEC-205-scFv, and bound the Ag-Ab complex via SPG as well as plasmid DNA through electrostatic bonding with CP in vitro. In addition, msSC functioned in a manner similar to anti-DEC-205 monoclonal Ab and bound to mouse bone marrow-derived DCs. It was demonstrated in vivo that msSC can target plasmid DNA to DCs, resulting in efficient uptake and expression. Moreover, msSC can form a complex with pGL3-CMV and transport it to draining lymph nodes when injected in vivo. These results indicate that msSC can be used as a carrier protein for vaccine delivery to DCs via formation of plasmid DNA-Ag-Ab ternary complexes.

Increasing plasmid-based DNA vaccine construct (16 kb pSVK-HBVA) production in Escherichia coli XL10-Gold through optimization of media component.

At present, there are production processes to produce protein by Escherichia coli (E. coli) fermentation. Research on the design and optimization of the plasmid fermentation medium, however, is less advanced. The fermentation medium that is optimized for plasmid DNA production is different from the medium that is optimized for protein production. So, establishing a scientific and rational method to optimize the fermentation medium used for plasmid production is very important. Previously, our laboratory developed a novel therapeutic DNA vaccine (named pSVK-HBVA) for hepatitis B based on the alphavirus replicon, and found that E. coli XL10-Gold was the optimal host strain for the production of plasmid pSVK-HBVA. The aim of this study was to establish a scientific and rational method to optimize the fermentation medium used for plasmid production, and investigate the effect of growth medium composition on the production of plasmid pSVK-HBVA harboured in E. coli XL10-Gold, as well as to optimize the medium composition. The one-factor-at-a-time experiments demonstrated that Luria-Bertani (LB) was the optimal basic medium. The optimal carbon source and nitrogen source were glycerol and home-made proteose peptone, respectively. Based on the Plackett-Burman (PB) design, proteose peptone, glycerol and NH4Cl were identified as the significant variables, which were further optimized by the steepest ascent (descent) method and central composite design. Growth medium optimization in 500-mL shake flasks by response surface methodology resulted in a maximum volumetric yield of 13.61 mg/L, which was approximately 2.5 times higher than that obtained from the basic medium (LB).

[Preliminary observation on antitumor effect of HPV58 composite DNA vaccine].

OBJECTIVE: To initially observe the antitumor immune of PVAX1-HPV58mE6E7FcGB composite DNA vaccine. METHODS: Before detecting immune effect of the vaccine, the B16-HPV58E6E7 tumor cell line was built which could steadily express HPV58E6E7 fusion gene. Then, HPV58E6E7-GST fusion protein as an antigen was expressed and purified. Before or after immunized with the vaccine, the C57BL/6 mice were challenged by B16-HPV58E6E7 cells. Anti-tumor transplantation and tumor growth inhibition experiment were performed to observe prevention and treatment effects on the vaccine. Specific humoral and cellular immune responses in the immunized mice were detected by ELISA, enzyme linked immunospot assay (ELISPOT) and cytotoxic T lymphocyte (CTL) method. RESULTS: In the anti-tumor transplantation experiment, tumor formation rate was only 9/15 in the mice which were immunized by PVAX1-HPV58mE6E7FcGB vaccine, time before tumor formation was the longest [(13.6 ± 1.7) days] and tumor growth was the slowest in the vaccine group. In tumor growth inhibition experiment, inhibition rate reached 81.4% in the vaccine group. Except tumor formation rate, all data in the vaccine group was superior to the pure antigen PVAX1-HPV58mE6E7Fc group (P < 0.05). Humoral immune effect showed that both the vaccine and the pure antigen could induce specific antibody in the immunized mice, and the highest titer were 1: 25 600 and 1: 12 800, respectively. Although there was not significant difference of antibody titer between the vaccine and the pure antigen group (P > 0.05), the number of activated T cells in the vaccine group was almost four times as that in the pure antigen group [(219 ± 34)/4×10(5) spleen lymphocytes versus (55 ± 25)/4×10(5) spleen lymphocytes, P < 0.05], and the highest specific CTL that vaccine induced was significantly higher than that of pure antigen (43.3% versus 31.3%, P < 0.05). CONCLUSIONS: Humoral and cellular immune response could be effectively stimulated by PVAX1-HPV58mE6E7FcGB composite DNA vaccine. Growth of B16-HPV58E6E7 cells was significantly inhibited in the immunized mice. The cellular immune effect on the vaccine was superior to the pure antigen. Therefore, PVAX1-HPV58mE6E7FcGB could be used as a candidate vaccine for immune therapy to the HPV58 positive tumors and precancerous lesions.

[Transformation activity and antigenicity of the human papillomavirus type 58 E6E7 fusion gene mutant].

OBJECTIVE: To develop a prophylactic and therapeutic vaccine against human papillomavirus (HPV) type 58-associated cervical carcinoma, and explore its transformation activity and antigenicity. METHODS: The E6 and E7 three amino acid codons in the HPV 58 virus were modified respectively and fused. The modified and fused gene was named HPV58 mE6E7. The recombinant HPV58 mE6E7 gene was inserted into pIRES-neo vector to generate plasmid pIRES-neo-HPV58 mE6E7. Then NIH/3T3 cell line was transfected with plasmid pIRES-neo-HPV58 mE6E7. The pIRES-neo-HPV58 mE6E7-transfected cells were the experimental group, pIRES-neo-HPV58 E6E7-transfected cells were the positive control group, and pIRES-neo empty vector-transfected cells were the negative control group. The expression of HPV58 mE6E7 protein in the experimental cells was detected by flow cytometry, immunofluorescence and Western blot. The transformation activity of HPV58 mE6E7 was tested by soft agar colony formation assay and subcutaneously tumors in nude mice. Finally, DNA vaccine was constructed with HPV58 mE6E7 fusion antigen and used to immunize C57BL/6 mice with the vaccine plasmids. The specific serum antibodies were detected by EIISA, and the number of splenic specific CD8(+) T cells secreting IFN-γ of the immunized mice was detected by ELISPOT assay. RESULTS: Sequencing confirmed the expected mutation and a 100% homogeneity of the HPV58 E6E7 fusion gene. Stable transfected NIH/3T3 cells expressing HPV58 mE6E7 and HPV58 E6E7 gene were 70.3% and 84.1%, respectively. The relative expressions of HPV58 mE6E7 and HPV58 E6E7 fusion protein in 3T3-HPV58 mE6E7 experimental cells and 3T3-HPV58 E6E7 positive control cells were 2.1 ± 1.7 and 3.8 ± 1.4, respectively, and were negative in the negative control group. No colony formation was found in the experimental and 3T3-neo negative control cell groups, and 31 colonies were found in the positive control cell group, among them 10 colonies were consisted of more than 50 cells. No tumor mass was formed within 4 weeks in the nude mice of experimental and negative control groups, but among the 10 mice of positive control group tumor was formed in 6 mice. Using HPV58 mE6E7 fusion gene as target antigen of DNA vaccine, the antibody titer was 25 600, and specific immunity spots were 218.8 ± 34.4, significantly higher than that in the control group. CONCLUSIONS: The fused and modified HPV58 E6E7 amino acid codons can abolish the transformation activity but preserve its antigenicity. HPV58 mE6E7 is a potential target gene for the development of therapeutic DNA vaccine against HPV58-associated cervical cancer.

[Construction and expression of the efficient recombinant plasmid pEE14.1-IFN-α expressing human IFN-α].

AIM: To construct the eukaryotic expression plasmid pEE14.1-IFN-α expressing human IFN-α gene, and to detect the expression of the plasmid in eukaryotic cells. METHODS: The human IFN-α gene amplified by PCR and was linked into pCI-GPI, then inserted into the eukaryotic expression vector pEE14.1. The recombinant plasmid was transfected into the 293T cells, the IFN-α expression was detected by ELISA and Western blotting. RESULTS: Enzyme digestion and sequence analysis showed that the bicistronic eukaryotic expression vector pEE14.1-IFN-α was constructed successfully. The expression of plasmid was detected by ELISA, and the production of IFN-α in supernatant of transfected cells was about 3.15 ng/mL. Also, Western blotting could reveal the characteristic band of IFN-α gene. CONCLUSION: The vector is constructed successfully, which provide a new selection for HBV immunotherapy.

Intraarticular gene delivery of CTLA4-FasL suppresses experimental arthritis.

T lymphocytes are key inflammatory cells contributing significantly to the pathogenesis of Rheumatoid arthritis (RA). Biological treatments targeting T lymphocytes may provide an efficient approach for treatment of RA. CTLA4-FasL, a fusion product of extracellular domains of CTLA4 and FasL, integrating two inhibitory elements against T cells into one molecule, might be a desirable derivative of engineered soluble FasL or CTLA4 and have therapeutic potential in RA. The aim of this study was to investigate whether simultaneous induction of Fas-mediated apoptosis and blockade of co-stimulation signal by CTLA4-FasL gene delivery has a suppressive effect on adjuvant-induced arthritis (AIA) in Lewis rats. Recombinant adeno-associated virus (rAAV) vectors encoding rat CTLA4-FasL fusion gene (rAAV.CTLA4-FasL) or enhanced green fluorescent protein (rAAV.EGFP) were injected intraarticularly into both ankle joints after immunization. The ankles were monitored by measures of clinical, histological and inflammatory cytokines' changes. Treatment using rAAV.CTLA4-FasL resulted in a significant suppression of AIA compared with rAAV.EGFP control, as reflected in the mainly clinical signs including articular index, ankle joint thickness and paw swelling and typically histological characters of arthritic joints including synovial hyperplasia, inflammatory cells infiltration and cartilage degradation. Treatment with rAAV.CTLA4-FasL also significantly decreased the levels of key proinflammatory cytokines in AIA joints. Moreover, local productions of transgene mRNA and protein of CTLA4-FasL were found in injected joints without systemic distribution. Our results indicate that rAAV.CTLA4-FasL profoundly suppressed experimental model of RA, implicating the potential therapeutic applications for suppression of RA by local joint delivery of CTLA4-FasL.

[A study on the construction, expression and immunosterility of Lagurus laguru zona pellucida 3 DNA vaccine pVAX1-sig-LTB-lZP3-C3d3].

AIM: To enhance the immunocontraceptive effect of Lagurus lagurus zona pellucida 3 DNA vaccine, and to achieve the prospect of application through the pVAX1-sig-LTB-lZP3-C3d3 different immunity pathway. METHODS: Two adjuvant molecules were constructed into the recombinant plasmid pVAX1-sig-LTB-lZP3-C3d3 as DNA vaccine which contains Escherichia coli heat-labile enterotoxin B subunit and the molecular adjuvant 3 copies of C3d. The results of RT-PCR and western blot showed that the DNA vaccine was expressed in mRNA and protein level. The female C57BL/6 mice were immunized by three ways: intramuscular injection, intranasal or oral route.Antibody levels and types were detected by ELISA. RESULTS: ELISA results showed that recombinant plasmid pVAX1-sig-LTB-lZP3-C3d3 immunization induced specific IgG, IgA levels were significantly different comparing with control (P<0.01). Antifertility experiment showed that the experimental group reduced the average fertility significantly different compared with the control group (P<0.01). CONCLUSION: Restriction analysis, RT-PCR and Western blot showed that the recombinant plasmid constructed correctly and can be the expression of mRNA and protein levels.It resulted that the recombinant plasmid pVAX1-sig-LTB-lZP3-C3d3 can induce the specific immune response efficiently and enhance the immunocontraceptive effects.

[Construction of a replicative anti-tumor DNA vaccine PSCK-2PFcGB and its expression in vivo and in vitro].

OBJECTIVE: To construct a replicative anti-tumor DNA vaccine PSCK-2PFcGB based on Semliki Forest Virus (SFV) replicon vector and observe its expression in vivo and in vitro. METHODS: The plasmid pVAX1-2PFcGB was digested with Nhe I, and the digestion product was blunted prior to further digestion with BssH II to obtain the fragment 2PFcGB, a fusion gene containing the multitarget complex antigen 2PAG encoding both the most cytotoxic T lymphocyte epitopes of human survivin and chorionic gonadotropin ß chain-CTP37 of human and monkey. The 2PFcGB fragment was inserted into the PSCK vector digested by Sma I. The products with the expected size were extracted and ligated, and the positive clones were screened by kanamycin and amplified. The recombinant PSCK-2PFcGB, following identification by colony PCR and restriction endonuclease Nde I, was transfected into 293T cells via lipofectamine 2000 and its expression was detected. The recombinant plasmid was also transfected into mouse quadriceps femoris muscle to observe its expression in vivo by immunohistochemistry. RESULTS: Nde I digestion resulted in a fragment of the expected size. Transfection with the recombinant plasmid PSCK-2PFcGB resulted in successful expression of the antigen and adjuvant molecular protein in 293T cells, with the positivity rates of 5.70% and 19.75%, respectively. The fusion tumor antigen survivin and hCGß-CTP37 were also detected in the muscular tissues of the mice. CONCLUSION: A novel replicative anti-tumor DNA vaccine PSCK-2PFcGB has been successfully constructed and can be expressed in 293T cells and in the muscular tissues of immunized mice, which provide a basis for further studies of the antitumor activity and immunological mechanism of the DNA vaccine.

[Construction of eukaryotic expression vector of human hCGbeta and establishment of stably transfected B16 cell line].

AIM: To construct the eukaryotic expression vector of human hCGbeta and stably transfect B16 cell line with it. METHODS: The full length of hCGbeta cDNA fragment was amplified by PCR and inserted into eukaryotic expression vector pIRES-neo, added the restriction enzyme position and 6xHis tag. After identification of restriction digestion and PCR, The recombinant plasmid pIRES-neo-hCGbeta-(His)6; was obtained. Then transfected it into B16 cells by lipofectamine 2000. After screening culture by G418, a stably transfected cell line was established, the transcription and expression of the hCGbeta gene was identified by RT-PCR, Western blot and immunofluorescence assay. RESULTS: The eukaryotic expression vector pIRES-neo-hCGbeta-(His)6; was successfully constructed. A stably transfected cell line was established and the expression rate of hCGbeta gene was higher than 90%. CONCLUSION: The established cell line can highly express hCGbeta stably, the expression of the target gene provide a solid experimental foundation for further studies on the function of the hCGbeta, and which will contribute to the research of hCGbeta gene in the tumor immunotherapy.

Association between the frequency of class II HLA antigens and the susceptibility to intrauterine infection of hepatitis B virus.

Multiple factors determine the susceptibility to intrauterine hepatitis B virus (HBV) infection. These factors include the HBV structure, HBV mutation, HBV DNA level, placental barrier, the immune status of the mother, and the genetic make-ups of the newborn infants. Since HLA system is an integral component of the immune response, we hypothesized that the highly polymorphic HLA genes are the key determinants of intrauterine HBV infection. In this study, we selected newborn infants of HBsAg-positive mothers, and divided the infants into 2 groups: intrauterine infection group and non-intrauterine infection group according to the status whether or not they were infected at birth. Each infected infant was compared with 2 controls from the same birth cohort. HLA-DR allele typing was performed using a PCR-sequence specific primer (PCR-SSP) for 24 subjects with intrauterine infection and 48 controls without infection. We found that, among the fifteen (15) HLA-DR alleles assessed, HLA-DRB1*07 was the one, and the only one, significantly in excess (OR = 6.66, P = 0.004) in the intrauterine infection group compared to the non-intrauterine infection group. Our findings thus suggest that high frequency of HLA class II molecules, e.g. HLA-DRB1*07, is associated with the susceptibility of the infants to intrauterine HBV infection.

[Construction of GPI-CTLA4Ig chimeric molecule and its expression on CHO-dhfr(-) cells].

AIM: To develop a novel immunosuppressant GPI-CTLAIg modified by glycosyl-phosphatidylinositol(GPI). METHODS: GPI-modified CTLAIg was produced by linking-up of CTLA4Ig with GPI-modification signal sequences from decay-accelerating factor (DAF). Chimeric molecule GPI-CTLA4Ig gene was cloned into eukaryotic expression vector pCI-dhfr. Using lipofectine-mediated gene transfer technique, pCI-GPI-CTLA4Ig was transfected into CHO-dhfr(-) cells, and the transfectants were screened by methotrexate (MTX). Expression of the recombinant protein was assessed by RT-PCR, ELISA, cell immunofluorescence staining and Western blot, and the purification of expressed protein was performed by protein A affinity chromatography. RESULTS: The chimeric molecule GPI-CTLA4Ig has been constructed and stablely expressed on CHO-dhfr(-) cells. CONCLUSION: GPI-modified CTLAIg will may be used as novel immunosuppressant for suppressing reaction in graft rejection.

[Development of an anti-rTNF-alpha chimeric antibody].

AIM: To develop an human-mouse chimeric antibody against rTNF-alpha. METHODS: Expression vector of human-mouse chimeric antibody CZ12 gene was constructed by using VL and VH genes of mAb Z12 with neutralizing activity, and then COS7 cells were transfected. Supernatant containing CZ12 was detected by RT-PCR, ELISA, Western blot and in-vitro neutralization assay, respectively. RESULTS: The RT-PCR analysis showed that there was the transcription of human-mouse chimeric antibody mRNA in the transfected COS7 cells. ELISA and Western blot detection showed that the CZ12 could recognize specifically TNF-alpha. The in-vitro neutralization assay proved that CZ12 could neutralize the cytoxicity of TNF-alpha to L929 cells. CONCLUSION: human-mouse chimeric antibody CZ12 with neutralizing activity was successfully expressed in eukaryotic cells.