Expression, purification and refolding of pro-MMP-2 from inclusion bodies of E. coli.

MMP-2 has been reported as the most validated target for cancer progression and deserves further investigation. However, due to the lack of methods for obtaining large amounts of highly purified and bioactive MMP-2, identifying specific substrates and developing specific inhibitors of MMP-2 remains extremely difficult. In this study, the DNA fragment coding for pro-MMP-2 was inserted into plasmid pET28a in an oriented manner, and the resulting recombinant protein was effectively expressed and led to accumulation as inclusion bodies in E. coli. This protein was easy to purify to near homogeneity by the combination of common inclusion bodies purification procedure and cold ethanol fractionation. Then, our results of gelatin zymography and fluorometric assay revealed that pro-MMP-2 at least partially restored its natural structure and enzymatic activity after renaturation. We obtained approximately 11 mg refolded pro-MMP-2 protein from 1 L LB broth, which was higher than other strategies previously reported. In conclusion, a simple and cost-effective procedure for obtaining high amounts of functional MMP-2 was developed, which would contribute to the progress of studies on the gamut of biological action of this important proteinase. Furthermore, our protocol should be appropriate for the expression, purification, and refolding of other bacterial toxic proteins.

Establishment and optimization of a high-throughput mimic perfusion model in ambr® 15.

OBJECTIVES: To establish an automated high-throughput mimic perfusion scale-down model (SDM) in ambr® 15 system. RESULTS: An optimized SDM for mimic perfusion was developed in ambr® 15 system. Cell retention in ambr® 15 was realized by sedimentation and supernatant removal with a retention rate > 95%. Although the SDM couldn't reach the viable cell density (VCD) at a bench scale bioreactor (BR), it maintained VCD at approximately 30 × 106 cells/mL with a cell bleeding rate estimated theoretically and predicted the cell specific perfusion rate (CSPR). A base-feeding strategy was developed to alleviate the pH drop during sedimentation which would adversely have an impact on cell growth, and showed an apparent cell viability improvement from 79.6% (control) to 90.1% on Day 18. The optimized SDM for mimic perfusion was employed for media screening in two cell lines. CONCLUSIONS: A small-scale high-throughput perfusion model in ambr® 15 was developed, optimized to improve cell viability, and as a result, utilized for media screening in two cell lines.

Acute enterovirus infections significantly alter host cellular DNA methylation status.

Acute infections with enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) usually cause Hand, foot and mouth disease (HFMD) among infants and young children with several large outbreaks worldwide. Unfortunately, the molecular mechanisms underlying enterovirus infections remain largely unknown. In this study, we analyzed the genome-wide DNA methylation patterns of host cells in response to EV71 and CVA16 infections using the Illumina Infinium HumanMethylation450 BeadChip. Of over 480,000 loci studied, significant differential methylation was observed between EV71 infected-cells and control cells at 3957 CpG sites, out of which 2478 were hypermethylated and 1479 were hypomethylated, whereas CVA16 infection resulted in methylation level changes of 5194 CpG sites with 4288 hypermethylated and 906 hypomethylated. These differential methylated loci displayed a wide range of genomic distributions in chromosomes, inside and surrounding areas (shores and shelves) of CpG islands, as well as functional gene regions including promoter, gene body and 3'UTR. Based on methylation alterations, 1189 genes were identified to be potentially co-associated with the replication processes of two enteroviruses. GO function annotation and enrichment analysis of 1189 common differentially methylated genes reflected a broad spectrum of biological regulatory events during viral infection. KEGG pathway analysis indicated the involvement of diverse signaling pathways including viral myocarditis, Notch signaling and antigen processing and presentation. Our present study provides a novel insight into enterovirus-host interaction network at epigenetic profile, thus contributing to improved understanding of HFMD pathogenesis.

Detection of antibodies against customized epitope: use of a coating antigen employing VEGF as fusion partner.

Diagnosis of many infectious, autoimmune diseases and cancers depends on the detection of specific antibodies against peptide epitope by enzyme-linked immunosorbent assay (ELISA). However, small peptides are difficult to be coated on the plate surfaces. In this study, we selected GnRH as a model hapten to evaluate whether VEGF121 would be suitable as an irrelevant hapten-carrier to develop a universal platform for specific antibodies detection. Firstly, GnRH was fused to the C terminus of VEGF121 and the resultant fusion protein VEGF-GnRH expressed effectively as inclusion bodies in Escherichia coli. Thereafter, VEGF-GnRH was easily purified to near homogeneity with a yield of about 235 mg from 2.1 L induced culture. At last, VEGF-GnRH was used to perform ELISA and western blot, and our results suggested that VEGF-GnRH was capable of detecting anti-GnRH antibodies in sera both qualitatively and quantitatively. Indeed, previous studies of our laboratory had demonstrated that other fusion proteins such as VEGF-Aß10, VEGF-GRP, VEGF-CETPC, and VEGF-ßhCGCTP37 were able to detect their corresponding antibodies specifically. Therefore, VEGF121 may be a suitable irrelevant fusion partner of important diagnostic peptide markers. Our works would shed some light on the development of a universal platform for detection of specific antibodies.

Protective antitumor immunity induced by tumor cell lysates conjugated with diphtheria toxin and adjuvant epitope in mouse breast tumor models.

Cancer cell vaccine-based immunotherapy has received increasing interest in many clinical trials involving patients with breast cancer. Combining with appropriate adjuvants can enhance the weak immunogenic properties of tumor cell lysates (TCL). In this study, diphtheria toxin (DT) and two tandem repeats of mycobacterial heat shock protein 70 (mHSP70) fragment 407-426 (M2) were conjugated to TCL with glutaraldehyde, and the constructed cancer cell vaccine was named DT-TCL-M2. Subcutaneous injection of DT-TCL-M2 in mice effectively elicited tumor-specific polyclonal immune responses, including humoral and cellular immune responses. High levels of antibodies against TCL were detected in the serum of immunized mice with ELISA and verified with Western blot analyses. The splenocytes from immunized mice showed potent cytotoxicity on Ehrlich ascites carcinoma cells. Moreover, the protective antitumor immunity induced by DT-TCL-M2 inhibited tumor growth in a mouse breast tumor model. DT-TCL-M2 also attenuated tumor-induced angiogenesis and slowed tumor growth in a mouse intradermal tumor model. These findings demonstrate that TCL conjugated with appropriate adjuvants induced effective antitumor immunity in vivo. Improvements in potency could further make cancer cell vaccines a useful and safe method for preventing cancer recurrence after resection.

Vaccination of non-obese diabetic mice with a fragment of peptide P277 attenuates insulin-dependent diabetes mellitus.

P277 is a peptide derived from the HSP60 regions, have potent immunological effect on insulin-dependent diabetes mellitus (IDDM) and its phase III clinical trials are currently under investigation. However, we recently discovered a positive correlation between anti-P277 autoantibodies and the presence of endothelial cells damage in inducing vascular leak syndrome. Therefore, the aim of our study was to demonstrate the critical peptide epitope of P277 to IDDM and to highlight the effects of this peptide therapy on inflammation of the islets. Groups of 4-week old female non-obese diabetic (NOD) mice were immunized one time every three weeks for three times with a residue of P277, showing a significant effect of down-regulating immunity to P277 protein and preventing the development of IDDM. Immunologic results including the suppression of T-cell proliferation, the increase of interleukin-10 (IL-10) production and reduction of interferon-γ (IFN-γ) production caused immune tolerance to P277. Hence, a functional role of the key epitope in P277 peptide capable of preventing IDDM is suggested, which could be modified to develop a novel safe and effective peptide vaccine against IDDM by reconstructing P277 in the further studies.

Immunization with a recombinant GnRH vaccine fused to heat shock protein 65 inhibits mammary tumor growth in vivo.

Gonadotrophin-releasing hormone (GnRH) is the prime decapeptide hormone in the regulation of mammalian reproduction. Active immunization against GnRH has been a good treatment option to fight against hormone-dependent disease such as breast cancer. We designed and purified a novel protein vaccine Hsp65-GnRH(6) containing heat shock protein 65 (Hsp65) and six copies of GnRH in linear alignment. Immunization with Hsp65-GnRH(6) evoked strong humoral response in female mice. The generation of specific anti-GnRH antibodies was detected by ELISA and verified by western blot. In addition, anti-GnRH antibodies effectively neutralized endogenous GnRH activity in vivo, as demonstrated by the degeneration of the ovaries and uteri in the vaccinated mice. Moreover, the growth of EMT-6 mammary tumor allografts was inhibited by anti-GnRH antibodies. Histological examinations have shown that there was increased focal necrosis in tumors. Taken together, our results showed that immunization with Hsp65-GnRH(6) elicited high titer of specific anti-GnRH antibodies and further led to atrophy of reproductive organs. The specific antibodies could inhibit the growth of EMT-6 murine mammary tumor probably via an indirect mechanism that includes the depletion of estrogen. In view of these results, the protein vaccine Hsp65-GnRH(6) appears to be a promising candidate vaccine for hormone-dependent cancer therapy.

Preparation of a peptide vaccine against GnRH by a bioprocess system based on asparaginase.

GnRH is a promising target in hormone-dependent cancer immunotherapy. In our previous study, we have designed and purified a peptide vaccine GhM (GnRH3-hinge-MVP) by use of the bioprocess system based on asparaginase. Active immunization with GhM in the presence of CFA/IFA evoked strong humoral response. In this study, the motif NRLLLTG with high affinity to nanoparticle carrier VLP HBcDelta-SBD was fused to the C terminus of GhM to form a new peptide vaccine GhMNR (GnRH3-hinge-MVP-NRLLLTG). The fusion protein ansB-C-GhMNR was controlled by vigorous T7lac promotor and expressed effectively as inclusion bodies after induction by lactose and then purified by means of cell disruption, washing and cold ethanol fractionation. After hydrolyzed for 72 h, GhMNR was liberated from the fusion partner ansB-C and purified by CM52 cation exchange chromatography. These results suggested that the bioprocess system is suitable for large-scale expression and purification of the peptide vaccine GhMNR, and even some other proteins or peptides which may be important for industrial or laboratory purposes.

A novel virus-like particle based on hepatitis B core antigen and substrate-binding domain of bacterial molecular chaperone DnaK.

Hepatitis B virus core (HBc) protein has been proved to be an attractive carrier for foreign epitopes, and can display green fluorescent protein (GFP) on its surface. The structure of substrate-binding domain of DnaK [DnaK (394-504 aa), DnaK SBD] is similar to GFP, we therefore reasoned that DnaK SBD might also be tolerated. Electron microscopic observations suggested that the chimeric proteins containing the truncated HBc (HBcDelta) and DnaK SBD could self-assemble into virus-like particle (VLP). Then the accessibility of DnaK SBD and the adjuvanticity of VLP HBcDelta-SBD were demonstrated by two recombinant peptide vaccines against gonadotropin-releasing hormone (GnRH), GhM and GhMNR. The latter carries in addition the peptide motif NRLLLTG which is known to bind to DnaK and DnaK SBD. The combination of VLP HBcDelta-SBD and GhMNR elicited stronger humoral responses and caused further testicular atrophy than the combinations of VLP HBcDelta and GhMNR or VLP HBcDelta-SBD and GhM in Balb/c mice. These findings indicate VLP HBcDelta-SBD might serve as an excellent carrier for GhMNR and some other peptide vaccines.