Soluble expression of recomb inant cMyc,Klf4,Oct4,and Sox2 proteins in bacteria and transduction into living cells

AIM：To develop a new method to produce recombinant reprogramming proteins,c Myc,Klf4,Oct4,and Sox2,in soluble format with low cost for the generation of induced pluripotent stem cells（i PSCs）.METHODS：A short polypeptide sequence derived from the HIV trans-activator of transcription protein（TAT） and the nucleus localization signal（NLS） polypeptide were fused to the N terminus of the reprogramming proteins and they were constructed into p Cold-SUMO vector which can extremely improve the solubility of recombinant proteins.Then these vector plasmids were transformed into E.coli BL21（DE3） Chaperone competent cells for amplification.The solubility of these recombinant proteins was determined by SDS-PAGE and Coomassie brilliant blue staining.The recombinant proteins were purified by NiNTA resin and identified by Western blot.The transduction of these proteins into HEK 293 T cells were evaluated by immunofluorescence staining.RESULTS：These four reprogramming proteins could be produced in soluble format in p Cold-SUMO expression vector system with the assistance of chaperone proteins in bacteria.The proteins were purified successfully with a purity of over 70% with a relative high transduction rate into 293 cells.CONCLUSION：The results in the present study indicate the four important reprogramming proteins,c Myc,Klf4,Oct4,and Sox2,can be produced in soluble format in bacteria with low cost.Our new method thus might be expected to greatly contribute to the future study of i PSCs.

Gene Sequence, Soluble Expression and Homologous Comparison of a D-Hydantoinase fromPseudomonas putida YZ-26

A 1440bp open-reading frame encoding D-hydantoinase from Pseudomonas putida YZ-26 was cloned and sequenced（ GenBank AY387829）. The DNA fragment was inserted into Nde and BamHI sites of vector pET-3a, yielding a recombinant plasmid, pET-HDT. After being transferred into the host strain, the artificial strain, pET-HDT/ E. coli BL21 can express the D-hydantoinase as the soluble form in the Lura-Bertani medium without addition of any inducers. The activity of the enzyme toward substrate DL-hydantoin can reach 3000-4000 IU per cells from one-liter bacterial culture incubated at 30 ℃ for 10-12 h. By the comparison of amino acid sequence homology, hydrophobic residues analysis and secondary structure prediction, it was found that D-hydantoinase reported herein is quite similar to that from Pseudomonas putdia CCRC12857, and alike to that from Pseudomonas putdia DSM84 or other bacteria. A rapid and efficient purification procedure of the enzyme was performed by a three-step procedure： ammonium sulfate fractionation, phenyl Sepharose hydrophobic interaction chromatography and Sephacryl S-200 gel filtration. The molecular mass of the monomeric enzyme is 52042 Da as determined by MALDI-TOF mass spectrometry.

Soluble Expression,Purification and Characterization of Single-chain Fv Catalytic Antibody(sFv-2F3)

To find optimal conditions for expressing the soluble form of sFv-2F3 and to study the purification and property of its derivative Se-sFv-2F3,the preferred expression conditions were investigated by means of orthogonal design. These culture conditions included incubation temperature,inducer concentration, induction time and cell concentration. The evaluation of expression was accomplished by the analysis of whole cell lysates and the yield of soluble sFv-2F3 was calculated according to the analysis of Profinder(FTI-500,Pharmacia). The purification procedure was carried out via a two-step purification procedure consisting of ion-exchange chromatography,followed by immobilized metal affinity chromatography(IMAC). The antioxidant efficacy of Se-sFv-2F3 was demonstrated by the determination of the content of the main product of lipid peroxidation,MDA,the viability of cells and the activity of LDH. We obtained the preferred culture conditions to grow the engineered bacteria and the procedure for preparing soluble sFv-2F3 and confirmed the antioxidant efficacy of Se-sFv-2F3.

Efficient and Soluble Expression of N Protein of Peste Des Petits Ruminants Virus and Development of Indirect ELISA

[ Objective] The paper was to get effective soluble N protein to establish indirect ELISA method for Peste des petits ruminants （PPR）. [ Method] Soluble N protein with high expression was obtained from Escherichia coli expression system through codon optimization and optimization of expression conditions, and indirect ELISA detection method based on N protein was further established. [ Result] The assay had no cross reaction with other sheep pathogens. The intra- and inter-batch variation coefficients were less than 9%, indicating the method had good repeatability. Furthermore, totally 480 clinical serum samples were detec- ted by the assay, and the agreement rate with commercial ELISA kit （IDVET） was 98.33%. [ Conclusion] The study laid a foundation for further development of mature PPRV antibody detection kits.

Chemical Chaperones Increasing Expression Level of Soluble Single-chain Fv Antibody(scFv2F3)

Glutathione peroxidase（GPX） is a sclenoenzyme that protects the biomembrane and other cellular components against oxidative damage. The selenium-containing single chain Fv fragment of monoelonal antibody 2173 （Se scFv2F3） is a kind of GPX mimic and it has a wide clinical applications because of its high activity and low antigenicity. Se-seFv2F3 is generated by the chemical modification of the single chain Fv fragment of monoelonal antibody 2F3 （ scFv2F3 ）, which can be expressed in E. coll. In this article, the effect of chemical chaperones, such as glycerol, glucose, and β-cyclodextrin added to the culture medium, on the expression of soluble scFv2F3 was investigated. The expression level was evaluated by the determination of soluble scFv2F3 contents in the whole cell lysates. The results suggest that both glycerol and β-cyclodextrin greatly increase the expression level of soluble scFv2F3, and β-cyclodextrin is found to be more effective compared with glycerol. Glucose has a slight effect on the expression level of soluble scFv2F3. This is the first example, wherein β-cyclodextrin has been used as a chemical chaperone during the cell culture to improve the expression level of recombinant proteins. In addition, chemical chaperones are found to decrease the toxic effect of IPTG on cells.

DsbA-DsbAmut fusion chaperon improved soluble expression of human trypsinogen-1 in Escherichia coli

A co-expressing system ofDsbA-DsbAmut was suggested for the first time to enhance the soluble expression of human trypsin-1. As a control, leaderless DsbA chaperone was also co-expressed with human trypsin-1. Vectors pET39b-trypsin and pET28a-DsbA- DsbAn^ut-trypsin with the above two DsbA fusion tag were constructed. The strain with vector pET39b-trypsin expressed fusion protein DsbA-trypsin in form of inclusion bodies. While in E. coli BL21 （DE3） strain with vector pET28a-DsbA-DsbAmUt-trypsin, the soluble expression of trypsin fusion protein was achieved. Under the optimized expression conditions, the soluble fraction accounted for about 49.43% of total DsbA-DsbAmUt-trypsin proteins in crude supernatant. The purification yield was 4.15% by nickel chelating chromatography and 3.3 mg activated trypsin with a purity of 88.68% was obtained from 1 L LB broth. To detect the possible functions of DsbA series chaperons in trypsin fusion protein, we analyzed the primary three-dimensional structure of fusion proteins, mainly focusing on the compatibleness between trypsin and fusion chaperons. The results suggested that （1） besides the primary function in periplasm, leaderless DsbA or DsbAmut may also act as a signal sequences-like leader targeted to periplasm that partly relieved the pressure from fusion protein overexpression and inclusion body formation, and （2） as there was significant soluble expression of DsbA-DsbAmUt-trypsin compared with DsbA-trypsin, DsbArout may function as charge or hydrophobic balance in recombinant protein DsbA-DsbAmut- trypsin.

Establishment of Double-antigen Sandwich Time-resolved Fluorescence Immunoassay for Detection of Pest des Petits Ruminants Virus

[Objectives]This study was conducted to explore rapid and large-scale screening and detection of peste des petits ruminants(PPR),so as to provide important technical means for prevention,control and purification of PPR.[Methods]Soluble N protein and NH fusion protein were successfully obtained in an Escherichia coli expression system by optimizing E.coli codon and expression conditions.Furthermore,based on purified soluble N protein and NH fusion protein,a double-antigen sandwich time-resolved fluorescence immunoassay method for detection of peste des petits ruminants virus(PPRV)was established.[Results]The method has high sensitivity and specificity and can specifically detect the antibody against PPRV in sheep serum,and it has no cross reaction with other related diseases.The method was used to detect 292 clinical samples,and compared with French IDVET competition ELISA kit.The coincidence rates of positive samples and negative samples from the two kinds of test kits were 92.47%and 97.26%,respectively,and the overall coincidence rate was 94.86%.The intra-group and inter-group coefficients of variation in the repeatability test were less than 10%.[Conclusions]Compared with the traditional ELISA method,the double-antigen sandwich time-resolved fluorescence immunoassay for detection of PPRV has equivalent sensitivity and specificity,and simple and rapid operation,and thus high application and popularization value.

sTREM-1 as promising prognostic biomarker for acute-on-chronic liver failure and mortality in patients with acute decompensation of cirrhosis

BACKGROUND Acute decompensation(AD)of cirrhosis is associated with high short-term mortality,mainly due to the development of acute-on-chronic liver failure(ACLF).Thus,there is a need for biomarkers for early and accurate identification of AD patients with high risk of development of ACLF and mortality.Soluble triggering receptor expressed on myeloid cells-1(sTREM-1)is released from activated innate immune cells and correlated with various inflammatory processes.AIM To explore the prognostic value of sTREM-1 in patients with AD of cirrhosis.METHODS A multicenter prospective cohort of 442 patients with cirrhosis hospitalized for AD was divided into a study cohort(n=309)and validation cohort(n=133).Demographic and clinical data were collected,and serum sTREM-1 was measured at admission.All enrolled patients were followed-up for at least 1 year.RESULTS In patients with AD and cirrhosis,serum sTREM-1 was an independent prognosis predictor for 1-year survival and correlated with liver,coagulation,cerebral and kidney failure.A new prognostic model of AD(P-AD)incorporating sTREM-1,blood urea nitrogen(BUN),total bilirubin(TBil),international normalized ratio(INR)and hepatic encephalopathy grades was established and performed better than the model for end-stage liver disease(MELD),MELD-sodium(MELD-Na),chronic liver failure-consortium(CLIF-C)ACLF and CLIF-C AD scores.Additionally,sTREM-1 was increased in ACLF and predicted the development of ACLF during first 28-d follow-up.The ACLF risk score incorporating serum sTREM-1,BUN,INR,TBil and aspartate aminotransferase levels was established and significantly superior to MELD,MELD-Na,CLIF-C ACLF,CLIF-C AD and P-AD in predicting risk of ACLF development.CONCLUSION Serum sTREM-1 is a promising prognostic biomarker for ACLF development and mortality in patients with AD of cirrhosis.

Primary Purification of Co-expressed Soluble and Insoluble Alpha-interferon 2b from Recombinant E. coli

Alpha-interferon 2b (IFN 2b) was produced both in soluble and insoluble forms from recombinant E. coli. The dissolution of the expressed IFN 2b in inclusion body was carried out and it was found that the optimal condition to dissolve the expressed protein was 7 mol稬1guanidinium salt solution at pH 3.0. The resultant solution was diluted 20 times using pH 6.0 buffer to refold the protein correctly. The cation exchange column was employed to purify both refolded and soluble IFN 2b. For soluble IFN sample, high IFN 2b recovery yield (92.1%) with 91.7% purity was obtained in the eluate. However, for refolded IFN sample, only 72.7% of IFN 2b was recovered with relatively low purity (56.8%) by cation exchange chromatography. Although the expression level of insoluble IFN was higher than that of co-expressed soluble IFN in this recombinant E. coli cells, the productivity of bioactive IFN 2b was higher with soluble expressed IFN after primary purification process. Soluble expression of foreign proteins in recombinant bacteria might be an alternative strategy for efficient production of heterogeneous pro-teins due to high bioactivity and simple downstream protein purification process.

Expression,purification and identification of LBD domain of human PPARδ in E.coli

Peroxisome proliferator-activated receptors （PPARs） are ligand-activated transcription factors known to play a pivotal role in regulations of metabolism. In order to yield soluble ligand binding domain of PPARδ （PPARδLBD） for screening ligands, the cDNA was amplified using total RNA from HepG2 cells by RT-PCR. Then the enzyme-digested product was inserted . downstream of the malE gene in the vectorpMAL-p2x, which encoded maltose-binding protein （MBP）, resulting in the expression of an MBP-PPARδLBD fusion protein. The recombinant plasmid was transformed into E. coli TBI that was cultured shakily at 30 ℃, 200 r/min and induced by 0.4 mmol/L IPTG for 6 h. The cells were harvested by centrifugation and broken by sonication. The expressed fusion protein was soluble and accounted for 0.31 of the total protein in the supernatant. Western blot analysis showed that the expressed MBP-PPARδLBD could bind to anti-MBP-antibody. The MBP-PPARδLBD fusion protein of 77 kDa and the PPARδLBD protein of 34 kDa were obtained by amylose-resin affinity chromatography without or with digestion of Factor Xa. They were both homogeneity, judged by SDS-PAGE. The recombinant MBP-PPARδLBD and PPARδLBD protein with high purity is obtained, which provides the necessary material for screening and researching PPARδ ligands.

Modification in Media Composition to Obtain Secretory Production of STxB-based Vaccines using Escherichia coli

Shiga toxin B-subunit （STxB） from Shigella dysenteriae targets in vivo antigen to cancer cells, dendritic cells （DC） and B cells, which preferentially express the globotriaosylceramide （Gb3） receptor. This pivotal role has encouraged scientists to investigate fusing STxB with other clinical antigens. Due to the challenges of obtaining a functional soluble form of the recombinant STxB, such as formation of inclusion bodies during protein expression, scientists tend to combine STxB with vaccine candidates rather than using their genetically fused forms. In this work, we fused HPV16 E7 as a vaccine candidate to the recombinantly-produced STxB. To minimize the formation of inclusion bodies, we investigated a number of conditions during the expression procedure. Then various strategies were used in order to obtain high yield of soluble recombinant protein from E. coli which included the use of different host strains, reduction of cultivation temperature, as well as using different concentrations of IPTG and different additives （Glycin, Triton X-100, ZnC12）. Our study demonstrated the importance of optimizing incubation parameters for recombinant protein expression in E. coli; also showed that the secretion production can be achieved over the course of a few hours when using additives such as glycine and Triton X-100. Interestingly, it was shown that when the culture mediums were supplemented by additives, there was an inverse ratio between time of induction （TOI） and the level of secreted protein at lower temperatures. This study determines the optimal conditions for high yield soluble E7-STxB expression and subsequently facilitates reaching a functionally soluble form of STxB-based vaccines, which can be considered as a potent vaccine candidate for cervical cancer.

Soluble triggering receptor expressed on myeloid cell-1 （sTREM- 1）： a potential biomarker for the diagnosis of infectious diseases

Sensitive and useful biomarkers for the diagnosis and prognosis of infectious diseases have been widely developed. An example of these biomarkers is triggering receptor expressed on myeloid cell-1 （TREM-1）, which is a cell surface receptor expressed on monocytes/macrophages and neutrophils. TREM-1 amplifies inflammation by activating the TREM-1/DAP12 pathway. This pathway is triggered by the interaction of TREM-1 with ligands or stimulation by bacterial lipopolysaccharide. Consequently, pro-inflammatory cytokines and chemokines are secreted. Soluble TREM-1 （sTREM-1） is a special form of TREM-1 that can be directly tested in human body fluids and well-known biomarker for infectious diseases, sTREM-1 level can be potentially used for the early diagnosis and prognosis prediction of some infectious diseases, including infectious pleural effusion, lung infections, sepsis, bacterial meningitis, viral infections （e.g., Crimean Congo hemorrhagic fever and dengue fever）, fungal infections （e.g., Aspergillus infection）, and burn-related infections, sTREM-1 is a more sensitive and specific biomarker than traditional indices, such as C-reactive protein and procalcitonin levels, for these infectious diseases. Therefore, sTREM-1 is a feasible biomarker for the targeted therapy and rapid and early diagnosis of infectious diseases.

Soluble Triggering Receptor Expressed on Myeloid Cells-1 and Inflammatory Markers in Colorectal Cancer Surgery： A Prospective Cohort Study

Background： Major abdominal surgery, including colorectal cancer （CRC） surgery, leads to systemic inflammatory response syndrome that can be detected and monitored with inflammatory markers testing. The aims of the study were to evaluate the usefulness of soluble triggering receptor expressed on myeloid cells-l （sTREM-1 ）, interleukin-6 （IL-6）, procalcitonin （PCT）, and C-reactive protein （CRP） in following the inflammatory response in CRC surgery and postoperative period, as well as to determine if duration of the surgery and the time that the colon has been opened during the surgery （open colon time [OCT]） refect a larger surgical stress through inflammatory markers rise. Methods： The study included 20 patients who underwent CRC surgery and 19 healthy volunteers from June 2011 to September 2012. We determined inflammatory markers 1 day before surgery （T0）, 24 h （T1）, 48 h （T2）, and 7 days after the surgery （T3）. All statistical analyses were calculated using MedCalc Statistical Software version 14.8.1 （MedCalc Software bvba, Ostend, Belgium）. Results： Concentrations ofCRP, PCT, and I L-6 in all measurement times were statistically different and sTREM- 1 did not yield statistical significance. A weak positive correlation was/bund between l L-6 in T 1 and T2 with the duration of the surgery （T 1 ： r= 0.4060, P 〈 0.0001 ; T2：r =0.3430, P〈0.0001）andOCT（T1：r= 0.3640, P〈0.0001,T2：r=0.3430, P〈0.0001）.AweakpositivecorrelationbetweenCRP in T2 and OCT （r = 0.4210, P 〈 0.0001 ） was also found. The interconnectivity of tested parameters showed a weak positive correlation between CRP and IL-6 in T1 （r= 0.3680; P 〈 0.0001 ）, moderate positive correlation in T2 （r = 0.6770; P 〈 0.0001）, and a strong positive correlation in T3 （r = 0.8651; P 〈 0.0001）. Conclusions： CRP, IL-6, and PCT were shown to be reliable for postoperative monitoring. Simultaneous determination of CRP and IL-6 might not be useful as they follow similar kinetics, sTREM- 1 might not be useful in CRC postoperative monitoring.