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Results for “strain engineering”

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PubMed2006

The PLAC1-homology region of the ZP domain is sufficient for protein polymerisation.

BACKGROUND: Hundreds of extracellular proteins polymerise into filaments and matrices by using zona pellucida (ZP) domains. ZP domain proteins perform highly diverse functions, ranging from structural to receptorial, and mutations in their genes are responsible for a number of severe human diseases. Recently, PLAC1, Oosp1-3, Papillote and CG16798 proteins were identified that share sequence homology with the N-terminal half of the ZP domain (ZP-N), but not with its C-terminal half (ZP-C). The functional significance of this partial conservation is unknown. RESULTS: By exploiting a highly engineered bacterial strain, we expressed in soluble form the PLAC1-homology region of mammalian sperm receptor ZP3 as a fusion to maltose binding protein. Mass spectrometry showed that the 4 conserved Cys residues within the ZP-N moiety of the fusion protein adopt the same disulfide bond connectivity as in full-length native ZP3, indicating that it is correctly folded, and electron microscopy and biochemical analyses revealed that it assembles into filaments. CONCLUSION: These findings provide a function for PLAC1-like proteins and, by showing that ZP-N is a biologically active folding unit, prompt a re-evaluation of the architecture of the ZP domain and its polymers. Furthermore, they suggest that ZP-C might play a regulatory role in the assembly of ZP domain protein complexes.

Animals↗

PubMed2000

Cytoplasmic expression of a soluble synthetic mammalian metallothionein-alpha domain in Escherichia coli. Enhanced tolerance and accumulation of cadmium.

Bacteria are commonly used for bioremediation of heavy metal pollution and strategies to improve their performance in this respect are desirable. In this study, an Escherichia coli strain was engineered to express a common metallothionein-alpha domain. The metallothionein-alpha domain was over-expressed in the cytoplasm of E. coli as a fusion to the carboxyl terminal of maltose binding protein. The fusion protein was highly soluble in the cytoplasm of E. coli. When grown in the presence of cadmium, cells expressing the metallothionein-alpha fusion protein showed increased viability compared with control cells. Cells expressing the metallothionein-alpha also demonstrated increased accumulation of cadmium.

ATP-Binding Cassette Transporters↗

PubMed2006

Equine herpesvirus type 1 modified live virus vaccines: quo vaditis?

Infections of horses with equine herpesvirus type 1 (EHV-1) have garnered new attention over the last few years. Devastating outbreaks occurring worldwide, primarily of the neurologic form of the disease, have resulted in a reassessment of the control strategies, and particularly the prophylactic measures, that are necessary to keep the infection and spread of disease in check. Most of the available EHV-1 vaccines are based on preparations of inactivated virus, which are applied monovalently for prevention of EHV-1-caused abortion in pregnant mares or as part of multivalent vaccines to prevent respiratory disease. Despite the importance of an induction of cytotoxic immune responses for protection against EHV-1-induced disease, only two modified live virus vaccine preparations, which are both based on the avirulent EHV-1 strain RacH and were developed more than 40 years ago, are commercially available. Current efforts focus on exploiting the available infectious bacterial artificial chromosome clones of various EHV-1 strains to engineer a new generation of modified live virus vaccines. Both more efficient and long-lasting anti-EHV-1 immunity and delivery of immunogens of other pathogens are attempted and within immediate reach. The improvement of modified live virus vaccines will likely be a major focus of research in the future, and will hopefully help to more completely protect horses against one of the most important and devastating viral diseases.

Animals↗

PubMed2005

Beyond oncolytic virotherapy: replication-competent retrovirus vectors for selective and stable transduction of tumors.

As cancer gene therapy employing replication-defective vectors has met with limited clinical success, there is renewed interest in using replication-competent viruses for oncolytic virotherapy. In preclinical and clinical studies, various attenuated vaccine strains and engineered virus vectors are currently being tested for their ability to achieve tumor-selective cell killing. However, significant improvements are still required in tumor selectivity, cytolytic potency, and modulating immune responses to achieve anti-tumor effects without prematurely terminating virus spread. Recently, we have developed murine leukemia virus (MLV)-based replication-competent retrovirus (RCR) vectors for highly efficient, selective, and persistent gene transfer to cancer cells, and found that such vectors may offer significant advantages as oncolytic agents. In a variety of preclinical models, RCR vectors can achieve efficient and persistent gene delivery as the virus replicates throughout an entire tumor mass after inoculation with initial multiplicities of infection as low as 0.001. When engineered to deliver suicide genes, RCR vectors achieve highly efficient and synchronized cell killing triggered by pro-drug administration, both in culture and in tumor models in vivo. Further strategies are being explored to enhance the packaging capacity, efficiency, and specificity of this vector system through the development of semi-replicative RCR vectors, adenovirus-RCR hybrids, and incorporation of tumor targeting mechanisms via modification of binding tropism and transcriptional regulation. In addition, the ability of these vectors to achieve stable transgene expression in infected tumor cells may allow therapeutic applications that move beyond oncolysis per se.

Drug Design↗

PubMed2006

Physiological and pharmacological insights into the role of ionic channels in cardiac pacemaker activity.

The generation of cardiac pacemaker activity is a complex phenomenon which requires the coordinated activity of different membrane ionic channels, as well as intracellular signalling factors including Ca(2+) and second messengers. The precise mechanism initiating automaticity in primary pacemaker cells is still matter of debate and certain aspects of how channels cooperate in the regulation of pacemaking by the autonomic nervous system have not been entirely elucidated. Research in the physiopathology of cardiac automaticity has also gained a considerable interest in the domain of cardiovascular pharmacology, since accumulating clinical and epidemiological evidence indicate a link between an increase in heart rate and the risk of cardiac mortality and morbidity. Lowering the heart rate by specific bradycardic agents in patients with heart disease constitutes a promising way to increase cardioprotection and improve survival. Thus, the elucidation of the mechanisms underlying the generation of pacemaker activity is necessary for the development of new therapeutic molecules for controlling the heart rate. Recent work on genetically modified mouse models provided new and intriguing evidence linking the activity of ionic channels genes to the generation and regulation of pacemaking. Importantly, results obtained on genetically engineered mouse strains have demonstrated that some channels are specifically involved in the generation of cardiac automaticity and conduction, but have no functional impact on the contractile activity of the heart. In this article, we will outline the current knowledge on the role of ionic channels in cardiac pacemaker activity and suggest new potential pharmacological targets for controlling the heart rate without concomitant negative inotropism.

Animals↗

PubMed2005

IL-12 is required for induction but not maintenance of protective, memory responses to Blastomyces dermatitidis: implications for vaccine development in immune-deficient hosts.

Cellular immunity mediated by T lymphocytes, in particular CD4(+) and CD8(+) type 1 (T1) cells, is the main defense against pathogenic fungi. IL-12 initiates T1 cell development and cell-mediated immunity, but it is unclear whether IL-12 contributes to the maintenance of an antifungal T1 response. In this study, we addressed the role of IL-12 for vaccine-induced memory T cell development against experimental pulmonary blastomycosis. CD4(+) T cells absolutely required IL-12 to control a live genetically engineered attenuated strain of Blastomyces dermatitidis given s.c. as a vaccine, whereas CD8(+) T cells were significantly less dependent on IL-12. Despite differential dependency of T cell subsets on IL-12 during vaccination, neither subset acquired memory immunity in the absence of IL-12. In contrast, adoptive transfer of immune CD4 T cells from wild-type mice into IL-12(-/-) mice showed that CD4(+) T1 memory cells sustained a T1 cytokine profile and remained protective over a period of 6 mo posttransfer. Similarly, memory CD8 cells elicited in IL-12(-/-) mice with killed yeast and transient rIL-12 treatment (during vaccination) remained durable and protective after animals were rested for 3 mo. In conclusion, these studies demonstrate that once CD4 and CD8 cells have acquired a protective T1 phenotype they no longer require the presence of IL-12 to maintain antifungal protective memory.

Animals↗

PubMedDate not supplied

[Experimental evaluation of the biological safety of gene-engineered bacteria using a model strain Bacillus subtilis interferon-producing strain].

The in vitro and in vivo evaluation of the biological and ecological safety of genetically modified bacteria (GMB) was carried out on B. subtilis recombinant strain 2335/105, capable of producing human interferon alpha-2, used as experimental model. As shown in this investigation made with the use of bacteriological analysis and polymerase chain reaction, the oral administration of GMB to calves, chickens and white mice produced no disturbances in the microbial ecology of the gastrointestinal tract of warm-blooded animals and did not lead to the appearance of spontaneous transformants. The present work is the first experimental evaluation of the biological safety of genetically modified microorganisms, used as the component of Subalin, a probiotic preparation intended for use in veterinary practice.

Animals↗

PubMed2002

Enterokinase cleavage of fusion proteins for preparation of recombinant human parathyroid hormone 1-34.

An engineering E.coli strain, BL21 (DE3)/pGEX-4T hPTH (1-34), was constructed by oligonucleotide annealing and PCR amplifying the target gene, then ligating it with pGEX-4T-3 vector and transferring into BL21 host. The yield of soluble fusion protein of GST-hPTH(1-34) expressed from BL21(DE3)/pGEX-4T hPTH(1-34) is about 10 g/L after high-density, high expression culture and purification by affinity chromatography. Following the simple digestion of enterokinase, about 0.6 g/L intact hPTH (1-34) was harvested. The product is checked by HPLC MS and N-terminus sequence analysis. The purified recombinant hPTH(1-34) stimulated adenylate cyclase in rabbit renal cortical cell membranes to exactly the same extent as synthetic human parathyroid hormone standards, indicating that the recombinant product has full biological activity.

Adenylyl Cyclases↗

PubMed2002

[Construction of hpaA gene-engineered attenuated Salmonella typhimurium vaccine strain].

To express Helicobacter pylori hpaA gene in attenuated Salmonella typhimurium vaccine vehicle, and elucidate the potential value of attenuated Salmonella typhimurium as a vector expressing Helicobacter pylori antigens, by means of molecular biology, 783 bp hpaA gene was cloned into NcoI-SalI site of a procaryotic expression plasmid pTrc99A, and the recombinant plasmid was then used to transform an attenuated Salmonella typhimurium vaccine strain SL3261, and the positive clones were screened by PCR and restriction enzyme digestion. HpaA expression was analyzed by SDS-PAGE and Western blot. Two and 10 days after recombinant strain intragastric immunization, the C57BL/6 mice was sacrificed, and the spleen and terminal ileum was cultured for recombinant strain. The results showed that a recombinant procaryotic expression plasmid pTrc99A-hpaA was constructed, and the recombinant plasmid was then introduced into an attenuated Salmonella typhimurium vaccine strain SL3261 successfully. HpaA was expressed in the recombinant strains as a 30 kD protein, and also its immunogenicity was confirmed by Western blot. Recombinant strain was found in both spleen and terminal ileum of each mouse two and ten days after intragastric immunization. We concluded that a recombinant live attenuated Salmonella typhimurium vaccine strain expressing Helicobacter pylori hpaA gene was constructed and identified, and this work will help to develop oral recombinant live vaccine strains against Helicobacter pylori infection.

Amino Acid Sequence↗

PubMed1991

Epitope mapping in Salmonella flagellar protein.

The flagellar filaments of bacteria of the genus Salmonella are highly immunopotent and antigenically diverse. It is proposed to develop vaccines by replacing the flagella of live attenuated Salmonella strains with engineered flagellar filament proteins containing foreign epitopes of medical and agricultural importance. As an initial step in this process, the major linear epitope regions of one filament protein have been identified.

Amino Acid Sequence↗

PubMed2003

[Study on the preliminary purification and bioactivity of recombinant human TNF-alpha mutein 471].

AIM: To purify preliminary recombinant human TNF-alpha mutein 471 and detect its bioactivity on the basis of the TNF-alpha mutein 471 expressed in prokaryotic express system. METHODS: The expression of recombinant human TNF-alpha mutein 471 in engineering bacteria strains E.coil was induced under the condition of optimal fermentation and expression. After cultured E.coil cells were collected and broken by using an ultrasonic disintegrator, the TNF-alpha mutein 471 existed in the form of inclusion body was extracted and purified, and then the effects of denaturation and protein concentration on protein folding were examined. The bioactivities of wild type TNF-alpha and the TNF-alpha mutein 471 were detected by MTT colorimetry. RESULTS: The TNF-alpha mutein 471 was folded and polymerized successfully to from a trimer with bioactivity under the condition of proper denaturation and renaturation. The cytotoxic activity of the TNF-alpha mutein 471 to the L929 cells was 15 times as much as wild type TNF-alpha. CONCLUSION: The TNF-alpha mutein 471 expressed in prokaryotic expression system possesses significantly bioactivity after renaturation, which lays the foundation for further animal experiment and clinical experimental researches.

Animals↗

PubMed2005

[Integrative expression of XynB of Aspergillus niger UV-11 in industrial yeast].

The cDNA sequence of beta-xylanase gene (xynB) was cloned from Aspergillus niger UV-11. It was inserted into the yeast expression vector and the recombinant plasmid pAX2 was obtained. The plasmid pAX2 was introduced into an industrial S. cerevisiae 2.346 and integrated into yeast genome by co-transformation of a YEPtype plasmid pBEJ16 carrying G418 resistance. The stable engineered yeast strain XY2 was obtained. It could express and secret extracellular xylanase, and enhance the alcohol production in wheat flour fermentation compared with the host strain S. cerevisiae 2.346.

Aspergillus niger↗

PubMed2005

[Expression of the metalloproteinase domain of von Willebrand factor-cleaving protease and preparation of its McAb].

The von Willebrand factor-cleaving protease (vWF-cp) is a newly identified plasma metalloproteinase and plays an important role in the pathogenesis of thrombotic microangiopathy. In the present study, the metalloproteinase domain of vWF-cp was expressed by IPTG-induced the recombinant engineered E.coli strain harbouring pET28a (+)-vWF-cp/MD and purified using chromatography on Ni-NTA column. Then the BALB/c mice were immunized with the recombinant protein to prepare the monoclonal antibodies (McAb) against vWF-cp and the obtained McAbs were characterized. Furthermore, the expression panels of vWF-cp in human normal tissues were investigated using immunohistochemistry. The results showed that high-level expression of the recombinant protein was achieved, which existed as inclusion body and amounted to 28% of total bacteria protein. Three monoclonal antibodies against the metalloproteinase domain of vWF-cp were obtained and two of them, SZ-112 and SZ-113, were further evaluated. Both of them belong to IgG(1). The concentration of them in ascites was 4 mg/ml, and their titers were as high as 1 x 10(-5). The data of ELISA showed that SZ-112 and SZ-113 recognized different epitopes of recombinant protein. The Western blot and immunoprecipitation data showed that the two monoclonal antibodies reacted not only with the recombinant protein, but also with a 200 kD protein in platelet lysate. Moreover, the vWF-cp was found to be present in the cytoplasm of many human tissues such as liver, prostate, ovary, etc. However, the protease could not be detected in brain tissue. In conclusion, the above-mentioned research work contributed not only to the further study of the structure and function of this protease, but also to the establishment of the method for quantifying the vWF-cp antigen in plasma.

ADAM Proteins↗

PubMed1985

Purification and crystallization of the EcoRV restriction endonuclease.

The type II restriction endonuclease EcoRV purified from a genetically engineered, overproducing strain has been crystallized. Four crystal forms all obtained by precipitation with polyethylene glycol 4000 have been characterized. Two of these are suitable for high resolution structure analysis. Both are orthorhombic, have space group P2(1)2(1)2(1) and have similar unit cell dimensions of a = 58.2 A, b = 71.7 A, c = 130.6 A (form A) and a = 59.9 A, b = 74.5 A, c = 121.8 A (form B). They diffract to about 2A resolution and appear to have one dimer of 2 X 29,000 daltons in the asymmetric unit.

Crystallization↗

PubMed1997

Targeting of mucosal vaccines to Peyer's patch M cells.

Transepithelial transport of antigens and pathogens is the first step in the induction of a mucosal immune response. In the intestine, the delivery of antigens across the epithelial barrier to the underlying lymphoid tissue is accomplished by M cells, a specialized epithelial cell type that occurs only in the lymphoid follicle-associated epithelium. Selective and efficient transport of antigen by M cells is considered an essential requirement for effective mucosal vaccines. Therefore, particulate antigen formulations are currently being developed to take advantage of the capacity of M cells to endocytose particles. Based on pathogens that exploit the M cell as an invasion route into the body, live mucosal vaccines have been designed using genetically-engineered, attenuated strains of pathogens such as poliovirus and Salmonella. In an alternative approach, antigens are coupled to or encapsulated in particulate synthetic carriers. To enhance binding and uptake of such nonviable vectors, ligands are being attached which direct the vaccine particle to receptors on the M cell surface.

Adhesins, Bacterial↗

PubMed1997

Finite elasticity formulations for evaluation of ligamentous tissue.

The variety of techniques used to measure the cross-sectional area of soft connective tissues during mechanical testing lead to inconsistencies in elastic descriptions. This study compares the numerical differences between finite elasticity (Eularian and Lagrangian formulations) and infinitesimal elasticity when considering stress, strain and elastic modulus of ligamentous tissue. Our results found stress differences (Cauchy versus Kirchhoff) of 22.4%, strain differences (engineering versus Green versus Almansi) as large as 14% and elastic modulus differences (Eularian versus Lagrangian) of 44% from ligament tissue sampled from rats. It is therefore critical to maintain consistent (energy conjugate) elastic formulations for reporting mechanical evaluation of soft hydrated tissue.

Algorithms↗

PubMed1998

Development of Bacillus thuringiensis fermentation and process control from a practical perspective.

Bacillus thuringiensis (Bt) is the most widely used biopesticide producer in the biological control market. It is very critical for the Bt pesticide industry to be able to achieve a high yield in the Bt fermentation process in order to reduce its cost and compete with chemical pesticides in the market. We review the overall development of Bt fermentation process research and provide our point of view for the future research opportunities and potential improvements. This minireview covers the areas of fermentation physiology, growth dynamics and high-yield process control. It is pointed out that many studies aimed to improve spore count and process research focusing on toxin protein yield is lacking. In addition, significant development opportunities reside in the process development for the genetically engineered Bt strains expressing multiple toxin proteins.

Bacillus thuringiensis↗

PubMed1992

Comparative efficacy of three doses of the genetically engineered Aujeszky's disease virus vaccine strain 783 in pigs with maternal antibodies.

Pigs with low levels of maternally derived antibodies were vaccinated twice intramuscularly with 10(5), 10(5.5), or 10(6) plaque forming units (p.f.u.) of the genetically engineered Aujeszky's disease virus (ADV) vaccine strain 783. Strain 783 has deletions in genes encoding glycoprotein gI and thymidine kinase. All vaccinated pigs showed a high level of protection against clinical disease after challenge infection with virulent ADV. Vaccination also reduced virus excretion. The daily mean virus excretion and the mean number of days with virus excretion, fever, mild clinical signs, and growth retardation were higher in pigs vaccinated with 10(5) than in pigs vaccinated with 10(5.5) or 10(6) p.f.u. of strain 783.

Animals↗