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A vaccinia virus recombinant containing the non-structural tick-borne encephalitis virus (TBEV) NS1 gene was developed. The recombinant expressed native dimeric form of the NS1 protein in infected cells and protected mice against lethal infection with TBEV.
The oligosaccharide structures present on Asn5 of the Pichia pastoris-expressed recombinant kringle 2 domain of tissue-type plasminogen activator [(r)-[K2tPA]] have been determined by a combination of techniques, including HPLC, FPLC, gel filtration, endoglycosidase digestions and mass spectrometry. The major oligosaccharides identified after their liberation by either hydrazinolysis or by the enzyme peptide:N4-(N-acetyl-beta-glucosaminyl)asparaginyl amidase, were in the oligomer range of (mannose)8(N-acetylglucosamine)2 (Man8GN2) to Man18GN2. The preponderance of these glycans spanned Man9GN2 to Man12GN2, and the major overall product was Man10GN2. An additional (less than 5%) amount of the polypeptide was hyperglycosylated. In contrast with glycoproteins produced in Saccharomyces cerevisiae, our results with specific mannosidase digestions were consistent with previous studies showing that (alpha 1,3)-linked mannose residues were not present in extensions of the core Man8GN2 unit. The results show that the N-linked glycosylation pathways in P. pastoris are substantially different from those found in S. cerevisiae, with shorter Man(alpha 1,6) extensions to the core Man8GN2 and the apparent lack of significant Man(alpha 1,3) additions representing the major processing modality of N-linked glycans in P. pastoris.
Xylella fastidiosa is a xylem-limited, Gram-negative bacterium responsible for citrus variegated chlorosis (CVC) in sweet oranges. In the present study, we present the recombinant expression, purification and characterization of an X. fastidiosa cysteine protease (dubbed Xylellain). The recombinant Xylellain ((HIS)Xylellain) was able to hydrolyze carbobenzoxy-Phe-Arg-7-amido-4-methylcoumarin (Z-FR-MCA) and carbobenzoxy-Arg-Arg-7-amido-4-methylcoumarin (Z-RR-MCA) with similar catalytic efficiencies, suggesting that this enzyme presents substrate specificity requirements similar to cathepsin B. The immunization of mice with (HIS)Xylellain provided us with antibodies, which recognized a protein of c. 31 kDa in the X. fastidiosa pathogenic strains 9a5c, and X. fastidiosa isolated from coffee plants. However, these antibodies recognized no protein in the nonpathogenic X. fastidiosa J1a12, suggesting the absence or low expression of this protein in the strain. These findings enabled us to identify Xylellain as a putative target for combating CVC and other diseases caused by X. fastidiosa strains.
A snake venom-derived alpha-neurotoxin, alpha-bungarotoxin (alphaBgtx), is the classic competitive antagonist of nicotinic acetylcholine receptors (nAChRs). The very high specificity and essentially irreversible binding of alphaBgtx to various nAChRs make alphaBgtx the prime candidate for studying the molecular determinants of specificity for nAChR-ligand interactions. To facilitate site-directed mutagenesis of alphaBgtx for functional analysis, we have developed a recombinant expression system for alphaBgtx using the methylotropic yeast Pichia pastoris. A synthetic gene coding for alphaBgtx was subcloned into an expression vector that directs secretion of the recombinant alphaBgtx (rBgtx) when stably integrated into the yeast genome. Expression of rBgtx was induced by growth of yeast cultures with methanol as the sole carbon source. The activity of the rBgtx in the cell-free medium was measured by competition with 1251-Bgtx for binding to Torpedo nAChR-enriched membranes. The rBgtx, purified to homogeneity by standard HPLC, has the correct predicted amino terminal sequence and molecular mass. Its circular dichroism spectrum is very similar to that of authentic venom-derived alphaBgtx, and the biological activity of the rBgtx is identical to that of authentic alphaBgtx. We have used the Pichia expression system to study a double point mutation of alphaBgtx, rBgtx-K38P/L42Q, that has a high affinity for alpha3beta2 neuronal nAChRs. This is the first demonstration of engineering an alpha-neurotoxin to recognize non-alpha7 neuronal nicotinic receptors.
Toxoplasma gondii lacks the capacity to synthesize purines de novo, and adenosine kinase (AK)-mediated phosphorylation of salvaged adenosine provides the major route of purine acquisition by this parasite. T. gondii AK thus represents a promising target for rational design of antiparasitic compounds. In order to further our understanding of this therapeutically relevant enzyme, an AK cDNA from T. gondii was overexpressed in E. coli using the pBAce expression system, and the recombinant protein was purified to apparent homogeneity using conventional protein purification techniques. Kinetic analysis of TgAK revealed Km values of 1.9 microM for adenosine and 54.4 microM for ATP, with a k(cat) of 26.1 min(-1). Other naturally occurring purine nucleosides, nucleobases, and ribose did not significantly inhibit adenosine phosphorylation, but inhibition was observed using certain purine nucleoside analogs. Adenine arabinoside (AraA), 4-nitrobenzylthioinosine (NBMPR), and 7-deazaadenosine (tubercidin) were all shown to be substrates of T. gondii AK. Transgenic AK knock-out parasites were resistant to these compounds in cell culture assays, consistent with their proposed action as subversive substrates in vivo.
Intramuscular immunization with a naked DNA plasmid expressing the Plasmodium yoelii circumsporozoite protein (pPyCSP) protects mice against challenge with P. yoelii sporozoites. This protection can be improved either by coadministration of a plasmid expressing murine GM-CSF (pGMCSF) or by boosting with recombinant poxvirus expressing the PyCSP. We now report that combining these two strategies, by first mixing the priming dose of pPyCSP with pGMCSF and then boosting with recombinant virus, can substantially increase vaccine effectiveness. Not only were immune responses and protection improved but the pPyCSP dose could be lowered from 100 microg to 1 microg with little loss of immunogenicity after boost with recombinant poxvirus. Comparing mice primed by the 1-microg doses of pPyCSP plus 1 microg pGMCSF with mice primed by 1-microg doses of pPyCSP alone, the former were better protected (60% vs 0) and had higher concentrations of Abs (titers of 163, 840 vs 5, 120 by indirect fluorescent Ab test against sporozoites), more ex vivo CTL activity (25% vs 7% specific lysis), and more IFN-gamma-secreting cells by enzyme-linked immunospot assay (1460 vs 280 IFN-gamma spot-forming cells/106 cells). Priming with plasmid vaccine plus pGMCSF and boosting with recombinant poxviruses strongly improves the immunogenicity and protective efficacy of DNA vaccination and allows for significant reduction of dose.
Recent cDNA characterization has predicted the existence of a new member of the transforming growth factor family, transforming growth factor-beta 3 (TGF beta 3). However, nothing is known about the biological activities of the TGF beta 3 protein, since it has not been purified from any natural sources. We report here the recombinant expression in mammalian cells and the purification to apparent homogeneity of human TGF beta 3. The TGF beta 3 was evaluated in comparison with purified TGF beta 1 and TGF beta 2 in several assays for its effects on stimulation or inhibition of proliferation of mammalian cells. These analyses revealed that TGF beta 3 exerts activities similar to the two other TGF beta species, but that there are distinct differences in potencies between the different TGF beta forms depending on the cell type and assay used.
Histidine decarboxylase catalyses the formation of histamine, an important biological messenger. In spite of the essential biological functions exerted by histamine the knowledge about the mechanisms involved in the regulation of histidine decarboxylase is rather limited. This is most likely due to the limited supply of suitable tools, including highly specific antibodies. In the present study we describe the production and characterisation of specific antisera against rat histidine decarboxylase using recombinant protein synthesised in a bacterial expression system. The antisera were shown to effectively immunoprecipitate histidine decarboxylase activity in extracts of fetal rat liver as well as to detect the histidine decarboxylase protein by Western blot analysis of COS-7 cells expressing recombinant rat histidine decarboxylase. The results demonstrate the successful production of highly specific antisera to histidine decarboxylase which may become valuable tools in future studies of the structure and function of this enzyme.
A murine model of the cytotoxic T lymphocyte (CTL) response to glycoprotein B (gB) of human cytomegalovirus (HCMV) was developed based on the use of adenovirus (Ad) and vaccinia virus (Vac) recombinants expressing gB. Mice of different major histocompatibility haplotypes [CBA (H-2k), BALB/k (H-2k) and BALB/c (H-2d)] infected with the Ad-gB recombinant developed an Ad-specific CTL response. However, only the H-2k mice developed a significant HCMV gB-specific CTL response, as indicated by the major histocompatibility complex class I-restricted lysis of Vac strain Copenhagen (VacC)-gB recombinant-infected target cells by H-2k mouse immune spleen cells. The VacC-gB recombinant elicited only a weak gB-specific CTL response in these mice, indicating that the observed gB-specific CTL response in mice is dependent on the expression vector used for immunization. The gB-specific cytotoxicity observed in H-2k mice was mediated by the CD8 lymphocyte subset.
The ability of angiotensin II (AII) to regulate [Ca++]i in human neuroblastoma (SH-SY5Y) cells stably expressing recombinant rat AT1A receptors was investigated using microfluorimetric methods, and compared to responses obtained by stimulation of native muscarinic receptors. Applications of AII or carbachol produced biphasic rises of [Ca++]i, but in Ca++-free solutions (containing 1 mM ethylene glycol-bis (beta-aminoethyl ether)N,N,N,'N'-tetraacetic acid), both agonists produced only transient monophasic rises of [Ca++]i, and second applications were without effect. Application of Ca++(o) (2.5 mM) to cells after exposure to either agonist produced a Ni2+-sensitive rise of [Ca++]i in the absence of agonist ("capacitative Ca++ influx"). After removal of Ca++(o), both AII and carbachol elicited a second rise of [Ca++]i. Thapsigargin (1 microM) prevented these second rises of [Ca++]i. During capacitative Ca++ influx, application of AII failed to produce a further rise of [Ca++]i. In contrast, carbachol produced a further rise of [Ca++]i, attributable to activation of both nicotinic and muscarinic receptors, because it was reduced (but not abolished) by mecamylamine (1 microM) and was observed when muscarine was used as the agonist. Thus, activation of recombinant AT1A and muscarinic receptors in SH-SY5Y cells leads to mobilization of Ca++ from a common intracellular pool, and stimulates capacitative Ca++ influx. Muscarinic (but not AII) receptor occupancy is capable of stimulating an additional Ca++ influx pathway.
We have developed a method for attenuating vaccinia virus recombinants by expressing a fusion protein of a lymphokine and an immunogen. Chimeric genes were constructed that coded for gamma interferon (IFN-gamma) and structural proteins of the human immunodeficiency virus type 1 (HIV-1). In this study, we describe the biological and immunological properties of vaccinia virus recombinants expressing chimeric genes of murine or human IFN-gamma with glycoprotein gp120, gag, and a fragment of gp41. All fusion proteins retained the antigenic characteristics of both IFN-gamma and HIV as shown by immunoblot analysis. However, the antiviral activity of IFN-gamma could be demonstrated only for the IFN-gamma-gag fusion protein. In contrast, the attenuating activity of IFN-gamma for nude mice was retained by all of the recombinants, albeit at various rates. Unlike the antiviral activity, the attenuating activity of IFN-gamma was not species specific. Implications for the development of attenuated live recombinant vaccines for AIDS are discussed.
The HMG domain is a DNA binding and bending 'architectural' motif involved in chromatin re-modelling during transcription. Recombinant SRY HMG domain protein, 88 amino acids in length, has been produced in E. coli. Using FPLC and a stirred ultra-filtration cell, this domain has been purified to homogeneity and concentrated to yield milligram quantities. Functional characterisation studies of the pure, concentrated SRY HMG domain show the recombinantly expressed protein to be active in terms of DNA binding and calmodulin binding activities.
Neuroactive steroids, in particular 3 alpha-hydroxypregnanes, are allosteric modulators of the gamma-aminobutyric acidA (GABAA) receptor. Regionally selective expression of receptor subunit subtypes may account for differential responsiveness of tissues to GABAergic inhibition and neurosteroid modulatory effects. The effect of 5 alpha-pregnan-3 alpha-ol-20-one (epiallopregnanolone) on heterotropic cooperativity on the GABAA receptor complex has been studied in three subtypes of expressed recombinant human receptors and in rat brain and spinal cord. Steroid potentiation of [3H]flunitrazepam binding was greatest for the alpha 3 beta 1 gamma 2 receptor complex, whereas alpha 1 beta 1 gamma 2 and alpha 2 beta 1 gamma 2 complexes showed less than 100% enhancement in binding. Previous studies suggest that the spinal cord is devoid of alpha 1, whereas cerebellum is rich in alpha 1 subunits. Correspondingly, a differential enhancement of [3H]flunitrazepam binding in spinal cord (51%) versus cerebellum (28%) was also observed. The structure of neuroactive steroids is important in determinikng the extent of neuromodulatory activity. The 5 beta-pregnanes,5 beta-pregnan-3 alpha-ol-20-one (epipregnanolone) and 5 beta-pregnan-3 alpha,21-diol-20-one (5 beta-tetrahydrodeoxycorticosterone), were both less potent than their corresponding 5 alpha derivatives. A 3 alpha hydroxyl group is essential for neuromodulatory activity in the expressed receptors, as demonstrated by the observation that 5 alpha-pregnan-3 beta-ol-20-one (allopregnanolone) and 4-pregnen-3, 20-dione (progesterone) were both inactive.(ABSTRACT TRUNCATED AT 250 WORDS)
Heterologous expression of Pleurotus ostreatus POXC and POXA1b laccases in two yeasts, Kluyveromyces lactis and Saccharomyces cerevisiae, was performed. Both transformed hosts secreted recombinant active laccases, although K. lactis was much more effective than S. cerevisiae. rPOXA1b transformants always had higher secreted activity than rPOXC transformants did. The lower tendency of K. lactis with respect to S. cerevisiae to hyperglycosylate recombinant proteins was confirmed. Recombinant laccases from K. lactis were purified and characterised. Specific activities of native and recombinant POXA1b are similar. On the other hand, rPOXC specific activity is much lower than that of the native protein, perhaps due to incomplete or incorrect folding. Both recombinant laccase signal peptides were correctly cleaved, with rPOXA1b protein having two C-terminal amino acids removed. The availability of the established recombinant expression system provides better understanding of laccase structure-function relationships and allows the development of new oxidative catalysts through molecular evolution techniques.
Using CHO-K1 cells expressing rat thyrotropin-receptor (CHO-rTSH-R cells) or rat chorionic gonadotropin-receptor (CHO-rCG-R cells), we have examined their reactivity or cross-reactivity to recombinant human thyrotropin (TSH) or human chorionic gonadotropin (hCG). TSH stimulated cAMP formation in CHO-rTSH-R cells dose-dependently, and the maximum response was obtained at 1 mIU/ml. hCG also increased cAMP in the cells from 10(4) mIU/ml, and the maximum stimulation was observed at 10(6) mIU/ml. 10(7) mIU of hCG had the same potency with 1 mIU of TSH to rTSH-R. On the other hand, 10(-1) mIU/ml of hCG increased cAMP content in CHO-rCG-R cells and reached the maximum level at 10(2) mIU/ml. TSH also showed the stimulatory activity to CHO-rCG-R cells. It increased cAMP formation in CHO-rCG-R cells dose-dependently from 10 mIU/ml to 10(3) mIU/ml. Thirty mIU of TSH was calculated to be equivalent to 1 mIU of hCG to CG-R. These results indicate that TSH and hCG cross-react each other with rTSH-R or rCG-R.
Human astrovirus is an important cause of acute gastroenteritis. We have generated, for the first time, a vaccinia virus recombinant expressing the astrovirus 87-kDa structural polyprotein. The results demonstrate that this expression results in the formation of virus-like particles in the absence of other astrovirus proteins and genomic RNA. The purified trypsin-activated virus-like particles strongly resemble the complete astrovirus particles.
Deleted in malignant brain tumours 1 (DMBT1) codes for a approximately 340kDa glycoprotein with highly repetitive scavenger receptor cysteine-rich (SRCR) domains. DMBT1 was implicated in cancer, defence against viral and bacterial infections, and differentiation of epithelial cells. Recombinant expression and purification of DMBT1 is an essential step for systematic standardized functional research and towards the evaluation of its therapeutical potential. So far, DMBT1 is obtained from natural sources such as bronchioalveolar lavage or saliva, resulting in time consuming sample collection, low yields, and protein preparations which may substantially vary due to differential processing and genetic polymorphism, all of which impedes functional research on DMBT1. Cloning of DMBT1 cDNAs is hampered because of the size and the 13 highly homologous SRCR exons. In this study, we report on the setup of a vector system that facilitates cloning of DMBT1 variants. We demonstrate applicability of the vector system by expression of the largest DMBT1 variant in a tetracycline-inducible mammalian expression system using the Chinese hamster ovary cell line. Yields up to 30 mg rDMBT1 per litre of cell culture supernatant could be achieved with an optimized production procedure. By harnessing the specific bacteria-binding property of DMBT1 we established an affinity purification procedure which allows the isolation of more than 3 mg rDMBT1 with a purity of about 95%. Although the glycosylation moieties of rDMBT1 are different from DMBT1(SAG) isolated from saliva, we demonstrate that rDMBT1 is functionally active in aggregating Gram-positive and Gram-negative bacteria and binding to C1q and lactoferrin, which represent two known endogenous DMBT1 ligands.
A series of double-subgenomic Sindbis virus (dsSIN) recombinants that express cassettes encoding the immunogenic proteins of Japanese encephalitis virus (JEV) [prM-E, prM-E-NS1, NS1-NS2A, 80%E (encodes the amino-terminal 80% part of E), and NS1] were constructed and analyzed for their ability to confer protective immunity in mice against lethal challenge with neurovirulent JEV. The cassettes were introduced into both 5' [second subgenomic promoter of the vector precedes the SIN structural open reading frame (SP-ORF)] and 3' (the promoter follows the SP-ORF) dsSIN vectors. The longest cassette (prM-E-NS1) was 3.2 kb in length, which is remarkable for such a small vector virus as SIN (SIN genome is roughly 11.8 kb in length). The level of expression of JEV proteins appeared similar for both 5' and 3' recombinants. In general, the stability of the recombinants obtained was found to be low (expression was lost following one to five passages at low multiplicity of infection, depending on the recombinant). However, 5' recombinants containing longer cassettes (prM-E-NS1, prM-E, NS1-NS2A) were more stable than the corresponding 3' recombinants. Intraperitoneal inoculation of mice with 10(7) PFU of dsSIN-JEV recombinants induced antibodies against JEV proteins and low titers of JEV-neutralizing antibodies were produced by mice inoculated with recombinants expressing 80%E, prM-E, and prM-E-NS1. A single immunization of mice with the dsSIN-prM-E or dsSIN-prM-E-NS1 recombinants provided 40-65% protection against peripheral lethal challenge with 10(4) LD50 of neurovirulent JEV. The results demonstrate that genetically engineered togaviruses can be successfully used as vaccine vectors.