12 results on '"Vellekamp, Gary"'
Search Results
2. Investigations of PEGylated Recombinant Adenovirus, Using Fluorescein-Labeled Polyethylene Glycol
- Author
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Vellekamp Gary J, Seoju Lee, and Sundari Ravindran
- Subjects
Gel electrophoresis ,Chromatography ,Virion ,Polyethylene glycol ,Adenoviridae ,Polyethylene Glycols ,law.invention ,chemistry.chemical_compound ,Spectrometry, Fluorescence ,chemistry ,Biochemistry ,law ,In vivo ,PEG ratio ,Genetics ,PEGylation ,Recombinant DNA ,Molecular Medicine ,Fluorescein ,Propionates ,Ultracentrifugation ,Molecular Biology ,Linker ,Chromatography, High Pressure Liquid - Abstract
As with certain successful protein drug treatments, the attachment of polyethylene glycol (PEG) molecules to recombinant adenovirus (rAd) can augment their therapeutic potential. Unlike these proteins, the rAd particle has thousands of target sites for PEG conjugation. The reliable measurement of the average number of PEG molecules attached to the virion, or the degree of PEGylation (DP), is crucial not only for the characterization of PEGylated virus but also for optimization of the PEGylation reaction. Using a fluorescein-labeled PEG-SPA linker (SPA, succinimidyl ester of PEG propionic acid) with a 5-kDa linear PEG moiety, multiple preparations of fluoro-PEG-rAds were produced under various reaction conditions, purified, and analyzed by size-exclusion high-performance liquid chromatography (HPLC) with fluorescence quantification of the virus peak. The DP was strongly dependent on the percent linker concentration in the reaction. For example, under one set of conditions, fluoro-PEG-rAd samples prepared at 1.3, 2.5, 5.0, 7.4, and 10.0% linker concentration had DPs of approximately 540, 1,000, 1,590, 1,990, and 2,170, respectively. The fluoro-PEG-rAds were compared with a set of nonfluorescent PEG-rAds. Analytical ultracentrifugation in CsCl density gradients showed distinct peaks at decreased buoyant density corresponding to the increased DP of the rAd samples; sodium dodecyl sulfate-polyacrylamide gel electrophoresis/scanning densitometry showed decreased hexon monomer and penton base. Both techniques were used to estimate the DP of nonfluorescent PEG-rAds versus fluoro-PEG-rAds, and anion-exchange HPLC revealed the different surface chemistries of the two vector types. In summary, these studies should provide investigators with the ability to reproducibly prepare and characterize PEGylated rAds or other large viral or nonviral particles for further in vivo studies.
- Published
- 2007
3. Characterization of Hemodynamic Events Following Intravascular Infusion of Recombinant Adenovirus Reveals Possible Solutions for Mitigating Cardiovascular Responses
- Author
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Beth Hutchins, Vellekamp Gary J, Suganto Sutjipto, Todd Machemer, Heidrun Engler, Drake LaFace, Elena Brin, Susan Cannon-Carlson, Douglas Cornell, Mark Horn, Marcio Voloch, Thomas Schluep, Van Tsai, Nico van Rooijen, Dan Maneval, Shu Fen Wen, Seoju Lee, and Sundari Ravindran
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Bradycardia ,Cardiac output ,Kupffer Cells ,Genetic Vectors ,Hemodynamics ,Blood Pressure ,Tachyphylaxis ,Pharmacology ,medicine.disease_cause ,Cardiovascular System ,Adenoviridae ,Electrocardiography ,Mice ,Therapeutic index ,Heart Rate ,Carcinoma, Non-Small-Cell Lung ,Drug Discovery ,Heart rate ,Genetics ,Animals ,Humans ,Medicine ,Cardiac Output ,Molecular Biology ,Mice, Inbred BALB C ,business.industry ,Genetic Therapy ,Hypothermia ,beta-Galactosidase ,Influenza A virus ,Immunology ,Molecular Medicine ,medicine.symptom ,business - Abstract
Intravascular administration of recombinant adenovirus (rAd) in cancer patients has been well tolerated. However, dose-limiting hemodynamic responses associated with suppression of cardiac output have been observed at doses of 7.5 x 10(13) particles. While analysis of hemodynamic responses induced by small-molecule pharmaceuticals is well established, little is known about the cardiovascular effects of rAd. Telemetric cardiovascular (CV) monitoring in mice was utilized to measure hemodynamic events following intravascular rAd administration. Electrocardiogram analysis revealed a block in the SA node 3-4 min postinfusion, resulting in secondary pacemaking initiated at the AV node. This was associated with acute bradycardia, reduced blood pressure, and hypothermia followed by gradual recovery. Adenovirus-primed murine sera with high neutralizing antibody (nAb) titers could inhibit CV responses, whereas human sera with equivalent nAb titers induced by natural infection were, surprisingly, not inhibitory. Interestingly, repeat dosing within 2-4 h of the primary injection resulted in desensitization, resembling tachyphylaxis, for subsequent CV responses. Last, depletion of Kupffer cells prior to rAd infusion precluded induction of CV responses. These inhibitory effects suggest that rAd interactions with certain cells of the reticular endothelial system are associated with induction of CV responses. Significantly, these studies may provide insight into management of acute adverse effects following rAd systemic delivery, enabling a broadening of therapeutic index.
- Published
- 2005
4. Proteomic study of recombinant adenovirus 5 encoding human p53 by matrix-assisted laser desorption/ionization mass spectrometry in combination with database search
- Author
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Guodong Chen, Barbara Twarowska, Tattanahali L. Nagabhushan, Vellekamp Gary J, Shihong Wang, Birendra N. Pramanik, John T. Tang, Urooj A. Mirza, Wylie David C, Fred W. Porter, and Yan-Hui Liu
- Subjects
Chromatography ,Molecular mass ,Chemistry ,viruses ,Computational biology ,Condensed Matter Physics ,Mass spectrometry ,law.invention ,Matrix-assisted laser desorption/ionization ,law ,Proteome ,Recombinant DNA ,Database search engine ,Physical and Theoretical Chemistry ,Protein precursor ,Instrumentation ,Polyacrylamide gel electrophoresis ,Spectroscopy - Abstract
The clinical application of recombinant adenoviruses as vectors for gene therapy brings about the need to develop new analytical methodologies for monitoring the quality of the viral production as well as establishing structure–function relationships. A mass spectrometry-based assay has been developed for the characterization of structural proteins of the recombinant adenovirus type 5 vector encoding human p53 tumor suppressor gene. The fingerprinting of the viral proteome was accomplished by integration of MALDI-MS and/or MALDI-PSD-MS with SDS–PAGE and RP-HPLC, followed by database search using MS-Fit and MS-Tag algorithms. Viral proteins (molecular weights ∼10,000–100,000 Da) corresponding to more than 95% of total protein mass were resolved and identified, which include hexon (II), penton base (III), peripentonal hexon-associated protein (IIIa), minor core protein (V), major core protein (VII), and other hexon-associated proteins (VI and VIII). An important finding of our studies was the identification of some precursor proteins (i.e., pVIII) and propeptides of precursor proteins (pVIII, pX, and pVI) present in the adenovirus sample. The information obtained allows direct and accurate assessment of the quality of recombinant adenoviruses.
- Published
- 2003
5. Quantification of empty capsids in preparations of conditionally replicating adenovirus
- Author
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Ravindran, Sundari, Yang, Xiaoyu, Sutjipto, Suganto, Liu, YanHui, and Vellekamp, Gary
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Pharmacology ,Drug Discovery ,Genetics ,Molecular Medicine ,Molecular Biology - Published
- 2004
- Full Text
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6. Empty capsids in column-purified recombinant adenovirus preparations
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Larry Bondoc, Vellekamp Gary J, Marcio Voloch, Suganto Sutjipto, Susan Cannon-Carlson, Wylie David C, Frei Andreas, Shaobin Zhuang, Yan-Hui Liu, Frederick William Porter, Collette M. Cutler, and John T. Tang
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Ultraviolet Rays ,viruses ,Genetic Vectors ,Cell Separation ,Biology ,Recombinant virus ,medicine.disease_cause ,Virus ,Mass Spectrometry ,law.invention ,Adenoviridae ,Cell Line ,Viral Proteins ,Column chromatography ,Capsid ,law ,Genetics ,medicine ,Centrifugation, Density Gradient ,Humans ,Centrifugation ,Molecular Biology ,Chromatography, High Pressure Liquid ,Differential centrifugation ,Chromatography ,Gene Transfer Techniques ,biochemical phenomena, metabolism, and nutrition ,Chromatography, Ion Exchange ,Flow Cytometry ,Genes, p53 ,Molecular biology ,Microscopy, Electron ,Spectrophotometry ,Recombinant DNA ,Chromatography, Gel ,Molecular Medicine ,Electrophoresis, Polyacrylamide Gel - Abstract
Empty capsids from adenovirus, that is, virus particles lacking DNA, are well documented in the published literature. They can be separated from complete virus by CsCl density gradient centrifugation. Here we characterize the presence of empty capsids in recombinant adenovirus preparations purified by column chromatography. The initial purified recombinant adenovirus containing the p53 tumor suppressor gene was produced from 293 cells grown on microcarriers and purified by passage through DEAE-Fractogel and gel-filtration chromatography. Further sequential purification of the column-purified virus by CsCl and glycerol density gradient centrifugations yielded isolated complete virus and empty capsids. The empty capsids were essentially noninfectious and free of DNA. Analysis of empty capsids by SDS-PAGE or RP-HPLC showed the presence of only three major components: hexon, IIIa, and a 31K band. This last protein was identified as the precursor to protein VIII (pVIII) by mass spectrometric analysis. No pVIII was detected from the purified complete virus. Analysis by electron microscopy of the empty capsids showed particles with small defects. The amount of pVIII was used to determine the level of empty capsid contamination. First, the purified empty capsids were used to quantify the relation of pVIII to empty capsid particle concentration (as estimated by either light scattering or hexon content). They were then used as a standard to establish the empty capsid concentration of various recombinant adenovirus preparations. Preliminary research showed changes in empty capsid concentration with variations in the infection conditions. While virus purification on anion-exchange or gel-filtration chromatography has little effect on empty capsid contamination, other chromatographic steps can substantially reduce the final concentration of empty capsids in column-purified adenovirus preparations.
- Published
- 2001
7. Investigations of PEGylated Recombinant Adenovirus, Using Fluorescein-Labeled Polyethylene Glycol
- Author
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Lee, Seoju, primary, Ravindran, Sundari, additional, and Vellekamp, Gary, additional
- Published
- 2007
- Full Text
- View/download PDF
8. Characterization of Hemodynamic Events Following Intravascular Infusion of Recombinant Adenovirus Reveals Possible Solutions for Mitigating Cardiovascular Responses
- Author
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Machemer, Todd, primary, Engler, Heidrun, additional, Tsai, Van, additional, Lee, Seoju, additional, Cannon-Carlson, Susan, additional, Voloch, Marcio, additional, Schluep, Thomas, additional, Ravindran, Sundari, additional, Vellekamp, Gary, additional, Brin, Elena, additional, Cornell, Douglas, additional, Sutjipto, Suganto, additional, Wen, Shu Fen, additional, Horn, Mark, additional, Van Rooijen, Nico, additional, Maneval, Dan, additional, Hutchins, Beth, additional, and LaFace, Drake, additional
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- 2005
- Full Text
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9. Characterization of Empty Capsids from a Conditionally Replicating Adenovirus for Gene Therapy
- Author
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Sutjipto, Suganto, primary, Ravindran, Sundari, additional, Cornell, Douglas, additional, Liu, Yan-Hui, additional, Horn, Mark, additional, Schluep, Thomas, additional, Hutchins, Beth, additional, and Vellekamp, Gary, additional
- Published
- 2005
- Full Text
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10. 781. Quantification of Empty Capsids in Preparations of Conditionally Replicating Adenovirus
- Author
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Sundari Ravindran, Suganto Sutjipto, Vellekamp Gary J, Yan-Hui Liu, and Xiaoyu Yang
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Pharmacology ,Alternative methods ,Capsid ,Chemistry ,viruses ,Drug Discovery ,Genetics ,Molecular Medicine ,Adenovirus Protein ,biochemical phenomena, metabolism, and nutrition ,Molecular Biology ,Virology - Abstract
For a previously studied replication-deficient rAd, we found that the empty capsids in these preparations had a high amount of pVIII (precursor to adenovirus protein VIII). This precursor protein was quantified by SDS-PAGE densitometry or analytical RP-HPLC. These techniques determined the concentration of empty capsids (ECpVIII) in these preparations. But these techniques were not useful for quantification of the empty capsids from a conditionally replicating rAd due to low levels of pVIII. Here we studied alternative methods to quantify this different type of empty capsid.
- Published
- 2004
11. Empty Capsids in Column-Purified Recombinant Adenovirus Preparations
- Author
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Vellekamp, Gary, primary, Porter, Frederick W., additional, Sutjipto, Suganto, additional, Cutler, Collette, additional, Bondoc, Larry, additional, Liu, Yan-Hui, additional, Wylie, David, additional, Cannon-Carlson, Susan, additional, Tang, John T., additional, Frei, Andreas, additional, Voloch, Marcio, additional, and Zhuang, Shaobin, additional
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- 2001
- Full Text
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12. Allotropism in Aspartyl-tRNA Synthetase from Porcine Thyroid.
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Vellekamp, Gary J. and Kull, Fredrick J.
- Subjects
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TRANSFER RNA , *LIGASES , *THYROID gland , *GEL permeation chromatography , *RIBONUCLEASES , *DISSOCIATION (Chemistry) - Abstract
Three forms aspartyl-tRNA synthetase, PC-1, PC-2 and PC-3 (based on their order of elution from phosphocellulose columns), were purified from porcine thyroid utilizing fractional pH precipitations and columns chromatography. Two forms, PC-1 and PC-2, eluted identically from gel filtration columns and migrated the same electrophoretically and in glycerol density gradients. They were estimated to have sedimentation coefficients of 7 S and molecular weights of about 150000. Both PC-1 and PC-2 were equally inhibited by KCl. Their elution positions from phosphocellulose were unchanged upon rechromatography, indicating that they were non-equilibrium forms and they were present in post-mitochondrial supernatants in roughly equal amounts. All three forms were present in the same ratios whether or not phenylmethylsulphonyl fluoride was present in homogenizing buffers PC-3 had the characteristics of an aminoacyl-tRNA synthetase complex. It contained aminoacyl-tRNA synthetase activity for 16 of 18 amino acids tested and was about 4% low-molecular-weight RNA. The complex did not significantly penetrate 5% polyacrylaimde gels, was excluded by Sephacryl S-200 and had a sedimentation coefficient greater than 20 S indicating a particles mass in excess of 500000 daltons. In addition, the PC-3 fraction contained a ribonuclease capable of degrading both aminoacyl-tRNA and tRNA. After storage, rechromatography of PC-3 on phosphocellulose showed that some dissociation of the enzymes had taken place. Aspartyl-tRNA synthetase activity was found in positions analogous to PC-1 as well as PC-3, and ribonuclease activity was found in two positions on the columns, one coincident with PC-3 and one preceding the position of elution of PC-1. Dissociation of the complex was also observed using glycerol density gradient centrifugation and by chromatography on Sepharose4B. When present the PC-3 complex, the aspartyl-tRNA synthetase activity and the ribonuclease activity were both stimulated by KCl. However, when dissociated to their free forms, the aspartyl-tRNA synhetase activity was inhibited by KCl, whereas the ribonuclease remained stimulated The effects on aspartyl-tRNA synthetase appeared to be potassium-ion-specific but were more pronounced in the presence of phosphate dianion than in chloride ion. The differential effects of potassium ion on the free and complexed forms of aspartyl-tRNA synthetase and the prescence of a ribonuclease in the aminoacyl-tRNA complex that is active toward tRNA could have functional significance in the intact cell. [ABSTRACT FROM AUTHOR]
- Published
- 1981
- Full Text
- View/download PDF
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