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Biomedical subjects

Eric Weber

Publications and source records attributed to Eric Weber.

7 recordsLinked to original sources
PubMed2006

A semi-automated large-scale process for the production of recombinant tagged proteins in the Baculovirus expression system.

The efficient preparation of recombinant proteins at the lab-scale level is essential for drug discovery, in particular for structural biology, protein interaction studies and drug screening. The Baculovirus insect-cell expression system is one of the most widely applied and highly successful systems for production of recombinant functional proteins. However, the use of eukaryotic cells as host organisms and the multi-step protocol required for the generation of sufficient virus and protein has limited its adaptation to industrialized high-throughput operation. We have developed an integrated large-scale process for continuous and partially automated protein production in the Baculovirus system. The instrumental platform includes parallel insect-cell fermentation in 10L BioWave reactors, cell harvesting and lysis by tangential flow filtration (TFF) using two custom-made filtration units and automated purification by multi-dimensional chromatography. The use of disposable materials (bags, filters and tubing), automated cleaning cycles and column regeneration, prevent any cross-contamination between runs. The preparation of the clear cell lysate by sequential TFF takes less than 2 h and represents considerable time saving compared to standard cell harvesting and lysis by sonication and ultra-centrifugation. The process has been validated with 41 His-tagged proteins with molecular weights ranging from 20 to 160 kDa. These proteins represented several families, and included 23 members of the deubiquitinating enzyme (DUB) family. Each down-stream unit can process four proteins in less than 24 h with final yields between 1 and 100 mg, and purities between 50 and 95%.

Animals↗
PubMed2006

Acanthamoeba keratitis in a U.S. Army soldier after unauthorized use of contact lenses in the combat theater.

A 25-year-old active duty Army E-5 developed severe infectious keratitis in his left eye secondary to soft contact lens (CL) wear while deployed in Iraq, necessitating evacuation to Walter Reed Army Medical Center for further evaluation and treatment. Initial clinical examination at Walter Reed Army Medical Center was suggestive of Acanthamoeba keratitis, a serious corneal pathogen associated with CL wear. In vivo confocal microscopy demonstrated Acanthamoeba cysts in the epithelium and anterior stroma, and smears and cultures from an epithelial biopsy specimen confirmed the diagnosis of Acanthamoeba keratitis. To our knowledge this is the first reported case of Acanthamoeba keratitis in a soldier wearing CLs in the combat theater. Because of the inability to maintain proper lens hygiene in a combat or field environment, the risk of developing a potentially sight-threatening corneal infection is significant. This unfortunate case of a devastating eye infection serves as a reminder of the current Army policy, which prohibits the use of CLs during gas chamber exercises, field training, and combat.

Acanthamoeba↗
PubMed2005

Gas-inducible product gene expression in bioreactors.

Inducible transgene expression technologies are of unmatched potential for biopharmaceutical manufacturing of unstable, growth-impairing and cytotoxic proteins as well as conditional metabolic engineering to improve desired cell phenotypes. Currently available transgene dosing modalities which rely on physical parameters or small-molecule drugs for transgene fine-tuning compromise downstream processing and/or are difficult to implement technologically. The recently designed gas-inducible acetaldehyde-inducible regulation (AIR) technology takes advantage of gaseous acetaldehyde to modulate product gene expression levels. At regulation effective concentrations gaseous acetaldehyde is physiologically inert and approved as food additive by the Federal Drug Administration (FDA). During standard bioreactor operation, gaseous acetaldehyde could simply be administered using standard/existing gas supply tubing and eventually eliminated by stripping with inducer-free air. We have determined key parameters controlling acetaldehyde transfer in three types of bioreactors and designed a mass balance-based model for optimal product gene expression fine-tuning using gaseous acetaldehyde. Operating a standard stirred-tank bioreactor set-up at 10 L scale we have validated AIR technology using CHO-K1-derived serum-free suspension cultures transgenic for gas-inducible production of human interferon-beta (IFN-beta). Gaseous acetaldehyde-inducible IFN-beta production management was fully reversible while maintaining cell viability at over 95% during the entire process. Compatible with standard bioreactor design and downstream processing procedures AIR-based technology will foster novel opportunities for pilot and large-scale manufacturing of difficult-to-produce protein pharmaceuticals.

Acetaldehyde↗
PubMed2003

Identification, characterization, and cloning of a complementary DNA encoding a 60-kd house dust mite allergen (Der f 18) for human beings and dogs.

BACKGROUND: House dust mites of the Dermatophagoides genus are the most important cause of perennial allergic disease in both humans and companion animals. Although the major mite allergens for humans are proteins of relatively low molecular weight, this is not the case for dogs. Western blotting shows that canine anti-mite IgE responses are directed primarily toward proteins in the molecular weight range of 50 to 120 kd. OBJECTIVE: The objectives of this study were to characterize a D farinae allergen with a molecular weight of approximately 60 kd and to isolate the cDNA coding for this allergen. METHODS: A protein of apparent molecular weight of 60 kd was identified by Western blotting by using canine serum IgE from house dust mite-sensitized atopic dogs. The protein was purified from homogenized D farinae mite bodies by ammonium sulfate precipitation, followed by gel filtration and cation exchange HPLC. The presence of IgE directed to the 60-kd protein in sera from humans and dogs with dust mite allergy was measured by FcepsilonRIalpha-based ELISA. A cDNA encoding a full-length 60-kd protein was isolated from a D farinae cDNA library by a combination of both PCR amplification and hybridization screening. A panel of mAbs specific for the 60-kd protein was generated and used to localize the protein in whole body sections of D farinae mites. RESULTS: ELISA showed that the purified protein bound IgE in 54% of the sera from patients with D farinae allergy. In addition, the 60-kd protein was able to bind IgE in 57% to 77% of D farinae -sensitized dogs. A cDNA was isolated that encoded a protein of 462 amino acids, consisting of a 25 amino acid signal sequence and a 437 amino acid mature protein. The calculated molecular weight of the mature protein is 50 kd, and the amino acid sequence contains a single N-glycosylation site. A protein database search showed homology with multiple chitinases. A mAb specific for the 60-kd chitinase recognized the allergen in the mite digestive system, but fecal pellets did not stain positively for this allergen. CONCLUSIONS: A 60-kd D farinae protein (Der f 18), with homology to chitinase, is a major allergen for humans and dogs sensitive to house dust mites.

Allergens↗