Differential sensitivity of lipegfilgrastim and pegfilgrastim to neutrophil elastase correlates with differences in clinical pharmacokinetic profile.

To assess the basis of the different half-lives of long-acting human granulocyte colony-stimulating factor (G-CSF) drugs, the effect of neutrophil elastase on lipegfilgrastim and pegfilgrastim was investigated. Sensitivity to human neutrophil elastase (HNE) was evaluated by incubating the drugs with HNE followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Drugs were also incubated with isolated human neutrophils followed by Western blot analysis. Lipegfilgrastim was more resistant to degradation with HNE or neutrophils than pegfilgrastim and appeared more intact on SDS-PAGE gels and Western blots. Lipegfilgrastim retained more functional activity than pegfilgrastim after incubation with HNE (67% vs ∼ 9%, respectively) or neutrophils (80% vs ∼ 4%, respectively) as assessed in an NFS-60 cell-based [(3) H]-thymidine incorporation assay. The binding and affinity of untreated lipegfilgrastim and pegfilgrastim for G-CSF receptors were evaluated using an NFS-60 competitive G-CSF receptor-binding assay and surface plasmon resonance. Untreated drugs were also evaluated in the functional NFS-60 thymidine incorporation assay. G-CSF receptor binding, receptor affinity, and functional activity were comparable between untreated drugs. The results showed a greater resistance to neutrophil elastase degradation and concomitant retention of functional activity of lipegfilgrastim compared with pegfilgrastim, which potentially explains the clinical observations of a longer half-life of lipegfilgrastim versus pegfilgrastim.

Optimization of BLyS production and purification from Escherichia coli.

B lymphocyte stimulator (BLyS) is a member of the tumor necrosis factor superfamily of cytokines. When the 152 amino acids of the C-terminus are associated into a homotrimer, this protein exhibits the ability to stimulate B cell proliferation and differentiation. Since numerous potential therapeutic indications have been identified for BLyS and other BLyS-derived products, large quantities of the protein are needed to further basic research and clinical trials. In this work, we have developed a high yield recombinant expression system that utilizes Escherichia coli as the host organism. Recombinant soluble BLyS (rsBLyS) production was achieved through the use of the phoA promoter system. This expression system, coupled to a semi-defined fermentation process, resulted in final purified yields of 435 mg/L of properly folded, trimeric, biologically active rsBLyS. This level of production is an 11-fold increase in volumetric yields compared to the process currently being used for clinical production. Furthermore, the increased rsBLyS production obtained from this process enabled the development of a conventional purification scheme that eliminated the use of a BLyS-affinity resin.

Production of biologically active Bacillus anthracis edema factor in Escherichia coli.

Anthrax is caused by the gram-positive spore-forming bacterium Bacillus anthracis. The anthrax toxin consists of three proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF). PA facilitates the translocation of LF and EF into the cytosol of mammalian cells. LF is thought to be a zinc-dependent metalloprotease that results in death. EF is a calmodulin- and calcium-dependent adenylate cyclase that causes edema upon entrance into the cytosol by elevating the cAMP levels in cells. Previous efforts to produce recombinant EF (rEF) in Escherichia coli yielded only 2.5 mg of rEF per liter of culture. In this work, we produced soluble rEF in large quantities in both the periplasm and cytoplasm of E. coli from shake flasks and fermentors. The rEF protein was purified by standard chromatography and yielded >97% pure, biologically active rEF. Yields of purified rEF from medium cell density fermentations resulted in up to 2.38 g/L of highly pure, biologically active rEF protein. These results exhibit the ability to generate gram quantities of active rEF from E. coli.

Production and purification of Bacillus anthracis protective antigen from Escherichia coli.

Anthrax is caused by the gram-positive, spore-forming bacterium, Bacillus anthracis. The anthrax toxin consists of three proteins, protective antigen (PA), lethal factor, and edema factor. Current vaccines against anthrax use PA as their primary component since it confers protective immunity. In this work, we expressed soluble, recombinant PA in relatively high amounts in the periplasm of E. coli from shake flasks and bioreactors. The PA protein was purified using Q-Sepharose-HP and hydroxyapatite chromatography, and routinely found to be 96-98% pure. Yields of purified PA varied depending on the method of production; however, medium cell density fermentations resulted in approximately 370 mg/L of highly pure biologically active PA protein. These results exhibit the ability to generate gram quantities of PA from E. coli.

Steroid regulation of midgut cell death during Drosophila development.

Steroid hormones trigger dynamic tissue changes during animal development by activating cell proliferation, cell differentiation, and cell death. Here we characterize steroid regulation of changes in midgut structure during the onset of Drosophila metamorphosis. Following an increase in the steroid 20-hydroxyecdysone (ecdysone) at the end of larval development, future adult midgut epithelium is formed, and the larval midgut is rapidly destroyed. Mutations in the steroid-regulated genes BR-C and E93 differentially impact larval midgut cell death but do not affect the formation of adult midgut epithelia. In contrast, mutations in the ecdysone-regulated E74A and E74B genes do not appear to perturb midgut development during metamorphosis. Larval midgut cells possess vacuoles that contain cellular organelles, indicating that these cells die by autophagy. While mutations in the BR-C, E74, and E93 genes do not impact DNA degradation during this cell death, mutations in BR-C inhibit destruction of larval midgut structures, including the proventriculus and gastric caeca, and E93 mutants exhibit decreased formation of autophagic vacuoles. Dying midguts express the rpr, hid, ark, dronc, and crq cell death genes, suggesting that the core cell death machinery is involved in larval midgut cell death. The transcription of rpr, hid, and crq are altered in BR-C mutants, and E93 mutants possess altered transcription of the caspase dronc, providing a mechanism for the disruption of midgut cell death in these mutant animals. These studies indicate that ecdysone triggers a two-step hierarchy composed of steroid-induced regulatory genes and apoptosis genes that, in turn, regulate the autophagic death of midgut cells during development.