Development of a plasma- and albumin-free recombinant von Willebrand factor.

Baxter has developed a recombinant therapy for treating von Willebrand's disease. Recombinant VWF is co-expressed with the rFVIII in CHO cells used to produce the rFVIII product Advate. This rVWF is used as a drug component for a rVWF-rFVIII complex drug product. CHO cells produce partially processed and partially un-processed rVWF still containing the pro-peptide. In order to make a consistent preparation containing mature and processed rVWF only rVWF is exposed to recombinant furin to remove the pro-peptide. Recombinant VWF and furin are produced under serum- and protein-free conditions. It is highly purified by a series of chromatographic steps and formulated in a protein-free buffer and has a homogeneous multimer distribution. The specific activity is higher in rVWF than in commercial plasma-derived VWF-FVIII complex products. SDS agarose electrophoretic analysis shows the presence of ultra-high molecular weight multimers. The FVIII-binding capacity and affinity of rVWF to FVIII is comparable to VWF in plasma. Carbohydrate analysis shows an intact glycosylation pattern. Recombinant VWF binds to collagen and promotes platelet adhesion under shear stress. It stabilizes endogenous FVIII in VWF-deficient knock-out mice as seen by a secondary rise in murine FVIII.

Preparation and properties of an alpha-1-protease inhibitor concentrate with high specific activity.

BACKGROUND AND OBJECTIVES: Because the current demand for alpha-1-protease inhibitor (A1PI) exceeds the available supply, we aimed to develop a process for purification of A1PI from plasma which would achieve the highest possible degree of purity, specific activity and yield. MATERIALS AND METHODS: A1PI was purified from Cohn fraction IV-1,4 using ethanol precipitation and Q-Sepharose chromatography. Ceramic hydroxyapatite chromatography was used as a final purification step. Two independent virus-inactivation procedures (chemical and vapour heating) were applied. RESULTS: The resulting A1PI had an unprecedented high specific activity. In addition, the process led to the discovery of a new isoform of A1PI in isoelectric focusing gels. CONCLUSION: The high specific activity of the A1PI preparation achieved with this process should allow a reduction of the A1PI total protein load necessary to achieve clinically relevant effects.

Identification of meningeal cell released neurite promoting activities for embryonic hippocampal neurons.

Primary cultures of meningeal cells from embryonic rat cerebra secrete neurite growth-inducing components into serum-free culture medium. This conditioned medium (CM) was analyzed by FPLC and immunochemical and enzymatic treatments and tested for neurite promoting activity (NPA) in a quantitative bioassay using hippocampal neurons from embryonic rat. By immunoprecipitation or specific adsorption we identified laminin (LN)-proteoglycan complexes and fibronectin (FN), respectively, as the major neurite promoting components within meningeal cell CM. The LN-proteoglycan complexes and their NPA were sensitive to chondroitinase (chondroitin ABC lyase, EC 4.2.2.4) and to a smaller extent to heparitinase (heparitin sulfate lyase, EC 4.2.2.8). Minor fractions of the total NPA in CM correlated with free LN and a putative but not yet characterized FN-proteoglycan complex.

Glial support of CNS neuronal survival, neurite growth and regeneration.

In an attempt to identify specific molecular and cellular requirements necessary to support long-term maintenance and differentiation of central neurons we have identified laminin-HSPG and free fibronectin as two major neurite promoting substrate adhesion factors released by immature cerebral astrocytes in serum-free culture. Astrocytes further secrete diffusible neurotrophic protein factor(s) which are permanently required for survival of cultured neurons from various brain regions. However, both the presence of substrate-bound neurite-promoting factors and diffusible neurotrophic activities were not sufficient to support long-term maintenance of central neurons in culture. Cell contact-mediated interactions which appear to be cell type-restricted (e.g. to neurons and astrocytes, but not to fibroblasts) are further required for neuronal stabilization. The implantation of immature astroglial cells into the injured adult CNS should provide a supportive environmental condition for damaged neurons to enhance their recovery and stimulate regenerative responses.

Astroglia-released neurite growth-inducing activity for embryonic hippocampal neurons is associated with laminin bound in a sulfated complex and free fibronectin.

Neurons from embryonic (E18) rat hippocampus were chosen to identify and characterize neurite growth-stimulating proteins accumulating in serum-free conditioned media (CM) obtained from primary or secondary cultures of cerebral astrocytes (less than 5% nonglial cells) using a quantitative cell culture bioassay. CM were fractionated by FPLC on an anion exchange column (Mono Q) and by gel filtration (Superose 6). Column fractions were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblotting and enzyme-linked immunosorbent assay (ELISA) using antibodies to laminin (LN) and fibronectin (FN). The neurite-promoting activity (NPA) was tested by incubating aliquots of the eluted fractions with poly-L-lysine precoated glass coverslips prior to addition of neurons suspended in chemically defined medium. We provide evidence that the NPA in astroglial CM could be assigned mainly to a negatively charged, highly sulfated LN complex consisting predominantly of the B-chains of LN and presumably a sulfated proteoglycan that was sensitive for chondroitinase and to a lower degree to heparinase degradation. In addition, a smaller proportion of the NPA was associated with uncomplexed LN and free FN. FN reached approximately 10 times the concentration of LN in astroglial CM. As revealed by immunofluorescence microscopy, both LN and FN are simultaneously expressed by cultured astrocytes; however, only the production of FN, measured by ELISA, increased during the time astrocytes were in culture, whereas the release of LN remained unchanged. We conclude that, besides the most active LN complex, FN bound to a polycationic matrix is able to induce neurite growth in hippocampal neurons in vitro.

T-lymphocyte colony formation of murine thymocytes in agar contained in glass capillaries.

Optimal growth conditions are presented for a new colony test with mouse thymocytes in agar contained in glass capillaries. The kinetics of colony growth and the dependence from the PHA-, I1-2-, agar- and 2-mercaptoethanol concentration are shown. The colony forming cells are identified as T-lymphocytes by usual morphology and by an indirect immunoperoxidase method using mouse anti-Thy 1.2 antibodies.

Low molecular mass inhibitors from calf thymus selective for T-lymphocyte proliferation.

Endogenous factors preferentially inhibiting T-lymphocyte proliferation were prepared from the acetone precipitate of a 60% ethanol extract from calf thymus and their biochemical properties examined. By ultrafiltration the strongest lymphocyte-selective inhibition was found in the molecular mass range between 1 and 5 kDa. Fast protein liquid chromatography (FPLC) of this fraction on an anion exchange column eluted the lymphocyte inhibitors at 205-265 mM ammonium acetate. Staining procedures following IEF and TLC suggested, that the inhibitors may not be glycoconjugates or amines but small weakly acidic peptides (less than 3 kDa).

Acidic "peptidophospholipids", a new class of hapten-bearing cell surface modifying reagents.

Covalent coupling of glutamyl-glutamic acid to the amino group of ether-phosphatidylethanolamine (EPE) yields an acidic "peptidophospholipid" (Glu2-EPE) which is water-soluble above pH 7.0 and stable to phospholipase A. The terminal amino group of Glu2-EPE is free for coupling with amino-reactive determinants. We describe the synthesis of various hapten-substituted peptidophospholipids as well as of an intermediate compound, coupled with the heterobifunctional reagent 3-(2'-pyridyl)-dithiopropionic acid N-hydroxysuccinimide ester. The latter derivative allows binding to sulfhydryl-containing molecules, e.g. peptides or proteins. So far, beef and pig insulin as well as trinitrophenyl-substituted ribonuclease A have thus been linked to Glu2-EPE. All derivatives of Glu2-EPE are water-soluble at physiological pH and readily adsorb to cell surfaces from aq. solution. Binding to cells is fast, stable and "non-toxic" over a wide range of concns. The adsorbed determinants are accessible to specific antibodies and facilitate complement-mediated cell lysis. Glu2-EPE thus appears to be a universal carrier molecule for fast, simple and mild modification of cells with foreign determinants, e.g. for Jerne plaque assays.