Article

Development and evaluation of an ELISA for quantification of human alpha-1-proteinase inhibitor in complex biological mixtures

Division of Hematology, Center for Biologics Evaluation and Research, United States Food and Drug Administration, 29 Lincoln Drive, Bethesda, MD 20892, USA.
Biologicals (Impact Factor: 1.41). 11/2007; 35(4):285-95. DOI: 10.1016/j.biologicals.2006.11.002
Source: PubMed

ABSTRACT Human alpha-1-proteinase inhibitor(1) (alpha(1)-PI) is the most abundant serine protease inhibitor in plasma. Its major function is inhibition of neutrophil elastase in lungs. alpha(1)-PI deficiency may result in severe, ultimately fatal emphysema. Three plasma-derived (pd-) alpha(1)-PI products are licensed in the US for replacement therapy of deficient patients. The recombinant versions (r-alpha(1)-PI), proposed as alternatives to pd-alpha(1)-PI products, have been under intensive investigation. For accurate determination of alpha(1)-PI from different sources and in various forms, there is an obvious need for reliable standardized assays for alpha(1)-PI quantification and potency measurements. As a part of our multi-step research focused on alpha(1)-PI structure-function investigation, we have established a simple and reproducible double-sandwich ELISA based on commercially available polyclonal antibodies. The developed ELISA allows the quantification of both pd-alpha(1)-PI and r-alpha(1)-PI in various complex matrices. A validation of the ELISA was performed with the working range of the assay (3.1-50 ng/ml) established on the bases of the following parameters: linearity (3-100 ng/ml, r(2)=0.995); accuracy (87.3-114.6% recovery); intra-assay precision (%CV, 2.8%); inter-assay plate-to-plate precision (3.9% per day and 4.1% day-to-day); detection limit (1.10 ng/ml); and quantification limit (3.34 ng/ml). The analytical performance of the alpha(1)-PI ELISA indicates that this assay can be used for monitoring concentration levels of alpha(1)-PI in multi-component biological matrices, based on the following: (a) quantification of r-alpha(1)-PI in various fermentation mixtures (E. coli and A. niger); (b) investigation of alpha(1)-PI enzymatically digested in the conditions of harsh fungal proteolysis; (c) evaluation of thermally polymerized alpha(1)-PI; (d) quantification of alpha(1)-PI in human serum; and (e) comparative quantification of alpha(1)-PI in commercially available products.

Full-text

Available from: Elena Karnaukhova, Dec 20, 2014
0 Followers
 · 
90 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Human alpha1-proteinase inhibitor (alpha1-PI), also known as antitrypsin, is the most abundant serine protease inhibitor (serpin) in plasma. Its deficiency is associated with development of progressive, ultimately fatal emphysema. Currently in the United States, alpha1-PI is available for replacement therapy as an FDA licensed plasma-derived (pd) product. However, the plasma source itself is limited; moreover, even with efficient viral inactivation steps used in manufacture of plasma products, the risk of contamination from emerging viruses may still exist. Therefore, recombinant alpha1-PI (r-alpha1-PI) could provide an attractive alternative. Although r-alpha1-PI has been produced in several hosts, protein stability in vitro and rapid clearance from the circulation have been major issues, primarily due to absent or altered glycosylation. We have explored the possibility of expressing the gene for human alpha1-PI in the filamentous fungus Aspergillus niger (A. niger), a system reported to be capable of providing more "mammalian-like" glycosylation patterns to secretable proteins than commonly used yeast hosts. Our expression strategy was based on fusion of alpha1-PI with a strongly expressed, secreted leader protein (glucoamylase G2), separated by dibasic processing site (N-V-I-S-K-R) that provides in vivo cleavage. SDS-PAGE, Western blot, ELISA, and alpha1-PI activity assays enabled us to select the transformant(s) secreting a biologically active glycosylated r-alpha1-PI with yields of up to 12 mg/L. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis further confirmed that molecular mass of the r-alpha1-PI was similar to that of the pd-alpha1-PI. In vitro stability of the r-alpha1-PI from A. niger was tested in comparison with pd-alpha1-PI reference and non-glycosylated human r-alpha1-PI from E. coli. We examined the suitability of the filamentous fungus A. niger for the expression of the human gene for alpha1-PI, a medium size glycoprotein of high therapeutic value. The heterologous expression of the human gene for alpha1-PI in A. niger was successfully achieved to produce the secreted mature human r-alpha1-PI in A. niger as a biologically active glycosylated protein with improved stability and with yields of up to 12 mg/L in shake-flask growth.
    Microbial Cell Factories 02/2007; 6:34. DOI:10.1186/1475-2859-6-34 · 4.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Se estableció y validó un ELISA para la cuantificación del Interferón alfa 2b humano recombinante en el Ingrediente Farmacéutico Activo, definiéndose los criterios de validez del ensayo y basado en el cumplimiento de las Buenas Prácticas de Laboratorio. Se evaluaron los parámetros de: linealidad, especificidad, exactitud, rango, precisión y robustez. El ensayo establecido resultó específico, con una exactitud entre 84,3% y 102,4%, se demostró un ajuste cuadrático y un rango de trabajo entre 1 y 10 ng/mL; la repetibilidad y la precisión intermedia mostraron coeficientes de variación inferiores al 10% y 20% respectivamente, y se comprobó la robustez del método conrespecto al efecto borde y la estabilidad de las soluciones.
    01/2009;