Recovery of bound homologous protein antigens from disulphide-linked immunosorbents at neutral pH

Affinity purification of tetanus toxin using polyclonal and monoclonal antibody immunoadsorbents

Tetanus toxin has been immunopurified on immunoadsorbent columns derived from equine polyclonal antitoxin coupled to cyanogen bromide-activated Sepharose CL4B. Desorption of bound toxin in active form was achieved only when the immunoadsorbent was mixed with Sephadex G15 and this mixture overlaid on a further volume of Sephadex G15. With equine antibody, 64% of adsorbed toxin was recovered with a specific activity of 2400 limiting flocculation units (Lf)/mg protein N (1.2 X 10(8) minimum lethal doses (MLD)/mg protein N). Similarly prepared immunoadsorbent derived from murine monoclonal antitoxin of low affinity had improved desorption with less acidic desorbents, without the requirement for Sephadex G15; greater than 80% of adsorbed toxin was recovered with a specific activity of 3000 Lf/mg protein N (1.6 X 10(8) MLD/mg protein N).

A general method for the isolation of haptoglobin 1-1, 2-1, and 2-2 from human plasma

A general method for the isolation of haptoglobin 1-1, 2-1, and 2-2 human plasma is described. Plasma is fractionated by affinity chromatography on chicken hemoglobin-Sepharose using the full capacity of the column; then after washing the column thoroughly, haptoglobin is eluted with 8 M urea and the eluate is collected in fractions to separate active and denatured haptoglobin. The urea-free, active fractions of haptoglobin are fractionated by affinity chromatography on Affi-Gel Con A to remove nonglycoproteins, principally apolipoprotein A-I, and the haptoglobin is eluted with 0.5 M glucose. Then the haptoglobin-containing fractions are fractionated by negative immunoadsorption chromatography on anti-chicken hemoglobin-protein A-Sepharose to remove chicken hemoglobin-human haptoglobin complexes. Haptoglobin prepared by this three-step procedure is biologically active and nearly homogeneous. The recovery is approximately 70%, irrespective of phenotype. The procedure can be completed in 3 days. A partial purification of apolipoprotein A-I is obtained simultaneously by this method.

Heterogeneity of pregnancy-specific beta 1-glycoprotein following purification from maternal serum and partial characterization of a high-molecular-weight component

Pregnancy-Specific beta 1-Glycoprotein (PSB1G) has been purified from maternal serum by physico-chemical and immunochemical methods. Marked instability of the protein was noted after partial purification which correlated with hydroxylapatite chromatography of PSB1G. Three molecular heterogeneous forms were demonstrated by gel filtration on Sephacryl S-200 which were designated as PSB1G-I, II and III. Each of the latter purified materials displayed altered immunoelectrophoretic mobility, i.e., altered from beta 1 to gamma mobility. In immunodiffusion experiments PSB1G-I reacted in complete immunological identity with 'native' serum PSB1G whereas PSB1G-II and III reacted in partial identity with each of the latter, suggesting that they are dissociation and/or degradation products of the parent PSB1G. The apparent molecular weights of PSB1G-I, II and III as determined by gel filtration were 280 000, 69 000 and 23 000, respectively, PSB1G-I was selected for structural analysis on the basis of its immunological identity with 'native' antigen. SDS-PAGE studies of PSB1G-I with and without reducing agent strongly suggest that PSB1G-I and 'native' serum antigen are composed of two dissimilar subunits of equal molecular size which are bonded together by non-covalent linkage. One of the subunits appears to represent a single polypeptide chain, whereas the other subunit appears to be composed of two polypeptide chains of unequal size that are linked together by covalent bonds. Investigations are continuing towards confirmation of the proposed structural model of PSB1G-I by an alternate methodology of protein structure analysis.

Vaccinia virus cytotoxin

Extracts of vaccinia-infected HeLa cells were rendered free from infectious virus by centrifugation followed by membrane filtration and were shown to be toxic to uninfected HeLa cells in the presence of hypertonic MgSO4, used as a macromolecular uptake inducer, under conditions which did not kill control cells. Extracts from uninfected cells were nontoxic. This biological test was adapted to a semi-quantitative assay which was used to monitor the purification of the cytotoxic factor by DEAE-cellulose and Sephadex G-100 chromatography. The cytotoxic factor was purified 100-fold, shown to be of molecular weight 30 -- 100,000 daltons, acidic and completely inactivated by soluble trypsin but not by ribonuclease under conditions believed to degrade both single- and double-stranded RNA species. It was demonstrated to be virus specific by approrpiate immunosorbent chromatography. Extracts were also prepared from vaccinia-infected HEp-2, RK and W-K cells respectively. A virus-specific factor, toxic to uninfected HeLa cells, with similar chromatographic properties to that isolated from infected HeLa cells, was isolated from these three additional cell lines. The concept of virus induced cytotoxins, substances which exert their toxic effect in the host cells in which they are made, is discussed.