A ten-residue fragment of an antibody (mini-antibody) directed against lysozyme as ligand in immunoaffinity chromatography

The interaction between an antibody molecule and a protein antigen is an example of "natural" protein modelling. Amino acids of the antigen-binding site consisting of three hypervariable segments (L1, L2, L3) of the light (L) and three (H1, H2, H3) of the heavy (H) chain of an antibody molecule interact with amino acids present in an epitope of a protein. A ten-residue peptide was synthesized with an amino acid sequence analogous to the hypervariable L3 segment of a monoclonal antibody directed against lysozyme. The peptide was immobilized on CH-Sepharose 4B and the affinity adsorbent was used to purify lysozyme added to a detergent extract of insect cells infected with a recombinant baculovirus. This methodology may also be applicable to other antigen-antibody combinations, in immunoaffinity chromatography for selective purification of a protein or in an immunosensor for detection of a protein.

Immune inhibition of virus release from human and nonhuman cells by antibody to viral and host cell determinants

Immune inhibition of release of the DNA viruses, herpes simplex virus types 1 and 2 and pseudorabies virus by anti-viral and anti-host cell sera occurred while two RNA viruses, influenza and encephalomyocarditis, were inhibited only by anti-viral sera (not anti-host cell sera). Simian virus 40 and surprisingly two herpes viruses, bovine mamillitis and equine abortion, were not inhibited by either anti-viral or anti-host sera. Using the herpes simplex virus model, inhibition of virus release was detected in different cells of human and nonhuman origin with cross-inhibition between cell lines of different origin; thus, this form of immunotherapy may not require antibody to be tissue or organ specific. Evidence of inhibition of virus release from neoplastic and leukemic cell lines suggests possible application of this approach to control of virus-mediated leukoproliferative pathology (e.g. Burkitt's lymphoma or adult T cell leukemia).

Reactivity of human sera with overlapping synthetic peptides of herpes simplex virus type 1 glycoprotein D

Thirty eight human sera, seropositive for herpes simplex virus (HSV) and 56 human sera, seronegative for HSV by immunofluorescence and by ELISA, were investigated for reactivity with a series of overlapping synthetic peptides of HSV type 1 glycoprotein D (gD-1). Thirty four out of the 38 human sera positive for HSV reacted with peptides located between residues 300 and 369; the HSV-negative sera reacted with six of the gD-1 peptides, but with none of the peptides within residues 300 to 369.

Virus neutralizing activity induced by synthetic peptides of glycoprotein D of herpes simplex virus type 1, selected by their reactivity with hyperimmune sera from mice

Mice were immunized with synthetic peptides covering the first 56 amino acids of herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) and a fusion protein, produced in Escherichia coli, containing the first 55 amino acid residues of gD. It was found that mice immunized with peptides composed of amino acid residues 1 to 13, 18 to 30. 22 to 38 and 38 to 56 of gD were not significantly protected against a lethal challenge with HSV-1. Immunization with peptide 9-21 and the gD fusion protein resulted in significant protection. Antisera, from mice immunized with HSV-1, were investigated for reactivity with a series of 57 overlapping gD peptides covering the entire amino acid sequence, except for the membrane-spanning region. All antisera reacted with peptides 9-21, 10-24, 151-165, 216-232, 282-301 and with peptide 340-354 located in the anchoring region of gD, and 15 other peptides were recognized by at least one antiserum. Twelve peptides (10-24, 151-165, 216-232, 244-267, 260-274, 270-284, 260-284, 282-301, 300-314, 340-354, 348-362 and 355-369) reacted most frequently with the hyperimmune sera from mice and were selected for further study. These were conjugated to bovine serum albumin and used to immunize rabbits. Only antisera against peptide 10-24, which covers the same epitope as peptide 9-21, neutralized HSV-1 in vitro.

Synthetic antibody fragment as ligand in immunoaffinity chromatography

The possibility that a fragment of an antibody molecule may interact with a protein antigen was tested by studying the binding properties of a thirteen-residue synthetic peptide with an amino acid sequence similar to part of a hypervariable segment of a monoclonal antibody directed against lysozyme. Affinity adsorbents were prepared with this peptide and with non-related peptides as ligand. Non-specific interactions could be abolished by washing the column with 0.05 M sodium thiocyanate in 20 mM tris-HCl (pH 7.4). Lysozyme was only bound to the antilysozyme adsorbent and could be eluted with 1 M sodium thiocyanate. The results show that immunoaffinity chromatography with synthetic peptide ligands which mimic the antigen-binding site may be a useful tool in the selective purification of proteins.

Immunological properties of multiple repeats of a linear epitope of herpes simplex virus type 1 glycoprotein D

Several peptides containing the amino acid sequence 9-21 of glycoprotein D of herpes simplex virus type 1 (HSV-1) were synthesized and investigated for reactivity with monoclonal antibody LP14 in a competition enzyme-linked immunosorbent assay (ELISA). Peptides containing two or four repeats of sequence 9-21 reacted at least one order of magnitude better with LP14 than with the monomeric form of sequence 9-21. Dimers in which one of the repeats of one or more essential residues were absent did not show this increased reactivity. Antisera obtained from rabbits immunized with a peptide containing two repeats of sequence 9-21 coupled to bovine serum albumin showed high antipeptide antibody titers with this peptide and were able to neutralize virus infectivity in vitro. Sera obtained from rabbits immunized with the free dimer could not neutralize virus infectivity.

The influence of different adjuvants on the immune response to a synthetic peptide comprising amino acid residues 9-21 of herpes simplex virus type 1 glycoprotein D

The immuno-modulating properties of different adjuvant systems on the murine humoral and cellular immune response to a synthetic peptide comprising amino acid residues 9-21 of glycoprotein D of herpes simplex virus type 1 (HSV-1) were investigated. For immunization, the peptide was conjugated to ovalbumin or bovine serum albumin by glutaraldehyde and the adjuvants used in this study were Freund's complete adjuvant (FCA), aluminium hydroxide, the Ribi adjuvant system (RAS) and two non-ionic block polymer surfactants, viz. L101 and 31R1, in oil in water emulsions. High anti-peptide antibody titers were obtained after immunization with FCA, aluminium hydroxide, RAS and L101. All adjuvants, except RAS, stimulated the induction of delayed type hypersensitivity obtained after immunization with peptide 9-21 coupled to ovalbumin and elicited by injection of purified HSV-1 virions in the footpad. Challenge with a lethal dose of HSV-1 showed that mice immunized with peptide 9-21 coupled to ovalbumin in combination with FCA, RAS and L101, respectively, were significantly protected. Although immunization with peptide 9-21 coupled to ovalbumin combined with aluminium hydroxide stimulated induction of delayed type hypersensitivity, no significant protective immunity against the challenge was generated.

Comparison of non-ionic detergents for extraction and ion-exchange high-performance liquid chromatography of Sendai virus integral membrane proteins

The integral membrane proteins of Sendai virus haemagglutinin-neuraminidase (HN) and fusion protein (F) were extracted from purified virions with 2% of a non-ionic detergent, i.e., polyoxyethylene alkyl ethers varying by 8-14 hydrocarbon units in the alkyl chain and by 4-8 ethylene glycol units in the oxyethylene chain. Triton X-100 and octyl glucoside were included as reference detergents. The hydrophile-lipophile balance (HLB) and the critical micelle concentration (CMC) of the detergents were determined. A decrease in length of the oxyethylate by 8-5 ethylene glycol units and an increase in the alkylate by 8-12 hydrocarbon units resulted in higher yields of extracted proteins. The highest yields were obtained for C12E5 with an HLB of 11.7. Yields of extracted protein could be correlated with the HLB values of the polyoxyethylene alkyl ethers. The structural integrity of HN and F was not affected during extraction by either detergent as measured by their reactivity with monoclonal antibodies directed against native HN and F. Extracts were subjected to anion-exchange high-performance liquid chromatography (HPLC) on a Mono Q column in the presence of 0.1% of the detergent used for extraction. Eluate fractions were analysed by sodium dodecyl polyacrylamide gel electrophoresis and recoveries of HN and F protein were determined by size-exclusion HPLC. The immunological activity of HN and F was tested in an enzyme-linked immunosorbent assay. The highest recoveries of HN and F (80%) were obtained with C10E5 in the elution buffer. HN and F were partially purified and the immunological activity was well preserved.

Comparison of ion-exchange high-performance liquid chromatography columns for purification of Sendai virus integral membrane proteins

The recovery and separation of the integral membrane proteins, the haemagglutinin-neuraminidase (HN) and the fusion protein (F), from a Sendai virus detergent extract were compared on three different ion-exchange high-performance liquid chromatography (IE-HPLC) columns: Mono Q, TSK DEAE-NPR and Zorbax BioSeries SAX. The detergent, either 1-O-n-octyl-beta-glucopyranoside (octylglucoside) or decyl polyethylene glycol-300 (decyl PEG-300), used for extraction of HN and F proteins from the virions, was also present in the elution buffers at a concentration of 0.1%. Recovery of HN and F proteins was primarily dependent on the detergent present in the eluent, resulting in yields of HN varying from 18 to 28 and 56 to 67%, when octylglucoside and decyl PEG-300, respectively, were used. The highest yield for HN protein was obtained by separation on either a Mono Q or a TSK DEAE-NPR column with decyl PEG-300 as the additive. Yields of F protein were lower, and the highest recovery of 46% was found in the presence of decyl PEG-300 by separation on the Mono Q column. Analysis of the fractions by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and by size-exclusion HPLC indicated that the HN protein eluted in the presence of decyl PEG-300 from the Mono Q and the TSK DEAE-NPR columns was obtained in pure form, while the F protein was slightly contaminated with HN. Analysis of the fractions with monoclonal antibodies directed against conformational epitopes of HN and F proteins indicated that after IE-HPLC the conformation of the proteins is largely retained.

An efficient procedure for the isolation of recombinant baculovirus

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Immunological properties of an N-terminal fragment of herpes simplex virus type 1 glycoprotein D expressed in Escherichia coli

The N-terminal fragment, comprising residues -5 to 55 of herpes simplex virus type 1 glycoprotein D was expressed as a beta-galactosidase fusion protein in Escherichia coli. This gD-fusion protein reacts with monoclonal antibody LP 14 directed against glycoprotein D of HSV. Antisera obtained after immunization of rabbits with purified gD-fusion protein react with HSV-1 gD in a Western blot and with N-terminal synthetic peptides of gD. In addition, these antisera are able to neutralize viral infectivity in vitro.

Purification of fusion proteins expressed by pEX3 and a truncated pEX3 derivative

A derivative of the pEX3 expression vector was constructed that codes for the first 407 amino acids of the 1051 amino acids of the pEX3 fusion protein. The amount of truncated fusion protein (40 mg/g cells), obtained by expression in E. coli, was similar to that produced by the original pEX3 vector. The truncated fusion protein was purified more easily from E. coli contaminants than the original fusion protein by washing with 2 M urea and 0.5% Triton X-100.

Effect of detergents on the structure of integral membrane proteins of Sendai virus studied with size-exclusion high-performance liquid chromatography and monoclonal antibodies

The integral membrane proteins of Sendai virus, the fusion protein F (Mr = 65,000) and the haemagglutinin-neuraminidase protein HN (Mr = 68,000), were used as a model protein mixture. They were subjected to size-exclusion high-performance liquid chromatography on Superose 6HR columns with eluents containing various additives in order to solubilize the proteins. The effect of the additives on the structure of the membrane proteins was investigated with conformation-dependent monoclonal antibodies, either directed against F or HN protein, and by determination of the haemagglutinating capacity of the HN protein. The results show that the structure of the HN protein is more easily disturbed by eluents than that of the F protein. When the elution conditions are mild, e.g., 0.1% octylglucoside, the structure of both proteins is conserved but no separation is obtained. Elution with a buffer containing 0.05% sarkosyl (dodecyl methylglycine sodium salt) did not affect the structure and resulted in pure F protein. Pretreatment of the Amberlite XAD-2-treated Sendai virus envelope extract with 4% sodium dodecyl sulphate (SDS) and elution with 0.1% SDS in 50 mM sodium phosphate (pH 6.5) altered the structure of the HN protein but resulted in purification of the tetramer and the dimer of the HN protein, and the monomer of the F protein.

The influence of pH and ionic strength on the coating of peptides of herpes simplex virus type 1 in an enzyme-linked immunosorbent assay

Rabbits were immunized with synthetic peptides of herpes simplex virus type 1 glycoproteins, coupled to a carrier protein with glutaraldehyde. Antibodies directed against the peptides were determined in an enzyme-linked immunosorbent assay (ELISA). Either free peptides or peptides coupled with glutaraldehyde to another carrier protein than the one used for immunization were used as the coating antigen. When conjugated peptides were used as the coat, it was necessary in some instances to correct the antibody titers for a substantial amount of antibody activity against glutaraldehyde. When free peptides were used, optimal coating conditions with regard to pH and ionic strength had to be determined, since some peptides failed to coat under standard conditions, at pH 9.6. The results show that some peptides needed stringent pH conditions while others could be coated in a broad pH range. The addition of 0.6 M NaCl had a favorable effect on peptide coating.

Structural properties and reactivity of N-terminal synthetic peptides of herpes simplex virus type 1 glycoprotein D by using antipeptide antibodies and group VII monoclonal antibodies

To investigate the contribution of individual amino acids to the antigenicity of the N-terminal region of herpes simplex virus type 1 glycoprotein D, a series of 14 overlapping synthetic peptides within residues 1 to 30 were examined for their reactivity with monoclonal antibody LP14 (a group VII monoclonal antibody; in herpes simplex virus mutants resistant to LP14, arginine 16 is substituted by histidine) and two antipeptide antisera (antipeptide 9-21 and antipeptide 1-23). Maximal binding was achieved with peptides 9-21, 10-30, 9-30, and 8-30 and the chymotryptic fragment 9-17 of peptide 9-21, suggesting that a major antigenic site is located within residues 10 through 17. Lysine 10 was shown to be essential for high reactivity, either by binding directly to the antibody molecule or by stabilizing an ordered structure of the peptide. The importance of ordered structure was demonstrated by a decrease in reactivity after sodium dodecyl sulfate treatment of peptides 9-21 and 8-30.

Column liquid chromatography of integral membrane proteins

Biological membranes have as a major function the compartmentation of biological processes in cells and organelles. They consist of a bilayer of phospholipid molecules in which proteins are embedded. These integral membrane proteins, which cross the bilayer once or several times, generally have a higher than average hydrophobicity and tend to aggregate. Detergents are needed to remove integral membrane proteins from the lipid bilayer and they have to be present during further chromatographic purification. Predominantly, four modes of HPLC have been used alone or in combination for the purification of integral membrane proteins. These are based on differences of proteins in size (size-exclusion chromatography, SEC), electrostatic interaction (ion-exchange chromatography, IEC), bioaffinity (bioaffinity chromatography, BAC) and hydrophobic interaction (reversed-phase chromatography, RPC, and hydrophobic-interaction chromatography, HIC). SEC, IEC, BAC and HIC are used under relatively mild conditions, and buffer systems generally contain a non-ionic detergent. RPC generally has a denaturing effect on the protein and should preferably be used for the purification of integral membrane proteins smaller than 50 kD.

Purification strategies for Sendai virus membrane proteins

Viral membrane proteins extracted from Sendai virions with the non-ionic detergents decylpolyethyleneglycol-300 and Triton X-100 were used as a model mixture of hydrophobic membrane proteins. The detergent extract contained the fusion protein (F) and the tetrameric and dimeric forms of the hemagglutinin-neuraminidase protein (HN). These proteins were purified by size-exclusion high-performance liquid chromatography (HPLC) in the presence of 0.1% sodium dodecyl sulphate, by ion-exchange and metal chelate affinity HPLC in the presence of 0.1% decylpolyethyleneglycol, and by reversed-phase HPLC without prior removal of the detergent. The tetramer of HN and F could be purified by size-exclusion HPLC after dissociation of a micellar aggregate containing tetrameric HN and multimeric F. The F and HN proteins could be purified by ion-exchange HPLC. Pure F protein could be obtained after metal chelate affinity HPLC. The F protein and the dimer and tetramer of HN could be eluted from a large-pore (100 nm) reversed-phase column, but they were eluted as broad, overlapping peaks. Only after reduction of the virion extract, the relatively small (13-15 kilodaltons) F2 protein could be obtained in pure form.

Enzymatic inactivation of aztreonam by faecal enzyme preparations from healthy volunteers

The enzymatic inactivation of aztreonam by the faecal flora was investigated in 25 healthy human volunteers. Ten volunteers received aztreonam orally and 15 volunteers did not receive antibiotic treatment. Residual aztreonam and its inactivated open ring form were simultaneously detected by an HPLC-assay. Independent of aztreonam treatment, beta-lactamase activity was detected in the faecal flora of 20 volunteers. The inactivation of aztreonam by the faecal supernatants was inhibited by clavulanic acid.

Comparison of reversed-phase column materials for high-performance liquid chromatography of proteins

Nine reversed-phase materials with various bonded phases from different suppliers were studied for the separation of hydrophilic proteins with two solvent systems. Protein retention, resolution and recovery were not correlated with the nature of the hydrocarbonaceous ligand. Peak volumes increased with molecular weight, which led to broad, irregular peaks for the larger proteins on some columns. Four columns that performed equally well were selected for the purification of hydrophobic Sendai virus membrane proteins. In this case, more distinct differences were found between columns. Recovery of the membrane proteins strongly depended on the combination of column and solvent systems.

Size-exclusion high-performance liquid chromatography of Sendai virus membrane proteins in different detergents. A comparison of different columns

Four column packings for size-exclusion high-performance liquid chromatography (HPLC) of proteins with particle sizes from 3 to 13 micron were compared, using 0.1% sodium dodecyl sulphate in the solvent. Their suitability for the purification of hydrophobic membrane proteins was studied with Sendai virus proteins as a model. The calibration curves of the two 13-micron column packings were linear up to high molecular weights. In contrast to this, large proteins (greater than 100-150 kD) were eluted later than expected from the 3- and 6-micron packings. Peak capacities for proteins larger than 20 kD ranged from 4.7 to 5.5. Therefore, purification of complex mixtures of membrane proteins will often require rechromatography by a different mode of HPLC. Non-ionic detergents are suitable for further ion-exchange chromatography. The effect of addition of 0.1% of five non-ionic detergents (three gluco-methylalkanamide detergents, octylglucoside, and decyl-polyethyleneglycol-300) to the solvent was investigated and decyl-polyethyleneglycol-300 was found to be most suitable. Size-exclusion HPLC with this detergent resulted in the separation of micelles of three different sizes, of which the larger two contained exclusively the Sendai virus F protein.

Predicted membrane topology of the coronavirus protein E1

The structure of the envelope protein E1 of two coronaviruses, mouse hepatitis virus strain A59 and infectious bronchitis virus, was analyzed by applying several theoretical methods to their amino acid sequence. The results of these analyses combined with earlier data on the orientation and protease sensitivity of E1 assembled in microsomal membranes lead to a topological model. According to this model, the protein is anchored in the lipid bilayer by three successive membrane-spanning helices present in its N-terminal half whereas the C-terminal part is thought to be associated with the membrane surface; these interactions with the membrane protect almost the complete polypeptide against protease digestion. In addition, it is predicted that the insertion of E1 into the membrane occurs by the recognition of the internal transmembrane region(s) as a signal sequence.

Combined size-exclusion and reversed-phase high-performance liquid chromatography of a detergent extract of Sendai virus

Virus envelope proteins obtained by Triton X-100 extraction of Sendai virions were purified to a high degree by a combination of high-performance liquid chromatography (HPLC) methods. Size-exclusion HPLC on a TSK 4000 PW column with several concentrations of acetonitrile or ethanol-1-butanol in 0.1% hydrochloric acid as eluent was used as the first chromatographic step. Peak fractions were diluted in water and further fractionated on reversed-phase columns (TMS-250 or Vydac 218 TP). Size-exclusion HPLC with 45% acetonitrile in 0.1% hydrochloric acid, combined with reversed-phase HPLC on either column, was most suitable for obtaining highly purified F2 protein. Antibodies obtained after injection of this protein were reactive with the intact virus.

Isolation of detergent-extracted Sendai virus proteins by gel-filtration, ion-exchange and reversed-phase high-performance liquid chromatography and the effect on immunological activity

Virus envelope proteins were isolated from Triton X-100 extracts of purified Sendai virions by gel-filtration, ion-exchange and reversed-phase high-performance liquid chromatography (HPLC). The fusion protein F, the matrix protein M and the tetrameric and dimeric form of the HN protein were isolated by gel-filtration HPLC with a solvent containing 0.1% sodium dodecyl sulphate. HN and F were also isolated by ion-exchange HPLC with 0.1% Triton X-100 in the eluent. Reversed-phase HPLC was performed on a C1 column with acetonitrile as the organic solvent. Especially the F1 and F2 component of the fusion protein F were obtained in pure form. The immunological activity of the proteins after HPLC was determined with an enzyme-linked immunosorbent assay (ELISA). After gel-filtration and ion-exchange HPLC, proteins still reacted with antiserum to the intact virus while proteins purified by reversed-phase HPLC did not react.

Differences in antigenic properties of Fc-binding activity during infection with herpes simplex virus type 1

The antigenic properties of the Fc receptor induced by herpes simplex virus type 1 (HSV-1) were studied with anti-HSV F(ab')2 and pFc' from infected rabbits. It appeared that the HSV-induced Fc-binding receptor had different antigenic characteristics at different times after infection. The Fc receptor present early in the infection (0.5 hours), during the adsorption period, most probably is the result of a fusion event between the virus envelope and the infected cell. We found that this Fc receptor reacted with anti-HSV F(ab')2 and thus showed HSV-antigenic properties in such a way that binding of anti-HSV F(ab')2 prevented the binding of pFc' fragments. Later on in the infection (5 hours), the Fc-binding activity present on the surface of the infected cell is the result of newly synthesized and in the plasma membrane integrated polypeptides. The Fc-binding activity present on the cell surface of 5 hours infected cells could not be inhibited by anti-HSV F(ab')2 and did not interfere with the binding of pFc' to the Fc receptor.

Purification of detergent-extracted Sendai virus proteins by reversed-phase high-performance liquid chromatography

Sendai virus envelope proteins were isolated by reversed-phase high-performance liquid chromatography. The F (F1 and F2, connected by disulphide bonds), M and HN proteins were extracted from purified Sendai virions with Triton X-100. After removal of the detergent from the extract with Amberlite XAD-2 and reduction of the proteins, separation was performed on a small (10-nm) and on a larger (30-nm) pore size C18 column. Proteins were eluted with a gradient of an ethanol 1-butanol mixture in 12 mM hydrochloric acid. On the 10-nm pore size column, F2 was completely recovered in pure form, whereas the recoveries of the other proteins were low (5-25%). Similar results were obtained with the 30-nm pore size column, except for protein F1 of which the yield was higher (50%).