Expression of human immunoglobulin E epsilon chain cDNA in E. coli

Analysis of IgE antibodies from a patient with atopic dermatitis: biased V gene usage and evidence for polyreactive IgE heavy chain complementarity-determining region 3

To better understand V gene usage, specificity, and clonal origins of IgE Abs in allergic reactions, we have constructed a combinatorial Ab library from the mRNA of an adult patient with atopic dermatitis. Sequence analysis of random clones revealed that 33% of clones used the IGHV6-1 H chain V gene segment, the only member of the V(H)6 gene family. IGHV6-1 is rarely used in the expressed adult repertoire; however, it is associated with fetal derived Abs. Features of the V(H)6 rearrangements included short complementarity-determining region 3, frequent use of IGHD7-27 D gene, and little nucleotide addition at the D-J junction. There was also a low level of mutation compared with V(H)1, V(H)3, and V(H)4 rearrangements. The library was expressed as phage-Fab fusions, and specific phage selected by panning on the egg allergen ovomucoid. Upon expression as soluble IgE Fabs, 12 clones demonstrated binding to ovomucoid, skim milk, and BSA by ELISA. Nucleotide sequencing demonstrated that the IGHV6-1 V gene segment encoded each of the 12 multiply reactive IgE Fabs. A cyclic peptide was designed from the complementarity-determining region 3 of several of these clones. The cyclic peptide bound both self and nonself Ags, including ovomucoid, human IgG, tetanus toxoid, and human and bovine von Willebrand factor. These results suggest that some IgE Abs may bind more than one Ag, which would have important implications for understanding the multiple sensitivities seen in conditions such as atopic dermatitis.

Construction of a combinatorial IgE library from an allergic patient. Isolation and characterization of human IgE Fabs with specificity for the major timothy grass pollen allergen, Phl p 5

To characterize human IgE antibodies with specificity for a major allergen at the molecular level, we have constructed an IgE combinatorial library from a grass pollen allergic patient. cDNAs coding for IgE heavy chain fragments and for light chains were reverse-transcribed and polymerase chain reaction-amplified from RNA of peripheral blood lymphocytes and randomly combined in plasmid pComb3H to yield a combinatorial library of 5 x 10(7) primary clones. IgE Fabs with specificity for Phl p 5, a major timothy grass pollen allergen, were isolated by panning. Sequence analysis showed that the 4 of the Fabs used the same heavy chain fragments which had combined with different kappa light chains. Soluble recombinant IgE Fabs were purified by affinity chromatography to Phl p 5 and, like natural IgE antibodies, cross-reacted with group 5 allergens from different grass species. The described approach should facilitate studies on the molecular interaction between IgE antibodies and allergens and encourages the consideration of specific IgE Fabs that are capable of interfering with allergen-IgE binding as potential therapeutic tools.

Antibody engineering using Escherichia coli as host

The expression of immunoglobulin fragments with antigen binding activities in E. coli is now routinely possible. Using such expression systems, Fv, Fab, and scFv fragments and single VH domains can be produced as secreted proteins in yields of the order of milligrams per liter. Moreover, expression systems are being rapidly developed for the production of antibody scFv or Fab fragments by repertoire cloning followed by selection. Diverse repertoires of genes encoding VH and VL domains can be isolated by the PCR and cloned for expression using these systems, which allow the selection of recombinants that produce fragments with the desired antigen binding specificities. This technology is rapidly evolving and, coupled with the development of systems for the random mutagenesis and selection of higher-affinity antibody fragments, could, in the longer term, provide an alternative rapid route to hybridoma technology.

Protein engineering of antibodies

This article reviews the technical advances in antibody engineering and the clinical applications of these molecules. Recombinant DNA technology facilitates the construction and expression of engineered antibodies. These novel molecules are designed to meet specific applications. Although genomic and cDNA cloning have been used widely in the past to isolate the relevant antibody V domains, at present, the PCR-based cloning is the preferred system. Bacterial and mammalian expression systems are used commonly for the production of antibodies, antibody fragments, and antibody fusion proteins. A range of chimeric antibodies with murine V domains joined to C regions from human and other species have been produced and found to exhibit the expected binding characteristics and effector functions. Humanized antibodies have been developed to minimize the HAMA response, and bifunctional immunoglobulins are being used in tumor therapy and diagnosis. Single chain antibodies and fusion proteins with antibody specificities jointed to nonimmunoglobulin sequences provide a source of antibody-like molecules with novel properties. The potential applications of minimal recognition units and antigenized antibodies are described. Combinatorial libraries produced in bacteriophage present an alternative to hybridomas for the production of antibodies with the desired antigen binding specificities. Future developments in this field are discussed also.

Thyroid hormone binding protein contains glycosylation site binding protein activity

Several lines of evidence provided by other workers indicate that within the same species thyroid hormone binding protein, the beta-subunit of prolyl hydroxylase, and protein disulfide isomerase are the same protein. We sought to determine if glycosylation site binding protein, a lumenal protein of the endoplasmic reticulum, also has the same primary structure. To accomplish this the level of glycosylation site binding protein (GSBP) activity, measured by photolabeling with a glycosylation site peptide probe, was carried out in preparations of 3T3 cells and in E. coli transformed with human thyroid hormone binding protein cDNA. The results strongly support the idea that GSBP is identical to these other lumenal proteins of the endoplasmic reticulum.

Bacterial expression of immunoglobulin VH proteins

A bacterial expression system in Escherichia coli has been developed that produces as much as 10 mg/l of culture of the VH protein associated with monoclonal antibodies specific for the 5-dimethylaminonaphthalene-2-sulfonyl (Dns) group. This system has been applied to the expression of the VH genes derived from a low-affinity, IgM-producing hybridoma and from a high-affinity, IgG-producing cell line. The plasmid vectors (contributed by Dr William F. Studier) utilize a T7 expression cassette whose activity is initiated by infection with a lambda phage derivative carrying the T7 RNA polymerase gene. The VH proteins were extracted from the bacterial pellet in 8 M urea and purified by chromatography in 8 M urea. Recombinants with the homologous light (L) chains were prepared to yield VHL molecules. These were used to measure intrinsic affinity for Dns-lysine by resonance energy transfer. The association constants were 7 x 10(6) M-1 and 7 x 10(9) M-1 for the low- and high-affinity systems, respectively. These values are not significantly different from those observed with monoclonal antibodies secreted from the corresponding cell lines. This system lends itself to the quantitative evaluation of the binding properties of the VH protein itself as well as the modulation of affinity by site-directed mutagenesis.

Synthesis of hepatitis B virus e antigen in E. coli

Hepatitis B virus core antigen (HBcAg) gene was deleted at some unique restriction enzyme sites, or at random, and inserted into the expression plasmids of E. coli which had the tryptophan promoter. E. coli transformants with the plasmids, synthesized materials with many kinds of antigenicity of HBcAg, HBeAg, or both HBcAg and HBeAg. HBeAg-specific material smaller than native HBeAg was produced in a stable condition.

An enzyme immunoassay for human lymphotoxin

A highly sensitive and specific enzyme immunoassay (EIA) for human lymphotoxin (hLT) has been developed. The assay is based upon a sandwich system employing two kinds of anti-hLT antibodies with neutralizing activity. One of them was mouse monoclonal antibody raised against Escherichia coli-derived recombinant hLT with a deletion of 20 amino-terminal amino acids and used as labelled antibody. The other was rabbit antibody raised against the carboxyl-terminal portion of hLT and used as solid-phase antibody. The EIA employing such a combination was able to detect less than 50 pg/ml of hLT, showing that this method was approximately 5-10 times higher sensitivity than the conventional bioassay employing L929 cell-lysis. The mean recovery of hLT added to serum specimens was 101% and the coefficients of variation were 3.3-7.8% (intra-assay) and 2.9-17.2% (interassay). There was a good correlation between the present EIA and the bioassay (r = 0.93).

Bispecific antibody-producing hybrid hybridoma and its use in one-step immunoassays for human lymphotoxin

A hybrid hybridoma cell line secreting a bispecific monoclonal antibody (MAb) was constructed by fusing horseradish peroxidase (HRPO)-immunized mouse splenocytes with previously established mouse hybridomas secreting anti-human lymphotoxin (hLT). This cell line was grown in ascitic fluid in mice to obtain large quantities of hybrid MAbs and a bispecific antibody, reacting with both HRPO and hLT, was separated from the monospecific antibody or other inactive immunoglobulin populations by hydroxylapatite chromatography. Sodium dodecylsulfate-polyacrylamide gel electrophoresis demonstrated that the bispecific antibody molecule contained two different types of heavy and light chains of both anti-HRPO and anti-hLT origin. The bispecific antibody was used to establish one-step enzyme immunoassays (EIAs) employing competitive and sandwich systems. The simple sandwich EIA was able to detect 1-100 U/ml of hLT and there was good correlation (r = 0.96) between hLT concentrations measured by the one-step EIA and a bioassay using L929 cell-lysis.

Purification and characterization of a recombinant human IgE Fc epsilon fragment lacking the C4 domain

Complementary DNA of human IgE Fc epsilon fragment (residues 226-480) lacking the C epsilon 4 domain was expressed in Escherichia coli and the product was purified by immunoaffinity chromatography on a monoclonal antibody (E12 0.02)-Affi-Gel 10 column. About 1.8 mg of an apparent dimer and 5.9 mg of a monomer were obtained from 65 g E. coli cells with 9.3% recovery. The purified products were found to lack more than half of the COOH-terminal portion of the C epsilon 3 domain. The apparent dimer showed high immunological specific activity (3.6 x 10(6) U/mg protein) comparable to that of natural human IgE when measured by commercial human IgE determination kits.

Expression of cDNA encoding human basic fibroblast growth factor in E. coli

The cDNA encoding human basic fibroblast growth factor was expressed in E. coli under the control of trp promoter. Bacterially synthesized hbFGF was highly purified using a heparin affinity HPLC column. By this chromatography, hbFGF was eluted as four distinct forms, which were indistinguishable by SDS polyacrylamide gel electrophoresis, amino acid composition, and partial terminal sequence analysis. These molecules stimulated the growth of fibroblasts and endothelial cells although their specific activities varied. The angiogenesis activity of these molecules was also confirmed.

Biological properties of a recombinant human immunoglobulin epsilon-chain fragment

A recombinant human immunoglobulin epsilon-chain gene expression product (rFc epsilon) was compared with a human E myeloma protein in the affinity for epsilon-chain Fc fragment receptors (Fc epsilon R) on cultured human basophils. The association-dissociation kinetics of the rFc epsilon-Fc epsilon R interaction are indistinguishable from that of E myeloma protein, indicating that rFc epsilon and IgE have identical affinity for the receptors. The recombinant gene product sensitizes cultured basophils for anti-IgE-induced histamine release. A dose-response curve of histamine release indicates that the gene product is equally efficient in transducing the signal for degranulation as the natural IgE. Both the rFc epsilon and IgE lost the affinity for Fc epsilon R by heating at 56 degrees C. Upon renaturation by passage through a solution of 6 M guanidine hydrochloride, rFc epsilon recovered both the affinity for Fc epsilon R and the original CD spectra. On the other hand, renaturation of heat-denatured IgE largely restored optical activity above 250 nm but restored neither the affinity for Fc epsilon R nor the CD spectrum below 220 nm. The results suggest that either the amino acid sequence or the carbohydrate present in the myeloma protein, but not the rFc epsilon, may interfere with refolding of the receptor-binding structures.

A hybrid protein between IFN-gamma and IL-2

The complementary DNAs encoding human interferon-gamma (IFN-gamma) and human interleukin-2 (IL-2), two different proteins involved in the same immune system, were fused to code a hybrid protein, which was expressed in E. coli to investigate the interactions of these two proteins at the molecular level. Through immunoprecipitation analysis, this protein was revealed to be of about 31 kDa, which was expected from nucleotide sequencing, and to have the antigenicities of both IFN-gamma and IL-2. The extract from bacteria expressing this hybrid protein showed at least two biological activities: an antiviral activity derived from IFN-gamma and the ability to support the growth of natural killer (NK) cells derived from IL-2. Comparing the enhancement of NK cell activity of this hybrid protein with IFN-gamma and IL-2, this hybrid protein appears to conserve each activity almost completely without diminishing the other.

cDNA of the immunoglobulin kappa chain of an Epstein-Barr virus-transformed human lymphoid cell line: partial sequence determination and bacterial expression

We report the isolation, nucleotide sequence determination, and bacterial expression of a partial cDNA for the immunoglobulin kappa chain from the Epstein-Barr virus-transformed human lymphoid cell line GM131. The cDNA, cloned in pBR322 by use of oligo(dG) X oligo(dC) tails, yields two Pst I fragments of 250 and 600 base pairs (bp). Various restriction enzyme fragments of the cDNA were subcloned in the vectors M13 mp10 and M13 mp11 for sequence analysis. As a result of instability of the 250-bp M13 subclones, the base sequence of the 250-bp Pst I fragment could not be determined. The 600-bp Pst I fragment contains coding sequences for part of the variable (V) region (residues 78-95) and all of the joining (J) (residues 96-108) and constant (C) regions (residues 109-212) and extends 148 bp into the 3' flanking region. Although the C- and 3'-flanking-region sequences are identical to germ-line sequences, the J-region sequence does not correspond to any of the five human germ-line J regions. The sequence is most similar to that of J4, with three base changes resulting in one silent mutation and two amino acid substitutions, at residues 103 (Lys----Tyr) and 106 (Ile---Met). The silent mutation appears to be the result of RNA splicing between the J and the C regions. The V-region sequence differs from published V-region germ-line sequences at several codons and from the more common amino acid sequences at two positions, residues 91 and 93. At these positions, histidine residues are found in place of the more common tyrosine and serine, respectively. None of the four amino acid substitutions observed for the GM131 kappa-chain are unique, suggesting that the changes, which most likely contribute to antigenic specificity, are compatible with antibody structure and function. The 600-bp Pst I fragment was subcloned in two prokaryotic expression vectors, pATH11 and pUC8. In both instances, a kappa-chain fusion protein detectable by immunoblotting was produced.

Transfectomas provide novel chimeric antibodies

Methods have been developed to transfect immunoglobulin genes into lymphoid cells. The transfected genes are faithfully expressed, and assembly can occur both between the transfected and endogenous chains and between two transfected chains. Gene transfection can be used to reconstitute immunoglobulin molecules and to produce novel immunoglobulin molecules. These novel molecules can represent unique combinations of heavy and light chains; alternatively, by means of recombinant DNA technology, genes can be assembled in vitro, transfected, and expressed. The end products of such manipulations include chimeric molecules with variable regions joined to different isotypic constant regions; this is possible both within and between species. It is also possible to synthesize altered immunoglobulin molecules, as well as molecules having immunoglobulin sequences fused with nonimmunoglobulin sequences (for example, enzyme sequences).

Establishment of hybridomas secreting monoclonal antibodies against C epsilon 2 and C epsilon 4 domains of human IgE

Three kinds of hybridomas secreting monoclonal antibodies (MAbs) against the epsilon chain of human IgE were constructed by somatic cell hybridization between mouse myeloma P3U1 cells and spleen cells from BALB/c mice immunized with human IgE purified from the culture supernatant of U-266 cells. These MAbs were used effectively for the purification and determination of human IgE. The recognition site in the IgE molecule of each antibody was examined by using various epsilon chain fragment peptides produced in Escherichia coli. From these experiments, it was suggested that one recognized C epsilon 2 and the second C epsilon 4. The third did not recognize the C epsilon 1-C epsilon 4 domains of the recombinant epsilon chain from E. coli, although it bound to the epsilon chain of natural human IgE.

Expression of a biologically active fragment of human IgE epsilon chain in Escherichia coli

cDNA corresponding to human IgE heavy (epsilon) chain mRNA was cloned from human IgE-secreting myeloma U266 cells. Partial nucleotide sequence analysis demonstrated that the cloned cDNA contained the coding region for about two-thirds of the CH2 and all of the CH3 and CH4 domains as well as the 3'-untranslated region. This epsilon cDNA was inserted into expression vector pUC7 and expression of an epsilon-chain fragment in Escherichia coli was demonstrated by protein blot analysis using 125I-labeled goat anti-human IgE as probe. The expression product was purified on a column of goat anti-human IgE-conjugated Sepharose 4B and the polypeptide was found to retain binding activity to human basophils.

Assembly of functional antibodies from immunoglobulin heavy and light chains synthesised in E. coli

Genes for a murine mu heavy chain and a lambda light chain immunoglobulin have been inserted into bacterial expression plasmids containing the Escherichia coli trp promoter and ribosome binding site. Induction of transcription from the trp promoter results in accumulation of both light and heavy chain polypeptides in appropriate host strains. Both proteins were found as insoluble products. Following extraction and purification of the immunoglobulin containing fractions, antigen binding activity was recovered. The activity demonstrates essentially the same properties as the antibody from the hybridoma from which the genes were cloned.

Properties of a human immunoglobulin epsilon-chain fragment synthesized in Escherichia coli

A fragment of the cloned gene for the human myeloma ND epsilon chain, coding for the second, third, and fourth domains of the immunoglobulin, has been coupled to the tryptophan control region of an expression plasmid and subcloned in Escherichia coli. Induction of gene expression results in the synthesis of the expected, antigenically active polypeptide of Mr 40,000, which constitutes 18% of total bacterial protein and yields 55 mg/liter of culture. The immunoglobulin, which is aggregated and packed into large inclusion bodies within the bacterial cell, can be dissolved by denaturing solvents and purified by affinity chromatography using anti-IgE Sepharose. Reduced monomeric chains assemble spontaneously into dimers. On assay to measure the inhibition of binding of 125I-labeled human E myeloma protein to Fc epsilon receptors on cultured human basophils, the cloned gene product exhibited 20% of the activity of the native protein.