[Humanization of Murine Monoclonal anti-hTNF Antibody: The F10 Story].

Tumor necrosis factor (TNF) is a proinflammatory cytokine implicated in pathogenesis of multiple autoimmune and inflammatory diseases. Anti-TNF therapy has revolutionized the therapeutic paradigms of autoimmune diseases and became one of the most successful examples of the clinical use of monoclonal antibodies. Currently, anti-TNF therapy is used by millions of patients worldwide. At the moment, fully human anti-TNF antibody Adalimumab is the best-selling anti-cytokine drug in the world. Here, we present a story about a highly potent anti-TNF monoclonal antibody initially characterized more than 20 years ago and further developed into chimeric and humanized versions. We present comparative analysis of this antibody with Infliximab and Adalimumab.

Multiple-antigen immunization of chickens facilitates the generation of recombinant antibodies to autoantigens.

Antibody phage display is a powerful tool for the generation of monoclonal antibodies against virtually any given antigen. Chickens are phylogenetically more distant from humans compared to other laboratory animals, such as mice and rats. Therefore, the use of chickens is especially beneficial when generating recombinant antibodies against human autoantigens, which are often highly conserved among mammals. Another advantage of using chickens in antibody phage display is that the preparation of single chain variable fragment (scFv) antibody libraries is faster and easier compared to preparing such libraries from other species, as only two primer sets are needed for amplification of the chicken variable heavy chain (V(H)) and variable light chain (V(L)) genes. In the present study we explored the possibility to immunize chickens with antigen cocktails for the generation of recombinant antibody fragments directed to a range of human autoantigens. Two pairs of chickens were immunized with two cocktails of seven recombinant autoantigenic proteins, libraries were prepared and panned on the individual proteins. The polyclonal chicken sera reacted strongly with most of the antigens used for immunization. By creating and screening single-chain variable fragment antibody phage display libraries, recombinant monoclonal antibody fragments were isolated successfully against the autoantigens annexin XI, centromere protein B, heat shock protein B3, DNA topoisomerase I, histidyl tRNA synthetase, Ro52, Ro60, Rpp30 and U1A. In conclusion, the immunization of only four chickens with two distinct pools of a total of 14 autoantigenic proteins allowed the isolation of scFvs against nine of these antigens.

Recombinant anti-P protein autoantibodies isolated from a human autoimmune library: reactivity, specificity and epitope recognition.

The ribosomal P proteins are specific and important autoantigens in patients affected by systemic lupus erythematosus. In this study, we describe for the first time the selection and characterization of recombinant human monoclonal anti-P protein (auto)-antibody fragments from an autoimmune patient-derived phage display antibody library. The selected recombinant anti-P antibodies specifically recognize the P proteins in immunofluorescence assays on HEp-2 cells and in immunoblotting assays, and they immunoprecipitate the P proteins under native conditions. Using both anti-P-positive patient sera and the selected recombinant anti-P antibodies, the immunodominant epitope was determined and shown to be located at the C-terminal end of the P proteins (amino acids 111-115). Inhibition of in vitro protein translation demonstrated that interaction of the monoclonal patient-derived anti-P antibodies with their native epitope functionally inhibits the activity of the P proteins on the ribosome, confirming the notion that patient autoantibodies are often directed to the functional centre of their autoantigenic target.

Recombinant human antibodies specific for the Pfs48/45 protein of the malaria parasite Plasmodium falciparum.

We report the first construction of two combinatorial human phage display libraries derived from malaria-immune patients. Specific single-chain Fv fragments (scFv) against Pfs48/45, a gamete surface protein of the sexual stages of Plasmodium falciparum, were selected and analyzed extensively. The selected scFv reacted with the surface of extracellular sexual forms of the parasite and showed Pfs48/45 reactivity on immunoblot. The scFv inhibit binding of human malaria sera to native Pfs48/45 from gametocytes. Moreover, the scFv bind to target epitopes of Pfs48/45 exposed in natural infections. Sequence analysis of eight scFv clones specific for epitope III of Pfs48/45 revealed that these clones could be divided into one V(H) family-derived germ-line gene (V(H)1) and two V(L) family segments (V(L)2 and V(K)I).

Characterization of recombinant human autoantibody fragments directed toward the autoantigenic U1-70K protein.

The U1-70K protein is specifically bound to stemloop I of the U1 small nuclear RNA contained in the U1 small nuclear ribonucleoprotein complex (U1 snRNP), which is involved in the splicing of pre-mRNA. All components of the U1 snRNP complex, including the U1-70K protein, are important autoantigens in patients with systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD). Here we describe for the first time the selection and characterization of recombinant human anti-U1-70K single chain autoantibody fragments (anti-hU1-70K scFv) from autoimmune patient-derived phage display antibody libraries. All scFv specifically recognize parts of the hU1-70K protein and its apoptotic 40-kDa cleavage product. In Western blotting assays a number of scFv preferentially recognize the 40-kDa apoptotic cleavage fragment of the U1-70K protein, suggesting a possible involvement of this apoptotic cleavage product in the autoimmune response of patients. The germline gene usage of these recombinant autoantibodies was also determined. Using several U1-70K deletion and point mutants of both human (h) and Drosophila melanogaster (Dm) origin, it was established that the U1-70K epitope that is recognized by the anti-hU1-70K scFv is located within the RNA binding domain.

Analysis of autoimmune bone marrow by antibody-phage display: somatic mutations and third complementarity-determining region arginines in anti-DNA gamma and kappa V genes.

OBJECTIVE: To examine anti-double-stranded DNA (anti-dsDNA) IgG autoantibodies from the bone marrow of individuals with systemic lupus erythematosus (SLE). METHODS: A library of single-chain variable fragments (scFv) was constructed from SLE bone marrow complementary DNA of gamma, kappa, and lambda isotype by cloning into the pHENIX phagemid vector. The library was screened with dsDNA in solution, and 2 anti-DNA phage, DNA1 and DNA4, were isolated and their Ig V genes sequenced. Soluble scFv corresponding to DNA1 and DNA4, and their heavy (H)- and light (L)-chain recombinants, were prepared, purified, and analyzed for binding to DNA by enzyme-linked immunosorbent assay. RESULTS: DNA1 and DNA4 used different Ig H-chain (3-30 and 5-51, respectively) and L-chain (DPK15 and DPK22, respectively) V genes. The ratios of replacement mutations to silent mutations in DNA1 and DNA4 suggest that their V genes were selected for improved antigen binding in vivo. The recombinant between DNA4VH and DNA1VL showed the highest relative affinity for both single-stranded DNA and dsDNA. These 2 Ig subunits contained third complementarity-determining region arginines and had acquired the majority of replacement mutations. CONCLUSION: Anti-dsDNA IgG autoantibodies from the bone marrow of SLE patients exploit diverse V genes and cationic V-D-J and V-J junctions for DNA binding, and accumulate replacement mutations that enhance binding.

Cell death: a trigger of autoimmunity?

Systemic autoimmune diseases are characterized by the production of antibodies against a broad range of self-antigens. Recent evidence indicates that the majority of these autoantigens are modified in various ways during cell death. This has led to the hypothesis that the primary immune response in the development of autoimmunity is directed to components of the dying cell. In this article, we summarize data on the modification of autoantigens during cell death and the possible consequences of this for autoimmunity.

Caspase-dependent cleavage of nucleic acids.

Autoimmune diseases are frequently characterized by the presence of autoantibodies directed against nucleic acid-protein complexes present in the nucleus of the cell. The mechanisms by which these autoantigenic molecules escape immunological tolerance are largely unknown, although a number of recent observations suggest that modified self-proteins generated during apoptosis may play an important role in the development of autoimmunity. It has been hypothesized that the recognition of these modified self-proteins by the immune system may promote autoantibody production. While apoptosis is specifically characterized by posttranslational modification of proteins, recent findings also show that nucleic acids are modified. This review summarizes the specific cleavages of some of these key nucleic acids, i.e. chromosomal DNA, ribosomal RNA and small structural RNAs (U1 snRNA, Y RNA), in apoptotic cells.

Specific detection of myeloma plasma cells using anti-idiotypic single chain antibody fragments selected from a phage display library.

Bone marrow plasma cells constitute the bulk of malignant cells in multiple myeloma patients. B-lymphocytes having immunoglobulin heavy chain gene rearrangements identical to those of the malignant clone (clonally related B-lymphocytes) may function as malignant plasma cell precursors. We and others proposed the use of anti-idiotypic antibodies to isolate and study clonally related B-lymphocytes. This strategy failed until now because anti-idiotypic antibodies raised by conventional hybridoma techniques proved to react frequently with epitopes shared by different idiotypes. Recently, we succeeded in selecting specific single chain Fv antibodies from phage libraries. To select single chain Fv bearing phages specifically directed against the immunoglobulin idiotype expressed by myeloma tumor cells we panned a semisynthetic phage library against purified myeloma paraprotein Fab fragments. The selection was performed in the presence of soluble polyclonal immunoglobulin as a competitor. Three independent selections for three myeloma patients yielded 10-26 clones. Between two and seven of the selected clones were reactive with patient Fab and not with polyclonal immunoglobulin in enzyme-linked immunosorbent assays. Five out of six anti-idiotypic single chain Fvs were able to specifically stain fixed monoclonal plasma cells in myeloma bone marrow. Idiotype specificity of these single chain Fvs was confirmed by flow cytometry since they did not react with monoclonal plasma cells of other patients, a panel of nine myeloma cell lines, isolated polyclonal bone marrow plasma cells and cultured B-lymphocytes. Using these anti-idiotypic reagents we were able to detect 25 myeloma plasma cells in a background of 50000 immunoglobulin isotype-matched cells of the myeloma cell line UM-1 or 50000 donor bone marrow cells (sensitivity 0.05%). This paper shows that highly specific anti-idiotypic single chain Fv antibody fragments selected from a phage display library can be used to detect rare idiotypic cells in patient samples.

Human monoclonal autoantibody fragments from combinatorial antibody libraries directed to the U1snRNP associated U1C protein; epitope mapping, immunolocalization and V-gene usage.

To study the localization and function of the U1snRNP associated U1C protein, so far only human sera from systemic lupus erythematosus (SLE) overlap syndrome patients have been used. Here we report for the first time the isolation of human monoclonal anti-UIC autoantibody fragments from IgG derived combinatorial and semi-synthetic human antibody libraries. Two classes of human monoclonal anti-UIC (auto)antibodies were found: specific anti-U1C autoantibodies, recognizing U1C only, and cross-reactive antibodies which also react with U1A and Sm-B/B'proteins. The heavy chains (V(H)genes) of all five antibodies from the semi-synthetic libraries and two of the three U1C-specific patient derived autoantibody fragments are encoded by V(H)3 genes, in which V(H) 3-30 (DP-49) was overrepresented. The heavy chain of the two cross-reactive autoantibodies are derived from the 3-07 (DP-54) gene. Three epitope regions on the U1C protein are targeted by these antibodies. (1) Four U1C specific antibodies recognize an N-terminal region of U1C in which amino acids 30-63 are essential for recognition, (2) two antibodies recognize only the complete U1C protein, and (3) two cross-reactive and one U1C specific antibody recognize the C-terminal domain in which amino acids 98-126 are critical for recognition. The two cross-reactive antibodies (K 11 and K 15) recognize the proline-rich region of the U1C protein (amino acids 98 126) and cross-react with proline-rich regions in Sm-B/B' (amino acids 163-184) and U1A (amino acids 187-204). All 10 antibody fragments are able to immunoprecipitate the native U1snRNP particle. The two cross-reactive antibodies immunoprecipitate the other Sm containing snRNPs as well. Using confocal immunofluorescence microscopy we could show that the major part of the U1C protein is localized within the coiled body structure.

Modified mRNA rescue of maternal CK1/8 mRNA depletion in Xenopus oocytes.

This work addresses two issues, the use of antisense oligodeoxynucleotides to deplete specific mRNAs in Xenopus oocytes to analyze their functions during development and the role of cytokeratin filaments in cells of the early Xenopus embryo. We have shown previously that depletion of cytokeratin CK1/8 mRNA causes defects in the early embryo. In this study, we show that the oligos, modified with phosphoramidate linkages to improve stability, are capable of degrading exogenous mRNA up to 27 hours after injection in the oocyte. For this reason, the phenotype could not be rescued by injection of a synthetic CK1/8 mRNA. However, modification of the synthetic CK1/8 mRNA, which prevents annealing of the antisense oligonucleotide used for depleting the endogenous CK1/8 mRNA, did result in the rescue of the CK1/8 depletion phenotype. These results demonstrate that the phenotype observed after depletion of the CK1/8 mRNA is truly caused by the lack of CK1/8 protein. Injection of the closely related type II cytokeratin (CK55) did not result in the same level of rescue of the CK1/8 depletion phenotype, suggesting that structurally similar members of the cytokeratin family, expressed at different stages of development, cannot substitute for each other in the early embryo.

Transgenic mice carrying chimeric or mutated type III intermediate filament (IF) genes.

Mice carrying chimeric, truncated or mutated genes encoding intermediate filament (IF) proteins type III do not show any detectable severe pathology. However, upon (over)expression of the transgene in the eye lens all animals develop lens opacification (cataract). At the cellular level the loss of visual acuity is preceded by interference with the terminal differentiation of lens fibre cells, plasma membrane damage, distorted assembly of the IF cytoskeleton and perturbation of the cytoskeleton-membrane complex. The degree of expression is paralleled by the extent of the damages.

Muscle-specific expression of a dominant negative desmin mutant in transgenic mice.

To extend our knowledge of the functions of desmin and vimentin intermediate filaments in the developing organism, a construct encoding a truncated desmin subunit driven by the desmin promoter (pDDV), was introduced into the murine germ line. The resulting mutant desmin subunit was assembly-incompetent and capable of disrupting both preexisting desmin and vimentin filaments in a dominant negative fashion in transfected C2C12 muscle cells and in transgenic mouse muscle tissue. Expression of the pDDV was tissue-specific in transgenic mice. High level expression of pDDV occurred in a small percentage of desmin-containing muscle cells. Immunohistochemical staining of muscle tissue showed a diffuse desmin pattern instead of the dots and clumps into which mutant desmin typically accumulates in undifferentiated C2C12 muscle cells in tissue culture. Disruption of the endogenous desmin filaments in Sartorius muscle results in ultrastructural abnormalities.

Disruption of vimentin intermediate filaments in transgenic mice by expression of a dominant negative mutant desmin subunit.

To investigate putative functions of vimentin intermediate filaments in the context of intact tissues and the developing organism, a construct (pVDV), driven by the vimentin promoter and encoding a truncated desmin subunit, was introduced into the murine germ line. The mutant desmin was assembly-incompetent and capable of disrupting preexisting vimentin filaments in a dominant negative fashion, both in transgenic mouse tissues and in fibroblast cultures derived from these mice. Mutant desmin expression strongly enhanced vimentin turnover. In tissues of some transgenic mouse lines, high level expression of pVDV occurred in 10 to 40% of vimentin-containing cells and, surprisingly, in 1 to 10% of the skeletal and tongue muscle cells. Immunohistochemical staining of muscle tissue showed a diffuse staining pattern instead of the punctated aggregates into which mutant desmin typically accumulates in other cell types. The overexpression of pVDV and the concomitant disruption of the endogenous vimentin filament network and enhanced vimentin turnover in a significant percentage of cells did not cause detectable developmental abnormalities.

Regulation of vimentin expression in cultured epithelial cells.

Most cell types start expressing vimentin when brought into tissue culture. Using both vimentin-expressing (HeLa) and vimentin-negative (MCF-7) epithelial cell lines, we have identified the cis-regulatory DNA elements involved in this process. Sequences located 1.1-0.6 kb upstream of the vimentin transcription-initiation site strongly enhance expression in HeLa cells, but are silenced in MCF-7 cells. Other regulatory elements in the vimentin promoter (an enhancer 3.2-2.6 kb upstream and a minimal promoter region including the CAAT-box) are potentially active in both cell types, but are silenced by the 0.5-kb fragment in MCF-7 cells. Deletion of this fragment restores transcriptional activity of a transfected vimentin promoter. Our data indicate that a double AP 1/jun-binding site present in the 0.5-kb fragment mediates the induction of vimentin expression in cultured epithelial cells, while silencing sequences located within the same fragment are responsible for the absence of vimentin expression in MCF-7 cells. In contrast to MCF-7 cells, a transfected vimentin promoter and gene are transcriptionally active in the vimentin-negative epithelial cell line T24. Transfection studies show that type-III-intermediate-filament expression is not impaired at any level in these cells. Upon transfection and expression of a desmin construct in T24 cells not only desmin, but also vimentin was detected. Both proteins assembled into intermediate filaments. This induction of vimentin expression appeared to be regulated at the post-transcriptional level.

Biochemical and structural aspects of transiently and stably expressed mutant desmin in vimentin-free and vimentin-containing cells.

Using immunoelectron microscopy it is demonstrated that desmin subunits missing their complete carboxy-terminal domain are incapable of homopolymeric filament formation in vivo. Furthermore it is shown that, in vimentin-containing cells, desmin integrates into preexisting vimentin filaments resulting in desmin/vimentin heteropolymers. Removal of the amino-terminal or both nonhelical end domains of desmin increases Triton X-100 solubility of the mutant desmin subunits. Expression of desmin mutants containing deletions in the C-terminal part of the rod in vimentin-free cells results in an increase of the Triton X-100 solubility too. In contrast, if expressed in vimentin-containing cells, these mutant subunits remain in the Triton X-100 insoluble fraction. Deletion of the nonhelical carboxy-terminal domain only has no effect on solubility. In vimentin-free cells, stably expressed desmin subunits missing their amino-terminal domains display a slightly higher turnover rate compared to wild-type desmin. Transiently expressed desmin subunits missing 18 or more carboxy-terminal residues of the rod domain are rapidly degraded in vimentin-free cells. In vimentin-containing cells, turnover rates were much less pronounced. Finally, by using site-directed mutagenesis, we were able to map specific residues important for de novo filament assembly within the amino-terminal domain and in the conserved part at the C-terminus of the alpha-helical domain.

Assembly of carboxy-terminally deleted desmin in vimentin-free cells.

Using a vimentin-free expression system we were able to demonstrate that the carboxy terminus of desmin is necessary for filament assembly in the living cell. Desmin subunits missing only 4 carboxy-terminal residues of their rod domain are incapable of homopolymeric filament assembly. Moreover, even single amino acid substitutions in the conserved carboxy-terminal part of the rod domain prevent desmin subunits from homopolymeric filament assembly. Desmin subunits missing 18 or more carboxy-terminal residues of their rod domain (including the complete conserved carboxy-terminal region) are unstable in cells devoid of intact type III intermediate filaments (IFs). Interaction with an intact type III IF, however, stabilizes these mutated desmin subunits. Expression of a desmin subunit missing both its non-helical end domains in vimentin-containing cells disrupts the endogenous vimentin network completely.

Assembly of amino-terminally deleted desmin in vimentin-free cells.

To study the role of the amino-terminal domain of the desmin subunit in intermediate filament (IF) formation, several deletions in the sequence encoding this domain were made. The deleted hamster desmin genes were fused to the RSV promoter. Expression of such constructs in vimentin-free MCF-7 cells as well as in vimentin-containing HeLa cells, resulted in the synthesis of mutant proteins of the expected size. Single- and double-label immunofluorescence assays of transfected cells showed that in the absence of vimentin, desmin subunits missing amino acids 4-13 are still capable of filament formation, although in addition to filaments large numbers of desmin dots are present. Mutant desmin subunits missing larger portions of their amino terminus cannot form filaments on their own. It may be concluded that the amino-terminal region comprising amino acids 7-17 contains residues indispensable for desmin filament formation in vivo. Furthermore it was shown that the endogenous vimentin IF network in HeLa cells masks the effects of mutant desmin on IF assembly. Intact and mutant desmin colocalized completely with endogenous vimentin in HeLa cells. Surprisingly, in these cells endogenous keratin also seemed to colocalize with endogenous vimentin, even if the endogenous vimentin filaments were disturbed after expression of some of the mutant desmin proteins. In MCF-7 cells some overlap between endogenous keratin and intact exogenous desmin filaments was also observed, but mutant desmin proteins did not affect the keratin IF structures. In the absence of vimentin networks (MCF-7 cells), the initiation of desmin filament formation seems to start on the preexisting keratin filaments. However, in the presence of vimentin (HeLa cells) a gradual integration of desmin in the preexisting vimentin filaments apparently takes place.