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Biomedical subjects

A D Griffiths

Publications and source records attributed to A D Griffiths.

At least 19 recordsLinked to original sources
PubMed1994

Isolation of high affinity human antibodies directly from large synthetic repertoires.

Antibody fragments of moderate affinity (approximately microM) can be isolated from repertoires of approximately 10(8) immunoglobulin genes by phage display and rounds of selection with antigen, and the affinities improved by further rounds of mutation and selection. Here, as an alternative strategy, we attempted to isolate high affinity human antibodies directly from large repertoires. We first created highly diverse repertoires of heavy and light chains entirely in vitro from a bank of human V gene segments and then, by recombination of the repertoires in bacteria, generated a large (close to 6.5 x 10(10)) synthetic repertoire of Fab fragments displayed on filamentous phage. From this repertoire we isolated Fab fragments which bound to a range of different antigens and haptens, and with affinities comparable with those of antibodies from a secondary immune response in mice (up to 4 nM). Although the VH-26 (DP-47) segment was the most commonly used segment in both artificial and natural repertoires, there were also major differences in the pattern of segment usage. Such comparisons may help dissect the contributions of biological mechanisms and structural features governing V gene usage in vivo.

Amino Acid Sequence↗
PubMed1994

In vitro assembly of repertoires of antibody chains on the surface of phage by renaturation.

Antibodies can be made from repertoires of associated heavy and light chains displayed on the surface of bacteriophage, and are readily diversified by random point mutation or by chain shuffling. To make extensive variations around the "core" antigen binding contacts of a crystallographically solved mouse antibody NQ10/12.5 (gamma l, kappa), the NQ10 light chain was assembled in vitro with a repertoire of about 10(7) human heavy chains displayed on the surface of phage, and selected by binding to hapten. An antibody with a much improved affinity was isolated from the repertoire (K(a) = 10(9) M-1 compared with 10(8) M-1 for NQ10). The sequence of the human heavy chain (VH-IL) was highly related to NQ10. It conserved the same folds for the H1, H2 and H3 loops, six of the seven contact residues for hapten, and also a phOx binding motif (Asp-X-Gly-X-X) in the H3 loop. It appears that the new heavy chain partners for the NQ10 light chain often retain many critical antigen binding features found in the NQ10 heavy chain.

Amino Acid Sequence↗
PubMed1994

Making antibodies by phage display technology.

Antibody fragments of predetermined binding specificity have recently been constructed from repertoires of antibody V genes, bypassing hybridoma technology and even immunization. The V gene repertoires are harvested from populations of lymphocytes, or assembled in vitro, and cloned for display of associated heavy and light chain variable domains on the surface of filamentous bacteriophage. Rare phage are selected from the repertoire by binding to antigen; soluble antibody fragments are expressed from infected bacteria; and the affinity of binding of selected antibodies is improved by mutation. The process mimics immune selection, and antibodies with many different binding specificities have been isolated from the same phage repertoire. Thus human antibody fragments have been isolated with specificities against both foreign and self antigens, including haptens, carbohydrates, secreted and cell surface proteins, viral coat proteins, and intracellular antigens from the lumen of the endoplasmic reticulum and the nucleus. Such antibodies have potential as reagents for research and in therapy.

Animals↗
PubMed1993

Human anti-self antibodies with high specificity from phage display libraries.

Recently we demonstrated that human antibody fragments with binding activities against foreign antigens can be isolated from repertoires of rearranged V-genes derived from the mRNA of peripheral blood lymphocytes (PBLs) from unimmunized humans. The heavy and light chain V-genes were shuffled at random and cloned for display as single-chain Fv (scFv) fragments on the surface of filamentous phage, and the fragments selected by binding of the phage to antigen. Here we show that from the same phage library we can make scFv fragments encoded by both unmutated and mutated V-genes, with high specificities of binding to human self-antigens. Several of the affinity purified scFv fragments were shown to be a mixture of monomers and dimers in solution by FPLC gel filtration and the binding kinetics of the dimers were determined using surface plasmon resonance (k(on) = 10(5)-10(6) M-1s-1, k(off) = 10(-2)s-1 and Ka = 10(7) M-1). The kinetics of association are typical of known Ab-protein interactions, but the kinetics of dissociation are relatively fast. For therapeutic application, the binding affinities of such antibodies could be improved in vitro by mutation and selection for slower dissociation kinetics.

Amino Acid Sequence↗
PubMed1992

By-passing immunization: building high affinity human antibodies by chain shuffling.

Diverse antibody libraries can be displayed on the surface of filamentous bacteriophage, and selected by panning of the phage with antigen. This allows human antibodies to be made directly in vitro without prior immunization, thus mimicking the primary immune response. Here we have improved the affinity of one such "primary" antibody by sequentially replacing the heavy and light chain variable (V) region genes with repertoires of V-genes (chain shuffling) obtained from unimmunized donors. For a human phage antibody for the hapten 2-phenyloxazol-5-one (phOx) (Kd = 3.2 x 10(-7) M), we shuffled the light chains and isolated an antibody with a 20 fold improved affinity. By shuffling the first two hypervariable loops of the heavy chain, we isolated an antibody with a further 15-fold improved affinity. The reshuffled antibody differed in five of the six hypervariable loops from the original antibody and the affinity for phOx (Kd = 1.1 x 10(-9) M) was comparable to that of mouse hybridomas from the tertiary immune response. Reshuffling offers an alternative to random point mutation for affinity maturation of human antibodies in vitro.

Amino Acid Sequence↗
PubMed1991

By-passing immunization. Human antibodies from V-gene libraries displayed on phage.

We have mimicked features of immune selection to make human antibodies in bacteria. Diverse libraries of immunoglobulin heavy (VH) and light (V kappa and V lambda) chain variable (V) genes were prepared from peripheral blood lymphocytes (PBLs) of unimmunized donors by polymerase chain reaction (PCR) amplification. Genes encoding single chain Fv fragments were made by randomly combining heavy and light chain V-genes using PCR, and the combinatorial library (greater than 10(7) members) cloned for display on the surface of a phage. Rare phage with "antigen-binding" activities were selected by four rounds of growth and panning with "antigen" (turkey egg-white lysozyme (TEL) or bovine serum albumin) or "hapten" (2-phenyloxazol-5-one (phOx], and the encoding heavy and light chain genes were sequenced. The V-genes were human with some nearly identical to known germ-line V-genes, while others were more heavily mutated. Soluble antibody fragments were prepared and shown to bind specifically to antigen or hapten and with good affinities, Ka (TEL) = 10(7) M-1; Ka (phOx) = 2 x 10(6) M-1. Isolation of higher-affinity fragments may require the use of larger primary libraries or the construction of secondary libraries from the binders. Nevertheless, our results suggest that a single large phage display library can be used to isolate human antibodies against any antigen, by-passing both hybridoma technology and immunization.

Amino Acid Sequence↗
PubMed1991

Making antibody fragments using phage display libraries.

To by-pass hybridoma technology and animal immunization, we are trying to build antibodies in bacteria by mimicking features of immune selection. Recently we used fd phage to display antibody fragments fused to a minor coat protein, allowing enrichment of phage with antigen. Using a random combinatorial library of the rearranged heavy (VH) and kappa (V kappa) light chains from mice immune to the hapten 2-phenyloxazol-5-one (phOx), we have now displayed diverse libraries of antibody fragments on the surface of fd phage. After a single pass over a hapten affinity column, fd phage with a range of phOx binding activities were detected, at least one with high affinity (dissociation constant, Kd = 10(-8) M). A second pass enriched for the strong binders at the expense of the weak. The binders were encoded by V genes similar to those found in anti-phOx hybridomas but in promiscuous combinations (where the same V gene is found with several different partners). By combining a promiscuous VH or V kappa gene with diverse repertoires of partners to create hierarchical libraries, we elicited many more pairings with strong binding activities. Phage display offers new ways of making antibodies from V-gene libraries, altering V-domain pairings and selecting for antibodies with good affinities.

Amino Acid Sequence↗
PubMed1991

Multi-subunit proteins on the surface of filamentous phage: methodologies for displaying antibody (Fab) heavy and light chains.

The display of proteins on the surface of phage offers a powerful means of selecting for rare genes encoding proteins with binding activities. Recently we found that antibody heavy and light chain variable (V) domains fused as a single polypeptide chain to a minor coat protein of filamentous phage fd, could be enriched by successive rounds of phage growth and panning with antigen. This allows the selection of antigen-binding domains directly from diverse libraries of V-genes. Now we show that heterodimeric Fab fragments can be assembled on the surface of the phage by linking one chain to the phage coat protein, and secreting the other into the bacterial periplasm. Furthermore by introducing an amber mutation between the antibody chain and the coat protein, we can either display the antibody on phage using supE strains of bacteria, or produce soluble Fab fragment using non-suppressor strains. The use of Fab fragments may offer advantages over single chain Fv fragments for construction of combinatorial libraries.

Amino Acid Sequence↗
PubMed1990

Phage antibodies: filamentous phage displaying antibody variable domains.

New ways of making antibodies have recently been demonstrated using gene technology. Immunoglobulin variable (V) genes are amplified from hybridomas or B cells using the polymerase chain reaction, and cloned into expression vectors. Soluble antibody fragments secreted from bacteria are then screened for binding activities. Screening of V genes would, however, be revolutionized if they could be expressed on the surface of bacteriophage. Phage carrying V genes that encode binding activities could then be selected directly with antigen. Here we show that complete antibody V domains can be displayed on the surface of fd bacteriophage, that the phage bind specifically to antigen and that rare phage (one in a million) can be isolated after affinity chromatography.

Amino Acid Sequence↗
PubMed1989

Binding activities of a repertoire of single immunoglobulin variable domains secreted from Escherichia coli.

In antibodies, a heavy and a light chain variable domain, VH and VL, respectively, pack together and the hypervariable loops on each domain contribute to binding antigen. We find, however, that isolated VH domains with good antigen-binding affinities can also be prepared. Using the polymerase chain reaction, diverse libraries of VH genes were cloned from the spleen genomic DNA of mice immunized with either lysozyme or keyhole-limpet haemocyanin. From these libraries, VH domains were expressed and secreted from Escherichia coli. Binding activities were detected against both antigens, and two VH domains were characterized with affinities for lysozyme in the 20 nM range. Isolated variable domains may offer an alternative to monoclonal antibodies and serve as the key to building high-affinity human antibodies. We suggest the name 'single domain antibodies (dAbs)' for these antigen binding demands.

Amino Acid Sequence↗
PubMed1988

Substitution of pre-mRNA with phosphorothioate linkages reveals a new splicing-related reaction.

In vitro transcription in the presence of a nucleoside 5'-O-(1-thiotriphosphate) has been used to prepare pre-mRNA analogues of the small intron of a rabbit beta-globin gene and flanking exon sequences. Incubation of transcripts prepared with adenosine 5'-O-(1-thiotriphosphate) in a HeLa cell nuclear extract showed that the presence of the thionucleotide in a transcript inhibited splicing, but a novel product was formed by cleavage three nucleotides upstream of the 3' splice site. This product was formed with the same kinetics as the intermediates of a normal splicing reaction, and its formation depended on the presence of intact small nuclear RNAs U1, U2, and U6. We conclude that activation of 3' splice site-proximal sequences need not be linked to exon ligation.

Adenosine Triphosphate↗
PubMed1988

Effects of RNA secondary structure on alternative splicing of pre-mRNA: is folding limited to a region behind the transcribing RNA polymerase?

The use in vivo of an alternative 5' splice site sequestered within a short stem of potential RNA secondary structure is determined by the length of the loop. Above a threshold length of loop, the alternative site is used despite the potential structure. In contrast, the alternative site is used very little or not at all during splicing in vitro with all lengths of loop that we have tested. A model is proposed which suggests that pre-mRNA is free to fold only within a limited period after transcription.

Animals↗
PubMed1987

Stereospecificity of nucleases towards phosphorothioate-substituted RNA: stereochemistry of transcription by T7 RNA polymerase.

Transcription by T7 RNA polymerase has been studied using a chiral ATP analogue. The Sp diastereoisomer of adenosine 5'-O-(1-thiotriphosphate) (ATP alpha S) was incorporated into RNA with an apparent KM of approximately 15 microM, similar to that for ATP; the Rp diastereoisomer was neither a substrate nor a competitive inhibitor. The configuration of the phosphodiester link in the RNA produced was analyzed with stereospecific nucleases. The rate of nuclease digestion was compared with the rate of digestion of phosphorothioate-substituted RNA of known stereochemistry synthesized by E. coli RNA polymerase. Surprisingly, the nucleases exhibited reduced discrimination compared with their activity on dinucleotides. The results show that phosphorothioate-substituted RNA transcribed by T7 RNA polymerase has the same configuration as that transcribed by E. coli RNA polymerase, ie. Rp. Thus, the reaction proceeds with inversion of configuration at phosphorus.

DNA-Directed RNA Polymerases↗
PubMed1986

The nails in adult type 1 pityriasis rubra pilaris. A comparison with Sézary syndrome and psoriasis.

The fingernails of twenty-four patients with classical adult (type 1) pityriasis rubra pilaris were examined for changes in nail morphology and a comparison was made with the fingernail morphology of twenty-seven consecutive psoriatic patients with nail changes. Distal yellow-brown discoloration, subungual hyperkeratosis, nail plate thickening, and splinter hemorrhages indicate a diagnosis of type 1 pityriasis rubra pilaris rather than psoriasis, while onycholysis (particularly marginal), salmon patches, small pits, and larger indentations of the nail plate indicate a diagnosis of psoriasis. Histology demonstrated that a nail biopsy would be a useful diagnostic procedure if nails were involved in isolation but provided no additional diagnostic features to those found from biopsy specimens of involved skin in the two conditions. The similarity in nail morphology between the type 1 pityriasis rubra pilaris patients and five patients with chronic erythroderma resulting from Sézary syndrome indicated that these changes may represent a nonspecific reaction pattern that may result from prolonged erythema of the proximal nail bed and matrix. The rough nails (trachyonychia) described in advanced Sézary syndrome were not observed in any of our patients.

Humans↗
PubMed1983

Constitutional aplastic anaemia: a family with a new X linked variety of amegakaryocytic thrombocytopenia.

A family is described in which three male members died in early infancy with severe thrombocytopenia and a fourth in adolescence with aplastic anaemia. One child was investigated in detail and shown to have amegakaryocytic thrombocytopenia, progressing to pancytopenia as a result of bone marrow hypoplasia. His associated congenital abnormalities differed from those described in Fanconi's aplastic anaemia, his chromosomes were normal, and the fetal haemoglobin level was 48%. Amegakaryocytic thrombocytopenia is itself rare and the index case appears unique. It is suggested that this family has a previously undescribed X linked variety of amegakaryocytic thrombocytopenia.

Abnormalities, Multiple↗