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A P Lewis

Publications and source records attributed to A P Lewis.

16 recordsLinked to original sources
PubMed1998

A C-terminal helicase domain of the human papillomavirus E1 protein binds E2 and the DNA polymerase alpha-primase p68 subunit.

The human papillomavirus (HPV) E1 and E2 proteins bind cooperatively to the viral origin of replication (ori), forming an E1-E2-ori complex that is essential for initiation of DNA replication. All other replication proteins, including DNA polymerase alpha-primase (polalpha-primase), are derived from the host cell. We have carried out a detailed analysis of the interactions of HPV type 16 (HPV-16) E1 with E2, ori, and the four polalpha-primase subunits. Deletion analysis showed that a C-terminal region of E1 (amino acids [aa] 432 to 583 or 617) is required for E2 binding. HPV-16 E1 was unable to bind the ori in the absence of E2, but the same C-terminal domain of E1 was sufficient to tether E1 to the ori via E2. Of the polalpha-primase subunits, only p68 bound E1, and binding was competitive with E2. The E1 region required (aa 397 to 583) was the same as that required for E2 binding but additionally contained 34 N-terminal residues. In confirmation of these differences, we found that a monoclonal antibody, mapping adjacent to the N-terminal junction of the p68-binding region, blocked E1-p68 but not E1-E2 binding. Sequence alignments and secondary-structure prediction for HPV-16 E1 and other superfamily 3 (SF3) viral helicases closely parallel the mapping data in suggesting that aa 439 to 623 constitute a discrete helicase domain. Assuming a common nucleoside triphosphate-binding fold, we have generated a structural model of this domain based on the X-ray structures of the hepatitis C virus and Bacillus stearothermophilus (SF2) helicases. The modelling closely matches the deletion analysis in suggesting that this region of E1 is indeed a structural domain, and our results suggest that it is multifunctional and critical to several stages of HPV DNA replication.

Antibodies, Monoclonal↗
PubMed1995

Engineered anti-CD38 monoclonal antibodies for immunotherapy of multiple myeloma.

Multiple myeloma is a malignancy of plasma cells for which there is no effective treatment. To develop an immunotherapeutic agent, we have raised a high affinity mAb (AT13/5) against CD38, one of the few well-characterized surface Ags present on myeloma cells. Since murine monoclonals have many disadvantages as human therapeutics, we prepared two engineered forms of the Ab: a CDR-grafted humanized IgG1 and a chimeric FabFc2 (mouse Fab cross-linked to two human gamma 1 Fc). To retain affinity in the humanized Ab, a number of changes were required to the human framework regions of the heavy chain. In particular, through systematic mutagenesis and computer modeling, we identified a critical interaction between the side chains of residues 29 and 78, which may be important for the humanization of other Abs. The properties of the humanized IgG1 and FabFc2 constructs were compared in a series of in vitro tests. Both constructs efficiently directed Ab-dependent cellular cytotoxicity against CD38-positive cell lines, but C was activated only poorly. Neither construct caused down-modulation of CD38, nor did they affect the NADase activity of CD38. Despite their differing structures, both Abs showed similar activity in most assays, although the humanized IgG1 was more potent at inducing monocyte cytotoxicity. These data represent the first direct comparison of CDR-grafted and chimeric FabFc2 forms of the same Ab, and offer no support for the perceived advantages of the FabFc2. These Abs show promise for therapy of multiple myeloma and other diseases involving CD38-positive cells.

ADP-ribosyl Cyclase↗
PubMed1995

Detection of rare allelic variants of the interferon-alpha 2 gene in human genomic DNA.

We have analyzed human donor DNA for the presence of sequences corresponding to allelic variants of the IFN-alpha 2 locus. Using both restriction enzyme digestion of PCR-amplified fragments and sequence analysis of these fragments, we have identified the three reported allelic variants, IFN-alpha 2a, IFN-alpha 2b, and IFN-alpha 2c, in genomic DNA derived from donors of African or Afro-Caribbean origin. This is the first report of the IFN-alpha 2a and IFN-alpha 2c alleles occurring in human donor DNA and supports the view that these are variants of the predominant IFN-alpha 2b allele rather than arising from mutations occurring in cultured cells.

Alleles↗
PubMed1994

Interferon (IFN)-alpha 2 genotype analysis of Chinese chronic hepatitis B patients undergoing recombinant IFN-alpha 2a therapy.

Sixteen Chinese chronic hepatitis B virus (HBV)-infected patients were treated with recombinant interferon-alpha 2a (rIFN-alpha 2a). Of these, 8 made a response to IFN, with titers of neutralizing antibody of 141-4525 as determined by an antiviral neutralization bioassay. To determine whether the immunogenicity of the IFN was directly linked to the patients' genotype, their genomic DNA was analyzed for the presence of the human IFN-alpha 2a gene. None of the patients possessed the gene for IFN-alpha 2a, but only 50% developed neutralizing antibodies. The hypothesis, therefore, of a direct link between antibody formation and genotype cannot be sustained. Alternative explanations of the immunogenicity of IFN-alpha 2a must be sought.

Adult↗
PubMed1993

Rescue, expression, and analysis of a neutralizing human anti-hepatitis A virus monoclonal antibody.

A human anti-hepatitis A virus mAb was rescued from a hybridoma cell line by conventional cDNA cloning, and expressed in CHO cells. The full nucleotide sequences of the mAb H and L chains were determined, revealing a VHI/V lambda II V region combination. Comparisons with germline V genes suggest that the V regions had undergone somatic mutations characteristic of an Ag-driven immune response. A comparison of the binding to hepatitis A virus between mAb derived from the CHO cells and the original hybridoma cell line using ELISA, radioimmunoprecipitation, and solid-phase competition RIA, indicated that the CHO cell-derived mAb fully retained the specificity of the mAb produced by hybridoma cells. Analysis of viral neutralization using a radioimmunofocus inhibition assay demonstrated the retention of antibody functionality after expression in CHO cells, demonstrating the use of this technique in the rescue and high level expression of unstable efficacious human mAb.

Amino Acid Sequence↗
PubMed1993

A humanized CD18 antibody can block function without cell destruction.

Leukocyte integrins are intimately involved in transient adherence of leukocytes to endothelium and to each other in the processes of extravasation and cell activation. In this study, seven mAb directed against human CD11a and two mAb directed against human CD18, the alpha- and beta-chains of the leukocyte functional Ag-1 molecule, respectively, were analyzed for their ability to inhibit several leukocyte functional Ag-1-mediated interactions. The best blocking mAb in these studies, a rat anti-human CD18, YFC51.1, was subsequently humanized by complementarily-determining region grafting, associated with human C regions and expressed. The humanized mAb was shown to maintain binding for human CD18. Even though the humanized mAb was an IgG1 isotype it still retained the functional blocking characteristics of the rat mAb while failing to mediate cell killing. The IgG1 mAb was unable to bind human Clq and could block but did not mediate antibody-dependent cellular cytotoxicity.

Animals↗
PubMed1992

Rescue and expression of human immunoglobulin genes to generate functional human monoclonal antibodies.

Human monoclonal antibody production has been hampered for many years by the instability of cell lines and low levels of expression of the antibodies. We describe here the rescue of human immunoglobulin genes utilizing micro-mRNA preparation from a small number of human hybridoma cells and conventional cDNA cloning. This allows cloning and immediate high-level expression from full-length human heavy and light chain cDNA molecules and provides a mechanism to rescue whole human monoclonal antibodies of proven efficacy.

Antibodies, Monoclonal↗
PubMed1991

Immunoglobulin complementarity-determining region grafting by recombinant polymerase chain reaction to generate humanised monoclonal antibodies.

We describe an approach to rapidly generate humanised monoclonal antibodies by grafting rodent complementarity-determining regions onto human immunoglobulin frameworks using recombinant polymerase chain reaction (PCR) methodology. The approach was applied to grafting a rat complementarily-determining region onto a human framework and amplifying the entire humanised heavy chain. The terminal oligodeoxyribonucleotide primers incorporated restriction sites to allow forced cloning into plasmid vectors for sequencing and expression. No nucleotide errors were introduced into the 1463-bp sequence even after sequential applications of PCR.

Animals↗
PubMed1990

A joint course for general practitioner and practice nurse trainers.

An experimental multidisciplinary course for prospective general practitioner and practice nurse trainers is described. Factual knowledge and attitudes were measured before and after the course and some of the changes measured emphasized the importance of multidisciplinary training. The ideas generated by the group of nurse trainers in terms of their future professional development were identified.

Education, Medical, Continuing↗
PubMed1989

Cloning and analysis of the gene encoding the 230-kilodalton merozoite surface antigen of Plasmodium yoelii.

The complete nucleotide sequence of the gene for the 230-kDa precursor to the major merozoite surface antigens (PMMSA) of Plasmodium yoelii YM has been determined. A single open reading frame of 5316 bp encodes a protein of calculated molecular mass 197,000. The deduced amino acid sequence contains potential signal peptide and membrane anchor sequences of 19 and 18 residues, respectively, and a region of six tandemly repeated tetrapeptides, Gly-Ala-Val-Pro. Comparison with the 195-kDa Plasmodium falciparum analogue (Pf195) at the amino acid level indicated an overall homology of approximately 30%, with areas of as high as 60% conservation. The tripeptide repeats present near the N-terminus of the Pf195 antigen are absent from the Py230 sequence. The PMMSA can be divided into 22 blocks based upon interspecies amino acid conservation.

Amino Acid Sequence↗
PubMed1989

Somatic reversion of P transposable element insertion mutations in the singed locus of Drosophila melanogaster requiring specific P insertions and a trans- acting factor.

Destabilization in somatic cells of P-element insertions in the X-linked singed gene of Drosophila melanogaster has been studied. We have shown that some but not all unstable P-element insertions in singed can form mosaics. The cause of this variation is not clear from studies of the restriction maps of the mutations tested. The transposable element movements occur early in development and require, in addition to an appropriate P-element insertion in singed, a trans-acting maternal effect component. Movements appear to occur preferentially in attached-X stocks. However, the maternal effect component maps to the central region of chromosome 2.

Animals↗
PubMed1989

General practitioners and their learning styles.

Continuing medical education sessions are often poorly attended by general practitioners. One reason may be that these traditionally consist of lectures by hospital consultants with a strong theoretical bias which may have little relevance to the learning needs of general practitioners. To compare the learning styles of teachers and learners in general practice, learning style questionnaires were administered to 50 hospital clinical tutors, 78 general practitioner trainers, 63 trainees and 47 non-trainer principals. The questionnaire covered four different learning preferences: activist, reflector, theorist and pragmatist. The findings showed that the learning styles of hospital tutors and general practitioner trainers were statistically significantly different to those of non-trainer principals and trainees. The tutors and trainers scored much higher on theorist styles and to a lesser extent on reflector and pragmatist styles. There were no significant differences on activist scores. Since teachers tend to teach in their preferred learning style, which may not match the style of the recipients, these findings have implications for continuing medical education in general practice. These implications are discussed.

Education, Medical, Continuing↗
PubMedDate not supplied

Cloning and sequence analysis of kappa and gamma cynomolgus monkey immunoglobulin cDNAs.

One gamma heavy chain and 10 kappa light chain cynomolgus monkey (Macaca fascicularis) immunoglobulin cDNAs have been cloned and sequenced. Comparisons of the variable (V) regions to human antibody sequences have revealed extensive identity, exhibiting 93% at the amino acid level for the VH framework regions, and 88-99% for the V kappa frameworks. Identification of very few cynomolgus monkey-specific framework region residues suggests a role for cynomolgus monkey antibodies as donators of variable regions to chimeric monoclonal antibodies for utilisation in human therapy with human constant (C) regions. The cynomolgus monkey C kappa region exhibited 83% amino acid identity to its human counterpart, and the C gamma region was 95, 93, 95, and 95% similar to the human C gamma 1, C gamma 2, C gamma 3, and C gamma 4 regions, respectively. Evolutionary analysis of the C gamma genes, using the silent molecular clock, suggests that the divergence between cynomolgus monkey and human occurred before the time at which the ancestral gamma gene diverged into the multiple isotypes observed in humans.

Amino Acid Sequence↗