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P Bailon

Publications and source records attributed to P Bailon.

At least 19 recordsLinked to original sources
PubMed2001

Identification of model peptides as affinity ligands for the purification of humanized monoclonal antibodies by means of phage display.

A proof-of-principle study was initiated to determine whether phage-display technology could be used to identify peptides as leads in the customization of ligands for affinity chromatography and to identify a peptide or peptidomimetic for use as a Protein A alternative in the affinity purification of monoclonal antibodies. The constant region of humanized anti-Tac (HAT), prepared by pepsin digestion and receptor-affinity chromatography, was used as the target for phage display in this study. As such, 20 phage-derived peptide sequences were identified from four rounds of biopanning with two linear phage-display libraries (7-mer, containing 100 copies of 2 x 10(9) sequences and 12-mer, containing 70 copies of 1.4 x 10(9) sequences). Five peptides were synthesized for use as affinity ligands, based on sequence homology to Protein A, sequence redundancy, and amino acid motifs. The best HAT binding immobilized peptide was EPIHRSTLTALL. The best-fit analysis of this peptide sequence with Protein A yielded an alignment well within the Fc binding domain of Protein A. These results suggest that phage display can serve as a tool in the identification of peptides as model ligands for affinity chromatography.

Amino Acid Sequence↗
PubMed1998

Identification of peptides that bind to the constant region of a humanized IgG1 monoclonal antibody using phage display.

The pFc' fragments of a humanized IgG1 monoclonal antibody were generated by digestion with immobilized pepsin. These pFc' fragments were separated from F(ab')2 fragments by affinity chromatography. The pFc' fragments corresponding to the constant region of the humanized IgG1 monoclonal antibody were used as targets for phage display using variable-length peptide libraries. Interacting phage-displayed peptides were selected by repetitious cycles of target screening and phage amplification. Peptide sequences, deduced by sequencing DNA from isolated phage, were aligned and analyzed for amino acid motifs against each other and protein A. These results indicated that an amino acid motif has been identified using phage display technology that is sufficient for pFc' binding. Furthermore, the peptides derived from this study may prove useful in the development of peptidomimetic alternatives to protein A for use in affinity chromatography.

Amino Acid Sequence↗
PubMed1997

Positional isomers of monopegylated interferon alpha-2a: isolation, characterization, and biological activity.

The success of recombinant interferon alpha in the clinic in part is limited by two properties of the protein: short serum half-life and immunogenicity. To improve these properties, interferon alpha-2a was conjugated with polyethylene glycol (PEG-5000). A homogeneous preparation of monopegylated interferon alpha-2a was subjected to vigorous analytical and activity characterization. A newly developed ampholyte-free chromatofocussing-like cation-exchange HPLC method utilizing a sulfopropyl resin was used to separate the monopegylated protein into 11 species. Peptide mapping, sequencing, and mass spectrometric analyses indicated that these species are positional isomers where each isomer represents a single polymer molecule conjugated to one specific lysine residue. No species with a modification at the amino terminus was observed. All 11 isomers show antiviral and antiproliferative activities in the same range as the parent monopegylated interferon alpha-2a.

Animals↗
PubMed1994

Humanized antibody directed to the IL-2 receptor beta-chain prolongs primate cardiac allograft survival.

IL-2Rs are expressed by T cells activated in response to foreign histocompatibility Ags but not by normal cells. This difference in IL-2R expression is exploited by blockade of IL-2Rs to achieve immunosuppression. High affinity IL-2Rs involve three subunits, IL-2R alpha, IL-2R beta, and IL-2R gamma. Murine Mik beta 1, a mAb that blocks IL-2 binding to IL-2R beta, was developed as an immunosuppressive agent. There was modest prolongation of cynomolgus cardiac allograft survival in animals treated with murine Mik beta 1 (mean survival 11.8 +/- 1.6 days compared with 8.2 +/- 0.4 days in untreated animals; p = 0.06). However, murine Mik beta 1 is ineffective in recruiting primate effector cells and is neutralized by monkey Abs directed toward the infused Ab. To circumvent these limitations, a humanized form of Mik beta 1, which is a largely human IgG1k Ab, except that murine hypervariable regions are retained, was developed. In vivo plasma survival of humanized Mik beta 1 was threefold longer than simultaneously administered murine Mik beta 1 (terminal t1/2, 104 +/- 10 h vs 37 +/- 2 h). Furthermore, humanized Mik beta 1 manifests Ab-dependent cellular cytotoxicity, an activity that is absent with the parental murine Mik beta 1. Graft survival was significantly prolonged by humanized Mik beta 1 treatment with survivals of 22, 22, 24, 27, 44, and > 300 days (p vs control < 0.01; p vs murine Mik beta 1 < 0.01). Survival was not prolonged further (p > 0.3) by the addition of humanized anti-Tac, which blocks interaction of IL-2 with IL-2R alpha subunits. There was no toxicity attributable to the use of Mik beta 1 Abs. Thus, humanized Mik beta 1 prolonged cardiac allograft survival in primates without toxicity and may be effective as an adjunct to standard immunosuppressive therapy.

Animals↗
PubMed1994

Anti-Tac(Fab)-PE40, a recombinant double-chain immunotoxin which kills interleukin-2-receptor-bearing cells and induces complete remission in an in vivo tumor model.

We have produced a single plasmid encoding both the heavy chain Fd domain (VH + CH1) of the anti-interleukin-2 receptor (IL2R) monoclonal antibody anti-Tac, and the anti-Tac light chain fused to PE40, a truncated derivative of Pseudomonas exotoxin. The active immunotoxin anti-Tac(Fab)-PE40 could be recovered from E. coli from either periplasm or renatured inclusion bodies. The double-chain immunotoxin was very cytotoxic toward IL2R-bearing cell lines, human activated T cells and fresh adult-T-cell-leukemia cells. The cytotoxicity was similar to that of anti-Tac(Fv)-PE40, the single-chain recombinant toxin containing only the variable domains of anti-Tac. IL2R-binding affinity was also equivalent to that of anti-Tac(Fv)-PE40, which is one-third that of anti-Tac. The serum half-life in mice was significantly prolonged as compared with anti-Tac(Fv)-PE40, with a beta phase of 430 vs. 57 minutes, but the LD50s were equivalent when the immunotoxins were administered in 3 daily doses. Anti-Tac(Fab)-PE40 was very cytotoxic in vitro toward transfected ATAC-4 carcinoma cells which express IL2Rs. In mice bearing ATAC-4 tumors, anti-Tac(Fab)-PE40 showed significant anti-tumor activity, inducing complete remissions in 80 and 100% of treated animals at approximately 7 and 14% respectively of the LD50. Anti-Tac(Fab)-PE40 was much more effective in vitro and in vivo than chemical conjugates between anti-Tac and truncated PE molecules. The recombinant Fab toxin should be studied further as potential treatment for IL2R-related malignancies, particularly if smaller recombinant immunotoxins have insufficient half-life in humans.

ADP Ribose Transferases↗
PubMed1994

Recombinant immunotoxins containing anti-Tac(Fv) and derivatives of Pseudomonas exotoxin produce complete regression in mice of an interleukin-2 receptor-expressing human carcinoma.

Anti-Tac(Fv)-PE40 is a recombinant single-chain immunotoxin composed of the variable domains of the monoclonal antibody anti-Tac, which binds to the p55 subunit of the interleukin-2 receptor (IL-2R), and a truncated form of Pseudomonas exotoxin (PE), which does not bind to the PE receptor (Chaudhary et al, Nature 339:394, 1989). Whereas its cytotoxic activity toward autoimmune and malignant target cells has been established, its efficacy in vivo remains unknown. To establish an animal model, we produced ATAC-4 cells by transfecting the gene encoding the low-affinity IL-2R (p55) into A431 epidermoid carcinoma cells. ATAC-4 cells contained low-affinity IL-2Rs (2 x 10(5)/cell) and formed tumors in nude mice. In tissue culture, protein synthesis in ATAC-4 cells was inhibited 50% (IC50) at 0.06 ng/mL (0.9 pmol/L) of anti-Tac(Fv)-PE40. IC50s for the derivatives anti-Tac(Fv)-PE38, which is missing PE amino acids 365-380, and anti-Tac(Fv)-PE38KDEL, which contains the same deletion plus the KDEL carboxyl terminus, were 0.04 and 0.025 ng/mL, respectively. All the agents produced complete tumor regressions in ATAC-4 tumor-bearing mice and anti-Tac(Fv)-PE38KDEL had significant antitumor activity at 1% of the LD50. The dose limiting toxicity of anti-Tac(Fv)-PE38KDEL was from hemorrhagic liver necrosis, which was observed at approximately 55% of the LD50.

ADP Ribose Transferases↗
PubMed1993

Characterization of lymphokine-activated killing by human peripheral blood mononuclear cells stimulated with interleukin 2 (IL-2) analogs specific for the intermediate affinity IL-2 receptor.

Interleukin 2-stimulated human peripheral blood mononuclear cells (PBMC) generate lymphokine-activated killing (LAK). Using the IL-2 analogs R38A and F42K, which interact primarily with the beta and gamma subunits of the IL-2 receptor, we assessed the roles of IL-2R beta gamma and the high-affinity IL-2 receptor complex in LAK activation. Although the kinetics of LAK activation were identical, lytic activity was approximately 30% lower and proliferation was up to 55% lower in those PBMC stimulated by R38A or F42K than in those exposed to wild-type IL-2. The percentage of cells expressing cell-surface markers such as CD3, CD4, CD8, and CD16 was not significantly different after treatment with wild-type IL-2, R38A, or F42K; however, the proportion of cells expressing IL-2R alpha increased dramatically in response to stimulation by F42K (30%) compared to stimulation by either rIL-2 or R38A (15%). In addition, by Day 7 the concentration of soluble IL-2R alpha in analog-stimulated LAK culture supernatants was 50-75% less than that from wild-type IL-2-cultured cells. These findings suggest that interaction of IL-2 with IL-2R beta gamma alone is sufficient for both proliferation and the generation of LAK, and that stimulation with subunit-specific IL-2 analogs results in differential regulation of the IL-2R alpha on human LAK cells.

Binding, Competitive↗
PubMed1992

Membrane-based receptor affinity chromatography.

Membrane-based receptor affinity chromatography (MRAC), which utilizes the molecular recognition between an immobilized receptor and its soluble protein ligand, has been developed for the purification of human interleukin-2 and related biomolecules. The multi-purpose affinity membrane used in this study consisted of a soluble form of interleukin-2 receptor (IL-2R) chemically bonded to hollow-fiber membranes in an oriented fashion. A model system involving anti-Tac-H (a humanized monoclonal antibody to IL-2R) was used to study the important factors influencing the performance of MRAC, including support morphology, mass transfer rate and adsorption kinetics. All three are shown to be highly efficient. MRAC has been successfully applied to the purification of anti-Tac-H, recombinant human interleukin-2 (rIL-2) and interleukin 2-Pseudomonas exotoxin fusion protein (IL2-PE40). Overall, MRAC was found to be a viable, scalable and extremely productive affinity purification method.

Adsorption↗
PubMed1991

Reduced immunogenicity and improved pharmacokinetics of humanized anti-Tac in cynomolgus monkeys.

The anti-Tac mAb has been shown to bind to the p55 chain of the IL-2R, block IL-2 binding and inhibit T cell proliferation. A humanized form of anti-Tac (HAT) has been constructed that retains the binding properties of murine anti-Tac (MAT). These two mAb were evaluated in cynomolgus monkeys to compare relative immunogenicity and pharmacokinetic properties. Monkeys treated with HAT daily for 14 days exhibited anti-HAT antibody titers which were 5- to 10-fold lower than their MAT-treated counterparts and these antibodies developed later than in the MAT-treated monkeys. Two of four monkeys receiving a single injection of MAT developed anti-MAT antibodies, whereas none of four monkeys developed antibodies after a single treatment with HAT. In monkeys injected with either HAT or MAT daily for 14 days, the anti-antibody titers induced were inversely related to the amount of anti-Tac administered. Antibodies that developed against MAT were both anti-isotypic and anti-idiotypic, whereas those developed against HAT appeared to be predominantly anti-idiotypic. The pharmacokinetic properties, that is the half-life and area under the curve values, of HAT were also significantly different from those of MAT. The area under the curve values for HAT in naive monkeys were approximately twofold more than those for MAT, and the mean serum half-life of HAT was 214 h, approximately four- to fivefold more than MAT. These pharmacokinetic values were reduced in monkeys previously sensitized with HAT or MAT suggesting that the presence of anti-antibodies altered these parameters.

Animals↗
PubMed1991

Localization in human interleukin 2 of the binding site to the alpha chain (p55) of the interleukin 2 receptor.

Human interleukin 2 (IL-2) analogs with defined amino acid substitutions were used to identify specific residues that interact with the 55-kDa subunit (p55) or alpha chain of the human IL-2 receptor. Analog proteins containing specific substitutions for Lys-35, Arg-38, Phe-42, or Lys-43 were inactive in competitive binding assays for p55. All of these analogs retained substantial competitive binding to the intermediate-affinity p70 subunit (beta chain) of the receptor complex. The analogs varied in ability to interact with the high-affinity p55/p70 receptor. Despite the lack of binding to p55, all analogs exhibited significant biological activity, as assayed on the murine CTLL cell line. The dissociation constants of Arg-38 and Phe-42 analogs for p70 were consistent with intermediate-affinity binding; the Kd values were not significantly affected by the presence of p55 in binding to the high-affinity IL-2 receptor complex. These results confirm the importance of the B alpha-helix in IL-2 as the locus for p55-receptor binding and support a revised model of IL-2-IL-2 receptor interaction.

Amino Acid Sequence↗
PubMed1990

Application of receptor-affinity chromatography to bioaffinity purification.

Receptor-affinity chromatography based upon the receptor-ligand interactions has been utilized for the purification of recombinant human interleukin-2 (rIL-2) from microbial and mammalian sources. The receptor-affinity purification process of rIL-2 is used as a model system to demonstrate the utility of this approach for the purification of recombinant proteins. The receptor-affinity purified biomolecule is shown to be biochemically and biologically more homogeneous than the immunoaffinity purified material.

Amino Acids↗
PubMed1990

The use of proteolysis and direct N-terminal sequence analysis to study human interleukin-2/receptor interaction on solid support.

An immobilized interleukin-2 receptor which is capable of binding interleukin-2 and suitable for direct N-terminal sequence analysis was employed to study interleukin-2/receptor interactions. Sensitive tryptic sites on the immobilized receptor and its interleukin-2 complex were identified by sequence analyses and compared. The results have revealed that the N-terminal region of interleukin-2 is not involved in receptor binding and the peptide segment covering residues 36-39 in the receptor is probably near or involved in the interleukin-2 binding site. The rapidity and simplicity make this solid phase sequence approach a good method for analyzing interleukin-2/receptor interaction and may be suitable for studying other protein-ligand interactions.

Amino Acid Sequence↗
PubMed1990

Purification of the IL-2 receptor (TAC) by ligand-affinity chromatography and utilization of the immobilized receptor for receptor-affinity chromatography (RAC) purification of IL-2, mutant IL-2, and IL-2 fusion proteins.

Recombinant technology has facilitated the production of two soluble forms of human p55 interleukin-2 receptor (IL-2R) in Chinese hamster ovary cells. We have developed a ligand-affinity method for the medium-scale purification of these two soluble forms of the IL-2R, based on the biochemical interactions between the matrix-bound ligand (interleukin-2) and its soluble receptor. The affinity-purified IL-2R is further purified by anion-exchange chromatography followed by gel filtration. This method has provided enough highly pure IL-2R for structure and function studies and for use in practical applications such as high-flux drug-screening assays. The purified IL-2R subsequently has been immobilized on silica gel and employed for the purification of recombinant IL-2. Receptor-affinity-chromatography-purified IL-2 contains only a highly active monomeric form of the lymphokine, in contrast to immunoaffinity chromatography where several molecular forms of IL-2 with varying degrees of biologic activity are recovered. Receptor-affinity chromatography has been successfully applied to the purification of several mutant IL-2 as well as an IL-2-Pseudomonas exotoxin (IL2-PE40) fusion protein that is a 54.5-kDa chimeric protein in which the cell recognition domain is replaced by IL-2. The IL-2-PE40 is a potential cytotoxic agent for cells bearing the IL-2 receptor.

ADP Ribose Transferases↗
PubMed1988

Interleukin 2 (IL2) PE40 is cytotoxic to cells displaying either the p55 or p70 subunit of the IL2 receptor.

IL2-PE40 is a chimeric protein composed of human interleukin 2 (IL2) genetically fused to the amino terminus of a modified form of pseudomonas exotoxin (PE). Internalization of IL2 via the individual p55 and p70 subunits of the IL2 receptor was studied using IL2-PE40 on several mouse and human cell lines expressing either the p55, the p70, or both IL2 receptor subunits. Internalization was assessed by measuring inhibition of protein synthesis caused by the toxin moiety of IL2-PE40. The results demonstrate that IL2 internalization is mediated by either the p55 receptor subunit or by the p70 subunit but is much more efficient when high affinity receptors composed of both subunits are present. IL2-PE40 is a powerful reagent for studying IL2 receptor interactions and for analyzing pathways of the immune response and its regulation.

ADP Ribose Transferases↗