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Results for “Epitope Mapping”

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PubMed1997

Conservation of fimbriae and the hemagglutinating adhesin HA-Ag2 among Porphyromonas gingivalis strains and other anaerobic bacteria studied by epitope mapping analysis.

Monoclonal antibodies characterized as antifimbria and anti-HA-Ag2 were used in immunoblotting to examine the antigenic distribution of fimbriae and HA-Ag2 among a collection of human and animal Porphyromonas strains and human Prevotella and Bacteroides strains. The results showed that fimbrial and HA-Ag2 antigenic structures are peculiar to the species Porphyromonas gingivalis.

Animals↗

PubMed1990

Antibody response in children to antigen sites on human PIV-3 HN: correlation with known epitopes mapped by monoclonal antibodies.

The antibody response in children to known epitopes on the HN of human parainfluenza virus type 3 was investigated. Children's sera with Haemagglutination-Inhibition titres between 1/480 to 1/1280 were used. When tested by ELISA, this high-titre serum from each of five children blocked 7 of 17 specific anti-HN murine monoclonal antibodies by greater than 75% at 1 micrograms well-1 of antigen. However, four monoclonal antibodies were blocked less than or equal to 30%, while six were partially blocked between 50% and 75%. Antigen concentrations of 0.5, 1.5 and 2.0 micrograms well-1 did not substantially change this pattern. Comparison of our results with published antigenic maps indicated that antigenic site A on the HN protein was the site with the most significant antibody representation in the children's sera. These findings suggest that antigenic maps deduced using monoclonal antibodies need to be carefully interpreted before they are used in vaccine development. Murine monoclonal antibodies may not fully represent either qualitatively or quantitatively important antibody components of the human or murine immune response to human PIV-3 HN.

Antibodies, Monoclonal↗

PubMed1994

Antibodies to collagen: comparative epitope mapping in women with silicone breast implants, systemic lupus erythematosus and rheumatoid arthritis.

Women with silicone breast implants have a significantly increased frequency of antibodies to collagen types I and II. To characterize the specificity of these antibodies, 70 women without a specific autoimmune disease, according to the criteria of the American College of Rheumatology, but who had silicone breast implants were studied for the presence of serum antibodies to native and denatured human types I and II collagen by ELISA. Positive sera were further studied by immunoblotting using peptides derived by cyanogen bromide digestion of the collagens. Samples of 82 women with systemic lupus erythematosus (SLE), 94 women with rheumatoid arthritis (RA), and 133 healthy controls were studied concurrently. There was a high frequency of autoantibodies to collagen in each of the study groups when compared to the healthy controls. However, and of particular interest, the epitope specificity of the autoantibodies differed markedly. Sera from women with silicone implants reacted strongly in an individual-specific manner with multiple peptides of type I collagen, whereas sera from women with SLE and RA reacted only weekly with a restricted range of peptides of type I collagen. Sera from women with RA reacted strongly with multiple peptides of type II, whereas sera from women with silicone implants or SLE reacted only weakly. The reactivity of women with silicone implants suggests that silicone or its biodegradation products can act as adjuvants in situ to enhance the immunogenicity of type I collagen, or protein-silicone conjugates.

Arthritis, Rheumatoid↗

PubMed1995

Epitope mapping and analysis of a growth-enhancing monoclonal antibody by limited tryptic digestion of porcine GH.

In this study, the epitope of a murine PS-7.6 monoclonal antibody (mAb) which was raised against the recombinant porcine GH (pGH) and subsequently shown to enhance the growth-promoting activity of pGH in a hypophysectomized rat model, was mapped by the limited tryptic digestion of pGH. A pGH fragment corresponding to amino acid residues 70-95 was separated by reverse-phase HPLC and also immunoprecipitated by PS-7.6 mAb. This fragment was found in an RIA to compete with radiolabelled pGH for the binding of PS-7.6 mAb in a dose-dependent fashion. Several peptides covering this potential epitope region of pGH(70-95) were synthesized and assayed by competitive RIA. The results suggested that pGH(75-90) was the optimal sequence recognized by PS-7.6 mAb. Sequential alanine substitution of each residue of pGH(75-90) revealed that the side chains of Leu76, Ile83 and Leu87 were critical for binding to PS-7.6 mAb. Other residues could be replaced by alanine without substantially altering the binding affinity. The region of amino acids 75-95 comprises the C-terminal end of the second helix of pGH and the repeating pattern of i and i + 3 (i + 7) of the critical amino acids appears consistent with PS-7.6 mAb binding to the hydrophobic side of the helix. The sequence and the helical structure of the epitope of PS-7.6 mAb provide the basis for designing the effective peptide vaccines to enhance the growth performance of animals.

Amino Acids↗

PubMed1994

Epitope mapping of the branched chain alpha-ketoacid dehydrogenase dihydrolipoyl transacylase (BCKD-E2) protein that reacts with sera from patients with idiopathic dilated cardiomyopathy.

Sera from 29 of 48 patients with idiopathic dilated cardiomyopathy (IDCM) and six of six patients with dilated cardiomyopathy (DCM) secondary to suspected viral myocarditis were shown to react with the branched chain alpha-ketoacid dehydrogenase (BCKD) complex mitochondrial proteins. Whereas sera from only 1 of 26 patients with ischemic heart disease showed reactivity against the BCKD complex protein, 0 of 30 sera from normal human volunteers, 0 of 64 sera from patients with lupus, and 0 of 34 sera from patients with rheumatoid arthritis showed detectable reactivity, denoting an element of specificity for the reactivity of sera from IDCM patients. The major reactivity was localized to the dihydrolipoyl transacylase (E2) component of BCKD complex. By using recombinant techniques, the immunodominant BCKD-E2 epitope recognized by sera from IDCM patients was localized to amino acid (aa) sequences 116 to 134. Each of the IDCM sera that reacted with the native BCKD complex was shown to react with the immunodominant peptide, as defined by a peptide inhibition ELISA and by an ELISA using the reactive peptide conjugated to BSA. Sera from IDCM patients that reacted with the native BCKD complex and the reactive peptide also showed inhibition of BCKD enzyme activity. The possible mechanisms for the induction of the Abs and the implications of these findings for the pathogenesis of IDCM are discussed.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed1995

Epitope mapping for monoclonal antibody against human surfactant protein A (SP-A) that alters receptor binding of SP-A and the SP-A-dependent regulation of phospholipid secretion by alveolar type II cells.

Surfactant protein A (SP-A) is a lung-specific glycoprotein in pulmonary surfactant and has a collagen like sequence on its N-terminal. SP-A has been shown to function as an inhibitor of phospholipid secretion by primary culture of alveolar type II cells via cell surface receptor(s) for SP-A. In a previous report, we showed that the C-terminal non-collagen like domain of human SP-A possessed the biological activities, and that a monoclonal antibody against human SP-A, PE10, abolished the biological activity of SP-A (Murata et al. (1993) Biochem. J. 291, 71-76). In the present study, we investigated an epitope of SP-A for PE10. Western blot analysis with fragmented peptides of human SP-A generated by both lysyl endopeptidase and BrCN showed that PE10 reacted with the peptide corresponding with Glu202 to the C-terminal but that it lacked the ability to bind to the peptide corresponding with Tyr208 to the C-terminal. The antibodies against a synthetic peptide (P1) corresponding with Glu202 to Asn217 of human SP-A inhibited the binding of PE10 to SP-A, suggesting that a similar site was recognized by both PE10 and anti-P1 antibodies. Anti-P1 antibodies as well as PE10 suppressed the biological activity of SP-A. A direct interaction between P1 and rat lung membranes, or between P1 and alveolar type II cell membranes was shown from the measurement of the fluorescence emission spectra of dansyl-labeled P1. These results suggest that an area contiguous to or near the region from Glu202 to Met207 of SP-A is important for expressing the biological activities.

Amino Acid Sequence↗

PubMed2002

Epitope mapping of the O-chain polysaccharide of Legionella pneumophila serogroup 1 lipopolysaccharide by saturation-transfer-difference NMR spectroscopy.

Two modifications of 5-acetimidoylamino-7-acetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic acid (5-N-acetimidoyl-7-N-acetyllegionaminic acid) in the O-chain polysaccharide (OPS) of the Legionella pneumophila serogroup 1 lipopolysaccharide (LPS) concern N-methylation of the 5-N-acetimidoyl group in legionaminic acid. Both N-methylated substituents, the (N,N-dimethylacetimidoyl) amino and acetimidoyl(N-methyl)amino group, could be allocated to one single legionaminic acid residue in the long- and middle-chain OPS, respectively. Using mutants devoid of N-methylated legionaminic acid derivatives, it could be shown that N-methylation of legionaminic acid correlated with the expression of the mAb 2625 epitope. In the present study we investigated the binding of the LPS-specific monoclonal antibody mAb 2625 to isolated OPS with surface-plasmon-resonance biomolecular interaction analysis and saturation-transfer-difference (STD) NMR spectroscopy in order to map the mAb 2625 epitope on a molecular level. It could be demonstrated that the binding affinity of the N-methylated legionaminic acid derivatives was independent from the size of the isolated OPS molecular species. In addition, STD NMR spectroscopic studies with polysaccharide ligands with an average molecular mass of up to 14 kDa revealed that binding was mainly mediated via the N-methylated acetimidoylamino group and via the closely located 7-N-acetyl group of the respective legionaminic acid residue, thus indicating these derivatives to represent the major epitope of mAb 2625.

Antibodies, Monoclonal↗

PubMed1994

Epitope mapping of region 11-70 of ovalbumin (Gal d I) using five synthetic peptides.

Five successively located peptides, in region 11-70 of the major allergen of ovalbumin (OA) Gal d I (11-19, 20-33, 34-46, 47-55, 56-70), were obtained by manual solid-phase peptide synthesis. These peptides together with the previously reported OA region 1-10 comprise a segment of 70 amino acid residues located at the N-terminal of ovalbumin. The crude peptides were purified by gel filtration and reversed-phase high-performance liquid chromatographies and their sequences were verified. Polyclonal antibodies against the peptides conjugated to carrier protein (BSA) were raised in rabbits. Rocket line immunoelectrophoresis showed that four peptides (20-33, 34-46, 47-55 and 56-70), could deflect OA-line immunoprecipitates. The peptide's affinity to rabbit polyclonal Ig was examined by quantitative precipitation inhibition and the results suggested that an epitope was encompassed in segments 34-55 and 47-55. Allergenicity was tested by inhibition of specific IgE binding of ovalbumin, using several sera and a serum pool from 16 egg-allergic patients. The results showed that the allergenicity was distributed over the whole region. These findings suggested that: (a) the region 11-70 of OA seemed not to encompass continuous epitopes; (b) the antigenicity of this region was convincing for peptides 34-46 and 47-55; (c) the allergenicity, though dependent on the patient serum used, was distributed over the whole of region 11-70; (d) peptide 11-19, although weak antigenically was capable of specific IgE inhibition; (e) human and rabbit polyclonal antibodies did not show analogous affinities to the present peptides.

Allergens↗

PubMed1995

Epitope mapping of cross-reactive monoclonal antibodies specific for the influenza A virus PA and PB2 polypeptides.

Characterization of the epitopes recognized by 21 monoclonal antibodies (MAbs) specific for the influenza A virus PA (13 MAbs) and PB2 (8 MAbs) polypeptides (Bárcena et al. (1994) J. Virol. 68, 6900-6909) raised against denatured polypeptides produced in E. coli is described. MAbs were characterized by: (1) competitive binding ELISAs; (2) mapping of the protein regions that specify their binding sites; and (3) analyses of their ability to recognize the corresponding viral protein in a number of viral isolates. Five and three non-overlapping antigenic areas were defined by the anti-PA and anti-PB2 MAbs, respectively. Five of the anti-PA MAbs recognized antigenic determinants located within the amino-terminal 157 amino acids of the PA protein, and 6 others reacted strongly with a PA fragment comprising the first 236 amino acids. All 8 anti-PB2 antibodies reacted strongly with a polypeptide fragment containing amino acids 1-113 of the PB2 protein. Analyses of the reactivities of 4 anti-P antibodies with 23 influenza A virus reference strains isolated over a period of 61 years and recovered from humans, pigs, birds and horses, showed that the epitopes were conserved among all viral isolates. The application of these antibodies as research and diagnostic tools is discussed.

Animals↗

PubMed1998

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.

Amino Acid Sequence↗

PubMed1999

Epitope mapping of secreted mouse leptin utilizing peripherally administered synthetic peptides.

We have recently reported that intraperitoneal (i.p.) administration of synthetic peptide amides corresponding to amino acids 106-140 of mouse leptin significantly reduced food intake and body weight gain in female C57BL/6J ob/ob mice. These results suggested that leptin activity was localized in domains toward its C-terminus between residues 106-140. In the present study, 14 overlapping peptides encompassing the complete sequence of secreted mouse leptin were synthesized, and their effects on body weight and food intake in female C57BL/6 J ob/ob mice were assessed. When given as seven daily 1-mg i.p. injections, only peptides corresponding to amino acids 106-120, 116-130 and 126-140 caused significant reductions in body weight and food intake. These results confirmed our earlier study and suggest that in contrast to the domain encompassed by amino acids 106-140, the N-terminal of mouse leptin between amino acids 21-105 may not contain functional epitopes that can be utilized as lead compounds in the development of peripherally administered bioactive peptide analogs or nonpeptide mimetics of leptin, which may have potential usefulness in treatment of the energy imbalance associated with obesity.

Amino Acid Sequence↗

PubMed2000

Identification and expression of an allergen Asp f 13 from Aspergillus fumigatus and epitope mapping using human IgE antibodies and rabbit polyclonal antibodies.

The Aspergillus genus of fungi is known to be one of the most prevalent aeroallergens. On two-dimensional immunoblotting using patients' sera containing IgE specific for Asp f 13, an allergen with a molecular mass of 33 kDa and a pI of 6.2 was identified. This allergen was also present in A. fumigatus culture filtrates. Furthermore, the sequence of the Asp f 13 cDNA was identical to that for alkaline protease isolated from A. fumigatus and showed 42-49% identity of amino acids with two proteases from P. cyclopium and T. album and with the Pen c 1 allergen from P. citrinum. Asp f 13 coding sequences were expressed in Escherichia coli as a [His](6)-tagged fusion protein which was purified by Ni(2+)-chelate affinity chromatography. Recombinant Asp f 13 was recognized by rabbit polyclonal antibodies against Asp f 13 and by IgE antibodies from subject allergic to A. fumigatus. To identify and characterize the linear epitopes of this allergen, a combination of chemical and enzymatic cleavage and immunoblotting techniques, with subsequent N-terminal sequencing and mass spectrometry, were performed. At least 13 different linear epitopes reacting with the rabbit anti-Asp f 13 antiserum were identified, located throughout the entire molecule. In contrast, IgE from A. fumigatus-sensitive patients bound to three immunodominant epitopes at the C-terminal of the protein.

Allergens↗

PubMed1999

Anti-mitochondrial flavoprotein autoantibodies of patients with myocarditis and dilated cardiomyopathy (anti-M7): interaction with flavin-carrying proteins, effect of vitamin B2 and epitope mapping.

Vitamin B2 and flavin cofactors are transported tightly bound to immunoglobulin in human serum. We reasoned that anti-mitochondrial flavoprotein autoantibodies (alpha Fp-AB) present in the serum of patients with myocarditis and cardiomyopathy of unknown aetiology may form immunoglobulin aggregates with these serum proteins. However, immunodiffusion and Western blot assays demonstrated that the flavin-carrying proteins were not recognized by alpha Fp-AB. Apparently the flavin moiety in the native protein conformation was inaccessible to alpha Fp-AB. This conclusion was supported by the absence of an immunoreaction between the riboflavin-binding protein from egg white and alpha FP-AB. Intravenous application of vitamin B2 to rabbits immunized with 6-hydroxy-D-nicotine oxidase, a bacterial protein carrying covalently attached FAD, did not neutralize alpha Fp-AB which had been raised in the serum of the animals. FAD-carrying peptides generated from 6-hydroxy-D-nicotine oxidase by trypsin and chymotrypsin treatment were not recognized by the alpha Fp-AB, but those generated by endopeptidase Lys were. This demonstrates that the epitope recognized by alpha Fp-AB comprises, besides the flavin moiety, protein secondary structure elements.

Amino Acid Sequence↗

PubMed1998

Epitope mapping of the house-dust-mite allergen Der p 2 by means of site-directed mutagenesis.

Recombinant Der p 2, expressed in the baker's yeast Saccharomyces cerevisiae, was used as a tool to determine IgE- and monoclonal antibody (mAb)-binding sites on this allergen. For this purpose, mutant molecules were produced by application of site-directed mutagenesis. The amino-acid residues spanning cys21-cys27 and cys73-cys78 were deleted, thus preventing loop formation through disulfide bonds. Charged residues in three predicted antigenic sites (residues 45-48, 67 + 69, and 88-90) were replaced by alanine residues, IgE- and mAb reactivity to these mutants was compared to that to "wild type" Der p 2. Residues spanning cys73-cys78 were involved in the antigenic binding site for mAb alpha DpX. Mutations in the areas adjacent to this loop (i.e., 67 + 69 and 88-90) had similar effects on this mAb (10- to 20-fold decreases in reactivity were observed), supporting the suggestion that these areas are involved in this antigenic structure. The area of residues 45-48 was shown to be involved in an epitope for mAb 2B12. The reactivity of mAb 7A1 was influenced by substitutions of residues 45-48 as well as 88-90. Deletion of the residues spanning cys21-cys27 resulted in decreased reactivity to three mAbs (10E11, alpha DpX, and 7A1). From these observations, it may be concluded that binding of different mAbs is influenced by the same mutations and that the binding of single mAbs is influenced by two or more mutations scattered over the allergen molecule. These findings can point in two directions: minor amino-acid changes result in disruption of the overall conformation of the allergen, or distant sites are close together in the three-dimensional structure of the allergen. Decreased IgE reactivity was observed with all mutant molecules, varying between patients. The observed effects ranged from 5- to 1000-fold. Deletion of the amino-acid residues spanning cys21-cys27 and cys73-cys78 had the strongest effect on IgE reactivity, where decreases up to 1000-fold were observed. Such mutants might be useful tools to improve the safety of allergen-specific immunotherapy.

Allergens↗

PubMed2001

Epitope mapping using the X-ray crystallographic structure of complement receptor type 2 (CR2)/CD21: identification of a highly inhibitory monoclonal antibody that directly recognizes the CR2-C3d interface.

Complement receptor type 2 (CR2)/CD21 is a B lymphocyte cell membrane C3d/iC3b receptor that plays a central role in the immune response. Human CR2 is also the receptor for the EBV viral membrane glycoprotein gp350/220. Both C3d and gp350/220 bind CR2 within the first two of 15-16 repetitive domains that have been designated short consensus/complement repeats. Many mAbs react with human CR2; however, only one currently available mAb is known to block both C3d/iC3b and gp350/220 binding. We have used a recombinant form of human CR2 containing the short consensus/complement repeat 1-2 ligand-binding fragment to immunize Cr2(-/-) mice. Following fusion, we identified and further characterized four new anti-CR2 mAbs that recognize this fragment. Three of these inhibited binding of CR2 to C3d and gp350/220 in different forms. We have determined the relative inhibitory ability of the four mAbs to block ligand binding, and we have used overlapping peptide-based approaches to identify linear epitopes recognized by the inhibitory mAbs. Placement of these epitopes on the recently solved crystal structure of the CR2-C3d complex reveals that each inhibitory mAb recognizes a site either within or adjacent to the CR2-C3d contact site. One new mAb, designated 171, blocks CR2 receptor-ligand interactions with the greatest efficiency and recognizes a portion of the C3d contact site on CR2. Thus, we have created an anti-human CR2 mAb that blocks the C3d ligand by direct contact with its interaction site, and we have provided confirmatory evidence that the C3d binding site seen in its crystal structure exists in solution.

Animals↗

PubMed2005

Evaluation of human monoclonal antibody 80R for immunoprophylaxis of severe acute respiratory syndrome by an animal study, epitope mapping, and analysis of spike variants.

In this report, the antiviral activity of 80R immunoglobulin G1 (IgG1), a human monoclonal antibody against severe acute respiratory syndrome coronavirus (SARS-CoV) spike (S) protein that acts as a viral entry inhibitor in vitro, was investigated in vivo in a mouse model. When 80R IgG1 was given prophylactically to mice at doses therapeutically achievable in humans, viral replication was reduced by more than 4 orders of magnitude to below assay limits. The essential core region of S protein required for 80R binding was identified as a conformationally sensitive fragment (residues 324 to 503) that overlaps the receptor ACE2-binding domain. Amino acids critical for 80R binding were identified. In addition, the effects of various 80R-binding domain amino acid substitutions which occur in SARS-like-CoV from civet cats, and which evolved during the 2002/2003 outbreak and in a 2003/2004 Guangdong index patient, were analyzed. The results demonstrated that the vast majority of SARS-CoVs are sensitive to 80R. We propose that by establishing the susceptibility and resistance profiles of newly emerging SARS-CoVs through early S1 genotyping of the core 180-amino-acid neutralizing epitope of 80R, an effective immunoprophylaxis strategy with 80R should be possible in an outbreak setting. Our study also cautions that for any prophylaxis strategy based on neutralizing antibody responses, whether by passive or active immunization, a genotyping monitor will be necessary for effective use.

Amino Acid Substitution↗

PubMed2006

Differential epitope mapping of antibodies to PDC-E2 in patients with hematologic malignancies after allogeneic hematopoietic stem cell transplantation and primary biliary cirrhosis.

A unique characteristic of the autoimmune liver disease primary biliary cirrhosis (PBC) is the presence of high-titer and extremely specific autoantibodies to the E2 component of the pyruvate dehydrogenase complex (PDC-E2). Autoantibodies to PDC-E2 antigen have only been detected in patients with disease or in those who subsequently develop PBC. One exception has been a subgroup of patients with multiple myeloma (MM) who underwent allogeneic hematopoietic stem cell transplantation (HSCT) and received donor lymphocyte infusions (DLIs) after transplantation. These patients developed high-titer antibodies to a variety of myeloma-associated antigens, including PDC-E2, coincident with rejection of myeloma cells in vivo. To examine the specificity of autoantibodies to PDC in these patients, we screened sera from patients with MM, chronic leukemias, monoclonal gammopathy of unknown significance (MGUS), PBC, and healthy donors. Three of 11 patients with MM (27%) and 2 of 6 patients with chronic leukemias (33%) developed anti-PDC-E2 antibodies in association with DLI response; 2 of 12 (17%) patients in the MGUS pretreatment control population also had detectable anti-PDC responses. Interestingly, the epitope specificity of these PDC-E2 autoantibodies was distinctive, suggesting that the mechanisms leading to loss of tolerance in the transplantation patients are distinct from PBC.

Aged↗

PubMed1999

Epitope mapping of 10 monoclonal antibodies against the pig analogue of human membrane cofactor protein (MCP).

Pig membrane cofactor protein (MCP; CD46) is a 50 000-60 000 MW glycoprotein that is expressed on a wide variety of cells, including erythrocytes. Pig MCP has cofactor activity for factor I-mediated cleavage of C3b and is an efficient regulator of the classical and alternative pathway of human and pig complement. A panel of 10 monoclonal antibodies (mAbs) was collected from two different laboratories; all of these mAbs were raised against pig leucocytes and all recognized the same complex banding pattern on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of erythrocyte membranes. All were shown to be reactive with pig MCP and were divided into four groups of mutually competitive antibodies based on competition studies for membrane-bound MCP and for soluble MCP, the latter by surface plasmon resonance (SPR) analysis. The antigenic properties of membrane-bound and soluble MCP were similar, although some interesting differences were revealed. None of the 10 mAbs were cross-reactive with human MCP and only one showed cross-reactivity with leucocytes from a panel of large mammals - a weak cross-reactivity with a subset of dog leucocytes. All antibodies in one of the epitope groups and some in a second epitope group were able to block the functional activity of pig MCP, as measured by inhibition of MCP-catalysed C3 degradation by factor I.

Animals↗