Electrospray ionization mass spectrometry of recombinantly engineered antibody fragments

Mass spectrometry has been used to confirm the correct protein expression of Fab and F(ab')2 fragments of the humanized anti-p185HER2 antibody huMAb4D5. These data demonstrate that electrospray ionization mass spectrometry can be used routinely to measure the masses of purified proteins as large as 100 kDa, with an accuracy of < or = 0.02%. This level of accuracy is helpful in demonstrating the faithful translation and proper posttranslational modification of these proteins. Accurate and reliable mass assignments by electrospray ionization mass spectrometry are achieved by calibrating with protein mass standards, optimizing resolution, and using methods to improve sample purity. On-line reversed-phase high-performance liquid chromatography/mass spectrometry has been employed to improve sample purity and thereby increase sensitivity. Disulfide reduction to yield the component subunits provides additional confirmation of the correct amino acid sequence with greater absolute mass accuracy. A volatile reducing agent such as tributylphosphine provides a convenient method to generate subunits for mass measurement while requiring little or no further sample purification.

Characterization of a synthetic 37-residue fragment of a monoclonal antibody against herpes virus by capillary electrophoresis/electrospray (ionspray) mass spectrometry and 252Cf plasma desorption mass spectrometry

A peptide comprising 37 amino acids of the antigen binding site of a monoclonal antibody directed against glycoprotein D of herpes simplex virus was synthesized. The synthetic peptide and the impurities formed in the synthesis were characterized by capillary electrophoresis/ionspray mass spectrometry and by 252Cf plasma desorption-time of flight mass spectrometry. The measured average molecular mass of the synthetic peptide was 4627.16 Da, which was only 0.08 Da higher than the calculated value (4627.08 Da). The plasma desorption mass spectrum of the synthetic peptide showed a protonated molecule at m/z 4624.1, which was 4 Da lower than the calculated one (4628.09 Da). The amino acid sequence of the peptide was confirmed in part by electrospray (ionspray) mass spectrometry using a high nozzle skimmer voltage difference. Five impurities were separated and identified by capillary electrophoresis/mass spectrometry and two of them also appeared in the plasma desorption mass spectrum.

Affinity probe capillary electrophoresis: analysis of recombinant human growth hormone with a fluorescent labeled antibody fragment

A new highly sensitive microscale analytical procedure called affinity probe capillary electrophoresis (APCE) is presented. One of the two species, which can form a biospecific complex, is labeled with a fluorescent dye. The affinity probe is used to detect the analyte as a complex after the separation of the excess free probe by capillary electrophoresis. As an example of this approach, an FAB' fragment of a mouse monoclonal antibody (anti-human growth hormone) was labeled with tetramethylrhodamine-iodoacetamide at a hinge region thiol group. Samples were mixed with the purified labeled antibody fragment, and the associated complex was separated by capillary isoelectric focusing with detection by laser-induced fluorescence. In these preliminary results, methionyl recombinant human growth hormone (met-rhGH) could be successfully determined down to detection levels of approximately 5 x 10(-12) M. Mono- and dideamidated variants of met-rhGH were detected simultaneously with the nondeamidated form of the antigen as separate peaks.

Malignant lymphoma of Waldeyer's ring. A histological and immunohistochemical study

The histopathological and immunohistological features of non-Hodgkin's lymphoma limited to the Waldeyer's ring were studied in 22 Japanese patients using a panel of T- and B-cell markers on paraffin-embedded sections. All cases showed a diffuse growth pattern. Twenty cases were B-cell lymphomas and two were T-cell lymphomas. In contrast to the primary malignant lymphomas of the nasal cavity and paranasal sinuses, in which T-cell neoplasms are more frequently seen, the majority of the primary Waldeyer's ring lymphomas were B-cell neoplasms. Sixteen of the 20 cases of B-cell lymphoma were centroblastic lymphomas, and the monomorphic variant comprised the majority of these; the other three B-cell lymphomas were immunocytomas. Two of the T-cell lymphomas showed morphological features of angiocentric lymphomas.

Primary non-Hodgkin lymphomas of the CNS. Classification, tissue reaction and proliferative activity

Primary cerebral lymphomas (PCL) are rare tumors, which, however, occur at increasing frequency. From 1980 to 1991, 44 PCL were histologically diagnosed from immunocompetent patients in our department. According to the updated Kiel Classification, 13.5% of the tumors were of low malignancy (4 immunocytomas, 2 centroblastic-centrocytic), and 79.5% were highly malignant B-cell lymphomas (26 centroblastic, 2 Burkitt-type, 3 immunoblastic, 4 unclassified). Two T-cell lymphomas and one large-cell anaplastic lymphoma were found as well. A reactive tissue infiltrate consisting of varying amounts of small T-cells and tissue macrophages was present in all B-cell lymphomas. PCNA-indices reflected the histological grade, with mean counts of 19.5% in low grade neoplasms and 59.3% in high grade ones. No correlation was found to exist between PCNA-index and patient survival.

Leukaemic intermediate lymphocytic lymphomas: analysis of twelve cases diagnosed by morphology

Twelve cases of leukaemic intermediate diffuse lymphocytic lymphoma (ILL), diagnosed by morphology, were analysed. The morphology of the ILL cells was so typical that it allowed ready distinction from chronic lymphocytic leukaemia (CLL) and other related B cell disorders. All cases were of B derivation, had strong mu and chi or lambda immunoglobulin (Ig) staining, were CD5 and FMC7 positive and CD10 negative. Cytogenetic abnormalities were found in 8 patients all having t(11;14)(q13;q32). DNA analysis revealed a relatively high incidence of hypoploidy. At diagnosis all the patients (9 males, 5 females; median age 68) had a low degree of absolute lymphocytosis but the disease was advanced and mostly widespread. The course of the disease appears to be aggressive and incurable with conventional combination chemotherapy.

Extramedullary plasmacytoma of the thyroid, associated with follicular colonization and stromal deposition of polytypic immunoglobulins and major histocompatibility antigens. Possible categorization in MALT lymphoma

A 78-year-old woman complaining of a neck mass underwent right hemithyroidectomy. The 7 x 6 cm thyroid tumor consisted predominantly of mildly atypical, epithelial membrane antigen-positive plasma cells and scattered lymphoid follicles. Features of follicular colonization (plasma cell infiltration into germinal centers) were noted. Numerous CD45RO-positive reactive T cells and a smaller number of CD20-positive blast-like B cells were also distributed among the plasma cell infiltrate. IgG, kappa-type monoclonality with J-chain reactivity was identified in the plasma cells, including those in the lymphoid follicles. The association of pre-existing lymphocytic thyroiditis was confirmed histologically in the non-tumorous thyroid tissue. The tumor exhibited deposition of reticulin fiber-rich, amorphous eosinophilic substances, provoking pronounced foreign body reactions. The deposit, polytypically immunoreactive for immunoglobulin gamma-, mu-, kappa- and lambda-chains, beta 2-microglobulin and HLA-DR, was scarcely reactive upon amyloid staining, and consisted ultrastructurally of electron-dense, non-fibrillar material and entrapped collagen fibers. Multiple myeloma was ruled out by laboratory, histologic and clinical examinations. The possible categorization of this extramedullary plasmacytoma of the thyroid within low-grade B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) is discussed.

IgG subclass imbalance in children with acute lymphoblastic leukemia receiving maintenance chemotherapy

Serum levels of IgG subclasses were measured in 18 children with acute lymphoblastic leukemia (ALL) receiving maintenance chemotherapy and in 36 age-matched controls in order to attempt to analyse the effects of chemotherapy. The IgG subclasses were measured by enzyme linked immunosorbent assay. Serum IgG1, IgG2 and IgG4 levels in the patients were significantly (p less than 0.01, p less than 0.005, p less than 0.005) lower than in the controls, but serum IgG3 levels in patients were as high as in controls. Suppression on IgG2 and IgG4 were more profound than IgG1. In six children, the levels of the IgG subclasses were measured at diagnosis, during maintenance chemotherapy and one year after cessation of chemotherapy. The levels of the four IgG subclasses at diagnosis and after cessation of chemotherapy were as high as those in control children except for the IgG4 levels in the post-chemotherapy group. IgG2 and IgG4 may be more susceptible to suppression by chemotherapy than IgG1 and IgG3 may not be suppressed by chemotherapy.

[IgG1-IgG4 subclasses in the cerebrospinal fluid and blood serum and their synthesis in the central nervous system in multiple sclerosis]

IgG1, IgG2, IgG3 and IgG4 subclasses were detected in cerebrospinal fluid and sera from 32 patients with MS. The CSF levels of IgG1 and IgG3 subclasses in MS patients were significantly higher than those of controls. There were no statistical differences between the values of IgG subclasses in MS and control sera. The IgG1 and IgG3 indices were significantly higher in MS patients than in controls showing that among four IgG subclasses IgG1 ang IgG3 were synthesized in the central nervous system of patients with MS. The elevation of IgG1 and IgG3 indices in MS patients was found more frequently (in about 90% of patients) than the elevation of the general IgG index (in 72% of patients).

Analytical control procedures of immunoreactivity for IgG and Fab fragments specific to haptens

This study investigates immunoreactivity control procedures, i.e., specificity, affinity constant (Ka), and specific active binding sites (SABS), for polyclonal anticolchicine, monoclonal antidigitoxin IgG and Fab fragments, and antidigoxin Fab fragments (Digidot). Preliminary control procedures for IgG and Fab fragment purity indicated that all reagents were immunologically pure. All IgG and Fab fragments exhibited similar cross-reactivity and Ka. No decrease in percentage of Fab fragment SABS was observed after papain cleavage of anticolchicine and antidigitoxin IgG. Nevertheless, only 4.3 +/- 1.2% of nonimmunopurified anticolchicine polyclonal Fab fragments and 76.2 +/- 2.3 to 88.7 +/- 2.5% of different batches of immunopurified anti-digoxin Fab (Digidot) were active, the latter percentage being in the range of the 85% specified by the manufacturer. Only 58 +/- 3% of digitoxin-specific monoclonal IgG was active and 67 +/- 7% of its Fab fragments. Results show the importance of determining the ratio of SABS to presumed total specific binding sites for pharmaceutical monoclonal and polyclonal antibody preparations against haptens.

Isolation and amplification of human IgE Fd encoding mRNA from human peripheral blood lymphocytes

In order to establish the feasibility of applying recombinatorial library technologies to investigate human in vivo IgE responses, and as a pre-requisite of recombinatorial library construction, we have attempted to determine workable peripheral blood sample volumes required for isolation of mRNA for polymerase chain reaction (PCR) amplification of human IgE Fd encoding sequences. Cells secreting chimeric human IgE monoclonal antibody specific for the hapten NIP were used to establish the conditions for specific amplification of C epsilon 1 domain and Fd encoding sequences, as determined by Southern hybridisation. Amplification of C epsilon 1 domain sequences could be achieved using as few as ten cultured cells as the source of RNA. Specific IgE+ B cell enrichment using immuno-magnetic particles prior to RNA extraction was, however, required to obtain amplification of IgE C epsilon 1 and Fd fragments from lymphocytes prepared from 40 ml human peripheral blood. IgG1+ B cell enrichment from similar samples was not required for detectable amplification of human C gamma 1 cDNA sequences. However, this procedure improved amplification efficiency. Optimisation of methods to separate specific B cell populations, or specific RNA/cDNA sequences, will facilitate in vitro generation of human IgE Fab fragments from peripheral blood.

[Oligoclonal bands of four IgG subfractions and IgM and IgA in the serum and cerebrospinal fluid of friends with multiple sclerosis]

Using the methods of isoelectric focusing and immunoblotting the CSF and serum immunoglobulins were analysed in 47 patients with multiple sclerosis and 57 patients with other neurological diseases. The oligoclonal bands were found in the IgG fraction in 42 multiple sclerosis (ms) patients and 13 controls. The percent proportion of oligoclonal bands in various IgG subfractions was similar in both groups and was: 66% and 61% respectively for IgG1, 22% and 22% for IgG3, 12% and 17% for IgG2. In no case was IgG4 found. Additionally sporadic oligoclonality of IgA and IgM in CSF was found. Positive results were obtained in 2 and 2 cases with ms, and in one control case (only IgA), among controls the oligoclonal bands were found most frequently in neuroinfections (38.5%) and polyneuropathy (20.5%).

Carcinoma-associated monoclonal antibodies in head and neck carcinoma. Immunohistochemistry and biodistribution of monoclonal antibodies 175F4 and 175F11

Monoclonal antibodies (mAbs) 175F4 (IgG1) and 175F11 (IgG2a), originally raised against the human mammary carcinoma cell line (ZR-75-1), react with a carcinoma-associated antigen in both adenocarcinomas and squamous cell carcinomas of different origins. Immunohistochemically, the mAbs exhibited reactivity with 42 out of 43 squamous cell carcinomas of the head and neck. Normal squamous epithelia were also reactive with the antibodies in the basal and suprabasal cell layer. 111In 175F4 F(ab')2 fragments localized a squamous cell carcinoma xenograft (HT-6) in nude mice with low blood pool activity, indicating a potential clinical usefulness for staging of squamous cell carcinomas in the head and neck.

Immobilization of Fv antibody fragments on porous silica and their utility in affinity chromatography

Recent advances in molecular biology have allowed antibody binding domains to be cloned and expressed in Escherichia coli. The use of Fv antibody fragments as ligands in immunoaffinity chromatography is reported. Fv fragments specific for hen-egg lysozyme were immobilized on porous silica and used to recover antigen from spiked serum in a single step. Comparison with a conventional immunoadsorbent (whole antibodies immobilized on silica) showed the Fv-silica to have a fivefold superior capacity. Analysis of sectioned Fv-silica particles by immunoelectron microscopy indicated that captured antigen was evenly distributed throughout the internal porous structure of the particle.

Inhibition of neutrophil chemotaxis by elastase-generated IgG fragments

IgG1 is cleaved in vitro by granulocyte elastase into Fc and Fab fragments. The elastase-specific Fc fragment has been previously detected in vivo. Biological activity of the fragments has been described in modulating neutrophil oxidative metabolism and enzyme release. To investigate further effects granulocyte chemotaxis (CT) was tested. The CT was assayed in Boyden chambers and the chemotactic index (CI) was calculated which represents the mean distance travelled by the activated cells. Stimulation of leucocyte CT by casein, activated serum and FMLP gives maximal values of delta CI = 46.7, 26.4 and 7.2 microns, respectively. Native IgG1 and the elastase-produced IgG fragments do not stimulate leucocyte CT. FMLP-stimulated CT is specifically inhibited by the elastase-produced Fc fragments. Addition of 7 nmol Fc to stimulus concentrations of 16 to 125 nM FMLP results in total inhibition of chemotaxis demonstrated by CI values which are lower than those for unstimulated cells. The inhibition of CT is concentration dependent in the range of 2 to 7 nmol Fc/10(6) PMN. Number and affinity of FMLP receptors are not influenced by Fc fragments, so Fc binds neither to FMLP nor the FMLP receptor. CT stimulated by casein shows a large portion of chemokinesis. Only at suboptimal casein concentrations do Fc and IgG have an inhibitory effect on CT (0.63 mg casein/ml, 10 nmol peptide/10(6) PMN). C5a-stimulated CT is not influenced by IgG or IgG fragments which indicates that the samples are not cytotoxic. So the FMLP and casein-stimulated CT is specifically inhibited by the elastase-produced Fc fragments in a low concentration range.

A ten-residue fragment of an antibody (mini-antibody) directed against lysozyme as ligand in immunoaffinity chromatography

The interaction between an antibody molecule and a protein antigen is an example of "natural" protein modelling. Amino acids of the antigen-binding site consisting of three hypervariable segments (L1, L2, L3) of the light (L) and three (H1, H2, H3) of the heavy (H) chain of an antibody molecule interact with amino acids present in an epitope of a protein. A ten-residue peptide was synthesized with an amino acid sequence analogous to the hypervariable L3 segment of a monoclonal antibody directed against lysozyme. The peptide was immobilized on CH-Sepharose 4B and the affinity adsorbent was used to purify lysozyme added to a detergent extract of insect cells infected with a recombinant baculovirus. This methodology may also be applicable to other antigen-antibody combinations, in immunoaffinity chromatography for selective purification of a protein or in an immunosensor for detection of a protein.

Chromatographic methods for large-scale preparation of immunoglobulin G2a monoclonal antibodies Lym-1 and TNT-1 F(ab')2 fragments

Lym-1 and TNT-1 are two murine immunoglobulin G2a monoclonal antibodies (MAbs) which have been used for clinical trials in cancer patients. This paper describes methods for large-scale preparation of F(ab')2 fragments from 50 mg to 4 g of MAbs Lym-1 and TNT-1. Digestion of MAbs with pepsin was optimized and performed at pH 3.8, a pepsin/antibody ratio of 1:250, and 3-4 h of incubation at 37 degrees C. The F(ab')2 fragments were purified by tandem column procedures using fast protein liquid chromatography. Quality control analyses of the products included protein purity, isoelectric point, immunoreactivity, and endotoxin level. The results revealed that the chromatographic procedures are practical, simple, and effective, and can be used to produce gram quantities of clinical-grade F(ab')2 fragments for the diagnosis of cancer in patients.

[The protective activity of 2 normal immunoglobulin preparations for intravenous administration in experimental Pseudomonas aeruginosa infection]

The antibody levels in 18 batches of the preparations of human immunoglobulin, Immunovenin and Immunovenin-Intact, for intravenous injection were determined in the enzyme immunoassay with the use of the mixture of P. aeruginosa lipopolysaccharide antigens of seven immunotypes. The average antibody titers in these preparations were identical. The preparations were found to have protective action against P. aeruginosa experimental infection in mice.

Shared idiotypic determinant in mono- and polyclonal anti-phospholipid antibodies with lupus anticoagulant activity

Of 42 purified human myeloma proteins tested, two (IgG3 Her and IgM Mag) were found to possess strong lupus anticoagulant (LA) and anti-cephalin activity, as assessed by a dilute activated partial thromboplastin time (dAPTT) and ELISA test, respectively. For these proteins, we confirmed the observation reported by others that LA activity is present in the antigen-binding (Fab) portion of the immunoglobulin molecule. Rabbit anti-idiotype antibodies against IgG3 Her inhibited the anti-cephalin activity of this protein, suggesting that the anti-cephalin activity of IgG3 Her depends on the hypervariable part of the immunoglobulin and thus most probably is a true antigen-antibody reaction. The anti-Her idiotype antibodies were also able to bind to and inhibit the anti-cephalin activity of IgM Mag. ELISA binding and inhibition experiments showed that the anti-idiotype antiserum contained at least two sets of anti-idiotypes; one set that recognizes a cross-reactive idiotype shared by IgG3 Her and IgM Mag, and another set that seems to be unique to the immunizing protein IgG3 Her. Both sets of anti-idiotype antibodies also bound weakly to polyclonal (patient) IgG, indicating an idiotypic cross reaction.

Report of a primary lymphoma of the conjunctiva. A lymphoma of MALT origin?

A case of primary conjunctival lymphoma is reported herein. A 47-year-old woman presented with an indolent salmon-coloured tumour of the lower epibulbar conjunctiva. Histologically, we found a lymphoid infiltrate in the epithelium and subepithelium consisting of two components. One component was characterized by centrocytic-like cells and the other by lymphocytic, plasmacytoid and plasma cells. An immunohistological study demonstrated a light chain restricted immunoglobulin expression of the tumour cells as well as some residual polytypic follicles exhibiting reticular dendritic cells. Tumour cell proliferation was associated with a T cell reactive population. A comprehensive investigation (in particular an orbital scan) did not demonstrate any other localization of this lymphoma. Such a lesion raised the question of a possible MALT origin, by analog with MALT-lymphomas of the gastrointestinal tract described by Isaacson and colleagues.

Inhibition of neutrophil oxidative burst by elastase-generated IgG fragments

IgG1 is cleaved in vitro by granulocyte elastase into Fc, Fab and Fabc fragments. The cleaved products have been isolated by a series of chromatographic procedures and characterized with regard to molecular mass and isoelectric point. The Fc fragment has been previously shown to express at its N-terminal site a neoantigen which is specific for elastase (Kolb, G., Eckle, I., Heidtmann, H.-H., Neurath, F. & Havemann, K. (1988) Scand. J. Rheumatol. S75, 179-189). The production of superoxide radical anions in prestimulated neutrophils is inhibited dose-dependently by the elastase-generated Fc and Fabc fragments. Native IgG1 and Fab fragments show no inhibitory effect, nor do papain-generated Fc fragments. The degree of inhibition depends on the stimulus applied: half-maximal inhibition is obtained by 6 microM Fc after stimulation with 4 beta-phorbol and 2.4 microM after stimulation with fMet-Leu-Phe; neutrophils stimulated with serum-activated zymosan are not inhibited by IgG fragments. The effect of Fc is purely cellular; no inhibition of O2 generation can be produced by applying Fc to the xanthine oxidase/xanthine system. The fragments have no effect on the activation or activity of crude NADPH oxidase, which is the O2-forming enzyme system of neutrophils. Possible mechanisms are discussed by which Fc acts on stimulated neutrophils.

Influence of IgE fragments on IgE determination

IgE fragments were detected by polyclonal and monoclonal anti-IgE antibodies using Western blot techniques and immunoassays. Other antibodies detected only intact IgE molecules. In the presence of IgE fragments, higher IgE levels were estimated, depending on the epitope specificity of the antibodies used in the IgE determination assays. IgE fragments have been found together with intact IgE in isolated material from different human sera and also from culture supernatant of an IgE-producing cell line. Our data demonstrate that IgE fragments may be assessed and represent a potential pitfall in diagnostic IgE determinations.

Kinetics of digoxin and anti-digoxin antibody fragments during treatment of digoxin toxicity

Anti-digoxin antibody fragments (ADAF, 80 mg) were infused intravenously to successfully treat severe digoxin toxicity in an 82 year old woman. During treatment, total and free digoxin were determined using an Abbot TDX analyser and an ultrafiltration technique. ADAF were measured by an enzyme-linked immunosorbent assay. By 1 h after ADAF, total serum digoxin concentrations had risen 12-fold from a pretreatment level of 15.4 nmol l-1 but free digoxin fell from 10 to 0.1 nmol l-1, indicating greater than 99.9% digoxin binding to ADAF. However, the low free levels had rebounded to 7.7 nmol l-1 by 12 h, but despite this rise the patient's condition had improved. A serum ADAF/digoxin molar ratio of around five was associated with the low concentration of free digoxin at 1 h, while at later times with ratios roughly between 3 and 4, the free digoxin concentrations ranged between 2.0 and 7.7 nmol l-1. ADAF were mainly confined to the plasma during the first hour, but subsequently distributed into an apparent volume of 193 ml kg-1. The elimination half-lives of ADAF and total digoxin were 96 and 55 h, respectively. More than 50% of the estimated digoxin load had been excreted in the urine by 5 days; for ADAF the equivalent figure was only about 3%. Renal and/or bacterial degradation may have contributed to the low detection of urinary ADAF.