Antibodies to small molecules: biological and clinical applications

Effects of antibodies induced by a conjugate vaccine on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone absorptive transport, metabolism, and proliferation of human lung cells

One of the most abundant and potent lung carcinogen is the nicotine-derived tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The monoclonal antibody P9D5 induced with a NNK-conjugate vaccine was used to investigate the ability of NNK-specific antibodies to modulate NNK-induced adverse effects as well as its absorptive transport and metabolism in two lung cancer cell lines (Calu-3 and NCI-H82). Transport experiments in Calu-3 cells with a 50-fold molar excess of apical P9D5 increased the recovery of coadministered apical NNK, with a concomitant decrease in NNK transepithelial transport of more than 50% compared to controls. In contrast, basolateral P9D5 did neither influence transepithelial transport of NNK nor its disappearance from the apical compartment. Calu-3 cells were also found to reduce NNK to NNAL and a 65-fold molar excess of NNK-specific antibody inhibited this metabolic conversion by 46 and 54% compared to irrelevant control antibody after 48 and 72 hr, respectively. The biological relevance of NNK redistribution by antibody was demonstrated by reversion of NNK-induced cell proliferation in NCI-H82 cells. Repartitioning of tobacco carcinogens by antibody may reduce their early effective peak concentrations in susceptible target organs and thus relieve overloaded local DNA repair mechanisms and diminish carcinogen-induced cell proliferation. These in vitro data therefore suggest that a prophylactic antibody response may be associated with a reduced risk of cancer.

A vaccine for hypertension based on peptide AngI-R: a pilot study

AIMS

We aim to modulate the renin-angiotensin system (RAS) by active immunization against angiotensin I/II, potentially by a novel type of peptide--'AngI-R' for the treatment of hypertension.

METHOD

27 spontaneous hypertensive rats (SHRs) were randomly divided into 3 groups (n=9). Effect of AngI-R on systolic blood pressure of SHRs was determined by its subcutaneous injection into SHRs with anti-angiotensin peptide AngI-R, captopril, physiological salt solution in the same schedule. Systolic blood pressure was monitored by tail-cuff arterial blood pressure measurement method and then calculated from the average of three measurements in each animal at a desired time (0, 4, 8, 16W). AngI, AngII and anti-AngI antibody were detected by ELISA and western blotting method. At the end, the pathologic changes in different organs of SHRs were observed.

RESULT

The results exhibited a marked effect to lower the systolic blood pressure (-15 mmHg) of SHRs after subcutaneous injection with peptide AngI-R. The anti-hypertensive effect lasted for over 1 month. The level of AngI and AngII in the vaccinated group, after administration of AngI-R was lower than the one in the control group and the pre-administered group. The anti-AngI/II antibody titre in the experiment group significantly increased.

CONCLUSION

The peptide AngI-R was able to decrease the blood pressure of SHRs. The peptide AngI-R induced an immune response to inhibit AngI and AngII, resulting in the decrease in blood pressure in SHRs.

Modulation of carcinogen bioavailability by immunisation with benzo[a]pyrene-conjugate vaccines

Benzo[a]pyrene (B[a]P) conjugate vaccines based on ovalbumin, tetanus toxoid and diphtheria toxoid (DT) as carrier proteins were developed to investigate the effect of specific antibodies on the bioavailability of this ubiquitous carcinogen and its metabolites. After metabolic activation of this prototype carcinogen, B[a]P forms DNA adducts which initiate chemical carcinogenesis. B[a]P-DT conjugate induced the most robust immune response. The antibodies reacted not only with B[a]P but also with the proximate carcinogen 7,8-diol-B[a]P. Antibodies modulated the bioavailability of B[a]P and its metabolic activation in a dose-dependent manner by sequestration in the blood. Our results showed that this immune prophylactic strategy influences the pharmacokinetic of B[a]P and further studies to investigate their effects on chemical carcinogenesis are warranted.

Evaluation of two carrier protein-angiotensin I conjugate vaccines to assess their future potential to control high blood pressure (hypertension) in man

AIMS

We aim to modulate the renin-angiotensin system (RAS) by active immunization against angiotensin I hormone (AI), potentially providing a novel conjugate vaccine treatment for hypertension in man.

METHODS

Immunization studies in rat and human subjects compare the effectiveness of tetanus toxoid (TT) and keyhole limpet haemocyanin (KLH) vaccines for immunotherapy following conjugation with an AI peptide analogue (AI). Cardiovascular responses were assessed in immunized rats and human subjects (two-dose trial only), following increasing i.v. infusions of either AI or angiotensin II hormone (AII).

RESULTS

The AI-TT and AI-KLH conjugate vaccines induced an equivalent immune response, and inhibition of the pressor effects to exogenous AI in rats. Single-dose clinical trials with both conjugate vaccines only resulted in an immune response to the KLH carrier protein. A two-dose clinical trial of AI-KLH conjugate vaccine resulted in a significant immune response to AI. A shift in diastolic blood pressure (DBP) dose-response was demonstrated following challenge with AI and AII for the study volunteer showing the largest anti-AI IgG induction.

CONCLUSION

KLH was shown to be a suitable alternative to TT as a carrier protein for AI, thus supporting continued evaluation of our AI-KLH conjugate vaccine for treatment of hypertension in man.

Investigation into suitable carrier molecules for use in an anti-gonadotrophin releasing hormone vaccine

Gonadal function can be controlled through immunoneutralisation of gonadotrophin releasing hormone (GnRH), with an analogue, GnRH-glycys, linked to a carrier molecule and an appropriate adjuvant. In this study, four different types of carrier molecule were investigated: (a) single and branched amino acid polymers--[poly-(D-glu, D-lys) and poly-(phe, glu)-poly(DL-ala)-poly(lys)]; (b) bacterial toxoids--diphtheria (DT) and tetanus (TT); (c) synthetic T-helper epitopes--derived from malarial circumsporozite protein (CS) and measles virus fusion protein (MVF); and (d) thyroglobulin (Thy)--a large protein. The effect of non-ionic surfactant vesicles (NISV) and an aluminum hydroxide based adjuvant (alum), was also examined. Although good antibody responses were achieved with GnRH-glycys-DT, GnRH-glycys-TT and GnRH-glycys-Thy, adsorbed onto alum and the dimerised synthetic T-helper epitope constructs, incorporated into NISV, a critical antibody titre was necessary to result in morphological changes in the gonads and complete suppression of spermatogenesis. This was only achieved with tetanus toxoid and the dimerised T-helper epitopes.

Immunological studies using monoclonal antibodies for detection of low dalton marine toxins

The general methodology employed in the development of an immunological assay system is initially described. These include: (a) the methods and reagents used for coupling low dalton epitopes; (b) selection of appropriate immunogenic carriers; (c) mode of administration and choice of animal; and (d) the method of assessing the antibody produced. The background and methodology, using ciguatoxin as a model, are presented. The stick enzyme immunoassay (S-EIA) has proven of value to evaluate implicated fish for verification of ciguatera poisoning and for screening of fish associated with ciguatera prior to consumption. No false negatives have occurred with the stick enzyme immunoassay system to date.

Monoclonal antibody to amphomycin. A tool to study the topography of dolichol monophosphate in the membrane

Understanding the topographical orientation of dolichol monophosphate (Dol-P) in the membrane of the endoplasmic reticulum (ER) is of utmost importance for studying the regulation of asparagine-linked protein glycosylation in eukaryotic cells. This was practically impossible due to the nonavailability of a suitable probe. Recent studies on the specific interaction between a lipopeptide, amphomycin, and Dol-P, provided an insight to develop a monospecific antibody to amphomycin which could recognize the amphomycin-Dol-P complex in order to detect Dol-P immunocytochemically in the ER membrane. We report herein the successful production of a monoclonal antibody to amphomycin. The antibody belongs to the IgG+IgM subclasses and is specific for amphomycin when analyzed by the enzyme-linked immunoassay and immunoblot procedures. The antibody recognizes with equal potency both the native amphomycin and also mild acid-hydrolyzed amphomycin from which N-terminal fatty acylated aspartic acid has been removed. Preincubation of amphomycin with the antibody partially reduced the inhibitory action of amphomycin on dolichol phosphate mannosyltransferase (EC 2.4.1.83). Furthermore, exposure of capillary endothelial cells to amphomycin, followed by the monoclonal antibody to amphomycin, followed sequentially by staining with FITC-conjugated goat anti-mouse IgG and examination under a fluorescent microscope gives intense fluorescence at the perinuclear region of the cell with a structure reminiscent of the ER.

Production and characteristics of strain common antibodies against a synthetic polypeptide corresponding to the C-terminal region of potato virus Y coat protein

Comparing the predicted amino acid sequence between two Japanese potato virus Y (PVY) strains, necrotic strain and ordinary strain, it was found that the C-terminal regions (H2N-HTTEDVSPSMHTLLGVKNM-COOH) of the coat proteins in the two strains were completely conserved. The conserved amino acid sequence was also found in the C-terminal region coat protein of PVY-36, a strain which did not react with monoclonal antibodies specific to the necrotic and the ordinary strain respectively. Antibodies were produced against a synthetic polypeptide PVY-C19 consisting of 19 amino acids, which correspond to the C-terminal region of the coat protein, using 4 coupling combinations of polypeptide PVY-C19 to protein carriers. Carrier-free polypeptides and those coupled to ovalbumin with ECDI (ethyl-dimethylaminopropyl carbodiimide) produced high titer of antibodies and detected PVY strains from PVY-infected plants by Western blot analysis and by ELISA.

Antibodies against the cystic fibrosis transmembrane regulator

Rabbit polyclonal antibodies have been raised against high-performance liquid chromatography purified synthetic peptides corresponding to two discrete regions of the cystic fibrosis transmembrane regulator (CFTR) protein: the R-domain (residues 785-796) and the extreme COOH-terminus (residues 1467-1480). Antibodies (Ab) to each of these peptides were affinity purified either by passage over a peptide-derivatized agarose matrix (Ab 785) to produce monospecific polyclonal antibodies or by protein A affinity chromatography to purify the immunoglobulin G1 fraction free of other serum proteins (Ab 1467). These antibodies recognize a candidate CFTR protein in the colonic cell line T84, as determined by Western blot analysis and by immunoprecipitation and labeling of the precipitate with [gamma-32P]ATP in the presence of protein kinase A. Both antibodies precipitated CFTR-related polypeptides from four mammalian cell types (HeLa, Bsc-40, HEp-2, and Chinese hamster ovary cells) transfected with the full-length CFTR cDNA clone using a vaccinia T7 protein expression system. Similar results were observed using a yeast CFTR expression system. In each case the Mr values of the bands observed were consistent with that expected for the CFTR protein. These antibodies should be useful probes for the immunocytochemical localization, immunoaffinity purification, and ultimately the functional characterization of the CFTR protein.

Conjugation of synthetic peptides to proteins: quantitation from S-carboxymethylcysteine released upon acid hydrolysis

A method described here for conjugating synthetic peptides to carrier proteins provides a convenient method for determining peptide-to-carrier protein ratios. N-Bromoacetyl-containing peptides are reacted in situ with carrier proteins in which the disulfide bonds were reduced with tri-n-butylphosphine. At pH 7-8 and ambient temperature, the newly formed sulfhydryl groups of the carrier protein react exclusively with the bromoacetyl mokiety of the peptide to form conjugates having stable thio ether linkages. Acid hydrolyses of these conjugates release S-carboxymethylcysteine in amounts proportional to the amounts of peptides conjugated and thus allow determination of peptide-to-protein ratios.

Monoclonal antibodies against the presynaptic calcium channel antagonist omega-conotoxin GVI A from cone snail poison

Monoclonal antibodies have been prepared against omega-conotoxin GVI A, a peptide isolated from marine snails of the genus Conus (Conus geographus and Conus magus). This toxin is a blocker of select presynaptic Ca2+ channels in the central nervous system. Antigenic omega-conotoxin GVI A was synthesized as a covalent conjugate with bovine serum albumin and injected s.c. An ELISA assay combined with a competitive inhibition assay was used to select and characterize monoclonal antibodies able to recognize and bind the free toxin. Several of the antibodies were found to block omega-conotoxin GVI A inhibition of 45Ca transport into rat brain synaptosomes and to block omega-conotoxin GVI A binding to membranes from the same preparation. The antibodies recognize native, synthetic toxin, and are useful for analysis of toxin in biological fluids.

Evidence for human antibodies that recognize an aflatoxin epitope in groups with high and low exposure to aflatoxins

Antibody activity against an aflatoxin epitope has been detected in serum from individuals who live in Kenya and who experience high exposure to aflatoxin B1. The activity was higher than in Danish people. The highest antibody activity was found in individuals who were recently exposed to aflatoxin B1. The ratio between IgG and IgM activities was higher in individuals with a high antibody titer. The specificity of the antibody activity differed in the serums obtained from Danish and Kenyan persons ("Danish" and "Kenyan" serum, respectively). The activity in Danish serum was inhibited by an aflatoxin-like substance isolated from human urine, whereas aflatoxin B1 did not inhibit the activity. In contrast, the activity in Kenyan serum was not inhibited by the aflatoxin-like substances. Therefore, the presence of antibodies against aflatoxin in humans indicates exposure to aflatoxin or aflatoxin-antigenic material. However, the biological consequences of these antibodies remain unknown.

Immunotoxicotherapy: present status and future trends

Immunotoxicotherapy (ITT) is currently used in humans for the treatment of snake venom and cardiac glycoside poisoning. Other toxins have been studied in animals or in vitro to assess their suitability as candidates for detoxification by specific antibodies. Testing conditions are often empirical suggesting that numerous improvements need to be introduced in ITT. Basic mechanisms in ITT include three phases: sequestration, extraction and elimination. The pharmacokinetics of these three phases depend on the type of antidotal binding site (ABS). IgG or its Fab2, Fab or Fv fragment are the possible choices. The Fab fragment is the most frequently used ABS because of its diffusion properties in the peripheral compartments and its renal excretion by glomerular filtration. Toxicokinetic and pharmacokinetic considerations indicate that the dosage cannot be satisfactorily calculated from stoichiometric principles. Study of the toxin dose-lethality curves shows that ABS dosage can be lowered. Moreover, clinical data reveal that some FAb fragments are directly eliminated without acting on toxin molecules. In order to counteract these drawbacks, a compromise between dosage and duration of infusion is suggested. Other improvements will stem from advances in immunologic methodology. Monoclonal and chimeric antibodies are new tools that will help resolve the clinical problems of immunogenicity and adverse reactions associated with polyclonal ABS.

Immunotherapy in the poisoned patient. Overview of present applications and future trends

Immunotherapy for reversal of toxicity due to poisons and drugs is not new. However, refinements in antibody isolation and purification as well as the advancement of hybridoma technology and recombinant DNA biotechnology has led to a new generation of immunotherapeutic and diagnostic agents. The advent of monoclonal antibody technology in 1975 heralded the new age of immunopharmacology and immunotoxicology. Monoclonal antibodies designed for a specific antigen resolved the problem of polyclonality and cross-reactivity of traditional antibodies. Along with the production and isolation of active antibody fragments from both polyclonal and human monoclonal sources, as well as the ability to tailor-make chimeric antibodies by recombinant biotechnology, the development of novel immunotherapeutic agents has taken place. Two immunotherapeutic modalities, digoxin-specific antibody fragments (Fab) and snake antivenin, have been available for the clinician's armamentarium for years. Along the same lines of anti-digoxin Fab development, application of newer antibody isolation technology has led to a purified IgG(T) antibody for snake venom poisoning which is still in the developmental stages. Potential future developments in immunotherapeutics must overcome the clinical problems of immunogenicity and adverse reactions to the antibodies. Human monoclonal sources, active antibody fragments, and chimeric antibodies from transfectomas are all potential resolutions to these problems.

Anaphylaxis: pathophysiology, clinical presentations and treatment

Anaphylaxis and anaphylactoid reactions are abrupt, often life-threatening episodes, secondary to the liberation of certain chemical mediators, and their effects on target organs. The number of agents known to trigger such reactions is expanding, with the most common fatal reactions secondary to penicillins, iodinated contrast material (ICM), and hymenoptera stings. Limited studies point to upper airway obstruction and circulatory collapse as the causes of death in man. It is felt that the frequency of cardiovascular involvement is not widely appreciated, and that hypotensive patients can be markedly hypovolemic. The primary goals of treatment should be aimed at preventing or reversing complications, and include immediate attention to the airway, cardiac monitoring, and establishment of intravenous access. The cornerstone of pharmacologic therapy is epinephrine. A comprehensive review of the pathophysiology, symptomatology, and treatment is presented.

Detection and quantification of the organophosphate insecticide paraoxon by competitive inhibition enzyme immunoassay

A competitive inhibition enzyme immunoassay (EIA) was developed to detect and quantify levels of the organophosphate insecticide paraoxon in body fluids. Protein-conjugated paraoxon served as an immunogen for the production of rabbit heteroantiserum, from which affinity purified IgG anti-paraoxon antibodies were isolated using a heterologous protein-paraoxon-conjugated immunoabsorbent. In the competitive inhibition EIA a standard curve was generated for the inhibition of binding of anti-paraoxon IgG to a solid-phase bound heterologous protein-paraoxon conjugate by various concentrations of free paraoxon. Binding was proportionate to the color change of an appropriate substrate generated by an enzyme-conjugated second antibody specific for the rabbit IgG anti-paraoxon. The assay detected paraoxon levels as low as 10(-10)M (28 pg/ml) in buffer, and serum paraoxon levels as low as 10(-9)M. In addition to its sensitivity, this technique is ideally suited to the simultaneous processing of large numbers of samples in less than 2 hr. The competitive inhibition EIA is cost effective and should facilitate environmental surveillance using sentinel animals, expand laboratory toxicology studies, and improve clinical detection capabilities.