Cloning, expression, and purification of an anti-desipramine single chain antibody in NS/O myeloma cells

Expression and characterization of the ScFv fragment of antiplatelet GPIIIa monoclonal antibody SZ-21

Platelet thrombus formation is a major contributor to various cardiovascular diseases caused by vascular occlusion. Glycoprotein IIb/IIIa (GPIIb/IIIa) plays a key role in platelet aggregation and hence the formation of thrombi. In the present study, the genes encoding the light- and heavy-chain variable regions (V(H) and V(L)) of SZ-21, which is a monoclonal antibody (MoAb) against GPIIIa integrin have been cloned by RT-PCR from the SZ-21 hybridoma. The genes of V(H) and V(L) were attached to the oligonucleotide of the linker peptide and single-chain antibody fragment (ScFv) was constructed. The ScFv was ligated into phage display vector pHEN1, and the phagemid pHEN1-21ScFv was constructed. The high-affinity phage display technology was used to retain the SZ-21ScFv binding activity to platelets in great effort. After four rounds of enrichment, the screening clone of SZ-21ScFv gene with good reactivity to platelets was ligated into highly expressed vector pET20b and expressed in Escherichia coli BL21(DE3)PlysS for the fusion protein. Recombinant ScFv fragment was produced mostly in the form of inclusion bodies, with its yield up to 21% of the total amount of bacteria protein. The ScFv fragment with the similar binding activity to platelets as MoAb SZ-21 was confirmed by enzyme-linked immunosorbent assay (ELISA) and Western blot. ADP-induced platelet aggregation can be inhibited by ScFv fragment in a dose-dependent manner and the maximal inhibition rate was obtained at a concentration of 750 nM. In addition, the ScFv fragment has ability to inhibit the binding of fibrinogen to platelets and react with endothelial cells. In this study, we have successfully produced the SZ-21ScFv, which retained the binding affinity to platelets and antithrombotic ability of their murine counterparts.

Three-step purification of bacterially expressed human single-chain Fv antibodies for clinical applications

We have obtained a cell line which secretes a human monoclonal IgM (B7) reacting with the myosin heavy chain of human heart. We have constructed single-chain fragments (scFv) of B7. The scFv may be useful for the imaging of myocardial necrosis after myocarditis, cardiac drug toxicosis or graft rejection. The aim of our work was to purify the scFv for immunoscintigraphy. We describe several purification steps including immobilized metal affinity chromatography (IMAC), anti-c-myc monoclonal antibody affinity chromatography, size-exclusion chromatography with Superdex 75 HR 10/30 and ion-exchange chromatography (mini Q TM 30Q).

Immunoassay for wheat processing quality: utilization of a sandwich assay incorporating an immobilized single-chain fragment

A single-chain fragment (scFv) was engineered from a monoclonal antibody to high molecular weight glutenin subunits (HMW-GS), wheat flour polypeptides that play a major role in determining the mixing- and extension strength-related properties of dough and its subsequent baking performance. The scFv was expressed in a thioredoxin mutant Escherichia coli strain that allows disulfide bond formation in the cytoplasm and incorporated into a diagnostic test for wheat quality. Although the scFv lacks the more highly conserved antibody constant regions usually involved with immobilization, it was able to be directly immobilized to a polystyrene microwell solid phase without chemical or covalent modification of the protein or solid phase and utilized as a capture antibody in a double-antibody (two-site) immunoassay. In the sandwich assay, increasing HMW-GS concentrations produced increasing assay color, and highly significant correlations were obtained between optical densities obtained in the ELISA using the scFv and the content of large glutenin polymers in flours as well as measures of dough strength as measured by resistance to dough extension in rheological testing. The assay using the scFv was able to be carried out at lower flour sample extract dilutions than that required for a similar assay utilizing a monoclonal capture antibody. This research shows that engineered antibody fragments can be utilized to provide superior assay performance in two-site ELISAs over monoclonal antibodies and is the first application of an engineered antibody to the analysis of food processing quality.

Anti-digoxin scFv fragments expressed in bacteria and in insect cells have different antigen binding properties

A gene encoding a single-chain antibody fragment directed against digoxin (named 1C10 scFv) was cloned in two expression systems. For this purpose, a new baculovirus transfer cassette fully compatible with the procaryotic pHEN vector was constructed. Baculovirus production led to higher yield than did Escherichia coli expression. The procaryotic fragment showed variations in the fine specificity profile but an affinity constant nearly identical to that of the 1C10 Fab, whereas the eucaryotic scFv fragment had a lower affinity with a specificity profile identical to original mAb. The half-lives of the digoxin:scFv complexes and the global specificity are compatible with therapeutic use of this antibody fragment.

High-level secretion of two antibody single chain Fv fragments by Pichia pastoris

The diagnostic and therapeutic applications of antibody single-chain Fv (sFv) fragments often require large amounts of protein that can be problematic and expensive to obtain. Here we report the secretion of two sFv fragments by the yeast Pichia pastoris at levels up to 250 mg/l. Soluble sFv fragments were purified from culture supernatants in one step by affinity or metal-chelating chromatography, and were indistinguishable from their bacterially expressed counterparts in terms of affinity. Secretion of functional sFv fragments by Pichia pastoris provides a low cost, high yield alternative to current sFv expression systems.

Bacterial expression and characterization of an anti-desipramine single-chain antibody fragment

Tricyclic antidepressant toxicity is a leading cause of death from intentional drug overdose. Monoclonal antibody Fab' fragments specific for the tricyclic antidepressant, desipramine, reverse acute drug toxicity but may themselves have adverse effects at therapeutic doses. To evaluate the characteristics of smaller antibody fragments, we cloned, expressed and characterized a 26 kD single chain Fv fragment (G5-sFv). A DNA sequence encoding VH-linker-V1 was constructed from hybridoma mRNA encoding a high affinity monoclonal desipramine specific IgG1 and expressed in E. coli. G5-sFv was produced at high levels as insoluble inclusion bodies. Single chain Fv was solubilized, folded in a redox buffer and affinity purified on desipramine-Sepharose. The affinity of G5-sFv for desipramine was similar to that of the corresponding monoclonal Fab' as measured by surface plasmon resonance (Fab' 5.5 +/- 0.5 x 10(8) M-1, sFv 2.3 +/- 0.5 x 10(8) M-1). G5-sFv administered to rats after a tracer dose of 3H-desipramine produced rapid and marked redistribution of drug from tissues into serum. G5-sFv was stable at 4 C for greater than 6 months but lost activity at higher temperatures. We conclude that desipramine-specific-single chain Fv expressed in E. coli retains the affinity of the parent antibody for desipramine. The pharmacokinetic effect of G5-sFv on desipramine distribution suggests that it may be useful as an antidote for desipramine overdose.

Inverse targeting of peritoneal tumors: selective alteration of the disposition of methotrexate through the use of anti-methotrexate antibodies and antibody fragments

We have hypothesized that antidrug antibodies (ADAb) may be employed to impart site-specific alterations in the disposition of drug molecules, potentially allowing for targeted drug therapy. We are specifically interested in minimizing systemic exposure to free drug and systemic toxicities resultant from regional chemotherapy through the intravenous administration of ADAb. In this report, we present the production and purification of anti-methotrexate Fab fragments, and we present investigations of the effects of anti-methotrexate Fab and anti-methotrexate immunoglobulin G on the disposition of methotrexate in the rat. Pharmacokinetic studies revealed that intravenous anti-methotrexate immunoglobulin G (anti-MTX IgG) and anti-methotrexate Fab (anti-MTX Fab) administration produced dramatic alterations in the plasma pharmacokinetics of methotrexate (MTX), following intraperitoneal MTX administration (area under the total MTX concentration vs time curve for anti-MTX IgG relative to control, 420 +/- 90 (p < 0.05); for anti-MTX Fab relative to control, 46 +/- 6.1 (p < 0.05); area under the free MTX concentration vs time curve for anti-MTX IgG relative to control, 0.64 +/- 0.16; for anti-MTX Fab relative to control, 0.45 +/- 0.20 (p < 0.05)). Additional studies conducted in anesthetized rats revealed no significant alterations in the area under the total peritoneal MTX concentration vs time curves, free MTX peritoneal concentration vs time curves, or peritoneal exit rate of MTX in anti-MTX Fab treated animals relative to controls. Therefore, our pharmacokinetic studies demonstrate that ADAb may produce site-specific alterations in drug pharmacokinetics, potentially enhancing the site specificity of drug distribution and drug action following regional chemotherapy.

Effects of recombinant drug-specific single chain antibody Fv fragment on [3H]-desipramine distribution in rats

Tricyclic antidepressant overdose can be reversed in rats by drug-specific antibody Fab fragments, but the required Fab dose may itself by toxic. We studied the potential use of a smaller, recombinant desipramine (DMI)-specific single chain Fv fragment (B9-sFv) for this purpose. Anesthetized rats received a tracer (subtoxic) dose of [3H]-DMI followed in 15 min by B9-IgG, B9-Fab, B9-sFv (0.1 mumol of binding sites) or BSA. Each of the active treatments produced a rapid and substantial increase in the serum radiolabel concentration, whereas BSA did not (P < 0.001). The increase in serum radiolabel concentration 1 min after treatment was 13.3-fold with B9-IgG, 10.0-fold with B9-Fab and 7.3-fold with B9-sFv. Serum antibody concentrations were also highest after B9-IgG and lower with B9-Fab or B9-sFv. The 24-hr urinary excretion of radiolabel did not differ among groups, but was extensive even in the BSA group and probably represented the excretion of DMI metabolites. B9-sFv concentrations in urine or buffer at 37 degrees declined by >90% over 24 hr, but this fragment was much more stable in serum, retaining 70% of its activity after 96 hr. These data demonstrate that B9-sFv can alter markedly the distribution of [3H]-DMI in vivo. The rapidity of this effect, and its magnitude in comparison with Fab fragment or IgG, suggest that further study of B9-sFv as a treatment of DMI overdose is warranted.