Anti-metatype antibodies stabilize the fluorescein single-chain antibody 4-4-20 complex against dissociation by hydrostatic pressure

Rapid refolding and polishing of single-chain antibodies from Escherichia coli inclusion bodies

An inexpensive and fast-folding strategy for single-chain antibody (scFv) recovered from Escherichia coli inclusion bodies has been developed. Two anti-fluorescein single-chain antibodies, 4-4-20 and 4M5.3, were expressed as inclusion bodies in E. coli for use in a comparative refolding study. Active protein yields as well as degree of aggregation were evaluated for scFv produced by stepwise dialysis, redox dialysis, and a newly developed controlled dilution and filtration strategy. Although all three methods produced active protein for both 4-4-20 and 4M5.3, the extent of aggregation differed greatly among the methods. For 4-4-20, the controlled dilution and filtration strategy reduced aggregation by half, allowed batch processing times of 8h (an 18-fold improvement), and significantly reduced denaturant usage while increasing active yields by 150%. A hydroxyapatite resin polishing step was used to remove completely the aggregate species and inactive monomeric scFv from active scFv.

The use of high pressure for separation and production of bioactive molecules

Due to its action on the forces governing inter- and intramolecular interactions, the application of high pressure to biopurification or bio-elaboration of a product are of interest. The two closely thermodynamically related parameters, pressure and temperature, render processes based on their action clean, as no chemical reagents have to be added (and thus further removed) when they are applied. The use of high pressure in the development of desorption methods for the purification of bioactive molecules, particularly in the immunoaffinity field, is reviewed and discussed. Also mentioned is the application of the pressure parameter during the synthesis of a bioreagent. Finally, integrated processes relative to the synthesis and purification of these compounds are proposed.

Anti-metatype antibody stabilization of Fv 4-4-20 variable domain dynamics

Anti-metatype (anti-Met) antibodies are immunoglobulins that specifically recognize and stabilize antibodies in their liganded or metatypic state, but lack specificity for either the hapten or the unliganded antibody. Autologous anti-Met antibodies were previously observed in vivo, suggesting that a metatypic autoantibody response could play a physiological role in the immune network, e.g. controlling the clearance of immune complexes from circulation. The first elicited anti-Met antibodies were against the fluorescein-liganded high affinity murine anti-fluorescein monoclonal antibody 4-4-20. The fluorescein-hapten system has proved to be an invaluable tool for both the recognition and characterization of the metatypic response by utilization of its spectral properties. In this investigation, hydrostatic pressure measurements, in conjunction with fluorescence spectroscopy, were performed on the recombinant Fv derivative (Fv 4-4-20) of the high affinity anti-fluorescein monoclonal antibody 4-4-20 complexed to anti-Met antibodies to study the influence of anti-Met antibodies of Fv 4-4-20 intervariable domain interactions. Anti-Met antibodies bound to liganded Fv 4-4-20 were observed to cause a change in the fluorescence properties of fluorescein that was not observed when anti-Met antibodies were bound to the liganded parent immunoglobulin. The variation of these spectral properties upon addition of anti-Met antibodies was shown to be correlated with dissociation of the variable domains in Fv 4-4-20 in response to its interaction with the anti-Met antibody. The ability to cause variable domain dissociation was dependent on whether monoclonal or polyclonal anti-Met antibodies were bound to the metatype. A model was proposed that elucidated the interaction of anti-Met antibodies, polyclonal and monoclonal, with variable domains of the primary anti-antigen antibody.

The use of hydrostatic pressure as a tool to study viruses and other macromolecular assemblages

Recent studies on the effect of pressure on macromolecular assemblages have provided new information on protein-protein and protein-nucleic acid interactions. New findings have recently emerged on the use of hydrostatic pressure to assess intermediate states in the assembly pathways of viruses, multimeric proteins and protein-nucleic acid complexes, addressing many questions of macromolecular recognition.

Comparative properties of the single chain antibody and Fv derivatives of mAb 4-4-20. Relationship between interdomain interactions and the high affinity for fluorescein ligand

Recombinant Fv derivative of the high affinity murine anti-fluorescein monoclonal antibody 4-4-20 was constructed and expressed in high yields, relative to the single chain antibody (SCA) derivative (2 3-fold), in Escherichia coli. Both variable heavy (VH) and variable light (VL) domains, that accumulated as insoluble inclusion bodies, were isolated, denatured, mixed, refolded, and affinity-purified to yield active Fv 4-4-20. Affinity-purified Fv 4-4-20 showed identical ligand binding properties compared with the SCA construct, both were slightly lower than the affinities expressed by Fab or IgG 4-4-20. Proper protein folding was shown to be domain-independent by in vitro mixing of individually refolded variable domains to yield functional Fv protein. In solid phase and solution phase assays, Fv 4-4-20 closely approximated the SCA derivative in terms of both idiotype and metatype, confirming identical active site structures and conformations. The equilibrium dissociation constant (Kd) for the VL/VH association (1.43 x 10(-7) M), which was determined using the change in fluorescein spectral properties upon ligand binding, was relatively low considering the high affinity displayed by the Fv protein for fluorescein (Kd, 2.9 x 10(-10) M). Thus, domain-domain stability in the Fv and SCA 4-4-20 proteins cannot be the sole cause of reduced affinity (2-3-fold) for fluorescein as compared with the Fab or IgG form of 4-4-20. With their identical ligand binding and structural properties, the decreased SCA or Fv affinity for fluorescein must be an ultimate consequence of deletion of the CH1 and CL constant domains. Collectively, these results verify the importance of constant domain interactions in antibody variable domain structure-function analyses and future antibody engineering endeavors.

Primary structures of three Armenian hamster monoclonal antibodies specific for idiotopes and metatopes of the monoclonal anti-fluorescein antibody 4-4-20

This paper reports the complete V gamma, V kappa, C gamma 1 and C kappa nucleotide and deduced amino acid sequences of two hamster monoclonal anti-metatype antibodies, 3A5-1 and 4A6. These antibodies have been previously characterized in terms of their binding and molecular stabilization properties with liganded murine monoclonal and single-chain antibody 4-4-20 active sites. Also reported are the complete V kappa and C kappa nucleotide and deduced amino acid sequence of hamster monoclonal anti-idiotype antibody 1F4, which is specific for the unliganded 4-4-20 active site. Oligonucleotide primers based on the 5' ends of murine variable genes, along with primers specific for murine IgG C gamma 1 and kappa constant region genes, have been used in cDNA and polymerase chain reactions (PCRs) to amplify IgG cDNA from Armenian hamster/mouse hybridomas. The hamster C gamma 1 and C kappa domain sequences are highly homologous to previously reported murine sequences. The anti-idiotype mAb V kappa gene demonstrated strong similarity to the murine V kappa V gene subgroup while the two anti-metatype mAb V kappa genes approximated more closely to the murine V kappa III gene subgroup. The two anti-metatype mAbs utilized highly homologous V gamma genes, with differing HCDR 3 regions, that appeared similar to the murine V gamma I(a) subgroup. These sequence determinations represent the first primary structures reported for antibodies with anti-metatype activity and are additions to the relatively sparse hamster immunoglobulin genetic database. Results are discussed in terms of 4-4-20 active site specificity and anti-metatype activity, as well as immunoglobulin structural diversity in an anti-Ig immune response.

Sandwich immunoassay for the hapten angiotensin II. A novel assay principle based on antibodies against immune complexes

Immunoassays for haptens such as short peptides or drugs are usually based on the principle of competition for a limited number of binding sites on antibody molecules. Owing to the small size of these antigens it has been thought that two specific antibodies cannot simultaneously bind a hapten. However, antisera containing so called anti-metatypic antibodies have been reported (Voss et al. (1988) Mol. Immunol. 25, 751-759) that bind to hapten-mAb complexes in a reaction where conformational changes on the primary antibody are important. Here, we report on monoclonal antibody pairs able to form ternary complexes with the octapeptide angiotensin II. The first mAb (mAb1) is conventional and binds angiotensin II with high affinity (Kd 10(-11) M). The secondary (anti-metatypic) mAbs (mAbs2s) recognize the immune complex consisting of angiotensin II bound to mAb1, but only poorly recognize mAb1 alone. An immunization technique involving tolerization with uncomplexed mAb1 was used to generate mAb2s. None of the mAbs2s were able to bind angiotensin II by themselves but all efficiently bound the complex of angiotensin II and mAb1. All mAb2s stabilized the angiotensin II-mAb1 complex and one mAb2 distinctly improved the specificity of the assay for angiotensin II. By either labelling mAb1 and immobilizing mAb2 (or vice versa) two-site immunometric assays with detection limits of 1 pg/ml angiotensin II have been established. The kinetics of the complex formation was investigated by fiber optic biospecific interaction analysis (FOBIA), a system allowing real time observation of binding events on the surface of a glass fiber. The association rate towards the liganded conformation of mAb1 was higher than towards the free mAb1. By contrast, the mAb2s dissociated at similar rates from complexed and uncomplexed mAb1.