Expression of functional antibody fragments

Abstract

Methods for the high yield production of antibody Fv-containing polypeptides, especially Fab′ and F(ab′)2 antibody fragments are provided. Expression of heavy and light chain Fv in a microbial secretory system is followed by recovery of Fv from the periplasm under conditions that maintain a cysteine residue as a free thiol. The free thiol is reacted with free thiol of an antibody fragment of the same or differing specificity, or with agents such as diagnostic labels or therapeutic moieties. The products offer advantages of homogeneity and purity not available through the use of known methods for preparing such derivatives.

Description

FIELD OF THE INVENTION [0001] This invention relates to the production of functional antibody fragments in a microbial host. BACKGROUND OF THE INVENTION [0002] Naturally occurring antibodies (immunoglobulins) comprise two heavy chains linked together by disulfide bonds and two light chains, each light chain being linked to one of the heavy chains by disulfide bonds. Each chain has an N-terminal variable domain (VH or VL) and a constant domain at its C-terminus; the constant domain of the light chain is aligned with and disulfide bonded to the first constant domain of the heavy chain, and the light chain variable domain is aligned with the variable domain of the heavy chain. The heavy chain constant region includes (in the N- to C-terminal direction) the CH1 and hinge regions. The light chain also contains a hinge domain. Particular amino acid residues are believed to form an interface between and disulfide bond the light and heavy chain variable domains, see e.g. Chothia et al., J. ...

AI Technical Summary

Benefits of technology

[0021] The principal embodiments of this invention are based on the surprising identification of cysteinyl free thiol in cysteinyl residues located outside of the light-heavy chain interface of recombinant microbial periplasmic antibody fragments, and the surprising discovery that Fv variants can be produced which contain only a single cysteinyl residue in the free thiol form. This facilitates the preparation of homogeneous recombinant F(ab′)2 and other Fv-containing bivalent polypeptides. Accordingly, in one embodiment this invention comprises expressing and secreting into the periplasm of a recombinant microbial cell culture a Fv polypeptide containing an immunoglobulin heavy chain Fv region and an immunoglobulin light chain Fv region, said light or heavy chain also comprising an unpaired cysteinyl residue as a free thiol, and recovering said polypeptide under conditions that substantially maintain said cysteinyl residue as the free thiol.

[0028] Optionally, the Fab′-SH is released from the host by freeze-thawing the host cell, subjecting it to osmotic shock, preparing a cell paste and purifying the Fab′-SH from the cell paste. Optionally, release of Fab′-SH from the host cell is facilitated by enzymatic digestion of the cell e.g., using lysozyme or physical disruption, e.g., by sonication or by use of a French press.

Problems solved by technology

1 chapter 14 (1983), however with these methods it is difficult to control the precise nature and proportions of the antibody fragment recovered.

Brennan et al. also teach the use of use sodium arsenite to cross-link two proximate cysteines, however this reaction involves highly toxic compounds.

Images