Expression of TIMP-1 in Pichia pastoris. Selection of an anti-TIMP-1 specific single-chain Fv antibody from a large non-immune library

Production, purification, and characterization of human scFv antibodies expressed in Saccharomyces cerevisiae, Pichia pastoris, and Escherichia coli

Single chain (scFv) antibodies are used as affinity reagents for diagnostics, therapeutics, and proteomic analyses. The antibody discovery platform we use to identify novel antigen binders involves discovery, characterization, and production. The discovery and characterization components have previously been characterized but in order to fully utilize the capabilities of affinity reagents from our yeast surface display library, efforts were focused on developing a production component to obtain purified, soluble, and active scFvs. Instead of optimizing conditions to achieve maximum yield, efforts were focused on using a system that could quickly and easily produce and process hundreds of scFv antibodies. Heterologous protein expression in Saccharomyces cerevisiae, Pichia pastoris, and Escherichia coli were evaluated for their ability to rapidly, efficaciously, and consistently produce scFv antibodies for use in downstream proteomic applications. Following purification, the binding activity of several scFv antibodies were quantified using a novel Biacore assay. All three systems produced soluble scFv antibodies which ranged in activity from 0 to 99%. scFv antibody yields from Saccharomyces, Pichia, and E. coli were 1.5-4.2, 0.4-7.3, and 0.63-16.4 mgL(-1) culture, respectively. For our purposes, expression in E. coli proved to be the quickest and most consistent way to obtain and characterize purified scFv for downstream applications. The E. coli expression system was subsequently used to study three scFv variants engineered to determine structure-function relationships.

An ELISA for the detection of TIMP-1 based on recombinant single chain Fv fusion proteins

BACKGROUND

Altered serum levels of TIMP-1 are an indicator of various pathological states. To quantitate TIMP-1 in biological samples, we have previously isolated TIMP-1 specific single-chain Fv fragments (scFvs) using phage-display. In the work presented here, we have used these scFvs to establish a TIMP-1 ELISA based exclusively on recombinant scFv fusion proteins.

METHODS

Two distinct TIMP-1 specific scFvs were used as the antigen binding components after being genetically fused to the N-termini of two different fusion protein constructs. One fusion protein, comprising a CL domain, serves as a coating reagent, while the second fusion protein with a modified form of bacterial alkaline phosphatase is used as a detection reagent. A double antibody sandwich-ELISA was then established and optimized.

RESULTS

An ELISA for the quantitation of tissue inhibitor of metalloproteinase (TIMP)-1, based entirely on recombinant antibody fragments, was developed as an alternative to assays using polyclonal antisera or monoclonal antibodies. Its performance was shown to compare well with a conventional ELISA. Finally, TIMP-1 concentrations in the sera of sixty healthy individuals were determined.

CONCLUSION

The assay described here provides a standardized, reliable and readily available means of quantitation of TIMP-1 in a large number of blood samples.