Single chain Fv fragment specific for human GM-CSF: selection and expression using a bacterial expression library.

Area of Science:

• Biotechnology
• Immunology
• Molecular Biology

Background:

• Single-chain variable fragments (scFvs) offer advantages over whole antibodies, including large-scale production and genetic modification.
• Development of specific bio-reagents is crucial for sensitive and accurate immunoassays.

Purpose of the Study:

• To engineer and characterize a novel anti-human granulocyte macrophage colony-stimulating factor (hGM-CSF) scFv.
• To evaluate its potential as a bio-reagent for immunoassay applications using a scalable bacterial expression system.

Main Methods:

• Amplification of V(H) and V(L) gene repertoires from immunized mouse splenocytes.
• Expression of scFv library in BL21 (DE3) Escherichia coli under T7 promoter.
• Light chain shuffling, cross-reactivity analysis, and surface plasmon resonance (SPR) for binding affinity measurement.

Main Results:

• Selection of a specific scFv (scFv196) with no cross-reactivity against E. coli antigens.
• scFv196 exhibited a binding affinity (K(D) = 1.5 μM) within the physiological range for hGM-CSF.
• The scFv recognized glycosylated hGM-CSF and showed evidence of periplasmic export.

Conclusions:

• A novel, specific, and high-affinity anti-hGM-CSF scFv (scFv196) was successfully developed using a bacterial expression system.
• The engineered scFv is a promising bio-reagent for immunoassay development, capable of detecting biologically relevant forms of hGM-CSF.