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Updated: Oct 28, 2026
Scalable High Throughput Selection From Phage-displayed Synthetic Antibody Libraries
Published on: January 17, 2015
Multiple Phagemids Within Single Bacterial Colonies During Construction and Bio-Panning of Single-Domain (VH and VHH)
Kyeongeun Kim1,2,3, Wookyoung Chun1,2,4, Hyunji Yang1,2,4
1Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 03080, Republic of Korea.
Background/Objectives:
Phage display relies on the physical linkage between the antibody fragment displayed on a virion (phenotype) and the phagemid encoding it (genotype), allowing antigen-binding clones enriched by bio-panning to be identified by sequencing of individual colonies. In colony-based screening, an additional practical assumption is that each isolated bacterial colony represents a single phagemid sequence. Single-domain antibodies (sdAbs), including the variable domain of the heavy chain of a heavy-chain-only antibody (VHH), are increasingly used as displayed molecules, yet their library construction and bio-panning protocols have been adopted, largely unmodified, from those established for single-chain variable fragment (scFv) and fragment antigen-binding (Fab). We therefore asked whether the underlying assumption of one phagemid per colony holds for sdAb phage display.
Methods:
Using two alpaca immune libraries-a VHH library and a VH/VHH library (VH, the variable domain of the heavy chain)-we tracked Sanger sequencing chromatograms through library construction and three rounds of bio-panning, and compared classical single-colony screening with a strategy in which pooled phagemid DNA recovered after bio-panning was retransformed into naïve Escherichia coli (E. coli) before screening.
Results:
Mixed-peak chromatograms were infrequent in the initial libraries (10-20%) but accounted for 80% and 50% of chromatograms in the final bio-panning round of the VHH and VH/VHH libraries. Classical screening-periplasmic enzyme-linked immunosorbent assay (ELISA) followed by Sanger sequencing-failed: only 5.7% and 6.9% of antigen-binding colonies yielded interpretable single-peak sequences. Retransformation restored clonality, raising the proportion of single-peak chromatograms to ~88% overall, and retransformation of individual mixed colonies showed that single colonies harbored multiple distinct phagemids.
Conclusions:
Colony-level clonality is not strictly preserved in single-domain VH and VHH phage display-more plausibly through multiple phage infection during amplification-and a simple retransformation step restores reliable identification of antigen-binding clones.
