Single-chain variable fragment

Rotating scFv fragment with highlighted complementarity determining regions (CDRs)
The two possible structures of a single-chain variable fragment, with the antigen binding sites including the N-termini on the left and the C-termini on the right. The linker peptides are shown as arrows.

A single-chain variable fragment (scFv) is not actually a fragment of an antibody, but instead is a fusion protein of the variable regions of the heavy (VH) and light chains (VL) of immunoglobulins, connected with a short linker peptide of ten to about 25 amino acids.[1] The linker is usually rich in glycine for flexibility, as well as serine or threonine for solubility, and can either connect the N-terminus of the VH with the C-terminus of the VL, or vice versa.[2] This protein retains the specificity of the original immunoglobulin, despite removal of the constant regions and the introduction of the linker.[3] The image to the right shows how this modification usually leaves the specificity unaltered.

These molecules were created to facilitate phage display, where it is highly convenient to express the antigen-binding domain as a single peptide. As an alternative, scFv can be created directly from subcloned heavy and light chains derived from a hybridoma. ScFvs have many uses, e.g., flow cytometry, immunohistochemistry, and as antigen-binding domains of artificial T cell receptors (chimeric antigen receptor).

Unlike monoclonal antibodies, which are often produced in mammalian cell cultures, scFvs are more often produced in bacteria cell cultures such as E. coli.[3]

  1. ^ Huston, J. S.; Levinson, D.; Mudgett-Hunter, M.; Tai, M. S.; Novotný, J.; Margolies, M. N.; Crea, R. (1988). "Protein engineering of antibody binding sites: recovery of specific activity in an anti-digoxin single-chain Fv analogue produced in Escherichia coli". Proceedings of the National Academy of Sciences of the United States of America. 85 (16): 5879–5883. Bibcode:1988PNAS...85.5879H. doi:10.1073/pnas.85.16.5879. PMC 281868. PMID 3045807.
  2. ^ Schirrmann, Thomas (8 November 2004). "Tumorspezifisches Targeting der humanen Natürlichen Killerzellinie YT durch Gentransfer chimärer Immunglobulin-T-Zellrezeptoren" (in German). Berlin. doi:10.18452/15246. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ a b Peterson, Eric; Owens, SM; Henry, RL (2006). "Monoclonal Antibody Form and Function: Manufacturing the Right Antibodies for Treating Drug Abuse". AAPS Journal. 8 (2): E383–E390. doi:10.1208/aapsj080243. PMC 3231570. PMID 16796389.