Cloning, expression and functional activities of a single chain antibody fragment directed to fusion protein of respiratory syncytial virus

Background: HNK20 is a murine IgA which is currently being investigated in clinical trials against respiratory syncytial virus (RSV) infections in infants and young children. Objective: To produce a single chain antibody fragment (scFv) from HNK20 hybridoma cells and assess its functional activities in vitro and in vivo (mouse model). Study design: The V regions of heavy and light chains were cloned and linked by a sequence encoding for (Gly(4)Ser)(3) and expressed in Escherichia coli. Results: Over 100 mg/l of the HNK20-scFv was produced in shake flasks after induction with isopropyl (beta-D-thiogalactopyranoside (IPTG). ScFv was purified under native conditions on a Ni2+ affinity column and migrated as a single band of 34 kDa on sodium dodecyl sulfate (SDS)-gels. ScFv demonstrated similar affinity as its parent IgA molecule, neutralized RSV in vitro and significantly reduced RSV titers in lungs of mice when administered intranasally shortly before or a day after RSV challenge. Conclusion: It is possible that this scFv or its derivatives, when applied by intranasal or pulmonary route, will be useful for treatment of RSV infections in infants and young children.