Identification of human single-chain antibodies with broad reactivity for noroviruses

Norovirus infections are a common cause of gastroenteritis and new methods to rapidly diagnose norovirus infections are needed. The goal of this study was to identify antibodies that have broad reactivity of binding to various genogroups of norovirus. A human scFv phage display library was used to identify two antibodies, HJT-R3-A9 and HJT-R3-F7, which bind to both genogroups I and II norovirus virus-like particles (VLPs). Mapping experiments indicated that the HJT-R3-A9 clone binds to the S-domain while the HJT-R3-F7 clone binds the P-domain of the VP1 capsid protein. In addition, a family of scFv antibodies was identified by elution of phage libraries from the GII.4 VLP target using a carbohydrate that serves as an attachment factor for norovirus on human cells. These antibodies were also found to recognize both GI and GII VLPs in enzyme-linked immunosorbent assay (ELISA) experiments. The HJT-R3-A9, HJT-R3-F7 and scFv antibodies identified with carbohydrate elution were shown to detect antigen from a clinical sample known to contain GII.4 norovirus but not a negative control sample. Finally, phages displaying the HJT-R3-A9 scFv can be used directly to detect both GI.1 and GII.4 norovirus from stool samples, which has the potential to simplify and reduce the cost of diagnostics based on antibody-based ELISA methods.