Efficient Production of Soluble Full-Length Norovirus VP1 in <i>Escherichia coli</i> ArcticExpress (DE3) with Potential for Diagnostic Assay Development

Human noroviruses (HuNoVs) are one of the main causative agents of non-bacterial gastroenteritis. The viral capsid protein VP1 is the main target for diagnostics. Although eukaryotic expression systems can produce correctly assembled VP1, they are associated with high costs and complexity. The Escherichia coli prokaryotic expression system is attractive for large-scale expression; however, VP1 often aggregates into insoluble inclusion bodies in conventional strains (BL21 (DE3)). The ArcticExpress (DE3) strain co-expresses psychrophilic chaperonins to improve protein folding at low temperatures enhancing the soluble yield of difficult-to-express targets. In this study, we demonstrated that E. coli ArcticExpress (DE3) under low-temperature induction enabled the high-yield production of soluble full-length VP1 for HuNoVs GII.4 and GII.17. In BL21 (DE3), the mentioned antigens were aggregated into insoluble inclusion bodies. Using ArcticExpress(DE3), VP1 yield was identified as approximately 18-93 mg/L across the tested genotypes. In BL21 (DE3), the protein outcome was genotype-dependent: GII.4 could be recovered only via insoluble-fraction processing, GII.17 remained undetectable or present only at trace levels under the conditions tested. The ArcticExpress-derived viral antigen retained antigenic properties and was recognized by cross-reactive anti-GII antibodies. To our knowledge, this study provides evidence that ArcticExpress (DE3) enable the soluble production of full-length HuNoVs VP1 suitable for downstream immunochemical analysis.