Characterization of a cross-reactive linear epitope in human genogroup I and bovine genogroup III norovirus capsid proteins

The Southampton norovirus (SV) capsid protein was expressed as VLPs by recombinant baculoviruses in insect cells and was used to immunize mice for the production of monoclonal antibodies (mAbs). One mAb, CM54, showed broad cross-reactivity to genogroup I (GI) noroviruses, but was not reactive to GII capsid proteins. Interestingly mAb CM54 reacted to a bovine norovirus capsid protein. Immunoblot analysis indicated the binding site for CM54 was located in the shell domain between amino acid residues 102-225 of the SV capsid protein. The epitope was mapped to high resolution using a peptide array and was located to the sequence LEDVRN at amino acid residues 162-167. Alignment of norovirus capsid protein sequences confirmed the epitope sequence was common to particular groups of human and bovine noroviruses. Modeling of the epitope onto the recombinant NV capsid protein revealed it was located to the inner surface of the shell domain.