The invention provides a norovirus genogroup I VP1 capsid protein having an amino acid sequence wherein the amino acid sequence stretch in the P domain Ala-Ala-Leu-Leu/Val-His-Tyr is modified to Ala-Ala-Leu-LeuNal-Arg/Lys-Tyr.

An isolated expression enhancer active in a plant, portion of a plant or plant cell, the expression enhancer is provided. The isolated expression enhancer may be selected from the group consisting of nbEPI42 (SEQ ID NO:1); nbSNS46 (SEQ ID NO:2); nbCSY65 (SEQ ID NO:3); nbHEL40 (SEQ ID NO:4); and nbSEP44 (SEQ ID NO:5). Methods for using the isolated expression enhancer are also provided.

Nucleic acids encoding modified norovirus VP1 proteins, and VLPs comprising one or more of the modified norovirus VP1 proteins are provided. Methods for modified norovirus VP1 protein, and norovirus VLP, production in plants, portions of the plant or a plant cell, are also described.

Nucleic acids encoding modified norovirus VP1 proteins, and virus-like particles (VLPs) containing one or more of the modified norovirus VP1 proteins, and compositions containing the nucleic acids, VP1 proteins, or the VLPs are provided. Methods for producing modified norovirus VP1 protein, and norovirus VLP, production in plants, portions of the plant or a plant cell, are also provided.

Methods of purifying virus-like particles (VLPs) that are substantially free of process contaminants and infectious agents. The methods incorporate, for example, low-pH treatment during harvest and/or inactivation by a solvent and/or detergent during VLP capture.

Disclosed herein are vaccine compositions, in particular, polyvalent icosahedral compositions for antigen presentation. The disclosed compositions may contain an S particle made up of recombinant fusion proteins. The recombinant fusion proteins may include a norovirus (NoV) S domain protein, a linker protein domain operatively connected to the norovirus S domain protein, and an antigen protein domain operatively connected to said linker.

Methods of purifying virus-like particles (VLPs) that are substantially free of process contaminants and infectious agents. The methods incorporate, for example, low-pH treatment during harvest and/or inactivation by a solvent and/or detergent during VLP capture.

An isolated expression enhancer active in a plant, portion of a plant or plant cell, the expression enhancer is provided. The isolated expression enhancer may be selected from the group consisting of nbMT78 (SEQ ID NO:1); nbATL75 (SEQ ID NO:2); nbDJ46 (SEQ ID NO:3); nbCHP79 (SEQ ID NO:4); nbEN42 (SEQ ID NO:5); atHSP69 (SEQ ID NO:6); atGRP62 (SEQ ID NO:7); atPK65 (SEQ ID NO:8); atRP46 (SEQ ID NO:9); nb30S72 (SEQ ID NO:10); nbGT61 (SEQ ID NO:11); nbPV55 (SEQ ID NO:12); nbPPI43 (SEQ ID NO:13); nbPM64 (SEQ ID NO:14); and nbH2A86 (SEQ ID NO:15). Methods for using the isolated expression enhancer are also provided.

Nucleic acids encoding modified norovirus VP1 proteins, and VLPs comprising one or more of the modified norovirus VP1 proteins are provided. Methods for modified norovirus VP1 protein, and norovirus VLP, production in plants, portions of the plant or a plant cell, are also described.

Nucleic acids encoding modified norovirus VP1 proteins, and VLPs comprising one or more of the modified norovirus VP1 proteins are provided. Methods for modified norovirus VP1 protein, and norovirus VLP, production in plants, portions of the plant or a plant cell, are also described.