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.

An anti-cancer virus composition including an icosahedral-shaped plant virus or virus-like particle linked to a HER2 antigen is described. The anti-cancer virus composition can be used for methods of treating or decreasing the risk of developing a HER2-expressing cancer in a subject by administering to a subject in need thereof an effective amount of the anti-cancer virus composition.

An anti-cancer virus composition including an icosahedral-shaped plant virus or virus-like particle linked to a HER2 antigen is described. The anti-cancer virus composition can be used for methods of treating or decreasing the risk of developing a HER2-expressing cancer in a subject by administering to a subject in need thereof an effective amount of the anti-cancer virus composition.

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.