An intratumoral immunotherapy for treating cancer in a subject in need includes a therapeutically effective amounts of cowpea mosaic virus (CPMV), CPMV virus-like particles, potato virus X (PVX), and/or PVX virus-like particles formulated for in situ administration to cancer of the subject, wherein the therapeutically effective amount of CPMV, CPMV virus-like particles, PVX, and/or PVX virus-like particles is an amount effective to provide a durable and systemic anticancer response against cancer metastasis and recurrence in the subject, and the CPMV, CPMV virus-like particles, PVX, and/or PVX virus-like particles are not used as a vehicle for drug or antigen delivery.

A vaccine composition including a plant virus particle linked to an HER2 antigen is described. The vaccine composition can be used for methods of treating or preventing an HER2-expressing cancer in a subject by administering to a subject in need thereof an effective amount of the vaccine composition.