There is described a process for production of metal-coated virus particles or metallic nanoparticles, said process comprising admixing virus particles with plant material with reducing power and a metal salt, wherein the process can be provided in planta or ex planta and the virus particles aid the production of the metal-coated virus particles or metallic nanoparticles.

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.

An agent is described that includes a plant virus particle or VLP conjugate to TRAIL. Associating TRAIL with the plant virus particle or VLP serves to both target cancer cells and induce their apoptosis. The agent can therefore be used for a method of treating cancer in a subject.