Protein based NPs such as PVX and TBSV are considered ideal interms of biocompatibility, because their biodegradability shouldprevent toxicity due to accumulation in the body. Plant viruseshave evolved to infect plant hosts, and to this aim have devel-oped infection strategies totally different from those adopted byanimal viruses. Due to the lack of specific receptors for recogni-tion and entry into animal cells, they cannot infect human cells.Nonetheless, even if they behave in these systems as unreplica-tive and biologically safe nano-objects, a possible intrinsic toxicitycannot be underestimated.