Satellite tobacco necrosis virus, computer artwork. A satellite virus is a subviral agent consisting of nucleic acids encoding its protein coat. Satellite viruses cannot infect host cells alone; they require a helper virus, in this case tobacco necrosis virus (TNV), to enable them to enter and replicate within the cell. TNV causes lesions on the leaves of tobacco plants (Nicotiana tabacum) which are exacerbated by the satellite virus.