Ribodeoxyviruses are viruses whose particles (virions) are enveloped and contain RNA and a DNA polymerase. Some of these viruses cause cancer, but most do not, nor any other disease. Ribodeoxyviruses replicate through a DNA intermediate, the DNA provirus. The DNA provirus can be assayed as infectious DNA.
Because ribodeoxyvirus information can be present in cells as a part of the cell genome, it needs no viral functions for its maintenance. Therefore, ribodeoxyviruses often persist in cells with little or no viral gene expression.
Most cancers in animals do not contain infectious ribodeoxyviruses, although they may contain ribodeoxyvirus genes and products. These same genes and products are, however, found with about the same frequency in normal cells, so that their presence in human tumors would not indicate an etiologic relationship between ribodeoxyviruses and human cancer.
It has been suggested that ribodeoxyviruses and the genes for cancer evolve independently from a normal cellular system of DNA-to-RNA-to-DNA information transfer.
(JAMA 230:1043-1045, 1974)