Newcastle disease virus (NDV): brief history of its oncolytic strains

Background: While genetically engineered viruses are now being tested for the virus therapy of human cancers, some naturally occurring viruses display unmatched oncolytic activity. Newcastle disease virus (NDV) excels as an oncolytic agent. Objectives: As its virulence versus attenuation can be explained on molecular biological bases, it may be possible to develop or select highly oncolytic strains of NDV without adverse toxicity. Study design: Questions are posed as to the mechanisms of viral oncolysis, the appropriateness of tests to predict oncolytic activity of a given NDV strain and the best modes of administration for oncolytic effects. Answers are provided based on specific data or on considerations drawn from experience (the authors use NDV oncolysates to immunize against melanoma and kidney carcinoma) or from analogous clinical situations (therapeutic use of mumps or measles viruses). Results and conclusions: NDV oncolysates probably suit better for immunotherapy (providing also active tumor-specific immunization) than massive repeated inoculations of NDV strains, especially when the NDV strain used is not proven to be oncolytic by appropriate pre-clinical tests.