title: The effects of the multiplicity of infection on viral subpopulations during passage of Newcastle disease viruses.
abstract: When mixtures of two clones of the Italy-Milano strain of Newcastle disease virus were inoculated so that one clone was present in quantities 20 times greater than the other, maintenance of that population ratio through six serial passages in 10-day-old embryonating chicken eggs depended on the multiplicity of infection of the first passage. The initial ratio was preserved when the eggs were inoculated at low multiplicity, 10(1) virions inoculated, but not at high multiplicity, 10(6) virions inoculated. In the latter situation, the clear plaque clone, which comprised 1/20 of the initial population of the inoculum, increased in numbers to parity with the red plaque clone after only six serial passages in embryonating eggs. Explanations for the competitive advantage of the clear plaque clone at high multiplicity of infection are discussed.
mesh_terms: D000818:Animals; D002642:Chick Embryo; D002999:Clone Cells / Q000502:physiology; D009522:Newcastle disease virus / Q000502:physiology*; D014779:Virus Replication