title: Particle heterogeneity in vaccinia virus populations during passage.
mesh_terms: D002460:Cell Line; D002499:Centrifugation, Density Gradient; D003673:Defective Viruses / Q000254:growth & development*; D014616:Vaccinia virus / Q000254:growth & development*; D014762:Viral Interference; D010948:Viral Plaque Assay; D014771:Virion / Q000254:growth & development*