The Persistent Production of Small Quantities of Infectious Newcastle Disease Virus in Grossly Unaltered L and U12 Strain Cells

Abstract

Inapparent infections of L and U₁₂ cell strains by Newcastle disease virus are described in which low concentrations of virus were persistently elaborated by the cells. Detectable amounts of infectious virus were found more frequently in L strain cultures and appeared to be associated with the cell fractions in slightly greater quantities. Even though they contained virus, the carrier cell lines were as susceptible as previously uninoculated stock cell cultures to the toxic effect of large virus inocula.