Stability in Newcastle disease virus-infected cells of HN protein which lost its functional activity under conditions of protein synthesis inhibition by cycloheximide.

Chick embryo cell cultures were infected with Newcastle disease virus (strains Italia, Beaudette and B1), labelled with 14C-amino acids from 5 to 6 hr post infection (p.i.), incubated in chase conditions from 6 to 10 hr p.i. in the presence or absence of cycloheximide (100 microgram/ml) and analyzed by slab polyacrylamide gel electrophoresis and autoradiography. In chase experiments the HN protein was stable in all three strains. The haemagglutinating activity of cell homogenates was greatly reduced after the addition of cycloheximide in tests with Beaudette and B1 strains; treatment of the homogenates with neuraminidase from Vibrio cholerae did not influence this effect.