Sendai virus multiplication in the presence of ceruloplasmin and homologous virus envelopes.

Preincubation of Sendai virus with ceruloplasmin induced in chorioallantoic membrane (CAM) fragments the synthesis of a population with decreased infectivity and high haemagglutinating (HA) and neuraminidase (NA) activities, whereas preincubation with solubilized virus envelopes led to the production of a viral population with the same infectivity as the control, but with lower HA and NA activities. Preincubation of the virus with a mixture of ceruloplasmin and solubilized envelopes depressed the overall virus synthesis; the resulting population had a low infectivity and high HA and NA activities. The variation in the HA/NA ratio indicates a modification in the envelope structure.