Noninfectious forms of Newcastle disease and influenza viruses: Studies on noninfectious virus occurring within cells that are producing fully infectious virus

Abstract

The multiplication of Newcastle disease virus (NDV) in the allantoic membrane of the chick embryo has been analyzed. About 40 to 80% of the virus inoculated was adsorbed, and of this less than 0.1 to 1% could be demonstrated in the allantoic membrane up to 2 hours after infection. After 2 to 3 hours, virus increased steeply in the allantoic membrane and was rapidly released into the allantoic fluid. Evidence is presented which suggests a continuous virus production for many hours after initial infection. The nonsedimentable, noninfectious hemagglutinin of NDV (S) could be demonstrated early in the infectious cycle but not prior to development of infectious virus. Its presence was confined to the allantoic membrane. Serial passage of undiluted NDV allantoic fluid and inoculation of chick embryos with large amounts of noninfectious NDV (S) did not result in a von Magnus phenomenon. It is suggested that the S hemagglutinin of NDV represents a developmental stage in virus reproduction. A nonsedimentable, noninfectious hemagglutinin has also been demonstrated in the allantoic membranes of chick embryos inoculated with small amounts of PR8 virus. It differs in both biological and physical properties from the noninfectious virus produced by serial passage of undiluted PR8 allantoic fluid and appears to be closely analogous to the NDV S component.