Infectious Bronchitis Virus Interference with Growth of Newcastle Disease Virus. I. Study of Interference in Chicken Embryos

Abstract

The egg-adapted (DA) strain of infectious bronchitis virus (IBV) and the GB (Texas) strain of Newcastle disease virus (NDV) were inoculated into embryonating chicken eggs in varied amounts and at different time intervals. The results of the different combinations clearly showed that an excess of IBV over NDV consistently interfered with the growth of NDV in chicken embryonating eggs, even when NDV was inoculated 4 hours prior to IBV. Hemagglutinating activity in embryonating chicken eggs inoculated solely with the GB strain of NDV was detected as early as 17 hours after inoculation. The allantoic fluid harvested from eggs that died but that did not develop hemagglutinating titers after inoculation of the IBV-NDV mixtures contained IBV. Heat-inactivated IBV did not interfere with NDV. Interferon did not appear to play a detectable role in the interference of IBV over NDV. Active IBV, when mixed in vitro with NDV, did not interfere with the expected hemagglutinating titer.