Identification of infectious bronchitis virus by interference with the B-1 isolant of Newcastle disease virus. Waxing and waning of interference.

The Massachusetts and the Connecticut types of infectious bronchitis virus (IBV) were identified by interference in embryonating chicken eggs (ECE) with the production of hemagglutinin by the B-1 isolant of Newcastle disease virus (NDV). This interference test appears to be specific because the above interference was eliminated by adding type-specific anti-IBV serum to the IBV-NDV system; however, interference was not detectable when fowlpox virus (FPV) and infectious laryngotracheitis virus (LTV) were substituted for IBV. Specificity of the interference test was dependent upon a system involving IBV, NDV, FPV, and LTV. The test can be done in 3 days and requires minimum laboratory facilities. Most of the experiments were done with the Massachusetts type of IBV. Only a few were with the Connecticut type. The interfering action of the above two types of IBV over the B-1 isolant of NDV waxed between the 24th and 54th hr after inoculation of NDV; it was waning at the 54th-60th hr postinoculation and was undetectable by the 66th-72nd hr.