Groups of 75 chickens were each infected with one of 7 isolates of infectious bronchitis virus (Mass 41, Holland 52, SE 17, Ark 99, Clark 333, JMK, and Florida). Following recovery, they were challenged along with susceptible controls to the homologous and 6 heterologous isolates. Cross-immunity was determined by virus recovery 4 or 5 days post-challenge. Challenge with the homologous isolate resulted in 90-100% protection. Challenge with heterologous isolates gave variable results and an overall average resistance of 38%. The SE-17-recovered chickens had a 50% protection, whereas the Holland-52-recovered chickens ahd a 13.3% protection.
The virus of transmissible enteritis of turkeys was shown to be an enveloped pleomorphic particle with an average diameter of 110 nm (range 60-250 nm). The surface bore tubular projections about 12 nm long. The internal component was very fragile, and could not be demonstrated in situ. It appeared as a helix, with a diameter of approximately 7 nm. Hemagglutination could not be demonstrated, but the virus had a strong tendency to adhere to other material during isopycnic centrifugation in sucrose. The complete virus had a density of 1.24 g/cm3.
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