title: Differentiation of avian infectious bronchitis virus isolates by thermal sensitivity.
abstract: Six isolates of avian infectious bronchitis virus (IBV) at different passage levels in the chicken embryo were tested for sensitivity at 56 C, with the following results: 1) isolates differed in thermal sensitivity; 2) virus was inactivated in a first-order exponential-kinetics 2-component fashion indicative of a heterogeneous population with a preponderance, 98% or more, of thermal-sensitive (S) virions over thermal-resistant (R) virons; 3) R virions 2-component populations were inactivated; 4) recovered R virions could be maintained in continuous passage in the chicken embryo as a one-component population by the limiting-dilution technique, although there was a progressive parallel increase in thermal sensitivity associated directly with the continuous passage; 5) growth curves of isolated one-component populations of R virions were quantitatively and in time sequence similar to curves of 2-component populations of continuous-passage virus.
mesh_terms: D000818:Animals; D002642:Chick Embryo; D003332:Coronaviridae / Q000145:classification*; D001351:Infectious bronchitis virus / Q000145:classification* / Q000502:physiology; D013696:Temperature