EFFECTS OF BIOLOGICAL PROPERTIES OF EMBRYO-ADAPTED BEAUDETTE STRAIN OF INFECTIOUS-BRONCHITIS VIRUS OF PASSAGE THROUGH CHICK-EMBRYO TRACHEA ORGAN-CULTURE

Two substrains derived from an uncloned 71st embryo (E71) passage and a cloned 71st embryo-10th chick embryo kidney cell (E71CEK10) passage of the Beaudette strain of avian infectious bronchitis virus were back-passaged through organ cultures of chick embryo trachea. The organ culture-passaged viruses had altered biological properties such as absence of or delayed lethality for chick embryos and lack or diminution of plaque-forming ability in chick embryo kidney monolayers but they showed no clear change of pathogenicity for 3-week-old chickens. These viruses regained their lethality for chick embryos, their cytopathic effects, and their plaque-forming ability in chick embryo kidney cells after they had been back-passaged through chick embryos, depending on the passage number. The results of cross neutralisation tests using the constant serum-variable virus method in chick embryos indicated little antigenic difference between the original virus and various host-passaged derivative strains. © 1979, Taylor & Francis Group, LLC. All rights reserved.