LIVE ATTENUATED TEMPERATURE-SENSITIVE AVIAN INFECTIOUS BRONCHITIS VIRUS VACCINES AND PREPARATION AND USE THEREOF

摘要

The cold-adapted (ca) temperature-sensitive (ts)vaccine is prepared by serially passaging a suitablyselected virus (e.g. Arkansas-type DPI strain) througha culture medium at a suboptimal replication temperaturewhich is less than about 35°C, e.g. 28°C, andharvesting the live, cold-adapted mutant for formulationinto dosage units of, for example, about 10 3 toabout 10 5 EID50/bird. The ca ts mutant is much lessable to replicate at 40-42°C (internal avian bodytemperatures) than at the temperature of the bird'supper respiratory tract, which is below 40°C. Thevaccine can be administered by any of the usual techniques,including the spray technique. Vaccines ofthis invention appear to be very effective (immunogenic),but are also safe (non-pathogenic).