Serological and molecular characterization of three enteric isolates of infectious bronchitis virus of chickens

Three coronaviruses isolated from the intestines of laying chickens were partially characterized. Serological and molecular assays indicated that the enteric coronaviruses are infectious bronchitis virus (IBV) isolates. Although the three isolates were recovered from three unrelated chicken flocks, their RNase T1-resistant oligonucleotide fingerprints were almost identical. The three isolates were not neutralized by antisera specific to IBV serotype Connecticut, but their RNase T1-resistant oligonucleotide fingerprints closely matched the fingerprints of strain Conn-46, a Connecticut serotype. This and the co-fingerprinting data suggested that the three field isolates may have emerged from the Connecticut virus through mutation(s). The mutation(s) apparently involved the S1 protein gene that determines the virus serotype.