DOT-BLOT HYBRIDIZATION USING DIGOXIGENIN-LABELED CDNA PROBE COMPLEMENTARY TO THE S1 GENE OF AVIAN INFECTIOUS-BRONCHITIS VIRUS PERMITS DISCRIMINATION BETWEEN VIRUS-STRAINS

Digoxigenin-dUTP-labeled DNA probe was prepared from a cDNA clone comp lementary to the gene encoding S1 region of the spike protein of infec tious bronchitis coronavirus (IBV) strain M41. The probe exclusively r eacted with four strains at 56-degrees-C which were grouped to the sam e serotype as the strain used for the probe. In contrast, at 68-degree s-C, the probe reacted only with the homologous strain and did not rea ct even with the strains belonging to the same serotype. The dot-blot hybridization thus appeared serotype-specific at 56-degrees-C and stra in-specific at 68-degrees-C. In addition, it was revealed that the S1 gene has some nucleotide sequence variation even among strains in the same serotype. This technique should be applied to determining serotyp es of the virus isolates and to differentiating field isolates from th e vaccine strain.