CHARACTERIZATION OF FIELD STRAINS OF GROUP-A BOVINE ROTAVIRUSES BY USING POLYMERASE CHAIN REACTION-GENERATED G-TYPE AND P-TYPE-SPECIFIC CDNA PROBES

Dot and Northern blot hybridization assays were used to analyze field strains of group A bovine rotaviruses (BRVs) by using nucleic acid pro bes representing P and G type specificities. The probes were prepared by polymerase chain reaction amplification of hyperdivergent regions o f the cloned VP4 (nucleotides 211 to 686) and VP7 (nucleotides 51 to 3 92) genes from four serotypically distinct (in P or G types) strains o f rotaviruses: NCDV (G6, P1), IND (G6, P5), 69M (G8, P10), and Cr (G10 , P11). The P and G type cDNA probes were radiolabeled with [P-32]dCTP and hybridized with RNA extracted from reference cell culture-passage d rotavirus strains or the field samples. The field samples were obtai ned from young diarrheic calves from Ohio, Nebraska, Washington State, and Canada. The cDNA probes were specific for their respective G or P types on the basis of analysis of known P and G type reference strain s. The G typing analysis of 102 field samples revealed that 36.3% (37 of 102) were G6, 2.9% (3 of 102) were G8, 12.7% (13 of 102) were G10, and 23.5% (24 of 102) were untypeable. The P typing results for 93 sam ples indicated that 2.2% (2 of 93) were P1 (NCDV-like), 20.4% (19 of 9 3) were P5 (UK-like), 9.3% (10 of 93) were P11 (B223-like), and 40.8% (38 of 93) were untypeable. This is the first report of the identifica tion among BRV strains in North America of a G type other than G6 or G 10. Our report further confirms that G6, P5 rotaviruses are predominan t among the BRV field strains that we examined, and the P types of the se strains differ from that of the BRV vaccine strain used in the Unit ed States (G6, P1). The large number of untypeable G (23.5%) and P (40 .8%) types suggests that other or new P and G types exist among BRV fi eld strains.