SEROLOGICAL AND GENETIC-CHARACTERIZATION OF BOVINE RESPIRATORY SYNCYTIAL VIRUS (BRSV) INDICATES THAT DANISH ISOLATES BELONG TO THE INTERMEDIATE SUBGROUP - NO EVIDENCE OF A SELECTIVE EFFECT ON THE VARIABILITY OF G-PROTEIN NUCLEOTIDE-SEQUENCE BY PRIOR CELL-CULTURE ADAPTION AND PASSAGES IN CELL-CULTURE OR CALVES

Danish isolates of bovine respiratory syncytial virus (BRSV) were char acterised by nucleotide sequencing of the G glycoprotein and by their reactivity with a panel of monoclonal antibodies (MAbs). Among the six Danish isolates, the overall sequence divergence ranged between 0 and 3% at the nucleotide level and between 0 and 5% at the amino acid lev el. Sequence divergences of 7-8%, 8-9% and 2-3% (nucleotide) and 9-11% , 12-16% and 4-6% (amino acid) were obtained in the comparison made be tween the group of Danish isolates and the previously sequenced 391-2U SA, 127UK and 220-69Bel isolates, respectively. Phylogenetic analysis showed that the Danish isolates formed three lineages within a separat e branch of the phylogenetic tree. Nevertheless, the Danish isolates w ere closely related to the 220-69Bel isolate, the prototype of the int ermediate antigenic subgroup. The sequencing of the extracellular part of the G gene of additional 11 field BRSV viruses, processed directly from lung samples without prior adaption to cell culture growth. reve aled sequence variabilities in the range obtained with the propagated virus. In addition, several passages in cell culture and in calves had no major impact on the nucleotide sequence of the G protein. These fi ndings indicated that the previously established variabilities of the G protein of RS virus isolates were not attributable to mutations indu ced during the propagation of the virus. The reactivity of the Danish isolates with G protein-specific MAbs were similar to that of the 220- 69Bel isolate. Furthermore, the sequence of the immunodominant region was completely conserved among the Danish isolates on one side and the 220-69Bel isolate on the other. When combined, these data strongly su ggested that the Danish isolates belong to the intermediate subgroup. (C) 1998 Elsevier Science B.V. All rights reserved.