SEQUENCE CONSERVATION IN THE ATTACHMENT GLYCOPROTEIN AND ANTIGENIC DIVERSITY AMONG BOVINE RESPIRATORY SYNCYTIAL VIRUS ISOLATES

Partial nucleotide sequences were determined from the coding regions o f the attachment glycoprotein (G) mRNAS of eight isolates of bovine re spiratory syncytial virus (BRSV). The antigenic characteristics of 18 field and reference isolates were analyzed using the reactivity patter ns of monoclonal antibodies (MAbs) directed against the human respirat ory syncytial virus (HRSV) and BRSV G, fusion protein (F), nucleoprote in (N), and phosphoprotein (P), by radioimmunoprecipitation and immuno fluorescence assays. The MAb reaction patterns demonstrated some rando m antigenic differences among the isolates, but for the most part were cross-reactive to the viral protein epitopes, especially on the F pro tein. Structural differences in the F and P proteins were observed amo ng BRSV isolates; the P protein migrated at three different apparent m olecular weights on PAGE gels, Antigenic and structural variation occu rs among isolates, however, the structural differences in the P protei n did not correlate with the antigenic differences among the F, N and P proteins. The G mRNA nucleotide sequence identities were high, rangi ng from 94.1 to 99.9%, and the predicted amino acid sequence identitie s ranged from 89.9 to 99.6%. Variance was due to substitution point mu tations. The G protein ectodomains contained areas of sequence diverge nce flanking a highly conserved region, with four cysteine residues, w hich is analogous to the putative HRSV receptor binding domain. The hi gh sequence and amino acid identities and random antigenic diversity a mong the isolates indicates that the BRSV isolates analyzed belong in a monophyletic group.