LOCATION OF NEUTRALIZING EPITOPES ON THE G-PROTEIN OF BOVINE EPHEMERAL FEVER RHABDOVIRUS

The surface glycoprotein G is the major neutralizing and protective an tigen of bovine ephemeral fever rhabdovirus (BEFV). Twelve neutralizin g MAbs against BEFV strain BB7721 were used to select 33 neutralizatio n escape mutants. The mutants had been classified previously into thre e major antigenic sites (G1-G3) based on their cross-neutralization pa tterns. The nucleotide sequence of the entire extracellular domain of the G protein gene was determined for all mutants. Each contained a si ngle nucleotide change leading to a single amino acid substitution. Th e 16 mutants assigned to the linear antigenic site G1 mapped to aa 487 -503 of the 623 aa G protein, Results of antibody binding to several o verlapping octapeptides covering this region mapped the sequence of tw o common minimal B cell epitopes recognized by the five G1 MAbs to (48 8)EEDE(491) and (499)NPHE(502). Site G2 mutations mapped either at aa 169 or 187, The 12 mutants representing antigenic site G3 (G3a and G3b ) mapped to aa 49, 57, 218, 229 and 265, indicating that this site is likely to combine complex discontinuous epitopes, Comparison of the de duced amino acid sequence from five BEFV field isolates and 887721 ide ntified aa 218 to be critical for the site G3a neutralization, Alignme nt of the glycoproteins of rabies virus, vesicular stomatitis Indiana virus, vesicular stomatitis New Jersey virus, infectious haematopoieti c necrosis virus and BEFV revealed similarities in the location of the neutralizing epitopes and extensive conservation of cysteine residues , suggesting that basic elements of the folded structure of these glyc oproteins are preserved.