ANTIGENIC ANALYSIS OF THE F-PROTEIN OF THE BOVINE RESPIRATORY SYNCYTIAL VIRUS - IDENTIFICATION OF 2 DISTINCT ANTIGENIC SITES INVOLVED IN FUSION INHIBITION

From two independent fusions, fifteen MAbs directed to the F protein o f the bovine respiratory syncytial virus (BRSV) were characterized by radioimmunoprecipitation assays. Competition binding assays among thes e MAbs identified two distinct antigenic sites (A and B) and one overl apping site (AB). Ah of the MAbs specific to epitopes belonging to sit e A neutralized the infectivity of the virus in vitro and recognized h uman and bovine RSV strains. Only two out of the five MAbs directed to epitopes of site B were neutralizing and three reacted with ah of the RSV strains tested, suggesting that the epitopes constituting this do main present heterogeneous characteristics. In each of sites A and B, one of the neutralizing MAbs also inhibited cell fusion. The biologica l relevance of these domains was established by competing representati ve MAbs and sera from BRSV-infected calves.