A CHARACTERIZATION OF EPITOPES ON POTATO LEAFROLL VIRUS COAT PROTEIN

A panel of ten stable hybridoma cell lines secreting monoclonal antibodies (MAbs) specific for potato leafroll virus (PLRV) antigen, was produced in two fusion experiments with murine splenic and myeloma cells. Using different ELISA procedures and Western blotting it was shown that one MAb detected a continuous epitope and nine MAbs reacted with conformation-dependent ones. The conformation-dependent epitopes could be separated into two groups after alkaline treatment of the virions. The MAbs were further differentiated in competitive binding assays. Within the group of MAbs reacting with epitopes not sensitive to alkaline degradation, only two MAbs were directed to the same epitope. The MAbs detecting epitopes formed by the quaternary protein structure or by a protein subunit configuration sensitive to alkaline degradation, displayed positive cooperative binding among each other. In total, a minimum number of nine different, but overlapping, epitopes on the PLRV coat protein could be revealed. The immune response to PLRV antigen in rabbit appeared to be directed mainly towards epitopes recognized by three MAbs. Most MAbs displayed heterologous reactivity to other luteoviruses, i.e., tomato yellow top virus (TYTV), beet western yellow virus (BWYV), beet mild yellowing virus (BMYV), bean leafroll virus (BLRV), and different strains of barley yellow dwarf virus. Three MAbs solely reacted with PLRV and TYTV. Six MAbs gave different reaction patterns in these tests; one of these MAbs differentiated BMYV from BWYV, and another detected a common epitope on PLRV and BLRV, a serological relationship not reported previously to our knowledge.