DEVELOPMENT OF SPECIFIC RECOMBINANT MONOCLONAL-ANTIBODIES AGAINST THELIPOPOLYSACCHARIDE OF RALSTONIA-SOLANACEARUM RACE-3

Recombinant single-chain antibodies (scFvs) against the lipopolysaccha ride of Ralstonia solanacearum (biovar 2, race 3) were successfully se lected by phage display from a large combinatorial antibody library. C haracterization with regard to cross-reaction and use in routine immun oassays showed that the selected antibodies had improved characteristi cs when compared with the polyclonal antiserum that is currently used for brown rot diagnosis of potato in the Netherlands. The isolated mon oclonal scFvs reacted in both enzyme-linked immunosorbent assay (ELISA ) and immunofluorescence cell staining with ail race 3 strains tested, but with only some strains belonging to other races. Furthermore, onl y a few cross-reactions with saprophytic bacteria, which also cross-re acted with polyclonal antisera, were observed. Using ELISA, one of the recombinant antibodies detected as few as 5 x 10(3) bacteria in potat o tuber extracts. Therefore, this antibody is potentially useful for d etection of R. solanacearum race 3.