José R. C. M.
van der Wolf
First, second, and fifth authors: Laboratory for Monoclonal Antibodies, P.O. Box 8123, 6700 ES Wageningen, the Netherlands; and third and fourth authors: DLO Research Institute for Plant Protection (IPO), P.O. Box 9060, 6700 GW Wageningen, the Netherlands
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Accepted for publication 20 April 1998.
Recombinant single-chain antibodies (scFvs) against the lipopolysaccharide of Ralstonia solanacearum (biovar 2, race 3) were successfully selected by phage display from a large combinatorial antibody library. Characterization with regard to cross-reaction and use in routine immunoassays showed that the selected antibodies had improved characteristics when compared with the polyclonal antiserum that is currently used for brown rot diagnosis of potato in the Netherlands. The isolated monoclonal scFvs reacted in both enzyme-linked immunosorbent assay (ELISA) and immunofluorescence cell staining with all race 3 strains tested, but with only some strains belonging to other races. Furthermore, only a few cross-reactions with saprophytic bacteria, which also cross-reacted with polyclonal antisera, were observed. Using ELISA, one of the recombinant antibodies detected as few as 5 × 103 bacteria in potato tuber extracts. Therefore, this antibody is potentially useful for detection of R. solanacearum race 3.
© 1998 The American Phytopathological Society