Relation of Japanese Xanthomonas campestris pv. vesicatoria with worldwide strains revealed with three specific monoclonal antibodies

Strains of Xanthomonas campestris pv. vesicatoria Dye 1978 (Xcv), the causal agent of bacterial spot, have been classified into two groups based on their ability to hydrolyze starch. Three monoclonal antibodies (MAbs), 7AH10, 5HB3, and 4AD2, were produced immunized against the living bacteria and were specific to and could distinguish Xcv strains able or unable to hydrolyze starch (Amy+ or Amy−). The MAb 7AH10, obtained against strain UPB141(Amy−) reacted in an enzyme-linked immunosorbent assay with all the Amy− strains (n = 19) and 1 of 11 Amy+ strains. Against Xcv 2625, an Amy− “unusual phenotype” strain, MAb 5HB3, recognized 97% of our worldwide collection of Xcvs (n = 30). Also against that strain, the MAb 4AD2 reacted with none of the homologous Amy− phenotypes and with 90% (n = 11) of the heterologous Amy+ phenotypes. For all the MAbs, cross reactions with other pathovars or species were less than 4% (n = 67). By assaying a Japanese collection of strains against the three MAbs, the Amy+ strains were distinguished from the Amy− strains, and their relation with other world strains could be demonstrated. All the MAbs reacted with the lipopolysaccharide fraction of the bacterial cell wall during immunoblotting.