ISOLATION OF MONOCLONAL-ANTIBODIES REACTING WITH THE CORE COMPONENT OF LIPOPOLYSACCHARIDE FROM RHIZOBIUM-LEGUMINOSARUM STRAIN-3841 AND MUTANT DERIVATIVES

Monoclonal antibodies reacting with the core oligosaccharide or lipid A component of Rhizobium lipopolysaccharide (LPS) could be useful for the elucidation of the structure and biosynthesis of this group of mac romolecules, Mutant derivatives of Rhizobium leguminosarum 3841 with L PS structures lacking the major O-antigen moiety were used as immunoge ns, and eight antibodies were selected for further study, All the anti bodies reacted with the fast-migrating species known as LPS-2 followin g gel electrophoresis of Rhizobium cell extracts. For four of these an tibodies, reactivity,vith affinity-purified LPS was lost after mild ac id hydrolysis, indicating that they probably recognized the core oligo saccharide component. The four other antibodies still reacted with aci d-treated LPS and may recognize the lipid A moiety, which is stable to mild acid hydrolysis. The pattern of antibody staining after gel elec trophoresis revealed differences in LPS-2 epitope structure between ea ch of the mutants and the wild type, Furthermore, for each of the muta nts the antibodies cross-reacted with a minor band that migrated more slowly than LPS-2; we have termed this more slowly migrating form LPS- 3. The majority of the antibodies also reacted with LPS from strain CE 109, a derivative of Rhizobium etli CE3, confirming that the LPS core antigens can be relatively conserved between strains of different Rhiz obium species. One of the antibodies isolated in this study (JIM 32) w as unusual because it appeared to react with all forms of LPS from str ain 3841 (namely, LPS-1, LPS-2, and LPS-3). Furthermore, JIM 32 reacte d positively with the LPS from many strains of Rhizobium tested (exclu ding the Rhizobium meliloti subgroup), JIM 32 did not react with repre sentative strains from Bradyrhizobium, Azorhizobium or other related b acterial species.