IMMUNOCHEMICAL STUDIES OF OPSONIC EPITOPES OF THE LIPOPOLYSACCHARIDE OF LEPTOSPIRA-INTERROGANS SEROVAR HARDJO

Leptospiral lipopolysaccharides (LPS) are the main antigens responsibl e for immunity in leptospirosis. In this investigation we studied the nature of the antigenic determinants of LPS extracted from Leptospira interrogans serovar hardjo (reference strain Hardjoprajitno). The reac tions of anti-LPS monoclonal antibodies (mAbs) MUM/F1-4/hardjo (IgM) a nd MUM/F1-6/hardjo (IgG) with whole cell lysates in Western immunoblot ting analysis were unaffected by proteinase K treatment. Periodate tre atment of the LPS destroyed the binding of MUM/F1-6/hardjo but preserv ed that of MUM/F1-4/hardjo. Alkaline phosphatase decreased significant ly the binding of MUM/F1-4/hardjo to the LPS but only slightly that of MUM/F1-6/hardjo. On the other hand, phosphodiesterase totally destroy ed the binding capacity of both monoclonal antibodies in enzyme immuno assays (EIA). A number of mono- and oligosaccharides was used in EIA i nhibition studies. Mannose-6-phosphate and galactose-6-phosphate inhib ited the binding of MUM/F1-4/hardjo (50% inhibition at a concentration of 5 mM) to the antigen, but glucose-6-phosphate did not. Galactosami ne and mannosamine inhibited the binding of MUM/F1-6/hardjo (50% inhib ition at a concentration of 3-4 mM), whereas only a weak inhibition wa s observed with glucosamine. In contrast, N-acetylated amino sugars di d not show any inhibition. An O-acetyl group also appears to be involv ed in the antigen-antibody binding process.