Control of immunologically crossreactive leptospiral infection by administration of lipopolysaccharides from a nonpathogenic strain of Leptospira biflexa

In our previous paper (Matsuo, K,, Isogai, E,, and Araki, Y,, Carbohydr. Re s., 328: 517-524, 2000), antigenic polysaccharides obtained from the lipopo lysaccharide (LPS) fraction of a nonpathogenic leptospira, Leptospira bifle xa patoc Patoc I, are shown to be broadly crossreactable with most rabbit a ntisera elicited by immunization with various pathogenic leptospires, The r esult led us to test a protective effect of the same LPS in a hamster model system by heterologously challenging with a pathogenic leptospira, L. inte rrogans manilae UP-MMG, Firstly, a similarity in the antigenic epitopes oft . biflexa and L, interrogans was confirmed by the following assays. In the microscopic agglutination test (MAT), a hamster antiserum elicited by immun ization with the L, biflexa-LPS preparation was shown to agglutinate cells oft. interrogans, Contrarily, in the enzyme-linked immunosorbent assay (ELI SA), the L, biflexa-LPS preparation was shown to crossreact with a hamster antiserum elicited by immunization with whole cells oft, interrograns. Thes e results suggest that the same or closely related antigens may be present on the cell surfaces of both L, biflexa patoc Patoc I and L. interrogans ma nilae UP-MMG, Furthermore, in a protective assay, the prior administration of a L, biflexa-LPS preparation resulted in raising a protective response i n hamsters against challenge by L, interrogans without any side effect. The protective effect was strongly dependent on the dose amounts and/or admini stration times of L, biflexa-LPS. Thus, L. biflexa-LPS preparations can use as a potent vaccine against leptospirosis caused by various Leptospires.