Leptospiral immunoglobulin-like proteins elicit protective immunity.

The identification of new vaccine candidates for leptospirosis is of great interest. This paper describes the identification of two homologous immunogenic proteins, LigA-m and LigB-m, of Leptospira interrogans serovar manilae strain UP-MMC-NIID, which show strong similarity with LigA found recently in L. interrogans serovar pomona. Southern blot analysis indicated the conservation of the lig genes among pathogenic leptospires. LigA-m protein was shown to be a surface-exposed lipoprotein expressed during in vitro culture. Both LigA-m and LigB-m induced protective immunity against a challenge with a homologous serovar of L. interrogans in mice. Furthermore, patients' sera infected with heterologous serovars' strains contained antibodies against LigA-m and LigB-m. Our results suggest that LigA-m and LigB-m proteins are new vaccine candidates for the prevention of leptospirosis.