Recombinant Mycobacterium bovis BCG expressing the LipL32 antigen of Leptospira interrogans protects hamsters from challenge.

The bacillus Calmette--Guerin (BCG), a live attenuated Mycobacterium bovis strain is considered a promising candidate as a vector system for delivery of foreign antigens to the immune system. The gene coding for the Leptospira interrogans external membrane protein LipL32, a highly immunogenic antigen found in all pathogenic leptospira, was cloned into several mycobacterial vectors for expression in BCG. Hamsters immunized with recombinant BCG (rBCG) expressing LipL32 were protected against mortality (P<or=0.05) upon challenge with a lethal inoculum of L. interrogans serovar Copenhageni. Autopsy examination did not reveal macroscopic or histological evidence of disease in rBCG immunized hamsters that survived lethal challenge. The data presented here further enhance the status of LipL32 as a promising candidate antigen for use in the control of leptospirosis, when presented to the immune system by an appropriate delivery system.