Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/1998
Publication Date: N/A
Interpretive Summary: Leptospirosis is a bacterial infection and an important cause of abortion and stillbirth in animals. Vaccines available for protection of cattle from leptospirosis have been shown to be marginally effective at preventing some types of leptospirosis. Therefore, it is important to search for proteins produced by the bacteria that can be incorporated into vaccines for prevention of this disease. We report here the identification and characterization of a novel protein located on the surface of the organism. The protein is present on bacteria growing in the laboratory but not in bacteria growing in the animal. This information will be useful to scientists trying to understand how this group of organisms causes disease and to develop better vaccines to protect livestock from leptospirosis.
Technical Abstract: We report the cloning of the gene encoding a 36-kDa leptospiral outer membrane lipoprotein, designated LipL36. A Lambda-Zap II library containing EcoRI fragments of Leptospira kirschneri DNA was screened, and a 2.3-kb DNA fragment, which contained the entire structural lipL36 gene, was identified. LipL36 is solubilized by Triton X-114 extraction of L. kirschneri; phase separation results in partitioning of LipL36 exclusively into the detergent phase. Processing of LipL36 is inhibited by globomycin, a selective inhibitor or lipoprotein signal peptidase. LipL36 appears to be localized exclusively to the periplasmic face of the leptospiral outer membrane. In early log phase cultures, LipL36 is one of the most abundant L. kirschneri proteins. Beginning in mid log phase, LipL36 expression is downregulated. LipL36 expression in vivo was evaluated by examining the humoral immune response to leptospiral antigens in the hamster model of leptospirosis. Hamsters surviving challenge with culture-adapted virulent L. kirschneri generate a strong antibody response to LipL36. In contrast, sera from hamsters surviving challenge with host-adapted L. kirschneri do not recognize LipL36. These results suggest that LipL36 expression is downregulated during late log phase growth and mammalian infection.