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ABSTRACTLeptospirosis, a worldwide zoonosis, lacks an effective, safe, and cross-protective vaccine. LipL32, the most abundant, immunogenic, and conserved surface lipoprotein present in all pathogenic species ofLeptospira, is a promising antigen candidate for a recombinant vaccine. However, several studies have reported a lack of protection when this protein is used as a subunit vaccine. In an attempt to enhance the immune response, we used LipL32 coupled to or coadministered with the B subunit of theEscherichia coliheat-labile enterotoxin (LTB) in a hamster model of leptospirosis. After homologous challenge with 5× the 50% lethal dose (LD50) ofLeptospira interrogans, animals vaccinated with LipL32 coadministered with LTB and LTB::LipL32 had significantly higher survival rates (P< 0.05) than animals from the control group. This is the first report of a protective immune response afforded by a subunit vaccine using LipL32 and represents an important contribution toward the development of improved leptospirosis vaccines.

Leptospirosis is a global zoonosis caused by pathogenic Leptospira spp. In this study, we characterized two Leptospira kirschneri serogroup Pomona serovar Mozdok isolates, one obtained from a dog and the other from a patient with severe leptospirosis, 4 years later. Histopathological analysis showed that both isolates caused severe tissue damage when used to infect hamsters. While L. kirschneri serogroup Pomona serovar Mozdok is endemic in animals in Europe, there is only one report of human leptospirosis in the literature. Although strains belonging to L. kirschneri serogroup Pomona have been identified in cases of human leptospirosis in Europe, serovar Mozdok has not yet been implicated. The 4-year interval between isolations and the fact that this is the first report of serovar Mozdok as the causative agent of human leptospirosis in the southern hemisphere, demonstrates its epidemiological importance to public health. Moreover, the presence of serovar Mozdok in Brazil has the potential to affect vaccine and diagnostic test development.

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Leptospirosis is the most widespread zoonosis in the world. Current vaccines are based on whole-cell preparations that cause severe side effects and do not induce satisfactory immunity. In light of the leptospiral genome sequences recently made available, several studies aimed at identification of protective recombinant immunogens have been performed; however, few such immunogens have been identified. The aim of this study was to evaluate 27 recombinant antigens to determine their potential to induce an immune response protective against leptospirosis in the hamster model. Experiments were conducted with groups of female hamsters immunized with individual antigen preparations. Hamsters were then challenged with a lethal dose of Leptospira interrogans. Thirteen antigens induced protective immune responses; however, only recombinant proteins LIC10325 and LIC13059 induced significant protection against mortality. These results have important implications for the development of an efficacious recombinant subunit vaccine against leptospirosis.