Oral immunization with Escherichia coli expressing a lipidated form of LigA protects hamsters against challenge with Leptospira interrogans serovar Copenhageni.

Leptospirosis is a potentially fatal zoonosis transmitted by reservoir host animals that harbor leptospires in their renal tubules and shed the bacteria in their urine. Leptospira interrogans serovar Copenhageni transmitted from Rattus norvegicus to humans is the most prevalent cause of urban leptospirosis. We examined L. interrogans LigA, domains 7 to 13 (LigA7-13), as an oral vaccine delivered by Escherichia coli as a lipidated, membrane-associated protein. The efficacy of the vaccine was evaluated in a susceptible hamster model in terms of the humoral immune response and survival from leptospiral challenge. Four weeks of oral administration of live E. coli expressing LigA7-13 improved survival from intraperitoneal (i.p.) and intradermal (i.d.) challenge by L. interrogans serovar Copenhageni strain Fiocruz L1-130 in Golden Syrian hamsters. Immunization with E. coli expressing LigA7-13 resulted in a systemic antibody response, and a significant LigA7-13 IgG level after the first 2 weeks of immunization was completely predictive of survival 28 days after challenge. As in previous LigA vaccine studies, all immunized hamsters that survived infection had renal leptospiral colonization and histopathological changes. In summary, an oral LigA-based vaccine improved survival from leptospiral challenge by either the i.p. or i.d. route.