Evaluation of the Leptospira interrogans Outer Membrane Protein OmpL37 as a Vaccine Candidate

The identification of potential vaccine candidates against leptospirosis remains a challenge. However, one such candidate is OmpL37, a potentially surface-exposed antigen that has the highest elastin-binding ability described to date, suggesting that it plays an important role in host colonization. In order to evaluate OmpL37's ability to induce a protective immune response, prime-boost, DNA and subunit vaccine strategies were tested in the hamster model of lethal leptospirosis. The humoral immune response was evaluated using an indirect ELISA test, and the cytokine profile in whole blood was determined by quantitative real-time PCR. Unlike the DNA vaccine, the administration of recombinant OmpL37 induced a strong IgG antibody response. When individually administrated, both formulations stimulated a TNF-α mediated inflammatory response. However, none of the OmpL37 formulations or vaccination strategies induced protective immunity. Further studies are required towards the identification of new vaccine targets against leptospirosis.