Leptospirosis Vaccine: Search for Subunit Candidates

Subunit vaccines are a potential intervention strategy against leptospirosis, which is a major public health problem in developing countries. Thus far, several proteins have been evaluated as potential vaccine candidates, but all those tested in aluminum hydroxide adjuvant have failed to protect animals against lethal challenge. Seven new leptospiral lipoproteins were evaluated as vaccine candidates. The coding sequences of these lipoproteins were amplified by PCR from Leptospira interrogans serovar Copenhageni, strain Fiocruz L1-130, cloned and expressed in Escherichia coli. The purified proteins were adsorbed in aluminum adjuvant and used in the immunization of four to six weeks old hamsters. After two doses of 60 μg of recombinant protein, hamsters were challenged with a lethal dose of L. interrogans. All seven tested proteins failed to fully protect the animals from disease or death. Further study must be undertaken toward developing an efficient subunit vaccine against leptospirosis for humans, livestock and pets.