Comparison of three different leptospiral vaccines for induction of a type 1 immune response to Leptospira borgpetersenii serovar Hardjo.

Leptospira serovar Hardjo are bacterial pathogens of cattle that cause zoonotic infections of humans. Monovalent serovar Hardjo vaccines protect cattle from serovar Hardjo while pentavalent vaccines do not even though they contain serovar Hardjo organisms. Here, cattle vaccinated with either of two monovalent vaccines had lymphocytes that made interferon-gamma (IFN-gamma) and IgG(1) and IgG(2) antibodies to Hardjo antigen while those from cattle vaccinated with a pentavalent Leptospira vaccine did not. IFN-gamma-producing cells were mainly CD4(+), but included CD8(+) and gamma delta TCR(+) cells. Despite their monovalent composition, those vaccines also induced IFN-gamma responses to serovar Grippotyphosa antigens. Thus, induction of a type 1 immune response is consistent with protective immunity to serovar Hardjo infections.