Use of a Novel Adjuvant in a Leptospira borgpetersenii Hardjo Vaccine to Induce a Cell-Mediated Immune Response

Infection of cattle with Leptospira borgpetersenii serovar Hardjo can have negative impacts on the cattle industry and pose the risk of transmission to other mammals, including humans. Current commercial vaccines used to protect against Leptospira serovar Hardjo are ineffective at providing long-term immunity, and a more cell-mediated immune response is thought to be necessary for lasting protection. IgG1 and IgG2 levels can be indicative of what type of a T cell response predominates; in a cell-mediated type 1 (Th1) immune response, interferon-ү (IFN-ү) secreted from helper T cells will stimulate B cells to class-switch to manufacture and secrete IgG2. In a humoral type 2 (Th2) immune response, helper T cells secrete interleukin-4 (IL-4) that stimulates B cells to class-switch to manufacture and secrete antibodies of the IgG1 isotype. In this study, a novel vaccine formulated with an oil-based adjuvant was shown to induce a stronger and more balanced cell-mediated response in comparison with current commercial serovar Hardjo vaccines. This was demonstrated by analyzing antibody levels in response to vaccination and challenge with Leptospira serovar Hardjo.