Saccharomyces boulardii ingestion increases the humoral response of a DNA vaccine against leptospirosis in mice

Background DNA vaccines are a good option to generate a desired antigen using the cellular machinery of the vaccinated subject. This kind of vaccine can induce both of the humoral and cellular immune response, and show high stability and easy working, as well as offer a low-cost production. and safety for immune compromised patients [1]. However, some disadvantages, such as the low transfection rate and low immunogenicity, makes necessary the use of multiple doses [2,3]. Therefore, several studies have been conducted trying to increase the immune response generated by the DNA vaccines. Sacharomyces boulardii, a probiotic yeast that is capable to increase the host immune response [4], was not previously evaluated as an adjuvant for DNA vaccines. Thereby, in the present study we evaluated the S. boulardii capacity to increase the humoral response of mice using DNA vaccines against a fragment of the leptospiral antigen LigAcloned in the mammalian expression plasmid pTARGET [4,5].