Design of an oral vaccine against Salmonella pullorum using protein surface display on bioengineered Saccharomyces cerevisiae.

Salmonella enterica subsp. Salmonella Pullorum is a concerned pathogenic microorganism that poses a serious threat to the global poultry industry due to high mortality in chicken. Acquired immunity is considered the most effective means to prevent and control Salmonella pullorum. However, safe and effective vaccines are still lacking worldwide. In this study, Saccharomyces cerevisiae was used as a chassis to design an oral vaccine for pullorum by displaying Salmonella fimbriae and outer membrane proteins on its surface. The results demonstrated that the engineered yeast EY-01 exhibited strong antigenicity as identification and capture by specific antibodies. In addition, oral administration of EY-01 significantly stimulated a 1.4- to 2.7-fold increase in antibody (IgG/A) and immune factors levels (IL-1β/2/4, IFN-γ) in chicks without affecting the growth performance. The ratios of CD4⁺/CD3⁺ and CD8⁺/CD3⁺ T cell subsets in peripheral blood were significantly increased by 2.1-fold. Importantly, 37.5% of chicks were protected from challenge with Salmonella pullorum after oral administration of EY-01. And the Salmonella load in various tissues, especially muscle, was significantly reduced by 7.2%-22.4%. Collectively, EY-01 is a safe and effective oral vaccine to against Salmonella infection in chicks and such surface display-based vaccine is potential to be used for decreasing the poultry diseases.