Heterologous Expression of the Antiviral Lectin Griffithsin in Probiotic Saccharomyces boulardii and In Vitro Characterization of Its Properties

In this study, the probiotic yeast <i>Saccharomyces boulardii</i> was engineered to secrete the antiviral lectin griffithsin. Twelve genetic tools with the griffithsin gene were cloned into the vector pSF-TEF1-URA3 and introduced into <i>S. boulardii</i>. In the recombinant strains, a 16.9 kDa band was detected using SDS-PAGE and further recognized by griffithsin antibody with Western blotting. <i>S. boulardii</i> strains FM, FT, HC, and HE with a high yield of griffithsin were acquired for property characterization in vitro. The four recombinant strains displayed a similar growth pattern to that of the control strains, while their morphological characteristics had changed according to scanning electron microscopy. In simulated gastrointestinal digestive fluids, the survival rates of <i>S. boulardii</i> FM, FT, and HC were significantly decreased (86.32 ± 1.49% to 95.36 ± 1.94%) compared with those of the control strains, with survival rates between 95.88 ± 0.00% and 98.74 ± 1.97%. The hydrophobicity of <i>S. boulardii</i> FM, the strain with the highest griffithsin production, was significantly increased to 21.89 ± 1.07%, and it exhibited a reduced auto-aggregation rate (57.64 ± 2.61%). Finally, Vero cells infected with porcine epidemic diarrhea virus (PEDV) were used to evaluate the strains' antiviral activity, and the rate at which <i>S. boulardii</i> FM inhibited PEDV reached 131.36 ± 1.06%, which was significantly higher than that of the control group.