Oral Administration of Recombinant Expressing Ovalbumin-CPE Fusion Protein Induces Antibody Response in Mice.

, a subspecies of , is a well-known eukaryotic probiotic with many benefits for human health. In the present study, a recombinant strain of was prepared to use as a potential oral vaccine delivery vehicle. In this sense, a ura3 auxotroph strain of CNCM I-745 (known as HANSEN CBS 5926, Yomogi) was generated using CRISPR/Cas9 methodology. Then a gene construct encoding a highly immunogenic protein, ovalbumin (OVA), was prepared and transformed into the . To facilitate the transport of the recombinant immunogen across the intestinal barrier, a claudin-targeting sequence from enterotoxin (CPE) was added to the C-terminus of the expression cassette. The recombinant strain expressing the OVA-CPE fusion protein was then administered orally to a group of mice, and serum IgG and fecal IgA levels were evaluated by ELISA. Our results demonstrated that anti-OVA IgG in serum significantly increased in test group ( < 0.001) compared to control groups (receiving wild type or PBS), and the fecal IgA titer was significantly higher in test group ( < 0.05) than control groups. In parallel, a recombinant strain expressing the similar construct lacking C-terminal CPE was also administered orally. The result showed an increased level of serum IgG in group receiving yeasts expressing the CPE negative construct compared to control groups; however, the fecal IgA levels did not increase significantly. In conclusion, our findings indicated that the yeast , as a delivery vehicle with possible immunomodulatory effects, and c-CPE, as a targeting tag, synergistically assist to stimulate systemic and local immunity. This proposed recombinant system might be useful in the expression of other antigenic peptides, making it as a promising tool for oral delivery of vaccines or therapeutic proteins.