Stable Surface Display of a Conserved Influenza Mini-Ha Antigen in Saccharomyces Cerevisiae for Oral Delivery

Yeast surface display is a versatile microbial engineering strategy for recombinant protein presentation and oral antigen delivery. In this study, a conserved influenza hemagglutinin stem antigen (mini-HA) was displayed on the surface of Saccharomyces cerevisiae to evaluate the feasibility and stability of a yeast-based oral delivery system. A rationally engineered mini-HA derived from influenza A H1N1 was anchored to the yeast cell surface using the Aga1p-Aga2p display system. Efficient surface localization was confirmed by flow cytometry and confocal microscopy. The displayed antigen remained stably anchored following exposure to simulated gastric fluid and after heat inactivation at 60 °C, indicating favorable stability of the yeast surface display system under acidic and thermal stress conditions. Oral administration of the engineered yeast induced antigen-specific systemic IgG and mucosal secretory IgA responses in mice. In addition, antigen-specific lymphocyte proliferation and increased expression of IFN-γ and T-bet were observed, suggesting activation of both humoral and cellular immune responses. No significant adverse effects on body weight, serum biochemical parameters, or tissue histopathology were detected. These findings support the feasibility of using S. cerevisiae surface display for stable presentation and oral delivery of a conserved influenza antigen. The favorable stability and immunogenicity of the system support further development of yeast-based recombinant antigen delivery platforms.