Engineering Saccharomyces cerevisiae for Surface Display of a Functional H5 Influenza Virus-Specific Nanobody

Nanobodies are characterized by their small size, high specificity, and strong affinity, making them promising antiviral agents. In this study, a dual-plasmid yeast surface display (YSD) system based on the Saccharomyces cerevisiae a-agglutinin (Aga1p-Aga2p) platform was evaluated for the functional presentation of H5-specific nanobody. To investigate the influence of fusion design on display performance, enhanced green fluorescent protein (EGFP) was fused to Aga2p in two different orientations. Both configurations enabled successful surface display, while the EGFP-AGA2 orientation showed significantly higher display efficiency than AGA2-EGFP (p < 0.001). This optimized configuration was subsequently used to display Nb10, a broadly neutralizing nanobody targeting the hemagglutinin (HA) protein of H5 influenza viruses. Indirect ELISA, immunofluorescence, and confocal microscopy confirmed successful surface localization of Nb10, while flow cytometry revealed 22.10% positive cells compared with 0.30% in the negative control (p < 0.001). In hemagglutination inhibition (HI) assays, the YSD-Nb10 strain exhibited an HI titer of 3log2, whereas no detectable HI activity was observed in the control strain. Collectively, these results demonstrate the feasibility of displaying a functional H5-specific nanobody using a dual-plasmid YSD system and highlight the importance of fusion orientation for efficient surface presentation, providing preliminary practical guidance for optimization of YSD applications.