N-glycosylation of envelope glycoprotein gI is crucial for the duck plague virus proliferation and virulence

Abstract Duck plague virus (DPV) causes highly pathogenic duck plague, and the envelope glycoprotein gI, as one of the key virulence genes, has not yet had its critical virulence sites identified through screening. In this study, reverse genetics technology was utilized to specifically target the gI protein within the genome of the DPV. Four mutant strains of DPV with mutations in the N-glycosylation sites of the gI protein were designed and constructed, and these mutant strains were successfully rescued. Our results confirmed that three asparagine residues (N69, N78, and N265) of gI are N-glycosylation sites, and Western blot analysis substantiated that the glycosylation at each predicted N-glycosylation site was compromised. The deglycosylation of gI results in the misfolding of the protein and its consequent retention in the endoplasmic reticulum (ER). For the subsequent intracellular transport of gI within duck embryonic fibroblasts (DEFs), the carrying effect of its interacting protein gE is essential. Compared to the parental virus, the mutated virus exhibits a reduced intercellular transmission capability to 66.3%. In ducks, the deglycosylation of gI significantly reduces the replication of DPV in vivo, thereby impairing the virulence of DPV. This research marks the first successful generation of an attenuated DPV strain through targeted mutations at the N-glycosylation sites. The findings provide a foundational understanding of DPV pathogenesis and offer a basis for the development of live attenuated vaccines against the disease.