Intracellularly delivered nanobody targeting the nucleocapsid protein effectively inhibits porcine deltacoronavirus replication

of 6.712 μM and a selectivity index of 11.98, demonstrating potent antiviral efficacy and favorable safety. Together, our results demonstrate that N protein-specific nanobodies represent a promising antiviral strategy against PDCoV infection, and that cell-penetrating peptide-mediated nanobody delivery provides a feasible approach for intracellular targeting of viral replication machinery.