Pepscan mapping of autophagy-inducing peptides of the glycoprotein of infectious hematopoietic necrosis virus and the effect on viral replication in vitro

Abstract

Infectious hematopoietic necrosis virus (IHNV) is the main pathogen threatening the aquaculture used by the salmonid industry worldwide. Our previous study showed that IHNV infection induced autophagy activation in epithelioma papulosum cyprinid (EPC) cells, but the relationship between IHNV infectivity and autophagy induction had not yet been addressed. To investigate this question, IHNV was inactivated by ultraviolet (UV) irradiation and the complete protein sequence of IHNV glycoprotein was segmented by pepscan into 43 peptides. The induction of autophagy was analyzed by transmission electron microscopy, confocal fluorescence microscopy, flow cytometry, and western blotting. The results show that UV-inactivated IHNV and viral glycoprotein can induce autophagosome formation, obvious punctate clusters of LC3-II and an elevated LC3-II to LC3-I ratio. All these results suggested that UV-inactivated IHNV and viral glycoprotein can induce autophagy independently of viral infectivity. The flow cytometry and western blotting results show that EPC cells treated with peptide p108 displayed an obvious induction of autophagy (LC3-II increased by approximately 2.5-fold). The cells pretreated with peptide p108 showed a significant inhibition of intracellular viral mRNA replication levels and extracellular viral yields of IHNV. These results suggest that peptide p108 could be a promising drug for use in IHNV prevention, and they lay a new foundation for anti-IHNV drug development.