Structural characterization and antiviral activity of lentinan from Lentinus edodes mycelia against infectious hematopoietic necrosis virus

A novel lentinan (LNT-I) was extracted from Lentinus edodes mycelia, and purified by an anion-exchange DEAE cellulose column and Sephadex G-200 gel. The structural characterization of LNT-I was determined by gas chromatography-mass spectrometry, high performance gel permeation chromatography, Fourier transform infrared spectrometry and 1D-nuclear magnetic resonance spectroscopy. The results showed that LNT-I was a beta-(1 -> 3)-glucan backbone with-(1 -> 6)-glucosyl side-branching units terminated by mannosyl and galactosyl residues, and its molecular weight was 3.79 x 10(5) Da. LNT-I consisted of glucose, mannose and galactose with the molar ratio of 19.26:1.20:1.00. LNT-I represented the prominent antiviral activity to IHNV at MOI of 0.05 and 0.10, respectively. Direct inactivation and the antiviral ability in pre-addition, co-addition and post-addition to IHNV (MOI of 0.05) were 62.34%, 39.60%, 53.63% and 82.38%, respectively under 100 mu g/mL of LNT-I. Antiviral mechanisms of LNT-I mainly involved in the direct inactivation and the inhibition of viral replication. Moreover, LNT-I significantly down-regulated the expression level of TNF-alpha, IL-2 and IL-11, and up-modulated the expression levels of IFN-1 and IFN-gamma after challenging with IHNV. The results indicated that the inhibitory effects of LNT-I on IHNV infection were possibly attributed to its regulation of the innate immune responses and specific immunity. (C) 2018 Elsevier B.V. All rights reserved.