The Regulation Effect And Mechanism Of Hericium Erinaceus Polysaccharide On Intestinal Mucosal Immune Suppression Of Muscovy Ducks Induced By Reovirus

Hericium erinaceus polysaccharide(HEP)consists of the following characters:virus-resistance,aggrandizement for immunity and promotionfor gastrointestinal epithelialmucosal regeneration and repair.Muscovy duck reovirus(MDRV)could lead to severe immune suppression and secondary infections to Muscovy,and MDRV nucleic acid is segmental,linear double-stranded RNA,which likely cause gene reassortment and serotypes mutation.MDRV cohabitation infection model was applied in this experiment,simulating natural infection methods to study the effects of HEP on intestinal mucosa of ducklings.Through the analysis on SIgA secretion,mucosal immune function related cytokines,somatostatin(SS),cAMP,NO and histamine(HIS),mucosal addressin cell adhesion molecule-l(MAdCAM-l),antioxi-dant capacity,and the relative expression of IL-2 and IL-6 mRNA in the intestinal mucosal tissues,and the content of MAdCAM-1 in the serum,and then clear the regulating effect of HEP on immune function of intestinal mucosa immunosuppre-ssion and its mechanism,provide scientific basis for the prevention and control of Muscovy reovirus disease.Through the establishment of simulation model which was similar with MDRV natural infection,200 of 1-day-old healthy young Muscovy were randomly divided into blank control group(BCG),Hericium erinaceus polysaccharide control group(HCG),cohabitation infected control group(CICG)and Hericium erinaceus polysacc-haride prevention group(HPG).6 samples in each experimental group were collected on the 1st,3rd,6th,10th,15th and 21st day after cohabitation infection,taking blood samples to collect blood serum,for determining the content of MAdCAM-1.Then sterilely took three samples-sections of duodenal tissues.One was used to extract total RNA,determining IL-2 mRNA and IL-6 mRNA expression levels.One was for determining the portion of cytokines and cAMP,NO,HIS,SS,MAdCAM-1 content.The last one used slide light to scrap intestinal mucosa for the determination of SIgA,GSH,MDA content and SOD activity.RIA results showed that the secretion level of intestinal mucosal SIgA of duck-lings with severe infection of MDRV,significantly decreased,compared with BCG.In intestinal tissue,the content of IFN-α,IFN-β,IFN-γ,IL-1β,IL-4,IL-5,IL-6,IL-8,IL-15,TNF-α,cAMP,SS decreased,while the content of IL-10,TGF-β,HIS,NO increased.The content of MAdCAM-1 in intestinal tissue decreased after an increase,which did not change significantly in serum.Compared with CICG,HEP could regula-te the secretion of above indexes in different extent,which may be related to inhibit-ing viral replication,maintaining a dynamic balance of intestinal mucosa local cellular immune function and humoralimmune function and reducing the occurrence of immu-ne suppression.The detection results of antioxidant indicators showed that the MDA content increased while SOD activity and GSH content significantly reduced in intes-tinal mucosal of CICG,compared with BCG.HEPS could increase SOD activity and GSH content,and decrease thecontent of MDA significantly.That exhibited the func-tion of improving antioxidase activity,removing free radicals and inhibiting lipid peroxidation.Real time-PCR results showed that the expression level of IL-2 mRNA significantly decreased,while the expression level of IL-6 mRNA increased,compared with BCG.HEP could alleviate the decrease of expression levels of IL-2 mRNA,and inhibit over-expression of IL-6 mRNA.These results indicated that MDRV could destroy intestinal mucosal immune system and antioxidant function,cause intestinal injury,which leaded to intestinal mucosa immune suppression.HEP took an important regulatory role on intestinal mucosal immune suppression of MDRV.It could improve the antioxidant capacity to mitigate the damage to intestinal barrier function of Muscovy.The result provided a theory basis for the clinical use of HEP to control MDRV infection.