Pinus Massoniana Pollen Polysaccharide Inhibits VvIBDV Infection By Interfering With Virus Adsorption In Vivo And Immunoregulation In Vitro

Infectious bursal disease(IBD)is an acute,highly contagious disease and caused by the infectious bursal disease virus(IBDV).Very virulent infectious bursal disease virus(vvIBDV)can cause high mortality and severe immunosuppression of chickens and bring huge economic losses to poultry industry.The current vaccination is still the main means of preventing the disease.However,due to the increasing prevalence of very virulent strains and variant strains,the phenomenon of immune failure occurs from time to time,causing irreversible damage to the growth of the bursa of Fabricius and may cause a renewed epidemic of IBD.Therefore,it is urgent to explore new drugs to prevent and control the prevalence and infection of IBD.With further research on plant polysaccharides,the anti-virus and regulation of immune function of Taishan pinus polysaccharide(TPPPS)has become a hot spot for researchers.The focus of this study was to investigate the inhibitory effects of pine pollen polysaccharides on vv IBDV in vitro infection and the immune opsonization of infected chickens.First,we investigated the ability of pine pollen polysaccharides to inhibit the activity and ability of vvIBDV in vitro.Second,we investigated the immune opsonization and antiviral effects of pine pollen polysaccharides on vvIBDV infection.This study is divided into the following two parts: 1.Activity analysis of anti-IBDV in vitro by TPPPSIn this study,DF-1 cells were used as host cells to investigate the mechanism of pine pollen polysaccharide in vitro against vv IBDV infection,and the virus inhibitor tibavirin as a control drug against virus was used to directly inactivate the virus from TPPPS.The mechanism of TPPPS anti-vvIBDV was explored in four aspects: retardation,inhibition of adsorption and replication.The results showed that TPPPS can effectively inhibit vv IBDV infection of DF-1 cells.It is speculated that the antiviral mechanism is that TPPPS pretreats DF-1 cells to bind the site of adsorption of virus particles on the cell surface and the virus and polysaccharide directly interact to inhibit the virus Adsorption of cells,or both effects coexist.It is suggested that TPPPS has potential for application and development in the prevention and treatment of vv IBDV infection.2.Study on the immune regulation and antiviral effect of TPPPS on vvIBDV chickens 2.1 Immune opacification of TPPPS against vvIBDV chickensIn this study,19-day-old SPF chickens were used as subjects to investigate the effect of TPPPS on the immunosuppression caused by vvIBDV.Studies have shown that TPPPS can significantly reduce the immunosuppression caused by vv IBDV infection and further enhance the body's immune system.After oral administration of TPPPS for 14 consecutive days,the body weight of the test chickens and the inhibition of the bursa of Fabricius were significantly improved,the amount of bursal poisoned was reduced,the degree of bursa of Fabricius was reduced,and the secretion of IBDV antibody was advanced and the secretion was increased.IL-2,IL-4 The secretion of cytokines increased,the number of CD4+ and CD8+ T lymphocytes increased,the conversion rate of T lymphocytes,and the level of ND antibodies increased.The above indicators in oral TPPPS group before virus inoculation were significantly higher than those in TPPPS treatment group and IBD.Vaccine group.The results of this study indicate that TPPPS has immunomodulatory effects on vv IBDV-induced chicken immunosuppression,and that oral TPPPS plays an important role in immune opsonization before virus inoculation.TPPPS can be used as an immunopotentiator to prevent and control early vvIBDV.Infection reduces IBDV-induced immune suppression.2.2 Antiviral effect of TPPPS on IBDV chickensIn this study,19-day-old SPF chickens were studied to investigate the role of TPPPS against SPF chickens infected with vvIBDV.Studies have shown that TPPPS has significant antiviral activity against vvIBDV.The antiviral effect of TPPPS on vv IBDV-infected chickens was analyzed by sequential oral administration of TPPPS to test chickens.The results showed that the weight of the experimental chickens restored to a healthy growth state,the inhibition of the bursa of the bursal was significantly improved,the amount of bursal bursal poisoning was reduced,and the degree of injury of the bursa of Fabricius was reduced.This indicates that TPPPS also has significant antiviral activity in vv IBDV infected chickens.The results of this study indicate that TPPPS interferes with virus adsorption and enters recipient cells through a direct interaction with IBDV virus particles during the period of blocking action and adsorption of cells,Feeding TPPPS early in multiple-day-olds infected with IBD in susceptible chickens can significantly improve the immunosuppression caused by IBD infection,increase the body's immune parameters and reduce the body's amount of virus,and has significant immunoregulatory and antiviral effects.