The Antivirus Activity Of Polysaccharide From Broussonetia Papyrifera Against Porcine Reproductive And Respiratory Syndrome Virus In Vitro

Porcine reproductive and respiratory syndrome(PRRS)is a highly contagious infectious disease caused by the Porcine reproductive and respiratory syndrome virus(PRRSV),characterized by reproductive disorders in sows,high fever and difficulty breathing in piglets.Due to the high variability of PRRSV,the immune effect of PRRSV vaccine is poor.At present,there is no specific medicine for PRRS,and PRRSV produces immunosuppression,so the prevention and treatment effect of PRRS is poor.Broussonetia papyrifera,as a traditional Chinese herbal medicine,contains many biologically active substances.In study,polysaccharide extracted and purified from the bark of Broussonetia papyrifera was used to investigate the effect on Marc-145 cells infected by PRRSV and related mechanisms,which provides theoretical basis for the prevention and treatment of PRRS,the development and utilization of Broussonetia papyrifera resources.1.Extraction,purification,content determination and monosaccharide composition analysis of Broussonetia papyrifera polysaccharide:Broussonetia papyrifera bark was extracted and purified to obtain Broussonetia papyrifera polysaccharide,which total polysaccharide content can reach 80.6%,including55.2% monosaccharide,25.4% uronic acid.Broussonetia papyrifera contained 9monosaccharide components,among which the content of glucose,rhamnose,arabinose,and galactose was relatively high,and the relative content was 39.6,17.8,15.1,and 13.8%respectively.2.Anti-PRRSV activity of Broussonetia papyrifera polysaccharide in vitro:(1)Broussonetia papyrifera had no significant cytotoxicity to Marc-145 cells in the concentration of 0.625-10 mg/m L.(2)Broussonetia papyrifera polysaccharide can be transported into the cell to promote the proliferation of Marc-145 cells.(3)Broussonetia papyrifera polysaccharide significantly inhibit cytopathic changes caused by PRRSV infection by inhibiting the entry of the virus and reducing the pathogenicity of PRRSV.3.The effect of Broussonetia papyrifera polysaccharide on PRRSV receptor expression level:(1)When PRRSV infected Marc-145 cells fort 3,6 h,the expression level of vimentin was increased.When PRRSV infected Marc-145 cells for 12,24 h,the expression level of vimentin was down-regulated.At the early stage of PRRSV infection,vimentin promoted the invasion and proliferation of the virus and cell pathology led to a decrease in vimentin expression level at the late stage of PRRSV infection.(2)When PRRSV infected Marc-145 cells for 3,6,and 12 h,the addition of Broussonetia papyrifera polysaccharide down-regulated the expression of vimentin.When PRRSV was infected with Marc-145 cells for 24 h,the addition of Broussonetia papyrifera polysaccharide could maintain the expression of vimentin to a certain extent level.At the early stage of PRRSV infection,Broussonetia papyrifera polysaccharide inhibit virus entry and proliferation by down-regulating the expression level of vimentin and the expression of vimentin was maintained at a high level by inhibiting host cell pathology at the late stage of infection.