Effect Of Porcine Sapelovirus Infection On Samll Intestinal Barrier In Piglets

In recent years,with the rapid development of pig industry,it is also facing the threat of a variety of diseases,and diarrhea is one of the biggest threats.Frequent diarrhea have caused huge economic losses to the pig industry.As an enterovirus with high detection rate,Porcine Sapelovirus,can cause diarrhea,pneumonia,encephalomyelitis,and other diseases after infection,which will seriously affect the healthy growth of piglets.Moreover,the subclinical infection of PSV only causes slight tissue damage or even no damage,which is easy to be ignored clinically,resulting in the spread of PSV infection,thus increasing the difficulty of prevention and control.At present,PSV generally exists in domestic large-scale pig farms,and has been detected in pig farms in South China,East China,North China,and southwest China,which poses a threat to the sustainable development of pig industry.So far,the research on PSV is mainly in epidemiology,but the pathogenic mechanism of host diarrhea caused by PSV infection is still unclear.Therefore,in order to further study the pathogenic mechanism of PSV,this paper studied the tissue localization of PSV in pig small intestine and the effect of virus on the morphology of small intestinal mucosa,and further analyzed the effect of PSV infection on the tight junction between intestinal mucosal epithelial cells and the repair after epithelial cell injury in piglets.The main research contents and results are as follows:1.Localization of PSV in intestinal tissue after infectionThe infection model was established by infecting piglets with PSV strain.The intestinal tissues of piglets were made into paraffin sections,and the distribution of PSV in the intestinal tissues of piglets was detected by immunohistochemistry(IHC).IHC results showed that PSV positive signals mainly existed in intestinal villous epithelial cells and lymphocytes.2.The effect of PSV infection on tight junction between small intestinal epithelial cells.Using the intestinal tissues of pigs artificially infected with PSV as materials,the intestinal tight junction related proteins were detected by q PCR,Western blot and IHC.The results showed that,the m RNA and protein expression levels of Claudin-3,Occludin and ZO-1 in the ileum decreased after PSV infected.The IHC results of Claudin-3 showed that Claudin-3 decreased or disappeared between the epithelial cells at the top of villi after PSV infection.The results showed that PSV infection could down regulate the expression of tight junction associated protein,destroy tight junction,damage the integrity of intestinal barrier,and cause intestinal injury.3.Effect of PSV infection on repair of small intestinal epithelium after injuryFactors involved in the proliferation and differentiation of intestinal stem cells were determined by q PCR,Western blot,and so on.The results showed that,in the Wnt/β-catenin signaling pathway,the m RNA expression levels ofβ-catenin were increased.The m RNA and protein expression levels of LEF1 were increased.The results of IHC for intestinal stem cells showed that LGR5~+cells were increased after PSV infection.In the Notch signaling pathway,the m RNA and protein expression levels of Notch1,Notch3,Hes1decreased,ATOH1 increased,and mucin MUC2 increased.The goblet cells in the small intestine were localized by PAS staining,and then we analyzed the positive of PAS staining,The results showed that,compared with the control group,the goblet cells in the ileum were significantly increased after PSV infection.The above results indicated that PSV infection could promote intestinal stem cell proliferation and differentiate into secretory type goblet cells with enhanced secretion.4.Effect of PSV infection on intestinal immunity of pigletsThe intestinal tissues of pigs artificially infected with PSV were made into paraffin sections.IHC was used to locate the intestinal related immune cells.And then we analyzed the positive rate of IHC staining.The results showed that compared with the control group,after PSV infection,the number of CD3~+T lymphocytes was decreased in the jejunum and ileum of piglets,and the number of CD4~+T lymphocytes in the duodenum and ileum was significantly decreased,in contrast to the number of CD8~+T lymphocytes in the jejunum and ileum.The results showed that PSV infection affected the mucosal immune function of the small intestine,which suggested its correlation with diarrhea caused by clinical infection with PSV.Based on the above results,PSV was colonized in the villous epithelial cells and la mina propria lymphocytes of the small intestine after infection,which destroyed the tight junction between the epithelium,resulting in the disorder of epithelial selective permeability and the abscission of epithelial cells;PSV infection can promote intestinal stem cells to proliferate and differentiate into secretory cells,and promote mucin secretion,leading to absorption disorder;PSV infection leads to the disorder of epithelial selective permeability,induces and enhances humoral immunity,and leads to the inflammatory and pathological damage of intestinal tract in piglets;The above results together cause the destruction of the integrity of intestinal barrier in piglets,and then cause piglet diarrhea.