| Porcine epidemic diarrhea virus(PEDV),the causative agent of porcine epidemic diarrhea(PED),has been prevailing in more than 20 provinces in China since 2010,causing severe water diarrhea,vomiting and dehydration accompanied with high mortality in 2-7 days old sucking piglets.The outbreak of PED has caused a significant impact and economic losses in swine industry in China.In this study,PEDV isolate strain CH/JX/01 and CV777 were inoculated into Vero cells,respectively.Viral antigen distribution and dynamic changes in Vero cells seperatly infected with these two strains of PEDV was detected by the immunofluorescence method.Then CH/JX/01 and CV777 strains adjuvanted with aluminum hydroxide were prepared,respectively.Afterwards,6 na?ve sows(free of anti-PEDV antibody in serum)were inoculated with CV777,CH/JX/01 strain and PBS,respectively.Three-day-old piglets(n=6)of each litter were randomly divided into two groups randomly from each sows inoculated with CV777 and CH/JX/01 strain and challenged with CV777 strain(group CC and WC)and CH/JX/01(group CW and WW)strain,respectively.Three-day-old piglets of the third litter injucted with PBS were randomly divided into three groups randomly and challenged with CV777 strain(group C),CH/JX/01(group W)strain and PBS(group NC).The challenged dose of each piglet was 105TCID50.Therefore,the clinical signs,gross leisions,histopathology leisions and the dynamic changes of blood cells and cytokines of TNF-??IL-1??IFN-??IL-4 ? IL-10 were examined.The results are as follows:The results of immunofluorescence staining: fluorescence was displayed in the cytoplasm of Vero cells infected with PEDVs.And the cytopathic effect(CPE)of Vero cells infected with CV777 appeared up at 36 h post-inoculation,but at 24 h post-inoculation for CH/JX/01.The morbidity and mortality of both group W and C were 100%,and the mortality of group CW and WW were 67% and 25%,respectively.Group CC and WC showed no obvious diarrhea symptoms.Among 4 treatment groups(group CC,CW,WC and WW),group CW showed the most severe diarrhea and the histological lesions of small intestine: significantly lower intestinal villus height(P<0.05)and villus height/crypt depth(V/C)value.The results of routine of blood tests: group W and C showed significantly higher(P<0.05)in granulocyte rate but decline in the rate of lymphocyte when compared to group NC,and the rate of lymphocyte of piglets in group W was significantly lower(P<0.05)in 48 h post-inoculation.The treatment groups showed a significantly lower(P>0.05)in granulocyte rate but increased in the rate of lymphocytes;and the rate of lymphocyte of piglets in group CC and WC were significantly higher(P<0.05)to group NC.The results of serum cytokine level detections: compared with group NC at 48 h post-inoculation,the TNF-? level had a significantly increase(P<0.05)in group C,W and the level of IFN-? in group W had a dramatic increase(P<0.01).The levels of IL-4 were elevated in group CW,WC and WW,and was significantly higher(P<0.05)in group WC in 48 h post-inoculation.The level of IL-4 was significantly higher(P<0.01)in group CW in 96 h post-inoculation than group NC.The group CW and CC showed significantly higher IL-10 level(P<0.01).The results of this study show that the pathogenicity,antigenicity and pathogensis of PEDV strain CH/JX/01 isolated in Jiangxi China exists distinct differences with CV777,and CV777 strain could not provide piglets against CH/JX/01 strain challenge.This study increases the knowledge on pathogensis which will benefit the prevention and control of PED. |
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