Development Of Rotavirus Induced Diarrhea Model And Efficacy Of Inactivated Rotavirus ZTR-68 Vaccine In Balb/c Neonatal Mice

Rotavirus(RV)is one of the major causes of diarrhea in infants under the age of five years.In the world,The number of infections is nearly 110 million per year,and the number of deaths is about 500,000.To date,there are still no effective drugs for the treatment of rotavirus infection.Vaccination is an effective means of preventing rotavirus infection.Exploring the construction of rotavirus animal models not only helps to evaluate the protection of rotavirus vaccines,but also helps to study the mechanism of rotavirus-induced diarrhea.In order to study the pathogenesis of Rotavirus(RV),Balb/c neonatal mices were developed for diarrhea model using simian rotavirus strain SA11and Human rotavirus strain ZTR-68.These data provide theoretical and experimental basis for vaccine protection evaluation.The 4-day-old Balb/c mices were intragastrically administrated with RV SA11 and ZTR-68 strain in different doses.The diarrhea status of these mice were observed at different time points.These mices were euthanized and dissected.Heart,liver,spleen,lung,small intestine and kidney and other tissues of euthanized mices were collected and detected by immunofluorescence for Rotavirus distribution.The collected tissues were fixed in formalin and used in HE staining and IHC staining for the detection of pathological changes of jejunum and the apoptosis of the cells.Obvious diarrhea symptoms were observed at 24h post inocμlation with Rotavirus strain SA11and ZTR-68.Pathological anatomy results showed that the intestines of these model mices are congested and flattened after 72h infection.Compared to the controls,the resμlts of intestine HE staining showed that the pathological changes in model mice were obvious,including vacuolar degeneration,edema and congestion of intestinal wall,integrity destruction of enteric epithelium and cell apoptosis,after intragastrically administered with SA11 strain and ZTR-68 strain.Rotavirus distribution in intestine and kidneys was also detected by immunofluorescence assay.In this study,the Rotavirus diarrhea models of Balb/c neonatal mice were developed successfμlly with RV SA11 strain and ZTR-68 strain.In addition to small intestine distribution,we found that Rotavirus distribution coμld also be detected in kidney of Balb/c neonatal mice after infection.In this study,we established an RV-induced diarrhea neonatal mouse model and analyzed the in vivo efficacy of an IRV derived from the wildtype human RV strain,ZTR-68.Adμlt Balb/c female mice were immunized twice(two week interval)with IRV at different dosages and mated with males.Seven days after new pups were born,the maternal mice and neonatal mice were analyzed for RV-specific antibodies.The results demonstrated that both the immunized maternal mice and the corresponding neonatal mice carried anti-RV IgG antibodies with equivalent antibody levels.Furthermore,we assayed protection against viral attack against 4-day old neonatal mice using monkey RV SA11 strain(G3[P2])and human RV ZTR-68 strain(G1[P8]).When compared to the control,the immunized neonatal mice exhibited delayed diarrhea occurrence and reduced diarrhea severity.Moreover,immunofluorescence analysis indicated that immunized neonatal mice carried significantly less or no RV antigens in the intestine and kidney relative to control mice.Furthermore,H&E staining of intestine tissue sections showed that the intestinal villi of the control neonatal mice were swollen,damaged at the distal end,and with severe cellμlar vacuolation;while the intestinal villi of the immunized neonatal mice only exhibited a low level of swelling without notable damage or massive cellμlar vacuolation.Our resμlts also showed that the IRV derived from RV strain ZTR-68 were passed to the neonatal mice.In addition,the IRV in the neonatal mice protected the host from not only the parental RV strain ZTR-68(G1[P8]),but also other strains such as SA11(G3[P2]).