The Genetic Evolution Analysis And The Mechanism For Inhibiting ISGs Expression Of Feline And Canine Parvovirus Virus

Feline leukopenia disease that is caused by feline parvovirus(FPV)infection causes cat vomiting,hemorrhagic enteritis and severe reduction of white blood cells.Canine parvovirus disease that is caused by canine parvovirus type 2(CPV-2)causes dog vomiting and hemorrhagic enteritis.FPV is a prototype virus for the carnivorous parvovirus and can infect cats and raccoons,mink and foxes,but it can not infect dogs.CPV-2 was first identified in US in 1978 and quickly spread around the world only in two years.Along with the evolution,the original CPV-2 has replaced with three variants(CPV-2a/2b/2c)that are continuing to spread around the world.Besides,the CPV-2a/2b/2c variants obtained the feature of infection in cats again.Although it is a DNA virus,the genomic substitution rate of CPV-2 is similar to that of some RNA viruses,with approximately 10-4 substitutions/site/year.To trace the evolution process of CPV-2,this study conducted a etiology investigation of cats and dogs parvoviruses in Guangzhou and Shenzhen,two cities in Guangdong Province,and isolated 16 parvovirus from cats and 18 canine parvoviruses.It was suggested that both FPV and CPV-2 were important pathogens in feline panleukopenia disease,and CPV-2a/2b/2c variants were prevalent in dogs.After phylogentic tree analyses,FPV branch(including FPV,MEV,BFPV and RPV)and CPV-2 branch(including CPV-2 and CPV-2a/2b/2c)were defined as two phylogenetic tree branches,and this two branch did not form a reliable sub-branch.For systemic amino acid analyses,all of the VP2 gene sequences of CPV-2 and FPV(from 1978 to 2015)from Gen Bank were analyzed in this study.Then,several new ideas regarding CPV-2 evolution were presented.First,the VP2 amino acid 555 and 375 positions of CPV-2 were first ruled out as a universal mutation site in CPV-2 variants and amino acid 101 position of FPV feature I or T instead of only I in existing rule.Second,the recently confusing nomenclature of CPV-2 variants was substituted with a optional nomenclature that would serve future CPV-2 research.Third,After check the global distribution of variants,CPV-2a is the predominant variant in Asia and CPV-2c is the predominant variant in Europe and Latin America.Fourth,a series of CPV-2-like strains were identified and deduced to evolve from modified live vaccine strains.Finally,three single VP2 mutation(F267Y,Y324 I,and T440A)strains were caught concern.Furthermore,these three new VP2 mutation strains may be responsible for vaccine failure,and the strains with VP2 440 A may become the novel CPV sub-variant.In conclusion,a summary of all VP2 sequences provides a new perspective regarding CPV-2 evolution and the correlative biological studies needs to be further performed.As CPV-2a/2b/2c obtained the feature to infect cats again,both FPV and CPV-2 are the essential pathogens for feline leukopenia disease.But,the mechanism of FPV and CPV-2 infection of cats in not clear.Besides,many studies have shown that mi RNAs are involved in virus-host interaction.Nevertheless,mi RNA expression profiling of FPV(original virus)or CPV-2(new virus)in cats has not been reported.To investigate these profiles,this study is a first attempt to use mi RNA analysis to understand the molecular basis of FPV and CPV-2 infection in cats.The different mi RNA expression profiles of jejunums of cats infected with FPV and CPV-2 were obtained by comparing to the negative cat,and a subset of mi RNAs were validated by real-time q PCR.The results show that a variety of metabolism-related pathways,cytokine-and pathogen-host interaction-related pathways,and pathology-and cellar structure-related pathways,as well as others,were affected.Specifically,the JAK-STAT signaling pathway,which is critical for cytokines and growth factors,was enriched.This description of mi RNAs involved in the regulation of FPV and CPV-2 infection in vivo provides further insight into the mechanisms of viral infection and adaptation and may provide an alternative antiviral strategy for disease control and prevention.Interferon(IFN)is an important antiviral cytokine.After viral infection,pathogenassociated molecular patterns(PAMPs)activate interferon responses and secrete type I IFN.And then,via JAK-STAT signaling pathway,IFN stimulated to produce interferonstimulated genes(ISGs).We found FPV and CPV-2 inhibited the ISGs expression by q PCR.Then,the aim of this study was to explore the mechanism of FPV and CPV-2 inhibiting ISGs.First,the feline IFN-? promoter was successfully cloned and the double luciferase reporter system was established.Through this system,it was confirmed that FPV and CPV-2 activate the IFN-? promoter through the NF-? B and IRF3 transcription factor binding sites.Second,FPV and CPV-2 induced m RNA up-regulation of IFN-? and IFN-?.Third,FPV and CPV-2 induced up-regulation of fca-mir-5;It was demonstrated that fca-mir-5 targets the key protein TYK2 in the JAK-STAT signaling pathway;It was demonstrated that the overexpression of fca-mir-5 inhibited Sev stimulating cells to produce ISGs and the knock-down of fca-mir-5 induced FPV and CPV-2 to cause up-regulation of some ISGs.In conclusion,this study revealed that FPV and CPV-2 stimulated the up-regulation of fcamir-5,thereby blocking JAK-STAT signaling pathway and inhibiting ISGs protein expression.