Molecular Epidemiological Investigation Of PEDV S1 Gene In Guangxi From 2017 To 2018 And Establishment Of A Detect Method Of Pedv-specific Antibody Siga

Porcine epidemic diarrhea(PED)is an infectious disease which lead to a high mortality rate for newborn piglets caused by Porcine epidemic diarrhea virus(PEDV).PEDV G2 strain caused a huge losses to China’s pig industry in2010.Until 2017,the G2 vaccine was successfuLly developed and widely used.But the infection of PEDV was still seriously in Guangxi.In this background,the purpose of this study was to investigate and understand the epidemic situation of PEDV more clearly and mucosal immunity of sows after vaccine immunization in Guangxi.1.MolecuLar epidemiological investigation of S1 gene of PEDV epidemic strains in Guangxi.This study successfuLly established an RT-PCR method that couLd quickly identify and diagnose PEDV G1 or G2 infection.Use this method to detect 92 clinicals samples which collected during 2017～2018.And positive rate was59.78%.Among the strains that isolated in these positive samples,the G1 strain accounted for 3.6% while the G2 strain was 96.36%.47 PEDV S1 partial genes from these positive samples were cloned and analyzed.It was found that the G2 and G2-a-a strains were the mainly epidemical strains.Potential recombination events were existed in S1 gene of some PEDV strains in Guangxi,and nine positive selection sites(AAs 2,27,55,201,237,314,315,347,361)in the signal peptide,NTD and CTD areas were identified.Compared with the S1 gene in virus isolation from the same pig farms which immunized by G2 vaccine or not,we found there were unique amino acid changes(T5P,S219 N,V273L,I323V)in the main functional region.Among these changes,the fifth(T5P)amino acid might lead to the changes of the secondary structure of protein in main functional region of signal peptide.2.Establishment of ELISA for detecting the specific antibodies SIgA in sow colostrum.The unique component in SIgA(SC protein)was used as the research object in This study.Rabbit anti-pig SC polyclonal antibodies were prepared by gene cloning,prokaryotic expression and preparation of polyclonal antibodies.Use the PEDV virus to coating the ELISA plate and then an ELISA method to detect PEDV-specific SIgA antibodies in sow colostrum was developed.The use of immune and unimmunized colostrum for preliminary application,It was found that this method couLd identify PEDV specific SIgA antibody in the colostrum of sow.The findings of the S gene in this study couLd provide references for the research about replication,viral viruLence,immune evasion and prevention of PEDV.At the same time,an ELISA method for detecting PEDV-specific SIgA antibodies in sow colostrum was successfuLly established.This method wouLd provide a scientific basis for further exploring the dynamics of PEDV-specific SIgA antibodies in sow milk,evaluation of PEDV mucosal immune effects,optimization of immune procedures and prevention of PEDV in suckling piglets.