Research On The Kinatics Of Specific IgA Antibodys Against Swine Influenza Virus H3N2 Infection

Swine influenza A virus is a RNA virus infection of pigs,which has a decreased appetite,fever,cough,sneezing,sticky nose,dispirited spirit and so on.Swine influenza is characterized by rapid infection,short course of the disease,rapid spread,easy to epidemic and there are many subtypes and frequent variations,which the more common subtypes are H1N1 and H3N2 virus.Recent studies have shown that pig is mutual susceptible host of human,avian and swine influenza virus,and is regarded as the isolates of influenza virus gene rearrangement "mixer" and flu variant "incubator".Currently,people focus on immune molecules effects and vaccine research on influenza virus,which is usually to use small animals(e.g.,mouse,chicken,etc)for animal testing at home and abroad.But there is little care about the change trend of sIgA for swine influenza virus.Research on sIgA secretion against SIV infectioncould be benefit for monitoring of swine influenza infection and control of this disease.This study has been divided into two parts.The first part is to construct recombinant vectors for eight segments of SIV gene and to express their proteins.The second part is to detect the kinatics of sIgA antibody against the SIV challenge.In the first part,we successfully reconstructed recombinant plasmids of NA,M1,M2,PB1,PA,NP and NA gene of H3N2 by pET32a(+)and HA1 gene by pColdI,named as pET32a(+)-M1,pET32a(+)-NS1,pET32a(+)-PB1,pET32a(+)-NP,pColdI-HA1,pET32a(+)-NA,pET32a(+)-M2 and pET32a(+)-PA.However,only three fusion proteins of M1,NS1 and PB1,whose proteins’ molecular weight are ranked approximately 40kDa,42 kDa and 30 kDa,were expressed successfully.Good immunogenicity of three fusion proteins was confirmed by western blotting assay.In the second part,the SIV of H3N2 was propogated and used to challenge two breeds of pigs.Each pig were intranasally infected by SIV H3N2 with 2×107TCID50.Three indirect ELISA assays,developed with the fusion proteins M1,NS1 and PB1,were used to timely detect the secretion of specific slgA antibodies against SIV in the nasal cavity during 21 days post infection.The kinatics of three specific slgA antibodies were drawed.The results showed that the specific sIgA antibodies secretion of nasal M1 and NS1 and PB1 protein were significantly increased on 5 days of infection(dpi)and reached a peak on 14 dpi,however,decreased on 21 dpi.It showed that the kinatics of specific slgA antibodies secretion against three proteins didn’t have any significant difference(P>0.05).Only Bama pigs secreted the sIgA antibodies against anti-PB1 protein were higher(P<0.01)than those of the binary pig on day 14 dpi and 21 dpi.Moreover,sIgA antibodies displayed extremely significant difference(P<0.01)between infection group and control group.