Hsp 70 From Haemophilus Parasuis Increases The Immune Response Of Classical Swine Fever Virus E0 And E2 Subunit Vaccine In Mice And Rabbits

Classical swine fever virus(CSFV)is the causative pathogen of classical swine fever(CSF),a highly contagious disease of swine.It can cause huge economic losses to the pig industry worldwide and was classified as Class A animal disease by the World Organisation for Animal Health(OIE).CSFV,encompassing a single-stranded RNA genome,is an enveloped virus with three kinds of envelope glycoproteins:EO(also known as Erns),El and E2.E0 and E2 are two main protective antigens inducing neutralizing antibody and also play an essential role in CSFV entry into the sensitive cells.Chimeric antigens of EO and E2 can significantly improve the sensitivity of serological diagnosis for CSFV by successfully detecting the infection 7 days in advance.Though traditional vaccines for CSFV,such as the widely-used hog cholera lapinized virus vaccine,have good immunogenicity,broad immune spectrum,high security and effect,good genetic stability and etc.,antigenic variation has occurred in the wild and vaccine strains as the latter has been intensively used for a long time,which results in chronic,latent infection and other atypical epidemic forms.With strong virulence return of live attenuated vaccines,they may also cause death of fetal pigs,weakness,congenital infection and immune tolerance of piglets via placenta.Therefore,it is necessary and also feasible to develop new vaccines that overcome the shortcomings of traditional vaccines of CSFV.Heat shock proteins known as stress proteins or protein chaperones,are a family of most highly conserved and abundant proteins among prokaryotic and eukaryotic cells.Hsps belonging to the Hsp90,Hsp70,and Hsp60 families are among the best characterized.Hsp70 has also been implicated in antigen presentation,and it is possible that this function contributes to its adjuvant-free carrier effect.To analyze the influence of Hsp70 on EO and E2 vaccine potency,Hsp70 protein was expressed in E.coli and then was as an adjuvant of EO and E2 subunit vaccine.We constructed the recombinant plasmids pColdI-Hsp70,pColdI-E0 and pColdI-E0-Hsp70,and expressed three kinds of prokaryotic expression proteins to immunized Balb/c mice.At the same time,mice and rabbits were immunized with recombinant glycosylated E2 with or without Hsp70.The humoral and cellular responses elicited against E0 and E2 were measured using ELISA kits,fluorescence flow cytometry,and cytotoxicity assays.The results showed that Hsp70 significantly enhanced EO and E2 vaccine potency by induction of a high and long-lasting specific immune response,as demonstrated by an increased IgG isotype,IFN-γ production,and Th/Ts cell differentiation in mice.Moreover,Hsp70 could enhance the antibodies in rabbits and provide protection against CSFV.Overall,our finding laid the theoretical foundation of CSFV subunit vaccine.