Evaluation Of Immune Effect Of DNA And Subunit Vaccine Of Four African Swine Fever Virus Proteins

African swine fever(ASF)is a highly contagious,hemorrhagic and viral infectious disease caused by African swine fever virus(ASFV).ASFV can cause high morbidity and mortality in domestic pigs and wild boar.ASFV emerged China in August 2018,with the development of the epidemic,it has spread across regions in China.There is no available vaccine for ASFV,and current control methods involve quarantined and culling of animals in affected areas and regions.ASFV poses a significant threat to the swine industry worldwide,and the need for an ASFV vaccine is of high priority.This study purpose to use DNA vaccines(based on p CAGGS plasmid)and subunit vaccines(based on baculovirus expression system)to immunize pigs,and evaluate the immunogenicity of four candidate proteins by different immune procedures.p30(CP204L),p54(E183L),p72(B646L)and B602 L proteins play an important role in the replication,assembly,invasion and internalization of ASFV.In this study,we recombinant plasmids-p CAGGS and baculoviruses expressing the selected ASFV antigens.The expression of the protein was confirmed by indirect immuneinfluscent assay(IFA)test and Western Blot test.The results showed that both the plasmid and recombinant baculovirus could effectively express the target protein.The 4-week-old piglets were inoculated with ASFV p30,p54,p72 and B602 L gene DNA vaccine and baculovirus expression protein subunit vaccine.The piglets were inoculated three times with an interval of 14 days.The treated animals were divided into three different groups.The first group was first inoculated with DNA vaccine(each plasmid was immunized with 1mg),and the second and third inoculated with subunit vaccines(500 μg for each protein)were boosted,referred to as "primary-boosted group";The second group was inoculated with DNA vaccine(each plasmid was immunized with 1mg)and subunit vaccine(500 μg for each protein),which was referred to as "double enhancement group",and the third group was inoculated with PBS.During the immunization period,blood for the preparation of serum was collected once two weeks from all the animals.The serum samples were tested to detect ASFV-specific antibodies and neutralization antibody.The cellular responses induced were measured by IFNγ-ELISpot test.The results showed that four kinds of DNA plasmids and three expressed proteins could induce specific antibodies in piglets,and the "double enhanced group" could induce higher antibodys response at the 4th and 6th week,but even if there was a high level of antibody,neutralizing antibody could not be detected in vitro.The results of ELISpot experiment showed that the Peripheral blood mononuclear cell(PBMC)of "double enhanced group" and "primary-boosted group" were stimulated by synthetic peptides designed for p30,p54,p72 and B602 L genes.In summary,the co-immunization of DNA and subunit vaccines can induce the production of ASFV specific antibody and improve the level of specific cellular responses.Before the effective ASFV vaccines were invented,DNA vaccine and subunit vaccine can tested the ASFV candidate genes functions,including the immunogenicity of antibodys and cellular responses,which will provide reference for the further studies of immunogenicity of unknown functional genes of ASFV.