Immunogenicity And Transcriptome Analysis Of Protoplast Fusion Strains SD₅ Of Salmonella And Escherichia Coli Of Ducks

Salmonellosis and colibacillosis of duck have become two important bacterial pathogens that threaten duck breeding industry.Due to the unreasonable use of antibiotics,antimicrobial resistance of bacteria was serious,drug treatment effect is not ideal,therefore effective vaccine to prevent bacterial infection is more and more attention.In this study,based on the original fused strains of Salmonella and E.coli of ducks,fusion strain SD₅ propolis inactivated vaccine and Salmonella S₇ and E.coli D₂ bicombinant inactivated propolis vaccine were prepared.After immunization of ducklings,the immune protection rate and serum were measured.Antibody titers,IL-4 and IFN-?levels,lymphocyte proliferation activity,and leukocyte phagocytosis activity were determined and the results were compared to evaluate the immune effects of SD₅ vaccine.Transcriptome sequencing was performed on SD₅,S₇ and D₂ to screen for differentially expressed genes and to elucidate SD₅ gene expression characteristics.The results of the study are as follows:The protection rates of SD₅ vaccine against S₇ and D₂ were 70%and 90%,respectively,and the protection rates of S₇-D₂ bicombinant vaccines were 80%and 70%,respectively;SD₅vaccine could induce both anti-S₇ and anti-D₂ antibody produced by the organism.The titer of potency was basically the same as that of the S₇-D₂ bicombinant vaccines.Antibodies could be detected after 3 days of immunization.The antibody level was significantly after 7 days different from that of the control group?P<0.01?.The serum titer of secondary immune was even more pronounced.The lymphocyte proliferation activity,IL-4,IFN-?levels and leukocyte phagocytosis activity were significantly higher than those in the control group?P<0.01?,and there was no significant difference compared with S₇-D₂ bicombinant vaccines.The transcriptomes of SD₅,S₇,and D₂ were sequenced.There were 1200 differentially expressed genes in SD₅ and S₇.There were 431 up-regulated genes,769 down-regulated genes,and 952 differentially expressed genes in SD₅ and D₂,of which 364 genes were up-regulated,and 588 genes are down-regulated.The GO enrichment analysis of differentially expressed genes revealed that 964 of SD₅ and S₇ differential genes were annotated to the GO database,involving 2070 GO functional categories,of which 20 GO function items were significantly enriched;There are 751 SD₅ and D₂ differentially expressed genes annotations to the GO database,involving a total of 2053 GO functional categories,and a significantly enriched GO function entry is the regulation of biological quality.The KEGG enrichment analysis of differentially expressed genes revealed that the differentially expressed genes of SD₅ and S₇ were distributed in 92 KEGG pathways.Significantly enriched pathways included flagellar assembly,ribosome,butanoate metabolism,propanoate metabolism,and carbon metabolism.The differentially expressed genes of SD₅ and D₂ are distributed in 93 KEGG pathways and no significant enrichment pathway was observed.Four differentially expressed genes were randomly selected for qRT-PCR validation and the results were similar to that of RNA-seq,demonstrating the reliability of the latter.