Expression And Immunogenicity Analysis Of Four Apx Toxins Of Actinobacillus Pleuropneumoniae

Procine contagious pleuropneumoniae(PCP)is an acute respiratory infection caused by Actinobacillus pleuropneumoniae(APP),which has caused huge economic losses to the pig industry in China.Actinobacillus pleuropneumoniae RTX Toxin(Apx toxin),produced by APP,is a hemolytic exotoxin,which is not only an important virulence factor,but also an important protective antigen of APP.After the bioinformatics analysis of structural genes of four Apx toxins,this research has cloned their genes such as Apx-N terminal,Apx-C terminal,Apx-NC(N-terminal+C-terminal)and Apx-full length according to their fuctional loci.Constructed 13 recombinant plasmids that ApxIV-N terminal was only constructed in ApxIV toxin and expressed 12 recombinant proteins successfully in the end,and all of them were inclusion body.Mixed recombinant protein with aluminium gel adjuvant was prepared to immunize mice with subunit vaccine of genetic engineering.Protection experiments on immunized mice with type 1 and type 15 APP,respectively.The result showed that ApxI-C and ApxIII-C proteins had better protective effects on type 1 and 15 APP,and the protective rates of ApxI-C were 83.3% and 66.7% respectively,the protective rates of ApxIII-C were all 66.7%.ApxI-NC,ApxI-full length and ApxII-N only had protective effects on type 1 APP,with protective rates of 100%,83.3% and 33.3% respectively.The recombinant proteins of ApxII,ApxIII and ApxIV only had protective effects on15 APP(except ApxII-N),andthe protection rates of ApxII-NC,ApxII-full length,Apx III-NC and ApxIII-full length were all 83.3%,ApxIII-C,ApxIV-N were all 66.7%,ApxIII-N was 50%.This research has showed:(1)Apx toxin is one of the important protective antigen of APP;(2)ApxI-C and ApxIII-C have good protection for both type1 and type15 APP,which maybe the potential cross-protective antigen of APP for further development and exploration.