Construction And Immunogenicity Of Genetic Engineer Vaccines Against EU-type/NA-type PRRSV And PCV2

In a situation where European(EU) genotype of porcine reproductive andrespiratory syndrome virus (PRRSV) has recently emerged in China. The coexistenceof NA-(type2) and EU (type1)-PRRSV type strains in Chinese swine herds couldcause potential problems to PRRSV diagnostics and management，creates a suitableenvironment for PRRSV intra-type and inter-type recombination. Intra-typerecombination of NA and EU PRRSV has been described previously. Availablestrategies should be deployed to constrain the prevalence of PRRSV in Chinese swineherds, not only for type2PRRSV but also for type1PRRSV. Strategies such as theintroduction of an effective type1PRRSV vaccine should be considered, especiallywhen the prevalence of pathogenic type1PRRSV in Chinese herds has beendetermined. In addition, PRRSV infection has been shown to enhance the severity ofclinical PCVAD under field and experimental conditions. Since both PCV2andPRRSV infect the monocytic cell lineage, PRRSV has been suggested to be associatedwith enhanced PCV2replication resulting in increased amounts of PCV2DNApresent in the sera of PCV2-PRRSV co-infected pigs. Moreover, PRRSV was foundto increase Interleukin (IL)-10expression which in turn suppresses T cell response,this may allow PCV2to circumvent the host immune response.In fact, co-infection ofPCV2and PRRSV in pigs is frequently observed in swine herds under fieldconditions. At present, vaccines are not able to protect completely against PRRSV andPCV2infection and have inherent drawbacks. Thus other strategies have been used todevelop genetically engineered vaccines, which including DNA vaccine and manylive vector engineering vaccines.Based on ORF3/ORF5gene of American-type CC strain, ORF3/ORF5ofLV strains which is European-type representative strains and ORF2gene of PCV2,Our research constructed Recombinant DNA vaccine of European-type PRRSV(pVAX1-EU-ORF3-ORF5)，Divalent recombinant DNA vaccine of European-type and American-type PRRSV (pVAX1-NA-ORF3-ORF5-EU-ORF3-ORF5), two-combined recombinant DNA vaccine of European-type PRRSV and PCV2(pVAX1-ORF2-EU-ORF3-ORF5). With Tiantan strain of vaccinia virus (E3L-) as atransformation of an object, we constructed Tiantan attenuated vaccine of TKgene deletion strains of vaccinia virus using the theory and technology ofhomologous recombination, including recombinant poxvirus virus of European-type PRRSV (rVV-EU-ORF3-ORF5), Divalent recombinant poxvirus virus ofEuropean-type and American-type PRRSV (rVV-NA-ORF3-ORF5-EU-ORF3-ORF5) and two-combined recombinant poxvirus virus of European-type PRRSVand PCV2(rVV-ORF2-EU-ORF3-ORF5).After the screening and identification with selectable marker, we analyze theimmunological properties of the recombinant virus through experimental animalstudies in mice and pigs, testing the response ability of specific humoral and cellularimmune response induced by these vaccines. Reference to the experimental data, thisresearch screened therapeutic vaccines with good prospect and establish effectiveimmunization strategies. The results shows that DNA vaccines and recombinantpoxvirus vaccine has good immunogenicity and reactogenicity, which can inducespecific humoral immune response in mice and pigs and provide better immuneprotection after challenged with PRRSV (LV strain and NM12strain) and PCV2.In addition， prime-boost vaccine regimens can improve humoral-andcell-mediated immune responses to PRRSV, exceptionally inoculation of pigs withrVV-EU-ORF3-ORF5priming followed by pVAX1-EU-ORF3-ORF5boosting couldprovide a better resistance to PRRSV infection and inhibited viral replication in vivo.Moreover, careful selection of adjuvants or delivery systems can enhance prime-boostregimens elicited immune responses, new vaccine adjuvants can potentiateimmunogenicity and protective efficacy of PRRSV vaccine. Quil A vaccine adjuvanthave a good prospect of immune responses and protective efficiency of in PRRSVvaccine. DNA were formulated together with chitosan, and delivered in the form ofchitosan-DNA nanoparticles may be is a wonderful choice. Consequently, it istherefore essential that future PRRSV and PCV2vaccines must be more potent, safe,efficacious, and provides more efficient protection against PRRSV.