title: Construction and immunogenicity of a DNA vaccine coexpressing GP3 and GP5 of genotype-I porcine reproductive and respiratory syndrome virus.
abstract: BACKGROUND
  The European (EU) genotype of porcine reproductive and respiratory syndrome virus (Genotype-I PRRSV) has recently emerged in China. The coexistence of Genotype-I and -II PRRSV strains could cause seriously affect PRRSV diagnosis and management. Current vaccines are not able to protect against PRRSV infection completely and have inherent drawbacks. Thus, genetically engineered vaccines, including DNA vaccine and live vector engineered vaccines, have been developed. This study aimed to determine the enhanced immune responses of mice inoculated with a DNA vaccine coexpressing GP3 and GP5 of a Genotype-I PRRSV.
  
  
  RESULTS
  To evaluate the immunogenicity of GP3 and GP5 proteins from European-type PRRSV, three DNA vaccines, pVAX1-EU-ORF3-ORF5, pVAX1-EU-ORF3 and pVAX1-EU-ORF5, were constructed, which were based on a Genotype-I LV strain (GenBank ID: M96262). BALB/c mice were immunized with the DNA vaccines; delivered in the form of chitosan-DNA nanoparticles. To increase the efficiency of the vaccine, Quil A (Quillaja) was used as an adjuvant. GP3 and GP5-specific antibodies, neutralizing antibodies and cytokines (IL-2, IL-4, IL-10 and IFN gamma) from the immunized mice sera, and other immune parameters, were examined, including T-cell proliferation responses and subgroups of spleen T-lymphocytes. The results showed that ORF3 and ORF5 proteins of Genotype-I PRRSV induced GP3 and GP5-specific antibodies that could neutralize the virus. The levels of Cytokines IL-2, IL-4, IL-10, and IFN-γ of the experimental groups were significantly higher than those of control groups after booster vaccination (P < 0.05). The production of CD3+CD4+ and CD3+CD8+ T lymphocyte was also induced. T lymphocyte proliferation assays showed that the PRRSV LV strain virus could stimulate the proliferation of T lymphocytes in mice in the experimental group.
  
  
  CONCLUSIONS
  Using Quil A as adjuvant, Genotype-I PRRSV GP3 and GP5 proteins produced good immunogenicity and reactivity. More importantly, better PRRSV-specific neutralizing antibody titers and cell-mediated immune responses were observed in mice immunized with the DNA vaccine co-expressing GP3 and GP5 proteins than in mice immunized with a DNA vaccine expressing either protein singly. The results of this study demonstrated that co-immunization with GP3 and GP5 produced a better immune response in mice.
authors.forename: Jing-Qiang
authors.initials: JQ
authors.lastname: Ren
authors.forename: Wen-Chao
authors.initials: WC
authors.lastname: Sun
authors.affiliation: Institute of Military Veterinary, Key Laboratory of Jilin Province for Zoonosis Prevention and Control, Academy of Military Medical Sciences, Changchun 130122, China. nakata0007@sina.com.
authors.forename: Hui-Jun
authors.initials: HJ
authors.lastname: Lu
authors.forename: Shu-Bo
authors.initials: SB
authors.lastname: Wen
authors.forename: Jie
authors.initials: J
authors.lastname: Jing
authors.forename: Fu-Long
authors.initials: FL
authors.lastname: Yan
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.forename: Cun-Xia
authors.initials: CX
authors.lastname: Liu
authors.forename: Peng-Peng
authors.initials: PP
authors.lastname: Xiao
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
authors.forename: Shou-Wen
authors.initials: SW
authors.lastname: Du
authors.forename: Rui
authors.initials: R
authors.lastname: Du
authors.forename: Ning-Yi
authors.initials: NY
authors.lastname: Jin
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood*; D049109:Cell Proliferation; D048271:Chitosan; D005838:Genotype; D007371:Interferon-gamma / Q000097:blood; D007376:Interleukin-2 / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D053758:Nanoparticles; D019316:Porcine respiratory and reproductive syndrome virus / Q000276:immunology / Q000378:metabolism*; D062605:Quillaja Saponins; D013601:T-Lymphocytes / Q000502:physiology; D019444:Vaccines, DNA / Q000276:immunology; D014764:Viral Proteins / Q000276:immunology* / Q000378:metabolism; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D007376:Interleukin-2; D062605:Quillaja Saponins; D019444:Vaccines, DNA; D014764:Viral Proteins; D014765:Viral Vaccines; C046386:Quil A; D007371:Interferon-gamma; D048271:Chitosan