title: Compound DNA vaccine encoding SAG1/ SAG3 with A2/B subunit of cholera toxin as a genetic adjuvant protects BALB/c mice against Toxoplasma gondii.
abstract: BACKGROUND
  Intracellular parasites, such as T. gondii, present a plurality of antigens because of the complexity of its life cycle. Compound DNA vaccines bring a new approach and hope for the treatment of toxoplasmosis. In this study, a DNA vaccine encoding two major surface antigens SAG1, SAG3 from T. gondii, with A2/B subunit of cholera toxin as a genetic adjuvant was constructed.
  
  
  METHODS
  BALB/c mice were immunized intramuscularly with PBS, pcDNA3.1, pSAG1, pSAG1/SAG3 and pSAG1/SAG3-CTXA2/B three times separately. Immunized mice were tested for IgG antibody and IFN-γ and IL-4 production by ELISA. The proliferation of T cells was measured by DNA synthesis assay and the lymphocyte subsets of spleen cells by flow cytometry. All the immunized mice were challenged with 103 highly virulent RH tachyzoites of Toxoplasma gondii intraperitoneally and the survival times were recorded.
  
  
  RESULTS
  An enhanced production of IgG antibodies, antigen-specific lymphocyte proliferation and IFN-γ production from splenic cells were induced in mice immunized with pSAG1/SAG3 compared to mice immunized with pSAG1 (P<0.05). Introduction of CTXA2/B further enhanced the Th1 cell-mediated immunity with higher levels of IFN-γ, lymphocyte proliferation activity and percentage of CD8+ T-cells. When challenged with lethal doses of T. gondii (1 × 103), all control mice (PBS and empty plasmid group) died within 6 days. Mice immunized with pSAG1 died within 8 days. While 20% and 40% survival rate were achieved from mice immunized with pSAG1/SAG3 and pSAG1/SAG3-CTXA2/B.
  
  
  CONCLUSIONS
  This study indicates the compound DNA vaccine encoding T. gondii antigens SAG1, SAG3 with CTXA2/B gene was a promising DNA vaccine candidate against toxoplasmosis, which could effectively enhance the humoral and cellular immune response and prolong survival time in vaccinated mice.
authors.affiliation: Department of human parasitology, Shandong University School of Medicine, No44 wenhuaxi Road, Jinan, Shandong, 250012, PR China. conghua@sdu.edu.cn
authors.forename: Hua
authors.initials: H
authors.lastname: Cong
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Qing
authors.initials: Q
authors.lastname: Xin
authors.forename: Zhiyu
authors.initials: Z
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Qunli
authors.initials: Q
authors.lastname: Zhao
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Zhou
authors.forename: Shenyi
authors.initials: S
authors.lastname: He
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage* / Q000235:genetics; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D049109:Cell Proliferation; D002772:Cholera Toxin / Q000008:administration & dosage* / Q000235:genetics; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007273:Injections, Intramuscular; D007371:Interferon-gamma / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D016052:Protozoan Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D016019:Survival Analysis; D013601:T-Lymphocytes / Q000276:immunology; D014124:Toxoplasmosis, Animal / Q000276:immunology / Q000517:prevention & control*; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D007074:Immunoglobulin G; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; D016052:Protozoan Vaccines; C047168:SAG1 antigen, Toxoplasma; C087692:SAG3 protein, Toxoplasma gondii; D019444:Vaccines, DNA; D015847:Interleukin-4; D007371:Interferon-gamma; D002772:Cholera Toxin