title: Evaluation of protective immune responses induced by DNA vaccines encoding Toxoplasma gondii surface antigen 1 (SAG1) and 14-3-3 protein in BALB/c mice.
abstract: BACKGROUND
  Toxoplasmosis, caused by an obligate intracellular protozoan parasite Toxoplasma gondii, has been a serious clinical and veterinary problem. Effective DNA vaccines against T. gondii can prevent and control the spread of toxoplasmosis, which is important for both human health and the farming industry. The T. gondii 14-3-3 protein has been proved to be antigenic and immunogenic and was a potential vaccine candidate against toxoplasmosis. In this study, we evaluated the immune responses induced by recombinant plasmids encoding T. gondii surface antigen 1 (SAG1) and 14-3-3 protein by immunizing BALB/c mice intramuscularly.
  
  
  METHODS
  In the present study, BALB/c mice were randomly divided into five groups, including three experimental groups (pSAG1, p14-3-3 and pSAG1/14-3-3) and two control groups (PBS and pBudCE4.1), and were immunized intramuscularly three times. The levels of IgG antibodies and cytokine production in mouse sera were determined by enzyme-linked immunosorbent assays (ELISA). Two weeks after the last immunization, all mice were challenged intraperitoneally (i.p.) with 1×10(4) tachyzoites of T. gondii and the survival time of mice was observed and recorded every day.
  
  
  RESULTS
  Mice vaccinated with pSAG1, p14-3-3 or pSAG1/14-3-3 developed high levels of IgG2a and gamma interferon (IFN-γ) and low levels of interleukin-4 (IL-4) and interleukin-10 (IL-10) compared to control groups (PBS or pBudCE4.1), which suggested a modulated Th1 type immune response (P<0.05). After intraperitoneal challenge with 1×10(4) tachyzoites of T. gondii (RH strain), the survival time of mice in experimental groups was longer than control groups (P<0.05). Mouse immunized with pSAG1/14-3-3 induced a higher level of IgG antibody response and significantly prolonged the survival time when compared with pSAG1 or p14-3-3 (P<0.05).
  
  
  CONCLUSIONS
  The study suggested that T. gondii 14-3-3 protein can induce effective immune responses in BALB/c mice and was a novel DNA vaccine candidate against toxoplasmosis, and the immune protective efficacy elicited by SAG1 gene was also demonstrated. Our results also showed multi-gene vaccine significantly enhanced immune responses and protective efficacy and was superior to the single-gene vaccine.
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, Peoples Republic of China.
authors.forename: Min
authors.initials: M
authors.lastname: Meng
authors.forename: Shenyi
authors.initials: S
authors.lastname: He
authors.forename: Guanghui
authors.initials: G
authors.lastname: Zhao
authors.forename: Yang
authors.initials: Y
authors.lastname: Bai
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Zhou
authors.forename: Hua
authors.initials: H
authors.lastname: Cong
authors.forename: Gang
authors.initials: G
authors.lastname: Lu
authors.forename: Qunli
authors.initials: Q
authors.lastname: Zhao
authors.forename: Xing-Quan
authors.initials: XQ
authors.lastname: Zhu
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics / Q000276:immunology*; D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006367:HeLa Cells; D006801:Humans; D007111:Immunity, Cellular; D056724:Immunity, Humoral; D007114:Immunization; D007074:Immunoglobulin G / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D016052:Protozoan Vaccines / Q000276:immunology; D011897:Random Allocation; D011993:Recombinant Fusion Proteins; D013047:Specific Pathogen-Free Organisms; D016019:Survival Analysis; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology*; D014123:Toxoplasmosis / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control*; D019444:Vaccines, DNA / Q000276:immunology
chemical_list: D048948:14-3-3 Proteins; D000953:Antigens, Protozoan; D016207:Cytokines; D007074:Immunoglobulin G; D015800:Protozoan Proteins; D016052:Protozoan Vaccines; D011993:Recombinant Fusion Proteins; C047168:SAG1 antigen, Toxoplasma; D019444:Vaccines, DNA