title: Alpha-galactosylceramide enhances protective immunity induced by DNA vaccine of the SAG5D gene of Toxoplasma gondii.
abstract: BACKGROUND
  Toxoplasmosis caused by the intracellular parasite Toxoplasma gondii (T. gondii) is a global epidemic parasitic disease. DNA vaccines play an important role in preventing the spread of toxoplasmosis. SAG family genes encoding particular surface proteins of T. gondii are the best candidates of DNA vaccine. As a member of SAG family genes, SAG5 gene has been proved to have better antigenic than SAG1. In addition, alpha-Galactosylceramide (α-GalCer) was used to be an adjuvant in malaria vaccine and received positive results. In this study, the effect of the DNA vaccine enhanced by α-GalCer was evaluated by immunizing BALB/c mice.
  
  
  METHODS
  In the present study, SAG5D gene of T. gondii was cloned, sequenced, and biologically characterized. BALB/c mice were randomly divided into five groups, including three experimental groups (pEGFP-C1-SAG5D, α-GalCer and α-GalCer/pEGFP-C1-SAG5D) and two control groups (PBS and pEGFP-C1), and were immunized intramuscularly three times. The levels of IgG antibodies and cytokine productions in mouse sera were determined by enzyme-linked immunosorbent assays (ELISA). Two weeks after the last immunization, all mice were challenged intraperitoneally with 1 × 10(4) tachyzoites of T. gondii and the survival time of mice was recorded.
  
  
  RESULTS
  A significant level of increase of IgG response against the soluble tachyzoite antigens (STAg) was detected by ELISA in experimental group. It revealed relatively high level of IFN-γ production by the spleen cells. There were higher productions of interleukin-4 (IL-4) in α-GalCer treated groups compared to control groups. Challenge experiment showed a longer survival period (11 days compared with 5 days in control) in SAG5D DNA vaccinated mice was found after a lethal challenge with T. gondii RH strain.
  
  
  CONCLUSIONS
  The present study suggested that T. gondii SAG5D was a novel and positive DNA vaccine candidate against toxoplasmosis. In addition, the adjuvant (α-GalCer) enhanced the body's cellular immune response and prolonged the survival time of mice after challenge.
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. lvgang700@126.com.
authors.forename: Gang
authors.initials: G
authors.lastname: Lu
authors.affiliation: Department of Pediatrics, Provincial Hospital Affiliated to Shandong University, Shandong University School of Medicine, Jinan, Shandong Province, 250021, Peoples Republic of China. zhouah@sdu.edu.cn.
authors.forename: Aihua
authors.initials: A
authors.lastname: Zhou
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. mengmin2011@126.com.
authors.forename: Min
authors.initials: M
authors.lastname: Meng
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. wanglinfenghuaxue@163.com.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. hangreen5508@163.com.
authors.forename: Yali
authors.initials: Y
authors.lastname: Han
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. guojingjing_100@126.com.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. zhouhy@sdu.edu.cn.
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. conghua@sdu.edu.cn.
authors.forename: Hua
authors.initials: H
authors.lastname: Cong
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. qunlizhao@yeah.net.
authors.forename: Qunli
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, Peoples Republic of China. xingquanzhu1@hotmail.com.
authors.forename: Xing-Quan
authors.initials: XQ
authors.lastname: Zhu
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China. shenyi.he@hotmail.com.
authors.forename: Shenyi
authors.initials: S
authors.lastname: He
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000276:immunology; D016207:Cytokines / Q000187:drug effects* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005699:Galactosylceramides / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000187:drug effects* / Q000276:immunology; D015847:Interleukin-4 / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D016052:Protozoan Vaccines / Q000494:pharmacology*; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000276:immunology / Q000517:prevention & control*; D019444:Vaccines, DNA / Q000494:pharmacology*
chemical_list: D000276:Adjuvants, Immunologic; D000954:Antigens, Surface; D016207:Cytokines; D005699:Galactosylceramides; D007074:Immunoglobulin G; D015800:Protozoan Proteins; D016052:Protozoan Vaccines; D019444:Vaccines, DNA; C493154:alpha-galactosylceramide; D015847:Interleukin-4