title: Vaccination with toxofilin DNA in combination with an alum-monophosphoryl lipid A mixed adjuvant induces significant protective immunity against Toxoplasma gondii.
abstract: A widely prevalent disease, toxoplasmosis poses serious health threats to both humans and animals; therefore, development of an ideal DNA vaccine against Toxoplasma gondii is needed eagerly. The purpose of the present study is to assess the protective efficacy of a DNA vaccine encoding the T. gondii toxofilin gene (pEGFP-toxofilin). In addition, toxofilin DNA vaccine combined with the individual adjuvants, alum or monophosphoryl lipid A (MPLA), or a mixture of alum-MPLA adjuvant were screened for their ability to enhance antibody responses.
  
  
  
  Using bioinformatics, we analyzed the gene and amino acid sequences of the toxofilin protein, recognizing and identifying several potential linear B and T helper (Th)-1 cell epitopes. BALB/c mice were immunized three times with either toxofilin DNA vaccine alone or in combination with the adjuvants such as alum, MPLA or an alum-MPLA mixture. The systemic immune response was evaluated by cytokine, the percentage of CD4 (+) and CD8 (+) T cells and specific antibody measurement. Two weeks after the last immunization, protective efficacy was evaluated by challenging intraperitoneally with 1 × 104tachyzoites of T. gondii or intragastrically with 20 cysts of T. gondii PRU strain.
  
  
  
  All experimentally immunized mice developed strong humoral and cellular immune responses compared with the control groups. Moreover, by comparison with the non-adjuvant toxofilin DNA vaccine group, adding alum adjuvant to toxofilin DNA vaccine resulted in an increase in humoral response and a skewed Th2 response. However, the MPLA adjuvant with toxofilin DNA vaccine induced significantly enhanced humoral and Th1-biased immune responses. Importantly, the co-administration of alum-MPLA adjuvant in combination with the toxofilin DNA vaccine shifted the Th2 immune response to a Th1 response compared with the alum-toxofilin group, and elicited the strongest humoral and Th1 responses among all the groups. At the same time, a longer survival time and less cyst amounts against T. gondii infection were also observed in the alum-MPLA-toxofilin group in comparison with single or no adjuvant groups.
  
  
  
  Toxoplasma gondii toxofilin is a promising vaccine candidate that warrants further development. Co-administration of the alum-MPLA adjuvant mixture with DNA vaccine could effectively enhance immunogenicity and strongly skew the cellular immune response towards a Th1 phenotype.
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China.
authors.forename: Pengxia
authors.initials: P
authors.lastname: Song
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China. shenyi.he@hotmail.com.
authors.forename: Shenyi
authors.initials: S
authors.lastname: He
authors.affiliation: Department of Pediatrics, Provincial Hospital Affiliated to Shandong University, Shandong University School of Medicine, 250021, Jinan, Shandong Province, People's Republic of China.
authors.forename: Aihua
authors.initials: A
authors.lastname: Zhou
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China.
authors.forename: Gang
authors.initials: G
authors.lastname: Lv
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Guo
authors.affiliation: Shandong University School of Medicine, 250021, Jinan, Shandong Province, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China.
authors.forename: Yali
authors.initials: Y
authors.lastname: Han
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China.
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Hao
authors.affiliation: Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, People's Republic of China.
authors.forename: Hua
authors.initials: H
authors.lastname: Cong
mesh_terms: D051344:Actin Capping Proteins / Q000235:genetics* / Q000276:immunology; D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000534:Alum Compounds / Q000494:pharmacology; D000818:Animals; D000917:Antibody Formation / Q000187:drug effects; D005260:Female; D007111:Immunity, Cellular; D008050:Lipid A / Q000031:analogs & derivatives* / Q000276:immunology / Q000494:pharmacology; D008807:Mice, Inbred BALB C; D015800:Protozoan Proteins / Q000235:genetics* / Q000276:immunology; D016052:Protozoan Vaccines / Q000276:immunology / Q000494:pharmacology*; D014122:Toxoplasma / Q000276:immunology / Q000472:pathogenicity; D014123:Toxoplasmosis / Q000276:immunology* / Q000517:prevention & control; D019444:Vaccines, DNA / Q000276:immunology / Q000494:pharmacology
chemical_list: D051344:Actin Capping Proteins; D000276:Adjuvants, Immunologic; D000534:Alum Compounds; D008050:Lipid A; D015800:Protozoan Proteins; D016052:Protozoan Vaccines; D019444:Vaccines, DNA; C406004:toxofilin protein, Toxoplasma gondii; C041524:aluminum sulfate; C048436:monophosphoryl lipid A
keywords: Adjuvant; Bioinformatics; DNA vaccine; Toxofilin; Toxoplasma gondii