title: Protection via a ROM4 DNA vaccine and peptide against Toxoplasma gondii in BALB/c mice.
abstract: Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite with a broad host range including most warm-blooded animals, including humans. T. gondii surface antigen 1 (SAG1) is a well-characterized T. gondii antigen. T. gondii expresses five nonmitochondrial rhomboid intramembrane proteases, TgROM1-5. TgROM4 is uniformly distributed on the surface of T. gondii and involved in regulating MIC2, MIC3, MIC6, and AMA1 during T. gondii invasion of host cells. Bioinformatics have predicted ROM4 B-cell and T-cell epitopes. Immunization strategy is also a key factor in determining the effectiveness of the immune response and has gained increasing attention in T. gondii vaccine research. In this study, we used a DNA prime-peptide boost vaccination regimen to assess the protective efficacy of various vaccination strategies using TgROM4.
  
  
  
  We identified a polypeptide (YALLGALIPYCVEYWKSIPR) using a bioinformatics approach, and immunized mice using a DNA-prime and polypeptide-boost regimen. BALB/c mice were randomly divided into six groups, including three experimental groups (peptide, pROM4 and pROM4/peptide) and three control groups (PBS, pEGFP-C1 and pSAG1). Mice were then immunized intramuscularly four times. After immunization, IgG and cytokine productions were determined using enzyme-linked immunosorbent assays. The survival time of mice was evaluated after challenge with tachyzoites of T. gondii RH strain. Additionally, the number of cysts in the brain was determined after intragastric challenge with cysts of T. gondii PRU strain.
  
  
  
  Mice vaccinated with different immunization regimens (peptide, pROM4 and pROM4/peptide) elicited specific humoral and cellular responses, with high levels of IgG, IgG2a, and interferon (IFN)-γ. Moreover, IgG, IgG2a and IFN-γ levels were highest in the pROM4/peptide group. Immunized mice, especially those in the pROM4/peptide group, had prolonged survival times after challenge with tachyzoites and reduced numbers of brain cysts after infection compared with negative controls.
  
  
  
  A DNA prime-peptide boost regimen based on ROM4 elicited the highest level of humoral and cellular immune responses among immunization regimens, and may be a promising approach to increase the efficacy of DNA immunization.
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 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: Lu
authors.affiliation: Qilu Hospital of shandong University, Qingdao, 266035, Shandong Province, People's Republic of China.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Zhao
authors.affiliation: Department of Ji Nan Children's Hospital, 250022, Jinan, Shandong Province, People's Republic of China.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
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: 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.
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: 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: Hua
authors.initials: H
authors.lastname: Cong
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
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007111:Immunity, Cellular / Q000187:drug effects; D056724:Immunity, Humoral / Q000187:drug effects; D007074:Immunoglobulin G / Q000187:drug effects* / Q000276:immunology; D007273:Injections, Intramuscular; D007371:Interferon-gamma / Q000187:drug effects* / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D010447:Peptide Hydrolases / Q000235:genetics* / Q000276:immunology; D010455:Peptides / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics* / Q000276:immunology; D016052:Protozoan Vaccines / Q000494:pharmacology*; D014122:Toxoplasma / Q000276:immunology; D014124:Toxoplasmosis, Animal / Q000517:prevention & control*; D014611:Vaccination; D019444:Vaccines, DNA / Q000494:pharmacology*
chemical_list: D000953:Antigens, Protozoan; D007074:Immunoglobulin G; D010455:Peptides; D015800:Protozoan Proteins; D016052:Protozoan Vaccines; D019444:Vaccines, DNA; D007371:Interferon-gamma; D010447:Peptide Hydrolases; C560858:ROM4 protein, Toxoplasma gondii
keywords: Bioinformatics; Immunization strategy; Peptide; ROM4; Toxoplasma gondii; Vaccine