title: Surface protein Adr2 of Rickettsia rickettsii induced protective immunity against Rocky Mountain spotted fever in C3H/HeN mice.
abstract: BACKGROUND
  Rickettsia rickettsii is the pathogen of Rocky Mountain spotted fever (RMSF), a life-threatening tick-transmitted infection. Adr2 was a surface-exposed adhesion protein of R. rickettsii and its immunoprotection against RMSF was investigated in mice.
  
  
  METHODS
  Recombinant Adr2 (rAdr2) was used to immunize C3H/HeN mice, and the rickettsial loads in organs of the mice were detected after challenge with R. rickettsii. The levels of specific antibodies of sera from the immunized mice were determined and the sera from immunized mice were applied to neutralize R. rickettsii. Proliferation and cytokine secretion of CD4(+) and CD8(+) T cells isolated from R. rickettsii-infected mice were also assayed after rAdr2 stimulation.
  
  
  RESULTS
  After R. rickettsii challenge, the rickettsial loads in spleens, livers, and lungs were significantly lower and the impairment degrees of these organs in rAdr2-immunized mice were markedly slighter, compared with those in negative control mice. The ratio of specific IgG2a/IgG1 of rAdr2-immunized mice kept increasing during the immunization. After treatment with rAdr2-immunized sera, the total number of R. rickettsii organisms adhering and invading host cells was significantly lower than that treated with PBS-immunized sera. Interferon-γ secretion by CD4(+) or CD8(+) T cells and tumor necrosis factor-α secretion by CD4(+) T cells from R. rickettsii-infected mice were respectively significantly greater than those from uninfected mice after rAdr2 stimulation.
  
  
  CONCLUSIONS
  Adr2 is a protective antigen of R. rickettsii. Protection offered by Adr2 is mainly dependent on antigen-specific cell-mediated immune responses, including efficient activity of CD4(+) and CD8(+) T cells to produce great amount of TNF-α and/or IFN-γ as well as rapid increase of specific IgG2a, which synergistically activate and opsonize host cells to killing intracellular rickettsiae.
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong-Dia-Jie Street, Fengtai, Beijing 100071, China.
authors.forename: Wenping
authors.initials: W
authors.lastname: Gong
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong-Dia-Jie Street, Fengtai, Beijing 100071, China. Electronic address: xiongxiaolu624@sohu.com.
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Xiong
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong-Dia-Jie Street, Fengtai, Beijing 100071, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Qi
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong-Dia-Jie Street, Fengtai, Beijing 100071, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Jiao
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong-Dia-Jie Street, Fengtai, Beijing 100071, China.
authors.forename: Changsong
authors.initials: C
authors.lastname: Duan
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong-Dia-Jie Street, Fengtai, Beijing 100071, China. Electronic address: wenbohai@yahoo.com.
authors.forename: Bohai
authors.initials: B
authors.lastname: Wen
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000276:immunology*; D058491:Bacterial Load; D001428:Bacterial Vaccines / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D005260:Female; D007111:Immunity, Cellular; D056724:Immunity, Humoral; D007074:Immunoglobulin G / Q000097:blood; D007371:Interferon-gamma / Q000276:immunology; D051379:Mice; D008809:Mice, Inbred C3H; D011994:Recombinant Proteins / Q000276:immunology; D012284:Rickettsia rickettsii / Q000276:immunology; D012373:Rocky Mountain Spotted Fever / Q000517:prevention & control*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma
keywords: Adr2; Cell-mediated immunity; Rickettsia rickettsii; Rocky Mountain spotted fever; Serum neutralization.