title: SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts.
abstract: BACKGROUND
  Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts.
  
  
  METHODS
  To accomplish our goals, we performed in silico analysis of the amino acid sequence of SAG2A, correlating the predictions with in vitro stimulation of antigen presenting cells and serological assays.
  
  
  RESULTS
  Structure modeling predicts that SAG2A protein possesses an unfolded C-terminal end, which varies its conformation within distinct strain types of T. gondii. This structure within the protein shelters a known B-cell immunodominant epitope, which presents low identity with its closest phyllogenetically related protein, an orthologue predicted in Neospora caninum. In agreement with the in silico observations, sera of known T. gondii infected mice and goats recognized recombinant SAG2A, whereas no serological cross-reactivity was observed with samples from N. caninum animals. Additionally, the C-terminal end of the protein was able to down-modulate pro-inflammatory responses of activated macrophages and dendritic cells.
  
  
  CONCLUSIONS
  Altogether, we demonstrate herein that recombinant SAG2A protein from T. gondii is immunologically relevant in the host-parasite interface and may be targeted in therapeutic and diagnostic procedures designed against the infection.
authors.affiliation: Laboratório de Imunoparasitologia "Dr, Mário Endsfeldz Camargo", Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, Av, Pará 1720-Bloco 4C, Campus Umuarama, Uberlândia, Minas Gerais 38.400-902, Brazil.
authors.forename: Arlindo G
authors.initials: AG
authors.lastname: Macêdo
authors.forename: Jair P
authors.initials: JP
authors.lastname: Cunha
authors.forename: Thyago H S
authors.initials: TH
authors.lastname: Cardoso
authors.forename: Murilo V
authors.initials: MV
authors.lastname: Silva
authors.forename: Fernanda M
authors.initials: FM
authors.lastname: Santiago
authors.forename: João S
authors.initials: JS
authors.lastname: Silva
authors.forename: Carlos P
authors.initials: CP
authors.lastname: Pirovani
authors.forename: Deise A O
authors.initials: DA
authors.lastname: Silva
authors.forename: José R
authors.initials: JR
authors.lastname: Mineo
authors.forename: Tiago W P
authors.initials: TW
authors.lastname: Mineo
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D003429:Cross Reactions; D018985:Epitopes, B-Lymphocyte / Q000235:genetics / Q000276:immunology; D006041:Goats; D054884:Host-Pathogen Interactions; D006801:Humans; D007113:Immunity, Innate; D016056:Immunodominant Epitopes / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D014122:Toxoplasma / Q000235:genetics* / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D018985:Epitopes, B-Lymphocyte; D016056:Immunodominant Epitopes; D015800:Protozoan Proteins; C067547:surface antigen P22, Toxoplasma