title: Identification of a sporozoite-specific member of the Toxoplasma SAG superfamily via genetic complementation.
abstract: Toxoplasma gondii sporozoites possess an array of stage-specific antigens that are localized to the membrane and internal cellular space, as well as secreted into the primary parasitophorous vacuole. Specific labelling of viable sporozoites excysted from oocysts reveals a complex admixture of surface proteins partially shared with tachyzoites. SAG1, SRS3 and SAG3 were detected on sporozoites as well as numerous minor antigens. In contrast, tachyzoite SAG2A and B were completely absent whereas a dominant 25 kDa protein was unique to the sporozoite surface. The sporozoite gene encoding this protein was identified in tachyzoites genetically complemented with a sporozoite cDNA library and cloned via site-specific recombination into a bacterial shuttle vector. The sporozoite cDNA identified in these experiments encoded a protein with conserved structural features of the prototypical T. gondii SAG1 (P30) and shared sequence identity with surface proteins from Sarcocystis spp. This new member of the SAG superfamily was designated SporoSAG. Expression of SporoSAG in tachyzoites conferred enhanced invasion on transgenic parasites suggesting a role for this protein in oocyst/sporozoite transmission to susceptible hosts.
authors.affiliation: Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana 59717-3610, USA.
authors.forename: Jay R
authors.initials: JR
authors.lastname: Radke
authors.forename: Marc-Jan
authors.initials: MJ
authors.lastname: Gubbels
authors.forename: Maria E
authors.initials: ME
authors.lastname: Jerome
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Radke
authors.forename: Boris
authors.initials: B
authors.lastname: Striepen
authors.forename: Michael W
authors.initials: MW
authors.lastname: White
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000032:analysis* / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D000954:Antigens, Surface / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D003001:Cloning, Molecular; D016054:DNA, Protozoan / Q000737:chemistry / Q000302:isolation & purification; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan; D005816:Genetic Complementation Test; D008562:Membrane Glycoproteins / Q000032:analysis / Q000276:immunology; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D034101:Sporozoites / Q000235:genetics / Q000276:immunology*; D014122:Toxoplasma / Q000235:genetics* / Q000254:growth & development / Q000276:immunology*
chemical_list: D000953:Antigens, Protozoan; D000954:Antigens, Surface; D016054:DNA, Protozoan; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; C047168:SAG1 antigen, Toxoplasma; C087692:SAG3 protein, Toxoplasma gondii; C067547:surface antigen P22, Toxoplasma