title: Differentiation of Neospora hughesi from Neospora caninum based on their immunodominant surface antigen, SAG1 and SRS2.
abstract: Neospora hughesi is a newly recognised parasite that is closely related to Neospora caninum, and is a cause of equine protozoal myeloencephalitis. We have characterised two N. hughesi immunodominant tachyzoite antigens which exhibit antigenic and molecular differences from the homologous tachyzoite antigens on N. caninum. These antigens on N. hughesi are referred to as NhSAG1 and NhSRS2, using the same mnemonics as used for the N. caninum antigens (NcSAG1 and NcSRS2), and are homologous to Toxoplasma gondii surface antigen 1 (SAG1) and SAG1-related sequence 2 (SRS2). The NcSAG1 and NcSRS2 were antigenically conserved in six different N. caninum isolates from cattle and dogs. The two equine-derived Neospora isolates, one designated as N. hughesi, were similar to each other but different from N. caninum. There was 6% difference in amino acid identity between NcSAG1 and NhSAG1, whereas there was a 9% difference when NcSRS2 and NhSRS2 were compared. The polymorphism of these genes and their corresponding proteins provide additional markers which can be used to distinguish N. caninum from N. hughesi.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia 65205, USA. marshae@missouri.edu
authors.forename: A E
authors.initials: AE
authors.lastname: Marsh
authors.forename: D K
authors.initials: DK
authors.lastname: Howe
authors.forename: G
authors.initials: G
authors.lastname: Wang
authors.forename: B C
authors.initials: BC
authors.lastname: Barr
authors.forename: N
authors.initials: N
authors.lastname: Cannon
authors.forename: P A
authors.initials: PA
authors.lastname: Conrad
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D000954:Antigens, Surface / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D015153:Blotting, Western; D002417:Cattle; D003048:Coccidiosis / Q000469:parasitology / Q000662:veterinary; D004285:Dogs; D004679:Encephalomyelitis / Q000469:parasitology / Q000662:veterinary; D006734:Horse Diseases / Q000469:parasitology; D006736:Horses; D016056:Immunodominant Epitopes / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D008969:Molecular Sequence Data; D018688:Neospora / Q000145:classification* / Q000276:immunology* / Q000302:isolation & purification; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment
chemical_list: D000953:Antigens, Protozoan; D000954:Antigens, Surface; D016056:Immunodominant Epitopes; D015800:Protozoan Proteins; C047168:SAG1 antigen, Toxoplasma; C115389:SRS2 protein, Neospora caninum