Investigation of SnSPR1, a novel and abundant surface protein of Sarcocystis neurona merozoites.
An expressed sequence tag (EST) sequencing project has produced over 15,000 partial cDNA sequences from the equine pathogen Sarcocystis neurona. While many of the sequences are clear homologues of previously characterized genes, a significant number of the S. neurona ESTs do not exhibit similarity to anything in the extensive sequence databases that have been generated. In an effort to characterize parasite proteins that are novel to S. neurona, a seemingly unique gene was selected for further investigation based on its abundant representation in the collection of ESTs and the predicted presence of a signal peptide and glycolipid anchor addition on the encoded protein. The gene was expressed in E. coli, and monospecific polyclonal antiserum against the recombinant protein was produced by immunization of a rabbit. Characterization of the native protein in S. neurona merozoites and schizonts revealed that it is a low molecular weight surface protein that is expressed throughout intracellular development of the parasite. The protein was designated Surface Protein 1 (SPR1) to reflect its display on the outer surface of merozoites and to distinguish it from the ubiquitous SAG/SRS surface antigens of the heteroxenous Coccidia. Interestingly, infection assays in the presence of the polyclonal antiserum suggested that SnSPR1 plays some role in attachment and/or invasion of host cells by S. neurona merozoites. The work described herein represents a general template for selecting and characterizing the various unidentified gene sequences that are plentiful in the EST databases for S. neurona and other apicomplexans. Furthermore, this study illustrates the value of investigating these novel sequences since it can offer new candidates for diagnostic or vaccine development while also providing greater insight into the biology of these parasites.
Zhang
Deqing
D
Department of Veterinary Sciences, University of Kentucky, Gluck Equine Research Center, Lexington, KY 40546-0099, USA.
Howe
Daniel K
DK
D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics / Q000302:isolation & purification; D000954:Antigens, Surface / Q000276:immunology; D002417:Cattle; D002460:Cell Line; D018076:DNA, Complementary / Q000737:chemistry; D020224:Expressed Sequence Tags; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D005786:Gene Expression Regulation; D015723:Gene Library; D006734:Horse Diseases / Q000469:parasitology; D006736:Horses; D020066:Merozoite Surface Protein 1 / Q000235:genetics / Q000302:isolation & purification; D052940:Merozoites; D008969:Molecular Sequence Data; D008970:Molecular Weight; D015800:Protozoan Proteins / Q000235:genetics* / Q000302:isolation & purification; D011817:Rabbits; D012522:Sarcocystis / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D012523:Sarcocystosis / Q000469:parasitology / Q000662:veterinary*; D016415:Sequence Alignment / Q000662:veterinary
D000953:Antigens, Protozoan; D000954:Antigens, Surface; D018076:DNA, Complementary; D020066:Merozoite Surface Protein 1; D015800:Protozoan Proteins