Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2000
Publication Date: N/A
Interpretive Summary: Sarcocystis neurona is a single-celled parasite. It causes a fatal neurologic disease in horses, equine protozoal myeloencephalitis (EPM). One way to maintain live parasites is in cell culture. Cell cultured S. neurona is routinely used for antigen preparation. Scientists at the Beltsville Agricultural Research Center and Oregon State University have found that S. neurona can lose pathogenicity by a prolonged passage in culture. They recommend freezing the parasite in liquid nitrogen during early passages. These results will be of use to parasitologists, its biologists, and diagnosticians.
Technical Abstract: An isolate of Sarcocystis neurona (SN7) was obtained from the spinal cord of a horse with neurologic signs. The parasite was isolated in cultures of bovine monocytes and equine spleen cells. The organism divided by endopolygeny and completed at least 1 asexual cycle in cell cultures in 3 days. The parasite was maintained by subpassages in bovine monocytes for 10 0months when it was found to be non pathogenic to immunosuppressed nude mic and gamma interferon knockout (KO) mice. Six KO mice and 2 mice that were inoculated subcutaneously with 106 to 107 culture-derived merozoites (approximately 27 passages), remained clinically normal and had no demonstrable S. neurona. Revival of a low passage (fifth passage) of the initial isolate stored at -195 C for 12 months retained its pathogenicity for KO mice. Four KO mice inoculated subcutaneously with merozoites (106) derived from the fifth passage culture died of acute neural sarcocystosis between 24 and 29 days post-inoculation. These results suggest that prolonged passage in cell culture may affect the pathogenicity of some strains of S. neurona. No differences were found in Western blot patterns using antigens from the low and high passage merozoites of the SN7 isolate.