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Abstract
Advances in the understanding of equine protozoal myeloencephalitis (EPM) are reviewed. It is now apparent that EPM can be caused by either of 2 related protozoan parasites, Sarcocystis neurona and Neospora hughesi, although S neurona is the most common etiologic pathogen. Horses are commonly infected, but clinical disease occurs only infrequently; the factors influencing disease occurrence are not well understood. Epidemiologic studies have identified risk factors for the development of EPM, including the presence of opossums and prior stressful health-related events. Attempts to reproduce EPM experimentally have reliably induced antibody responses in challenged horses, but have not consistently produced neurologic disease. Diagnosis of EPM has improved by detecting intrathecal antibody production against the parasite. Sulfadiazine/pyrimethamine (ReBalance) and the triazine compounds diclazuril (Protazil) and ponazuril (Marquis) are effective anticoccidial drugs that are now available as FDA-approved treatments for EPM.
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Affiliation(s)
- Robert J MacKay
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, 2015 Southwest 16th Avenue, PO Box 100136, Gainesville, FL 32610-0125, USA
| | - Daniel K Howe
- Department of Veterinary Science, M.H. Gluck Equine Research Center, University of Kentucky, 108 Gluck Equine Research Center, Lexington, KY 40546-0099, USA.
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Hay AN, Potter A, Lindsay D, LeRoith T, Zhu J, Cashwell S, Witonsky S, Leeth C. Interferon gamma protective against Sarcocystis neurona encephalitis in susceptible murine model. Vet Immunol Immunopathol 2021; 240:110319. [PMID: 34474260 DOI: 10.1016/j.vetimm.2021.110319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 07/30/2021] [Accepted: 08/26/2021] [Indexed: 11/27/2022]
Abstract
Sarcocystis neurona is the predominant etiological agent of the infectious equine neurologic disease, equine protozoal myeloencephalitis (EPM), which is prevalent in the United States. A wealth of knowledge about S. neurona biology and its life cycle has accumulated over the last several decades. However, much remains unknown about the aberrant equine host's immune response to S. neurona and the relatively high prevalence of exposure to the protozoa but relatively infrequent occurrence of clinical neurologic disease. Mouse models simulating EPM are commonly used to study the disease due to numerous challenges associated with studying the disease in horses. The critical role of the cytokine, interferon gamma (IFNγ), in protection against S. neurona encephalitis has been well established as Ifnγ-/- mice are highly susceptible to S. neurona encephalitis. However, there are discrepancies in the literature regarding S. neurona disease susceptibility in lymphocyte deficient mice, lacking T-lymphocytes and their associated Ifnγ production. In the current study, we investigated S. neurona encephalitis susceptibility in 2 genetically different strains of lymphocyte null mice, C57Bl/6 (B6).scid and Balb/c.scid. The B6.scid mouse was determined to be susceptible to S. neurona encephalitis as 100 % of infected mice developed neurologic disease within 60 days post infection (DPI). The Balb/c.scid mouse was nearly disease resistant as only 10 % of mice developed neurologic disease 60 DPI. Encephalitis was histologically demonstrable and S. neurona was identified in cerebellar samples collected from B6.scid but absent in Balb/c.scid mice. To further investigate the importance of T-lymphocyte derived Ifnγ, T- lymphocytes were adoptively transferred into B6.scid mice. The adoptive transfer of Ifnγ competent T- lymphocytes offered complete protection against S. neurona encephalitis but transfer of Ifnγ deficient T- lymphocytes did not with 100 % of these recipient mice succumbing to S. neruona encephalitis. Histological analysis of collected cerebellar samples confirmed the presences of S. neurona and encephalitis in recipient mice that developed neurologic disease. These studies show that the background strain is critical in studying SCID susceptibility to S. neurona disease and suggest a protective role of Ifnγ producing T- lymphocytes in S. neurona encephalitis susceptible mice.
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Affiliation(s)
- Alayna N Hay
- Virginia Tech, Department of Animal and Poultry Sciences, 175 West Campus Drive, 3280 Litton Reaves Hall, Blacksburg, VA, 24061, United States
| | - Ashley Potter
- Virginia Tech, Department of Animal and Poultry Sciences, 175 West Campus Drive, 3280 Litton Reaves Hall, Blacksburg, VA, 24061, United States
| | - David Lindsay
- Department of Biomedical Sciences and Pathobiology, Virginia- Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Tanya LeRoith
- Department of Biomedical Sciences and Pathobiology, Virginia- Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Jing Zhu
- Virginia Tech, Department of Animal and Poultry Sciences, 175 West Campus Drive, 3280 Litton Reaves Hall, Blacksburg, VA, 24061, United States
| | - Sarah Cashwell
- Virginia Tech, Department of Animal and Poultry Sciences, 175 West Campus Drive, 3280 Litton Reaves Hall, Blacksburg, VA, 24061, United States
| | - Sharon Witonsky
- Department of Large Animal Clinical Sciences, Virginia- Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, 24061, United States
| | - Caroline Leeth
- Virginia Tech, Department of Animal and Poultry Sciences, 175 West Campus Drive, 3280 Litton Reaves Hall, Blacksburg, VA, 24061, United States.
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Wang D, Quan Y, Yan Q, Morales JE, Wetsel RA. Targeted Disruption of the β2-Microglobulin Gene Minimizes the Immunogenicity of Human Embryonic Stem Cells. Stem Cells Transl Med 2015; 4:1234-45. [PMID: 26285657 DOI: 10.5966/sctm.2015-0049] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 06/22/2015] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Human embryonic stem cells (hESCs) are a promising source of cells for tissue regeneration, yet histoincompatibility remains a major challenge to their clinical application. Because the human leukocyte antigen class I (HLA-I) molecules are the primary mediators of immune rejection, we hypothesized that cells derived from a hESC line lacking HLA-I expression could be transplanted without evoking a robust immune response from allogeneic recipients. In the present study, we used the replacement targeting strategy to delete exons 2 and 3 of β2-microglobulin on both gene alleles in hESCs. Because β2-microglobulin serves as the HLA-I light chain, disruption of the β2-microglobulin gene led to complete HLA-I deficiency on the cell surface of hESCs and their derivatives. Therefore, these cells were resistant to CD8+ T-cell-mediated destruction. Although interferon-γ (IFN-γ) treatment significantly induced β2-microglobulin expression, promoting CD8+ T cell-mediated killing of control hESCs and their derivatives, CD8+ T-cell-mediated cytotoxicity was barely observed with β2-microglobulin-null hESCs and their derivatives treated with IFN-γ. This genetic manipulation to disrupt HLA-I expression did not affect the self-renewal capacity, genomic stability, or pluripotency of hESCs. Despite being relatively sensitive to natural killer (NK) cell-mediated killing due to the lack of HLA-I expression, when transplanted into NK cell-depleted immunocompetent mice, β2-microglobulin-null hESCs developed into tumors resembling those derived from control hESCs in severe combined immunodeficiency mice. These results demonstrate that β2-microglobulin-null hESCs significantly reduce immunogenicity to CD8+ T cells and might provide a renewable source of cells for tissue regeneration without the need for HLA matching in the future. SIGNIFICANCE This study reports the generation of a novel β2-microglobulin (B2M)-/- human embryonic stem cell (hESC) line. Differentiated mature cells from this line do not express cell surface human leukocyte antigen molecules even after interferon-γ stimulation and are resistant to alloreactive CD8+ T cells. Moreover, this B2M-/- hESC line contains no off-target integration or cleavage events, is devoid of stable B2M mRNA, exhibits a normal karyotype, and retains its self-renewal capacity, genomic stability, and pluripotency. Although B2M-/- hESC-derived cells are more susceptible to natural killer (NK) cells, murine transplantation studies have indicated that they are, overall, much less immunogenic than normal hESCs. Thus, these data show for the first time that, in vivo, the advantages provided by B2M-/- hESC-derived cells in avoiding CD8+ T-cell killing appear significantly greater than any disadvantage caused by increased susceptibility to NK cells.
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Affiliation(s)
- Dachun Wang
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases and Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Yuan Quan
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases and Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Qing Yan
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases and Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - John E Morales
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases and Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Rick A Wetsel
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases and Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas, USA
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Dubey JP, Howe DK, Furr M, Saville WJ, Marsh AE, Reed SM, Grigg ME. An update on Sarcocystis neurona infections in animals and equine protozoal myeloencephalitis (EPM). Vet Parasitol 2015; 209:1-42. [PMID: 25737052 DOI: 10.1016/j.vetpar.2015.01.026] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/27/2015] [Accepted: 01/29/2015] [Indexed: 01/27/2023]
Abstract
Equine protozoal myeloencephalitis (EPM) is a serious disease of horses, and its management continues to be a challenge for veterinarians. The protozoan Sarcocystis neurona is most commonly associated with EPM. S. neurona has emerged as a common cause of mortality in marine mammals, especially sea otters (Enhydra lutris). EPM-like illness has also been recorded in several other mammals, including domestic dogs and cats. This paper updates S. neurona and EPM information from the last 15 years on the advances regarding life cycle, molecular biology, epidemiology, clinical signs, diagnosis, treatment and control.
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Affiliation(s)
- J P Dubey
- United States Department of Agriculture, Agricultural Research Service, Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Building 1001, Beltsville, MD 20705-2350, USA.
| | - D K Howe
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546-0099, USA
| | - M Furr
- Marion du Pont Scott Equine Medical Center, Virginia Maryland Regional College of Veterinary Medicine, 17690 Old Waterford Road, Leesburg, VA 20176, USA
| | - W J Saville
- Department of Veterinary Preventive Medicine, The Ohio State University, 1920 Coffey Road, Columbus, OH 43210, USA
| | - A E Marsh
- Department of Veterinary Preventive Medicine, The Ohio State University, 1920 Coffey Road, Columbus, OH 43210, USA
| | - S M Reed
- Rood and Riddle Equine Hospital, Lexington, KY 40511, USA
| | - M E Grigg
- Molecular Parasitology Section, Laboratory of Parasitic Diseases, National Institutes of Health, National Institutes of Allergy, and Infectious Diseases, 4 Center Drive, Room B1-06, Bethesda, MD 20892, USA
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Effects of Experimental Sarcocystis neurona-Induced Infection on Immunity in an Equine Model. J Vet Med 2014; 2014:239495. [PMID: 26464923 PMCID: PMC4590861 DOI: 10.1155/2014/239495] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 08/21/2014] [Accepted: 09/15/2014] [Indexed: 11/17/2022] Open
Abstract
Sarcocystis neurona is the most common cause of Equine Protozoal Myeloencephalitis (EPM), affecting 0.5-1% horses in the United States during their lifetimes. The objective of this study was to evaluate the equine immune responses in an experimentally induced Sarcocystis neurona infection model. Neurologic parameters were recorded prior to and throughout the 70-day study by blinded investigators. Recombinant SnSAG1 ELISA for serum and CSF were used to confirm and track disease progression. All experimentally infected horses displayed neurologic signs after infection. Neutrophils, monocytes, and lymphocytes from infected horses displayed significantly delayed apoptosis at some time points. Cell proliferation was significantly increased in S. neurona-infected horses when stimulated nonspecifically with PMA/I but significantly decreased when stimulated with S. neurona compared to controls. Collectively, our results suggest that horses experimentally infected with S. neurona manifest impaired antigen specific response to S. neurona, which could be a function of altered antigen presentation, lack of antigen recognition, or both.
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Abstract
Equine protozoal myeloencephalitis (EPM) can be caused by either of 2 related protozoan parasites, Sarcocystis neurona and Neospora hughesi, although S. neurona is the most frequent etiologic pathogen. Horses are commonly infected, but clinical disease occurs infrequently; the factors influencing disease occurrence are not well understood. Risk factors for the development of EPM include the presence of opossums and prior stressful health-related events. Attempts to reproduce EPM experimentally have reliably induced antibody responses in challenged horses but have not consistently produced acute neurologic disease. Diagnosis and options for treatment of EPM have improved over the past decade.
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Affiliation(s)
- Daniel K Howe
- Department of Veterinary Science, M.H. Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA.
| | - Robert J MacKay
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, 2015 Southwest 16th Avenue, Room VH-136, PO Box 100136, Gainesville, FL 32610-0125, USA
| | - Stephen M Reed
- Department of Veterinary Science, M.H. Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA; Rood and Riddle Equine Hospital, PO Box 12070, Lexington, KY 40580, USA
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Olias P, Meyer A, Klopfleisch R, Lierz M, Kaspers B, Gruber AD. Modulation of the host Th1 immune response in pigeon protozoal encephalitis caused by Sarcocystis calchasi. Vet Res 2013; 44:10. [PMID: 23398807 PMCID: PMC3598538 DOI: 10.1186/1297-9716-44-10] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Accepted: 01/15/2013] [Indexed: 02/06/2023] Open
Abstract
Pigeon protozoal encephalitis (PPE) is an emerging central-nervous disease of domestic pigeons (Columba livia f. domestica) reported in Germany and the United States. It is caused by the apicomplexan parasite Sarcocystis calchasi which is transmitted by Accipter hawks. In contrast to other members of the Apicomplexa such as Toxoplasma and Plasmodium, the knowledge about the pathophysiology and host manipulation of Sarcocystis is scarce and almost nothing is known about PPE. Here we show by mRNA expression profiling a significant down-modulation of the interleukin (IL)-12/IL-18/interferon (IFN)-γ axis in the brains of experimentally infected pigeons during the schizogonic phase of disease. Concomitantly, no cellular immune response was observed in histopathology while immunohistochemistry and nested PCR detected S. calchasi. In contrast, in the late central-nervous phase, IFN-γ and tumor necrosis factor (TNF) α-related cytokines were significantly up-modulated, which correlated with a prominent MHC-II protein expression in areas of mononuclear cell infiltration and necrosis. The mononuclear cell fraction was mainly composed of T-lymphocytes, fewer macrophages and B-lymphocytes. Surprisingly, the severity and composition of the immune cell response appears unrelated to the infectious dose, although the severity and onset of the central nervous signs clearly was dose-dependent. We identified no or only very few tissue cysts by immunohistochemistry in pigeons with severe encephalitis of which one pigeon repeatedly remained negative by PCR despite severe lesions. Taken together, these observations may suggest an immune evasion strategy of S. calchasi during the early phase and a delayed-type hypersensitivity reaction as cause of the extensive cerebral lesions during the late neurological phase of disease.
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Affiliation(s)
- Philipp Olias
- Institute of Veterinary Pathology, Freie Universität Berlin, Robert-von-Ostertag-Str, 15, Berlin 14163, Germany.
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Witonsky SG, Ellison S, Yang J, Gogal RM, Lawler H, Suzuki Y, Sriranganathan N, Andrews F, Ward D, Lindsay DS. Horses experimentally infected with Sarcocystis neurona develop altered immune responses in vitro. J Parasitol 2009; 94:1047-54. [PMID: 18973416 DOI: 10.1645/ge-1441.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Accepted: 01/23/2008] [Indexed: 11/10/2022] Open
Abstract
Equine protozoal myeloencephalitis (EPM) due to Sarcocystis neurona infection is 1 of the most common neurologic diseases in horses in the United States. The mechanisms by which most horses resist disease, as well as the possible mechanisms by which the immune system may be suppressed in horses that develop EPM, are not known. Therefore, the objectives of this study were to determine whether horses experimentally infected with S. neurona developed suppressed immune responses. Thirteen horses that were negative for S. neurona antibodies in serum and cerebrospinal fluid (CSF) were randomly assigned to control (n = 5) or infected (n = 8) treatment groups. Neurologic exams and cerebrospinal fluid analyses were performed prior to, and following, S. neurona infection. Prior to, and at multiple time points following infection, immune parameters were determined. All 8 S. neurona-infected horses developed clinical signs consistent with EPM, and had S. neurona antibodies in the serum and CSF. Both infected and control horses had increased percentages (P < 0.05) of B cells at 28 days postinfection. Infected horses had significantly decreased (P < 0.05) proliferation responses as measured by thymidine incorporation to nonspecific mitogens phorbol myristate acetate (PMA) and ionomycin (I) as soon as 2 days postinfection.
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Affiliation(s)
- Sharon G Witonsky
- Department of Large Animal Clinical Sciences, Phase II, Duck Pond Dr., Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia 24061-0442, USA.
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Witonsky SG, Gogal RM, Duncan RB, Norton H, Ward D, Yang J, Lindsay DS. Humoral immunity is not critical for protection against experimental infection with Sarcocystis neurona in B-cell-deficient mice. J Parasitol 2006; 91:830-7. [PMID: 17089750 DOI: 10.1645/ge-488r.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Immunodeficient B-cell-deficient mice (mmuMT) were infected with Sarcocystis neurona merozoites to determine the role of B cells and the humoral immune response in protective immunity. As expected, the mice did not seroconvert based on a direct agglutination test. Infected mice did not have significant changes in gross pathology at the time points examined. Histologic changes included mild perivascular and peribronchial infiltrate in the lungs; perivascular infiltrate and mild inflammatory sinusoidal foci in the liver; prominent high endothelial venules in the lymph nodes; and moderate cellular expansion of the periarteriolar sheaths (PALS) in the spleen. Changes resolved by day 60 postinfection. Mice developed significant CD4 and CD8 responses in lymphoid organs, including significant effector (CD45RB(high)) and memory (CD44(high)) CD4 and CD8 responses. Flow cytometry confirmed the lack of B cells. Overall, these data suggest that B cells are not critical to the protective immune response to SN infection.
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Affiliation(s)
- Sharon G Witonsky
- Department of Large Animal Clinical Sciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, Virginia 24061, USA.
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Yang J, Ellison S, Gogal R, Norton H, Lindsay DS, Andrews F, Ward D, Witonsky S. Immune response to Sarcocystis neurona infection in naturally infected horses with equine protozoal myeloencephalitis. Vet Parasitol 2006; 138:200-10. [PMID: 16563631 DOI: 10.1016/j.vetpar.2006.02.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Revised: 01/30/2006] [Accepted: 02/07/2006] [Indexed: 11/21/2022]
Abstract
Equine protozoal myeloencephalitis (EPM) is one of the most common neurologic diseases of horses in the United States. The primary etiologic agent is Sarcocystis neurona. Currently, there is limited knowledge regarding the protective or pathophysiologic immune response to S. neurona infection or the subsequent development of EPM. The objectives of this study were to determine whether S. neurona infected horses with clinical signs of EPM had altered or suppressed immune responses compared to neurologically normal horses and if blood sample storage would influence these findings. Twenty clinically normal horses and 22 horses with EPM, diagnosed by the presence of S. neurona specific antibodies in the serum and/or cerebrospinal (CSF) and clinical signs, were evaluated for differences in the immune cell subsets and function. Our results demonstrated that naturally infected horses had significantly (P<0.05) higher percentages of CD4 T-lymphocytes and neutrophils (PMN) in separated peripheral blood leukocytes than clinically normal horses. Leukocytes from naturally infected EPM horses had significantly lower proliferation responses, as measured by thymidine incorporation, to a non-antigen specific mitogen than did clinically normal horses (P<0.05). Currently, studies are in progress to determine the role of CD4 T cells in disease and protection against S. neurona in horses, as well as to determine the mechanism associated with suppressed in vitro proliferation responses. Finally, overnight storage of blood samples appears to alter T lymphocyte phenotypes and viability among leukocytes.
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Affiliation(s)
- Jibing Yang
- Department of Large Animal Clinical Sciences, Phase II, Duck Pond Dr., Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, 24061, USA
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Mullaney T, Murphy AJ, Kiupel M, Bell JA, Rossano MG, Mansfield LS. Evidence to support horses as natural intermediate hosts for Sarcocystis neurona. Vet Parasitol 2005; 133:27-36. [PMID: 15970386 DOI: 10.1016/j.vetpar.2005.05.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2004] [Revised: 05/12/2005] [Accepted: 05/12/2005] [Indexed: 10/25/2022]
Abstract
Opossums (Didelphis spp.) are the definitive host for the protozoan parasite Sarcocystis neurona, the causative agent of equine protozoal myeloencephalitis (EPM). Opossums shed sporocysts in feces that can be ingested by true intermediate hosts (cats, raccoons, skunks, armadillos and sea otters). Horses acquire the parasite by ingestion of feed or water contaminated by opossum feces. However, horses have been classified as aberrant intermediate hosts because the terminal asexual sarcocyst stage that is required for transmission to the definitive host has not been found in their tissues despite extensive efforts to search for them [Dubey, J.P., Lindsay, D.S., Saville, W.J., Reed, S.M., Granstrom, D.E., Speer, C.A., 2001b. A review of Sarcocystis neurona and equine protozoal myeloencephalitis (EPM). Vet. Parasitol. 95, 89-131]. In a 4-month-old filly with neurological disease consistent with EPM, we demonstrate schizonts in the brain and spinal cord and mature sarcocysts in the tongue and skeletal muscle, both with genetic and morphological characteristics of S. neurona. The histological and electron microscopic morphology of the schizonts and sarcocysts were identical to published features of S. neurona [Stanek, J.F., Dubey, J.P., Oglesbee, M.J., Reed, S.M., Lindsay, D.S., Capitini, L.A., Njoku, C.J., Vittitow, K.L., Saville, W.J., 2002. Life cycle of Sarcocystis neurona in its natural intermediate host, the raccoon, Procyon lotor. J. Parasitol. 88, 1151-1158]. DNA from schizonts and sarcocysts from this horse produced Sarcocystis specific 334bp PCR products [Tanhauser, S.M., Yowell, C.A., Cutler, T.J., Greiner, E.C., MacKay, R.J., Dame, J.B., 1999. Multiple DNA markers differentiate Sarcocystis neurona and Sarcocystis falcatula. J. Parasitol. 85, 221-228]. Restriction fragment length polymorphism (RFLP) analysis of these PCR products showed banding patterns characteristic of S. neurona. Sequencing, alignment and comparison of both schizont and sarcocyst DNA amplicons showed 100% identity. Although Koch's postulates have not been demonstrated in this case study, the finding of mature, intact S. neurona schizonts and sarcocysts in the tissues of this single horse strongly suggests that horses have the potential to act as intermediate hosts. Further studies are needed to demonstrate Koch's postulates with repeated transfer of S. neurona between opossums and horses.
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Affiliation(s)
- Thomas Mullaney
- Diagnostic Center for Population and Animal Health (DCPAH), College of Veterinary Medicine, Michigan State University (MSU), East Lansing, MI 48824, USA
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Sellon DC, Knowles DP, Greiner EC, Long MT, Hines MT, Hochstatter T, Tibary A, Dame JB. Infection of immunodeficient horses with Sarcocystis neurona does not result in neurologic disease. CLINICAL AND DIAGNOSTIC LABORATORY IMMUNOLOGY 2005; 11:1134-9. [PMID: 15539518 PMCID: PMC524751 DOI: 10.1128/cdli.11.6.1134-1139.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Equine protozoal myeloencephalitis is a progressive neurologic disease of horses most commonly caused by infection with the apicomplexan parasite Sarcocystis neurona. Factors affecting neuroinvasion and neurovirulence have not been determined. We investigated the pathogenesis of infection with S. neurona in horses with severe combined immune deficiency (SCID). Two immunocompetent (IC) Arabian horses and two Arabian horses with SCID were infected orally with 5 x 10(5) sporocysts of S. neurona. Four IC horses and one SCID horse were infected intravenously (i.v.) with 5 x 10(8) merozoites of the WSU-1 isolate of S. neurona. Despite prolonged parasitemia and persistent infection of visceral tissues (skeletal muscle, cardiac muscle, lung, liver, and spleen) as demonstrated by PCR and culture, SCID horses did not develop neurologic signs after oral or i.v. infection. S. neurona was undetectable in the neuronal tissues of SCID horses by either PCR, immunohistochemistry, or culture. In contrast, although parasitemia was undetectable in orally infected IC horses and of only short duration in i.v. infected IC horses, four of six IC horses developed neurologic signs. S. neurona was detectable by PCR and/or culture of neural tissue but not visceral tissue of IC horses with neurologic disease. Infected SCID horses are unable to clear S. neurona from visceral tissues, but the infection does not result in neurologic signs; in contrast, IC horses rapidly control parasitemia and infection of visceral tissues but frequently experience neuroinvasion and exhibit clinical signs of neurologic disease.
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Affiliation(s)
- Debra C Sellon
- Department of Veterinary Clinical Sciences, Washington State University, Pullman, WA 99163, USA.
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