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In situ ultrastructures of two evolutionarily distant apicomplexan rhoptry secretion systems. Nat Commun 2021; 12:4983. [PMID: 34404783 PMCID: PMC8371170 DOI: 10.1038/s41467-021-25309-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 08/03/2021] [Indexed: 12/03/2022] Open
Abstract
Parasites of the phylum Apicomplexa cause important diseases including malaria, cryptosporidiosis and toxoplasmosis. These intracellular pathogens inject the contents of an essential organelle, the rhoptry, into host cells to facilitate invasion and infection. However, the structure and mechanism of this eukaryotic secretion system remain elusive. Here, using cryo-electron tomography and subtomogram averaging, we report the conserved architecture of the rhoptry secretion system in the invasive stages of two evolutionarily distant apicomplexans, Cryptosporidium parvum and Toxoplasma gondii. In both species, we identify helical filaments, which appear to shape and compartmentalize the rhoptries, and an apical vesicle (AV), which facilitates docking of the rhoptry tip at the parasite’s apical region with the help of an elaborate ultrastructure named the rhoptry secretory apparatus (RSA); the RSA anchors the AV at the parasite plasma membrane. Depletion of T. gondii Nd9, a protein required for rhoptry secretion, disrupts the RSA ultrastructure and AV-anchoring. Moreover, T. gondii contains a line of AV-like vesicles, which interact with a pair of microtubules and accumulate towards the AV, leading to a working model for AV-reloading and discharging of multiple rhoptries. Together, our analyses provide an ultrastructural framework to understand how these important parasites deliver effectors into host cells. The rhoptry is an apical secretory organelle of apicomplexan parasites that is essential for host cell invasion. Here, Mageswaran et al. provide in situ ultrastructures of rhoptries from two pathogens, revealing a conserved architecture including luminal filaments and a distinct docking mechanism.
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Ammar SI, Watson AM, Craig LE, Cope ER, Schaefer JJ, Mulliniks JT, Gerhold RW. Eimeria gilruthi-associated abomasitis in a group of ewes. J Vet Diagn Invest 2018; 31:128-132. [PMID: 30453850 DOI: 10.1177/1040638718814109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Nine of 23 (39%) research ewes with severe diarrhea and weight loss had histologic lesions consistent with Eimeria gilruthi infection in their abomasa. Gross anatomic lesions included hundreds of opaque 1-mm nodules in abomasal mucosa that corresponded microscopically to 200-300 µm diameter organisms surrounded by areas of necrosis. Analysis of fecal samples from 4 ewes demonstrated oocysts from typical ovine Eimeria species, none of which were E. gilruthi. Two separate PCR reactions were performed on abomasal tissue from 4 sheep to amplify the 18S ribosomal DNA (rDNA) and internal transcribed spacer (ITS) region of the rDNA, respectively. The resultant 18S rDNA nucleotide sequences shared 99% homology with multiple Eimeria species in GenBank. The ITS region shared 77% homology with E. ellipsoidalis in GenBank. Further studies are needed to understand the life cycle and pathogenicity of E. gilruthi. Our results underscore the inclusion of E. gilruthi in the differential diagnosis of diarrhea and weight loss in sheep.
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Affiliation(s)
- Sawsan I Ammar
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine (Gerhold, Ammar, Watson, Craig, Schaefer), University of Tennessee, Knoxville, TN.,Department of Animal Science (Cope), University of Tennessee, Knoxville, TN.,West Central Research and Extension Center, University of Nebraska, North Platte, NE (Mulliniks).,Clinical Pathology Department, College of Veterinary Medicine, Sadat City University, Sadat City, Menofia, Egypt (Ammar)
| | - Allison M Watson
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine (Gerhold, Ammar, Watson, Craig, Schaefer), University of Tennessee, Knoxville, TN.,Department of Animal Science (Cope), University of Tennessee, Knoxville, TN.,West Central Research and Extension Center, University of Nebraska, North Platte, NE (Mulliniks).,Clinical Pathology Department, College of Veterinary Medicine, Sadat City University, Sadat City, Menofia, Egypt (Ammar)
| | - Linden E Craig
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine (Gerhold, Ammar, Watson, Craig, Schaefer), University of Tennessee, Knoxville, TN.,Department of Animal Science (Cope), University of Tennessee, Knoxville, TN.,West Central Research and Extension Center, University of Nebraska, North Platte, NE (Mulliniks).,Clinical Pathology Department, College of Veterinary Medicine, Sadat City University, Sadat City, Menofia, Egypt (Ammar)
| | - Emily R Cope
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine (Gerhold, Ammar, Watson, Craig, Schaefer), University of Tennessee, Knoxville, TN.,Department of Animal Science (Cope), University of Tennessee, Knoxville, TN.,West Central Research and Extension Center, University of Nebraska, North Platte, NE (Mulliniks).,Clinical Pathology Department, College of Veterinary Medicine, Sadat City University, Sadat City, Menofia, Egypt (Ammar)
| | - John J Schaefer
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine (Gerhold, Ammar, Watson, Craig, Schaefer), University of Tennessee, Knoxville, TN.,Department of Animal Science (Cope), University of Tennessee, Knoxville, TN.,West Central Research and Extension Center, University of Nebraska, North Platte, NE (Mulliniks).,Clinical Pathology Department, College of Veterinary Medicine, Sadat City University, Sadat City, Menofia, Egypt (Ammar)
| | - J Travis Mulliniks
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine (Gerhold, Ammar, Watson, Craig, Schaefer), University of Tennessee, Knoxville, TN.,Department of Animal Science (Cope), University of Tennessee, Knoxville, TN.,West Central Research and Extension Center, University of Nebraska, North Platte, NE (Mulliniks).,Clinical Pathology Department, College of Veterinary Medicine, Sadat City University, Sadat City, Menofia, Egypt (Ammar)
| | - Richard W Gerhold
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine (Gerhold, Ammar, Watson, Craig, Schaefer), University of Tennessee, Knoxville, TN.,Department of Animal Science (Cope), University of Tennessee, Knoxville, TN.,West Central Research and Extension Center, University of Nebraska, North Platte, NE (Mulliniks).,Clinical Pathology Department, College of Veterinary Medicine, Sadat City University, Sadat City, Menofia, Egypt (Ammar)
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Morgan KJ, Alley MR, Pomroy WE, Castro I, Howe L. Enteric coccidiosis in the brown kiwi (Apteryx mantelli). Parasitol Res 2012; 111:1689-99. [PMID: 22837099 DOI: 10.1007/s00436-012-3008-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 06/11/2012] [Indexed: 12/01/2022]
Abstract
Enteric coccidiosis may cause significant morbidity and mortality in juvenile brown kiwi (Apteryx mantelli). Morphology of sporulated oocysts indicates that at least two Eimeria species are able to infect the brown kiwi. A histological study of the endogenous stages of coccidia was undertaken in the intestinal tracts of ten naturally infected young kiwi. Sequential sectioning of the entire intestinal tract allowed identification and recording of the distribution of the various coccidial life stages. Macromeronts measuring 268 × 162 μm when mature were found mainly within the lamina propria of the proximal one third of the small intestine. A smaller form of lamina propria meront was also identified (8.7 × 6.4 μm) with a similar distribution to the macromeronts. Small meronts (4.4 × 3.8 μm) were also identified in mucosal epithelial cells, with the overall peak in distribution within the intestinal tract being distal to the lamina propria meronts. Three morphologically distinctive gametocytes were identified. Type A gametocytes contained within epithelial cells shared the same distribution as the epithelial meronts. Polyps containing large numbers of type B gametocytes within the distal intestinal tract were found in two cases, and type C gametocytes were identified throughout the entire intestinal tract in one case only. The observational nature of this study precludes complete knowledge of the parasite life cycles using histology alone. However, it is likely that each of the three morphologically distinct gametocytes represents a separate species of enteric coccidia.
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Affiliation(s)
- K J Morgan
- Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
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