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Towards the First Multiepitope Vaccine Candidate against Neospora caninum in Mouse Model: Immunoinformatic Standpoint. BIOMED RESEARCH INTERNATIONAL 2022; 2022:2644667. [PMID: 35722460 PMCID: PMC9204498 DOI: 10.1155/2022/2644667] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 05/09/2022] [Indexed: 11/28/2022]
Abstract
Neospora caninum is an economically significant parasite among livestock, particularly in dairy cattle herds, causing storm abortions. Vaccination seems necessary to limit the infection and its harsh consequences. This is the first steps towards developing a multiepitope vaccine candidate against N. caninum using in silico approaches. High-ranked mouse MHC-binding and shared linear B-cell epitopes from six proteins (SRS2, MIC3, MIC6, GRA1, IMP-1, and profilin) as well as IFN-γ-inducing epitopes (from SAG1) were predicted, screened, and connected together through appropriate linkers. Finally, RS-09 protein (TLR4 agonist) and histidine tag were added to N- and C-terminal of the vaccine sequence, yielding 486 residues in length. Physicochemical properties showed a stable (instability index: 27.23), highly soluble, antigenic (VaxiJen score: 0.9554), and nonallergenic candidate. Secondary structure of the multiepitope protein included 58.85% random coil, 20.99% extended strand, and 20.16% alpha helix. Also, the tertiary structure was predicted, and further analyses validated a stable interaction between the vaccine model and mouse TLR4 (binding score: -1261.6). Virtual simulation of immune profile demonstrated potently stimulated humoral (IgG+IgM) and cell-mediated (IFN-γ) responses upon multiepitope vaccine injection. Altogether, a potentially immunogenic vaccine candidate was developed using several N. caninum proteins, with the capability to elicit IFN-γ upsurge and other components of cellular immunity, and can be used in prophylactic purposes against neosporosis.
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Determination of B and T Cell Epitopes in Neospora caninum Immune Mapped Protein-1 (IMP-1): Implications in Vaccine Design against Neosporosis. BIOMED RESEARCH INTERNATIONAL 2022; 2022:2508050. [PMID: 35434130 PMCID: PMC9010208 DOI: 10.1155/2022/2508050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 01/15/2022] [Accepted: 03/10/2022] [Indexed: 02/05/2023]
Abstract
Prevention of neosporosis is advantageous for cattle health and productivity. Previously, several vaccine candidates were nominated for vaccination against Neospora caninum. This study was premised on in silico evaluation of N. caninum IMP-1 in order to determine its physicochemical features and immunogenic epitopes. We employed a wide array of network-based tools for the prediction of antigenicity, allergenicity, solubility, posttranslational modification (PTM) sites, physicochemical properties, transmembrane domains and signal peptide, secondary and tertiary structures, and intrinsically disordered regions. Also, prediction and screening of potential continuous B cell peptides and those epitopes having stringent affinity to couple with mouse major histocompatibility complex (MHC) and cytotoxic T lymphocyte (CTL) receptors were accomplished. The protein had 393 residues with a molecular weight of 42.71 kDa, representing aliphatic index of 85.83 (thermotolerant) and GRAVY score of -0.447 (hydrophilic). There were 47 PTM sites without a signal peptide in the sequence. Secondary structure comprised mostly of extended strand and helices, followed by coils. The Ramachandran plot of the refined model showed 90.1%, 9.9%, 0.0%, and 0.0% residues in the favored, additional allowed, generously allowed, and disallowed regions, correspondingly. Additionally, various potential B cell (linear and conformational), CTL, and MHC binding epitopes were predicted for N. caninum IMP-1. The findings of the present study could be further directed for next-generation vaccine design against neosporosis.
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Neospora caninum SRS2 Protein: Essential Vaccination Targets and Biochemical Features for Next-Generation Vaccine Design. BIOMED RESEARCH INTERNATIONAL 2022; 2022:7070144. [PMID: 35434127 PMCID: PMC9007667 DOI: 10.1155/2022/7070144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 03/23/2022] [Indexed: 11/17/2022]
Abstract
Vaccination is a standout preventive measure to combat neosporosis among cattle herds. The present in silico study was done to evaluate the physicochemical properties and potent immunogenic epitopes of N. caninum SRS2 protein as a possible vaccine candidate. Web-based tools were used to predict physicochemical properties, antigenicity, allergenicity, solubility, posttranslational modification (PTM) sites, transmembrane domains and signal peptide, and secondary and tertiary structures as well as intrinsically disordered regions, followed by identification and screening of potential linear and conformational B-cell epitopes and those peptides having affinity to bind mouse major histocompatibility complex (MHC) and cytotoxic T lymphocyte (CTL). The protein had 401 residues with a molecular weight of 42 kDa, representing aliphatic index of 69.35 (thermotolerant) and GRAVY score of -0.294 (hydrophilic). There were 53 PTM sites without a signal peptide in the sequence. Secondary structure comprised mostly by extended strand, followed by helices and coils. The Ramachandran plot of the refined model showed 90.2%, 8.8%, 0.5%, and 0.5% residues in the favored, additional allowed, generously allowed, and disallowed regions, correspondingly. Additionally, various potential B-cell (linear and conformational), CTL, and MHC-binding epitopes were predicted for N. caninum SRS2. These epitopes could be further utilized in the multiepitope vaccine constructs directed against neosporosis.
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Das M, Hasan M, Akter S, Roy S, Sharma B, Chowdhury MSR, Ahsan MI, Akhand RN, Uddin MB, Ahmed SSU. In Silico Investigation of Conserved miRNAs and Their Targets From the Expressed Sequence Tags in Neospora Caninum Genome. Bioinform Biol Insights 2021; 15:11779322211046729. [PMID: 34898982 PMCID: PMC8655437 DOI: 10.1177/11779322211046729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 08/20/2021] [Indexed: 12/02/2022] Open
Abstract
Neospora caninum is a protozoan parasite, the etiologic agent of Neosporosis—a common cause of abortion in cattle worldwide. Herd level prevalence of Neosporosis could be as high as 90%. However, there is no approved treatment and vaccines available for Neosporosis. MicroRNA (miRNA) based prophylaxis and therapeutics could be options for Neosporosis in cattle and other animals. The current study aimed to investigate the genome of Neospora caninum to identify and characterize the conserved miRNAs through Expressed Sequence Tags (ESTs) dependent homology search. A total of 1,041 mature miRNAs of reference organisms were employed against 336 non-redundant ESTs available in the genome of Neospora caninum. The study predicted one putative miRNA “nca-miR-9388-5p” of 19 nucleotides with MFEI value -1.51 kcal/mol and (A + U) content% 72.94% corresponding with its pre-miRNA. A comprehensive search for specific gene targets was performed and discovered 16 potential genes associated with different protozoal physiological functions. Significantly, the gene “Protein phosphatase” was found responsible for the virulence of Neospora caninum. The other genes were accounted for gene expression, vesicular transport, cell signaling, cell proliferation, DNA repair mechanism, and different developmental stages of the protozoon. Therefore, this study finding will provide pivotal information to future aspirants upon Bovine Neosporosis. It will also serve as the baseline information for further studies of the bioinformatics approach to identify other protozoal miRNAs.
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Affiliation(s)
- Moumita Das
- Department of Epidemiology and Public Health, Sylhet Agricultural University, Sylhet, Bangladesh
| | - Mahmudul Hasan
- Department of Pharmaceuticals and Industrial Biotechnology, Sylhet Agricultural University, Sylhet, Bangladesh
| | - Sharmin Akter
- Department of Epidemiology and Public Health, Sylhet Agricultural University, Sylhet, Bangladesh
| | - Sawrab Roy
- Department of Microbiology and Immunology, Sylhet Agricultural University, Sylhet, Bangladesh
| | - Binayok Sharma
- Department of Medicine, Sylhet Agricultural University, Sylhet, Bangladesh
| | | | - Md Irtija Ahsan
- Department of Epidemiology and Public Health, Sylhet Agricultural University, Sylhet, Bangladesh
| | - Rubaiat Nazneen Akhand
- Department of Biochemistry and Chemistry, Sylhet Agricultural University, Sylhet, Bangladesh
| | - Md Bashir Uddin
- Department of Medicine, Sylhet Agricultural University, Sylhet, Bangladesh
| | - Syed Sayeem Uddin Ahmed
- Department of Epidemiology and Public Health, Sylhet Agricultural University, Sylhet, Bangladesh
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Shedding light on biochemical features and potential immunogenic epitopes of Neospora caninum SAG1: In silico study. INFORMATICS IN MEDICINE UNLOCKED 2021. [DOI: 10.1016/j.imu.2021.100785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Meixner N, Sommer MF, Scuda N, Matiasek K, Müller M. Comparative aspects of laboratory testing for the detection of Toxoplasma gondii and its differentiation from Neospora caninum as the etiologic agent of ovine abortion. J Vet Diagn Invest 2020; 32:898-907. [PMID: 33025842 DOI: 10.1177/1040638720962110] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Histologic examination of aborted material is an essential component in the diagnosis of ovine toxoplasmosis. However, the detection of Toxoplasma gondii in histologic sections, and its differentiation from the closely related protozoan Neospora caninum, is challenging. We developed a chromogenic in situ hybridization (ISH) assay for the identification of T. gondii in paraffin-embedded tissue samples. We examined retrospectively the archived placental tissue of 200 sheep abortion submissions for the presence of T. gondii by immunohistochemistry (IHC), ISH, and real-time PCR (rtPCR). All placental samples that tested positive for T. gondii by rtPCR (9 of 200) were also positive by IHC, with inconclusive IHC staining in an additional 7 rtPCR-negative cases. Further testing for N. caninum of all 200 placentas by rtPCR revealed 7 Neospora-positive cases. T. gondii ISH was positive in 4 of 9 IHC-positive samples and 1 of the 7 N. caninum rtPCR-positive samples. Real-time PCR was used as the reference standard for specificity and sensitivity calculations regarding placenta samples. Specificity of ISH and IHC was 99% and 96-100%, respectively. The sensitivity of ISH (44%) was quite low compared to IHC (100%). The exclusive use of ISH for the detection of T. gondii, and thus for the diagnosis of ovine toxoplasmosis, was not acceptable. However, combined with rtPCR, both ISH and IHC can be useful detection methods to improve histologic evaluation by visualizing the parasite within tissue sections.
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Affiliation(s)
- Nicola Meixner
- Bavarian Health and Food Safety Authority, Erlangen, Germany
| | - Marie F Sommer
- Bavarian Health and Food Safety Authority, Erlangen, Germany
| | - Nelly Scuda
- Bavarian Health and Food Safety Authority, Erlangen, Germany
| | - Kaspar Matiasek
- Section of Clinical and Comparative Neuropathology, Institute of Veterinary Pathology, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-Universität, Munich, Germany
| | - Matthias Müller
- Bavarian Health and Food Safety Authority, Erlangen, Germany
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Salehi N, Gottstein B, Haddadzadeh HR. Genetic diversity of bovine Neospora caninum determined by microsatellite markers. Parasitol Int 2015; 64:357-61. [PMID: 25988829 DOI: 10.1016/j.parint.2015.05.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 05/07/2015] [Accepted: 05/10/2015] [Indexed: 11/18/2022]
Abstract
Neospora caninum is one of the most significant parasitic organisms causing bovine abortion worldwide. Despite the economic impact of this infection, relatively little is known about the genetic diversity of this parasite. In this study, using Nc5 and ITS1 nested PCR, N. caninum has been detected in 12 brain samples of aborted fetuses from 298 seropositive dairy cattle collected from four different regions in Tehran, Iran. These specimen (Nc-Iran) were genotyped in multilocus using 9 different microsatellite markers previously described (MS4, MS5, MS6A, MS6B, MS7, MS8, MS10, MS12 and MS21). Microsatellite amplification was completely feasible in 2 samples, semi-completely in 8 samples, and failed in 2 samples. Within the two completely performed allelic profiles of Nc-Iran strains, unique multilocus profiles were obtained for both and novel allelic patterns were found in the MS8 and MS10 microsatellite markers. The Jaccard's similarity index showed significant difference between these two strains and from other standard isolates derived from GenBank such as Nc-Liv, Nc-SweB1, Nc-GER1, KBA1, and KBA2. All samples originating from the same area showed identical allelic numbers and a correlation between the number of repeats and geographic districts was observed.
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Affiliation(s)
- N Salehi
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI, United States.
| | - B Gottstein
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - H R Haddadzadeh
- Department of Parasitology, Veterinary Medicine Faculty, University of Tehran, Tehran, Iran
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Goodswen SJ, Barratt JLN, Kennedy PJ, Ellis JT. Improving the gene structure annotation of the apicomplexan parasite Neospora caninum fulfils a vital requirement towards an in silico-derived vaccine. Int J Parasitol 2015; 45:305-18. [PMID: 25747726 DOI: 10.1016/j.ijpara.2015.01.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 01/12/2015] [Accepted: 01/12/2015] [Indexed: 12/16/2022]
Abstract
Neospora caninum is an apicomplexan parasite which can cause abortion in cattle, instigating major economic burden. Vaccination has been proposed as the most cost-effective control measure to alleviate this burden. Consequently the overriding aspiration for N. caninum research is the identification and subsequent evaluation of vaccine candidates in animal models. To save time, cost and effort, it is now feasible to use an in silico approach for vaccine candidate prediction. Precise protein sequences, derived from the correct open reading frame, are paramount and arguably the most important factor determining the success or failure of this approach. The challenge is that publicly available N. caninum sequences are mostly derived from gene predictions. Annotated inaccuracies can lead to erroneously predicted vaccine candidates by bioinformatics programs. This study evaluates the current N. caninum annotation for potential inaccuracies. Comparisons with annotation from a closely related pathogen, Toxoplasma gondii, are also made to distinguish patterns of inconsistency. More importantly, a mRNA sequencing (RNA-Seq) experiment is used to validate the annotation. Potential discrepancies originating from a questionable start codon context and exon boundaries were identified in 1943 protein coding sequences. We conclude, where experimental data were available, that the majority of N. caninum gene sequences were reliably predicted. Nevertheless, almost 28% of genes were identified as questionable. Given the limitations of RNA-Seq, the intention of this study was not to replace the existing annotation but to support or oppose particular aspects of it. Ideally, many studies aimed at improving the annotation are required to build a consensus. We believe this study, in providing a new resource on gene structure and annotation, is a worthy contributor to this endeavour.
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Affiliation(s)
- Stephen J Goodswen
- School of Medical and Molecular Sciences, University of Technology Sydney (UTS), 15 Broadway, Ultimo, NSW 2007, Australia.
| | - Joel L N Barratt
- School of Medical and Molecular Sciences, University of Technology Sydney (UTS), 15 Broadway, Ultimo, NSW 2007, Australia
| | - Paul J Kennedy
- School of Software, Faculty of Engineering and Information Technology and the Centre for Quantum Computation and Intelligent Systems at the University of Technology Sydney (UTS), 15 Broadway, Ultimo, NSW 2007, Australia
| | - John T Ellis
- School of Medical and Molecular Sciences, University of Technology Sydney (UTS), 15 Broadway, Ultimo, NSW 2007, Australia
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Monney T, Hemphill A. Vaccines against neosporosis: what can we learn from the past studies? Exp Parasitol 2014; 140:52-70. [PMID: 24602874 DOI: 10.1016/j.exppara.2014.02.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 02/09/2014] [Accepted: 02/18/2014] [Indexed: 10/25/2022]
Abstract
Neospora caninum is an intracellular apicomplexan parasite, which is a leading cause of abortion in cattle; thus neosporosis represents an important veterinary health problem and is of high economic significance. The parasite can infect cattle via trans-placental transmission from an infected cow to its fetus (vertical transmission), or through the oral route via ingestion of food or water contaminated with oocysts that were previously shed with the feces of a canid definitive host (horizontal transmission). Although vaccination was considered a rational strategy to prevent bovine neosporosis, the only commercialized vaccine (Neoguard®) produced ambiguous results with relatively low efficacy, and was recently removed from the market. Therefore, there is a need to develop an efficient vaccine capable of preventing both, the horizontal transmission through infected food or water to a naïve animal as well as the vertical transmission from infected but clinically asymptomatic dams to the fetus. Different vaccine strategies have been investigated, including the use of live attenuated vaccines, killed parasite lysates, total antigens or antigen fractions from killed parasites, and subunit vaccines. The vast majority of experimental studies were performed in mice, and to a certain extent in gerbils, but there is also a large number of investigations that were conducted in cattle and sheep. However, it is difficult to directly compare these studies due to the high variability of the parameters employed. In this review, we will summarize the recent advances made in vaccine development against N. caninum in cattle and in mice and highlight the most important factors, which are likely to influence the degree of protection mediated by vaccination.
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Affiliation(s)
- Thierry Monney
- Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland
| | - Andrew Hemphill
- Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland.
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He P, Li J, Gong P, Liu C, Zhang G, Yang J, Tuo W, Yang B, Zhang X. Neospora caninum surface antigen (p40) is a potential diagnostic marker for cattle neosporosis. Parasitol Res 2013; 112:2117-20. [PMID: 23435920 DOI: 10.1007/s00436-013-3309-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 01/18/2013] [Indexed: 10/27/2022]
Abstract
Neospora caninum is an intracellular protozoan that infects domestic and wild canids as well as many warm-blooded animals as shown by the isolation of viable parasites. The effectiveness of diagnostic tests for detecting specific antibodies against N. caninum is hampered by potential cross-reaction with other Coccidia. So, there is currently an urgent need for a sensitive and specific diagnostic assay for detecting N. caninum in animals. The N. caninum 40-kD surface antigen (p40), similar to NcSAG1 and NcSRS2, was shown to belong to surface antigen super family and thus represents an excellent marker for the diagnosis of neosporosis. In order to test the hypothesis, recombinant Ncp40 (rNcp40) was expressed in Escherichia coli, and an indirect ELISA test was developed using recombinant NCp40 antigen for N. caninum serodiagnosis. The antigen used in this study did not have cross-reactivity with anti-Toxoplasma gondii serum. Anti-p40 antibodies were detected by ELISA in the sera of Yellow cattle and were compared with (IFAT). Optimal sensitivity and specificity (98.2 and 98.6 %) were identified by IFAT. Additionally, 37 positive sera of T. gondii were detected and there was no significant difference with the negative serum of N. caninum. The rNcp40 ELISA developed here provides a specific and sensitive assay for detecting neosporosis in cattle.
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Affiliation(s)
- Pengfei He
- College of Animal Science and Veterinary Medicine, Jilin University, 5333 Xian Road, Changchun, 130062, People's Republic of China
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A review of the infection, genetics, and evolution of Neospora caninum: from the past to the present. INFECTION GENETICS AND EVOLUTION 2012; 13:133-50. [PMID: 22985682 DOI: 10.1016/j.meegid.2012.08.012] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 08/05/2012] [Accepted: 08/07/2012] [Indexed: 12/30/2022]
Abstract
This paper is a review of current knowledge on Neospora caninum in the context of other apicomplexan parasites and with an emphasis on: life cycle, disease, epidemiology, immunity, control and treatment, evolution, genomes, and biological databases and web resources. N. caninum is an obligate, intracellular, coccidian, protozoan parasite of the phylum Apicomplexa. Infection can cause the clinical disease neosporosis, which most notably is associated with abortion in cattle. These abortions are a major root cause of economic loss to both the dairy and beef industries worldwide. N. caninum has been detected in every country in which a study has been specifically conducted to detect this parasite in cattle. The major mode of transmission in cattle is transplacental (or vertical) transmission and several elements of the N. caninum life cycle are yet to be studied in detail. The outcome of an infection is inextricably linked to the precise timing of the infection coupled with the status of the immune system of the dam and foetus. There is no community consensus as to whether it is the dam's pro-inflammatory cytotoxic response to tachyzoites that kills the foetus or the tachyzoites themselves. From economic analysis the most cost-effective approach to control neosporosis is a vaccine. The perfect vaccine would protect against both infection and the clinical disease, and this implies a vaccine is needed that can induce a non-foetopathic cell mediated immunity response. Researchers are beginning to capitalise on the vast potential of -omics data (e.g. genomes, transcriptomes, and proteomes) to further our understanding of pathogens but especially to identify vaccine and drug targets. The recent publication of a genome for N. caninum offers vast opportunities in these areas.
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Reid AJ, Vermont SJ, Cotton JA, Harris D, Hill-Cawthorne GA, Könen-Waisman S, Latham SM, Mourier T, Norton R, Quail MA, Sanders M, Shanmugam D, Sohal A, Wasmuth JD, Brunk B, Grigg ME, Howard JC, Parkinson J, Roos DS, Trees AJ, Berriman M, Pain A, Wastling JM. Comparative genomics of the apicomplexan parasites Toxoplasma gondii and Neospora caninum: Coccidia differing in host range and transmission strategy. PLoS Pathog 2012; 8:e1002567. [PMID: 22457617 PMCID: PMC3310773 DOI: 10.1371/journal.ppat.1002567] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 01/23/2012] [Indexed: 11/18/2022] Open
Abstract
Toxoplasma gondii is a zoonotic protozoan parasite which infects nearly one third of the human population and is found in an extraordinary range of vertebrate hosts. Its epidemiology depends heavily on horizontal transmission, especially between rodents and its definitive host, the cat. Neospora caninum is a recently discovered close relative of Toxoplasma, whose definitive host is the dog. Both species are tissue-dwelling Coccidia and members of the phylum Apicomplexa; they share many common features, but Neospora neither infects humans nor shares the same wide host range as Toxoplasma, rather it shows a striking preference for highly efficient vertical transmission in cattle. These species therefore provide a remarkable opportunity to investigate mechanisms of host restriction, transmission strategies, virulence and zoonotic potential. We sequenced the genome of N. caninum and transcriptomes of the invasive stage of both species, undertaking an extensive comparative genomics and transcriptomics analysis. We estimate that these organisms diverged from their common ancestor around 28 million years ago and find that both genomes and gene expression are remarkably conserved. However, in N. caninum we identified an unexpected expansion of surface antigen gene families and the divergence of secreted virulence factors, including rhoptry kinases. Specifically we show that the rhoptry kinase ROP18 is pseudogenised in N. caninum and that, as a possible consequence, Neospora is unable to phosphorylate host immunity-related GTPases, as Toxoplasma does. This defense strategy is thought to be key to virulence in Toxoplasma. We conclude that the ecological niches occupied by these species are influenced by a relatively small number of gene products which operate at the host-parasite interface and that the dominance of vertical transmission in N. caninum may be associated with the evolution of reduced virulence in this species.
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Affiliation(s)
- Adam James Reid
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Sarah J. Vermont
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - James A. Cotton
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - David Harris
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | | | | | - Sophia M. Latham
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - Tobias Mourier
- Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
| | - Rebecca Norton
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - Michael A. Quail
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Mandy Sanders
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Dhanasekaran Shanmugam
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Amandeep Sohal
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - James D. Wasmuth
- Program in Molecular Structure and Function, Hospital for Sick Children and Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Laboratory of Parasitic Diseases, National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, Maryland, United States of America
| | - Brian Brunk
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Michael E. Grigg
- Laboratory of Parasitic Diseases, National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIAID), Bethesda, Maryland, United States of America
| | - Jonathan C. Howard
- Institute for Genetics, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - John Parkinson
- Program in Molecular Structure and Function, Hospital for Sick Children and Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - David S. Roos
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alexander J. Trees
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
| | - Matthew Berriman
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
| | - Arnab Pain
- Wellcome Trust Sanger Institute, Hinxton, Cambridgshire, United Kingdom
- King Abdullah University of Science and Technology, Thuwal, Jeddah, Kingdom of Saudi Arabia
- * E-mail: (AP); (JMW)
| | - Jonathan M. Wastling
- Institute of Infection and Global Health and School of Veterinary Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, Merseyside, United Kingdom
- * E-mail: (AP); (JMW)
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Identification of the cross-reactive and species-specific antigens between Neospora caninum and Toxoplasma gondii tachyzoites by a proteomics approach. Parasitol Res 2011; 109:899-911. [PMID: 21461729 DOI: 10.1007/s00436-011-2332-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 03/03/2011] [Indexed: 10/18/2022]
Abstract
The characterization of the cross-reactive and species-specific antigens of Neospora caninum and Toxoplasma gondii is important in the exploration to determine the common mechanisms of parasite-host interaction and to improve the serological diagnosis; it is also useful for the selection of the cross-reactive antigens that could be used in the development of vaccines or drugs for controlling the diseases caused by these two parasites. In this study, cross-reactive and species-specific antigens between N. caninum and T. gondii tachyzoites were comprehensively investigated using a proteomics approach with the application of two-dimensional gel electrophoresis, immunoblot analysis, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS), and MALDI-TOF/TOF-MS analysis. Immunoblotting and mass spectrometry analysis revealed that at least 42 individual protein spots of N. caninum were reacted with the anti-N. caninum serum, among which at least 18 protein spots were cross-reacted with the anti-T. gondii serum. Moreover, at least 31 protein spots of T. gondii were reacted with the anti-T. gondii serum, among which at least 19 protein spots were cross-reacted with the anti-N. caninum serum. Furthermore, some new specific proteins were also identified in the N. caninum protein profile by searching Toxoplasma sequences or sequences from other organisms. This study substantiates the usefulness of proteomics in the immunoscreening of the cross-reactive or species-specific antigens of both parasites. In addition, the present study showed that there was significant homology in the antigenic proteome profiles between the two parasites. These observations have implications for the design of multicomponent common vaccines against both parasite infections.
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Zhang G, Huang X, Boldbaatar D, Battur B, Battsetseg B, Zhang H, Yu L, Li Y, Luo Y, Cao S, Goo YK, Yamagishi J, Zhou J, Zhang S, Suzuki H, Igarashi I, Mikami T, Nishikawa Y, Xuan X. Construction of Neospora caninum stably expressing TgSAG1 and evaluation of its protective effects against Toxoplasma gondii infection in mice. Vaccine 2010; 28:7243-7. [PMID: 20832493 DOI: 10.1016/j.vaccine.2010.08.096] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 08/24/2010] [Accepted: 08/25/2010] [Indexed: 10/19/2022]
Abstract
Toxoplasma gondii and Neospora caninum are closely related apicomplexan parasites. The surface antigen 1 of T. gondii (TgSAG1) is a major immunodominant antigen and, therefore, is considered to be a good candidate for the development of an effective recombinant vaccine against toxoplasmosis. In this study, N. caninum stably expressing the TgSAG1 gene (Nc/TgSAG1) was constructed using pyrimethamine-resistant DHFR-TS and GFP genes as double-selection markers. The expression level, molecular weight, and antigenic property of recombinant TgSAG1 expressed by the Nc/TgSAG1 were similar to those of the native TgSAG1. The mice immunized with Nc/TgSAG1 induced TgSAG1-specific Th1-dominant immune responses and protected the mice from a lethal challenge infection with T. gondii. These results indicate that N. caninum may provide a new tool for the production of a live recombinant vector vaccine against toxoplasmosis in animals. To our knowledge, this is the first report to evaluate the usefulness of N. caninum-based live vaccine.
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Affiliation(s)
- Guohong Zhang
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan
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15
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Protection against lethal Neospora caninum infection in mice induced by heterologous vaccination with a mic1 mic3 knockout Toxoplasma gondii strain. Infect Immun 2009; 78:651-60. [PMID: 19995895 DOI: 10.1128/iai.00703-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neospora caninum and Toxoplasma gondii are closely related, obligate intracellular parasites infecting a wide range of vertebrate hosts and causing abortion and neonatal morbidity and mortality. Several lines of evidence suggest that cross immunity between these two pathogens could be exploited in the design of strategies for heterologous vaccination. We assessed the ability of an attenuated strain of T. gondii ("mic1-3KO strain") conferring strong protection against chronic and congenital toxoplasmosis to protect mice against lethal N. caninum infection. Mice immunized with mic1-3KO tachyzoites by the oral and intraperitoneal routes developed a strong cellular Th1 response and displayed significant protection against lethal heterologous N. caninum infection, with survival rates of 70% and 80%, respectively, whereas only 30% of the nonimmunized mice survived. We report here the acquisition of heterologous protective immunity against N. caninum following immunization with a live attenuated mic1-3KO strain of T. gondii.
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Toxoplasma gondii rhoptry discharge correlates with activation of the early growth response 2 host cell transcription factor. Infect Immun 2008; 76:4703-12. [PMID: 18678671 DOI: 10.1128/iai.01447-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Toxoplasma gondii is a ubiquitous apicomplexan parasite that can cause severe disease in fetuses and immune-compromised patients. Rhoptries, micronemes, and dense granules, which are secretory organelles unique to Toxoplasma and other apicomplexan parasites, play critical roles in parasite growth and virulence. To understand how these organelles modulate infected host cells, we sought to identify host cell transcription factors triggered by their release. Early growth response 2 (EGR2) is a host cell transcription factor that is rapidly upregulated and activated in Toxoplasma-infected cells but not in cells infected with the closely related apicomplexan parasite Neospora caninum. EGR2 upregulation occurred only when live parasites were in direct contact with the host cell and not from exposure to cell extracts that contain dense granule or micronemal proteins. When microneme-mediated attachment was blocked by pretreating parasites with a calcium chelator, EGR2 expression was significantly reduced. In contrast, when host cells were infected with parasites in the presence of cytochalasin D, which allows rhoptry secretion but prevents parasite invasion, EGR2 was activated. Finally, we demonstrate that Toxoplasma activation of host p38 mitogen-activated protein kinase is necessary but not sufficient for EGR2 activation. Collectively, these data indicate that EGR2 is specifically upregulated by a parasite-derived secreted factor that is most likely a resident rhoptry protein.
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17
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Zhang H, Lee EG, Liao M, Compaore MKA, Zhang G, Kawase O, Fujisaki K, Sugimoto C, Nishikawa Y, Xuan X. Identification of ribosomal phosphoprotein P0 of Neospora caninum as a potential common vaccine candidate for the control of both neosporosis and toxoplasmosis☆. Mol Biochem Parasitol 2007; 153:141-8. [PMID: 17412435 DOI: 10.1016/j.molbiopara.2007.02.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 02/12/2007] [Accepted: 02/28/2007] [Indexed: 11/30/2022]
Abstract
The characterization of the cross-reactive antigens of two closely related apicomplexan parasites, Neospora caninum and Toxoplasma gondii, is important to elucidate the common mechanisms of parasite-host interactions. In this context, a gene encoding N. caninum ribosomal phosphoprotein P0 (NcP0) was identified by immunoscreening of a N. caninum tachyzoite cDNA expression library with antisera from mice immunized with T. gondii tachyzoites. The NcP0 was encoded by a gene with open reading frame of 936 bp, which encoded a protein of 311 amino acids. The NcP0 gene existed as a single copy in the genome and was interrupted by a 432 bp intron. The NcP0 showed 94.5% amino acid identity to T. gondii P0 (TgP0). Anti-recombinant NcP0 (rNcP0) sera recognized a native parasite protein with a molecular mass of 34 kDa in Western blot analysis. Immunofluorescence analysis showed that the NcP0 was localized to the surface of N. caninum tachyzoites. A purified anti-rNcP0 IgG antibody inhibited the growth of N. caninum and T. gondii in vitro in a concentration-dependent manner. These results indicate that P0 is a cross-reactive antigen between N. caninum and T. gondii and a potential common vaccine candidate to control both parasites.
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Affiliation(s)
- Houshuang Zhang
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan
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18
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Zhang H, Compaore MKA, Lee EG, Liao M, Zhang G, Sugimoto C, Fujisaki K, Nishikawa Y, Xuan X. Apical membrane antigen 1 is a cross-reactive antigen between Neospora caninum and Toxoplasma gondii, and the anti-NcAMA1 antibody inhibits host cell invasion by both parasites. Mol Biochem Parasitol 2006; 151:205-12. [PMID: 17156863 DOI: 10.1016/j.molbiopara.2006.11.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 10/31/2006] [Accepted: 11/08/2006] [Indexed: 11/21/2022]
Abstract
The cross-reactive antigens of Neospora caninum and Toxoplasma gondii are important in the exploration to determine the common mechanisms of parasite-host interaction. In this study, a gene encoding N. caninum apical membrane antigen 1 (NcAMA1) was identified by immunoscreening of a N. caninum tachyzoite cDNA expression library with antisera from mice immunized with recombinant T. gondii apical membrane antigen 1 (TgAMA1). NcAMA1 was encoded by an open reading frame of 1695 bp, which encoded a protein of 564 amino acids. The single-copy NcAMA1 gene was interrupted by seven introns. NcAMA1 showed 73.6% amino acid identity to TgAMA1. Mouse polyclonal antibodies raised against the recombinant NcAMA1 (rNcAMA1) recognized a 69-kDa native parasite protein by Western blotting. Immunofluorescence analysis showed that NcAMA1 was localized to the apical end of tachyzoites. Two-dimensional electrophoresis and Western blotting indicated that an approximately 57-kDa cleavage product was released into the excretory/secretory products of N. caninum. Preincubation of free tachyzoites with anti-rNcAMA1 IgG antibodies inhibited the invasion into host cells by N. caninum and T. gondii. These results indicated that AMA1 is a cross-reactive antigen between N. caninum and T. gondii and a potential common vaccine candidate to control two parasites.
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Affiliation(s)
- Houshuang Zhang
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
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19
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McInnes LM, Ryan UM, O'Handley R, Sager H, Forshaw D, Palmer DG. Diagnostic significance of Neospora caninum DNA detected by PCR in cattle serum. Vet Parasitol 2006; 142:207-13. [PMID: 16934934 DOI: 10.1016/j.vetpar.2006.07.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 07/13/2006] [Accepted: 07/18/2006] [Indexed: 11/29/2022]
Abstract
A nested PCR that successfully detected Neospora caninum DNA in serum of cattle was used for investigation of selected abortion cases and in a study of healthy pregnant cows at an abattoir. N. caninum DNA was not detected in serum from antibody positive dams that aborted due to N. caninum, but was present in serum of some antibody negative dams that aborted due to other causes. N. caninum DNA was also found in the serum of about half of the animals that aborted of undetermined cause, but was not detected in cow sera from two beef cattle herds in Western Australia with no recent history of abortion. In the abattoir study of 79 dams and their foetuses N. caninum DNA was found in serum of 3 dams and in material from 11 foetuses. The majority of the cows and all foetuses were antibody negative. Our findings suggest that there is no obvious relationship between the presence or absence of N. caninum DNA in serum and the presence of antibodies to N. caninum in dams, the presence of N. caninum DNA in foetuses or abortion due to N. caninum. This is the first report of the detection of N. caninum DNA in serum of cattle rather than the white blood cell fraction. It indicates the presence of free tachyzoites and/or parasite DNA in circulation. The results suggest that persistent infection in the absence of antibodies is a possible outcome of N. caninum infection. Infection of foetuses in the absence of antibodies supports the possibility of persistent infection due to immunotolerance to an early in utero infection. It is therefore important to test for N. caninum DNA as well as antibodies for the detection of exposed and/or infected animals. However, the presence or absence of N. caninum antibodies or DNA did not support nor exclude N. caninum as the cause of abortion. Additional criteria are required for a positive diagnosis of abortion caused by N. caninum.
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Affiliation(s)
- Linda M McInnes
- Division of Health Sciences, School of Veterinary and Biomedical Science, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia
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Häsler B, Hernandez JA, Reist M, Sager H, Steiner-Moret C, Staubli D, Stärk KDC, Gottstein B. Neospora caninum: Serological follow-up in dairy cows during pregnancy. Vet Parasitol 2006; 137:222-30. [PMID: 16469449 DOI: 10.1016/j.vetpar.2006.01.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Revised: 12/19/2005] [Accepted: 01/10/2006] [Indexed: 11/26/2022]
Abstract
We conducted a longitudinal study to follow-up the anti-Neospora caninum serologic status in 30 initially seropositive and 83 initially seronegative cows during their pregnancy. Study cows were blood-sampled every other month during pregnancy until parturition. Blood serum samples were screened for anti-N. caninum antibodies by ELISA. Cows that seroconverted were re-tested by immunoblot as a confirmation test. Among 30 seropositive cows, 28 cows remained seropositive during the whole pregnancy, whereas 2 cows transiently tested negative at least once during pregnancy. Among 83 seronegative cows, 82 cows remained seronegative and 1 cow tested positive three times during the sixth, eighth and last month of pregnancy. As only 2 out of 30 seropositive animals and 1 out of 83 animals changed their serologic status during pregnancy, the study results indicate that there is only a minor temporal instability of anti-N. caninum antibody reactivity in adult cattle.
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Affiliation(s)
- Barbara Häsler
- Swiss Federal Veterinary Office, Schwarzenburgstrasse 155, CH-3003 Bern, Switzerland.
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21
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Johnson AM. Speculation on possible life cycles for the clonal lineages in the genus toxoplasma. ACTA ACUST UNITED AC 2005; 13:393-7. [PMID: 15275153 DOI: 10.1016/s0169-4758(97)01129-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent evidence suggests that the strains currently classified in the genus Toxoplasma, ie. within the species Toxoplasma gondii, may actually comprise at least two clonal lineages correlated with their virulence in mice. Here, Alan Johnson reviews these data in the context of evolution and speciation within the genus, and raises hypotheses on how the virulent lineage may undergo an asexual life cycle in nature, similar to that found for the very closely related coccidian, Neospora camnum. The putative vertical transmission life cycle of this mouse virulent lineage of T. gondii could involve passage to the foetus late in pregnancy, or transmission in milk to the neonate after birth.
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Affiliation(s)
- A M Johnson
- Molecular Parasitology Unit, Department of Cell and Molecular Biology, University of Technology. Sydney, Westbourne Street, Gore Hill, NSW 2065, Australia.
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Akca A, Gokce HI, Guy CS, McGarry JW, Williams DJL. Prevalence of antibodies to Neospora caninum in local and imported cattle breeds in the Kars province of Turkey. Res Vet Sci 2005; 78:123-6. [PMID: 15563918 DOI: 10.1016/j.rvsc.2004.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/30/2004] [Indexed: 11/17/2022]
Abstract
This study investigates the seroprevalence of Neospora caninum in cattle in the province of Kars in north-eastern Turkey. A total of 301 serum samples, 228 from local breeds of cows with a history of recent abortion and the remaining 73 collected at random from Simmental cows imported from Germany or their offspring, were tested for anti-Neospora antibodies by ELISA. All the serum samples from local breeds were negative for N. caninum antibodies, apart from one which tested inconclusive. In contrast six of the samples (8.2% with 95%CI: 2-14.5%) from Simmental cows tested positive. There was a significant difference (P<0.001) in the seroprevalence of N. caninum between local and Simmental breeds, even if the inconclusive test was considered positive, and the odds ratio of its occurrence in the Simmental breed was 20.3. In conclusion, it is unlikely that N. caninum contributes to abortion in local cattle breeds and our results also suggest that N. caninum was introduced to the region by the importation of Simmental cattle and that the vertical transmission of the parasite in cattle is important in the region.
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Affiliation(s)
- A Akca
- Department of Parasitology, Faculty of Veterinary Medicine, University of Kafkas, 36040-Kars, Turkey
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23
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Bartley PM, Kirvar E, Wright S, Swales C, Esteban-Redondo I, Buxton D, Maley SW, Schock A, Rae AG, Hamilton C, Innes EA. Maternal and fetal immune responses of cattle inoculated with Neospora caninum at mid-gestation. J Comp Pathol 2004; 130:81-91. [PMID: 15003463 DOI: 10.1016/j.jcpa.2003.08.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2003] [Accepted: 08/23/2003] [Indexed: 11/30/2022]
Abstract
The humoral and cell-mediated immune responses of pregnant cattle and their fetuses were examined at intervals after infection with Neospora caninum tachyzoites at mid-gestation (day 140). All cattle seroconverted and interferon gamma was detected in supernatants of peripheral blood mononuclear cells stimulated with specific antigen. At day 14 post-inoculation (pi), specific cell proliferation responses were detected in the lymph node draining the site of inoculation and in the uterine lymph node. The peak response was recorded in the majority of maternal lymph nodes by day 28 pi and cells from the maternal retropharyngeal lymph node, which in part drains the central nervous system, showed no specific activity to N. caninum until day 42 pi. This changing pattern of immune responsiveness may reflect parasite invasion and development within different host tissues. Fetal lymph node cells showed mitogen responsiveness from day 14 pi (day 154 of gestation) and also showed N. caninum-specific cell proliferation and interferon-gamma responses by day 28 pi (day 168 of gestation). At day 42 pi, specific cell-mediated immune responses were not apparent; however, N. caninum-specific fetal IgG and IgM antibodies were detected.
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Affiliation(s)
- P M Bartley
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Edinburgh, Scotland EH26 0PZ, UK
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Schatzberg SJ, Haley NJ, Barr SC, deLahunta A, Olby N, Munana K, Sharp NJH. Use of a multiplex polymerase chain reaction assay in the antemortem diagnosis of toxoplasmosis and neosporosis in the central nervous system of cats and dogs. Am J Vet Res 2004; 64:1507-13. [PMID: 14672429 DOI: 10.2460/ajvr.2003.64.1507] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To develop a multiplex polymerase chain reaction (PCR) assay for the detection of Toxoplasma gondii and Neospora caninum DNA in canine and feline biological samples. SAMPLE POPULATION; Biological samples from 7 cats with systemic (n = 4) or CNS (3) toxoplasmosis, 6 dogs with neospora- or toxoplasma-associated encephalitis, and 11 animals with nonprotozoal disease. PROCEDURE Primers for T gondii, N caninum, and the canine ferritin gene (dogs) or feline histone 3.3 gene (cats) were combined in a single PCR assay. The DNA was extracted from paraffin-embedded brain tissue, CSF, or skeletal muscle. The PCR products with positive results were cloned, and sequence identity was confirmed. RESULTS Of 7 cats and 4 dogs with immunohistochemical or serologic evidence of toxoplasmosis, PCR results were positive for all cats and 3 dogs for T gondii, and positive for T gondii and N caninum for 1 dog. Another dog had negative PCR results for both parasites. Of 2 dogs with immunohistochemical or serologic evidence of neosporosis, PCR results were positive for 1 for N caninum and positive for the other for T gondii. All negative-control samples yielded negative results for T gondii and N caninum on the PCR assay. CONCLUSIONS AND CLINICAL RELEVANCE Standard tests for toxoplasmosis or neosporosis associated with the CNS rely on serologic, histologic, or immunohistochemical analysis and can be difficult to interpret. The multiplex PCR assay with built-in control reactions could be a complementary clinical tool for the antemortem diagnosis of toxoplasmosis or neosporosis associated with the CNS.
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Affiliation(s)
- Scott J Schatzberg
- Department of Medicine, The Bobst Hospital, Animal Medical Center, New York, NY 10021, USA
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Hernandez J, Risco C, Donovan A. Risk of abortion associated with Neospora caninum during different lactations and evidence of congenital transmission in dairy cows. J Am Vet Med Assoc 2002; 221:1742-6. [PMID: 12494973 DOI: 10.2460/javma.2002.221.1741] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To examine the relationship between exposure to Neospora caninum and abortion in dairy cows during their first, second, third, and fourth or later lactations and to establish the main mode of transmission in female calves from birth until their first pregnancy was terminated by abortion or parturition. DESIGN Prospective observational study. ANIMALS 460 Holstein cows and 79 female calves. PROCEDURE Cows were classified as seropositive or seronegative to N caninum within 7 days after calving; incidence of abortion was compared between groups during different lactations. Blood samples were collected from female calves before ingestion of colostrum and every 6 months until their first pregnancy was terminated by abortion or parturition; number of seropositive calves was compared between seropositive and seronegative dams. RESULTS During the first pregnancy of their second lactation, risk of abortion for seropositive cows was 2.8 times that of seronegative cows. Among 10 calves born to seropositive cows, 4 were classified as seropositive at birth and thereafter. Among 69 calves born to seronegative cows, all were classified as seronegative at birth; 67 calves remained seronegative thereafter. CONCLUSIONS AND CLINICAL RELEVANCE Exposure to N caninum alone was not significantly associated with abortion in cows during the first, third, and fourth or later lactations. Seropositive cows that have aborted previously may have subsequent abortions attributable to N caninum. Congenital infection was the main mode of N caninum transmission in a cohort of female calves.
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Affiliation(s)
- Jorge Hernandez
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0136, USA
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26
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Abstract
In the present study a murine encephalitis model was used to investigate if protection against neosporosis could be achieved by immunisation. Groups of 10 mice were immunised with a sublethal dose of live Neospora caninum tachyzoites, N. caninum antigens incorporated into iscoms, N. caninum lysate mixed with Quil A, or N. caninum lysate in PBS. Control mice were given Quil A only. Challenge infection with 2.5x10(6) N. caninum tachyzoites resulted in clinical symptoms that remained until the end of the experiment in the controls. In contrast, mice immunised with live parasites or parasite lysate in Quil A only showed mild and transient symptoms. Of nine mice immunised with N. caninum iscoms, seven recovered while two died. Most severely affected were the mice immunised with parasite lysate only; all of them died within 28 days post-infection. Histological examination and scoring of brain lesions gave a significantly lower (P<0.0001) lesion score in mice immunised with live parasites than in controls. The groups immunised with iscoms or lysate and Quil A also had reduced lesion scores (P<0.04 and 0.07, respectively) but not the group given parasite lysate alone. The lesions seen in the latter group differed from those in the other groups. There was less cellular reaction and more tachyzoites indicating an active infection. The N. caninum specific antibody responses and cytokine production (IFN-gamma, IL-4 and IL-5) of splenocytes were analysed at the time of challenge infection. The results suggest a correlation between protection and high levels of IFN-gamma. Also, the immune responses recorded in mice immunised with parasite lysate without adjuvant were relatively weak and more towards the Th2 type, when compared with the other immunisation schedules. This is consistent with the weaker inflammatory response observed in the brains of these mice.
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Affiliation(s)
- Anna Lundén
- Department of Parasitology (SWEPAR), Swedish University of Agricultural Sciences and National Veterinary Institute, SE-751 89 Uppsala, Sweden.
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27
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Hernandez J, Risco C, Donovan A. Association between exposure to Neospora caninum and milk production in dairy cows. J Am Vet Med Assoc 2001; 219:632-5. [PMID: 11549092 DOI: 10.2460/javma.2001.219.632] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine association between exposure to Neospora caninum and milk production in dairy cows. DESIGN Prospective observational study. ANIMALS 565 Holstein cows. PROCEDURE Cows were classified as seropositive or seronegative to N. caninum within 7 days after calving by use of a kinetic ELISA. Milk production was compared between seropositive and seronegative cows. RESULTS On the basis of 305-day mature equivalent milk production data, seropositive cows produced less milk (2.8 lb/cow per day) than did seronegative cows. In addition, analysis of results throughout the first 300 days of lactation revealed that after adjusting for effects of lactation number, calving season, clinical mastitis, and lameness, milk weight of seropositive cows was 2.5 lb/cow per day less than that of seronegative cows. CONCLUSIONS AND CLINICAL RELEVANCE Exposure to N. caninum was associated with a 3 to 4% decrease in milk production. A decrease in milk production of 800 lb/cow for a typical 305-day lactation represents a loss of $128/cow.
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Affiliation(s)
- J Hernandez
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32610-0136, USA
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Miller MA, Sverlow K, Crosbie PR, Barr BC, Lowenstine LJ, Gulland FM, Packham A, Conrad PA. Isolation and characterization of two parasitic protozoa from a Pacific harbor seal (Phoca vitulina richardsi) with meningoencephalomyelitis. J Parasitol 2001; 87:816-22. [PMID: 11534647 DOI: 10.1645/0022-3395(2001)087[0816:iacotp]2.0.co;2] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Two species of protozoans were isolated from a harbor seal with fatal meninogoencephalitis. Serologic reactivity was detected to both Sarcocystis neurona and Toxoplasma gondii. Parasites associated with brain inflammation and necrosis reacted only with immunohistochemical stains utilizing polyclonal antisera raised against Sarcocystis neurona. However, 2 distinct parasites were observed in cell cultures derived from the seal's brain tissue. These parasites were separated by mouse passage and limiting dilution. Purified zoites from 1 isolate (HS1) reacted strongly with polyclonal antiserum to S. neurona and with the harbor seal's own serum (1:2,560 for each) on indirect immunofluorescent antibody tests (IFAT), but weakly to antisera to T. gondii and Neospora caninum (1:40). Zoites from the second isolate (HS2) reacted positively with T. gondii polyclonal antiserum (1:81,920) and with the harbor seal's own serum (1:640), but weakly to S. neurona and N. caninum antisera (1:80 or less). Amplification and sequence analysis of protozoal DNA encoding portions of the 18s ribosomal RNA (18s rDNA) and the adjacent first internal transcribed spacer (ITSI) were performed for both isolates, and resulting sequences were compared to those from similar protozoans. Based on molecular characterization, parasite morphology, serologic reactivity, histology, and immunohistochemistry, HS1 was indistinguishable from S. neurona, and HS2 was indistinguishable from T. gondii.
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Affiliation(s)
- M A Miller
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, 95616-8739, USA
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29
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Maley SW, Buxton D, Thomson KM, Schriefer CE, Innes EA. Serological analysis of calves experimentally infected with Neospora caninum: a 1-year study. Vet Parasitol 2001; 96:1-9. [PMID: 11182233 DOI: 10.1016/s0304-4017(00)00428-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A serological study was conducted with calves experimentally infected with the protozoan parasite Neospora caninum. The animals were inoculated with either a low or high dose of N. caninum tachyzoites and temperature responses monitored daily for the first 2 weeks after inoculation. Blood samples were collected before inoculation, and at regular intervals thereafter for 1 year. Serological analysis was achieved using an indirect fluorescent antibody test (IFAT), an enzyme-linked immunosorbent assay (ELISA) and an IgG avidity ELISA. Injection of Neospora produced a significant rise in rectal temperature in the high dose group. In addition, the lymph node draining the site of inoculation increased in size following injection in all animals, in both infected groups, before returning to normal by day 14 after injection. Both groups given N. caninum produced specific antibody that was detected by the IFAT and the ELISA, which remained elevated for the 12-month duration of the experiment. The specific Neospora antibodies produced did not cross-react in an IFAT for the detection of antibodies to Toxoplasma gondii. IgG avidity increased 2 weeks after inoculation, in both infected groups, until week 12 when infection was well established. There was a little difference between the two infected dose groups. This study demonstrates that the two different doses of N. caninum produced a similar antibody response, and that the higher dose also induced a febrile reaction. The IgG avidity ELISA was successful at distinguishing between recent and long-standing infection in this study. However, in both groups, there was fluctuation in the levels of specific antibody throughout the yearlong study, which accords with similar experiments in pregnant cattle, where it has been suggested that fluctuation may indicate periodic recrudescence of infection and a re-stimulation of antibody production by antigen.
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Affiliation(s)
- S W Maley
- Moredun Research Institute, International Research Centre, Pentlands Science Park, Edinburgh EH26 0PZ, UK.
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Innes EA, Buxton D, Maley S, Wright S, Marks J, Esteban I, Rae A, Schock A, Wastling J. Neosporosis. Aspects of epidemiology and host immune response. Ann N Y Acad Sci 2001; 916:93-101. [PMID: 11193706 DOI: 10.1111/j.1749-6632.2000.tb05278.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neospora caninum is a recently recognized protozoan parasite which has been described as causing a neuromuscular paralysis in dogs and is emerging as a major cause of bovine infertility and abortion worldwide. The parasite is known to infect a range of warm blooded animals but the disease predominates in dogs and cattle. It is not yet known if N. caninum can infect and cause disease in people. The dog has recently been identified as the definitive host and the parasite may be transmitted through the ingestion of oocysts or congenitally from mother to fetus. N. caninum is known to infect red foxes (Vulpes vulpes) and coyotes (Canis latrans) and the role of wildlife species as reservoirs of infection requires further investigation. Little is known about the range of parasite genotypes within the environment or the variation in virulence between different strains. RAPD-PCR analysis of geographically distinct bovine and canine isolates has revealed little genetic variation. Epidemiological studies from different areas of the world have investigated the importance of N. caninum as an abortifacient agent and longitudinal studies have shown the high rate (approximately 80%) of congenital transmission within infected herds. Information on the rates of repeat abortion due to neosporosis are less well defined however current estimates put this at 5% suggesting that cattle may develop some form of protective immunity against N. caninum-induced abortion. Diagnosis of the disease is based upon detection of the parasite in the tissues, most commonly using immunohistochemistry with additional information provided by serology. However, although positive fetal serology is a strong indicator of exposure to the parasite, care should be taken in the interpretation of maternal serology. As we understand more about the epidemiology of neosporosis we are also better able to interpret the results of diagnostic tests. The mere presence of the parasite does not necessarily infer that this was the primary cause of abortion. CD4+ T-cells, interferon gamma and macrophages have all been found to significantly inhibit multiplication of N. caninum tachyzoites. The nature of a protective immune response and its modulation in the pregnant animal is discussed.
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Affiliation(s)
- E A Innes
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Edinburgh, EH26 OPZ, United Kingdom.
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31
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Barta JR, Martin DS, Carreno RA, Siddall ME, Profous-Juchelkat H, Hozza M, Powles MA, Sundermann C. Molecular phylogeny of the other tissue coccidia: Lankesterella and Caryospora. J Parasitol 2001; 87:121-7. [PMID: 11227876 DOI: 10.1645/0022-3395(2001)087[0121:mpotot]2.0.co;2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Nearly complete sequences were obtained from the 18S rDNA genes of Eimeria falciformis (the type species of the genus), Caryospora bigenetica, and Lankesterella minima. Two clones of the rDNA gene from C. higenetica varied slightly in primary structure. Parsimony-based and maximum likelihood phylogenetic reconstructions with a number of other apicomplexan taxa support 2 major clades within the Eucoccidiorida, i.e., the isosporoid coccidia (consisting of Toxoplasma, Neospora, Isospora [in part], and Sarcocystis spp.) and a second clade containing Lankesterella and Caryospora spp., as well as the eimeriid coccidia (Cyclospora, Isospora [in part], and Eimeria spp.). Our observations suggest that Caryospora spp. may not belong in the family Eimeriidae but rather may be allied with the family Lankesterellidae with which they share molecular and life history similarities. This may be a third lineage of coccidian parasites that has independently evolved a unique heteroxenous transmission strategy.
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Affiliation(s)
- J R Barta
- Department of Pathobiology, University of Guelph, Ontario, Canada
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32
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Abstract
An extrachromosomal genome of between 27 and 35 kb has been described in several apicomplexan parasites including Plasmodium falciparum and Toxoplasma gondii. Examination of sequence data proved the genomes to be a remnant plastid genome, from which all genes encoding photosynthetic functions had been lost. Localisation studies had shown that the genome was located within a multi-walled organelle, anterior to the nucleus. This organelle had been previously described in ultrastructural studies of several genera of apicomplexa, but no function had been attributed to it. This invited review describes the evolution of knowledge on the apicomplexan plastid, then discusses current research findings on the likely role of the plastid in the Apicomplexa. How the plastid may be used to effect better drug treatments for apicomplexan diseases, and its potential as a marker for investigating phylogenetic relationships among the Apicomplexa, are discussed.
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Affiliation(s)
- M T Gleeson
- Department of Cell and Molecular Biology, Faculty of Science, University of Technology, Westbourne Street, Gore Hill NSW 2065, Sydney, Australia.
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33
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Fazaeli A, Carter PE, Pennington TH. Intergenic spacer (IGS) polymorphism: a new genetic marker for differentiation of Toxoplasma gondii strains and Neospora caninum. J Parasitol 2000; 86:716-23. [PMID: 10958446 DOI: 10.1645/0022-3395(2000)086[0716:isipan]2.0.co;2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The region between the 28S and 18S rRNA genes, including the intergenic spacer (IGS) region and the 5S rRNA gene, from 32 strains of Toxoplasma gondii and the NC1 strain of Neospora caninum was amplified and used for DNA sequencing and/or restriction fragment length polymorphism (RFLP) analysis. The 5S rDNA sequences from 20 strains of T. gondii were identical. The IGS region between the 5S and 18S rRNA genes (nontranscribed spacer 2 or NTS 2) showed 10 nucleotide variations. Six of the 10 variant positions correlated with the murine virulence of the strains. Intraspecific polymorphisms distinguished the virulent strains of zymodemes 5, 6, and 8 from other virulent strains (in zymodeme 1). RFLP methods (IGS-RFLP) were developed and used to characterize the virulent and avirulent patterns among 29 T. gondii strains. Sequence diversity of 19.8% was found between T. gondii and N. caninum when comparing a region of 919 bp at the 3' end of NTS 2. The sequence variation in ribosomal IGS could therefore be a useful marker for Toxoplasma strain identification and for distinguishing N. caninum from T. gondii.
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MESH Headings
- Animals
- Base Sequence
- DNA, Protozoan/chemistry
- DNA, Ribosomal/chemistry
- Genetic Markers
- Humans
- Molecular Sequence Data
- Neospora/classification
- Neospora/genetics
- Neospora/isolation & purification
- Neospora/pathogenicity
- Polymerase Chain Reaction
- Polymorphism, Restriction Fragment Length
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 28S/genetics
- RNA, Ribosomal, 5S/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Toxoplasma/classification
- Toxoplasma/genetics
- Toxoplasma/isolation & purification
- Toxoplasma/pathogenicity
- Virulence
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Affiliation(s)
- A Fazaeli
- Department of Medical Microbiology, University of Aberdeen, Medical School, Foresterhill, United Kingdom
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34
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Abstract
Since the identification of Neospora caninum in 1984 as a parasite separate from Toxoplasma gondii by Bjerkas et al., and its subsequent characterization and classification in 1988 by Dubey and co-workers, this parasite has attracted increasing attention, primarily as an important causative agent of abortion in cattle and neuromuscular disease in dogs, but also as a complementary model system to T. gondii for investigating the basic biology of intracellular parasitism. During November 11-14, 1999, the COST 820 Annual meeting (Vaccines against coccidioses) took place in Interlaken, Switzerland. Almost half of the papers presented at that meeting were on N. caninum and neosporosis, reflecting the increasing awareness of the importance of this parasite on part of the scientific community in Europe. On the occasion of the meeting, participants in this COST Action involved in Neospora research in Europe were asked to participate in this invited review in order to document the growing interest in N. caninum and the disease it causes. Thus, this paper is a unique collection of contributions provided by several European experts in the field. It is comprised of 10 reviews or original papers on different aspects of Neospora research including epidemiology, immunology, application and development of serological tools, and molecular characterisation of the parasite currently carried out throughout Europe. In addition, two distinguished invited speakers from overseas (Milton McAllister and John Ellis) provided valuable contributions. This invited review demonstrates that the COST 820 Action has brought together scientists from all over Europe and other parts of the world, and has laid the basis for many fruitful collaborations. The studies described here will contribute in assessing the relevance of neosporosis as a potential risk factor not only for animals, but also for human health.
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Affiliation(s)
- A Hemphill
- Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012, Bern, Switzerland.
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35
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Sonda S, Fuchs N, Gottstein B, Hemphill A. Molecular characterization of a novel microneme antigen in Neospora caninum. Mol Biochem Parasitol 2000; 108:39-51. [PMID: 10802317 DOI: 10.1016/s0166-6851(00)00200-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The apical complex of the parasites belonging to the phylum Sporozoa is believed to be critically involved in the events leading to host cell invasion. The characterization of the components of this subcellular structure is therefore an important step towards understanding how these parasites achieve host cell entry. Affinity-purification of an anti-Neospora caninum antiserum on a reactive protein band of approximately 40 kDa following Triton-X-114 extraction of parasite proteins, SDS-PAGE and Western blotting, yielded an immunoglobulin fraction which, by immunofluorescence, stained predominantly the apical portion of N. caninum tachyzoites. Following immunoscreening of a N. caninum tachyzoite lambdagt22 cDNA expression library, the respective full length cDNA sequence was determined. This sequence was found to encode a protein of 362 amino acids, with a calculated Mr of 38086. This protein is encoded by a single copy gene which produces a transcript of 2.4 kb. Sequence analysis showed that it contains a N-terminal putative signal peptide sequence and two potential membrane spanning regions. Four consecutive epidermal growth factor like domains were identified, as well a conserved sequence motif for binding of ATP/GTP (P-loop). The full length cDNA was expressed as a recombinant poly-histidine fusion protein in Escherichia coli, and antibodies affinity purified on this protein labelled exclusively a 38 kDa band on immunoblots of N. caninum extracts. In addition, specific labeling of a 45 kDa band in Toxoplasma gondii tachyzoite extracts was observed. By immunofluorescence, these antibodies stained predominantly the apical portion of both N. caninum and T. gondii tachyzoites, but the protein was absent from the parasite surface. Immunogold localization in LR-White embedded N. caninum tachyzoites demonstrated staining of predominantly the apically located micronemes, as well as of dense granules located at the posterior end of the tachyzoites. As evidenced by immunohistochemistry, this Neospora microneme antigen and its immunoreactive counterpart in Toxoplasma appeared to be expressed in both tachyzoite and bradyzoite stages.
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Affiliation(s)
- S Sonda
- Institute of Parasitology, Faculties of Veterinary Medicine and Medicine, University of Berne, Länggass-Strasse 122, CH-3012, Berne, Switzerland
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36
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Mathew JS, Van Den Bussche RA, Ewing SA, Malayer JR, Latha BR, Panciera RJ. Phylogenetic relationships of Hepatozoon (Apicomplexa: Adeleorina) based on molecular, morphologic, and life-cycle characters. J Parasitol 2000; 86:366-72. [PMID: 10780559 DOI: 10.1645/0022-3395(2000)086[0366:prohaa]2.0.co;2] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
To evaluate higher-level affinities of Hepatozoon species within Apicomplexa, we sequenced the 18S rRNA gene from 2 parasites (Hepatozoon americanum and Hepatozoon canis) of dogs and 1 (Hepatozoon catesbianae) of bullfrogs. Sequences from other apicomplexans among the Sarcocystiidae, Eimeriidae, Theileriidae, Plasmodiidae, Cryptosporiidae, and Babesiidae, a Perkinsus species and 2 dinoflagellates were obtained from GenBank. Phylogenetic analysis indicated that Plasmodium, Cryptosporidium, and Hepatozoon form a monophyletic group distinct from representatives of other apicomplexan families. Although equivocal, our analysis indicated that Plasmodium and Cryptosporidium are sister taxa and that Hepatozoon is basal to them. To evaluate phylogenetic affinities among H. americanum, H. canis, and other species of Hepatozoon, we examined 18 morphologic and life-cycle features of 13 species currently assigned to Hepatozoon. This analysis indicates paraphyly of Hepatozoon (as currently arranged) because Hepatozoon lygosomarum was found most closely related to Hemolivia mauritanicum. These results, combined with results of previous studies, support elevating Hepatozoon to familial level (Hepatozoidae) as originally suggested by Wenyon in 1926. Both DNA sequence data and morphologic and life-cycle characters support a sister-group relationship between H. americanum and H. canis.
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Affiliation(s)
- J S Mathew
- Department of Infectious Diseases and Physiology, Oklahoma State University, Stillwater 74078, USA
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37
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Atkinson RA, Cook RW, Reddacliff LA, Rothwell J, Broady KW, Harper P, Ellis JT. Seroprevalence of Neospora caninum infection following an abortion outbreak in a dairy cattle herd. Aust Vet J 2000; 78:262-6. [PMID: 10840574 DOI: 10.1111/j.1751-0813.2000.tb11752.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To investigate the seroprevalence of Neospora caninum infection in a commercial dairy cattle herd, 15 months after detection of an abortion outbreak. PROCEDURE Sera from the whole herd (n = 266) were examined for N caninum antibodies by indirect fluorescent antibody test (IFAT) and immunoblot analysis. Herd records were reviewed to collate serological results with abortion history, proximity to calving, and pedigree data. RESULTS The seroprevalence of N caninum infection was 24% (63/266) for IFAT titre > or = 160, 29% (78/266) for immunoblot positive (+ve), and 31% (82/266) for IFAT > or = 160 and/or immunoblot +ve; 94% (59/63) of animals with IFAT > or = 160 were immunoblot +ve. The association between seropositivity (IFAT > or = 160 and/or immunoblot +ve) and history of abortion was highly significant (P < 0.001); the seroprevalence was 86% (18/21) in aborting cows, compared with 30% (50/164) in non-aborting animals. The abortion rate for seropositive cows was 26% (18/68) compared with 3% (3/117) for seronegative animals. IFAT titres of infected cows were higher within 2 months of calving than at other times (P < 0.001). The association between seropositivity in dams and daughters was highly significant (P = 0.009). CONCLUSIONS The abortions were associated with N caninum infection and there was evidence of reactivation of latent infection close to calving and congenital transmission of infection. Immunodominant antigens identified by immunoblots may prove useful for improved diagnostic tests.
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Affiliation(s)
- R A Atkinson
- Molecular Parasitology Unit, University of Technology, Sydney, New South Wales
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38
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Williams DJ, Davison HC, Helmick B, McGarry J, Guy F, Otter A, Trees AJ. Evaluation of a commercial ELISA for detecting serum antibody to Neospora caninum in cattle. Vet Rec 1999; 145:571-5. [PMID: 10606017 DOI: 10.1136/vr.145.20.571] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A commercially available serum antibody detection enzyme-linked immunosorbent assay for Neospora caninum in cattle was evaluated against an immunofluorescent antibody test (IFAT) by applying it to 397 sera from normal adult cattle, 352 sera from cattle which had recently aborted, and 422 sera from two herds which had a history of N caninum-associated abortions. It was evaluated in two laboratories and showed high reproducibility, repeatability and almost perfect or substantial agreement with the IFAT.
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Affiliation(s)
- D J Williams
- Veterinary Parasitology, Liverpool School of Tropical Medicine/Faculty of Veterinary Science, University of Liverpool
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39
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Mugridge NB, Morrison DA, Heckeroth AR, Johnson AM, Tenter AM. Phylogenetic analysis based on full-length large subunit ribosomal RNA gene sequence comparison reveals that Neospora caninum is more closely related to Hammondia heydorni than to Toxoplasma gondii. Int J Parasitol 1999; 29:1545-56. [PMID: 10608441 DOI: 10.1016/s0020-7519(99)00150-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Since its first description in the late 1980s, Neospora caninum has been recognised as a prominent tissue cyst-forming parasite due to its ability to induce congenital disease and abortion in animals, especially cattle. It is found worldwide and is a cause of significant economic losses for the livestock industry. However, its place within the family Sarcocystidae, like that of several other taxa, remains unresolved. Neospora caninum shares several morphological and life cycle characters with Hammondia heydorni, although it is most commonly thought of as being a close relative of Toxoplasma gondii. This study presents information regarding the phylogenetic relationship of N. caninum to species currently classified into the genus Hammondia, as well as to two strains (RH and ME49) of T. gondii based on the full-length large subunit ribosomal RNA gene. Phylogenetic analyses using two alignment strategies and three different tree-building methods showed that the two species in the genus Hammondia are paraphyletic. Neospora caninum was shown to form a monophyletic clade with H. heydorni instead of T. gondii, which in turn was shown to be most closely related to H. hammondi. The finding that N. caninum and H. heydorni are closely related phylogenetically may aid the elucidation of currently unknown aspects of their biology and epidemiology, and suggests that H. heydorni should be considered in the differential diagnosis of N. caninum from other apicomplexan parasites.
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Affiliation(s)
- N B Mugridge
- Molecular Parasitology Unit, University of Technology Sydney, NSW, Australia
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40
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Abstract
Neospora caninum is an apicomplexan parasite which causes neosporosis, namely stillbirth and abortion in cattle, and neuromuscular disease in dogs. Although N. caninum is phylogenetically and biologically closely related to Toxoplasma gondii, it is antigenically clearly distinct. In analogy to T. gondii, three stages have been identified. These are: (i) asexually proliferating tachyzoites; (ii) tissue cysts harbouring slowly dividing bradyzoites; and (iii) oocysts containing sporozoites. The sexually produced stage of this parasite has only recently been identified, and has been shown to be shed with the faeces from dogs orally infected with N. caninum tissue cysts. Thus dogs are definitive hosts of N. caninum. Tachyzoites can be cultivated in vitro using similar techniques as previously described for T. gondii. Methods for generating tissue cysts containing N. caninum bradyzoites in mice, and purification of these cysts, have been developed. A number of studies have been undertaken to identify and characterise at the molecular level specific antigenic components of N. caninum in order to improve serological diagnosis and to enhance the current view on the many open questions concerning the cell biology of this parasite and its interactions with the host on the immunological and cellular level. The aim of this paper is to provide an overview on the approaches used for detection of antigens in N. caninum. The studies discussed here have had a great impact in the elucidation of the immunological and pathogenetic events during infection, as well as the development of potential new immunotherapeutic tools for future vaccination against N. caninum infection.
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Affiliation(s)
- A Hemphill
- Institute of Parasitology, Faculty of Veterinary Medicine, University of Bern, Switzerland.
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41
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Schares G, Dubremetz JF, Dubey JP, Bärwald A, Loyens A, Conraths FJ. Neospora caninum: identification of 19-, 38-, and 40-kDa surface antigens and a 33-kDa dense granule antigen using monoclonal antibodies. Exp Parasitol 1999; 92:109-19. [PMID: 10366536 DOI: 10.1006/expr.1999.4403] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neospora caninum, a coccidian parasite closely related to Toxoplasma gondii, can infect a broad host range and is regarded as an important cause of bovine abortion worldwide. In the present study, four antigens of N. caninum were partially characterized using monoclonal antibodies. Immunofluorescence of viable tachyzoites as well as the immunoprecipitation of antigens extracted from tachyzoites previously labeled by surface biotinylation revealed that three of these antigens with apparent molecular weights of 40, 38, and 19 kDa are located in the outer surface membrane of this parasite stage. Further evidence for the surface localization of the 38-kDa antigen was obtained by immunoelectron microscopy. In addition to the surface molecules, an antigen located in dense granules and in the tubular network of the parasitophorous vacuole was detected by another monoclonal antibody. When tachyzoite antigens separated under nonreducing conditions were probed on Western blots, this antibody reacted mainly with a 33-kDa antigen. Immunohistochemical analysis of infected tissue sections indicated that the 33-kDa dense granule antigen is present in both tachyzoites and bradyzoites, while the 38-kDa surface antigen from tachyzoites seems to be absent in bradyzoites.
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Affiliation(s)
- G Schares
- Institut für Epidemiologische Diagnostik, Bundesforschungsanstalt für Viruskrankheiten der Tiere, Seestrasse 55, Wusterhausen, D-16868, Germany.
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42
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Abstract
Neospora caninum is an apicomplexan parasite which invades many different cell types and tissues. It causes neosporosis, namely stillbirth and abortion in cattle and neuromuscular disease in dogs, and has been found in several other animal species. N. caninum is closely related to Toxoplasma gondii, and controversial opinions exist with respect to its phylogenetical status. Initially, two stages of N. caninum had been identified, namely asexually proliferating tachyzoites and bradyzoites. The sexually produced stage of this parasite, oocysts containing sporozoites, has been found only recently. In order to answer the many open questions regarding its basic biology and its relationship with the host, a number of diagnostic tools have been developed. These techniques are based on the detection of antibodies against parasites in body fluids, the direct visualization of the parasite within tissue samples by immunohistochemistry, or the specific amplification of parasite DNA by PCR. Other studies have been aiming at the identification of specific antigenic components of N. caninum, and the molecular and functional characterization of these antigens with respect to the cell biology of the parasite. Clearly, molecular approaches will also be used increasingly to elucidate the immunological and pathogenetic events during infection, but also to prepare potential new immunotherapeutic tools for future vaccination against N. caninum infection.
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Affiliation(s)
- A Hemphill
- Institute of Parasitology, Faculty of Veterinary Medicine, University of Bern, Switzerland
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43
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Holmdahl OJ, Morrison DA, Ellis JT, Huong LT. Evolution of ruminant Sarcocystis (Sporozoa) parasites based on small subunit rDNA sequences. Mol Phylogenet Evol 1999; 11:27-37. [PMID: 10082608 DOI: 10.1006/mpev.1998.0556] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We present an evolutionary analysis of 13 species of Sarcocystis, including 4 newly sequenced species with ruminants as their intermediate host, based on complete small subunit rDNA sequences. Those species with ruminants as their intermediate host form a well-supported clade, and there are at least two major clades within this group, one containing those species forming microcysts and with dogs as their definitive host and the other containing those species forming macrocysts and with cats as their definitive host. Those species with nonruminants as their intermediate host form the paraphyletic sister group to these clades. Most of the species have considerable genotypic differences (differing in more than 100 nucleotide positions), except for S. buffalonis and S. hirsuta. There is a large suite of genotypic differences indicating that those species infecting ruminant and nonruminant hosts have had very different evolutionary histories, and similarly for the felid- and canid-infecting species. Furthermore, the rDNA sequences that represent the different structural regions of the rRNA molecule have very different genotypic behavior within Sarcocystis. The evolution of these regions should be functionally constrained, and their differences can be explained in terms of the importance of the nucleotide sequences to their functions.
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Affiliation(s)
- O J Holmdahl
- Molecular Parasitology Unit, University of Technology, Sydney Westbourne Street, Gore Hill, New South Wales, 2065, Australia
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44
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Sonda S, Fuchs N, Connolly B, Fernandez P, Gottstein B, Hemphill A. The major 36 kDa Neospora caninum tachyzoite surface protein is closely related to the major Toxoplasma gondii surface antigen. Mol Biochem Parasitol 1998; 97:97-108. [PMID: 9879890 DOI: 10.1016/s0166-6851(98)00133-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The tachyzoites and the tissue cysts containing bradyzoites of Neospora caninum and Toxoplasma gondii, respectively, are difficult to distinguish morphologically. Specific antigens have been identified in T. gondii tachyzoites and bradyzoites, some of which are stage-specifically expressed, and different functions have been attributed to some of them. A tachyzoite stage-specifically expressed surface protein is the major surface antigen 1 (SAG1) which has been shown to be involved in host cell attachment and invasion. Previously we have identified a cell surface-associated glycoprotein (p36) in N. caninum tachyzoites. The full length coding sequence of the cDNA coding for p36 was determined, and analysis of the deduced amino acid sequence demonstrated that p36 is closely related to SAG1. p36 is encoded by a single copy gene which produces a transcript of 1.4 kb. Immunogold labeling of resin-embedded parasites using polyclonal antibodies affinity-purified on a recombinant p36 fusion protein expressed in Escherichia coli showed that this protein is located exclusively on the tachyzoite cell surface. As SAG1 in T. gondii, p36 is expressed in the tachyzoite stage, but is absent from bradyzoites. p36 is recognized by antibodies present in sera of cows experimentally infected with N. caninum tachyzoites.
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Affiliation(s)
- S Sonda
- Institute of Parasitology, Faculty of Veterinary Medicine, University of Berne, Switzerland
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45
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Lundén A, Marks J, Maley SW, Innes EA. Cellular immune responses in cattle experimentally infected with Neospora caninum. Parasite Immunol 1998; 20:519-26. [PMID: 9988308 DOI: 10.1046/j.1365-3024.1998.00184.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neospora caninum has recently been identified as an important cause of infectious abortion in cattle. The parasite is closely related to Toxoplasma gondii, but the two species are antigenically distinct. To examine cell proliferative responses and the induction of IFN-gamma in experimentally infected cattle, four 2-4 months old calves were subcutaneously inoculated with N. caninum tachyzoites. Peripheral blood mononuclear cells were collected regularly and stimulated in vitro with a crude lysate of N. caninum or T. gondii tachyzoites. Significant proliferative responses to N. caninum antigen were recorded in all calves from days 4-6 postinoculation. This response was accompanied by production of high levels of IFN-gamma. Although the calves remained seronegative to T. gondii, while seroconverting to N. caninum, stimulation with T. gondii lysate resulted in cell proliferation of a similar magnitude as that obtained using the N. caninum lysate. However, the T. gondii lysate appeared less effective than the N. caninum lysate to stimulate IFN-gamma production. Cells taken from uninfected control animals did not show any significant proliferation to either N. caninum or T. gondii antigen and no IFN-gamma was produced. These results suggest that the two parasites may possess cross-reacting T-cell epitopes, but that the T cells specific for N. caninum may have a different functional capacity. This highlights the need to investigate the antigen specificity and cytokine profile of T cells from infected animals to help understand their role in immunity to N. caninum.
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Affiliation(s)
- A Lundén
- Moredun Research Institute, Pentlands Science Park, Midlothian, Scotland, UK
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46
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Lang-Unnasch N, Reith ME, Munholland J, Barta JR. Plastids are widespread and ancient in parasites of the phylum Apicomplexa. Int J Parasitol 1998; 28:1743-54. [PMID: 9846612 DOI: 10.1016/s0020-7519(98)00136-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Current evidence supports the presence of a non-photosynthetic chloroplast-like organelle in several apicomplexan parasites, including Plasmodium falciparum and Toxoplasma gondii. This apicomplexan organelle, referred to here as the "plastid", may have been acquired through a primary or secondary endosymbiosis of a photosynthetic organism. Alternatively, apicomplexan plastids may have been acquired through several independent endosymbiotic events, as appears to be the case for the acquisition of chloroplasts by dinoflagellates. The likelihood of multiple origins of an apicomplexan plastid is enhanced by the close evolutionary relatedness of apicomplexan and dinoflagellate taxa. In this study, we have tested the hypothesis that apicomplexan plastids are derived from a single ancient ancestor. Two lines of evidence supporting this hypothesis are presented. First, this study supports the widespread presence of plastid DNA in apicomplexan species. Second, the topologies of the phylogenetic trees derived from plastid and nuclear-encoded rRNA gene sequences suggest the co-evolution of the DNAs localised in these two compartments. Taken together, these data support a single ancient lineage for the plastids of parasites in the phylum Apicomplexa.
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Affiliation(s)
- N Lang-Unnasch
- Department of Medicine, University of Alabama at Birmingham 35294-2170, USA.
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47
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Uggla A, Stenlund S, Holmdahl OJ, Jakubek EB, Thebo P, Kindahl H, Björkman C. Oral Neospora caninum inoculation of neonatal calves. Int J Parasitol 1998; 28:1467-72. [PMID: 9770634 DOI: 10.1016/s0020-7519(98)00110-6] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Four calves born to cows seronegative for Neospora caninum were dosed orally within 6 h after birth with tachyzoites of the bovine N. caninum Nc-SweB1 isolate added to colostrum. Two of the calves were dosed via stomach tube and two by feeding bottle. The latter two calves showed transient fever and passed blood-stained diarrhoea 1-2 weeks after inoculation. From 5 weeks after inoculation they developed a significant antibody response which remained high until the calves were euthanised and necropsied at 15 and 19 weeks after inoculation, respectively. The two calves inoculated by stomach tube showed no clinical signs and they remained seronegative throughout the study. At necropsy of the seropositive calves, no pathological lesions were seen, and parasites were not detected by immunohistochemistry. Neospora caninum was not re-isolated in cell culture from the brains of the seropositive calves; however, N. caninum DNA was detected in brain from both of them by PCR. The data suggest that oral infection of N. caninum via colostrum might be a possible route of vertical transmission in newborn calves, in addition to transplacental infection.
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Affiliation(s)
- A Uggla
- Department of Parasitology, National Veterinary Institute, Uppsala, Sweden.
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48
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Harkins D, Clements DN, Maley S, Marks J, Wright S, Esteban I, Innes EA, Buxton D. Western blot analysis of the IgG responses of ruminants infected with Neospora caninum and with Toxoplasma gondii. J Comp Pathol 1998; 119:45-55. [PMID: 9717126 DOI: 10.1016/s0021-9975(98)80070-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The IgG antibody responses of sheep, goats and cattle inoculated subcutaneously with live Neospora caninum tachyzoites of the NC1 isolate were analysed by Western blotting. Antibodies were detected against a wide range of NC1 tachyzoite antigens (6.5 to 80 kDa). The dominant antibody responses were directed against proteins at 36.5-38, 45.5-48.5, 52-53.5, 58, 58.5, 59.5, 60.5, 62, 63.5, 64, 66.5, 67, 67.5, 68.5 and 69.5 kDa, with sera from all three species. These sera were also used to probe blots of Toxoplasma gondii antigen and, while a number of protein bands were recognized, there was no consistency within or between animal species. The IgG antibody responses of sheep, goats and cattle orally infected with T. gondii oocysts of the M3 isolate were analysed by the same methods. Antibodies were detected to a range of S48 toxoplasma tachyzoite antigens (11 to 83 kDa). The dominant antibody responses were directed against proteins at 11, 16-17, 21.5, 22.5-23.5, 26-28.5, 32-35, 49.5, 50.5, 53, 54.5, 60.5 and 61 kDa, with sera from all three species. These sera were also used to probe blots of N. caninum antigen; antibody responses to numerous antigens were detected but showed little consistency within or between animal species.
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Affiliation(s)
- D Harkins
- Moredun Research Institute, International Research Centre, Pentlands Science Park, Liverpool, UK
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49
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Gottstein B, Hentrich B, Wyss R, Thür B, Busato A, Stärk KD, Müller N. Molecular and immunodiagnostic investigations on bovine neosporosis in Switzerland. Int J Parasitol 1998; 28:679-91. [PMID: 9602392 PMCID: PMC7130244 DOI: 10.1016/s0020-7519(98)00006-x] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/1997] [Revised: 12/15/1997] [Accepted: 12/15/1997] [Indexed: 02/07/2023]
Abstract
Neospora caninum has gained considerable attention through its role in the aetiology of bovine abortion. Due to its close phylogenetic relationship with Toxoplasma gondii, respective unequivocal differential diagnosis deserves special consideration. In order to evaluate the diagnostic performance of molecular and immunodiagnostic techniques and to provide insights into the epidemiological significance of bovine neosporosis in Switzerland, we conducted a study on 83 cases of bovine abortion: of these, 24 (29%) foetal brains were positive by Neospora-PCR, six of these foetuses were simultaneously seropositive in Neospora-IFAT and/or somatic antigen-ELISA. Conversely, four (5%) foetal brains were considered positive by Toxoplasma-PCR, two of which were also seropositive in the Toxoplasma-P30-ELISA and/or direct agglutination test. The seroprevalence in 1689 cattle sera obtained from 113 diary farms was 11.5% (95% confidence interval: 9.2-13.8) by Neospora-somatic antigen-ELISA were and 10.7% (95% confidence interval: 8.3-12.6) by Toxoplasma-P30-ELISA. From the same samples, 1.1%, less than statistically expected, were positive in both ELISA. Within selected groups of cow-calf farms, the seroprevalence determined using the Neospora-somatic antigen-ELISA was 14% (95% confidence interval 5.0-23.0) for dams and 15% (95% confidence interval: 3.0-28.0) for offspring calves. Seroprevalences determined by Toxoplasma-P30-ELISA were 8% (95% confidence interval: 4.0-12.0) for dams and 3% (95% confidence interval: 0.3-6.0) for calves. None of the sera gave a positive reaction in both ELISA. Our data indicated that prenatal neosporosis appears as an important cause of bovine abortion in Switzerland.
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Affiliation(s)
- B Gottstein
- Institute of Parasitology, University of Berne, Switzerland.
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50
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Hemphill A, Gajendran N, Sonda S, Fuchs N, Gottstein B, Hentrich B, Jenkins M. Identification and characterisation of a dense granule-associated protein in Neospora caninum tachyzoites. Int J Parasitol 1998; 28:429-38. [PMID: 9559361 DOI: 10.1016/s0020-7519(97)00193-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neospora caninum is an apicomplexan parasite which is morphologically and ultrastructurally very similar to Toxoplasma gondii. In order to identify molecules involved in host cell entry and subsequent modification of the parasitophorous vacuole, a polyclonal antiserum directed against N. caninum tachyzoites was raised in a rabbit. Subcellular fractionation of tachyzoites was performed using the non-ionic detergent Triton-X-114. Membrane fractions were analysed by immunoblotting using the polyclonal antiserum. One of the immunoreactive protein bands had a mol. wt of 33,000 and was subsequently named Nc-p33. Affinity-purified anti-Nc-p33 antibodies were used to characterise this polypeptide using SDS-PAGE, isoelectric focusing, Western blot analysis and immuno-EM. Nc-p33 was found in two isolates of N. caninum (NC-1 and Liverpool), but could not be detected in T. gondii tachyzoites. Immunogold EM revealed that Nc-p33 constituted a dense granule-associated protein, and Western blotting demonstrated that Nc-p33 was most likely identical to the recently described antigen NCDG1. Shortly after invasion, this dense granule protein was targeted to the parasitophorous vacuole membrane, and, at later timepoints after infection, was also found on the parasitophorous vacuolar network. This suggested that Nc-p33 could play a functional role in the modification of the parasitophorous vacuole and its membrane.
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Affiliation(s)
- A Hemphill
- Institute of Parasitology, University of Bern, Switzerland.
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