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Mévélec MN, Lakhrif Z, Dimier-Poisson I. Key Limitations and New Insights Into the Toxoplasma gondii Parasite Stage Switching for Future Vaccine Development in Human, Livestock, and Cats. Front Cell Infect Microbiol 2020; 10:607198. [PMID: 33324583 PMCID: PMC7724089 DOI: 10.3389/fcimb.2020.607198] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 10/19/2020] [Indexed: 12/19/2022] Open
Abstract
Toxoplasmosis is a parasitic disease affecting human, livestock and cat. Prophylactic strategies would be ideal to prevent infection. In a One Health vaccination approach, the objectives would be the prevention of congenital disease in both women and livestock, prevention/reduction of T. gondii tissue cysts in food-producing animals; and oocyst shedding in cats. Over the last few years, an explosion of strategies for vaccine development, especially due to the development of genetic-engineering technologies has emerged. The field of vaccinology has been exploring safer vaccines by the generation of recombinant immunogenic proteins, naked DNA vaccines, and viral/bacterial recombinants vectors. These strategies based on single- or few antigens, are less efficacious than recombinant live-attenuated, mostly tachyzoite T. gondii vaccine candidates. Reflections on the development of an anti-Toxoplasma vaccine must focus not only on the appropriate route of administration, capable of inducing efficient immune response, but also on the choice of the antigen (s) of interest and the associated delivery systems. To answer these questions, the choice of the animal model is essential. If mice helped in understanding the protection mechanisms, the data obtained cannot be directly transposed to humans, livestock and cats. Moreover, effectiveness vaccines should elicit strong and protective humoral and cellular immune responses at both local and systemic levels against the different stages of the parasite. Finally, challenge protocols should use the oral route, major natural route of infection, either by feeding tissue cysts or oocysts from different T. gondii strains. Effective Toxoplasma vaccines depend on our understanding of the (1) protective host immune response during T. gondii invasion and infection in the different hosts, (2) manipulation and modulation of host immune response to ensure survival of the parasites able to evade and subvert host immunity, (3) molecular mechanisms that define specific stage development. This review presents an overview of the key limitations for the development of an effective vaccine and highlights the contributions made by recent studies on the mechanisms behind stage switching to offer interesting perspectives for vaccine development.
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Affiliation(s)
| | - Zineb Lakhrif
- Team BioMAP, Université de Tours, INRAE, ISP, Tours, France
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Castaño P, Fuertes M, Fernández M, Ferreras MC, Ferre I, Ortega-Mora LM, Pérez V, Benavides J. Macrophages and T Lymphocytes in the Ovine Placenta After Experimental Infection With Toxoplasma gondii. Vet Pathol 2020; 57:545-549. [PMID: 32452287 DOI: 10.1177/0300985820923987] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Early abortion in ovine toxoplasmosis has had limited investigation. This study evaluated the immune response in the placenta of sheep orally infected with Toxoplasma gondii and euthanized between 2 and 4 weeks postinfection. Toxoplasma infection of the placenta was only found at 4 weeks after infection. Parasitic debris in foci of necrosis were immunolabeled in the maternal caruncle, whereas well-preserved intracellular parasitic vacuole-like structures were found in trophoblasts of fetal cotyledon. Early abortions had increased macrophages in caruncular septa, whereas in later abortions the placentas containing the parasite had an increase of T lymphocytes and macrophages mainly in the fetal cotyledons. This study suggests that the immune response in both the fetal and maternal compartments of the placenta may contribute to the pathogenesis of ovine toxoplasmosis and that these responses differ between early and late presentations of the disease.
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Affiliation(s)
- Pablo Castaño
- Instituto de Ganadería de Montaña (CSIC-Universidad de León), Grulleros, León, Spain
| | - Miguel Fuertes
- Instituto de Ganadería de Montaña (CSIC-Universidad de León), Grulleros, León, Spain
| | - Miguel Fernández
- Instituto de Ganadería de Montaña (CSIC-Universidad de León), Grulleros, León, Spain.,Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana, León, Spain
| | - M Carmen Ferreras
- Instituto de Ganadería de Montaña (CSIC-Universidad de León), Grulleros, León, Spain.,Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana, León, Spain
| | | | | | - Valentín Pérez
- Instituto de Ganadería de Montaña (CSIC-Universidad de León), Grulleros, León, Spain.,Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana, León, Spain
| | - Julio Benavides
- Instituto de Ganadería de Montaña (CSIC-Universidad de León), Grulleros, León, Spain
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Castaño P, Fernández M, Regidor-Cerrillo J, Fuertes M, Horcajo P, Ferre I, Ferreras MC, Ortega-Mora LM, Pérez V, Benavides J. Peripheral and placental immune responses in sheep after experimental infection with Toxoplasma gondii at the three terms of gestation. Vet Res 2019; 50:66. [PMID: 31533826 PMCID: PMC6751581 DOI: 10.1186/s13567-019-0681-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 08/06/2019] [Indexed: 12/21/2022] Open
Abstract
Although it is known that gestation could influence the clinical course of ovine toxoplasmosis, the precise effect of the term of gestation when sheep are infected are yet mostly unknown. The aim of this study was to evaluate the peripheral and placental immune responses developed in pregnant sheep after experimental infection with Toxoplasma gondii at different times of gestation. Thirty-six pregnant sheep were allocated in different groups, orally inoculated with sporulated oocysts of T. gondii at early, mid and late gestation and culled within 30 days post-infection. The peripheral humoral and cytokine responses were evaluated, as well as the transcription of cytokines at the placenta. Serological analysis revealed that, regardless the term of gestation when infected, specific IgG against T. gondii were detected from day 8 post-infection and there was an early peripheral release of IFN-γ at the first week post-infection followed by a short peak of IL10 and TNF-α at the second week post-infection. There were no significant differences in this response between infected groups. At the placenta, a similar increase in transcription of IFN-γ, and TNF-α was found at the three terms of gestation, while IL-4 increased mainly at the first and second terms and IL-10 transcription was higher at the last term. While these findings show that both Th1 and Th2 cytokines play a key role in the pathogenesis of ovine toxoplasmosis and that placental and peripheral immune responses do not closely correlate, there seems to be no clear modulation of these responses along the gestation.
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Affiliation(s)
- Pablo Castaño
- Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346, León, Spain
| | - Miguel Fernández
- Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346, León, Spain
| | - Javier Regidor-Cerrillo
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Miguel Fuertes
- Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346, León, Spain
| | - Pilar Horcajo
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Ignacio Ferre
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - M Carmen Ferreras
- Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346, León, Spain
| | - Luis Miguel Ortega-Mora
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Valentín Pérez
- Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346, León, Spain
| | - Julio Benavides
- Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346, León, Spain.
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Stelzer S, Basso W, Benavides Silván J, Ortega-Mora L, Maksimov P, Gethmann J, Conraths F, Schares G. Toxoplasma gondii infection and toxoplasmosis in farm animals: Risk factors and economic impact. Food Waterborne Parasitol 2019; 15:e00037. [PMID: 32095611 PMCID: PMC7033994 DOI: 10.1016/j.fawpar.2019.e00037] [Citation(s) in RCA: 180] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/25/2019] [Accepted: 01/30/2019] [Indexed: 12/23/2022] Open
Abstract
The protozoan parasite Toxoplasma gondii is a zoonotic parasite that can be transmitted from animals to humans. Felids, including domestic cats, are definitive hosts that can shed oocysts with their feces. In addition to infections that occur by accidental oral uptake of food or water contaminated with oocysts, it is assumed that a large proportion of affected humans may have become infected by consuming meat or other animal products that contained infective parasitic stages of T. gondii. Since farm animals represent a direct source of infection for humans, but also a possible reservoir for the parasite, it is important to control T. gondii infections in livestock. Moreover, T. gondii may also be pathogenic to livestock where it could be responsible for considerable economic losses in some regions and particular farming systems, e.g. in areas where the small ruminant industry is relevant. This review aims to summarize actual knowledge on the prevalence and effects of infections with T. gondii in the most important livestock species and on the effects of toxoplasmosis on livestock. It also provides an overview on potential risk factors favoring infections of livestock with T. gondii. Knowledge on potential risk factors is prerequisite to implement effective biosecurity measures on farms to prevent T. gondii infections. Risk factors identified by many studies are cat-related, but also those associated with a potential contamination of fodder or water, and with access to a potentially contaminated environment. Published information on the costs T. gondii infections cause in livestock production, is scarce. The most recent peer reviewed reports from Great Britain and Uruguay suggest annual cost of about 5-15 million US $ per country. Since these estimates are outdated, future studies are needed to estimate the present costs due to toxoplasmosis in livestock. Further, the fact that T. gondii infections in livestock may affect human health needs to be considered and the respective costs should also be estimated, but this is beyond the scope of this article.
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Affiliation(s)
- S. Stelzer
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald - Insel Riems, Germany
| | - W. Basso
- Institute of Parasitology, University of Bern, Länggassstrasse 122, 3012 Bern, Switzerland
| | - J. Benavides Silván
- Instituto de Ganadería de Montaña (CSIC-Universidad de León) Grulleros, 24346 León, Spain
| | - L.M. Ortega-Mora
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
| | - P. Maksimov
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald - Insel Riems, Germany
| | - J. Gethmann
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald - Insel Riems, Germany
| | - F.J. Conraths
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald - Insel Riems, Germany
| | - G. Schares
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald - Insel Riems, Germany
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Xia N, Zhou T, Liang X, Ye S, Zhao P, Yang J, Zhou Y, Zhao J, Shen B. A Lactate Fermentation Mutant of Toxoplasma Stimulates Protective Immunity Against Acute and Chronic Toxoplasmosis. Front Immunol 2018; 9:1814. [PMID: 30147689 PMCID: PMC6096001 DOI: 10.3389/fimmu.2018.01814] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 07/23/2018] [Indexed: 12/20/2022] Open
Abstract
Toxoplasma gondii is an important zoonotic pathogen infecting one-third of the world’s population and numerous animals, causing significant healthcare burden and socioeconomic problems. Vaccination is an efficient way to reduce global sero-prevalence, however, ideal vaccines are not yet available. We recently discovered that the Toxoplasma mutant lacking both lactate dehydrogenases LDH1 and LDH2 (Δldh) grew well in vitro but was unable to propagate in mice, making it a good live vaccine candidate. Here, we tested the protection efficacy of ME49 Δldh using a mouse model. Vaccinated mice were efficiently protected from the lethal challenge of a variety of wild-type strains, including type 1 strain RH, type 2 strain ME49, type 3 strain VEG, and a field isolate of Chinese 1. The protection efficacies of a single vaccination were nearly 100% for most cases and it worked well against the challenges of both tachyzoites and tissue cysts. Re-challenging parasites were unable to propagate in vaccinated mice, nor did they make tissue cysts. High levels of Toxoplasma-specific IgG were produced 30 days after immunization and stayed high during the whole tests (at least 125 days). However, passive immunization of naïve mice with sera from vaccinated mice did reduce parasite propagation, but the overall protection against parasite infections was rather limited. On the other hand, Δldh immunization evoked elevated levels of Th1 cytokines like INF-γ and IL-12, at early time points. In addition, splenocytes extracted from immunized mice were able to induce quick and robust INF-γ and other pro-inflammatory cytokine production upon T. gondii antigen stimulation. Together these results suggest that cellular immune responses are the main contributors to the protective immunity elicited by Δldh vaccination, and humoral immunity also contributes partially. We also generated uracil auxotrophic mutants in ME49 and compared their immune protection efficiencies to the Δldh mutants. The results showed that these two types of mutants have similar properties as live vaccine candidates. Taken together, these results suggest that mutants lacking LDH were severely attenuated in virulence but were able to induce strong anti-toxoplasma immune responses, therefore are good candidates for live vaccines.
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Affiliation(s)
- Ningbo Xia
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Taifang Zhou
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Xiaohan Liang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Shu Ye
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Pengfei Zhao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Jichao Yang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Yanqin Zhou
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Junlong Zhao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,Hubei Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.,Key Laboratory of Preventive Medicine in Hubei Province, Wuhan, China
| | - Bang Shen
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Medicine in Hubei Province, Wuhan, China
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6
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Verhelst D, De Craeye S, Entrican G, Dorny P, Cox E. Parasite distribution and associated immune response during the acute phase of Toxoplasma gondii infection in sheep. BMC Vet Res 2014; 10:293. [PMID: 25511864 PMCID: PMC4279818 DOI: 10.1186/s12917-014-0293-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 12/02/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In many countries, Toxoplasma gondii (T. gondii) is a major cause of reproductive disorders and abortions in the sheep industry, and therefore responsible for important financial and economic losses. In addition, undercooked infected lamb is an important risk factor for human toxoplasmosis. In the present study, the initial phase of the infection was investigated: the parasite's entry site, the subsequent distribution of the parasite and the host-immune response. RESULTS Parasite DNA was already detected in the cranial small intestinal mucosa the first days after oral infection with T. gondii tissue cysts. Simultaneously, high IFN-gamma and IL-12 responses were induced mainly in the mesenteric lymph nodes. The emergence of IgG1 (at 8dpi), and IgG2 (at 11 dpi) was accompanied by a decrease or even disappearance of the IFN-gamma and IL-12 response in the Peyers' patches (PP), PBMC's and popliteal LN's. Meanwhile the parasite DNA could be recovered from most mucosal and systemic tissues to become undetectable in the small intestine, popliteal LN, PBMC and spleen 3 weeks pi. CONCLUSIONS Our results indicate that parasites enter the cranial small intestine the first days after infection and that after an increase the first two weeks after infection, the parasite DNA levels in the intestine drop below the detection limit three weeks after infection. This coincides with an increase in parastic-specific serum IgG1 and IgG2 and a decrease of the antigen-specific IFN-gamma response in PP, PBMC and popliteal LN. We suggest a role for IFN-gamma and IL-12 in controlling the infection.
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Affiliation(s)
- Delfien Verhelst
- Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
| | - Stéphane De Craeye
- National Reference Laboratory for Toxoplasmosis, Operational Direction Communicable and Infectious Diseases, Scientific Institute of Public Health, Brussels, Belgium.
| | - Gary Entrican
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Midlothian, Penicuik, EH26 0PZ, Scotland, UK.
| | - Pierre Dorny
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium. .,Laboratory of Parasitology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
| | - Eric Cox
- Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
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Castaño P, Fuertes M, Ferre I, Fernández M, Ferreras MDC, Moreno-Gonzalo J, González-Lanza C, Katzer F, Regidor-Cerrillo J, Ortega-Mora LM, Pérez V, Benavides J. Placental thrombosis in acute phase abortions during experimental Toxoplasma gondii infection in sheep. Vet Res 2014; 45:9. [PMID: 24475786 PMCID: PMC3931317 DOI: 10.1186/1297-9716-45-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 01/16/2014] [Indexed: 02/08/2023] Open
Abstract
After oral administration of ewes during mid gestation with 2000 freshly prepared sporulated oocysts of T. gondii isolate M4, abortions occurred between days 7 and 11 in 91.6% of pregnant and infected ewes. Afterwards, a further infection was carried out at late gestation in another group of sheep with 500 sporulated oocysts. Abortions happened again between days 9 and 11 post infection (pi) in 58.3% of the infected ewes. Classically, abortions in natural and experimental ovine toxoplasmosis usually occur one month after infection. Few experimental studies have reported the so-called acute phase abortions as early as 7 to 14 days after oral inoculation of oocysts, and pyrexia was proposed to be responsible for abortion, although the underline mechanism was not elucidated. In the present study, all placentas analysed from ewes suffering acute phase abortions showed infarcts and thrombosis in the caruncullar villi of the placentomes and ischemic lesions (periventricular leukomalacia) in the brain of some foetuses. The parasite was identified by PCR in samples from some placentomes of only one sheep, and no antigen was detected by immunohistochemical labelling. These findings suggest that the vascular lesions found in the placenta, and the consequent hypoxic damage to the foetus, could be associated to the occurrence of acute phase abortions. Although the pathogenesis of these lesions remains to be determined, the infectious dose or virulence of the isolate may play a role in their development.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Julio Benavides
- Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Grulleros, 24346 León, Spain.
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Abstract
SUMMARYCongenital infection with Toxoplasma gondii is an important cause of abortion in sheep worldwide. The cat is the definitive host of the parasite, and infected cats may shed millions of oocysts in their faeces resulting in extensive environmental contamination and an important source of infection for grazing herbivorous animals. Studies looking at development of specific antibodies in sheep, as an indicator of exposure to T. gondii, have shown that there is an increase in seroprevalence associated with age indicating that most infections in sheep occur following birth. The stage of gestation when transplacental transmission of T. gondii to the developing foetus occurs is critical in determining the clinical outcome. The importance of endogenous transplacental transmission in persistently infected ewes and its clinical importance is a subject of current debate. Ewes infected prior to mating develop immune responses that help protect against disease in a subsequent pregnancy and also against experimental challenge administered during pregnancy. Both innate and adaptive immune responses are activated following T. gondii infection and experiments involving the chronic cannulation of peripheral lymph nodes in sheep have allowed the dynamics of the immune responses to be analysed in real time. A live vaccine, Toxovax® is the only commercially available vaccine worldwide to protect against congenital toxoplasmosis.
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9
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Toxoplasmosis in sheep—The last 20 years. Vet Parasitol 2009; 163:1-14. [DOI: 10.1016/j.vetpar.2009.02.026] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 02/23/2009] [Accepted: 02/27/2009] [Indexed: 11/22/2022]
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10
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Innes EA, Bartley PM, Maley S, Katzer F, Buxton D. Veterinary vaccines against Toxoplasma gondii. Mem Inst Oswaldo Cruz 2009; 104:246-51. [DOI: 10.1590/s0074-02762009000200018] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 12/03/2008] [Indexed: 11/22/2022] Open
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Innes EA, Bartley PM, Maley SW, Wright SE, Buxton D. Comparative host–parasite relationships in ovine toxoplasmosis and bovine neosporosis and strategies for vaccination. Vaccine 2007; 25:5495-503. [PMID: 17367899 DOI: 10.1016/j.vaccine.2007.02.044] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 01/24/2007] [Accepted: 02/07/2007] [Indexed: 10/23/2022]
Abstract
Toxoplasma gondii and Neospora caninum are important causes of reproductive loss in ruminant species worldwide. Both parasites cause disease during pregnancy that may result in foetal death or birth of live congenitally infected offspring. T. gondii is also an important human pathogen with the main risk groups including pregnant women and immuno-compromised individuals, although clinical disease has also been observed in outbreaks among immuno-competent people. While the two parasites are closely related there are distinct differences between the two in their interactions with different host species and subsequent clinical outcome. This paper discusses the respective host-parasite relationships in ovine toxoplasmosis and bovine neosporosis and how the immune response may be host-protective, parasite-protective or contribute to disease pathogenesis, and how this knowledge may help in the development of more effective and targeted vaccination strategies.
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Affiliation(s)
- Elisabeth A Innes
- Moredun Research Institute, Pentlands Science Park, Edinburgh EH26 OPZ, United Kingdom.
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12
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Innes EA, Vermeulen AN. Vaccination as a control strategy against the coccidial parasitesEimeria,ToxoplasmaandNeospora. Parasitology 2007; 133 Suppl:S145-68. [PMID: 17274844 DOI: 10.1017/s0031182006001855] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The protozoan parasitesEimeriaspp.Toxoplasma gondiiandNeospora caninumare significant causes of disease in livestock worldwide andT. gondiiis also an important human pathogen. Drugs have been used with varying success to help control aspects of these diseases and commercial vaccines are available for all three groups of parasites. However, there are issues with increasing development of resistance to many of the anti-coccidial drugs used to help control avian eimeriosis and public concerns about the use of drugs in food animals. In addition there are no drugs available that can act against the tissue cyst stage of eitherT. gondiiorN. caninumand thus cure animals or people of infection. All three groups of parasites multiply within the cells of their host species and therefore cell mediated immune mechanisms are thought to be an important component of host protective immunity. Successful vaccination strategies for bothEimeriaandToxoplasmahave relied on using a live vaccination approach using attenuated parasites which allows correct processing and presentation of antigen to the host immune system to stimulate appropriate cell mediated immune responses. However, live vaccines can have problems with safety, short shelf-life and large-scale production; therefore there is continued interest in devising new vaccines using defined recombinant antigens. The major challenges in devising novel vaccines are to select relevant antigens and then present them to the immune system in an appropriate manner to enable the induction of protective immune responses. With all three groups of parasites, vaccine preparations comprising antigens from the different life cycle stages may also be advantageous. In the case ofEimeriaparasites there are also problems with strain-specific immunity therefore a cocktail of antigens from different parasite strains may be required. Improving our knowledge of the different parasite transmission routes, host-parasite relationships, disease pathogenesis and determining the various roles of the host immune response being at times host-protective, parasite protective and in causing immunopathology will help to tailor a vaccination strategy against a particular disease target. This paper discusses current vaccination strategies to help combat infections withEimeria,ToxoplasmaandNeosporaand recent research looking towards developing new vaccine targets and approaches.
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Affiliation(s)
- E A Innes
- Moredun Research Institute, Pentlands Science Park, Edinburgh EH26 OPZ, UK.
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13
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Wattegedera S, Sills K, Howard CJ, Hope JC, McInnes CJ, Entrican G. Variability in cytokine production and cell proliferation by mitogen-activated ovine peripheral blood mononuclear cells: modulation by interleukin (IL)-10 and IL-12. Vet Immunol Immunopathol 2004; 102:67-76. [PMID: 15451616 DOI: 10.1016/j.vetimm.2004.06.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Revised: 06/08/2004] [Accepted: 06/14/2004] [Indexed: 11/19/2022]
Abstract
T-cell reactivity is typically measured by cell proliferation and/or production of cytokines in response to antigenic/mitogenic stimulation. The choice of assays is more limited in ruminants than rodents, and complicated by the variability inherent in outbred populations. We have measured proliferation and production of interferon-gamma (IFN-gamma) by peripheral blood mononuclear cells (PBMC) from 24 sheep, and compared the responses between sheep, within sheep over several sample points, and also drawn comparisons between the two assays. PBMC derived from different sheep varied by as much as ten-fold in both proliferation and IFN-gamma production, though not necessarily at the same sample time. Thus, there was a poor correlation between the two assays and also considerable variation in the responses from the same animal at different time points. Both parameters could be modulated by exogenous recombinant ovine interleukin (IL)-10 and IL-12, but we were unable to correlate IFN-gamma production with endogenous cytokine production in the assays. These data highlight the importance of assay selection for the measurement of immune responsiveness and also demonstrate the variation that can be expected between sheep and over time.
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Affiliation(s)
- S Wattegedera
- Moredun Research Institute, International Research Centre, Pentlands Science Park, Bush Loan, Edinburgh, EH26 0PZ, UK.
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14
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Abstract
Toxoplasma gondii is a protozoan parasite that can infect all warm-blooded animals. Sheep and cattle show different susceptibilities to T. gondii infection. Primary infection in pregnant sheep can result in abortion or the birth of weak lambs but they are then protected against further challenge by the development of an effective immunity. Cattle on the other hand can be readily infected, but abortion or perinatal mortality have not been recorded. The evidence suggests that cattle develop a more effective immune response to T. gondii infection than sheep. Potential mechanisms to explain these differences are discussed in this paper.
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MESH Headings
- Abortion, Veterinary/etiology
- Abortion, Veterinary/immunology
- Abortion, Veterinary/parasitology
- Animals
- Antibodies, Protozoan/biosynthesis
- Cattle
- Cattle Diseases/etiology
- Cattle Diseases/immunology
- Cattle Diseases/parasitology
- Cysts/parasitology
- Female
- Immunity, Cellular
- Pregnancy
- Pregnancy Complications, Parasitic/etiology
- Pregnancy Complications, Parasitic/immunology
- Pregnancy Complications, Parasitic/veterinary
- Sheep
- Sheep Diseases/etiology
- Sheep Diseases/immunology
- Sheep Diseases/parasitology
- Species Specificity
- Toxoplasma/immunology
- Toxoplasma/isolation & purification
- Toxoplasma/pathogenicity
- Toxoplasmosis, Animal/complications
- Toxoplasmosis, Animal/etiology
- Toxoplasmosis, Animal/immunology
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15
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Innes EA. Toxoplasmosis: comparative species susceptibility and host immune response. Comp Immunol Microbiol Infect Dis 1997; 20:131-8. [PMID: 9208198 DOI: 10.1016/s0147-9571(96)00038-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The protozoan parasite Toxoplasma gondii is capable of infecting all warm blooded animals; however, the consequences of infection are very variable between different species of animal. Marsupials and New World monkeys, which have evolved largely separately from the cat, the definitive host of the parasite, are among the most vulnerable species where infection with T. gondii can prove fatal. In more resistant species such as humans and sheep, infection is generally unapparent, provoking only mild symptoms; thereafter the host remains infected for life. However, when the immune system is compromised, such as in the immunologically immature fetus, infection with the parasite can have very serious consequences. Much of the work examining host immune responses has been done using experimentally infected mice. While there are many advantages in using this experimental model, care should be taken in extrapolating results from mice to other species. Mice are extremely vulnerable to the consequences of infection with T. gondii., and their use to further our understanding of congenital toxoplasmosis may not be ideal, as fetal infection can occur in successive pregnancies. This is not the case in rats or sheep; they are more resistant to the disease and therefore may provide a more relevant model for human congenital toxoplasmosis. Studies of host immune responses have emphasised the importance of the cytokine interferon gamma (IFN gamma) in resistance to T. gondii. The efficiency of induction of this cytokine may be critical for determining the outcome of the host-parasite relationship.
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Affiliation(s)
- E A Innes
- Moredun Research Institute, Edinburgh, U.K
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16
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Coughlan SN, Saman E, Jacobs D, Mercier C, Cesbron-Delauw MF, Trees AJ. Cellular and humoral immune responses to recombinant antigens in sheep infected with Toxoplasma gondii. Parasite Immunol 1995; 17:465-8. [PMID: 8552415 DOI: 10.1111/j.1365-3024.1995.tb00916.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Immune responses to recombinant fragments of the Toxoplasma gondii antigens ROP2 and GRA2 were investigated in sheep naturally and experimentally infected with T. gondii oocysts. Specific serum antibodies to C-terminal fragments were detected by ELISA. Cell-mediated responses in peripheral blood mononuclear cells were demonstrated by proliferation and interferon-gamma production following in vitro stimulation with the ROP2 fragment. This data indicates the presence of epitopes for sheep B cells in the recombinant GRA2 fragment and for both B and T cells in the ROP2 fragment.
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Affiliation(s)
- S N Coughlan
- Department of Veterinary Parasitology, Liverpool School of Tropical Medicine, UK
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