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Clinical Microbiology Reviews Apr 2012The apicomplexan parasite Toxoplasma gondii was discovered a little over 100 years ago, but knowledge of its biological life cycle and its medical importance has grown... (Review)
Review
The apicomplexan parasite Toxoplasma gondii was discovered a little over 100 years ago, but knowledge of its biological life cycle and its medical importance has grown in the last 40 years. This obligate intracellular parasite was identified early as a pathogen responsible for congenital infection, but its clinical expression and the importance of reactivations of infections in immunocompromised patients were recognized later, in the era of organ transplantation and HIV infection. Recent knowledge of host cell-parasite interactions and of parasite virulence has brought new insights into the comprehension of the pathophysiology of infection. In this review, we focus on epidemiological and diagnostic aspects, putting them in perspective with current knowledge of parasite genotypes. In particular, we provide critical information on diagnostic methods according to the patient's background and discuss the implementation of screening tools for congenital toxoplasmosis according to health policies.
Topics: Humans; Prevalence; Toxoplasma; Toxoplasmosis
PubMed: 22491772
DOI: 10.1128/CMR.05013-11 -
Parasites & Vectors May 2015Toxoplasmosis, caused by the obligate intracellular protozoan Toxoplasma gondii, is an important zoonosis with medical and veterinary importance worldwide. The disease... (Review)
Review
Toxoplasmosis, caused by the obligate intracellular protozoan Toxoplasma gondii, is an important zoonosis with medical and veterinary importance worldwide. The disease is mainly contracted by ingesting undercooked or raw meat containing viable tissue cysts, or by ingesting food or water contaminated with oocysts. The diagnosis and genetic characterization of T. gondii infection is crucial for the surveillance, prevention and control of toxoplasmosis. Traditional approaches for the diagnosis of toxoplasmosis include etiological, immunological and imaging techniques. Diagnosis of toxoplasmosis has been improved by the emergence of molecular technologies to amplify parasite nucleic acids. Among these, polymerase chain reaction (PCR)-based molecular techniques have been useful for the genetic characterization of T. gondii. Serotyping methods based on polymorphic polypeptides have the potential to become the choice for typing T. gondii in humans and animals. In this review, we summarize conventional non-DNA-based diagnostic methods, and the DNA-based molecular techniques for the diagnosis and genetic characterization of T. gondii. These techniques have provided foundations for further development of more effective and accurate detection of T. gondii infection. These advances will contribute to an improved understanding of the epidemiology, prevention and control of toxoplasmosis.
Topics: Animals; Diagnostic Tests, Routine; Humans; Toxoplasma; Toxoplasmosis
PubMed: 26017718
DOI: 10.1186/s13071-015-0902-6 -
Current Biology : CB Jul 2018Putting cat lovers on notice: Toxoplasma gondii is here to control your brain…or is it? Kochanowsky and Koshy shine the spotlight on this notorious pathogen.
Putting cat lovers on notice: Toxoplasma gondii is here to control your brain…or is it? Kochanowsky and Koshy shine the spotlight on this notorious pathogen.
Topics: Animals; Host-Parasite Interactions; Humans; Life History Traits; Toxoplasma; Toxoplasmosis; Toxoplasmosis, Animal
PubMed: 30040931
DOI: 10.1016/j.cub.2018.05.035 -
Microbiological Research Oct 2019T. gondii is a major opportunistic pathogen chronically infecting nearly one third of the world's population. Due to the high infection and mortality rates in... (Review)
Review
T. gondii is a major opportunistic pathogen chronically infecting nearly one third of the world's population. Due to the high infection and mortality rates in immunocompromised patients and newborns, the extent or magnitude of T. gondii pathogenesis is determined mainly by host-pathogen interactions. T. gondii utilizes specialized secretory proteins to modify host cellular factors and facilitate invasion and replication. This review provides update on the recent progress in this field of research with particular emphasis on the T. gondii secretory proteins and their role in invasion and pathogenesis.
Topics: Animals; Host-Parasite Interactions; Humans; Life Cycle Stages; Protein Transport; Protozoan Proteins; Toxoplasma; Toxoplasmosis
PubMed: 31421715
DOI: 10.1016/j.micres.2019.06.003 -
Frontiers in Cellular and Infection... 2019is an intracellular protozoan parasite of global importance that can remarkably infect, survive, and replicate in nearly all mammalian cells. Notably, 110 years after... (Review)
Review
is an intracellular protozoan parasite of global importance that can remarkably infect, survive, and replicate in nearly all mammalian cells. Notably, 110 years after its discovery, Toxoplasmosis is still a neglected parasitic infection. Although most human infections with are mild or asymptomatic, infection can result in life-threatening disease in immunocompromised individuals and in the developing fetus due to congenital infection, underscoring the role of the host immune system in controlling the parasite. Recent evidence indicates that elicits a robust innate immune response during infection. Interestingly, however, has evolved strategies to successfully bypass or manipulate the immune system and establish a life-long infection in infected hosts. In particular, manipulates host immunity through the control of host gene transcription and dysregulation of signaling pathways that result in modulation of cell adhesion and migration, secretion of immunoregulatory cytokines, production of microbicidal molecules, and apoptosis. Many of these host-pathogen interactions are governed by parasite effector proteins secreted from the apical secretory organelles, including the rhoptries and dense granules. Here, we review recent findings on mechanisms by which evades host innate immunity, with a focus on parasite evasion of the human innate immune system.
Topics: Host-Pathogen Interactions; Humans; Immune Evasion; Immunity, Innate; Toxoplasma; Toxoplasmosis
PubMed: 31041194
DOI: 10.3389/fcimb.2019.00103 -
Clinical Microbiology Reviews Apr 1998Infections by the protozoan parasite Toxoplasma gondii are widely prevalent world-wide in animals and humans. This paper reviews the life cycle; the structure of... (Review)
Review
Infections by the protozoan parasite Toxoplasma gondii are widely prevalent world-wide in animals and humans. This paper reviews the life cycle; the structure of tachyzoites, bradyzoites, oocysts, sporocysts, sporozoites and enteroepithelial stages of T. gondii; and the mode of penetration of T. gondii. The review provides a detailed account of the biology of tissue cysts and bradyzoites including in vivo and in vitro development, methods of separation from host tissue, tissue cyst rupture, and relapse. The mechanism of in vivo and in vitro stage conversion from sporozoites to tachyzoites to bradyzoites and from bradyzoites to tachyzoites to bradyzoites is also discussed.
Topics: Animals; Cells, Cultured; Host-Parasite Interactions; Humans; Immunohistochemistry; Life Cycle Stages; Microscopy, Electron; Toxoplasma; Toxoplasmosis; Toxoplasmosis, Animal
PubMed: 9564564
DOI: 10.1128/CMR.11.2.267 -
The Journal of Clinical Investigation Jul 2020Toxoplasma gondii is an incredibly successful parasite owing in part to its ability to persist within cells for the life of the host. Remarkably, at least 350 host... (Review)
Review
Toxoplasma gondii is an incredibly successful parasite owing in part to its ability to persist within cells for the life of the host. Remarkably, at least 350 host species of T. gondii have been described to date, and it is estimated that 30% of the global human population is chronically infected. The importance of T. gondii in human health was made clear with the first reports of congenital toxoplasmosis in the 1940s. However, the AIDS crisis in the 1980s revealed the prevalence of chronic infection, as patients presented with reactivated chronic toxoplasmosis, underscoring the importance of an intact immune system for parasite control. In the last 40 years, there has been tremendous progress toward understanding the biology of T. gondii infection using rodent models, human cell experimental systems, and clinical data. However, there are still major holes in our understanding of T. gondii biology, including the genes controlling parasite development, the mechanisms of cell-intrinsic immunity to T. gondii in the brain and muscle, and the long-term effects of infection on host homeostasis. The need to better understand the biology of chronic infection is underscored by the recent rise in ocular disease associated with emerging haplotypes of T. gondii and our lack of effective treatments to sterilize chronic infection. This Review discusses the cell types and molecular mediators, both host and parasite, that facilitate persistent T. gondii infection. We highlight the consequences of chronic infection for tissue-specific pathology and identify open questions in this area of host-Toxoplasma interactions.
Topics: Animals; Disease Models, Animal; History, 20th Century; History, 21st Century; Humans; Toxoplasma; Toxoplasmosis
PubMed: 32609097
DOI: 10.1172/JCI136226 -
Cell Host & Microbe Nov 2020Apicomplexan parasites cause major human disease and food insecurity. They owe their considerable success to highly specialized cell compartments and structures. These...
Apicomplexan parasites cause major human disease and food insecurity. They owe their considerable success to highly specialized cell compartments and structures. These adaptations drive their recognition, nondestructive penetration, and elaborate reengineering of the host's cells to promote their growth, dissemination, and the countering of host defenses. The evolution of unique apicomplexan cellular compartments is concomitant with vast proteomic novelty. Consequently, half of apicomplexan proteins are unique and uncharacterized. Here, we determine the steady-state subcellular location of thousands of proteins simultaneously within the globally prevalent apicomplexan parasite Toxoplasma gondii. This provides unprecedented comprehensive molecular definition of these unicellular eukaryotes and their specialized compartments, and these data reveal the spatial organizations of protein expression and function, adaptation to hosts, and the underlying evolutionary trajectories of these pathogens.
Topics: Apicomplexa; Biological Evolution; Epitopes; Host-Pathogen Interactions; Humans; Proteome; Proteomics; Protozoan Proteins; Toxoplasma
PubMed: 33053376
DOI: 10.1016/j.chom.2020.09.011 -
Frontiers in Cellular and Infection... 2019is a successful protozoan parasite that cycles between definitive felid hosts and a broad range of intermediate hosts, including rodents and humans. Within intermediate... (Review)
Review
is a successful protozoan parasite that cycles between definitive felid hosts and a broad range of intermediate hosts, including rodents and humans. Within intermediate hosts, this obligate intracellular parasite invades the small intestine, inducing an inflammatory response. infects infiltrating immune cells, using them to spread systemically and reach tissues amenable to chronic infection. An intact immune system is necessary to control life-long chronic infection. Chronic infection is characterized by formation of parasite cysts, which are necessary for survival through the gastrointestinal tract of the next host. Thus, must evade sterilizing immunity, but still rely on the host's immune response for survival and transmission. To do this, exploits a central cost-benefit tradeoff in immunity: the need to escalate inflammation for pathogen clearance vs. the need to limit inflammation-induced bystander damage. What are the consequences of sustained inflammation on host biology? Many studies have focused on aspects of the immune response that directly target growth and survival, commonly referred to as "resistance mechanisms." However, it is becoming clear that a parallel arm of the immune response has evolved to mitigate damage caused by the parasite directly (for example, egress-induced cell death) or bystander damage due to the inflammatory response (for example, reactive nitrogen species, degranulation). These so-called "disease tolerance" mechanisms promote tissue function and host survival without directly targeting the pathogen. Here we review changes to host metabolism, tissue structure, and immune function that point to disease tolerance mechanisms during infection. We explore the impact tolerance programs have on the health of the host and parasite biology.
Topics: Animals; Disease Resistance; Host-Parasite Interactions; Humans; Immune Tolerance; Immunity, Innate; Inflammation; Toxoplasma; Toxoplasmosis
PubMed: 31245299
DOI: 10.3389/fcimb.2019.00185 -
Molecular Microbiology May 2021Toxoplasma and other apicomplexan parasites undergo a unique form of cellular locomotion referred to as "gliding motility." Gliding motility is crucial for parasite... (Review)
Review
Toxoplasma and other apicomplexan parasites undergo a unique form of cellular locomotion referred to as "gliding motility." Gliding motility is crucial for parasite survival as it powers tissue dissemination, host cell invasion and egress. Distinct environmental cues lead to activation of gliding motility and have become a prominent focus of recent investigation. Progress has been made toward understanding what environmental cues are sensed and how these signals are transduced in order to regulate the machinery and cellular events powering gliding motility. In this review, we will discuss new findings and integrate these into our current understanding to propose a model of how environmental sensing is achieved to regulate gliding motility in Toxoplasma. Collectively, these findings also have implications for the understanding of gliding motility across Apicomplexa more broadly.
Topics: Animals; Cell Movement; Ecosystem; Humans; Protozoan Proteins; Toxoplasma; Toxoplasmosis
PubMed: 33278047
DOI: 10.1111/mmi.14661