Friday, November 27, 2009

Toxoplasmosis and Other Intestinal Coccidial Infections in Cats and Dogs

Vet Clin North Am Small Anim Pract. 2009 Nov;39(6):1009-1034.

Toxoplasmosis and Other Intestinal Coccidial Infections in Cats and Dogs

Dubey JP, Lindsay DS, Lappin MR.

United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Beltsville Agricultural Research Center, Building 1001, Beltsville, MD, 20705-2350, USA.

Toxoplasma gondii and related coccidians are intracellular protozoan parasites. Coccidia are obligate intracellular parasites normally found in the intestinal tract. Virtually all warm blooded animals, including humans are commonly infected with coccidians. This article reviews the diagnosis, treatment, and prevention of infections in cats and dogs related to Isospora spp, Toxoplasma gondii, and Neospora caninum. Much remains to be learned concerning the pathogenesis of clinical coccidiosis.

PMID: 19932360 [PubMed - as supplied by publisher]

Characterizaion of a leucine aminopeptidase from Toxoplasma gondii

Mol Biochem Parasitol. 2009 Nov 17. [Epub ahead of print]

Characterizaion of a leucine aminopeptidase from Toxoplasma gondii

Jia H, Nishikawa Y, Luo Y, Yamagishi J, Sugimoto C, Xuan X.

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan; Department of Collaboration and Education, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Hokkaido 001-0020, Japan.

The M17 family leucine aminopeptidase (LAP) hydrolyzes amino acids from the N-terminus of peptides. Many LAPs from parasitic protozoa, including Plasmodium, Trypanosoma, and Leishmania, have been intensely investigated because of their crucial roles in parasite biology. In this study, the functional recombinant Toxoplasma gondii LAP (rTgLAP) was expressed in Escherichia coli (E. coli), and its enzymatic activity against synthetic substrates for aminopeptidase, as well as cellular localization, were determined. The activity was strongly dependent on metal divalent cations, and was inhibited by bestatin, which is an inhibitor for metalloprotease. Our results indicated that TgLAP is a functional aminopeptidase in the cytoplasm of T. gondii.

PMID: 19931316 [PubMed - as supplied by publisher]

Friday, November 20, 2009

Mollaret Meningitis may be Caused by Reactivation of Latent Cerebral Toxoplasmosis

Int J Neurosci. 2009;119(10):1655-1692.

Mollaret Meningitis may be Caused by Reactivation of Latent Cerebral Toxoplasmosis

Prandota J.

Department of Social Pediatrics, Faculty of Public Health, University Medical School, 5 Bartla Street, 51-618, Wroclaw, Poland.

Mollaret meningitis (MM) occurs mainly in females and is characterized by recurrent episodes of headache, transient neurological abnormalities, and the cerebrospinal fluid containing mononuclear cells. HSV-2 was usually identified as the causative agent. Recently, we found that recurrent headaches in non-HIV-infected subjects were due to acquired cerebral toxoplasmosis (CT). The aim of the study was therefore to focus on molecular pathomechanisms that may lead to reactivation of latent CT and manifest as MM. Literature data cited in this work were selected to illustrate that various factors may affect latent CNS Toxoplasma gondii infection/inflammation intensity and/or host defense mechanisms, i.e., the production of NO, cytokines, tryptophan degradation by indoleamine 2,3-dioxygenase, mechanisms mediated by an IFN-gamma responsive gene family, limiting the availability of intracellular iron to T. gondii, and production of reactive oxygen/nitrogen species, finally inducing choroid plexitis and/or vasculitis. Examples of triggers revealing MM and accompanying disturbances of IFN-gamma-mediated immune responses that control HSV-2 and T. gondii include: female predominance (female mice are more susceptible to T. gondii infection than males); HSV-2 infection (increased IFN-gamma, IL-12); metaraminol (increased plasma catecholamine levels, changes in cytokine expression favoring T(H)2 cells responses); probably cholesterol contained in debris from ruptured epidermoid cysts (decreased NO; increased TNF-alpha, IL-6, IL-8). These irregularities induced by the triggers may be responsible for reactivation of latent CT and development of MM. Thus, subjects with MM should have test(s) for T. gondii infection performed obligatorily.

PMID: 19922380 [PubMed - as supplied by publisher]

Diagnosis of congenital toxoplasmosis using whole-blood interferon-{gamma} release assay

J Clin Microbiol. 2009 Nov 18. [Epub ahead of print]

Diagnosis of congenital toxoplasmosis using whole-blood interferon-{gamma} release assay

Chapey E, Wallon M, Debize G, Rabilloud M, Peyron F.

Hospices Civils de Lyon, Service de Parasitologie, Hôpital de la Croix Rousse, F-69317 Lyon, France; Université Claude Bernard Lyon 1, Service de Parasitologie, Faculté de Médecine Lyon Sud, F-69372 Lyon, France; Hospices Civils de Lyon, Laboratoire d'Hématologie, Hôpital de la Croix Rousse, F-69317 Lyon, France; Hospices Civils de Lyon, Service de Biostatistique, F-69424 Lyon, France; Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France; CNRS, UMR 5558, Laboratoire Biostatistique Santé, F-69495 Pierre-Bénite, France.

Congenital toxoplasmosis at birth is generally subclinical but infected infants are at risk of developing ocular lesions. Diagnosis at birth relies mainly on serological tests. Cell- mediated immunity plays the major role in resistance to infection but is not routinely investigated for diagnostic purposes. Here we describe a simple test based on the response to interferon-gamma (IFN-gamma) after stimulation of whole blood by crude parasitic antigens. One millilitre of heparinized blood was centrifuged; plasma was kept for routine serological tests and pellets were resuspended in culture medium. After 24 h of culture in the presence of crude Toxoplasma gondii antigen, the cells were centrifuged and IFN-gamma was assayed in the supernatant. In 62 infants under 1 year of age born to mothers who were infected during pregnancy, the sensitivity and specificity were 94% (16/17) and 98% (44/45), respectively. The false negative was in a treated baby who turned positive after withdrawal of treatment. The false positive was observed in 3-month-old baby. In a cohort of 124 congenitally infected patients aged between 1 and 30 years, the sensitivity of the test was 100%. We present a simple test based on IFN-gamma secretion to assess cell-mediated immunity in toxoplasmosis. As only 1 mL of blood is required to investigate humoral and cellular immunity, our assay is well adapted for the study of congenital toxoplasmosis in infants. Using purified antigens or recombinant peptides might improve the test performances.

PMID: 19923492 [PubMed - as supplied by publisher]

Wednesday, November 18, 2009

Asymptomatic diffuse "encephalitic" cerebral toxoplasmosis in a patient with chronic lymphocytic leukemia: case report and review of the literature

Int J Clin Exp Pathol. 2009 Mar 15;3(1):106-9.

Asymptomatic diffuse "encephalitic" cerebral toxoplasmosis in a patient with chronic lymphocytic leukemia: case report and review of the literature

Abedalthagafi M, Rushing EJ, Garvin D, Cheson B, Ozdemirli M.

Opportunistic infections account for the majority of central nervous system lesions in adult immunosuppressed patients. In this setting, toxoplasmosis typically manifests as multiple abscesses readily seen on routine neuroimaging studies. Asymptomatic, widely disseminated Toxoplasma cysts without parenchymal reaction are also recognized. In contrast, widespread parasites in the brain parenchyma with an inflammatory "encephalitic" reaction and little or no necrosis have been reported in only four patients with acquired immune deficiency syndrome (AIDS). We describe a 70 year old male with stage IV chronic lymphocytic leukemia complicated by aplastic anemia. Neurological examination and imaging revealed no significant abnormalities. At autopsy, the brain revealed multifocal cysts and free tachyzoites of Toxoplasma gondii with diffuse microglial nodules and no necrosis. To the best of our knowledge, this case represents the first report of the "encephalitic" form of toxoplasmosis in a non-AIDS patient.

PMID: 19918334 [PubMed - in process]

Patient with toxoplasmosis and glucose-6-phosphate dehydrogenase deficiency: a case report

Cases J. 2009 Aug 6;2:8826.

Patient with toxoplasmosis and glucose-6-phosphate dehydrogenase deficiency: a case report

Nunes AA.

Department of Social Medicine, University of Sao Paulo, Avenida Bandeirantes 3900 - Monte Alegre, 14.048-900 - Ribeirao Preto SP Brazil.

INTRODUCTION: Toxoplasmosis, a zoonotic protozoal disease caused by toxoplasma gondii, is prevalent throughout the world, affecting a large proportion of persons who usually have no symptoms. Glucose 6 phosphate dehydrogenase deficiency, an X-linked inherited disorder, is present in over 400 million people world wide. It is more common in tropical and subtropical countries and is one of the important causes of hemolytic anemia. CASE PRESENTATION: This case report relates the occurrence of the two diseases simultaneously in a child of five years old. CONCLUSION: Patients with glucose-6-phosphate dehydrogenase deficiency are more susceptible to toxoplasmosis and this case report, reinforce the findings of this propensity and alert us for such possibility, what it is important, therefore, the treatment of toxoplasmosis can cause serious hemolysis in these patients.

PMID: 19918404 [PubMed - in process]

Congenital toxoplasmosis from a chronically infected woman with reactivation of retinochoroiditis during pregnancy - an underestimated event?

J Pediatr (Rio J). 2009 Nov 16;86(1). [Epub ahead of print]

Congenital toxoplasmosis from a chronically infected woman with reactivation of retinochoroiditis during pregnancy - an underestimated event?

Andrade GM, Vasconcelos-Santos DV, Carellos EV, Romanelli RM, Vitor RW, Carneiro AC, Januario JN.

Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.

OBJECTIVE: To report a rare case of congenital toxoplasmosis from an immunocompetent mother with chronic infection who had reactivation of ocular disease during pregnancy. DESCRIPTION: The newborn was asymptomatic at birth and identified by neonatal screening (IgM anti-Toxoplasma gondii in dried blood) among other 190 infants with congenital toxoplasmosis during a 7-month period. His mother had had a non-treated episode of reactivation of toxoplasmic retinochoroiditis during pregnancy, with stable IgG titers and negative IgM results. Results of IgM and IgG in the newborn's serum, as well as IgG immunoblotting were positive and active retinochoroidal lesions were detected in his peripheral retina. The neonate was treated with sulfadiazine, pyrimethamine and folinic acid. At 14 months of life, the child remained asymptomatic, with regression of retinochoroidal lesions and persistence of IgG. COMMENTS: It is possible that systematic neonatal screening in areas with high prevalence of infection may identify these cases.

PMID: 19918624 [PubMed - as supplied by publisher]

Early Response of Mucosal Epithelial Cells during Toxoplasma gondii Infection

J Immunol. 2009 Nov 16. [Epub ahead of print]

Early Response of Mucosal Epithelial Cells during Toxoplasma gondii Infection

Ju CH, Chockalingam A, Leifer CA.

Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

The innate immune response of mucosal epithelial cells during pathogen invasion plays a central role in immune regulation in the gut. Toxoplasma gondii is a protozoan intracellular parasite that is usually transmitted through oral infection. Although much of the information on immunity to T. gondii has come from i.p. infection models, more recent studies have revealed the importance of studying immunity following infection through the natural peroral route. Oral infection studies have identified many of the key players in the intestinal response; however, they have relied on responses detected days to weeks following infection. Much less is known about how the gut epithelial layer senses and reacts during initial contact with the pathogen. Given the importance of epithelial cells during pathogen invasion, this study uses an in vitro approach to isolate the key players and examine the early response of intestinal epithelial cells during infection by T. gondii. We show that human intestinal epithelial cells infected with T. gondii elicit rapid MAPK phosphorylation, NF-kappaB nuclear translocation, and secretion of IL-8. Both ERK1/2 activation and IL-8 secretion responses were shown to be MyD88 dependent and TLR2 was identified to be involved in the recognition of the parasite regardless of the parasite genotype. Furthermore, we were able to identify additional T. gondii-regulated genes in the infected cells using a pathway-focused array. Together, our findings suggest that intestinal epithelial cells were able to recognize T. gondii during infection, and the outcome is important for modulating intestinal immune responses.

PMID: 19917706 [PubMed - as supplied by publisher]

The importance of toxoplasma gondii infection in diseases presenting with headaches

Int J Neurosci. 2009;119(12):2144-82.

The importance of toxoplasma gondii infection in diseases presenting with headaches. Headaches and aseptic meningitis may be manifestations of the Jarisch-Herxheimer reaction

Prandota J.

Department of Social Pediatrics, Faculty of Public Health, University Medical School, Wroclaw, Poland. Prandota@ak.am.wroc.pl

Worldwide, approximately 2 billion people are chronically infected with T. gondii with largely unknown consequences. This review presents clinical symptoms, differential diagnosis, triggering factors, treatment, and pathomechanisms responsible for idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis. Literature cited in this work illustrates that immune state and other biologic mediator imbalances due to various endogenous and exogenous triggering factors may markedly affect latent central nervous system T. gondii infection/inflammation intensity, and cause reactivation of cerebral toxoplasmosis (CT). Irregularities in pro- and anti-inflammatory processes may markedly disturb the host and/or T. gondii defense mechanisms important for immune control of the parasite thereby manifesting as a wide range of neurologic symptoms and signs observed in some patients with migraine, epilepsy, celiac disease, Henoch-Schönlein purpura, and other brain disorders. This is consistent with reactivation of CT in mice after treatment with dexamethasone associated with depression of type T(H)1 immune response, and development of CT after administration of etanercept or other bioproducts. It seems that various types of headaches, epilepsy, aseptic meningitis, systemic adverse reactions to drugs or other substances represent the Jarisch-Herxheimer reaction due to apoptosis of T. gondii tachyzoites. Also development of some brain tumors, such as ependymoma and glioma may be associated with a chronic course of CT. Thus, all these patients should be tested for T. gondii infection.

PMID: 19916846 [PubMed - in process]

EuPathDB: a portal to eukaryotic pathogen databases

Nucleic Acids Res. 2009 Nov 13. [Epub ahead of print]

EuPathDB: a portal to eukaryotic pathogen databases

Aurrecoechea C, Brestelli J, Brunk BP, Fischer S, Gajria B, Gao X, Gingle A, Grant G, Harb OS, Heiges M, Innamorato F, Iodice J, Kissinger JC, Kraemer ET, Li W, Miller JA, Nayak V, Pennington C, Pinney DF, Roos DS, Ross C, Srinivasamoorthy G, Stoeckert CJ Jr, Thibodeau R, Treatman C, Wang H.

Center for Tropical & Emerging Global Diseases, University of Georgia, Athens, GA 30602, Penn Center for Bioinformatics, University of Pennsylvania, Philadelphia, PA 19104, Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, Center for Applied Genetic Technologies, University of Georgia, Athens, GA 30602, Department of Genetics, University of Georgia, Athens, GA 30602 and Department of Computer Science, University of Georgia, Athens, GA 30602, USA.

EuPathDB (http://EuPathDB.org; formerly ApiDB) is an integrated database covering the eukaryotic pathogens of the genera Cryptosporidium, Giardia, Leishmania, Neospora, Plasmodium, Toxoplasma, Trichomonas and Trypanosoma. While each of these groups is supported by a taxon-specific database built upon the same infrastructure, the EuPathDB portal offers an entry point to all these resources, and the opportunity to leverage orthology for searches across genera. The most recent release of EuPathDB includes updates and changes affecting data content, infrastructure and the user interface, improving data access and enhancing the user experience. EuPathDB currently supports more than 80 searches and the recently-implemented 'search strategy' system enables users to construct complex multi-step searches via a graphical interface. Search results are dynamically displayed as the strategy is constructed or modified, and can be downloaded, saved, revised, or shared with other database users.

PMID: 19914931 [PubMed - as supplied by publisher]

Up-regulation of hyaluronan receptors in Toxoplasma gondii-infected monocytic cells

Biochem Biophys Res Commun. 2009 Nov 12. [Epub ahead of print]

Up-regulation of hyaluronan receptors in Toxoplasma gondii-infected monocytic cells

Unno A, Kitoh K, Takashima Y.

Department of Veterinary Parasitological Diseases, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan; United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.

The apicomplexan, obligate intracellular parasite Toxoplasma gondii orally infects humans and animals. The parasites cross the intestinal epithelium, invade leukocytes in the general circulation and then disseminate into the peripheral organs. The mechanism of extravasation of the infected leukocytes, however, remains poorly understood. It is known that adhesion of leukocytes to extracellular matrix (ECM) is an important factor in extravasation, and CD44 and ICAM-1 on the leukocyte surface are known receptors for hyaluronan (HA), an ECM component. In this study, we demonstrated up-regulation of CD44 and ICAM-1 expression on the surface of T. gondii-infected human monocytic THP-1 cells and fresh isolated human monocyte. T. gondii-infected THP-1 cells adhered more efficiently to immobilized HA than did non-infected cells. T. gondii-infected monocytes in the general circulation might preferentially adhere to the ECM and migrate out from blood vessels, so transporting parasites into the peripheral organs.

PMID: 19914206 [PubMed - as supplied by publisher]

Toll-like receptor initiated host defense against Toxoplasma gondii

J Biomed Biotechnol. 2010;2010:737125. Epub 2009 Nov 11.

Toll-like receptor initiated host defense against Toxoplasma gondii

Denkers EY.

Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. eyd1@cornell.edu

Toxoplasma gondii is an intracellular pathogen notable for its ability to establish a stable host-parasite relationship amongst a wide range of host species and in a large percentage of the human population. Toll-like receptor signaling through MyD88 is a critical pathway in initiating defense against this opportunistic protozoan and may also be a mediator of pathology during immune dysfunction. Other MyD88 independent signaling pathways are also involved in the host-parasite interaction. These responses can be triggered by the parasite itself, but interactions with the intestinal microbiota add additional complexity during enteric infection.

PMID: 19911079 [PubMed - in process]

Wednesday, November 11, 2009

A single polymorphic amino acid on Toxoplasma gondii kinase ROP16 determines the direct and strain-specific activation of Stat3

J Exp Med. 2009 Nov 9. [Epub ahead of print]

A single polymorphic amino acid on Toxoplasma gondii kinase ROP16 determines the direct and strain-specific activation of Stat3

Yamamoto M, Standley DM, Takashima S, Saiga H, Okuyama M, Kayama H, Kubo E, Ito H, Takaura M, Matsuda T, Soldati-Favre D, Takeda K.

Department of Microbiology and Immunology and 2 Department of Cardiovascular Medicine, Graduate School of Medicine, and 3 Laboratory of Mucosal Immunology and 4 Laboratory of Systems Immunology, World Premier International Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan.

Infection by Toxoplasma gondii down-regulates the host innate immune responses, such as proinflammatory cytokine production, in a Stat3-dependent manner. A forward genetic approach recently demonstrated that the type II strain fails to suppress immune responses because of a potential defect in a highly polymorphic parasite-derived kinase, ROP16. We generated ROP16-deficient type I parasites by reverse genetics and found a severe defect in parasite-induced Stat3 activation, culminating in enhanced production of interleukin (IL) 6 and IL-12 p40 in the infected macrophages. Furthermore, overexpression of ROP16 but not ROP18 in mammalian cells resulted in Stat3 phosphorylation and strong activation of Stat3-dependent promoters. In addition, kinase-inactive ROP16 failed to activate Stat3. Comparison of type I and type II ROP16 revealed that a single amino acid substitution in the kinase domain determined the strain difference in terms of Stat3 activation. Moreover, ROP16 bound Stat3 and directly induced phosphorylation of this transcription factor. These results formally establish an essential and direct requirement of ROP16 in parasite-induced Stat3 activation and the significance of a single amino acid replacement in the function of type II ROP16.

PMID: 19901082 [PubMed - as supplied by publisher]

Members of a novel protein family containing MAR domains act as sialic acid-binding lectins during host cell invasion by apicomplexan parasites

J Biol Chem. 2009 Nov 9. [Epub ahead of print]

Members of a novel protein family containing MAR domains act as sialic acid-binding lectins during host cell invasion by apicomplexan parasites

Friedrich N, Santos JM, Liu Y, Palma AS, Leon E, Saouros S, Kiso M, Blackman MJ, Matthews S, Feizi T, Soldati-Favre D.

University of Geneva, Faculty of Medicine, Switzerland;

Numerous intracellular pathogens exploit cell surface glycoconjugates for host cell recognition and entry. Unlike bacteria and viruses, Toxoplasma gondii and other parasites of the phylum Apicomplexa actively invade host cells and this process critically depends on adhesins (MICs) released onto the parasite surface from intracellular organelles called micronemes. The microneme adhesive repeat (MAR) domain of T. gondii MIC1 (TgMIC1) recognizes sialic acid (Sia), a key determinant on the host-cell surface for invasion by this pathogen. By complementation and invasion assays, we demonstrate that TgMIC1 is one important player in Sia-dependent invasion, and that another novel Sia-binding lectin, designated TgMIC13, is also involved. Using BLAST searches, we identify a family of MAR-containing proteins in enteroparasitic coccidians, a subclass of apicomplexans including T. gondii, suggesting that all these parasites exploit sialylated glycoconjugates on host-cells as determinants for enteric invasion. Furthermore this protein family might provide a basis for the broad host-cell range observed for coccidians that form tissue cysts during chronic infection. Carbohydrate microarray analyses, corroborated by structural considerations, show that TgMIC13, TgMIC1 and its homologue Neospora caninum MIC1 (NcMIC1) share a preference for alpha2-3- over alpha2-6-linked sialyl-N-acetyllactosamine sequences. However, the three lectins also display differences in binding preferences. Intense binding of TgMIC13 to alpha2-9-linked disialyl-sequence reported on embryonal cells and relatively strong binding to 4-O-acetylated-Sia found on gut epithelium, and binding of NcMIC1 to 6'sulpho-sialyl Lewis(x) might have implications for tissue tropism.

PMID: 19901027 [PubMed - as supplied by publisher]

Tuesday, November 10, 2009

Decrease of Foxp3(+) Treg Cell Number and Acquisition of Effector Cell Phenotype during Lethal Infection

Immunity. 2009 Nov 4. [Epub ahead of print]

Decrease of Foxp3(+) Treg Cell Number and Acquisition of Effector Cell Phenotype during Lethal Infection

Oldenhove G, Bouladoux N, Wohlfert EA, Hall JA, Chou D, Dos Santos L, O'Brien S, Blank R, Lamb E, Natarajan S, Kastenmayer R, Hunter C, Grigg ME, Belkaid Y.

Mucosal Immunology Unit, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.

Using a model of lethal oral infection with Toxoplasma gondii, we examined the fate of both induced and natural regulatory T (Treg) cells in the face of strong inflammatory responses occurring in a tolerogenic-prone environment. We found that during highly T helper 1 (Th1) cell-polarized mucosal immune responses, Treg cell numbers collapsed via multiple pathways, including blockade of Treg cell induction and disruption of endogenous Treg cell homeostasis. In particular, shutdown of interleukin 2 (IL-2) in the highly Th1 cell-polarized environment triggered by infection directly contributes to Treg cell incapacity to suppress effector responses and eventually leads to immunopathogenesis. Furthermore, we found that environmental cues provided by both local dendritic cells and effector T cells can induce the expression of T-bet transcription factor and IFN-gamma by Treg cells. These data reveal a mechanism for Th1 cell pathogenicity that extends beyond their proinflammatory program to limit Treg cell survival.

PMID: 19896394 [PubMed - as supplied by publisher]

Monday, November 09, 2009

Dysregulation of macrophage signal transduction by Toxoplasma gondii: past progress and recent advances

Parasite Immunol. 2009 Dec;31(12):717-28.

Dysregulation of macrophage signal transduction by Toxoplasma gondii: past progress and recent advances

Leng J, Butcher BA, Denkers EY.

Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401, USA.

The opportunistic protozoan parasite Toxoplasma gondii is well known as a strong inducer of cell-mediated immunity, largely as a result of proinflammatory cytokine induction during in vivo infection. Yet, during intracellular infection the parasite suppresses signal transduction pathways leading to these proinflammatory responses. The opposing responses are likely to reflect the parasite's need to stimulate immunity allowing host survival and parasite persistence, and at the same time avoiding excessive responses that could result in parasite elimination and host immunopathology. This Review summarizes past and present investigations into the effects of Toxoplasma on host cell signal transduction. These studies reveal insight into the profound suppression of proinflammatory cytokine responses that occurs when the parasite infects macrophages and other cells of innate immunity.

PMID: 19891610 [PubMed - in process]

Anti-parasitic action and elimination of intracellular Toxoplasma gondii in the presence of novel thiosemicarbazone

Braz J Med Biol Res. 2009 Nov 6. pii: S0100-879X2009005000038. [Epub ahead of print]

Anti-parasitic action and elimination of intracellular Toxoplasma gondii in the presence of novel thiosemicarbazone and its 4-thiazolidinone derivatives

Carvalho CS, de Melo EJ.

Setor de Toxicologia Celular, Laboratório de Biologia Celular e Tecidual, Universidade Estadual do Norte Fluminense, Rio de Janeiro, RJ, Brasil.

Toxoplasma, which infects all eukaryotic cells, is considered to be a good system for the study of drug action and of the behavior of infected host cells. In the present study, we asked if thiosemicarbazone derivatives can be effective against tachyzoites and which morphological and ultrastructural features of host cells and parasites are associated with the destruction of Toxoplasma. The compounds were tested in infected Vero cell culture using concentration screens (0.1 to 20 mM). The final concentration of 1 mM was chosen for biological assay. The following results were obtained: 1) These new derivatives decreased T. gondii infection with an in vitro parasite IC50% of 0.2-0.7 mM, without a significant effect on host cells and the more efficient compounds were 2, 3 (thiosemicarbazone derivatives) and 4 (thiazolidinone derivative); 2) The main feature observed during parasite elimination was continuous morphological disorganization of the tachyzoite secretory system, progressive organelle vesiculation, and then complete disruption; 3) Ultrastructural assays also revealed that progressive vesiculation in the cytoplasm of treated parasites did not occur in the host cell; 4) Vesiculation inside the parasite resulted in death, but this feature occurred asynchronously in different intracellular tachyzoites; 5) The death and elimination of T. gondii was associated with features such as apoptosis-like stage, acidification and digestion of parasites into parasitophorous vacuoles. Our results suggest that these new chemical compounds are promising for the elimination of intracellular parasites by mainly affecting tachyzoite development at 1 mM concentration for 24 h of treatment.

PMID: 19893994 [PubMed - as supplied by publisher]

Friday, November 06, 2009

Post-translational modifications to Toxoplasma gondii alpha- and beta-tubulins include novel C-terminal methylation

J Proteome Res. 2009 Nov 4. [Epub ahead of print]

Post-translational modifications to Toxoplasma gondii alpha- and beta-tubulins include novel C-terminal methylation

Xiao H, El Bissati K, Verdier-Pinard P, Burd B, Zhang H, Kim K, Fiser A, Angeletti RH, Weiss LM.

Toxoplasma gondii is an apicomplexan of both medical and veterinary importance which is classified as an NIH Category B priority pathogen. It is best known for its ability to cause congenital infection in immune competent hosts and encephalitis in immune compromised hosts. The highly stable and specialized microtubule-based cytoskeleton participates in the invasion process. The genome encodes three isoforms of both alpha- and beta-tubulin and we show that the tubulin is extensively altered by specific post-translational modifications (PTMs) in this paper. T. gondii tubulin PTMs were analyzed by mass spectrometry and immunolabeling using specific antibodies. The PTMs identified on alpha-tubulin included acetylation of Lys40, removal of the last C-terminal amino acid residue Tyr453 (detyrosinated tubulin) and truncation of the last five amino acid residues. Polyglutamylation was detected on both alpha- and beta-tubulins. An antibody directed against mammalian alpha-tubulin lacking the last two C-terminal residues (Delta2-tubulin) labeled the apical region of this parasite. Detyrosinated tubulin was diffusely present in subpellicular microtubules and displayed an apparent accumulation at the basal end. Methylation, a PTM not previously described on tubulin, was also detected. Methylated tubulins were not detected in the host cells, human foreskin fibroblasts, suggesting that this may be a modification specific to the Apicomplexa.

PMID: 19886702 [PubMed - as supplied by publisher]

Obtaining Highly Purified Toxoplasma gondii Oocysts by a Discontinuous Cesium Chloride Gradient

J Vis Exp. 2009 Nov 3;(33). pii: 1420. doi: 10.3791/1420.

Obtaining Highly Purified Toxoplasma gondii Oocysts by a Discontinuous Cesium Chloride Gradient

Staggs SE, See MJ, Dubey JP, Villegas EN.

Dynamac, Inc.

Toxoplasma gondii is an obligate intracellular protozoan pathogen that commonly infects humans. It is a well characterized apicomplexan associated with causing food- and water-borne disease outbreaks. The definitive host is the feline species where sexual replication occurs resulting in the development of the highly infectious and environmentally resistant oocyst. Infection occurs via ingestion of tissue cysts from contaminated meat or oocysts from soil or water. Infection is typically asymptomatic in healthy individuals, but results in a life-long latent infection that can reactivate causing toxoplasmic encephalitis and death if the individual becomes immunocompromised. Meat contaminated with T. gondii cysts have been the primary source of infection in Europe and the United States, but recent changes in animal management and husbandry practices and improved food handling and processing procedures have significantly reduced the prevalence of T. gondii cysts in meat(1, 2). Nonetheless, seroprevalence in humans remains relatively high suggesting that exposure from oocyst contaminated soil or water is likely. Indeed, waterborne outbreaks of toxoplasmosis have been reported worldwide supporting the theory exposure to the environmental oocyst form poses a significant health risk(3-5). To date, research on understanding the prevalence of T. gondii oocysts in the water and environment are limited due to the lack of tools to detect oocysts in the environment (5, 6). This is primarily due to the lack of efficient purification protocols for obtaining large numbers of highly purified T gondii oocysts from infected cats for research purposes. This study describes the development of a modified CsCl method that easily purifies T. gondii oocysts from feces of infected cats that are suitable for molecular biological and tissue culture manipulation(7).

PMID: 19888193 [PubMed - in process]

Critical role for the immunoproteasome subunit LMP7 in the resistance of mice to Toxoplasma

Eur J Immunol. 2009 Nov 4. [Epub ahead of print]

Critical role for the immunoproteasome subunit LMP7 in the resistance of mice to Toxoplasma gondii infection


Tu L, Moriya C, Imai T, Ishida H, Tetsutani K, Duan X, Murata S, Tanaka K, Shimokawa C, Hisaeda H, Himeno K.

Department of Parasitology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.

Proteasome-mediated proteolysis is responsible for the generation of immunogenic epitopes presented by MHC class I molecules, which activate antigen-specific CD8(+) T cells. Immunoproteasomes, defined by the presence of the three catalytic subunits LMP2, MECL-1, and LMP7, have been hypothesized to optimize MHC class I antigen processing. In this study, we demonstrate that the infection of mice with a protozoan parasite, Toxoplasma gondii, induced the expression of LMP7 mRNA in APC and increased the capacity of APC to induce the production of IFN-gamma by antigen-specific CD8(+) T cells. In vitro infection of a DC cell line with T. gondii also induced the expression of LMP7 and resulted in enhanced proteasome proteolytic activity. Finally, mice lacking LMP7 were highly susceptible to infection with T. gondii and showed a reduced number of functional CD8(+) T cells. These results demonstrate that proteasomes containing LMP7 play an indispensable role in the survival of mice infected with T. gondii, presumably due to the efficient generation of CTL epitopes required for the functional development of CD8(+) T cells.

PMID: 19890948 [PubMed - as supplied by publisher]

Association between intracellular infectious agents and Tourette's syndrome

Eur Arch Psychiatry Clin Neurosci. 2009 Nov 5. [Epub ahead of print]

Association between intracellular infectious agents and Tourette's syndrome

Krause D, Matz J, Weidinger E, Wagner J, Wildenauer A, Obermeier M, Riedel M, Müller N.

Department of Psychiatry, Ludwig-Maximilians University Munich, Nussbaumstr. 7, 80336, Munich, Germany, Daniela.Krause@med.uni-muenchen.de.

The underlying pathophysiological mechanisms in Tourette's syndrome (TS) are still unclear. Increasing evidence supports the involvement of infections, possibly on the basis of an altered immune status. Not only streptococci but also other infectious agents may be involved. This study investigates the association between the neurotrophic agents Chlamydia, Toxoplasma and TS. 32 patients with TS and 30 healthy matched controls were included. For each individual, IgA/IgG antibody titers against Chlamydia trachomatis/pneumoniae and Toxoplasma gondii were evaluated and analyzed with Fisher's exact test. We found a significantly higher rate of TS patients with elevated antibody titers against Chlamydia trachomatis (P = 0.017) as compared to controls. A trend toward a higher prevalence in the Tourette's group was shown for Toxoplasma (P = 0.069). In conclusion, within the TS patients a higher rate of antibody titers could be demonstrated, pointing to a possible role of Chlamydia and Toxoplasma in the pathogenesis of tic disorders. Because none of these agents has been linked with TS to date, a hypothesis is that infections could contribute to TS by triggering an immune response. It still remains unclear whether tic symptoms are partly due to the infection or to changes in the immune balance caused by an infection.

PMID: 19890596 [PubMed - as supplied by publisher]

Wednesday, November 04, 2009

Isolation of Toxoplasma gondii development mutants identifies a potential proteophosphogylcan that enhances cyst wall formation

Mol Biochem Parasitol. 2009 Oct 29. [Epub ahead of print]

Isolation of Toxoplasma gondii development mutants identifies a potential proteophosphogylcan that enhances cyst wall formation

Craver MP, Rooney PJ, Knoll LJ.

Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706.

Within warm-blooded animals, Toxoplasma gondii switches from an actively replicating form called a tachyzoite into a slow growing encysted form called a bradyzoite. To uncover the genes involved in bradyzoite development, we screened over 8000 T. gondii insertional mutants by immunofluorescence microscopy. We identified nine bradyzoite development mutants that were defective in both cyst wall formation and expression of a bradyzoite specific heat shock protein. One of these mutants, named 42F5, contained an insertion into the predicted gene TGME49_097520. The disrupted protein is serine/proline-rich with homology to proteophosphoglycans from Leishmania. T. gondii proteophosphoglycan (TgPPG1) expressed from the native promoter was undetectable in tachyzoites, but bradyzoites show punctate spots within the parasite and staining around the parasitophorous vacuole. Complementation of the 42F5 mutant with TgPPG1 expressed from either the alpha-tubulin or native promoter restores cyst wall formation. Overall, TgPPG1 is upregulated in bradyzoites and enhances cyst wall component expression and assembly.

PMID: 19879901 [PubMed - as supplied by publisher]

T cell-intrinsic role of Nod2 in promoting type 1 immunity to Toxoplasma

Nat Immunol. 2009 Nov 1. [Epub ahead of print]

T cell-intrinsic role of Nod2 in promoting type 1 immunity to Toxoplasma gondii

Shaw MH, Reimer T, Sánchez-Valdepeñas C, Warner N, Kim YG, Fresno M, Nuñez G.

Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, Michigan, USA.

Nod2 belongs to the nucleotide-binding oligomerization domain receptor (NLR) family of proteins, which function as intracellular pathogen sensors in innate immune cells. Nod2 deficiency results in an impaired immune response to bacterial pathogens. However, how this protein promotes host defense against intracellular parasites is unknown. Here we found that Nod2(-/-) mice had less clearance of Toxoplasma gondii and lower interferon-gamma (IFN-gamma) production. Reconstitution of T cell-deficient mice with Nod2(-/-) T cells followed by T. gondii infection demonstrated a T cell-intrinsic defect. Nod2(-/-) CD4(+) T cells had poor helper T cell differentiation, which was associated with impaired production of interleukin 2 (IL-2) and nuclear accumulation of the transcription factor subunit c-Rel. Our data demonstrate a T cell-intrinsic role for Nod2 signaling that is critical for host defense against T. gondii.

PMID: 19881508 [PubMed - as supplied by publisher]

In-vitro and in-vivo activity of 1-hydroxy-2-alkyl-4(1H)quinolone derivatives against Toxoplasma

Antimicrob Agents Chemother. 2009 Nov 2. [Epub ahead of print]

In-vitro and in-vivo activity of 1-hydroxy-2-alkyl-4(1H)quinolone derivatives against Toxoplasma gondii

Bajohr LL, Ma L, Platte C, Liesenfeld O, Tietze LF, Groß U, Bohne W.

Institut für Mikrobiologie und Hygiene, Charité Universtätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 27, 12203 Berlin, Germany; Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, D-37077 Göttingen, Germany; Institut für Medizinische Mikrobiologie, Universitätsmedizin Göttingen, Kreuzbergring 57, D-37075 Göttingen, Germany.

1-hydroxy-2-dodecyl-4(1)quinolone (HDQ) was recently identified as a Toxoplasma gondii inhibitor. We describe here two novel 1-hydroxyquinolones, which displayed a 10- and 5-fold lower IC50 than HDQ. In a mouse model of acute toxoplasmosis these two compounds and HDQ reduced the percentage of infected peritoneal cells and decreased the parasite load in lung and liver. Compound B showed a tendency towards lower parasite loads in brains in a mouse model of toxoplasmic encephalitis.

PMID: 19884369 [PubMed - as supplied by publisher]

GRA Proteins of Toxoplasma gondii: Maintenance of Host-Parasite Interactions across the Parasitophorous Vacuolar Membrane

Korean J Parasitol. 2009 Oct;47(Supplement):S29-S37.

GRA Proteins of Toxoplasma gondii: Maintenance of Host-Parasite Interactions across the Parasitophorous Vacuolar Membrane

Nam HW.

Department of Parasitology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.

The dense granule of Toxoplasma gondii is a secretory vesicular organelle of which the proteins participate in the modification of the parasitophorous vacuole (PV) and PV membrane for the maintenance of intracellular parasitism in almost all nucleated host cells. In this review, the archives on the research of GRA proteins are reviewed on the foci of finding GRA proteins, characterizing molecular aspects, usefulness in diagnostic antigen, and vaccine trials in addition to some functions in host-parasite interactions.

PMID: 19885333 [PubMed - as supplied by publisher]

Sunday, November 01, 2009

Synthesis and biological evaluation of biguanide and dihydrotriazine derivatives as potential inhibitors of dihydrofolate reductase

J Enzyme Inhib Med Chem. 2009 Oct 29. [Epub ahead of print]

Synthesis and biological evaluation of biguanide and dihydrotriazine derivatives as potential inhibitors of dihydrofolate reductase of opportunistic microorganisms

Bag S, Tawari NR, Queener SF, Degani MS.

Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, Mumbai, India.

Twenty-one biguanide and dihydrotriazine derivatives were synthesized and evaluated as inhibitors of dihydrofolate reductase (DHFR) from opportunistic microorganisms: Pneumocystis carinii (pc), Toxoplasma gondii (tg), Mycobacterium avium (ma), and rat liver (rl). The most potent compound in the series was B2-07 with 12 nM activity against tgDHFR. The most striking observation was that B2-07 showed similar potency to trimetrexate, approximately 233-fold improved potency over trimethoprim and approximately 7-fold increased selectivity as compared to trimetrexate against tgDHFR. Molecular docking studies in the developed homology model of tgDHFR rationalized the observed potency of B2-07. This molecule can act as a good lead for further design of molecules with better selectivity and improved potency.

PMID: 19874136 [PubMed - as supplied by publisher]

Microscopic analysis of calcium ionophore activated egress of Toxoplasma gondii from the host cell

Vet Parasitol. 2009 Oct 4. [Epub ahead of print]

Microscopic analysis of calcium ionophore activated egress of Toxoplasma gondii from the host cell

Caldas LA, de Souza W, Attias M.

Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.

Toxoplasma gondii invades and destroys nucleated cells of warm blooded hosts in a process which involves several steps: recognition, adhesion, penetration, multiplication inside a parasitophorous vacuole (PV) and egress. The last one is the least understood. Parasite egress from LLC-MK2 cells infected with the RH strain of T. gondii was artificially triggered with 4BrA23187 calcium ionophore. The combination of videomicroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) showed that egress does not result from host cell rupture due to overloading with tachyzoites. Videomicroscopy showed that upon calcium ionophore administration parasite rosettes disassemble, the contour of the parasitophorous vacuole disappears and each tachyzoite takes a separate route to the extracellular medium. FESEM and TEM showed the fragmentation of the intravacuolar network, the fragmentation of parasitophorous vacuole membrane and individual tachyzoites with extruded conoids migrating through the cytosol, tightly surrounded by remnants of parasitophorous vacuole membrane or free in the cytosol. Both videomicroscopy and FESEM showed that a single parasite can cross the host cell membrane without disrupting it, while a large number of parasites, egressing simultaneously, rupture the membrane and the cell as a whole. These data suggest that invasion and egress share less similarities than previously believed.

PMID: 19875235 [PubMed - as supplied by publisher]

Primary culture of intestinal epithelial cells as a potential model for Toxoplasma gondii enteric cycle studies

Mem Inst Oswaldo Cruz. 2009 Sep;104(6):862-4.

Primary culture of intestinal epithelial cells as a potential model for Toxoplasma gondii enteric cycle studies

Moura Mde A, Amendoeira MR, Barbosa HS.

Laboratório de Toxoplasmose, Instituto Oswaldo Cruz-Fiocruz, Rio de Janeiro, RJ, Brasil, 21040-361.

The primary culture of intestinal epithelial cells from domestic cats is an efficient cellular model to study the enteric cycle of Toxoplasma gondii in a definitive host. The parasite-host cell ratio can be pointed out as a decisive factor that determines the intracellular fate of bradyzoites forms. The development of the syncytial-like forms of T. gondii was observed using the 1:20 bradyzoite-host cell ratio, resulting in similar forms described in in vivo systems. This alternative study potentially opens up the field for investigation into the molecular aspects of this interaction. This can contribute to the development of new strategies for intervention of a main route by which toxoplasmosis spreads.

PMID: 19876557 [PubMed - in process]