Wednesday, March 31, 2010

Modeling toxoplasmosis spread in cat populations under vaccination

Theor Popul Biol. 2010 Mar 19. [Epub ahead of print]

Modeling toxoplasmosis spread in cat populations under vaccination

Arenas AJ, González-Parra G, Villanueva Micó RJ.

Departamento de Matemáticas y Estadística, Universidad de Córdoba, Montería, Colombia; Instituto de Matemática Multidisciplinar, Universidad Politécnica de Valencia, Edificio 8G, piso 2, P.O. Box 22012, Valencia, Spain.

In this paper we present an epidemiological model to study the transmission dynamics of toxoplasmosis in a cat population under a continuous vaccination schedule. We explore the dynamics of toxoplasmosis at the population level using a mathematical model that includes the effect of oocyst, since the probability of acquisition of Toxoplasma Gondii infection depends on the environmental load of the parasite. This model considers indirectly the infection of prey through the oocyst shedding by cats. We prove that the basic reproduction number R(0) is a threshold value that completely determines the global dynamics and the outcome of the disease. Numerical computer simulations are presented to investigate different scenarios. These simulations show the effectiveness of a constant vaccination program. Copyright © 2010. Published by Elsevier Inc.

PMID: 20304000 [PubMed - as supplied by publisher]

Protective immunity against lethal anaphylactic reaction in Toxoplasma-infected mice by DNA vaccination with T. gondii-derived heat shock protein

Parasitol Int. 2010 Mar 23. [Epub ahead of print]

Protective immunity against lethal anaphylactic reaction in Toxoplasma gondii-infected mice by DNA vaccination with T. gondii-derived heat shock protein 70 gene

Kikumura A, Fang H, Mun HS, Uemura N, Makino M, Sayama Y, Norose K, Aosai F.

Department of Infection and Host Defense, Chiba University Graduate School of Medicine, 1-8-1 Inohana Chuo-ku, Chiba 260-8670, Japan.

Toxoplasma gondii-derived heat shock protein 70 (T.g.HSP70) was proven to induce lethal anaphylactic reaction in T. gondii-infected mice through platelet-activating factor (PAF)-mediated, but not classical IgE-dependent, pathway via TLR4/MyD88 signal pathway. The effector cells generating PAF and causing T.g.HSP70-induced anaphylactic reaction were CD11b(+) and CD11c(+) cells, although the reaction was enhanced by marked IFN-gamma production by CD11b(+), CD11c(+), CD4(+) and CD8(+) splenocytes. In the present study, the effects of T.g.HSP70 gene vaccine targeting peripheral dendritic cells were evaluated against T.g.HSP70-induced anaphylactic reaction in T. gondii-infected mice. C57BL/6 mice receiving T.g.HSP70 gene vaccine showed prolonged survival. Platelets of peripheral blood, which completely disappeared during the T.g.HSP70-induced anaphylactic reaction, were partially restored with the T.g.HSP70 gene vaccination. The T.g.HSP70-induced marked production of PAF and IFN-gamma from splenocytes of infected mice during the T.g.HSP70-induced anaphylactic reaction was shown to decrease after the T.g.HSP70 gene vaccination. Thus, T.g.HSP70 gene vaccine induced protective immunity against T.g.HSP70-induced PAF-mediated lethal anaphylactic reaction in T. gondii-infected mice. Copyright © 2010. Published by Elsevier Ireland Ltd.

PMID: 20346412 [PubMed - as supplied by publisher]

Non-archetypal Type II-like and atypical strains of Toxoplasma gondii infecting marsupials of Australia

Int J Parasitol. 2010 Mar 26. [Epub ahead of print]

Non-archetypal Type II-like and atypical strains of Toxoplasma gondii infecting marsupials of Australia

Parameswaran N, Thompson RC, Sundar N, Pan S, Johnson M, Smith NC, Grigg ME.

WHO Collaborating Centre for the Molecular Epidemiology of Parasitic Infections, School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA 6150, Australia.

Australia is geographically isolated and possesses a remarkable diversity of wildlife species. Marsupials are highly susceptible to infection with the cosmopolitan parasite Toxoplasma gondii. Of 46 marsupials screened for T. gondii by multilocus PCR-DNA sequencing at polymorphic genes (B1, SAG3, GRA6, GRA7), 12 were PCR-positive; the majority (67%; 9/12) were infected by non-archetypal Type II-like or atypical strains. Six novel alleles were detected at B1, indicating greater diversity of genotypes than previously envisaged. Two isolates lethal to marsupials, were avirulent to mice. The data support the conclusion that Australia's isolation may have favoured the persistence of non-archetypal ancestral genotypes. Copyright © 2010. Published by Elsevier Ltd.

PMID: 20346947 [PubMed - as supplied by publisher]

Identification of T. gondii epitopes, adjuvants, and host genetic factors that influence protection of mice and humans

Vaccine. 2010 Mar 25. [Epub ahead of print]

Identification of T. gondii epitopes, adjuvants, and host genetic factors that influence protection of mice and humans

Tan TG, Mui E, Cong H, Witola W, Montpetit A, Muench SP, Sidney J, Alexander J, Sette A, Grigg M, Maewal A, McLeod R.

Department of Surgery, Committees on Immunology, Molecular Medicine, and Genetics, Institute of Genomics and Systems Biology, and The College, The University of Chicago, Chicago, IL 60615, USA; Department of Pediatrics (Infectious Disease), Committees on Immunology, Molecular Medicine, and Genetics, Institute of Genomics and Systems Biology, and The College, The University of Chicago, Chicago, IL 60615, USA.

Toxoplasma gondii is an intracellular parasite that causes severe neurologic and ocular disease in immune-compromised and congenitally infected individuals. There is no vaccine protective against human toxoplasmosis. Herein, immunization of L(d) mice with HF10 (HPGSVNEFDF) with palmitic acid moieties or a monophosphoryl lipid A derivative elicited potent IFN-gamma production from L(d)-restricted CD8(+) T cells in vitro and protected mice. CD8(+) T cell peptide epitopes from T. gondii dense granule proteins GRA 3, 6, 7, and Sag 1, immunogenic in humans for HLA-A02(+), HLA-A03(+), and HLA-B07(+) cells were identified. Since peptide repertoire presented by MHC class I molecules to CD8(+) T cells is shaped by endoplasmic reticulum-associated aminopeptidase (ERAAP), polymorphisms in the human ERAAP gene ERAP1 were studied and associate with susceptibility to human congenital toxoplasmosis (p<0.05). These results have important implications for vaccine development. Copyright © 2010. Published by Elsevier Ltd.

PMID: 20347630 [PubMed - as supplied by publisher]

Acquired infection with Toxoplasma in adult mice results in sensorimotor deficits but normal cognitive behavior despite widespread brain pathology

Microbes Infect. 2010 Mar 25. [Epub ahead of print]

Acquired infection with Toxoplasma gondii in adult mice results in sensorimotor deficits but normal cognitive behavior despite widespread brain pathology

Gulinello M, Acquarone M, Kim JH, Spray DC, Barbosa HS, Sellers R, Tanowitz HB, Weiss LM.

Behavioral Core Facility, Department of Neuroscience,1410 Pelham PkwyS K925 Albert Einstein College of Medicine, Bronx, NY 10461.

Toxoplasma gondii is a ubiquitous intracellular parasite which chronically infects 30 to 50% of the human population. While acquired infection is primarily asymptomatic several studies have suggested that such infections may contribute to neurological and psychiatric symptoms. Previous studies in rodents have demonstated that T. gondii infection does not just kill its host, but alters the behavioral repertoire of an infected animal making it more likely that predation with occur completing the parasite life cycle. The aim of the present study was to evaluate the behavioral changes in C57BL/6 mice chronically infected with the avirulent T. gondii (ME49, a type II strain), in a comprehensive test battery. Infected mice demonstrated profound and widespread brain pathology, motor coordination and sensory deficits. In contrast, cognitive function, anxiety levels, social behavior and the motivation to explore novel objects were normal. The observed changes in behavior did not represent "gross" brain damage or dysfunction and were not due to targeted destruction of specific areas of the brain. Such changes point out the subtle interaction of this parasite with its intermediate hosts and are consistent with ideas about increased predation being an outcome of infection. Copyright © 2010. Published by Elsevier SAS.

PMID: 20348009 [PubMed - as supplied by publisher]

The probable relation between Toxoplasma gondii and Parkinson's disease

Neurosci Lett. 2010 Mar 26. [Epub ahead of print]

The probable relation between Toxoplasma gondii and Parkinson's disease

Miman O, Kusbeci OY, Aktepe OC, Cetinkaya Z.

Afyon Kocatepe University Faculty of Medicine Department of Microbiology.

Parkinson's disease (PD), a chronic progressive neurodegenerative disorder, has a mainly unknown multifactorial etiology. Neuroinflammatory mechanisms might contribute to the cascade of events leading to neuronal degeneration. Toxoplasmosis can be associated with various neuropsychiatric disorders. The most commonly affected central nervous system (CNS) region in toxoplasmosis is the cerebral hemisphere, followed by the basal ganglia, cerebellum and brain stem. Therefore, in this study, we aimed to investigate the possible association between Toxoplasma infection and PD by evaluating the serum anti-T. gondii IgG antibodies. There were no difference between the socioeconomic status of the patients and control subjects and magnetic resonance images of the patients were normal. Serum anti-T. gondii IgG levels were measured using ELISA. There was no statistically significant differences among the patients and control subjects with respect to age (66,01+/-12,14 years, 62,42+/-5,93 years, p=0.089; respectively) and gender. The sero-positivity rate for anti-T. gondii IgG antibodies in PD patients and control groups were 42.3% and 22.5% respectively and they were statistically significant (p=0.006). These results suggest that Toxoplasma infection may be involved in the pathogenetic mechanisms of PD. If confirmed, this hypothesis would represent a valuable advancement in care of patients with Parkinson's disease. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

PMID: 20350582 [PubMed - as supplied by publisher]

Monday, March 29, 2010

Protozoa traversal of the blood-brain barrier to invade the central nervous system

FEMS Microbiol Rev. 2010 Feb 6. [Epub ahead of print]

Protozoa traversal of the blood-brain barrier to invade the central nervous system

Elsheikha HM, Khan NA.

School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, UK.

Abstract Neuropathogenic protozoa have evolved strategies to breach the blood-brain barrier and invade the central nervous system. These include transcellular, paracellular and the Trojan horse routes but the associated molecular mechanisms remain incompletely understood. Here, we summarize the current understanding of protozoa penetration across the blood-brain barrier, focusing on Plasmodium, Babesia, Trypanosoma, Toxoplasma, Acanthamoeba and Balamuthia. Advances in understanding the molecular pathways will offer opportunities for the rational development of novel therapeutic interventions.

PMID: 20337721 [PubMed - as supplied by publisher]

The effect of essential oils from Thymus broussonetii Boiss on transmission of Toxoplasma gondii cysts in mice

Parasitol Res. 2010 Mar 25. [Epub ahead of print]

The effect of essential oils from Thymus broussonetii Boiss on transmission of Toxoplasma gondii cysts in mice

Dahbi A, Bellete B, Flori P, Hssaine A, Elhachimi Y, Raberin H, Chait A, Tran Manh Sung R, Hafid J.

Equipe d'Immuno-Parasitologie et Physiologie, Laboratoire Aliments, Environnement et Santé, Faculté des Sciences et Techniques, Bd. A. El Khattabi, B.P. 549, 40000, Marrakech, Morocco.

In this study, we have evaluated the effect of essential oils of Thymus broussonetii Boiss, an endemic plant of Morocco in experimental transmission of Toxoplasma gondii cysts in mice. These oils were obtained by hydrodistillation and were administered to mice at 20 microg/animal orally at the time of infection and for several days thereafter. This resulted in total absence of intracerebral cysts in mice who received the essential oils signifying that these essential oils of thyme have a blocking effect on the appearance of the cysts. In addition, no abnormality was observed in the control mice who received the essential oils of thyme.

PMID: 20336317 [PubMed - as supplied by publisher]

Thursday, March 25, 2010

Differential Regulation of Effector- and Central-Memory Responses to Toxoplasma gondii Infection by IL-12 Revealed by Tracking of Tgd057-Specific CD8+

PLoS Pathog. 2010 Mar 19;6(3):e1000815.

Differential Regulation of Effector- and Central-Memory Responses to Toxoplasma gondii Infection by IL-12 Revealed by Tracking of Tgd057-Specific CD8+ T Cells

Wilson DC, Grotenbreg GM, Liu K, Zhao Y, Frickel EM, Gubbels MJ, Ploegh HL, Yap GS.

Center for Immunity and Inflammation, UMDNJ-New Jersey Medical School, Newark, New Jersey, United States of America.

Production of the pro-inflammatory cytokine IL-12 by innate phagocytes drives the differentiation of IFN-gamma-producing effector T cells during Toxoplasma gondii infection. However, the role of IL-12 in the regulation of memory CD8+ T cell differentiation and function during murine toxoplasmosis is unclear. To track memory CTL development, we identified a novel H-2K(b)-restricted CTL population specific for the Toxoplasma antigen tgd057. Tgd057-specific CTLs were induced by both vaccination and natural peroral infection, and were representative of the polyclonal CTL population. Tgd057-specific primary effector cells required IL-12 for the differentiation of KLRG1+ effector subpopulations and IFN-gamma production in response to restimulation with parasite-infected cells, but not to restimulation with cognate peptide. The effect of IL-12 deficiency during the primary response was profoundly imprinted on memory CTLs, which continued to show defects in cell numbers, KLRG1+ effector memory subpopulation differentiation, and IFN-gamma recall responses. Importantly, isolated CD62L(hi) KLRG1- CD8+ T cells differentiated in the absence of IL-12 were enhanced in their ability to generate IFN-gamma-producing secondary tgd057-specific effector cells. Our data, for the first time, demonstrate the negative impact of IL-12 signaling on the quality of the central memory CTL compartment. Thus, despite the beneficial role of IL-12 in promoting effector differentiation, excessive exposure to IL-12 during CTL priming may limit the development of long-term protective immunity through the decreased fitness of central memory CTL responses.

PMID: 20333242 [PubMed - in process]

Toxoplasma gondii: Impaired maturation and pro-inflammatory response of dendritic cells in MIF-deficient mice favors susceptibility to infection

Exp Parasitol. 2010 Mar 20. [Epub ahead of print]

Toxoplasma gondii: Impaired maturation and pro-inflammatory response of dendritic cells in MIF-deficient mice favors susceptibility to infection

Terrazas CA, Juarez I, Terrazas LI, Saavedra R, Calleja EA, Rodriguez-Sosa M.

Unidad de Biomedicina.

Macrophage migration inhibitory factor (MIF) has been found to be involved in host resistance to several parasitic infections. To determine the mechanisms of MIF-dependent responses to Toxoplasma gondii, we investigated host resistance in MIF-/- mice (BALB/c background) during natural oral infection. We focused on the potential involvement of MIF in Dendritic Cell (DC) maturation and IL-12 production. Following oral T. gondii infection, wild type mice developed a strong IL-12 response with an adequate maturation of their draining mesenteric lymph node DC (MLNDC) population and were resistant to challenge with either 40 or 100 cysts (ME49 strain). In contrast, similarly infected MIF-/- mice mounted a weak IL-12 response, displayed immature MLNDCs in the early phases of infection and rapidly succumbed to both type of challenges. Lack of maturation and IL-12 production of DCs in response to T. gondii antigens was confirmed by in vitro studies, and these effects were reversed following treatment with recombinant MIF. These findings demonstrate that MIF-induced early DC maturation and IL-12 production mediate resistance to T. gondii infection. Copyright © 2010. Published by Elsevier Inc.

PMID: 20331989 [PubMed - as supplied by publisher]

Accuracy of Real-Time Polymerase Chain Reaction for Toxoplasma gondii in Amniotic Fluid

Obstet Gynecol. 2010 Apr;115(4):727-733.

Accuracy of Real-Time Polymerase Chain Reaction for Toxoplasma gondii in Amniotic Fluid

Wallon M, Franck J, Thulliez P, Huissoud C, Peyron F, Garcia-Meric P, Kieffer F.

From the Service de Parasitologie, Hôpital de la Croix-Rousse, Hospices Civils de Lyon, Lyon, France; the Laboratoire de Parasitologie-Mycologie, Hôpital de la Timone, Marseille, France; the Laboratoire de la Toxoplasmose, Institut de Puériculture de Paris, Paris, France; the Service de Gynécologie Obstétrique, Hôpital de la Croix Rousse, Hospices Civils de Lyon, Lyon, France; the Service de Néonatalogie, Hôpital de la Conception, Marseille, France; the Service de Néonatologie, Institut de Puériculture, Paris, France.

OBJECTIVE:: To provide clinicians with information about the accuracy of real-time polymerase chain reaction (PCR) analysis of amniotic fluid for the prenatal diagnosis of congenital Toxoplasma infection. METHODS:: This was a prospective cohort study of women with Toxoplasma infection identified by prenatal screening in three centers routinely carrying out real-time PCR for the detection of Toxoplasma gondii in amniotic fluid. The data available were gestational age at maternal infection, types and dates of maternal treatment, results of amniocentesis and neonatal work-up and definitive infectious status of the child. We estimated sensitivity, specificity and positive and negative predictive values both overall and per trimester of pregnancy at the time of maternal infection. RESULTS:: Polymerase chain reaction analysis was carried out on amniotic fluid for 261 of the 377 patients included (69%). It was accurate with the exception of four negative results in children who were infected. Overall sensitivity and negative predictive value were 92.2% (95% confidence interval [CI] 81-98%) and 98.1% (95% CI 95-99.5%), respectively. There was no significant association with the trimester of pregnancy during which maternal infection occurred. Specificity and positive predictive values of 100% were obtained for all trimesters. CONCLUSION:: Real-time PCR analysis significantly improves the detection of T. gondii on amniotic fluid. It provides an accurate tool to predict fetal infection and to decide on appropriate treatment and surveillance. However, postnatal follow-up remains necessary in the first year of life to fully exclude infection in children for whom PCR results were negative. LEVEL OF EVIDENCE:: III.

PMID: 20308831 [PubMed - as supplied by publisher]

Separation of DNA-containing organelles from Toxoplasma gondii by CZE

Electrophoresis. 2010 Mar 23. [Epub ahead of print]

Separation of DNA-containing organelles from Toxoplasma gondii by CZE

Moe MK, Samuelsen PJ, Nielsen HV, Nielsen KM.

Department of Pharmacy, University of Tromsø, Tromsø, Norway.

Toxoplasma gondii and other members of the family Apicomplexa have two organelles, in addition to the nucleus, that contain DNA. Herein is reported the separation of the DNA-carrying organelles from T. gondii tachyzoites, i.e. the mitochondrion and the apicoplast, by CZE. The cells were stained with SYTO9, a dye that exhibit fluorescence when interacting with double stranded nucleic acids (e.g. DNA) and disrupted by nitrogen cavitation. Following careful removal of the heavier cellular material, the remaining lysate was injected on a CE instrument and the DNA-containing organelles were detected by LIF. The mitochondrion had longer migration time than the apicoplast, and the migration times were comparable in the replicates. This method should potentially also work for other members of the Apicomplexa including Plasmodium falciparum.

PMID: 20333721 [PubMed - as supplied by publisher]

Tuesday, March 23, 2010

Structural characterization of apical membrane antigen 1 (AMA1) from Toxoplasma gondii

J Biol Chem. 2010 Mar 19. [Epub ahead of print]

Structural characterization of apical membrane antigen 1 (AMA1) from Toxoplasma gondii

Crawford J, Tonkin ML, Grujic O, Boulanger MJ.

University of Victoria, Canada.

Apical membrane antigen 1 (AMA1) is an essential component of the moving junction (MJ) complex used by apicomplexan parasites to invade host cells. We report the 2.0 A resolution X-ray crystal structure of the full ectodomain (domains I, II and III) of AMA1 from the pervasive protozoan parasite Toxoplasma gondii. The structure of T. gondii AMA1 (TgAMA1) is the most complete of any AMA1 structure to date with more than 97.5% of the ectodomain unambiguously modeled. Comparative sequence analysis reveals discrete segments in TgAMA1 that map to areas of established functional importance in AMA1 from Plasmodium vivax (PvAMA1) and falciparum (PfAMA1). Inspection of the TgAMA1 structure reveals a network of apical surface loops, reorganized in both size and chemistry relative to Pv/PfAMA1, that appear to serve as structural filters restricting access to a central hydrophobic groove. The terminal portion of this groove is formed by an extended loop from DII that is fourteen residues shorter in TgAMA1. A pair of tryptophan residues (Trp353 and Trp354) anchor the DII loop in the hydrophobic groove and frame a conserved tyrosine (Tyr230) forming a contiguous surface that may be critical for MJ assembly. The minimalist DIII structure folds into a cystine knot that likely stabilizes and orients the bulk of the ectodmain without providing excess surface area to which invasion inhibitory antibodies can be generated. The detailed structural characterization of TgAMA1 provides valuable insight into the mechanism of host cell invasion by T. gondii.

PMID: 20304917 [PubMed - as supplied by publisher]

Saturday, March 20, 2010

Activation of the P2X7 receptor triggers the elimination of Toxoplasma gondii tachyzoites from infected macrophages

Microbes Infect. 2010 Mar 15. [Epub ahead of print]

Activation of the P2X7 receptor triggers the elimination of Toxoplasma gondii tachyzoites from infected macrophages

Corrêa G, da Silva CM, de Abreu Moreira-Souza AC, Vommaro RC, Coutinho-Silva R.

Laboratory of Immunophysiology, Biophysics Institute Carlos Chagas Filho, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373. 21941-902 Rio de Janeiro- Brazil; Laboratory of Cellular Ultrastructure Hertha Meyer, Biophysics Institute Carlos Chagas Filho, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373. 21941-902 Rio de Janeiro- Brazil.

Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii, which is widespread throughout the world. After active penetration, the parasite is enclosed within a parasitophorous vacuole and survives in the host cell by avoiding, among other mechanisms, lysosomal degradation. A large number of studies have demonstrated the importance of ATP-signalling via the P2X(7) receptor, as a component of the inflammatory response against intracellular pathogens. We here evaluate the effects of extracellular ATP on T. gondii infection of macrophages. ATP treatment inhibits the parasite load and the appearance of large vacuoles in the cytoplasm of intracellular parasites. ROS and NO assays showed that only ROS production is involved with the ATP effects. Immunofluorescence showed colocalization of Lamp1 and SAG1 only after ATP treatment, suggesting the formation of phagolysosomes. The involvement of P2X(7) receptors in T. gondii clearance was confirmed by the use of P2X(7) agonists and antagonists, and by infecting macrophages from P2X(7) receptor-deficient mice. We conclude that parasite elimination might occur following P2X(7) signalling and that novel therapies against intracellular pathogens could take advantage of activation of purinergic signalling. Copyright © 2010. Published by Elsevier SAS.

PMID: 20298798 [PubMed - as supplied by publisher]

Coordinate control of host centrosome position, organelle distribution and migratory response by Toxoplasma gondii via host mTORC2

J Biol Chem. 2010 Mar 17. [Epub ahead of print]

Coordinate control of host centrosome position, organelle distribution and migratory response by Toxoplasma gondii via host mTORC2

Wang Y, Weiss LM, Orlofsky A.

Albert Einstein College of Medicine, United States.

The invasion of host cells by Toxoplasma gondii is accompanied by a reorganization of host cell structure, in which the host centrosome and Golgi apparatus are localized to the vacuole, and mitochondria, microtubules and endolysosomes are recruited to the vacuole perimeter. The mechanism and functional significance of this process have not been well defined. Here we report that the centrosome-vacuole association was abolished in mTORC2-deficient cells, which also displayed a disordered distribution of perivacuolar host mitochondria and lysosomes. Infection of fibroblasts led to stable, mTORC2-dependent activation of Akt, and Akt inhibition mimicked the effect of mTORC2 ablation on centrosome, mitochondria and lysosome localization. Mobilization of the centrosome by Akt inhibition was abrogated by inhibitors of GSK3, implying that the centrosome is constrained to the vacuole through an mTORC2-Akt-GSK3 pathway. Infected cells were incapable of migration in a wounded monolayer model, and this effect was associated with the inability of centrosomes to reorient in the direction of migration. Both migration and centrosome reorientation were fully restored upon ablation of mTORC2. These findings provide the first linkage of host signals to parasite-mediated host cell reorganization, and demonstrate migratory suppression as a novel functional consequence of this process that is associated with mTORC2-mediated centrosome constraint.

PMID: 20236941 [PubMed - as supplied by publisher]

Thursday, March 18, 2010

Development of a screen to dissect Toxoplasma gondii egress

Mol Biochem Parasitol. 2010 Mar 11. [Epub ahead of print]

Development of a screen to dissect Toxoplasma gondii egress

Eidell KP, Burke T, Gubbels MJ.

Department of Biology, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA.

Toxoplasma gondii egress from the host cell during the lytic part of its life cycle is increasingly appreciated as a process where complex signaling mediates the parasite's response to a variety of internal and external conditions. Although several in vitro as well as physiological triggers have been identified, the molecular nature of these signaling pathways is largely unexplored. To facilitate a more comprehensive analysis of the underlying mechanism we designed a screening procedure to enrich for phenotypes with defects in induced egress. The procedure is based on in vitro induced egress and the efficient separation of intracellular from extracellular parasites. Attachment and fast reinvasion of egressed parasites is prevented by the addition of glycans, whereas PDTC is included to specifically kill the egressed, extracellular parasites. Two available mutants were used to assess the power of the screen; a temperature-sensitive mutant, F-P2, with a conditionally lethal, reversible egress defect, and a mutant wherein the perforin PLP1 is knocked out displaying a constitutive, delayed egress defect. We show that mutant F-P2 can be routinely enriched over 1,000-fold from a wild-type population, whereas the PLP-KO strain cannot be enriched, fitting the underlying phenotypes. The screen efficiency facilitates the isolation of new mutants from mutagenized parasite populations. The use of various egress enhancers will allow genetic dissection of the egress signaling pathways. This is illustrated by a mutant generated using dithitotreitol as an egress enhancer, which displays a defect in dithitotreitol induced egress but not in Ca(2+) ionophore induced egress. Copyright © 2010. Published by Elsevier B.V.

PMID: 20227445 [PubMed - as supplied by publisher]

Toxoplasma gondii: a morphometric analysis of the wall and epithelial cells of pigs intestine

Exp Parasitol. 2010 Mar 13. [Epub ahead of print]

Toxoplasma gondii: a morphometric analysis of the wall and epithelial cells of pigs intestine

da Silva PD, Shiraishi CS, da Silva AV, Gonçalves GF, Sant'ana DD, de Almeida Araújo EJ.

Instituto de Pesquisa Estudos e Ambiência Científica (IPEAC), Universidade Paranaense (UNIPAR), Umuarama, Paraná, Brasil.

The aim of this study was to perform a morphometric analysis of the different layers of the jejunal wall and epithelial cells of pigs with toxoplasmosis. Experiments were conducted using ten 88-day-old crossbred (Pietran x Wessex) pigs divided into two groups: control (n = 5) and experimental (n = 5). The experimental group consisted of animals inoculated orally with 5,000 sporulated oocysts of a genotype III strain of Toxoplasma gondii. At 30 and 60 days following inoculation, the animals were anaesthetised for jejunal biopsy. The intestinal segments were processed routinely for histology. Transverse cuts (4mum thick) were stained with haematoxylin and eosin (HE), Periodic Acid Schiff (PAS), Alcian Blue (AB), pH 2.5, and Alcian Blue (AB), pH 1.0. We observed hypertrophy of the jejunal wall, increased enterocyte height, and a decreased number of intraepithelial lymphocytes in the infected animals. There were no changes in the number of goblet cells. Copyright © 2010. Published by Elsevier Inc.

PMID: 20233593 [PubMed - as supplied by publisher]

Friday, March 12, 2010

Myeloablative Conditioning Predisposes Patients for Toxoplasma gondii Reactivation after Allogeneic Stem Cell Transplantation

Clin Infect Dis. 2010 Mar 10. [Epub ahead of print]

Myeloablative Conditioning Predisposes Patients for Toxoplasma gondii Reactivation after Allogeneic Stem Cell Transplantation

Meers S, Lagrou K, Theunissen K, Dierickx D, Delforge M, Devos T, Janssens A, Meersseman W, Verhoef G, Van Eldere J, Maertens J.

Hematology Department, 2Medical Diagnostic Sciences, and 3Medical Intensive Care Unit and Infectious Diseases unit, Department of General Internal Medicine, University Hospitals Leuven, Leuven, Belgium.

Background. Toxoplasmosis is an often fatal opportunistic infection following allogeneic hematopoietic stem cell transplantation and is largely due to deferred diagnosis. In addition, breakthrough infections occur during prophylaxis with trimethoprim-sulfamethoxazole. Methods. From November 2001 onwards, we routinely monitored all stem cell transplant recipients who were seropositive for Toxoplasma gondii and/or who received a transplant from a donor who was seropositive for T. gondii reactivation by polymerase chain reaction of peripheral blood samples. The aim of this study was to evaluate the incidence of and the risk factors for Toxoplasma reactivation in this population not receiving specific prophylaxis. We also studied the feasibility of a preemptive treatment approach based on this routine monitoring. Results. We report a toxoplasmosis incidence of 8.7% (18 of 208 patients). Twelve patients (5.8%) had a T. gondii infection at diagnosis; 6 patients (2.9%) had Toxoplasma disease, including cerebral toxoplasmosis ([Formula: see text]) and cardiopulmonary toxoplasmosis ([Formula: see text]). We identified myeloablative conditioning and conditioning with high-dose total body irradiation (10-12 Gy) as risk factors for T. gondii reactivation, whereas patients with a seropositive donor were less likely to experience reactivation. Patients with T. gondii disease had a significantly higher number of transcripts in blood than did patients with a T. gondii infection. Finally, with a strategy of routine monitoring and preemptive treatment with clindamycin-pyrimethamine, we only had 3 Toxoplasma-related deaths among our patients, which is a much lower rate than that reported in the literature. Conclusions. Systematic monitoring with polymerase chain reaction is a good means to detect T. gondii reactivation and could reduce T. gondii-related mortality among hematopoietic stem cell transplant recipients.

PMID: 20218875 [PubMed - as supplied by publisher]

Redundant and Pathogenic Roles for IL-22 in Mycobacterial, Protozoan, and Helminth Infections

J Immunol. 2010 Mar 10. [Epub ahead of print]

Redundant and Pathogenic Roles for IL-22 in Mycobacterial, Protozoan, and Helminth Infections

Wilson MS, Feng CG, Barber DL, Yarovinsky F, Cheever AW, Sher A, Grigg M, Collins M, Fouser L, Wynn TA.

Immunopathogensis Section.

IL-22 is a member of the IL-10 cytokine family and signals through a heterodimeric receptor composed of the common IL-10R2 subunit and the IL-22R subunit. IL-10 and IL-22 both activate the STAT3 signaling pathway; however, in contrast to IL-10, relatively little is known about IL-22 in the host response to infection. In this study, using IL-22(-/-) mice, neutralizing Abs to IL-22, or both, we show that IL-22 is dispensable for the development of immunity to the opportunistic pathogens Toxoplasma gondii and Mycobacterium avium when administered via the i.p. or i.v. route, respectively. IL-22 also played little to no role in aerosol infections with Mycobacterium tuberculosis and in granuloma formation and hepatic fibrosis following chronic percutaneous infections with the helminth parasite Schistosoma mansoni. A marked pathogenic role for IL-22 was, however, identified in toxoplasmosis when infections were established by the natural oral route. Anti-IL-22 Ab-treated mice developed significantly less intestinal pathology than control Ab-treated mice even though both groups displayed similar parasite burdens. The decreased gut pathology was associated with reduced IL-17A, IL-17F, TNF-alpha, and IFN-gamma expression. In contrast to the prior observations of IL-22 protective effects in the gut, these distinct findings with oral T. gondii infection demonstrate that IL-22 also has the potential to contribute to pathogenic inflammation in the intestine. The IL-22 pathway has emerged as a possible target for control of inflammation in certain autoimmune diseases. Our findings suggest that few if any infectious complications would be expected with the suppression of IL-22 signaling.

PMID: 20220096 [PubMed - as supplied by publisher]

Wednesday, March 10, 2010

Annual burden of ocular toxoplasmosis in the United States

Am J Trop Med Hyg. 2010 Mar;82(3):464-5.

Annual burden of ocular toxoplasmosis in the United States

Jones JL, Holland GN.

Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at University of California at Los Angeles, Los Angeles, California.

Toxoplasmosis is the most common retinal infection in the United States, and it can severely impact vision. We used data from population-based studies, outbreaks, and the U.S. census to estimate the burden of Toxoplasma gondii infection and ocular toxoplasmosis. We estimate that 1,075,242 persons are infected with T. gondii, 21,505 persons have ocular lesions (both asymptomatic and symptomatic), and 4,839 (range = 2,150-7,527) persons develop symptomatic ocular toxoplasmosis each year in the United States. Toxoplasmosis contributes a significant burden to eye disease in the United States.

PMID: 20207874 [PubMed - in process]

Infection in systemic lupus erythematosus: friend or foe?

Int J Clin Rheumtol. 2010 Feb 1;5(1):59-74.

Infection in systemic lupus erythematosus: friend or foe?

Francis L, Perl A.

Division of Rheumatology, Department of Medicine State University of New York, College of Medicine 750 East Adams Street Syracuse, New York 13210, USA.

Infectious agents have long been implicated in the pathogenesis of systemic lupus erythematosus. Common viruses, such as the Epstein-Barr virus, transfusion transmitted virus, parvovirus and cytomegalovirus, have an increased prevalence in patients with systemic lupus erythematosus. They may contribute to disease pathogenesis through triggering autoimmunity via structural or functional molecular mimicry, encoding proteins that induce cross-reactive immune responses to self antigens or modulate antigen processing, activation, or apoptosis of B and T cells, macrophages or dendritic cells. Alternatively, some infectious agents, such as malaria, Toxoplasma gondii and Helicobacter pylori, may have a protective effect. Vaccinations may play dual roles by protecting against friend and foe alike.

PMID: 20209114 [PubMed]

Toxoplasma secreting Cre recombinase for analysis of host-parasite interactions

Nat Methods. 2010 Mar 7. [Epub ahead of print]

Toxoplasma secreting Cre recombinase for analysis of host-parasite interactions

Koshy AA, Fouts AE, Lodoen MB, Alkan O, Blau HM, Boothroyd JC.

[1] Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA. [2] Division of Infectious Disease, Department of Internal Medicine, Stanford University School of Medicine, Stanford, California, USA.

We describe a Toxoplasma gondii strain that will permit the use of site-specific recombination to study the host-parasite interactions of this organism. This Toxoplasma strain efficiently injects a Cre fusion protein into host cells. In a Cre-reporter cell line, a single parasite invasion induced Cre-mediated recombination in 95% of infected host cells. By infecting Cre-reporter mice with these parasites, we also monitored host-cell infection in vivo.

PMID: 20208532 [PubMed - as supplied by publisher]

Sunday, March 07, 2010

Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention

Trends Parasitol. 2010 Mar 2. [Epub ahead of print]

Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention

Elmore SA, Jones JL, Conrad PA, Patton S, Lindsay DS, Dubey JP.

Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 1601 Campus Delivery, Fort Collins, CO 80523, USA.

Toxoplasma gondii is a parasite of birds and mammals. Cats are the only definitive host and thus the only source of infective oocysts, but other mammals and birds can develop tissue cysts. Although feline infections are typically asymptomatic, infection during human pregnancy can cause severe disease in the fetus. Cat owners can reduce their pets' exposure risk by keeping all cats indoors and not feeding them raw meat. Humans usually become infected through ingestion of oocyst-contaminated soil and water, tissue cysts in undercooked meat, or congenitally. Because of their fastidious nature, the passing of non-infective oocysts, and the short duration of oocyst shedding, direct contact with cats is not thought to be a primary risk for human infection. Copyright © 2010 Elsevier Ltd. All rights reserved.

PMID: 20202907 [PubMed - as supplied by publisher]

Friday, March 05, 2010

DNA topoisomerases in apicomplexan parasites: promising targets for drug discovery

Proc Biol Sci. 2010 Mar 3. [Epub ahead of print]

DNA topoisomerases in apicomplexan parasites: promising targets for drug discovery

García-Estrada C, Prada CF, Fernández-Rubio C, Rojo-Vázquez F, Balaña-Fouce R.

Departamento de Ciencias Biomédicas (INTOXCAL), Universidad de León, , Campus de Vegazana s/n, 24071 León, Spain.

The phylum Apicomplexa includes a large group of protozoan parasites responsible for a wide range of animal and human diseases. Destructive pathogens, such as Plasmodium falciparum and Plasmodium vivax, causative agents of human malaria, Cryptosporidium parvum, responsible of childhood diarrhoea, and Toxoplasma gondii, responsible for miscarriages and abortions in humans, are frequently associated with HIV immunosuppression in AIDS patients. The lack of effective vaccines, along with years of increasing pressure to eradicate outbreaks with the use of drugs, has favoured the formation of multi-drug resistant strains in endemic areas. Almost all apicomplexan of medical interest contain two endosymbiotic organelles that contain their own mitochondrial and apicoplast DNA. Apicoplast is an attractive target for drug testing because in addition to harbouring singular metabolic pathways absent in the host, it also has its own transcription and translation machinery of bacterial origin. Accordingly, apicomplexan protozoa contain an interesting mixture of enzymes to unwind DNA from eukaryotic and prokaryotic origins. On the one hand, the main mechanism of DNA unwinding includes the scission of one-type I-or both DNA strands-type II eukaryotic topoisomerases, establishing transient covalent bonds with the scissile end. These enzymes are targeted by camptothecin and etoposide, respectively, two natural drugs whose semisynthetic derivatives are currently used in cancer chemotherapy. On the other hand, DNA gyrase is a bacterial-borne type II DNA topoisomerase that operates within the apicoplast and is effectively targeted by bacterial antibiotics like fluoroquinolones and aminocoumarins. The present review is an update on the new findings concerning topoisomerases in apicomplexan parasites and the role of these enzymes as targets for therapeutic agents.

PMID: 20200034 [PubMed - as supplied by publisher]

IL-10 production by CD4(+) effector T cells: a mechanism for self-regulation

Mucosal Immunol. 2010 Mar 3. [Epub ahead of print]

IL-10 production by CD4(+) effector T cells: a mechanism for self-regulation

Jankovic D, Kugler DG, Sher A.

Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.

The development of Th1 lymphocytes is essential for cell-mediated immunity and resistance against intracellular pathogens. However, if left unregulated, the same response can cause serious damage to host tissues and lead to mortality. A number of different paracrine regulatory mechanisms involving distinct myeloid and lymphoid subpopulations have been implicated in controlling excessive secretion of inflammatory cytokines by Th1 cells. Much of this work has focused on interleukin (IL)-10, a cytokine with broad anti-inflammatory properties, one of which is to counteract the function of Th1 lymphocytes. While studying the role of IL-10 in regulating immunopathology during infection with the intracellular parasite Toxoplasma gondii, we discovered that the host-protective IL-10 derives in an autocrine manner from conventional interferon-gamma (IFN-gamma)-producing T-bet(+) Foxp3(neg) Th1 cells. In the following review, we will discuss these findings that support the general concept that production of IL-10 is an important self-regulatory function of CD4(+) T lymphocytes.Mucosal Immunology advance online publication 3 March 2010. doi:10.1038/mi.2010.8.

PMID: 20200511 [PubMed - as supplied by publisher]

Thursday, March 04, 2010

Treatment of toxoplasmic lymphadenitis with co-trimoxazole: double-blind, randomized clinical trial

Int J Infect Dis. 2010 Feb 27. [Epub ahead of print]

Treatment of toxoplasmic lymphadenitis with co-trimoxazole: double-blind, randomized clinical trial

Alavi SM, Alavi L.

Joundishapour Infectious and Tropical Diseases Research Center, Infectious Disease Ward, Razi Hospital, Joundishapour University of Medical Sciences, No. 52, West 11 Avenue, Kianabad, Ahvaz, Iran.

BACKGROUND: Lymphadenitis is one of the presenting signs of toxoplasmosis. Co-trimoxazole (CTM) has a good therapeutic effect on ocular and cerebral infections caused by Toxoplasma gondii. Since this infection is endemic in Ahvaz and because of the lack of investigations into the therapeutic effects of CTM in toxoplasmic lymphadenitis (TL), this study was performed from 2005 to 2007 to determine the therapeutic effects of CTM on TL in Ahvaz. METHODS: Forty-six patients with TL were enrolled in this randomized, double-blind, placebo-controlled trial study. Diagnosis was based on clinical examination, serological tests (chemiluminescent), and histopathological examinations. Palpable lymph nodes, IgM >8IU, and follicular hyperplasia were defined as positive findings. Patients were randomly assigned to the comparison groups (23 patients in each group). The CTM patients were treated with 48mg/kg/day CTM divided into two doses, for 1 month. The placebo patients were treated with placebo for 1 month. The primary endpoint for treatment response was 1 month. Follow-up with physical and serological examinations occurred at 6 months. The secondary endpoint was at 6 months. Clinical response was defined as no palpable lymph nodes and serological response as IgM <6IU; a patient was cured if the lymph nodes were no longer palpable and IgM was <6IU. Results were analyzed using SPSS software and the Chi-square test. RESULTS: At the end of treatment, a clinical response was observed in 15 (65.2%) in the CTM group and five (21.7%) in the placebo group. A serological response was seen in 65.2% of the CTM group and 13.0% of the placebo group. The cure rate was 65.2% in the CTM group and 13.1% in the placebo group. There was a significant difference in therapeutic effect between the two groups (52.2%, 95% confidence interval 32.1-72%, p<0.001). There was no difference in the site of infection between the two groups (p>0.05). CONCLUSION: CTM has a good therapeutic effect in TL and may be used in selected patients for whom treatment is required. Copyright © 2010 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

PMID: 20194044 [PubMed - as supplied by publisher]

CCR7 dependent immunity during acute Toxoplasma gondii infection

Infect Immun. 2010 Mar 1. [Epub ahead of print]

CCR7 dependent immunity during acute Toxoplasma gondii infection

Noor S, Habashy AS, Nance JP, Clark RE, Nemati K, Carson MJ, Wilson EH.

Division of Biomedical Sciences, University of California, Riverside, CA 92521, USA.

The chemokine receptor CCR7 is a well established homing receptor for dendritic cells and T cells. Interactions with its ligands CCL19 and CCL21 facilitate priming of immune responses in lymphoid tissue yet CCR7-independent immune responses can be generated in the presence of sufficient antigen. In these studies we investigated the role of CCR7 signaling in the generation of protective immune responses to the intracellular protozoan parasite, Toxoplasma gondii. Results demonstrate a significant increase in the expression of CCL19, CCL21 and CCR7 in peripheral and CNS tissue over the course of infection. Unexpectedly, despite the presence of abundant antigen, CCR7 was an absolute requirement for protective immunity to T. gondii as CCR7(-/-) mice succumbed to the parasite early in the acute phase of infection. Although serum levels of IL-12, IL-6, TNF-alpha, and IL-10 remained unchanged there was a significant decrease in CCL2/MCP-1 and inflammatory monocyte recruitment to the site of infection. In addition, CCR7(-/-) mice failed to produce sufficient IFN-gamma, a critical Th1 associated effector cytokine required to control parasite replication. As a result there was increased parasite dissemination and a significant increase in parasite burden in the lung, liver and brains of infected mice. Adoptive transfer experiments revealed that expression of CCR7 on the T cell compartment alone is sufficient to enable T cell priming, increase IFN-gamma production and allow survival of CCR7(-/-) mice. These data demonstrate an absolute requirement for T cell expression of CCR7 for the generation of protective immune responses to Toxoplasma infection.

PMID: 20194594 [PubMed - as supplied by publisher]

Wednesday, March 03, 2010

Prime and boost immunization with influenza and adenovirus encoding the Toxoplasma gondii surface antigen 2 (SAG2) induces strong protective immunity

Vaccine. 2010 Feb 25. [Epub ahead of print]

Prime and boost immunization with influenza and adenovirus encoding the Toxoplasma gondii surface antigen 2 (SAG2) induces strong protective immunity

Machado AV, Caetano BC, Barbosa RP, Salgado AP, Rabelo RH, Garcia CC, Bruna-Romero O, Escriou N, Gazzinelli RT.

Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte 31270-910, MG, Brazil; Centro de Pesquisas René Rachou, FIOCRUZ, Belo Horizonte 30190-002, MG, Brazil.

In this work, we explored an original vaccination protocol using recombinant influenza and adenovirus. We constructed recombinant influenza viruses harboring dicistronic NA segments containing the surface antigen 2 (SAG2) from Toxoplasma gondii under control of the duplicated 3' promoter. Recombinant influenza viruses were able to drive the expression of the foreign SAG2 sequence in cell culture and to replicate efficiently both in cell culture and in lungs of infected mice. In addition, mice primed with recombinant influenza virus and boosted with a recombinant adenovirus encoding SAG2 elicited both humoral and cellular immune responses specific for SAG2. Moreover, when immunized animals were challenged with the cystogenic P-Br strain of T. gondii, they displayed up to 85% of reduction in parasite burden. These results demonstrate the potential use of recombinant influenza vectors harboring the dicistronic segments in the development of vaccines against infectious diseases. Copyright © 2010 Elsevier Ltd. All rights reserved.

PMID: 20189485 [PubMed - as supplied by publisher]

Monday, March 01, 2010

Evaluation of drug effects on Toxoplasma gondii nuclear and plastid DNA replication using real-time PCR

Parasitol Res. 2010 Feb 26. [Epub ahead of print]

Evaluation of drug effects on Toxoplasma gondii nuclear and plastid DNA replication using real-time PCR

Zhao Q, Zhang M, Hong L, Zhou K, Lin Y.

School of Life Sciences, Xiamen University, Xiamen, Fujian, China, 361005, zhaoqingxm@yahoo.cn.

Toxoplasma gondii Nicolle and Manceaux, 1908 is a unicellular protozoan that can infect a broad spectrum of organisms including humans. In addition to a nuclear genome, it also carries a circular DNA within a plastid-like organelle (apicoplast) and a linear genome within its mitochondria. The plastid organelle has been shown to be the target of various anti-parasitic drugs or antibiotics. To evaluate the effects of agents on the DNA replication of T. gondii, we tested six drugs (ciprofloxacin, acetylspiramycin, clindamycin, azithromycin, artemether, and sulfadiazine) on the parasite cultured in Hela cells. After drug treatment for 48 h, the parasite growth and DNA replication were evaluated and quantitated using TaqMan real-time quantitative PCR with oligonucleotide primers synthesized based on a gene from the apicoplast genome (ycf24, Genbank accession no. U87145) and a gene from the nuclear genome (uprt, Genbank accession no. U10246). Our results showed that ciprofloxacin was the most effective in inhibiting the replication of the plastid DNA after 48 h drug treatment, with a reduction of 22% in the copy number of the plastid DNA. Artemether was the most effective drug in suppressing the proliferation of tachyzoites. This study also demonstrates that real-time quantitative PCR is a simple and useful technique for monitoring parasite growth and DNA replication.

PMID: 20186551 [PubMed - as supplied by publisher]