Friday, September 28, 2012

Toxoplasmosis and neuropsychiatric diseases: can serological studies establish a clear relationship?

Neurol Sci. 2012 Sep 26. [Epub ahead of print]

Toxoplasmosis and neuropsychiatric diseases: can serological studies establish a clear relationship?

Fabiani S, Pinto B, Bruschi F.

Department of Experimental Pathology, M.B.I.E., School of Medicine, Università di Pisa, Via Roma, 55, Pisa, Italy.

Toxoplasmosis is a widespread infection, with clinical spectrum ranging from a completely asymptomatic infection to multi-organ involvement. After entering the body, the parasite forms tissue cysts and establishes a chronic infection, involving also the central nervous system (CNS). During the last years, a lot of research has focused on the possible link between exposure to T. gondii and development of neuropsychiatric disorders such as schizophrenia and Parkinson's disease (PD). If a firm association between Toxoplasma infection and neuropsychiatric disorders will be established, this would lead to novel strategies for their prevention and treatment. We will review data from serological and neurodevelopment studies relating infection with T. gondii to such neuropsychiatric diseases.

PMID: 23010876 [PubMed - as supplied by publisher]

Protective efficacy of a Toxoplasma gondii ROP13 plasmid DNA vaccine in mice

Clin Vaccine Immunol. 2012 Sep 26. [Epub ahead of print]

Protective efficacy of a Toxoplasma gondii ROP13 plasmid DNA vaccine in mice

Wang PY, Yuan ZG, Petersen E, Li J, Zhang XX, Li XZ, Li HX, Lv ZC, Cheng T, Ren D, Yang GL, Lin RQ, Zhu XQ.

State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province 730046, People's Republic of China.

Toxoplasma gondii is an obligate intracellular parasite infecting humans and any warm-blooded animals, resulting in serious public health problems and economic losses worldwide. Rhoptries are involved in T. gondii invasion and host cell interaction, which have been implicated as important virulence factors. In the present study, a DNA vaccine expressing rhoptry protein 13 (ROP13) of T. gondii inserted into eukaryotic expression vector pVAX I,was constructed, and the immune protection it induced in Kunming mice was evaluated. Kunming mice were immunized intramuscularly with pVAX-ROP13 and/or with IL-18. After that, we evaluated the immune response using lymphoproliferative assay, cytokine and antibody measurements, and the survival times of mice challenged with the virulent T. gondii RH strain (Type I) and the cyst-forming PRU strain (Type II). The results showed that pVAX-ROP13 alone or with pVAX/IL-18 induced a high level of specific anti-T. gondii antibodies and specific lymphocyte proliferative responses. Co-injection of pVAX/IL-18 significantly increased the production of IFN-γ, IL-2, IL-4 and IL-10. Further, challenge experiments showed that co-immunization of pVAX-ROP13 with pVAX/IL-18 significantly (P < 0.05) increased survival time (32.3 ± 2.7 days) compared with pVAX-ROP13 alone (24.9 ± 2.3 days). Immunized mice challenged with T. gondii cysts (PRU strain), had a significant reduction in the number of brain cysts, suggesting that ROP13 could trigger a strong humoral and cellular response against T. gondii cyst infection and is a potential vaccine candidate against toxoplasmosis, which provided foundation for further development of effective vaccines against T. gondii.

PMID: 23015648 [PubMed - as supplied by publisher]

β-1,3-Glucan, Which Can Be Targeted by Drugs, Forms a Trabecular Scaffold in the Oocyst Walls of Toxoplasma and Eimeria

MBio. 2012 Sep 25;3(5). pii: e00258-12. doi: 10.1128/mBio.00258-12. Print 2012.

β-1,3-Glucan, Which Can Be Targeted by Drugs, Forms a Trabecular Scaffold in the Oocyst Walls of Toxoplasma and Eimeria

Bushkin GG, Motari E, Magnelli P, Gubbels MJ, Dubey JP, Miska KB, Bullitt E, Costello CE, Robbins PW, Samuelson J.

Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts, USA.

ABSTRACT The walls of infectious pathogens, which are essential for transmission, pathogenesis, and diagnosis, contain sugar polymers that are defining structural features, e.g., β-1,3-glucan and chitin in fungi, chitin in Entamoeba cysts, β-1,3-GalNAc in Giardia cysts, and peptidoglycans in bacteria. The goal here was to determine in which of three walled forms of Toxoplasma gondii (oocyst, sporocyst, or tissue cyst) is β-1,3-glucan, the product of glucan synthases and glucan hydrolases predicted by whole-genome sequences of the parasite. The three most important discoveries were as follows. (i) β-1,3-glucan is present in oocyst walls of Toxoplasma and Eimeria (a chicken parasite that is a model for intestinal stages of Toxoplasma) but is absent from sporocyst and tissue cyst walls. (ii) Fibrils of β-1,3-glucan are part of a trabecular scaffold in the inner layer of the oocyst wall, which also includes a glucan hydrolase that has a novel glucan-binding domain. (iii) Echinocandins, which target the glucan synthase and kill fungi, arrest development of the Eimeria oocyst wall and prevent release of the parasites into the intestinal lumen. In summary, β-1,3-glucan, which can be targeted by drugs, is an important component of oocyst walls of Toxoplasma but is not a component of sporocyst and tissue cyst walls. IMPORTANCE We show here that walls of Toxoplasma oocysts, the infectious stage shed by cats, contain β-1,3-glucan, a sugar polymer that is a major component of fungal walls. In contrast to fungi, β-1,3-glucan is part of a trabecular scaffold in the inner layer of the oocyst wall that is independent of the permeability barrier formed by the outer layer of the wall. While glucan synthase inhibitors kill fungi, these inhibitors arrest the development of the oocyst walls of Eimeria (an important chicken pathogen that is a surrogate for Toxoplasma) and block release of oocysts into the intestinal lumen. The absence of β-1,3-glucan in tissue cysts of Toxoplasma suggests that drugs targeted at the glucan synthase might be used to treat Eimeria in chickens but not to treat Toxoplasma in people.

PMID: 23015739 [PubMed - in process]

In vitro culture systems for the study of apicomplexan parasites in farm animals

Int J Parasitol. 2012 Sep 20. pii: S0020-7519(12)00214-7. doi: 10.1016/j.ijpara.2012.08.004. [Epub ahead of print]

In vitro culture systems for the study of apicomplexan parasites in farm animals.

Müller J, Hemphill A.

Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland. Electronic address:

In vitro culture systems represent powerful tools for the study of apicomplexan parasites such as Cryptosporidium, Eimeria, Sarcocystis, Neospora, Toxoplasma, Besnoitia, Babesia and Theileria, all with high relevance for farm animals. Proliferative stages of these parasites have been cultured in vitro employing a large variety of cell culture and explant approaches. For some, such as Cryptosporidium and Eimeria, the sexual development has been reproduced in cell cultures, while for others, animal experimentation is required to fulfill the life cycle. In vitro cultures have paved the way to exploit the basic biology of these organisms, and had a major impact on the development of tools for diagnostic purposes. With the aid of in vitro cultivation, studies on host-parasite interactions, on factors involved in innate resistance, stage conversion and differentiation, genetics and transfection technology, vaccine candidates and drug effectiveness could be carried out. The use of transgenic parasites has facilitated high-throughput screening of anti-microbial compounds that are active against the proliferative stages. Here, we review the basic features of cell culture-based in vitro systems for apicomplexan parasites that are relevant for farm animals, and discuss their applications with a focus on drug identification and studies of stage differentiation.

PMID: 23000674 [PubMed - as supplied by publisher]

Screening for small molecule inhibitors of Toxoplasma gondii

Expert Opin Drug Discov. 2012 Sep 24. [Epub ahead of print]

Screening for small molecule inhibitors of Toxoplasma gondii

Kortagere S.

Drexel University College of Medicine, Institute for Molecular Medicine, Department of Microbiology and Immunology , 2900, Queen Lane, PA 19129 , USA

Introduction: Toxoplasma gondii, the agent that causes toxoplasmosis, is an opportunistic parasite that infects many mammalian species. It is an obligate intracellular parasite that causes severe congenital neurological and ocular disease mostly in immunocompromised humans. The current regimen of therapy includes only a few medications that often lead to hypersensitivity and toxicity. In addition, there are no vaccines available to prevent the transmission of this agent. Therefore, safer and more effective medicines to treat toxoplasmosis are urgently needed. Areas covered: The author presents in silico and in vitro strategies that are currently used to screen for novel targets and unique chemotypes against T. gondii. Furthermore, this review highlights the screening technologies and characterization of some novel targets and new chemical entities that could be developed into highly efficacious treatments for toxoplasmosis. Expert opinion: A number of diverse methods are being used to design inhibitors against T. gondii. These include ligand-based methods, in which drugs that have been shown to be efficacious against other Apicomplexa parasites can be repurposed to identify lead molecules against T. gondii. In addition, structure-based methods use currently available repertoire of structural information in various databases to rationally design small-molecule inhibitors of T. gondii. Whereas the screening methods have their advantages and limitations, a combination of methods is ideally suited to design small-molecule inhibitors of complex parasites such as T. gondii.

PMID: 22998671 [PubMed - as supplied by publisher]

New naphthoquinones and an alkaloid with in vitro activity against Toxoplasma gondii RH and EGS strains

Exp Parasitol. 2012 Sep 18. pii: S0014-4894(12)00263-9. doi: 10.1016/j.exppara.2012.09.003. [Epub ahead of print]

New naphthoquinones and an alkaloid with in vitro activity against Toxoplasma gondii RH and EGS strains

Ferreira RA, Oliveira AB, Gualberto SA, Miguel Del Corral JM, Fujiwara RT, Guimarães PH, Vitor RW.

Laboratório de Microscopia, Instituto de Ciências Agrárias, Faculdade de Estudos Administrativos, FEAD, Brazil; Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Brazil.

The efficacy of three amino-terpenyl naphthoquinones and the alkaloid liriodenine were examined against tachyzoites and tissues cysts of the RH and EGS strains, respectively. Monolayers of 2C4 fibroblasts infected with tachyzoites of the RH strain were incubated with different concentrations of the compounds for 48 hours. Specifically, 7-(4-methyl-3-pentenyl)-2-pyrrolidine-[1,4]-naphthoquinone (QUI-5), 6-(4-methyl-3-pentenyl)-2-pyrrolidine-[1,4]-naphthoquinone (QUI-6), 6-(4-methylpentyl)-2-pyrrolidine-[1,4]-naphthoquinone (QUI-11), and (8 h-benzo[g]-1,3-benzodioxolo[6,5,4-de]quinolin-8-one,9Cl-1,2-methylene dioxiaporfina (liriodenine) inhibited intracellular replication of T. gondii. The IC(50) values obtained for compounds QUI-5 and QUI-6 were 69.35 μM and 172.81 μM (i.e., 21.4 μg/mL and 53.4 μg/mL), respectively. The naphthoquinone QUI-11 and liriodenine significantly inhibited intracellular replication of T. gondii. The IC(50) values obtained with these experiments were 0.32 μM and 0.07 μM (i.e., 0.1 μg/mL and 0.02 μg/mL), respectively. Compounds QUI-5, QUI-6, QUI-11 and liriodenine demonstrated lower toxicity for 2C4 fibroblasts compared to atovaquone. In addition, cysts isolated from the brains of mice chronically infected with the EGS strain were exposed to the compounds. Infectivity of the cysts after incubation with the compounds was assessed by infection of mice. The data obtained showed that in vitro incubation with QUI-6, QUI-11 and liriodenine inhibited the infectivity of the bradyzoites. This activity was time- and concentration-dependent.

PMID: 23000485 [PubMed - as supplied by publisher]

Virulence factors of Toxoplasma gondii

Microbes Infect. 2012 Sep 21. pii: S1286-4579(12)00222-5. doi: 10.1016/j.micinf.2012.09.005. [Epub ahead of print]

Virulence factors of Toxoplasma gondii

Dubremetz JF, Lebrun M.

UMR5235 CNRS-Université de Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France. Electronic address:

Toxoplasma gondii virulence is dependent on factors involved in either parasite-host cell interaction, or in host immune response. It is essentially defined in the mouse and little is known concerning human infection. The genetic dependence of virulence is a growing field, benefiting from the recent development of research of the population structure of T. gondii.

PMID: 23006855 [PubMed - as supplied by publisher]

Wednesday, September 19, 2012

The molecular basis for the distinct host and tissue tropisms of coccidian parasites

Mol Biochem Parasitol. 2012 Sep 7. pii: S0166-6851(12)00217-4. doi: 10.1016/j.molbiopara.2012.08.007. [Epub ahead of print]

The molecular basis for the distinct host and tissue tropisms of coccidian parasites

Cowper B, Matthews S, Tomley F.

Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.

The phylum Apicomplexa is home to a variety of parasites of significant medical and economic relevance, including the coccidian species Toxoplasma gondii, Neospora caninum and Eimeria tenella. In spite of their shared ancestry, the aforementioned coccidian species exhibit highly variable host and tissue tropisms; whilst T. gondii invades a broad spectrum of cell types and host organisms, E. tenella infection is restricted to the small intestine in chicken. Apicomplexans are obligatory intracellular parasites, and are uniquely adapted for host cell invasion via several conserved features. The process of initial host cell recognition and attachment is governed by the regulated deployment of surface microneme proteins (MICs), which therefore are likely to be major determinants of the host and tissue tropism of each parasite. Structural and functional data is now available for several coccidian MICs, providing insights into their receptor specificities and modes of recognition in atomic detail. Here, detailed analysis of these data has been performed, encouraging rationalization of the marked differences in the host and tissue tropism. We have observed that T. gondii expresses a wide repertoire of MICs, binding a broad range of oligosaccharide epitopes, including a unique preference for a α2,9-disialyl terminated receptor. By contrast, the MIC repertoire of Neospora caninum appears to be more restrictive, and even further so in E. tenella, correlating with the reduced tropisms of these parasites.
PMID: 22982139 [PubMed - as supplied by publisher]

Annual cost of illness and quality-adjusted life year losses in the United States due to 14 foodborne pathogens

J Food Prot. 2012 Jul;75(7):1292-302.

Annual cost of illness and quality-adjusted life year losses in the United States due to 14 foodborne pathogens

Hoffmann S, Batz MB, Morris JG Jr.

U.S. Department of Agriculture, Economic Research Service, 355 E Street S.W., Washington, D.C. 20024, USA.

In this article we estimate the annual cost of illness and quality-adjusted life year (QALY) loss in the United States caused by 14 of the 31 major foodborne pathogens reported on by Scallan et al. (Emerg. Infect. Dis. 17:7-15, 2011), based on their incidence estimates of foodborne illness in the United States. These 14 pathogens account for 95 % of illnesses and hospitalizations and 98 % of deaths due to identifiable pathogens estimated by Scallan et al. We estimate that these 14 pathogens cause $14.0 billion (ranging from $4.4 billion to $33.0 billion) in cost of illness and a loss of 61,000 QALYs (ranging from 19,000 to 145,000 QALYs) per year. Roughly 90 % of this loss is caused by five pathogens: nontyphoidal Salmonella enterica ($3.3 billion; 17,000 QALYs), Campylobacter spp. ($1.7 billion; 13,300 QALYs), Listeria monocytogenes ($2.6 billion; 9,400 QALYs), Toxoplasma gondii ($3 billion; 11,000 QALYs), and norovirus ($2 billion; 5,000 QALYs). A companion article attributes losses estimated in this study to the consumption of specific categories of foods. To arrive at these estimates, for each pathogen we create disease outcome trees that characterize the symptoms, severities, durations, outcomes, and likelihoods of health states associated with that pathogen. We then estimate the cost of illness (medical costs, productivity loss, and valuation of premature mortality) for each pathogen. We also estimate QALY loss for each health state associated with a given pathogen, using the EuroQol 5D scale. Construction of disease outcome trees, outcome-specific cost of illness, and EuroQol 5D scoring are described in greater detail in a second companion article.

PMID: 22980013

CD73-generated adenosine facilitates Toxoplasma gondii differentiation to long-lived tissue cysts in the central nervous system

Proc Natl Acad Sci U S A. 2012 Sep 17. [Epub ahead of print]

CD73-generated adenosine facilitates Toxoplasma gondii differentiation to long-lived tissue cysts in the central nervous system.

Mahamed DA, Mills JH, Egan CE, Denkers EY, Bynoe MS.

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

Toxoplasma gondii is an obligate intracellular protozoan pathogen that traffics to the central nervous system (CNS) following invasion of its host. In the CNS, T. gondii undergoes transformation from a rapidly dividing tachyzoite to a long-lived, slow-dividing bradyzoite contained within cysts. The role of extracellular adenosine in T. gondii pathogenesis has not been previously investigated. T. gondii uses host purines such as adenosine for its energy needs, as it is unable to make its own. Here, we show that CD73(-/-) mice, which lack the ability to generate extracellular adenosine, are protected from T. gondii chronic infection, with significantly fewer cysts and reduced susceptibility to reactivation of infection in the CNS independent of host effector function. Parasite dissemination to the brain was unimpaired in CD73(-/-) hosts, suggesting that the reduced cyst number is due to impaired parasite differentiation in the CNS. Confirming this, T. gondii tachyzoites formed fewer cysts following alkaline pH stress in astrocytes isolated from CD73(-/-) mice compared with wild type, and in fibroblasts treated with a CD73 inhibitor. Cyst formation was rescued in CD73(-/-) astrocytes supplemented with adenosine, but not with adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine. Furthermore, mice lacking adenosine receptors had no defect in cyst formation. Based on these findings, we conclude that CD73 expression promotes Toxoplasma bradyzoite differentiation and cyst formation by a mechanism dependent on the generation of adenosine, but independent of adenosine receptor signaling. Overall, these findings suggest that modulators of extracellular adenosine may be used to develop therapies aimed at defending against human toxoplasmosis.

PMID: 22988118 [PubMed - as supplied by publisher]

Saturday, September 15, 2012

Salicylanilide Inhibitors of Toxoplasma gondii

J Med Chem. 2012 Sep 12. [Epub ahead of print]

Salicylanilide Inhibitors of Toxoplasma gondii.

Fomovska A, Wood RD, Mui E, Dubey JP, Ferriera LR, Hickman MR, Lee PJ, Leed SE, Auschwitz JM, Welsh WJ, Sommerville C, Woods S, Roberts CW, McLeod R.

Toxoplasma gondii (T. gondii) is an apicomplexan parasite that can cause eye disease, brain disease, and death, especially in congenitally infected and immunocompromised people. Novel medicines effective against both active and latent forms of the parasite are greatly needed. The current study focused on the discovery of such medicines by exploring a family of potential inhibitors whose anti-apicomplexan activity has not been previously reported. Initial screening efforts revealed that niclosamide, a drug approved for anti-helmintic use, possessed promising activity in vitro against T. gondii. This observation inspired the evaluation of the activity of a series of salicylanilides and derivatives. Several inhibitors with activities in the nanomolar range with no appreciable in vitro toxicity to human cells were identified. An initial structure-activity relationship was explored. Four compounds were selected for evaluation in an in vivo model of infection, and two derivatives with potentially enhanced pharmacological parameters demonstrated the best activity profiles.

PMID: 22970937

Sunday, September 09, 2012

Immune response and immunopathology during toxoplasmosis.

Semin Immunopathol. 2012 Sep 7. [Epub ahead of print]

Immune response and immunopathology during toxoplasmosis.

Dupont CD, Christian DA, Hunter CA.

Department of Pathobiology, University of Pennsylvania, 380 South University Avenue, Philadelphia, PA, 19104, USA.

Toxoplasma gondii is a protozoan parasite of medical and veterinary significance that is able to infect any warm-blooded vertebrate host. In addition to its importance to public health, several inherent features of the biology of T. gondii have made it an important model organism to study host-pathogen interactions. One factor is the genetic tractability of the parasite, which allows studies on the microbial factors that affect virulence and allows the development of tools that facilitate immune studies. Additionally, mice are natural hosts for T. gondii, and the availability of numerous reagents to study the murine immune system makes this an ideal experimental system to understand the functions of cytokines and effector mechanisms involved in immunity to intracellular microorganisms. In this article, we will review current knowledge of the innate and adaptive immune responses required for resistance to toxoplasmosis, the events that lead to the development of immunopathology, and the natural regulatory mechanisms that limit excessive inflammation during this infection.

PMID: 22955326 [PubMed - as supplied by publisher]

Saturday, September 08, 2012

Does protein phosphorylation govern host cell entry and egress by the Apicomplexa?

Int J Med Microbiol. 2012 Aug 27. [Epub ahead of print]

Does protein phosphorylation govern host cell entry and egress by the Apicomplexa?

Jacot D, Soldati-Favre D.

Department of Microbiology and Molecular Medicine, Faculty of Medicine, CMU, 1 Rue Michel-Servet, 1211 Geneva, Switzerland.

Members of the phylum Apicomplexa are responsible for a wide range of diseases in humans and animals. The absence of an effective vaccine or safe curing drugs and the continuous emergence of resistant parasites to available treatments impose a high demand on the identification of novel targets for intervention against the apicomplexans. Protein kinases are considered attractive potential therapeutic targets not only against cancers but also to combat infectious diseases. The scope and aim of this review is to report on the recent progress in dissecting the impact of protein phosphorylation in regulating motility and invasion.

PMID: 22951234 [PubMed - as supplied by publisher]

Toxoplasma gondii Infection Induces Suppression in a Mouse Model of Allergic Airway Inflammation

PLoS One. 2012;7(8):e43420. Epub 2012 Aug 28.

Toxoplasma gondii Infection Induces Suppression in a Mouse Model of Allergic Airway Inflammation

Fenoy IM, Chiurazzi R, Sánchez VR, Argenziano MA, Soto A, Picchio MS, Martin V, Goldman A.

Centro de Estudios en Salud y Medio Ambiente (CESyMA), Escuela de Ciencia y Tecnología, Universidad Nacional de San Martín, Buenos Aires, Argentina.

Allergic asthma is an inflammatory disorder characterized by infiltration of the airway wall with inflammatory cells driven mostly by activation of Th2-lymphocytes, eosinophils and mast cells. There is a link between increased allergy and a reduction of some infections in Western countries. Epidemiological data also show that respiratory allergy is less frequent in people exposed to orofecal and foodborne microbes such as Toxoplasma gondii. We previously showed that both acute and chronic parasite T. gondii infection substantially blocked development of airway inflammation in adult BALB/c mice. Based on the high levels of IFN-γ along with the reduction of Th2 phenotype, we hypothesized that the protective effect might be related to the strong Th1 immune response elicited against the parasite. However, other mechanisms could also be implicated. The possibility that regulatory T cells inhibit allergic diseases has received growing support from both animal and human studies. Here we investigated the cellular mechanisms involved in T. gondii induced protection against allergy. Our results show for the first time that thoracic lymph node cells from mice sensitized during chronic T. gondii infection have suppressor activity. Suppression was detected both in vitro, on allergen specific T cell proliferation and in vivo, on allergic lung inflammation after adoptive transference from infected/sensitized mice to previously sensitized animals. This ability was found to be contact- independent and correlated with high levels of TGF-β and CD4(+)FoxP3(+) cells.

PMID: 22952678 [PubMed - in process]

Migration of Toxoplasma gondii-Infected Dendritic Cells across Human Retinal Vascular Endothelium

Invest Ophthalmol Vis Sci. 2012 Sep 4. [Epub ahead of print]

Migration of Toxoplasma gondii-Infected Dendritic Cells across Human Retinal Vascular Endothelium.

Furtado JM, Bharadwaj AS, Ashander LM, Olivas A, Smith JR.

Casey Eye Institute, Oregon Health & Science University, United States.

Purpose: Toxoplasma gondii, the parasite responsible for ocular toxoplasmosis, accesses the retina from the bloodstream. We investigated the dendritic cell as a potential taxi for T. gondii tachyzoites moving across the human retinal endothelium, and examined the participation of adhesion molecules and chemokines in this process. Methods: CD14-positive monocytes were isolated from human peripheral blood by antibody-mediated cell enrichment, and cultured in granulocyte-macrophage colony-stimulating factor and interleukin-4 to generate dendritic cells. Transmigration assays were performed over 18 hours in transwells seeded with human retinal endothelial cells and using dendritic cells exposed to laboratory or natural strains of T. gondii tachyzoites. Parasites were tagged with yellow fluorescent protein to verify infection. In some experiments, endothelial monolayers were pre-incubated with antibody directed against adhesion molecules, or chemokine was added to lower chambers of transwells. Results: Human monocyte-derived dendritic cell preparations infected with laboratory or natural strain T. gondii tachyzoites transmigrated in larger numbers across simulated human retinal endothelium than uninfected dendritic cells (p≤0.0004 in 5 of 6 experiments). Antibody blockade of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1 and activated leukocyte cell adhesion molecule (ALCAM) inhibited transmigration (p≤0.001), and CCL21 or CXCL10 increased transmigration (p≤0.03). Conclusions: Transmigration of human dendritic cells across retinal endothelium is increased following infection with T. gondii. Movement may be impacted by locally produced chemokines and is mediated in part by ICAM-1, VCAM-1 and ALCAM. These findings have implications for development of novel therapeutics aimed at preventing retinal infection by T. gondii.

PMID: 22952125 [PubMed - as supplied by publisher]

Thursday, September 06, 2012

Toxoplasma gondii Immunoglobulin G Antibodies and Nonfatal Suicidal Self-Directed Violence

J Clin Psychiatry. 2012 Jul 10. [Epub ahead of print]

Toxoplasma gondii Immunoglobulin G Antibodies and Nonfatal Suicidal Self-Directed Violence

Zhang Y, Träskman-Bendz L, Janelidze S, Langenberg P, Saleh A, Constantine N, Okusaga O, Bay-Richter C, Brundin L, Postolache TT.

Mood and Anxiety Program, Department of Psychiatry, University of Maryland School of Medicine, Baltimore.

The primary aim was to relate Toxoplasma gondii seropositivity and serointensity to scores on the self-rated Suicide Assessment Scale (SUAS-S). Another aim was to reevaluate the previously reported positive association between T gondii serointensity and a history of nonfatal suicidal self-directed violence.
This cross-sectional, observational study compared T gondii serointensity and seropositivity in plasma from 54 adult suicide attempters (inpatients at Lund University Hospital, Lund, Sweden) and 30 adult control subjects (randomly selected from the municipal population register in Lund, Sweden) recruited between 2006 and 2010. The potential of patients and controls for self-directed violence was evaluated with the SUAS-S. Psychiatric diagnoses were made according to DSM-IV criteria. Plasma samples were tested for immunoglobulin G antibodies to T gondii, cytomegalovirus, and herpes simplex virus type 1. Data were analyzed using multivariable logistic regression to investigate the association between T gondii serointensity or seropositivity and a history of nonfatal suicidal self-directed violence; multivariable linear regression was used to explore the relationship between T gondii serointensity or seropositivity and the SUAS-S. Both regression models included sex, age, and body mass index as covariates.
Seropositivity of T gondii (adjusted odds ratio [OR] = 7.12; 95% CI, 1.66-30.6; P = .008) and serointensity of T gondii (adjusted OR = 2.01; 95% CI, 1.09-3.71; P = .03) were positively associated with a history of nonfatal suicidal self-directed violence. Seropositivity of T gondii was associated with higher SUAS-S scores, a relationship significant for the whole sample (P = .026), but not for suicide attempters only. No significant associations with other pathogens were identified.
These results are consistent with previous reports on the association between T gondii infection and nonfatal suicidal self-directed violence. Confirming these results in future large longitudinal studies and including suicide as an outcome may lead to novel individualized approaches in suicide prevention.

 PMID: 22938818 [PubMed - as supplied by publisher]

Host metabolism regulates growth and differentiation of Toxoplasma gondii

Int J Parasitol. 2012 Aug 24. [Epub ahead of print]

Host metabolism regulates growth and differentiation of Toxoplasma gondii

Weilhammer DR, Iavarone AT, Villegas EN, Brooks GA, Sinai AP, Sha WC.

Immunology and Pathogenesis Division, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.

A critical step in the pathogenesis of Toxoplasma gondii is conversion from the fast-replicating tachyzoite form experienced during acute infection to the slow-replicating bradyzoite form that establishes long-lived tissue cysts during chronic infection. Bradyzoite cyst development exhibits a clear tissue tropism in vivo, yet conditions of the host cell environment that influence this tropism remain unclear. Using an in vitro assay of bradyzoite conversion, we have found that cell types differ dramatically in the ability to facilitate differentiation of tachyzoites into bradyzoites. Characterization of cell types that were either resistant or permissive for conversion revealed that resistant cell lines release low molecular weight metabolites that could support tachyzoite growth under metabolic stress conditions and thereby inhibit bradyzoite formation in permissive cells. Biochemical analysis revealed that the glycolytic metabolite lactate is an inhibitory component of supernatants from resistant cells. Furthermore, upregulation of glycolysis in permissive cells through the addition of glucose or by overexpression of the host kinase, Akt, was sufficient to convert cells from a permissive to a resistant phenotype. These results suggest that the metabolic state of the host cell may play a role in determining the predilection of the parasite to switch from the tachyzoite to bradyzoite form.

PMID: 22940576 [PubMed - as supplied by publisher]

Toxoplasma gondii and Cognitive Deficits in Schizophrenia: An Animal Model Perspective

Schizophr Bull. 2012 Sep 1. [Epub ahead of print]

Toxoplasma gondii and Cognitive Deficits in Schizophrenia: An Animal Model Perspective

Kannan G, Pletnikov MV.

Department of Psychiatry and Behavioral Sciences.

Cognitive deficits are a core feature of schizophrenia. Epidemiological evidence indicates that microbial pathogens may contribute to cognitive impairment in patients with schizophrenia. Exposure to Toxoplasma gondii (T. gondii) has been associated with cognitive deficits in humans. However, the mechanisms whereby the parasite impacts cognition remain poorly understood. Animal models of T. gondii infection may aid in elucidating the underpinnings of cognitive dysfunction. Here, we (1) overview the literature on the association of T. gondii infection and cognitive impairment, (2) critically analyze current rodent models of cognitive deficits resulting from T. gondii infection, and (3) explore possible mechanisms whereby the parasite may affect cognitive function.

PMID: 22941742 [PubMed - as supplied by publisher]

A comparative study of small RNAs in Toxoplasma gondii of distinct genotypes

Parasit Vectors. 2012 Sep 3;5(1):186. [Epub ahead of print]

A comparative study of small RNAs in Toxoplasma gondii of distinct genotypes

Wang J, Liu X, Jia B, Lu H, Peng S, Piao X, Hou N, Cai P, Yin J, Jiang N, Chen Q.


Toxoplasma gondii is an intracellular parasite with a significant impact on human health. Inside the mammalian and avian hosts, the parasite can undergo rapid development or remain inactive in the cysts. The mechanism that regulates parasite proliferation has not been fully understood. Small noncoding RNAs (sncRNA) such as microRNAs (miRNAs) are endogenous regulatory factors that can modulate cell differentiation and development. It is anticipated that hundreds of miRNAs regulate the expression of thousands of genes in a single organism. SncRNAs have been identified in T. gondii, however the profiles of sncRNAs expression and their potential regulatory function in parasites of distinct genotypes has largely been unknown.
The transcription profiles of miRNAs in the two genetically distinct strains, RH and ME49, of T. gondii were investigated and compared by a high-through-put RNA sequencing technique and systematic bioinformatics analysis. The expression of some of the miRNAs was confirmed by Northern blot analysis.
1,083,320 unique sequences were obtained. Of which, 17 conserved miRNAs related to 2 metazoan miRNA families and 339 novel miRNAs were identified. A total of 175 miRNAs showed strain-specific expression, of which 155 miRNAs were up-regulated in RH strain and 20 miRNAs were up-regulated in ME49 strain. Strain-specific expression of miRNAs in T. gondii could be due to activation of specific genes at different genomic loci or due to arm-switching of the same pre-miRNA duplex.
Evidence for the differential expression of miRNAs in the two genetically distinct strains of T. gondii has been identified and defined. MiRNAs of T. gondii are more species-specific as compared to other organisms, which can be developed as diagnostic biomarkers for toxoplasmosis. The data also provide a framework for future studies on RNAi-dependent regulatory mechanisms in the zoonotic parasite.

PMID: 22943187

Toxoplasmosis in the fetus and newborn: an update on prevalence, diagnosis and treatmen

Expert Rev Anti Infect Ther. 2012 Jul;10(7):815-28.

Toxoplasmosis in the fetus and newborn: an update on prevalence, diagnosis and treatmen

Moncada PA, Montoya JG.

Department of Medicine and Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA, USA.

Toxoplasma gondii is an unicellular coccidian parasite with worldwide distribution. It is estimated that more than a third of the world's population has been infected with the parasite, but seroprevalence is unevenly distributed across countries and different socioeconomic strata. The majority of newborns with congenital toxoplasmosis do not have any clinical signs of the disease at birth; however, 30-70% of those with clinical abnormalities were not detected initially, and are found to have new retinal lesions consistent with toxoplasmicchorioretinitis later in life. Congenital toxoplasmosis can also cause fetal death, stillbirths or long-term disabling sequelae, particularly among untreated infants. The disease appears to be more frequent and severe at certain latitudes. Congenital toxoplasmosis can be prevented and treated during gestation. Less severe disease is commonly reported in countries where prenatal screening and treatment have been systematically implemented. By contrast, severe disease appears to be observed primarily in infants born to untreated mothers. For definition purposes, it is best to use the term toxoplasma or Toxoplasma gondii infection when referring to asymptomatic patients with primary or chronic infection, and toxoplasmosis when referring to patients with symptoms or signs.
PMID: 22943404 [PubMed - in process]