Toxoplasma's ways of manipulating the host transcriptome via secreted effectors

Curr Opin Microbiol. 2015 Apr 23;26:24-31. doi: 10.1016/j.mib.2015.04.003. [Epub ahead of print]

Hakimi MA¹, Bougdour A².

 

The obligate intracellular parasite Toxoplasma gondii strikes a subtle balance with the host immune system that not only prevents host death but also promotes parasite persistence. Although being enclosed within a parasitophorous vacuole, the parasite actively interfaces with host cell signaling pathways, thereby directing host cell responses. To this end, T. gondii delivers effector proteins into the host cell that co-opt host transcription factors and eventually modulate gene expression. Aside from the secretory Rhoptry organelles initially described as the main source of such effectors, Dense Granules are now recognized as critical in delivering products that remain confined at the vacuolar space or traffic beyond the vacuole membrane to the host cell nucleus and contribute to rewire host gene expression. This review highlights the latest breakthroughs in T. gondii effector discovery and their modus operandi during infection.
Copyright © 2015. Published by Elsevier Ltd.

PMID:

25912924

[PubMed - as supplied by publisher]

Aryloxyethyl Thiocyanates Are Potent Growth Inhibitors of Trypanosoma cruzi and Toxoplasma gondii

ChemMedChem. 2015 Apr 27. doi: 10.1002/cmdc.201500100. [Epub ahead of print]

 

Chao MN¹, Matiuzzi CE, Storey M, Li C, Szajnman SH, Docampo R, Moreno SN, Rodriguez JB.

 

As a part of our project aimed at searching for new safe chemotherapeutic agents against parasitic diseases, several compounds structurally related to the antiparasitic agent WC-9 (4-phenoxyphenoxyethyl thiocyanate), which were modified at the terminal phenyl ring, were designed, synthesized, and evaluated as growth inhibitors against Trypanosoma cruzi, the etiological agent of Chagas disease, and Toxoplasma gondii, the parasite responsible of toxoplasmosis. Most of the synthetic analogues exhibited similar antiparasitic activity and were slightly more potent than our lead WC-9. For example, two trifluoromethylated derivatives exhibited ED₅₀ values of 10.0 and 9.2 μM against intracellular T. cruzi, whereas they showed potent action against tachyzoites of T. gondii (ED₅₀ values of 1.6 and 1.9 μM against T. gondii). In addition, analogues of WC-9 in which the terminal aryl group is in the meta position with respect to the alkyl chain bearing the thiocyanate group showed potent inhibitory action against both T. cruzi and T. gondii at the very low micromolar range, which suggests that a para-phenyl substitution pattern is not necessary for biological activity.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

KEYWORDS:

antiparasitic agents; biological activity; chemotherapeutic agents; inhibitors; structure-activity relationships

PMID:

25914175

[PubMed - as supplied by publisher]

Apicomplexan cell cycle flexibility: centrosome controls the clutch

Trends Parasitol. 2015 Apr 19. pii: S1471-4922(15)00079-3. doi: 10.1016/j.pt.2015.04.003. [Epub ahead of print]

Chen CT1, Gubbels MJ2.

Author information

Abstract

The centrosome serves as a central hub coordinating multiple cellular events in eukaryotes. A recent study in Toxoplasma gondii revealed a unique bipartite structure of the centrosome, which coordinates the nuclear cycle (S-phase and mitosis) and budding cycle (cytokinesis) of the parasite, and deciphers the principle behind flexible apicomplexan cell division modes.

Copyright © 2015. Published by Elsevier Ltd.

KEYWORDS: 

Toxoplasma gondii; apicomplexa; centrosome; endodyogeny; schizogony

PMID:

 

25899747

 

[PubMed - as supplied by publisher]

Characteristics and critical function of CD8+ T cells in the Toxoplasma-infected brain

Semin Immunopathol. 2015 Apr 22. [Epub ahead of print]

Landrith TA1, Harris TH, Wilson EH.

Author information

Abstract

The rise of the AIDS epidemic made the requirement for T cells in our continuous protection from pathogens critically apparent. The striking frequency with which AIDS patients exhibited profound neurological pathologies brought attention to many chronic infections that are latent within the immune-privileged CNS. One of the most common lethal opportunistic infections of these patients was with the protozoan parasite, Toxoplasma gondii. Reactivation of Toxoplasma cysts within the brain causes massive tissue destruction evidenced as multiple ring-enhancing lesions on MRI and is called toxoplasmic encephalitis (TE). TE is not limited to AIDS patients, but rather is a risk for all severely immunocompromised patients, including recipients of chemotherapy or transplant recipients. The lessons learned from these patient populations are supported by T cell depletion studies in mice. Such experiments have demonstrated that CD4+ and CD8+ T cells are required for protection against TE. Although it is clear that these T cell subsets work synergistically to fight infection, much evidence has been generated that suggests CD8+ T cells play a dominant role in protection during chronic toxoplasmosis. In other models of CNS inflammation, such as intracerebral infection with LCMV and experimental autoimmune encephalomyelitis (EAE), infiltration of T cells into the brain is harmful and even fatal. In the brain of the immunocompetent host, the well-regulated T cell response to T. gondii is therefore an ideal model to understand a controlled inflammatory response to CNS infection. This review will examine our current understanding of CD8+ T cells in the CNS during T. gondii infection in regards to the (1) mechanisms governing entry into the brain, (2) cues that dictate behavior within the brain, and (3) the functional and phenotypic properties exhibited by these cells.

PMID:

 

25898888

 

[PubMed - as supplied by publisher]

Adoptive transfer of CD4+Foxp3+ regulatory T cells to C57BL/6J mice during acute infection with Toxoplasma gondii down modulates the exacerbated Th1 immune response

Microbes Infect. 2015 Apr 18. pii: S1286-4579(15)00072-6. doi: 10.1016/j.micinf.2015.04.002. [Epub ahead of print]

Olguín JE1, Fernández J1, Salinas N2, Juárez I3, Rodriguez-Sosa M3, Campuzano J4, Castellanos C1, Saavedra R5.

Author information

Abstract

Infection of C57BL/6J mice with the parasite Toxoplasma gondii triggers a powerful Th1 immune response that is detrimental to the host. During acute infection, a reduction in CD4+Foxp3+ regulatory T cells (Treg) has been reported. We studied the role of Treg during T. gondii infection by adoptive transfer of cells purified from transgenic Foxp3EGFP mice to infected wild type animals. We found a less severe weight loss, a significant delayed mortality in infected Treg-transferred mice, and reduced pathology of the small intestine that were associated with lower IFN-γ and TNF-α levels. Nevertheless, higher cyst number and parasite load in brain were observed in these mice. Treg-transferred infected mice showed reduced levels of both IFN-γ and TNF-α in sera. A reduced number of CD4+ T cells producing IFN-γ was detected in these mice, while IL-2 producing CD4+ T cells were restored to levels nearly similar to uninfected mice. CD25 and CD69 expression of CD4+ T cells were also down modulated. Our data show that the low Treg cell number are insufficient to modulate the activation of CD4+ T cells and the production of high levels of IFN-γ. Thus, a delicate balance between an optimal immune response and its modulation by Treg cells must exist.

Copyright © 2015. Published by Elsevier Masson SAS.

KEYWORDS: 

Regulatory T-Cells; T(h)1 cells; Toxoplasma gondii; adoptive transfer; interferon-gamma

PMID:

 

25899946

 

[PubMed - as supplied by publisher]

Rhomboid Proteases in Invasion and Replication of Apicomplexa

Mol Microbiol. 2015 Apr 21. doi: 10.1111/mmi.13032. [Epub ahead of print]

Stewart RJ1, Tonkin CJ.

Author information

Abstract

In this issue of Molecular Microbiology Rugarabamu and colleagues (Rugarabamu et al., 2015) investigate the role of rhomboid proteases responsible for adhesin shedding during invasion of the Apicomplexan parasite Toxoplasma gondii. This study, together with several other recent publications, raises new questions about the function of these rhomboids in Toxoplasma, whilst also strongly arguing against other recently proposed roles for these proteases.

This article is protected by copyright. All rights reserved.

KEYWORDS: 

Apicomplexa; Invasion; Motility; Plasmodium; Rhomboid; Toxoplasma

PMID:

 

25903290

 

[PubMed - as supplied by publisher] 

Isoprenoid metabolism in apicomplexan parasites

Curr Clin Microbiol Rep. 2014 Dec 1;1(3-4):37-50.

 

Imlay L¹, Odom AR².

 

Apicomplexan parasites include some of the most prevalent and deadly human pathogens. Novel antiparasitic drugs are urgently needed. Synthesis and metabolism of isoprenoids may present multiple targets for therapeutic intervention. The apicoplast-localized methylerythritol phosphate (MEP) pathway for isoprenoid precursor biosynthesis is distinct from the mevalonate (MVA) pathway used by the mammalian host, and this pathway is apparently essential in most Apicomplexa. In this review, we discuss the current field of research on production and metabolic fates of isoprenoids in apicomplexan parasites, including the acquisition of host isoprenoid precursors and downstream products. We describe recent work identifying the first MEP pathway regulator in apicomplexan parasites, and introduce several promising areas for ongoing research into this well-validated antiparasitic target.

KEYWORDS:

Apicomplexa; Plasmodium; fosmidomycin; isoprenoid; metabolism; methylerythritol phosphate (MEP) pathway

PMID:

25893156

[PubMed]

Is childhood cat ownership a risk factor for schizophrenia later in life?

Schizophr Res. 2015 Apr 17. pii: S0920-9964(15)00176-0. doi: 10.1016/j.schres.2015.03.036. [Epub ahead of print]

 

Fuller Torrey E¹, Simmons W², Yolken RH³.

 

Two previous studies suggested that childhood cat ownership is a possible risk factor for later developing schizophrenia or other serious mental illness. We therefore used an earlier, large NAMI questionnaire to try and replicate this finding. The results were the same, suggesting that cat ownership in childhood is significantly more common in families in which the child later becomes seriously mentally ill. If true, an explanatory mechanism may be Toxoplasma gondii. We urge our colleagues to try and replicate these findings to clarify whether childhood cat ownership is truly a risk factor for later schizophrenia.
Copyright © 2015 Elsevier B.V. All rights reserved.

KEYWORDS:

Bipolar disorder; Cat contact; Schizophrenia; Toxoplasma gondii; Toxoplasmosis

PMID:

25892720

[PubMed - as supplied by publisher]

Postdoc Position Available

POSTDOCTORAL POSITION

 

Indiana University School of Medicine

POSTDOCTORAL POSITION available to investigate host-pathogen interactions using the protozoan parasite Toxoplasma gondii as a model system. Related to the malaria parasite, Plasmodium, Toxoplasma causes life-threatening infection in immunocompromised patients and has been linked to altering the behavior of its host. We are investigating cellular changes that occur in both the parasite and its host that are critical to pathogenesis.

Position requires a Ph.D., expertise in molecular biology, neuroscience, or cell signaling, and excellent communication skills (speaking and writing English). Experience in microbiology/parasitology is a plus, but not required. Submit CV, project plan (half page), and contact information for three references to Dr. Bill Sullivan (wjsulliv@iu.edu). Applicants that fail to include a brief description of project ideas will not be considered.

Our lab is part of the Intracellular Pathogens Group at IU, which meets regularly to foster innovation and collaboration. Visit www.sullivanlab.com for more information.

Located in downtown Indianapolis, Indiana University School of Medicine (IUSM) is the second largest medical school in the US and boasts an outstanding intellectual atmosphere and core facilities. IUSM was nationally ranked in the Top 30 Best Places to Work for Postdocs. IUSM is an equal opportunity employer.

Adaptive immune-mediated host resistance to Toxoplasma gondii is governed by the NF-κB regulator Bcl-3 in dendritic cells

Eur J Immunol. 2015 Apr 17. doi: 10.1002/eji.201445045. [Epub ahead of print]

 

Tassi I¹, Claudio E, Wang H, Tang W, Ha HL, Saret S, Sher A, Jankovic D, Siebenlist U.

 

The atypical IκB family member Bcl-3 associates with p50/NF-κB1 or p52/NF-κB2 homodimers in nuclei, thereby either positively or negatively modulating transcription in a context-dependent manner. Previously we reported that Bcl-3 was critical for host resistance to Toxoplasma gondii. Bcl-3-deficient mice succumbed within 3-5 weeks after infection, correlating with an apparently impaired Th1-type adaptive immune response. However in which cell type(s) Bcl-3 functioned to assure resistance remained unknown. We now show that Bcl-3 expression in dendritic cells is required to generate a protective Th1-type immune response and confer resistance to T.gondii. Surprisingly, mice lacking Bcl-3 in dendritic cells were as susceptible as mice globally deficient for Bcl-3. Furthermore, early innate defenses were not compromised by the absence of Bcl-3, as initial production of IL-12 by dendritic cells and IFN-γ by NK cells were preserved. However, subsequent production of IFN-γ by CD4⁺ and CD8⁺ T cells was compromised when dendritic cells lacked Bcl-3, and these mice succumbed at a time when T cell-mediated IFN-γ production was essential for host resistance. These findings demonstrate that Bcl-3 is required in dendritic cells to prime protective T-cell-mediated immunity to T.gondii. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.

KEYWORDS:

Adaptive Immunity, Bcl-3; Dendritic Cells; IFN-γ; T cells; T.gondii

PMID:

25884683

[PubMed - as supplied by publisher]

 

Toxoplasma gondii exposure in patients suffering from mental and behavioral disorders due to psychoactive substance use

BMC Infect Dis. 2015 Apr 3;15(1):172. doi: 10.1186/s12879-015-0912-1.

 

Alvarado-Esquivel C¹, Carrillo-Oropeza D², Pacheco-Vega SJ³, Hernández-Tinoco J⁴, Salcedo-Jaquez M⁵, Sánchez-Anguiano LF⁶, Ortiz-Jurado MN⁷, Alarcón-Alvarado Y⁸, Liesenfeld O^9,10, Beristain-García I¹¹.

BACKGROUND:

Toxoplasma gondii infection has been associated with psychiatric diseases. However, there is no information about the link between this infection and patients with mental and behavioral disorders due to psychoactive substance use.

METHODS:

We performed a case-control study with 149 psychiatric patients suffering from mental and behavioral disorders due to psychoactive substance use and 149 age- and gender-matched control subjects of the general population. We searched for anti-T. gondii IgG and IgM antibodies in the sera of participants by means of commercially available enzyme-linked immunoassays. Seroprevalence association with socio-demographic, clinical and behavioral characteristics in psychiatric patients was also investigated.

RESULTS:

Anti-T. gondii IgG antibodies were present in 15 (10.1%) of 149 cases and in 14 (9.4%) of 149 controls (P = 1.0). Anti-T. gondii IgM antibodies were found in 11 (7.4%) of the 149 cases and in 16 (10.7%) of the 149 controls (P = 0.31). No association of T. gondii exposure with socio-demographic characteristics of patients was found. Multivariate analysis of clinical and behavioral characteristics of cases showed that T. gondii seropositivity was positively associated with consumption of opossum meat (OR = 10.78; 95% CI: 2.16-53.81; P = 0.003) and soil flooring at home (OR = 11.15; 95% CI: 1.58-78.92; P = 0.01), and negatively associated with suicidal ideation (OR = 0.17; 95% CI: 0.05-0.64; P = 0.008).

CONCLUSIONS:

Mental and behavioral disorders due to psychoactive substance use do not appear to represent an increased risk for T. gondii exposure. This is the first report of a positive association of T. gondii exposure with consumption of opossum meat. Further studies to elucidate the role of T. gondii infection in suicidal ideation and behavior are needed to develop optimal strategies for the prevention of infection with T. gondii.

PMID:

25886154

[PubMed - in process]

PMCID:

PMC4397680

Toxoplasma gondii infection modulate systemic allergic immune response in BALB/c mice

Exp Parasitol. 2015 Apr 14. pii: S0014-4894(15)00090-9. doi: 10.1016/j.exppara.2015.04.001. [Epub ahead of print]

 

Fenoy IM¹, Sanchez VR², Soto AS², Picchio MS², Martin V², Goldman A².

 

The increased prevalence of allergies in developed countries has been attributed to a reduced exposure to some microbes. In agreement with epidemiological studies, we previously showed that Toxoplasma gondii infection prevents allergic airway inflammation. The mechanisms would be related to the strong Th1 response induced by the parasite and to regulatory cell induction. Herein we further characterized whether T. gondii allergy modulation extents to a systemic level or if it is limited to the lung. Parasite infection before allergic sensitization resulted in a diminished Th2 cytokine response and, when sensitized during acute infection, an increased in TGF-β production was detected. Allergen specific T cell proliferation was also reduced. Sensitization during both acute and chronic phases of infection resulted in a decreased anaphylaxis reaction. Our results extend earlier work and show that, in addition to lung airway inflammation, T. gondii infection can suppress allergic responses at systemic level. These results open the possibility that this protozoan infection could modulate other allergic disorders such as atopic dermatitis or oral allergies. Understanding the mechanisms by which different microorganisms regulate inflammation may potentially lead to the development of strategies aimed to control atopic diseases.
Copyright © 2015. Published by Elsevier Inc.

KEYWORDS:

Allergy; Anaphylaxis; Immune-modulation; Infection; Toxoplasma gondii

PMID:

25888245

[PubMed - as supplied by publisher]

Inflammasomes in host response to protozoan parasites

Immunol Rev. 2015 May;265(1):156-171. doi: 10.1111/imr.12291.

 

Zamboni DS¹, Lima-Junior DS.

 

Inflammasomes are multimeric complexes of proteins that are assembled in the host cell cytoplasm in response to specific stress signals or contamination of the cytoplasm by microbial molecules. The canonical inflammasomes are composed of at least three main components: an inflammatory caspase (caspase-1, caspase-11), an adapter molecule (such as ASC), and a sensor protein (such as NLRP1, NLRP3, NLRP12, NAIP1, NAIP2, NAIP5, or AIM2). The sensor molecule determines the inflammasome specificity by detecting specific microbial products or cell stress signals. Upon activation, these molecular platforms facilitate restriction of microbial replication and trigger an inflammatory form of cell death called pyroptosis, thus accounting for the genesis of inflammatory processes. Inflammasome activation has been widely reported in response to pathogenic bacteria. However, recent reports have highlighted the important role of the inflammasomes in the host response to the pathogenesis of infections caused by intracellular protozoan parasites. Herein, we review the activation and specific roles of inflammasomes in recognition and host responses to intracellular protozoan parasites such as Trypanosoma cruzi, Toxoplasma gondii, Plasmodium spp., and Leishmania spp.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

KEYWORDS:

Leishmania; Plasmodium; Toxoplasma; Trypanosoma; caspase-1; inflammasomes

PMID:

25879291

[PubMed - as supplied by publisher]

The NLRP1 inflammasomes

Immunol Rev. 2015 May;265(1):22-34. doi: 10.1111/imr.12283.

 

Chavarría-Smith J¹, Vance RE.

 

Inflammasomes are cytosolic protein complexes that serve as platforms for the recruitment and activation of the pro-inflammatory CASPASE-1 protease. CASPASE-1 activation leads to processing and maturation of the cytokines interleukin-1β and interleukin-18 and a lytic form of cell death termed pyroptosis. Inflammasome assembly is initiated by cytosolic sensors in response to microbial infections. Many of these sensors, including NLRP1 (NLR family, pyrin domain containing 1), are described to form an inflammasome, but until recently, the mechanism of inflammasome activation and its physiological functions in host defense have remained unclear. In the last few years, important advances in our understanding of NLRP1 biology have been achieved. In this review, we discuss the activation of NLRP1 by various stimuli, including Bacillus anthracis lethal toxin, Toxoplasma gondii, muramyl dipeptide, and host intracellular ATP depletion. The role NLRP1 plays in pathogen recognition and resistance during infection is also discussed, as is the regulation of NLRP1 by host and viral proteins. We conclude by discussing the unexpected differences in the mechanism of NLRP1 inflammasome activation, as compared to the activation of other inflammasomes, such as the NAIP (NLR family, apoptosis inhibitory protein)/NLRC4 inflammasomes.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

KEYWORDS:

NLRP1; caspase-1; inflammasome; innate immunity; lethal toxin

PMID:

25879281

[PubMed - as supplied by publisher]

Beyond the association. Toxoplasma gondii in schizophrenia, bipolar disorder, and addiction: systematic review and meta-analysis

Acta Psychiatr Scand. 2015 Apr 15. doi: 10.1111/acps.12423. [Epub ahead of print]

 

Sutterland AL¹, Fond G, Kuin A, Koeter MW, Lutter R, van Gool T, Yolken R, Szoke A, Leboyer M, de Haan L.

OBJECTIVE:

To perform a meta-analysis on studies reporting prevalence of Toxoplasma gondii (T. gondii) infection in any psychiatric disorder compared with healthy controls. Our secondary objective was to analyze factors possibly moderating heterogeneity.

METHOD:

A systematic search was performed to identify studies into T. gondii infection for all major psychiatric disorders versus healthy controls. Methodological quality, publication bias, and possible moderators were assessed.

RESULTS:

A total of 2866 citations were retrieved and 50 studies finally included. Significant odds ratios (ORs) with IgG antibodies were found in schizophrenia (OR 1.81, P < 0.00001), bipolar disorder (OR 1.52, P = 0.02), obsessive-compulsive disorder (OR 3.4, P < 0.001), and addiction (OR 1.91, P < 0.00001), but not for major depression (OR 1.21, P = 0.28). Exploration of the association between T. gondii and schizophrenia yielded a significant effect of seropositivity before onset and serointensity, but not IgM antibodies or gender. The amplitude of the OR was influenced by region and general seroprevalence. Moderators together accounted for 56% of the observed variance in study effects. After controlling for publication bias, the adjusted OR (1.43) in schizophrenia remained significant.

CONCLUSION:

These findings suggest that T. gondii infection is associated with several psychiatric disorders and that in schizophrenia reactivation of latent T. gondii infection may occur.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

KEYWORDS:

Toxoplasma gondii ; bipolar disorder; meta-analysis; schizophrenia; substance abuse disorder

PMID:

25877655

[PubMed - as supplied by publisher]

Comprehensive Evaluation of Toxoplasma gondii VEG and Neospora caninum LIV Genomes with Tachyzoite Stage Transcriptome and Proteome Defines Novel Transcript Features

PLoS One. 2015 Apr 13;10(4):e0124473. doi: 10.1371/journal.pone.0124473.

 

Ramaprasad A¹, Mourier T², Naeem R¹, Malas TB¹, Moussa E¹, Panigrahi A³, Vermont SJ⁴, Otto TD⁵, Wastling J⁴, Pain A¹.

 

Toxoplasma gondii is an important protozoan parasite that infects all warm-blooded animals and causes opportunistic infections in immuno-compromised humans. Its closest relative, Neospora caninum, is an important veterinary pathogen that causes spontaneous abortion in livestock. Comparative genomics of these two closely related coccidians has been of particular interest to identify genes that contribute to varied host cell specificity and disease. Here, we describe a manual evaluation of these genomes based on strand-specific RNA sequencing and shotgun proteomics from the invasive tachyzoite stages of these two parasites. We have corrected predicted structures of over one third of the previously annotated gene models and have annotated untranslated regions (UTRs) in over half of the predicted protein-coding genes. We observe distinctly long UTRs in both the organisms, almost four times longer than other model eukaryotes. We have also identified a putative set of cis-natural antisense transcripts (cis-NATs) and long intergenic non-coding RNAs (lincRNAs). We have significantly improved the annotation quality in these genomes that would serve as a manually curated dataset for Toxoplasma and Neospora research communities.

PMID:

25875305

[PubMed - as supplied by publisher]

Genotype-associated Arginase 1 Expression in Rat Peritoneal Macrophages induced by Toxoplasma gondii

J Parasitol. 2015 Apr 14. [Epub ahead of print]

 

Zhang Q¹, Kong L, Zhang Y, Chen H, An R, Wang W, Xu X, Zhang A, Cai Y, Li M, Wen H, Luo Q, Shen J, He L.

 

Toxoplasma gondii induces polarization of mouse macrophages, including both classically activated macrophage (M1) and alternatively activated macrophage (M2) in a genotype-related manner. Here we presented a novel result that the Wh6 strain with type Chinese 1, which is predominantly prevalent in China, induced Arg1 expression in a STAT6 dependent manner in primary rat peritoneal macrophages, compared to the PRU stain with typeⅡ that elicited a high expression of Arg1 in a C/EBPβ dependent manner. Additional experiment revealed that dexamethasone inhibited Arg1 expression in rat macrophage in both contexts. Our data suggested that Arg1 expression, which is abundant in polarized M2 cells, is associated with strain/genotype difference in varying pathways.

PMID:

25872571

[PubMed - as supplied by publisher]

A serine-arginine-rich (SR) splicing factor modulates alternative splicing of over a thousand genes in Toxoplasma gondii

Nucleic Acids Res. 2015 Apr 13. pii: gkv311. [Epub ahead of print]

 

Yeoh LM¹, Goodman CD², Hall NE³, van Dooren GG⁴, McFadden GI², Ralph SA⁵.

 

Single genes are often subject to alternative splicing, which generates alternative mature mRNAs. This phenomenon is widespread in animals, and observed in over 90% of human genes. Recent data suggest it may also be common in Apicomplexa. These parasites have small genomes, and economy of DNA is evolutionarily favoured in this phylum. We investigated the mechanism of alternative splicing in Toxoplasma gondii, and have identified and localized TgSR3, a homologue of ASF/SF2 (alternative-splicing factor/splicing factor 2, a serine-arginine-rich, or SR protein) to a subnuclear compartment. In addition, we conditionally overexpressed this protein, which was deleterious to growth. qRT-PCR was used to confirm perturbation of splicing in a known alternatively-spliced gene. We performed high-throughput RNA-seq to determine the extent of splicing modulated by this protein. Current RNA-seq algorithms are poorly suited to compact parasite genomes, and hence we complemented existing tools by writing a new program, GeneGuillotine, that addresses this deficiency by segregating overlapping reads into distinct genes. In order to identify the extent of alternative splicing, we released another program, JunctionJuror, that detects changes in intron junctions. Using this program, we identified about 2000 genes that were constitutively alternatively spliced in T. gondii. Overexpressing the splice regulator TgSR3 perturbed alternative splicing in over 1000 genes.
© The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

PMID:

25870410

[PubMed - as supplied by publisher]

Postdoctoral positions available

We are currently looking for four postdoctoral scholars to work on three different NIH-funded projects investigating host-parasite interactions. We are studying the innate and adaptive immune response to Toxoplasma and, in turn, how Toxoplasma modulates the host cell. We are particularly interested in individual differences in host susceptibility to Toxoplasma and Toxoplasma strain differences in interacting with the host. The Vet School at UC Davis is ranked as the best in the country and our location in the Vet School will allow us to investigate Toxoplasma proteins that play a role in its sexual cycle in cats and to perform genetic crosses to identify the molecular basis for phenotypic strain differences. More information can be found on our website:  www.saeijlab.com

We are looking for team players that are excited about studying host-parasite interactions and have excellent communication skills. Previous experience with molecular biology, biochemistry, immunology, genetics or computational skills is a plus.

UC Davis is located in the town of Davis, which is ranked as one of the best towns to live in in the nation. Davis is close to San Francisco, Sacramento, the Napa/Sonoma wine country and the Lake Tahoe ski area. UC Davis offers excellent benefits and multiple opportunities for professional development for postdocs (see https://gradstudies.ucdavis.edu/postdoctoral).

Interested candidates can submit a current C.V. and names of three references to: Dr. Jeroen Saeij (jsaeij@mit.edu), Associate Professor of Biology.

A large scale proteogenomics study of apicomplexan pathogens - Toxoplasma gondii and Neospora caninum

Proteomics. 2015 Apr 13. doi: 10.1002/pmic.201400553. [Epub ahead of print]

Krishna R1, Xia D, Sanderson S, Shanmugasundram A, Vermont S, Bernal A, Daniel-Naguib G, Ghali F, Brunk B, Roos D, Wastling JM, Jones AR.

Author information

Abstract

Proteomics data can supplement genome annotation efforts, for example being used to confirm gene models or correct gene annotation errors. Here we present a large scale proteogenomics study of two important apicomplexan pathogens: Toxoplasma gondii and Neospora caninum. We queried proteomics data against a panel of official and alternate gene models generated directly from RNASeq data, using several newly generated and some previously published MS data sets for this meta-analysis. We identified a total of 201996 and 39953 peptide-spectrum matches (PSMs) for T. gondii and N. caninum respectively at a 1% peptide false discovery rate threshold. This equated to the identification of 30494 distinct peptide sequences and 2921 proteins (matches to official gene models) for T. gondii, and 8911 peptides / 1273 proteins for N. caninum following stringent protein-level thresholding. We have also identified 289 and 140 loci for T. gondii and N. caninum respectively which mapped to RNA-Seq derived gene models used in our analysis and apparently absent from the official annotation (release 10 from EuPathDB) of these species. We present several examples in our study where the RNA-Seq evidence can help in correction of the current gene model and can help in discovery of potential new genes. The findings of this study have been integrated into the EuPathDB. The data have been deposited to the ProteomeXchange with identifiers PXD000297and PXD000298. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

KEYWORDS: 

Gene annotation; MS/MS; N. caninum; OMSSA; Open-source; Proteogenomics; T. gondii; X!Tandem

PMID:

 

25867681

 

[PubMed - as supplied by publisher]

Forward Genetics Screens Using Macrophages to Identify Toxoplasma gondii Genes Important for Resistance to IFN-γ-Dependent Cell Autonomous Immunity

J Vis Exp. 2015 Mar 12;(97). doi: 10.3791/52556.

Walwyn O1, Skariah S1, Lynch B1, Kim N1, Ueda Y1, Vohora N1, Choe J1, Mordue DG2.

Author information

Abstract

Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan pathogen. The parasite invades and replicates within virtually any warm blooded vertebrate cell type. During parasite invasion of a host cell, the parasite creates a parasitophorous vacuole (PV) that originates from the host cell membrane independent of phagocytosis within which the parasite replicates. While IFN-dependent-innate and cell mediated immunity is important for eventual control of infection, innate immune cells, including neutrophils, monocytes and dendritic cells, can also serve as vehicles for systemic dissemination of the parasite early in infection. An approach is described that utilizes the host innate immune response, in this case macrophages, in a forward genetic screen to identify parasite mutants with a fitness defect in infected macrophages following activation but normal invasion and replication in naïve macrophages. Thus, the screen isolates parasite mutants that have a specific defect in their ability to resist the effects of macrophage activation. The paper describes two broad phenotypes of mutant parasites following activation of infected macrophages: parasite stasis versus parasite degradation, often in amorphous vacuoles. The parasite mutants are then analyzed to identify the responsible parasite genes specifically important for resistance to induced mediators of cell autonomous immunity. The paper presents a general approach for the forward genetics screen that, in theory, can be modified to target parasite genes important for resistance to specific antimicrobial mediators. It also describes an approach to evaluate the specific macrophage antimicrobial mediators to which the parasite mutant is susceptible. Activation of infected macrophages can also promote parasite differentiation from the tachyzoite to bradyzoite stage that maintains chronic infection. Therefore, methodology is presented to evaluate the importance of the identified parasite gene to establishment of chronic infection. 

PMID:

 

25867017

 

[PubMed - in process]

Anti-Toxoplasma Activity of Natural Products: A Review

Recent Pat Antiinfect Drug Discov. 2015 Apr 10. [Epub ahead of print]

Sepúlveda-Arias JC1, Veloza LA, Mantilla-Muriel LE.

Author information

Abstract

Toxoplasma gondii is an intracellular parasite widely distributed in nature. Infection is asymptomatic in immunocompetent individuals; however, various clinical manifestations may occur in immunocompromised individuals. Although there are medications for the treatment of toxoplasmosis, such as pyrimethamine and sulfonamide, they cannot always be used due to adverse reactions or to therapeutic failures related to intolerance or malabsorption of drugs and to parasite drug resistance. In recent years, the search for new antimicrobial agents derived from plants has intensified because a quarter of synthetic drugs that are currently prescribed have been isolated from a plant source, demonstrating that natural products are important in the development of new drugs. A systematic literature search was conducted to evaluate the use of natural products as an alternative for the treatment of T. gondii infection. The search was conducted for the 2000-2014 period in Science Direct, Scopus, PubMed, EMBASE, and SciELO databases, using the following MeSH terms: anti-Toxoplasma activity, toxoplasma AND natural products, toxoplasma AND plant extracts. Ethnobotanical and experimental evidence (in vitro/in vivo) was found supporting the use of natural products as a source for the discovery of new therapies against T. gondii.

PMID:

 

25858302

 

[PubMed - as supplied by publisher]

Chronic Toxoplasma gondii in Nurr1-Null Heterozygous Mice Exacerbates Elevated Open Field Activity

PLoS One. 2015 Apr 9;10(4):e0119280. doi: 10.1371/journal.pone.0119280. eCollection 2015.

Eells JB1, Varela-Stokes A1, Guo-Ross SX1, Kummari E1, Smith HM1, Cox E1, Lindsay DS2.

Author information

Abstract

Latent infection with Toxoplasma gondii is common in humans (approximately 30% of the global population) and is a significant risk factor for schizophrenia. Since prevalence of T. gondii infection is far greater than prevalence of schizophrenia (0.5-1%), genetic risk factors are likely also necessary to contribute to schizophrenia. To test this concept in an animal model, Nurr1-null heterozygous (+/-) mice and wild-type (+/+) mice were evaluate using an emergence test, activity in an open field and with a novel object, response to bobcat urine and prepulse inhibition of the acoustic startle response (PPI) prior to and 6 weeks after infection with T. gondii. In the emergence test, T. gondii infection significantly decreased the amount of time spent in the cylinder. Toxoplasma gondii infection significantly elevated open field activity in both +/+ and +/- mice but this increase was significantly exacerbated in +/- mice. T. gondii infection reduced PPI in male +/- mice but this was not statistically significant. Aversion to bobcat urine was abolished by T. gondii infection in +/+ mice. In female +/- mice, aversion to bobcat urine remained after T. gondii infection while the male +/- mice showed no aversion to bobcat urine. Antibody titers of infected mice were a critical variable associated with changes in open field activity, such that an inverted U shaped relationship existed between antibody titers and the percent change in open field activity with a significant increase in activity at low and medium antibody titers but no effect at high antibody titers. These data demonstrate that the Nurr1 +/- genotype predisposes mice to T. gondii-induced alterations in behaviors that involve dopamine neurotransmission and are associated with symptoms of schizophrenia. We propose that these alterations in murine behavior were due to further exacerbation of the altered dopamine neurotransmission in Nurr1 +/- mice. 

PMID:

 

25855987

 

[PubMed - in process] 

α2u-globulins mediate manipulation of host attractiveness in Toxoplasma gondii-Rattus novergicus association

ISME J. 2015 Mar 13. doi: 10.1038/ismej.2015.33. [Epub ahead of print]
 

Vasudevan A¹, Kumar V¹, Ning Chiang Y², Yew JY³, Cheemadan S¹, Vyas A¹.

 

Uninfected female rats (Rattus novergicus) exhibit greater attraction to the males infected with protozoan parasite Toxoplasma gondii. This phenomenon is contrary to the aversion towards infected males observed in multitude of other host-parasite associations. In this report, we describe a proximate mechanism for this anomaly. We demonstrate that T. gondii infection enhances hepatic production and urinary excretion of α2u-globulins in rats. We further demonstrate that α2u-globulins are sufficient to recapitulate male sexual attractiveness akin to effects of the infection. This manipulation possibly results in greater horizontal transmission of this parasite between the infected male and the uninfected female. It supports the notion that in some evolutionary niches parasites can alter host sexual signaling, likely leading to an increased rate of sexual transmission.

PMID:

25853804

[PubMed - as supplied by publisher]

AMA1-deficient Toxoplasma parasites transiently colonize mice and trigger an innate immune response that proceeds to long lasting protective immunity

Infect Immun. 2015 Apr 6. pii: IAI.02606-14. [Epub ahead of print]

 

Lagal V¹, Dinis M¹, Cannella D², Bargieri D³, Gonzalez V¹, Andenmatten N⁴, Meissner M⁴, Tardieux I⁵.

 

The Apical Membrane Antigen 1 (AMA1) protein was believed to be essential for the perpetuation of two Apicomplexa parasite genera Plasmodium and Toxoplasma, until we genetically engineered viable parasites lacking AMA1. The reduction in invasiveness of the T. gondii RH-AMA1^KO tachyzoite population, in vitro, raised key questions about the outcome of these tachyzoites once inoculated in the peritoneal cavity of mice. In this study, we used the AMNIS technology to simultaneously quantify and image the parasitic process driven by AMA1^KO tachyzoites. We report their ability to colonize and multiply in mesothelial cells and in both resident and recruited leucocytes. While the RH-AMA1^KO population amplification is rapidly lethal in immunocompromised mice, it is controlled in immunocompetent hosts where a combination of immune cells sense parasites and secrete pro-inflammatory cytokines. This innate response further leads to a long-lasting immunoprotective status against a secondary challenge by high inocula of the homologous type I or a distinct type II T. gondii genotypes. While AMA1 is definitively not an essential protein for tachyzoite entry and multiplication in host cells, it clearly assists the expansion of parasite population in vivo.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.

PMID:

25847964

[PubMed - as supplied by publisher]