PLoS One. 2010 Dec 31;5(12):e14472.
The CD40-Autophagy Pathway Is Needed for Host Protection Despite IFN-Γ-Dependent Immunity and CD40 Induces Autophagy via Control of P21 Levels
Portillo JA, Okenka G, Reed E, Subauste A, Van Grol J, Gentil K, Komatsu M, Tanaka K, Landreth G, Levine B, Subauste CS.
Department of Ophthalmology and Visual Sciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America.
Abstract
Autophagy degrades pathogens in vitro. The autophagy gene Atg5 has been reported to be required for IFN-γ-dependent host protection in vivo. However, these protective effects occur independently of autophagosome formation. Thus, the in vivo role of classic autophagy in protection conferred by adaptive immunity and how adaptive immunity triggers autophagy are incompletely understood. Employing biochemical, genetic and morphological studies, we found that CD40 upregulates the autophagy molecule Beclin 1 in microglia and triggers killing of Toxoplasma gondii dependent on the autophagy machinery. Infected CD40(-/-) mice failed to upregulate Beclin 1 in microglia/macrophages in vivo. Autophagy-deficient Beclin 1(+/-) mice, mice with deficiency of the autophagy protein Atg7 targeted to microglia/macrophages as well as CD40(-/-) mice exhibited impaired killing of T. gondii and were susceptible to cerebral and ocular toxoplasmosis. Susceptibility to toxoplasmosis occurred despite upregulation of IFN-γ, TNF-α and NOS2, preservation of IFN-γ-induced microglia/macrophage anti-T. gondii activity and the generation of anti-T. gondii T cell immunity. CD40 upregulated Beclin 1 and triggered killing of T. gondii by decreasing protein levels of p21, a molecule that degrades Beclin 1. These studies identified CD40-p21-Beclin 1 as a pathway by which adaptive immunity stimulates autophagy. In addition, they support that autophagy is a mechanism through which CD40-dependent immunity mediates in vivo protection and that the CD40-autophagic machinery is needed for host resistance despite IFN-γ.
PMID: 21217818 [PubMed - in process]
Wednesday, January 12, 2011
Determination of the Viability of Toxoplasma gondii in Cured Ham Using Bioassay
J Food Prot. 2010 Dec;73(12):2239-43.
Determination of the Viability of Toxoplasma gondii in Cured Ham Using Bioassay: Influence of Technological Processing and Food Safety Implications
Bayarri S, Gracia MJ, Lázaro R, Pe Rez-Arquillué C, Barberán M, Herrera A.
Departamento de Producción Animal y Ciencia de los Alimentos;, Email: sbayarri@unizar.es.
Abstract
Toxoplasmosis is a zoonotic disease caused by the protozoan Toxoplasma gondii and distributed worldwide. Ingestion of viable cysts from infected raw or undercooked meat is an important route of horizontal transmission of the parasite to humans. Little information is available concerning the effect of commercial curing on cysts of T. gondii. This study is the first in which the influence of processing of cured ham on the viability of T. gondii has been evaluated, using bioassay to assess the risk of infection from eating this meat product. Naturally infected pigs were selected for the study, and a mouse concentration bioassay technique was used to demonstrate viable bradyzoites of T. gondii in porcine tissues and hams. No viable parasites were found in the final product (14 months of curing) based on results of the indirect immunofluorescence assay and histological and PCR analyses. Our results indicate that the consumption of hams cured as described here poses an insignificant risk of acquiring toxoplasmosis. However, additional studies are required to evaluate the safety of ham products cured under different conditions of curing time, salt, and nitrite concentration.
PMID: 21219742 [PubMed - in process]
Determination of the Viability of Toxoplasma gondii in Cured Ham Using Bioassay: Influence of Technological Processing and Food Safety Implications
Bayarri S, Gracia MJ, Lázaro R, Pe Rez-Arquillué C, Barberán M, Herrera A.
Departamento de Producción Animal y Ciencia de los Alimentos;, Email: sbayarri@unizar.es.
Abstract
Toxoplasmosis is a zoonotic disease caused by the protozoan Toxoplasma gondii and distributed worldwide. Ingestion of viable cysts from infected raw or undercooked meat is an important route of horizontal transmission of the parasite to humans. Little information is available concerning the effect of commercial curing on cysts of T. gondii. This study is the first in which the influence of processing of cured ham on the viability of T. gondii has been evaluated, using bioassay to assess the risk of infection from eating this meat product. Naturally infected pigs were selected for the study, and a mouse concentration bioassay technique was used to demonstrate viable bradyzoites of T. gondii in porcine tissues and hams. No viable parasites were found in the final product (14 months of curing) based on results of the indirect immunofluorescence assay and histological and PCR analyses. Our results indicate that the consumption of hams cured as described here poses an insignificant risk of acquiring toxoplasmosis. However, additional studies are required to evaluate the safety of ham products cured under different conditions of curing time, salt, and nitrite concentration.
PMID: 21219742 [PubMed - in process]
Friday, January 07, 2011
Genomic Data Reveal Toxoplasma gondii Differentiation Mutants Are Also Impaired with Respect to Switching into a Novel Extracellular Tachyzoite State
PLoS One. 2010 Dec 30;5(12):e14463.
Genomic Data Reveal Toxoplasma gondii Differentiation Mutants Are Also Impaired with Respect to Switching into a Novel Extracellular Tachyzoite State
Lescault PJ, Thompson AB, Patil V, Lirussi D, Burton A, Margarit J, Bond J, Matrajt M.
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
Abstract
Toxoplasma gondii pathogenesis includes the invasion of host cells by extracellular parasites, replication of intracellular tachyzoites, and differentiation to a latent bradyzoite stage. We present the analysis of seven novel T. gondii insertional mutants that do not undergo normal differentiation to bradyzoites. Microarray quantification of the variation in genome-wide RNA levels for each parasite line and times after induction allowed us to describe states in the normal differentiation process, to analyze mutant lines in the context of these states, and to identify genes that may have roles in initiating the transition from tachyzoite to bradyzoite. Gene expression patterns in wild-type parasites undergoing differentiation suggest a novel extracellular state within the tachyzoite stage. All mutant lines exhibit aberrant regulation of bradyzoite gene expression and notably some of the mutant lines appear to exhibit high proportions of the intracellular tachyzoite state regardless of whether they are intracellular or extracellular. In addition to the genes identified by the insertional mutagenesis screen, mixture model analysis allowed us to identify a small number of genes, in mutants, for which expression patterns could not be accounted for using the three parasite states - genes that may play a mechanistic role in switching from the tachyzoite to bradyzoite stage.
PMID: 21209930 [PubMed - in process]
Genomic Data Reveal Toxoplasma gondii Differentiation Mutants Are Also Impaired with Respect to Switching into a Novel Extracellular Tachyzoite State
Lescault PJ, Thompson AB, Patil V, Lirussi D, Burton A, Margarit J, Bond J, Matrajt M.
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
Abstract
Toxoplasma gondii pathogenesis includes the invasion of host cells by extracellular parasites, replication of intracellular tachyzoites, and differentiation to a latent bradyzoite stage. We present the analysis of seven novel T. gondii insertional mutants that do not undergo normal differentiation to bradyzoites. Microarray quantification of the variation in genome-wide RNA levels for each parasite line and times after induction allowed us to describe states in the normal differentiation process, to analyze mutant lines in the context of these states, and to identify genes that may have roles in initiating the transition from tachyzoite to bradyzoite. Gene expression patterns in wild-type parasites undergoing differentiation suggest a novel extracellular state within the tachyzoite stage. All mutant lines exhibit aberrant regulation of bradyzoite gene expression and notably some of the mutant lines appear to exhibit high proportions of the intracellular tachyzoite state regardless of whether they are intracellular or extracellular. In addition to the genes identified by the insertional mutagenesis screen, mixture model analysis allowed us to identify a small number of genes, in mutants, for which expression patterns could not be accounted for using the three parasite states - genes that may play a mechanistic role in switching from the tachyzoite to bradyzoite stage.
PMID: 21209930 [PubMed - in process]
Thursday, January 06, 2011
Translation control is critical during acute and chronic stages of toxoplasmosis infection
Expert Rev Anti Infect Ther. 2011 Jan;9(1):1-3.
Translation control is critical during acute and chronic stages of toxoplasmosis infection
Joyce BR, Konrad C, Wek RC, Sullivan WJ Jr.
PMID: 21171869 [PubMed - in process]
Translation control is critical during acute and chronic stages of toxoplasmosis infection
Joyce BR, Konrad C, Wek RC, Sullivan WJ Jr.
PMID: 21171869 [PubMed - in process]
Intramembrane Cleavage of AMA1 Triggers Toxoplasma to Switch from an Invasive to a Replicative Mode
Science. 2010 Dec 23. [Epub ahead of print]
Intramembrane Cleavage of AMA1 Triggers Toxoplasma to Switch from an Invasive to a Replicative Mode
Santos JM, Ferguson DJ, Blackman MJ, Soldati-Favre D.
Department of Microbiology, Faculty of Medicine, University of Geneva, 1 rue-Michel Servet, 1211 Geneva 4, Switzerland.
Abstract
Apicomplexan parasites invade host cells and immediately initiate cell division. The extracellular parasite discharges transmembrane proteins onto its surface to mediate motility and invasion. These are shed by intramembrane cleavage, a process associated with invasion but otherwise poorly understood. Functional analysis of Toxoplasma rhomboid 4, a surface intramembrane protease, by conditional overexpression of a catalytically inactive form, produced a profound block in replication. This was completely rescued by expression of the cleaved cytoplasmic tail of Toxoplasma or Plasmodium apical membrane antigen 1 (AMA1). These results reveal an unexpected function for AMA1 in parasite replication, and suggest that invasion proteins help to promote parasite switch from an invasive to a replicative mode.
PMID: 21205639 [PubMed - as supplied by publisher]
Intramembrane Cleavage of AMA1 Triggers Toxoplasma to Switch from an Invasive to a Replicative Mode
Santos JM, Ferguson DJ, Blackman MJ, Soldati-Favre D.
Department of Microbiology, Faculty of Medicine, University of Geneva, 1 rue-Michel Servet, 1211 Geneva 4, Switzerland.
Abstract
Apicomplexan parasites invade host cells and immediately initiate cell division. The extracellular parasite discharges transmembrane proteins onto its surface to mediate motility and invasion. These are shed by intramembrane cleavage, a process associated with invasion but otherwise poorly understood. Functional analysis of Toxoplasma rhomboid 4, a surface intramembrane protease, by conditional overexpression of a catalytically inactive form, produced a profound block in replication. This was completely rescued by expression of the cleaved cytoplasmic tail of Toxoplasma or Plasmodium apical membrane antigen 1 (AMA1). These results reveal an unexpected function for AMA1 in parasite replication, and suggest that invasion proteins help to promote parasite switch from an invasive to a replicative mode.
PMID: 21205639 [PubMed - as supplied by publisher]
Full-parasites: database of full-length cDNAs of apicomplexa parasites, 2010 update
Nucleic Acids Res. 2011 Jan;39(Database issue):D625-31. Epub 2010 Nov 4.
Full-parasites: database of full-length cDNAs of apicomplexa parasites, 2010 update
Tuda J, Mongan AE, Tolba ME, Imada M, Yamagishi J, Xuan X, Wakaguri H, Sugano S, Sugimoto C, Suzuki Y.
Faculty of Medicine, Sam Ratulangi University, Kampus Unsrat, Bahu Manado 95115, Indonesia.
Abstract
Full-Parasites (http://fullmal.hgc.jp/) is a transcriptome database of apicomplexa parasites, which include Plasmodium and Toxoplasma species. The latest version of Full-Parasites contains a total of 105,786 EST sequences from 12 parasites, of which 5925 full-length cDNAs have been completely sequenced. Full-Parasites also contain more than 30 million transcription start sites (TSS) for Plasmodium falciparum (Pf) and Toxoplasma gondii (Tg), which were identified using our novel oligo-capping-based protocol. Various types of cDNA data resources were interconnected with our original database functionalities. Specifically, in this update, we have included two unique RNA-Seq data sets consisting of 730 million mapped RNA-Seq tags. One is a dataset of 16 time-lapse experiments of cultured bradyzoite differentiation for Tg. The other dataset includes 31 clinical samples of Pf. Parasite RNA was extracted together with host human RNA, and the extracted mixed RNA was used for RNA sequencing, with the expectation that gene expression information from the host and parasite would be simultaneously represented. By providing the largest unique full-length cDNA and dynamic transcriptome data, Full-Parasites is useful for understanding host-parasite interactions and will help to eventually elucidate how monophyletic organisms have evolved to become parasites by adopting complex life cycles.
PMID: 21051343 [PubMed - in process]
Full-parasites: database of full-length cDNAs of apicomplexa parasites, 2010 update
Tuda J, Mongan AE, Tolba ME, Imada M, Yamagishi J, Xuan X, Wakaguri H, Sugano S, Sugimoto C, Suzuki Y.
Faculty of Medicine, Sam Ratulangi University, Kampus Unsrat, Bahu Manado 95115, Indonesia.
Abstract
Full-Parasites (http://fullmal.hgc.jp/) is a transcriptome database of apicomplexa parasites, which include Plasmodium and Toxoplasma species. The latest version of Full-Parasites contains a total of 105,786 EST sequences from 12 parasites, of which 5925 full-length cDNAs have been completely sequenced. Full-Parasites also contain more than 30 million transcription start sites (TSS) for Plasmodium falciparum (Pf) and Toxoplasma gondii (Tg), which were identified using our novel oligo-capping-based protocol. Various types of cDNA data resources were interconnected with our original database functionalities. Specifically, in this update, we have included two unique RNA-Seq data sets consisting of 730 million mapped RNA-Seq tags. One is a dataset of 16 time-lapse experiments of cultured bradyzoite differentiation for Tg. The other dataset includes 31 clinical samples of Pf. Parasite RNA was extracted together with host human RNA, and the extracted mixed RNA was used for RNA sequencing, with the expectation that gene expression information from the host and parasite would be simultaneously represented. By providing the largest unique full-length cDNA and dynamic transcriptome data, Full-Parasites is useful for understanding host-parasite interactions and will help to eventually elucidate how monophyletic organisms have evolved to become parasites by adopting complex life cycles.
PMID: 21051343 [PubMed - in process]
Wednesday, January 05, 2011
Strain-specific activation of the NF-{kappa}B pathway by GRA15, a novel Toxoplasma gondii dense granule protein
J Exp Med. 2011 Jan 3. [Epub ahead of print]
Strain-specific activation of the NF-{kappa}B pathway by GRA15, a novel Toxoplasma gondii dense granule protein
Rosowski EE, Lu D, Julien L, Rodda L, Gaiser RA, Jensen KD, Saeij JP.
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139.
Abstract
NF-κB is an integral component of the immune response to Toxoplasma gondii. Although evidence exists that T. gondii can directly modulate the NF-κB pathway, the parasite-derived effectors involved are unknown. We determined that type II strains of T. gondii activate more NF-κB than type I or type III strains, and using forward genetics we found that this difference is a result of the polymorphic protein GRA15, a novel dense granule protein which T. gondii secretes into the host cell upon invasion. A GRA15-deficient type II strain has a severe defect in both NF-κB nuclear translocation and NF-κB-mediated transcription. Furthermore, human cells expressing type II GRA15 also activate NF-κB, demonstrating that GRA15 alone is sufficient for NF-κB activation. Along with the rhoptry protein ROP16, GRA15 is responsible for a large part of the strain differences in the induction of IL-12 secretion by infected mouse macrophages. In vivo bioluminescent imaging showed that a GRA15-deficient type II strain grows faster compared with wild-type, most likely through its reduced induction of IFN-γ. These results show for the first time that a dense granule protein can modulate host signaling pathways, and dense granule proteins can therefore join rhoptry proteins in T. gondii's host cell-modifying arsenal.
PMID: 21199955 [PubMed - as supplied by publisher]
Strain-specific activation of the NF-{kappa}B pathway by GRA15, a novel Toxoplasma gondii dense granule protein
Rosowski EE, Lu D, Julien L, Rodda L, Gaiser RA, Jensen KD, Saeij JP.
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139.
Abstract
NF-κB is an integral component of the immune response to Toxoplasma gondii. Although evidence exists that T. gondii can directly modulate the NF-κB pathway, the parasite-derived effectors involved are unknown. We determined that type II strains of T. gondii activate more NF-κB than type I or type III strains, and using forward genetics we found that this difference is a result of the polymorphic protein GRA15, a novel dense granule protein which T. gondii secretes into the host cell upon invasion. A GRA15-deficient type II strain has a severe defect in both NF-κB nuclear translocation and NF-κB-mediated transcription. Furthermore, human cells expressing type II GRA15 also activate NF-κB, demonstrating that GRA15 alone is sufficient for NF-κB activation. Along with the rhoptry protein ROP16, GRA15 is responsible for a large part of the strain differences in the induction of IL-12 secretion by infected mouse macrophages. In vivo bioluminescent imaging showed that a GRA15-deficient type II strain grows faster compared with wild-type, most likely through its reduced induction of IFN-γ. These results show for the first time that a dense granule protein can modulate host signaling pathways, and dense granule proteins can therefore join rhoptry proteins in T. gondii's host cell-modifying arsenal.
PMID: 21199955 [PubMed - as supplied by publisher]
Phosphorylation of Mouse Immunity-Related GTPase (IRG) Resistance Proteins Is an Evasion Strategy for Virulent Toxoplasma gondii
PLoS Biol. 2010 Dec 21;8(12):e1000576.
Phosphorylation of Mouse Immunity-Related GTPase (IRG) Resistance Proteins Is an Evasion Strategy for Virulent Toxoplasma gondii
Steinfeldt T, Könen-Waisman S, Tong L, Pawlowski N, Lamkemeyer T, Sibley LD, Hunn JP, Howard JC.
Institute for Genetics, University of Cologne, Cologne, Germany.
Abstract
Virulence of complex pathogens in mammals is generally determined by multiple components of the pathogen interacting with the functional complexity and multiple layering of the mammalian immune system. It is most unusual for the resistance of a mammalian host to be overcome by the defeat of a single defence mechanism. In this study we uncover and analyse just such a case at the molecular level, involving the widespread intracellular protozoan pathogen Toxoplasma gondii and one of its most important natural hosts, the house mouse (Mus musculus). Natural polymorphism in virulence of Eurasian T. gondii strains for mice has been correlated in genetic screens with the expression of polymorphic rhoptry kinases (ROP kinases) secreted into the host cell during infection. We show that the molecular targets of the virulent allelic form of ROP18 kinase are members of a family of cellular GTPases, the interferon-inducible IRG (immunity-related GTPase) proteins, known from earlier work to be essential resistance factors in mice against avirulent strains of T. gondii. Virulent T. gondii strain ROP18 kinase phosphorylates several mouse IRG proteins. We show that the parasite kinase phosphorylates host Irga6 at two threonines in the nucleotide-binding domain, biochemically inactivating the GTPase and inhibiting its accumulation and action at the T. gondii parasitophorous vacuole membrane. Our analysis identifies the conformationally active switch I region of the GTP-binding site as an Achilles' heel of the IRG protein pathogen-resistance mechanism. The polymorphism of ROP18 in natural T. gondii populations indicates the existence of a dynamic, rapidly evolving ecological relationship between parasite virulence factors and host resistance factors. This system should be unusually fruitful for analysis at both ecological and molecular levels since both T. gondii and the mouse are widespread and abundant in the wild and are well-established model species with excellent analytical tools available.
PMID: 21203588 [PubMed - in process]
Phosphorylation of Mouse Immunity-Related GTPase (IRG) Resistance Proteins Is an Evasion Strategy for Virulent Toxoplasma gondii
Steinfeldt T, Könen-Waisman S, Tong L, Pawlowski N, Lamkemeyer T, Sibley LD, Hunn JP, Howard JC.
Institute for Genetics, University of Cologne, Cologne, Germany.
Abstract
Virulence of complex pathogens in mammals is generally determined by multiple components of the pathogen interacting with the functional complexity and multiple layering of the mammalian immune system. It is most unusual for the resistance of a mammalian host to be overcome by the defeat of a single defence mechanism. In this study we uncover and analyse just such a case at the molecular level, involving the widespread intracellular protozoan pathogen Toxoplasma gondii and one of its most important natural hosts, the house mouse (Mus musculus). Natural polymorphism in virulence of Eurasian T. gondii strains for mice has been correlated in genetic screens with the expression of polymorphic rhoptry kinases (ROP kinases) secreted into the host cell during infection. We show that the molecular targets of the virulent allelic form of ROP18 kinase are members of a family of cellular GTPases, the interferon-inducible IRG (immunity-related GTPase) proteins, known from earlier work to be essential resistance factors in mice against avirulent strains of T. gondii. Virulent T. gondii strain ROP18 kinase phosphorylates several mouse IRG proteins. We show that the parasite kinase phosphorylates host Irga6 at two threonines in the nucleotide-binding domain, biochemically inactivating the GTPase and inhibiting its accumulation and action at the T. gondii parasitophorous vacuole membrane. Our analysis identifies the conformationally active switch I region of the GTP-binding site as an Achilles' heel of the IRG protein pathogen-resistance mechanism. The polymorphism of ROP18 in natural T. gondii populations indicates the existence of a dynamic, rapidly evolving ecological relationship between parasite virulence factors and host resistance factors. This system should be unusually fruitful for analysis at both ecological and molecular levels since both T. gondii and the mouse are widespread and abundant in the wild and are well-established model species with excellent analytical tools available.
PMID: 21203588 [PubMed - in process]
TgVTC2 is Involved in Polyphosphate Accumulation in Toxoplasma gondii
Mol Biochem Parasitol. 2010 Dec 29. [Epub ahead of print]
TgVTC2 is Involved in Polyphosphate Accumulation in Toxoplasma gondii
Rooney PJ, Ayong L, Tobin CM, Moreno SN, Knoll LJ.
Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Microbial Sciences Building Room 3345, 1550 Linden Drive, Madison, WI 53706, United States.
Abstract
Polyphosphate is found in every cell, having roles in diverse processes, including differentiation and response to stress. In this study, we characterize a Toxoplasma gondii mutant containing an insertion within the carboxy-terminal end of a homolog of Saccharomyces cerevisiae Vtc2p, a component of the polyphosphate synthetic machinery. Locus TgVTC2 encodes a 140kDa protein containing conserved SPX, VTC and transmembrane domains. TgVTC2 localizes in punctate spots within the cytoplasm that do not co-localize with known markers. The TgVTC2 mutant showed dramatically reduced polyphosphate accumulation, a defect restored by introduction of TgVTC2 to the mutant. Insertion within TgVTC2 resulted in increased transcript levels for two loci, including a putative FIKK kinase. These transcript levels were restored to wild-type levels upon complementation with the TgVTC2 locus. The TgVTC2 locus was refractory to knockout, and may be essential. Analysis of this TgVTC2 mutant will facilitate dissection of the T. gondii polyphosphate synthesis pathway.
Copyright © 2010. Published by Elsevier B.V.
PMID: 21195114 [PubMed - as supplied by publisher]
TgVTC2 is Involved in Polyphosphate Accumulation in Toxoplasma gondii
Rooney PJ, Ayong L, Tobin CM, Moreno SN, Knoll LJ.
Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Microbial Sciences Building Room 3345, 1550 Linden Drive, Madison, WI 53706, United States.
Abstract
Polyphosphate is found in every cell, having roles in diverse processes, including differentiation and response to stress. In this study, we characterize a Toxoplasma gondii mutant containing an insertion within the carboxy-terminal end of a homolog of Saccharomyces cerevisiae Vtc2p, a component of the polyphosphate synthetic machinery. Locus TgVTC2 encodes a 140kDa protein containing conserved SPX, VTC and transmembrane domains. TgVTC2 localizes in punctate spots within the cytoplasm that do not co-localize with known markers. The TgVTC2 mutant showed dramatically reduced polyphosphate accumulation, a defect restored by introduction of TgVTC2 to the mutant. Insertion within TgVTC2 resulted in increased transcript levels for two loci, including a putative FIKK kinase. These transcript levels were restored to wild-type levels upon complementation with the TgVTC2 locus. The TgVTC2 locus was refractory to knockout, and may be essential. Analysis of this TgVTC2 mutant will facilitate dissection of the T. gondii polyphosphate synthesis pathway.
Copyright © 2010. Published by Elsevier B.V.
PMID: 21195114 [PubMed - as supplied by publisher]
Foodborne illness acquired in the United States-major pathogens
Emerg Infect Dis. 2011 Jan;17(1):7-15.
Foodborne illness acquired in the United States-major pathogens
Scallan E, Hoekstra RM, Angulo FJ, Tauxe RV, Widdowson MA, Roy SL, Jones JL, Griffin PM.
Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Abstract
Estimates of foodborne illness can be used to direct food safety policy and interventions. We used data from active and passive surveillance and other sources to estimate that each year 31 major pathogens acquired in the United States caused 9.4 million episodes of foodborne illness (90% credible interval [CrI] 6.6-12.7 million), 55,961 hospitalizations (90% CrI 39,534-75,741), and 1,351 deaths (90% CrI 712-2,268). Most (58%) illnesses were caused by norovirus, followed by nontyphoidal Salmonella spp. (11%), Clostridium perfringens (10%), and Campylobacter spp. (9%). Leading causes of hospitalization were nontyphoidal Salmonella spp. (35%), norovirus (26%), Campylobacter spp. (15%), and Toxoplasma gondii (8%). Leading causes of death were nontyphoidal Salmonella spp. (28%), T. gondii (24%), Listeria monocytogenes (19%), and norovirus (11%). These estimates cannot be compared with prior (1999) estimates to assess trends because different methods were used. Additional data and more refined methods can improve future estimates.
PMID: 21192848 [PubMed - in process]
Foodborne illness acquired in the United States-major pathogens
Scallan E, Hoekstra RM, Angulo FJ, Tauxe RV, Widdowson MA, Roy SL, Jones JL, Griffin PM.
Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Abstract
Estimates of foodborne illness can be used to direct food safety policy and interventions. We used data from active and passive surveillance and other sources to estimate that each year 31 major pathogens acquired in the United States caused 9.4 million episodes of foodborne illness (90% credible interval [CrI] 6.6-12.7 million), 55,961 hospitalizations (90% CrI 39,534-75,741), and 1,351 deaths (90% CrI 712-2,268). Most (58%) illnesses were caused by norovirus, followed by nontyphoidal Salmonella spp. (11%), Clostridium perfringens (10%), and Campylobacter spp. (9%). Leading causes of hospitalization were nontyphoidal Salmonella spp. (35%), norovirus (26%), Campylobacter spp. (15%), and Toxoplasma gondii (8%). Leading causes of death were nontyphoidal Salmonella spp. (28%), T. gondii (24%), Listeria monocytogenes (19%), and norovirus (11%). These estimates cannot be compared with prior (1999) estimates to assess trends because different methods were used. Additional data and more refined methods can improve future estimates.
PMID: 21192848 [PubMed - in process]
Self-Mating in the Definitive Host Potentiates Clonal Outbreaks of the Apicomplexan Parasites Sarcocystis neurona and Toxoplasma gondii
PLoS Genet. 2010 Dec 23;6(12):e1001261.
Self-Mating in the Definitive Host Potentiates Clonal Outbreaks of the Apicomplexan Parasites Sarcocystis neurona and Toxoplasma gondii
Wendte JM, Miller MA, Lambourn DM, Magargal SL, Jessup DA, Grigg ME.
Molecular Parasitology Unit, Laboratory of Parasitic Diseases, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
Abstract
Tissue-encysting coccidia, including Toxoplasma gondii and Sarcocystis neurona, are heterogamous parasites with sexual and asexual life stages in definitive and intermediate hosts, respectively. During its sexual life stage, T. gondii reproduces either by genetic out-crossing or via clonal amplification of a single strain through self-mating. Out-crossing has been experimentally verified as a potent mechanism capable of producing offspring possessing a range of adaptive and virulence potentials. In contrast, selfing and other life history traits, such as asexual expansion of tissue-cysts by oral transmission among intermediate hosts, have been proposed to explain the genetic basis for the clonal population structure of T. gondii. In this study, we investigated the contributing roles self-mating and sexual recombination play in nature to maintain clonal population structures and produce or expand parasite clones capable of causing disease epidemics for two tissue encysting parasites. We applied high-resolution genotyping against strains isolated from a T. gondii waterborne outbreak that caused symptomatic disease in 155 immune-competent people in Brazil and a S. neurona outbreak that resulted in a mass mortality event in Southern sea otters. In both cases, a single, genetically distinct clone was found infecting outbreak-exposed individuals. Furthermore, the T. gondii outbreak clone was one of several apparently recombinant progeny recovered from the local environment. Since oocysts or sporocysts were the infectious form implicated in each outbreak, the expansion of the epidemic clone can be explained by self-mating. The results also show that out-crossing preceded selfing to produce the virulent T. gondii clone. For the tissue encysting coccidia, self-mating exists as a key adaptation potentiating the epidemic expansion and transmission of newly emerged parasite clones that can profoundly shape parasite population genetic structures or cause devastating disease outbreaks.
PMID: 21203443 [PubMed - in process]
Self-Mating in the Definitive Host Potentiates Clonal Outbreaks of the Apicomplexan Parasites Sarcocystis neurona and Toxoplasma gondii
Wendte JM, Miller MA, Lambourn DM, Magargal SL, Jessup DA, Grigg ME.
Molecular Parasitology Unit, Laboratory of Parasitic Diseases, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
Abstract
Tissue-encysting coccidia, including Toxoplasma gondii and Sarcocystis neurona, are heterogamous parasites with sexual and asexual life stages in definitive and intermediate hosts, respectively. During its sexual life stage, T. gondii reproduces either by genetic out-crossing or via clonal amplification of a single strain through self-mating. Out-crossing has been experimentally verified as a potent mechanism capable of producing offspring possessing a range of adaptive and virulence potentials. In contrast, selfing and other life history traits, such as asexual expansion of tissue-cysts by oral transmission among intermediate hosts, have been proposed to explain the genetic basis for the clonal population structure of T. gondii. In this study, we investigated the contributing roles self-mating and sexual recombination play in nature to maintain clonal population structures and produce or expand parasite clones capable of causing disease epidemics for two tissue encysting parasites. We applied high-resolution genotyping against strains isolated from a T. gondii waterborne outbreak that caused symptomatic disease in 155 immune-competent people in Brazil and a S. neurona outbreak that resulted in a mass mortality event in Southern sea otters. In both cases, a single, genetically distinct clone was found infecting outbreak-exposed individuals. Furthermore, the T. gondii outbreak clone was one of several apparently recombinant progeny recovered from the local environment. Since oocysts or sporocysts were the infectious form implicated in each outbreak, the expansion of the epidemic clone can be explained by self-mating. The results also show that out-crossing preceded selfing to produce the virulent T. gondii clone. For the tissue encysting coccidia, self-mating exists as a key adaptation potentiating the epidemic expansion and transmission of newly emerged parasite clones that can profoundly shape parasite population genetic structures or cause devastating disease outbreaks.
PMID: 21203443 [PubMed - in process]
Wednesday, December 29, 2010
Host Cholesterol Synthesis Contributes to Growth of Intracellular Toxoplasma gondii in Macrophages
J Vet Med Sci. 2010 Dec 24. [Epub ahead of print]
Host Cholesterol Synthesis Contributes to Growth of Intracellular Toxoplasma gondii in Macrophages
Nishikawa Y, Ibrahim HM, Kameyama K, Shiga I, Hiasa J, Xuan X.
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine.
Abstract
The intracellular protozoan Toxoplasma gondii lacks the ability to synthesize sterol and scavenges cholesterol from the low-density lipoprotein receptor (LDLR) pathway of its host to facilitate replication. Sterol biosynthesis inhibitors, however, have a demonstrated anti-Toxoplasma effect. In this study, we examined the host mevalonate pathway as a novel source of cholesterol for T. gondii and its effects on parasite growth in macrophages. Parasite growth did not significantly change in the absence of LDLR or when LDL was exogenously supplemented. Lovastatin and compactin, both inhibitors of hydroxymethylglutaryl-CoA (HMG-CoA) reductase in the mevalonate pathway, significantly inhibited T. gondii growth in both wild-type and LDLR-knockout macrophages. Parasite growth was also suppressed by squalestatin, an inhibitor of squalene synthase, despite mevalonate producing isoprenoid intermediates in host cells. The present study demonstrates that lovastatin, compactin and squalestatin have anti-Toxoplasma activities and that the host cholesterol synthesis may contribute to parasite growth in macrophages.
PMID: 21187676
Host Cholesterol Synthesis Contributes to Growth of Intracellular Toxoplasma gondii in Macrophages
Nishikawa Y, Ibrahim HM, Kameyama K, Shiga I, Hiasa J, Xuan X.
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine.
Abstract
The intracellular protozoan Toxoplasma gondii lacks the ability to synthesize sterol and scavenges cholesterol from the low-density lipoprotein receptor (LDLR) pathway of its host to facilitate replication. Sterol biosynthesis inhibitors, however, have a demonstrated anti-Toxoplasma effect. In this study, we examined the host mevalonate pathway as a novel source of cholesterol for T. gondii and its effects on parasite growth in macrophages. Parasite growth did not significantly change in the absence of LDLR or when LDL was exogenously supplemented. Lovastatin and compactin, both inhibitors of hydroxymethylglutaryl-CoA (HMG-CoA) reductase in the mevalonate pathway, significantly inhibited T. gondii growth in both wild-type and LDLR-knockout macrophages. Parasite growth was also suppressed by squalestatin, an inhibitor of squalene synthase, despite mevalonate producing isoprenoid intermediates in host cells. The present study demonstrates that lovastatin, compactin and squalestatin have anti-Toxoplasma activities and that the host cholesterol synthesis may contribute to parasite growth in macrophages.
PMID: 21187676
Tuesday, December 28, 2010
Toxoplasma gondii: humoral and cellular immune response of BALB/c mice immunized via intranasal route with rTgROP2
Rev Bras Parasitol Vet. 2010 Oct-Dec;19(4):210-6.
Toxoplasma gondii: humoral and cellular immune response of BALB/c mice immunized via intranasal route with rTgROP2
Igarashi M, Zulpo DL, Cunha IA, Barros LD, Pereira VF, Taroda A, Navarro I, Vidotto O, Vidotto MC, Jenkins MC, Garcia JL.
Laboratório de Protozoologia, Departamento de Medicina Veterinária Preventiva, Universidade de Londrina - UEL, CP 6001, CEP 86050-970Londrina - PR, Brazil. jlgarcia@uel.br.
Abstract
TgROP2 is an intracellular protein associated with rhoptries of Toxoplama gondii and an antigen component of a candidate vaccine for toxoplasmosis. The purpose of the present study was to evaluate the efficacy of rTgROP2 to stimulate humoral and cellular immune responses in BALB/c mice via intranasal injection. TgROP2 partial coding sequence was (196-561) amplified by PCR from genomic T. gondii RH strain DNA and cloned into the pTrcHis expression vector. Escherichia coli Rosetta 2 cells transformed with pTrcHis-TgROP2 showed high levels (~1 mg.mL(-1)) of recombinant protein after 4 hours of IPTG induction. Recombinant TgROP2 exhibited an apparent Mr equal to 54 kDa. In order to test immunogenicity of the recombinant protein, 10 BALB/c mice received 10 µg of rROP2 protein + 10 µg of Quil-A via intranasal injection. Doses were administered at days 0, 21, and 42. Three animals were euthanized and used to evaluate cell-ular immune response on day 62. Five (50%) and two (20%) out of ten animals produced IgG (DO mean = 0.307; cut-off = 0.240) and IgA (DO mean = 0.133, cut-off = 0.101), respectively, by ELISA on day 62. The proliferation of splenocytes revealed high stimulation index (SI) when co-cultured with 5, 10 and 15 µg.mL(-1) of rTgROP2. These results indicate that intranasal immunization with recombinant protein ROP2 plus Quil-A can elicit both cellular and humoral immune responses in BALB/c mice.
PMID: 21184696
Toxoplasma gondii: humoral and cellular immune response of BALB/c mice immunized via intranasal route with rTgROP2
Igarashi M, Zulpo DL, Cunha IA, Barros LD, Pereira VF, Taroda A, Navarro I, Vidotto O, Vidotto MC, Jenkins MC, Garcia JL.
Laboratório de Protozoologia, Departamento de Medicina Veterinária Preventiva, Universidade de Londrina - UEL, CP 6001, CEP 86050-970Londrina - PR, Brazil. jlgarcia@uel.br.
Abstract
TgROP2 is an intracellular protein associated with rhoptries of Toxoplama gondii and an antigen component of a candidate vaccine for toxoplasmosis. The purpose of the present study was to evaluate the efficacy of rTgROP2 to stimulate humoral and cellular immune responses in BALB/c mice via intranasal injection. TgROP2 partial coding sequence was (196-561) amplified by PCR from genomic T. gondii RH strain DNA and cloned into the pTrcHis expression vector. Escherichia coli Rosetta 2 cells transformed with pTrcHis-TgROP2 showed high levels (~1 mg.mL(-1)) of recombinant protein after 4 hours of IPTG induction. Recombinant TgROP2 exhibited an apparent Mr equal to 54 kDa. In order to test immunogenicity of the recombinant protein, 10 BALB/c mice received 10 µg of rROP2 protein + 10 µg of Quil-A via intranasal injection. Doses were administered at days 0, 21, and 42. Three animals were euthanized and used to evaluate cell-ular immune response on day 62. Five (50%) and two (20%) out of ten animals produced IgG (DO mean = 0.307; cut-off = 0.240) and IgA (DO mean = 0.133, cut-off = 0.101), respectively, by ELISA on day 62. The proliferation of splenocytes revealed high stimulation index (SI) when co-cultured with 5, 10 and 15 µg.mL(-1) of rTgROP2. These results indicate that intranasal immunization with recombinant protein ROP2 plus Quil-A can elicit both cellular and humoral immune responses in BALB/c mice.
PMID: 21184696
High level of soluble HLA-G in amniotic fluid is correlated with congenital transmission of Toxoplasma gondii
Clin Immunol. 2010 Dec 23. [Epub ahead of print]
High level of soluble HLA-G in amniotic fluid is correlated with congenital transmission of Toxoplasma gondii
Robert-Gangneux F, Gangneux JP, Vu N, Jaillard S, Guiguen C, Amiot L.
Laboratoire de Parasitologie, Faculté de Médecine et Centre Hospitalier Universitaire de Rennes, Rennes, France; Unité EA4427-SERAIC (Signalisation et réponse aux agents infectieux et chimiques), IRSET (Institut de Recherche en Santé Environnement Travail), Université Rennes 1, Rennes, France.
Abstract
The expression of human leukocyte antigen (HLA)-G on cytotrophoblast cells contributes to maternal-fetal tolerance. Soluble forms of HLA-G (sHLA-G) can be detected in amniotic fluid (AF) and a decrease of sHLA-G is known to be correlated to fetal loss. In this work we investigated the role of sHLA-G in the transplacental passage of the protozoan parasite Toxoplasma gondii, responsible for congenital toxoplasmosis in about 30% of fetuses when primary infection (PI) occurs during pregnancy. We determined the sHLA-G concentration in 61 AF from women with PI and 24 controls. Our results showed higher sHLA-G levels in AF from PI than in controls (p<0.001). Moreover sHLA-G level from congenitally infected fetuses (n=12) was higher than in fetus in whom congenital infection was ruled out (n=49, p<0.05). These data suggest that sHLA-G could participate in immunomodulation necessary to avoid fetal loss due to Toxoplasma infection, but that over-expression could favor congenital transmission.
Copyright © 2010. Published by Elsevier Inc.
PMID: 21185786
High level of soluble HLA-G in amniotic fluid is correlated with congenital transmission of Toxoplasma gondii
Robert-Gangneux F, Gangneux JP, Vu N, Jaillard S, Guiguen C, Amiot L.
Laboratoire de Parasitologie, Faculté de Médecine et Centre Hospitalier Universitaire de Rennes, Rennes, France; Unité EA4427-SERAIC (Signalisation et réponse aux agents infectieux et chimiques), IRSET (Institut de Recherche en Santé Environnement Travail), Université Rennes 1, Rennes, France.
Abstract
The expression of human leukocyte antigen (HLA)-G on cytotrophoblast cells contributes to maternal-fetal tolerance. Soluble forms of HLA-G (sHLA-G) can be detected in amniotic fluid (AF) and a decrease of sHLA-G is known to be correlated to fetal loss. In this work we investigated the role of sHLA-G in the transplacental passage of the protozoan parasite Toxoplasma gondii, responsible for congenital toxoplasmosis in about 30% of fetuses when primary infection (PI) occurs during pregnancy. We determined the sHLA-G concentration in 61 AF from women with PI and 24 controls. Our results showed higher sHLA-G levels in AF from PI than in controls (p<0.001). Moreover sHLA-G level from congenitally infected fetuses (n=12) was higher than in fetus in whom congenital infection was ruled out (n=49, p<0.05). These data suggest that sHLA-G could participate in immunomodulation necessary to avoid fetal loss due to Toxoplasma infection, but that over-expression could favor congenital transmission.
Copyright © 2010. Published by Elsevier Inc.
PMID: 21185786
Saturday, December 25, 2010
Toxoplasma gondii Lysine Acetyltransferase GCN5-A Functions in the Cellular Response to Alkaline Stress and Expression of Cyst Genes
PLoS Pathog. 2010 Dec 16;6(12):e1001232.
Toxoplasma gondii Lysine Acetyltransferase GCN5-A Functions in the Cellular Response to Alkaline Stress and Expression of Cyst Genes
Naguleswaran A, Elias EV, McClintick J, Edenberg HJ, Sullivan WJ.
Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America.
Abstract
Parasitic protozoa such as the apicomplexan Toxoplasma gondii progress through their life cycle in response to stimuli in the environment or host organism. Very little is known about how proliferating tachyzoites reprogram their expressed genome in response to stresses that prompt development into latent bradyzoite cysts. We have previously linked histone acetylation with the expression of stage-specific genes, but the factors involved remain to be determined. We sought to determine if GCN5, which operates as a transcriptional co-activator by virtue of its histone acetyltransferase (HAT) activity, contributed to stress-induced changes in gene expression in Toxoplasma. In contrast to other lower eukaryotes, Toxoplasma has duplicated its GCN5 lysine acetyltransferase (KAT). Disruption of the gene encoding for TgGCN5-A in type I RH strain did not produce a severe phenotype under normal culture conditions, but here we show that the TgGCN5-A null mutant is deficient in responding to alkaline pH, a common stress used to induce bradyzoite differentiation in vitro. We performed a genome-wide analysis of the Toxoplasma transcriptional response to alkaline pH stress, finding that parasites deleted for TgGCN5-A fail to up-regulate 74% of the stress response genes that are induced 2-fold or more in wild-type. Using chromatin immunoprecipitation, we verify an enrichment of TgGCN5-A at the upstream regions of genes activated by alkaline pH exposure. The TgGCN5-A knockout is also incapable of up-regulating key marker genes expressed during development of the latent cyst form, and is impaired in its ability to recover from alkaline stress. Complementation of the TgGCN5-A knockout restores the expression of these stress-induced genes and reverses the stress recovery defect. These results establish TgGCN5-A as a major contributor to the alkaline stress response in RH strain Toxoplasma.
PMID: 21179246
Toxoplasma gondii Lysine Acetyltransferase GCN5-A Functions in the Cellular Response to Alkaline Stress and Expression of Cyst Genes
Naguleswaran A, Elias EV, McClintick J, Edenberg HJ, Sullivan WJ.
Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America.
Abstract
Parasitic protozoa such as the apicomplexan Toxoplasma gondii progress through their life cycle in response to stimuli in the environment or host organism. Very little is known about how proliferating tachyzoites reprogram their expressed genome in response to stresses that prompt development into latent bradyzoite cysts. We have previously linked histone acetylation with the expression of stage-specific genes, but the factors involved remain to be determined. We sought to determine if GCN5, which operates as a transcriptional co-activator by virtue of its histone acetyltransferase (HAT) activity, contributed to stress-induced changes in gene expression in Toxoplasma. In contrast to other lower eukaryotes, Toxoplasma has duplicated its GCN5 lysine acetyltransferase (KAT). Disruption of the gene encoding for TgGCN5-A in type I RH strain did not produce a severe phenotype under normal culture conditions, but here we show that the TgGCN5-A null mutant is deficient in responding to alkaline pH, a common stress used to induce bradyzoite differentiation in vitro. We performed a genome-wide analysis of the Toxoplasma transcriptional response to alkaline pH stress, finding that parasites deleted for TgGCN5-A fail to up-regulate 74% of the stress response genes that are induced 2-fold or more in wild-type. Using chromatin immunoprecipitation, we verify an enrichment of TgGCN5-A at the upstream regions of genes activated by alkaline pH exposure. The TgGCN5-A knockout is also incapable of up-regulating key marker genes expressed during development of the latent cyst form, and is impaired in its ability to recover from alkaline stress. Complementation of the TgGCN5-A knockout restores the expression of these stress-induced genes and reverses the stress recovery defect. These results establish TgGCN5-A as a major contributor to the alkaline stress response in RH strain Toxoplasma.
PMID: 21179246
Evaluation of three novel azasterols against Toxoplasma gondii
Vet Parasitol. 2010 Dec 1. [Epub ahead of print]
Evaluation of three novel azasterols against Toxoplasma gondii
Martins-Duarte ES, Lemgruber L, Lorente SO, Gros L, Magaraci F, Gilbert IH, de Souza W, Vommaro RC.
Laboratório de Ultraestrutura Celular Herth, Meyer, Instituto de Biofísica Carlos Chagas Filho, UFRJ, CCS, Bloco G, Av. Carlo, Chagas Filho, Cidade Universitária, Ilha do Fundão, 21941-902, Rio de Janeiro, RJ, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil.
Abstract
Previous studies from our group have demonstrated the high susceptibility of Toxoplasma gondii tachyzoites to the sterol analogues 22,26-azasterol and 24,25-(R,S)-epiminolanosterol. In this work we present data on testing in vitro three novel azasterols as potential agents for the treatment of toxoplasmosis. The three compounds inhibited parasite growth at micromolar concentrations, in a dose-dependent manner. Electron microscopy analysis of intracellular tachyzoites after treatment with the most effective compound showed drastic mitochondrion swelling associated with the appearance of an electron-lucent matrix and disrupted cristae. Parasite lysis also took place. The appearance of electron dense cytoplasmic structures similar to amylopectin granules distributed throughout the parasite suggests that azasterols might be inducing differentiation of those tachyzoites which were not lysed to the bradyzoite stage.
Copyright © 2010 Elsevier B.V. All rights reserved.
PMID: 21176865
Evaluation of three novel azasterols against Toxoplasma gondii
Martins-Duarte ES, Lemgruber L, Lorente SO, Gros L, Magaraci F, Gilbert IH, de Souza W, Vommaro RC.
Laboratório de Ultraestrutura Celular Herth, Meyer, Instituto de Biofísica Carlos Chagas Filho, UFRJ, CCS, Bloco G, Av. Carlo, Chagas Filho, Cidade Universitária, Ilha do Fundão, 21941-902, Rio de Janeiro, RJ, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil.
Abstract
Previous studies from our group have demonstrated the high susceptibility of Toxoplasma gondii tachyzoites to the sterol analogues 22,26-azasterol and 24,25-(R,S)-epiminolanosterol. In this work we present data on testing in vitro three novel azasterols as potential agents for the treatment of toxoplasmosis. The three compounds inhibited parasite growth at micromolar concentrations, in a dose-dependent manner. Electron microscopy analysis of intracellular tachyzoites after treatment with the most effective compound showed drastic mitochondrion swelling associated with the appearance of an electron-lucent matrix and disrupted cristae. Parasite lysis also took place. The appearance of electron dense cytoplasmic structures similar to amylopectin granules distributed throughout the parasite suggests that azasterols might be inducing differentiation of those tachyzoites which were not lysed to the bradyzoite stage.
Copyright © 2010 Elsevier B.V. All rights reserved.
PMID: 21176865
Tuesday, December 21, 2010
Cell cycle-dependent, intercellular transmission of Toxoplasma gondii is accompanied by marked changes in parasite gene expression
Mol Microbiol. 2011 Jan;79(1):192-204. doi: 10.1111/j.1365-2958.2010.07441.x. Epub 2010 Nov 9.
Cell cycle-dependent, intercellular transmission of Toxoplasma gondii is accompanied by marked changes in parasite gene expression
Gaji RY, Behnke MS, Lehmann MM, White MW, Carruthers VB.
Department of Microbiology and Immunology, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA Department of Veterinary Molecular Biology, Montana State University, Bozeman, MT 59717, USA Departments of Molecular Medicine & Global Health, University of South Florida, Tampa, FL 33612, USA.
Abstract
Intracellular microbes have evolved efficient strategies for transitioning from one cell to another in a process termed intercellular transmission. Here we show that host cell transmission of the obligate intracellular parasite Toxoplasma gondii is closely tied to specific cell cycle distributions, with egress and reinvasion occurring most proficiently by parasites in the G1 phase. We also reveal that Toxoplasma undergoes marked changes in mRNA expression when transitioning from the extracellular environment to its intracellular niche. These mRNA level changes reflect a modal switch from expression of proteins involved in invasion, motility and signal transduction in extracellular parasites to expression of metabolic and DNA replication proteins in intracellular parasites. Host cell binding and signalling associated with the discharge of parasite secretory proteins was not sufficient to induce this switch in gene expression, suggesting that the regulatory mechanisms responsible are tied to the establishment of the intracellular environment. The genes whose expression increased after parasite invasion belong to a progressive cascade known to underlie the parasite division cycle indicating that the unique relationship between the G1 phase and invasion effectively synchronizes short-term population growth. This work provides new insight into how this highly successful parasite competently transits from cell to cell.
© 2010 Blackwell Publishing Ltd.
PMID: 21166903
Cell cycle-dependent, intercellular transmission of Toxoplasma gondii is accompanied by marked changes in parasite gene expression
Gaji RY, Behnke MS, Lehmann MM, White MW, Carruthers VB.
Department of Microbiology and Immunology, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA Department of Veterinary Molecular Biology, Montana State University, Bozeman, MT 59717, USA Departments of Molecular Medicine & Global Health, University of South Florida, Tampa, FL 33612, USA.
Abstract
Intracellular microbes have evolved efficient strategies for transitioning from one cell to another in a process termed intercellular transmission. Here we show that host cell transmission of the obligate intracellular parasite Toxoplasma gondii is closely tied to specific cell cycle distributions, with egress and reinvasion occurring most proficiently by parasites in the G1 phase. We also reveal that Toxoplasma undergoes marked changes in mRNA expression when transitioning from the extracellular environment to its intracellular niche. These mRNA level changes reflect a modal switch from expression of proteins involved in invasion, motility and signal transduction in extracellular parasites to expression of metabolic and DNA replication proteins in intracellular parasites. Host cell binding and signalling associated with the discharge of parasite secretory proteins was not sufficient to induce this switch in gene expression, suggesting that the regulatory mechanisms responsible are tied to the establishment of the intracellular environment. The genes whose expression increased after parasite invasion belong to a progressive cascade known to underlie the parasite division cycle indicating that the unique relationship between the G1 phase and invasion effectively synchronizes short-term population growth. This work provides new insight into how this highly successful parasite competently transits from cell to cell.
© 2010 Blackwell Publishing Ltd.
PMID: 21166903
Saturday, December 18, 2010
The apicoplast
Protoplasma. 2010 Dec 17. [Epub ahead of print]
The apicoplast
McFadden GI.
School of Botany, University of Melbourne, Melbourne, VIC, 3010, Australia, gim@unimelb.edu.au.
Abstract
Parasites like malaria and Toxoplasma possess a vestigial plastid homologous to the chloroplasts of plants. The plastid (known as the apicoplast) is non-photosynthetic but retains many hallmarks of its ancestry including a circular genome that it synthesises proteins from and a suite of biosynthetic pathways of cyanobacterial origin. In this review, the discovery of the apicoplast and its integration, function and purpose are explored. New insights into the apicoplast fatty acid biosynthesis pathway and some novel roles of the apicoplast in vaccine development are reviewed.
PMID: 21165662
The apicoplast
McFadden GI.
School of Botany, University of Melbourne, Melbourne, VIC, 3010, Australia, gim@unimelb.edu.au.
Abstract
Parasites like malaria and Toxoplasma possess a vestigial plastid homologous to the chloroplasts of plants. The plastid (known as the apicoplast) is non-photosynthetic but retains many hallmarks of its ancestry including a circular genome that it synthesises proteins from and a suite of biosynthetic pathways of cyanobacterial origin. In this review, the discovery of the apicoplast and its integration, function and purpose are explored. New insights into the apicoplast fatty acid biosynthesis pathway and some novel roles of the apicoplast in vaccine development are reviewed.
PMID: 21165662
Thursday, December 16, 2010
Post-genomics resources and tools for studying apicomplexan metabolism
Trends Parasitol. 2010 Dec 8. [Epub ahead of print]
Post-genomics resources and tools for studying apicomplexan metabolism
Hung SS, Parkinson J.
Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, Ontario, Canada and Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
Abstract
The phylum Apicomplexa comprises over 5000 species of obligate intracellular parasites, many responsible for diseases that significantly impact human health and economics. To aid drug development programs, global sequencing initiatives are generating increasing numbers of apicomplexan genomes. The challenge is how best to exploit these resources to identify effective therapeutic targets. Because of its important role in growth and maintenance, much interest has centred on metabolism. However, in the absence of detailed biochemical data, reconstructing the metabolic potential from a fully sequenced genome remains problematic. In this review current resources and tools facilitating the metabolic reconstruction for apicomplexans are examined. Furthermore, how these datasets can be utilized to explore the metabolic capabilities of apicomplexans are discussed and targets for therapeutic intervention are prioritized.
Copyright © 2010 Elsevier Ltd. All rights reserved.
PMID: 21145790 [PubMed - as supplied by publisher]
Post-genomics resources and tools for studying apicomplexan metabolism
Hung SS, Parkinson J.
Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, Ontario, Canada and Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
Abstract
The phylum Apicomplexa comprises over 5000 species of obligate intracellular parasites, many responsible for diseases that significantly impact human health and economics. To aid drug development programs, global sequencing initiatives are generating increasing numbers of apicomplexan genomes. The challenge is how best to exploit these resources to identify effective therapeutic targets. Because of its important role in growth and maintenance, much interest has centred on metabolism. However, in the absence of detailed biochemical data, reconstructing the metabolic potential from a fully sequenced genome remains problematic. In this review current resources and tools facilitating the metabolic reconstruction for apicomplexans are examined. Furthermore, how these datasets can be utilized to explore the metabolic capabilities of apicomplexans are discussed and targets for therapeutic intervention are prioritized.
Copyright © 2010 Elsevier Ltd. All rights reserved.
PMID: 21145790 [PubMed - as supplied by publisher]
Unusual anchor of a motor complex (MyoD-MLC2) to the plasma membrane of Toxoplasma gondii
Traffic. 2010 Dec 9. doi: 10.1111/j.1600-0854.2010.01148.x. [Epub ahead of print]
Unusual anchor of a motor complex (MyoD-MLC2) to the plasma membrane of Toxoplasma gondii
Polonais V, Foth BJ, Chinthalapudi K, Marq JB, Manstein DJ, Soldati-Favre D, Frénal K.
Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 Rue Michel-Servet, CH-1211 Geneva 4, Switzerland Research Division for Structural Analysis, Hannover Medical School, OE8830, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany Institute für Biophysical Chemistry, Hannover Medical School, OE4350, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany.
Abstract
Toxoplasma gondii possesses 11 rather atypical myosin heavy chains. The only myosin light chain described to date is MLC1, associated to myosin A, and contributing to gliding motility. In this study, we examined the repertoire of calmodulin-like proteins in Apicomplexans, identified six putative myosin light chains and determined their subcellular localization in T. gondii and Plasmodium falciparum. MLC2, only found in coccidians, is associated to myosin D via its CaM-like domain and anchored to the plasma membrane of T. gondii via its N-terminal extension. Molecular modeling suggests that MyoD-MLC2 complex is more compact than the reported structure of Plasmodium MyoA-MTIP complex. Anchorage of this MLC2 to the plasma membrane is likely governed by palmitoylation.
© 2010 John Wiley & Sons A/S.
PMID: 21143563 [PubMed - as supplied by publisher]
Unusual anchor of a motor complex (MyoD-MLC2) to the plasma membrane of Toxoplasma gondii
Polonais V, Foth BJ, Chinthalapudi K, Marq JB, Manstein DJ, Soldati-Favre D, Frénal K.
Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 Rue Michel-Servet, CH-1211 Geneva 4, Switzerland Research Division for Structural Analysis, Hannover Medical School, OE8830, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany Institute für Biophysical Chemistry, Hannover Medical School, OE4350, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany.
Abstract
Toxoplasma gondii possesses 11 rather atypical myosin heavy chains. The only myosin light chain described to date is MLC1, associated to myosin A, and contributing to gliding motility. In this study, we examined the repertoire of calmodulin-like proteins in Apicomplexans, identified six putative myosin light chains and determined their subcellular localization in T. gondii and Plasmodium falciparum. MLC2, only found in coccidians, is associated to myosin D via its CaM-like domain and anchored to the plasma membrane of T. gondii via its N-terminal extension. Molecular modeling suggests that MyoD-MLC2 complex is more compact than the reported structure of Plasmodium MyoA-MTIP complex. Anchorage of this MLC2 to the plasma membrane is likely governed by palmitoylation.
© 2010 John Wiley & Sons A/S.
PMID: 21143563 [PubMed - as supplied by publisher]
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