Science. 2013 May 10;340(6133):701-6. doi: 10.1126/science.1233028.
Cellular self-defense: how cell-autonomous immunity protects against pathogens
Randow F, MacMicking JD, James LC.
Medical Research Council Laboratory of Molecular Biology, Division of Protein and Nucleic Acid Chemistry, Cambridge, UK. randow@mrc-lmb.cam.ac.uk
Our prevailing view of vertebrate host defense is strongly shaped by the notion of a specialized set of immune cells as sole guardians of antimicrobial resistance. Yet this view greatly underestimates a capacity for most cell lineages-the majority of which fall outside the traditional province of the immune system-to defend themselves against infection. This ancient and ubiquitous form of host protection is termed cell-autonomous immunity and operates across all three domains of life. Here, we discuss the organizing principles that govern cellular self-defense and how intracellular compartmentalization has shaped its activities to provide effective protection against a wide variety of microbial pathogens.
PMID: 23661752 [PubMed - indexed for MEDLINE]
Friday, May 24, 2013
Toxoplasma gondii myosin F, an essential motor for centrosomes positioning and apicoplast inheritance
EMBO J. 2013 May 21. doi: 10.1038/emboj.2013.113. [Epub ahead of print]
Toxoplasma gondii myosin F, an essential motor for centrosomes positioning and apicoplast inheritance
Jacot D, Daher W, Soldati-Favre D.
Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Geneva, Switzerland.
Members of the Apicomplexa phylum possess an organelle surrounded by four membranes, originating from the secondary endosymbiosis of a red alga. This so-called apicoplast hosts essential metabolic pathways. We report here that apicoplast inheritance is an actin-based process. Concordantly, parasites depleted in either profilin or actin depolymerizing factor, or parasites overexpressing the FH2 domain of formin 2, result in loss of the apicoplast. The class XXII myosin F (MyoF) is conserved across the phylum and localizes in the vicinity of the Toxoplasma gondii apicoplast during division. Conditional knockdown of TgMyoF severely affects apicoplast turnover, leading to parasite death. This recapitulates the phenotype observed upon perturbation of actin dynamics that led to the accumulation of the apicoplast and secretory organelles in enlarged residual bodies. To further dissect the mode of action of this motor, we conditionally stabilized the tail of MyoF, which forms an inactive heterodimer with endogenous TgMyoF. This dominant negative mutant reveals a central role of this motor in the positioning of the two centrosomes prior to daughter cell formation and in apicoplast segregation.
PMID: 23695356 [PubMed - as supplied by publisher]
Toxoplasma gondii myosin F, an essential motor for centrosomes positioning and apicoplast inheritance
Jacot D, Daher W, Soldati-Favre D.
Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Geneva, Switzerland.
Members of the Apicomplexa phylum possess an organelle surrounded by four membranes, originating from the secondary endosymbiosis of a red alga. This so-called apicoplast hosts essential metabolic pathways. We report here that apicoplast inheritance is an actin-based process. Concordantly, parasites depleted in either profilin or actin depolymerizing factor, or parasites overexpressing the FH2 domain of formin 2, result in loss of the apicoplast. The class XXII myosin F (MyoF) is conserved across the phylum and localizes in the vicinity of the Toxoplasma gondii apicoplast during division. Conditional knockdown of TgMyoF severely affects apicoplast turnover, leading to parasite death. This recapitulates the phenotype observed upon perturbation of actin dynamics that led to the accumulation of the apicoplast and secretory organelles in enlarged residual bodies. To further dissect the mode of action of this motor, we conditionally stabilized the tail of MyoF, which forms an inactive heterodimer with endogenous TgMyoF. This dominant negative mutant reveals a central role of this motor in the positioning of the two centrosomes prior to daughter cell formation and in apicoplast segregation.
PMID: 23695356 [PubMed - as supplied by publisher]
Wednesday, May 22, 2013
A SAS-6-Like Protein Suggests that the Toxoplasma Conoid Complex Evolved from Flagellar Components
Eukaryot Cell. 2013 May 17. [Epub ahead of print]
A SAS-6-Like Protein Suggests that the Toxoplasma Conoid Complex Evolved from Flagellar Components
Deleon JC, Scheumann N, Beatty W, Beck JR, Tran JQ, Yau C, Bradley PJ, Gull K, Wickstead B, Morrissette NS.
Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine CA 92697.
SAS-6 is required for centriole biogenesis in diverse eukaryotes. Here, we describe a novel family of SAS-6-like (SAS6L) proteins that share an N-terminal domain with SAS-6, but lack coiled-coil tails. SAS6L proteins are found in a subset of eukaryotes that contain SAS-6, including diverse protozoa and green algae. In the apicomplexan parasite Toxoplasma gondii SAS-6 localizes to the centriole, but SAS6L is found above the conoid, an enigmatic tubulin-containing structure found at the apex of a subset of alveolate organisms. Loss of SAS6L causes reduced fitness in Toxoplasma. The Trypanosoma brucei homolog of SAS6L localizes to the basal plate region, the site in the axoneme where the central pair microtubules are nucleated. When endogenous SAS6L is overexpressed in Toxoplasma tachyzoites or Trypanosoma trypomastigotes, it forms prominent filaments that extend through the cell cytoplasm, indicating that it retains a capacity to form higher-order structures despite lacking a coiled coil domain. We conclude that although SAS6L proteins share a conserved domain with SAS-6, they are a functionally distinct family that pre-dates the last common ancestor of eukaryotes. Moreover, the distinct localization of the SAS6L protein in Trypanosoma and Toxoplasma adds weight to the hypothesis that the conoid complex evolved from flagellar components.
PMID: 23687115 [PubMed - as supplied by publisher]
A SAS-6-Like Protein Suggests that the Toxoplasma Conoid Complex Evolved from Flagellar Components
Deleon JC, Scheumann N, Beatty W, Beck JR, Tran JQ, Yau C, Bradley PJ, Gull K, Wickstead B, Morrissette NS.
Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine CA 92697.
SAS-6 is required for centriole biogenesis in diverse eukaryotes. Here, we describe a novel family of SAS-6-like (SAS6L) proteins that share an N-terminal domain with SAS-6, but lack coiled-coil tails. SAS6L proteins are found in a subset of eukaryotes that contain SAS-6, including diverse protozoa and green algae. In the apicomplexan parasite Toxoplasma gondii SAS-6 localizes to the centriole, but SAS6L is found above the conoid, an enigmatic tubulin-containing structure found at the apex of a subset of alveolate organisms. Loss of SAS6L causes reduced fitness in Toxoplasma. The Trypanosoma brucei homolog of SAS6L localizes to the basal plate region, the site in the axoneme where the central pair microtubules are nucleated. When endogenous SAS6L is overexpressed in Toxoplasma tachyzoites or Trypanosoma trypomastigotes, it forms prominent filaments that extend through the cell cytoplasm, indicating that it retains a capacity to form higher-order structures despite lacking a coiled coil domain. We conclude that although SAS6L proteins share a conserved domain with SAS-6, they are a functionally distinct family that pre-dates the last common ancestor of eukaryotes. Moreover, the distinct localization of the SAS6L protein in Trypanosoma and Toxoplasma adds weight to the hypothesis that the conoid complex evolved from flagellar components.
PMID: 23687115 [PubMed - as supplied by publisher]
Identification of functional modules of AKMT, a novel lysine methyltransferase regulating the motility of Toxoplasma gondii
Mol Biochem Parasitol. 2013 May 16. pii: S0166-6851(13)00071-6. doi: 10.1016/j.molbiopara.2013.05.004. [Epub ahead of print]
Identification of functional modules of AKMT, a novel lysine methyltransferase regulating the motility of Toxoplasma gondii
Sivagurunathan S, Heaslip A, Liu J, Hu K.
From the Department of Biology, Indiana University, Bloomington, IN, 47405, USA
The intracellular parasite Toxoplasma gondii is a leading cause of congenital neurological defects. To cause disease, it must reiterate its lytic cycle through host cell invasion, replication, and parasite egress. This requires the parasite to sense changes in its environment and switch between the non-motile (for replication) and motile (for invasion and egress) states appropriately. Recently, we discovered a previously unknown mechanism of motility regulation in T. gondii, mediated by a lysine methyltransferase, AKMT (for Apical complex lysine (K) methyltransferase). When AKMT is absent, activation of motility is inhibited, which compromises parasite invasion and egress, and thus severely impairs the lytic cycle. Although the methyltransferase activity of AKMT has been established, the phylogenetic relationship of AKMT with other better studied lysine methyltransferases (KMTs) was not known. Also unknown was the functional relationships between different domains of AKMT. In this work we carried out phylogenetic analyses, which show that AKMT orthologs form a new subfamily of KMTs. We systematically generated truncation mutants of AKMT, and discovered that the predicted enzymatic domain alone is a very poor enzyme and cannot complement the function of AKMT in vivo. Interestingly, the N- and C-terminal domains of the AKMT have drastically different impacts on its enzyme activity, localization as well as in vivo function. Our results thus reveal that AKMT is an unusual, parasite-specific enzyme and identified regions and interactions within this novel lysine methyltransferase that can be used as drug targets.
PMID: 23685344 [PubMed - as supplied by publisher]
Identification of functional modules of AKMT, a novel lysine methyltransferase regulating the motility of Toxoplasma gondii
Sivagurunathan S, Heaslip A, Liu J, Hu K.
From the Department of Biology, Indiana University, Bloomington, IN, 47405, USA
The intracellular parasite Toxoplasma gondii is a leading cause of congenital neurological defects. To cause disease, it must reiterate its lytic cycle through host cell invasion, replication, and parasite egress. This requires the parasite to sense changes in its environment and switch between the non-motile (for replication) and motile (for invasion and egress) states appropriately. Recently, we discovered a previously unknown mechanism of motility regulation in T. gondii, mediated by a lysine methyltransferase, AKMT (for Apical complex lysine (K) methyltransferase). When AKMT is absent, activation of motility is inhibited, which compromises parasite invasion and egress, and thus severely impairs the lytic cycle. Although the methyltransferase activity of AKMT has been established, the phylogenetic relationship of AKMT with other better studied lysine methyltransferases (KMTs) was not known. Also unknown was the functional relationships between different domains of AKMT. In this work we carried out phylogenetic analyses, which show that AKMT orthologs form a new subfamily of KMTs. We systematically generated truncation mutants of AKMT, and discovered that the predicted enzymatic domain alone is a very poor enzyme and cannot complement the function of AKMT in vivo. Interestingly, the N- and C-terminal domains of the AKMT have drastically different impacts on its enzyme activity, localization as well as in vivo function. Our results thus reveal that AKMT is an unusual, parasite-specific enzyme and identified regions and interactions within this novel lysine methyltransferase that can be used as drug targets.
PMID: 23685344 [PubMed - as supplied by publisher]
Monday, May 20, 2013
Protein kinases of Toxoplasma gondii: functions and drug targets
Parasitol Res. 2013 May 17. [Epub ahead of print]
Protein kinases of Toxoplasma gondii: functions and drug targets
Wei F, Wang W, Liu Q.
College of Life Science, Jilin Agricultural University, 2888 Xincheng Street, Changchun, 130118, People's Republic of China.
Toxoplasma gondii is an important opportunistic parasite that infects almost all warm-blooded animals, causing congenital neurological and ocular diseases, especially in immunocompromised humans. The available therapeutic drugs are hypersensitive and toxic, and no vaccine is available to block the transmission of this parasite. Safer and more effective drugs are thus urgently needed to treat toxoplasmosis. Protein kinases (PKs) play crucial roles in the proliferation, differentiation, and pathogenesis of T. gondii. T. gondii calcium-dependent protein kinase 1 and cGMP-dependent protein kinase are associated with cell invasion; mitogen-activated protein kinase 1 and cAMP-dependent protein kinase are involved in stress response and conversion from tachyzoite to bradyzoite; casein kinase 1 and cdc2 cyclin-dependent kinase control cell cycle. Rhoptry kinases, the T. gondii-specific PKs, are involved in host manipulation. Because of their difference in structure and function from that of mammalian PKs, T. gondii PKs are promising drug targets. In this review, we describe the functions of T. gondii protein kinases and their inhibitors as potential drugs against T. gondii.
PMID: 23681193 [PubMed - as supplied by publisher]
Protein kinases of Toxoplasma gondii: functions and drug targets
Wei F, Wang W, Liu Q.
College of Life Science, Jilin Agricultural University, 2888 Xincheng Street, Changchun, 130118, People's Republic of China.
Toxoplasma gondii is an important opportunistic parasite that infects almost all warm-blooded animals, causing congenital neurological and ocular diseases, especially in immunocompromised humans. The available therapeutic drugs are hypersensitive and toxic, and no vaccine is available to block the transmission of this parasite. Safer and more effective drugs are thus urgently needed to treat toxoplasmosis. Protein kinases (PKs) play crucial roles in the proliferation, differentiation, and pathogenesis of T. gondii. T. gondii calcium-dependent protein kinase 1 and cGMP-dependent protein kinase are associated with cell invasion; mitogen-activated protein kinase 1 and cAMP-dependent protein kinase are involved in stress response and conversion from tachyzoite to bradyzoite; casein kinase 1 and cdc2 cyclin-dependent kinase control cell cycle. Rhoptry kinases, the T. gondii-specific PKs, are involved in host manipulation. Because of their difference in structure and function from that of mammalian PKs, T. gondii PKs are promising drug targets. In this review, we describe the functions of T. gondii protein kinases and their inhibitors as potential drugs against T. gondii.
PMID: 23681193 [PubMed - as supplied by publisher]
Wednesday, May 15, 2013
The Unfolded Protein Response in the protozoan parasite Toxoplasma gondii features translational and transcriptional control
Eukaryot Cell. 2013 May 10. [Epub ahead of print]
The Unfolded Protein Response in the protozoan parasite Toxoplasma gondii features translational and transcriptional control
Joyce BR, Tampaki Z, Kim K, Wek RC, Sullivan WJ Jr.
Department of Pharmacology & Toxicology
Indiana University School of Medicine
The Unfolded Protein Response (UPR) is an important regulatory network that responds to perturbations in protein homeostasis in the endoplasmic reticulum (ER). In mammalian cells, the UPR features translational and transcriptional mechanisms of gene expression aimed at restoring proteostatic control. A central feature of the UPR is phosphorylation of the α subunit of eIF2 by PERK (EIF2AK3/PEK), which reduces the influx of nascent proteins into the ER by lowering global protein synthesis, coincident with preferential translation of key transcription activators of genes that function to expand the processing capacity of this secretory organelle. Upon ER stress, the apicomplexan parasite Toxoplasma gondii is known to induce phosphorylation of Toxoplasma eIF2α and lower translation initiation. To characterize the nature of the ensuing UPR in this parasite, we carried out microarray analyses to measure the changes in the transcriptome and in translational control during ER stress. We determined that a collection of transcripts linked with the secretory process are induced in response to ER stress, supporting the idea that a transcriptional induction phase of the UPR occurs in Toxoplasma. Furthermore, we determined that about 500 gene transcripts showed enhanced association with translating ribosomes during ER stress. Many of these target genes are suggested to be involved in gene expression, including JmjC5, which continues to be actively translated during ER stress. This study indicates that Toxoplasma triggers a UPR during ER stress that features both translational and transcriptional regulatory mechanisms, which is likely to be important for parasite invasion and development.
PMID: 23666622 [PubMed - as supplied by publisher]
The Unfolded Protein Response in the protozoan parasite Toxoplasma gondii features translational and transcriptional control
Joyce BR, Tampaki Z, Kim K, Wek RC, Sullivan WJ Jr.
Department of Pharmacology & Toxicology
Indiana University School of Medicine
The Unfolded Protein Response (UPR) is an important regulatory network that responds to perturbations in protein homeostasis in the endoplasmic reticulum (ER). In mammalian cells, the UPR features translational and transcriptional mechanisms of gene expression aimed at restoring proteostatic control. A central feature of the UPR is phosphorylation of the α subunit of eIF2 by PERK (EIF2AK3/PEK), which reduces the influx of nascent proteins into the ER by lowering global protein synthesis, coincident with preferential translation of key transcription activators of genes that function to expand the processing capacity of this secretory organelle. Upon ER stress, the apicomplexan parasite Toxoplasma gondii is known to induce phosphorylation of Toxoplasma eIF2α and lower translation initiation. To characterize the nature of the ensuing UPR in this parasite, we carried out microarray analyses to measure the changes in the transcriptome and in translational control during ER stress. We determined that a collection of transcripts linked with the secretory process are induced in response to ER stress, supporting the idea that a transcriptional induction phase of the UPR occurs in Toxoplasma. Furthermore, we determined that about 500 gene transcripts showed enhanced association with translating ribosomes during ER stress. Many of these target genes are suggested to be involved in gene expression, including JmjC5, which continues to be actively translated during ER stress. This study indicates that Toxoplasma triggers a UPR during ER stress that features both translational and transcriptional regulatory mechanisms, which is likely to be important for parasite invasion and development.
PMID: 23666622 [PubMed - as supplied by publisher]
IL-21 Is Required for Optimal Antibody Production and T Cell Responses during Chronic Toxoplasma gondii Infection
PLoS One. 2013 May 7;8(5):e62889. doi: 10.1371/journal.pone.0062889. Print 2013.
IL-21 Is Required for Optimal Antibody Production and T Cell Responses during Chronic Toxoplasma gondii Infection
Stumhofer JS, Silver JS, Hunter CA.
Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America.
Previous studies have indicated that Il21r (-/-) mice chronically infected with Toxoplasma gondii display a defect in serum IgG; however, the basis for this antibody defect was not defined and questions remain about the role of IL-21 in promoting the production of IL-10, which is required to limit infection-induced pathology during toxoplasmosis. Therefore, Il21 (-/-) mice were challenged with T. gondii to determine whether IL-21 impacts the parasite-specific CD8(+) T cell response, its contribution to thymus-dependent antibody production after infection, and balance between protective and pathogenic responses. Whereas IL-21 has been implicated in the differentiation of IL-10 producing CD4(+) T cells no immune-mediated pathology was evident in Il21 (-/-) mice during the acute response, nor was there a defect in the development of this population in chronically infected Il21 (-/-) mice. However, Il21 (-/-) mice displayed a defect in IgG production after infection that correlated with a decrease in GC B cell numbers, the CD4(+) and CD8(+) T cell numbers in the brain were reduced over the course of the chronic infection leading to a decrease in total IFN-γ production and an increase in parasite numbers associated with susceptibility to toxoplasmic encephalitis. Together, these results identify a key role for IL-21 in shaping the humoral and cellular response to T. gondii, but indicate that IL-21 has a limited role in regulating immunopathology.
PMID: 23667536 [PubMed - in process]
IL-21 Is Required for Optimal Antibody Production and T Cell Responses during Chronic Toxoplasma gondii Infection
Stumhofer JS, Silver JS, Hunter CA.
Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America.
Previous studies have indicated that Il21r (-/-) mice chronically infected with Toxoplasma gondii display a defect in serum IgG; however, the basis for this antibody defect was not defined and questions remain about the role of IL-21 in promoting the production of IL-10, which is required to limit infection-induced pathology during toxoplasmosis. Therefore, Il21 (-/-) mice were challenged with T. gondii to determine whether IL-21 impacts the parasite-specific CD8(+) T cell response, its contribution to thymus-dependent antibody production after infection, and balance between protective and pathogenic responses. Whereas IL-21 has been implicated in the differentiation of IL-10 producing CD4(+) T cells no immune-mediated pathology was evident in Il21 (-/-) mice during the acute response, nor was there a defect in the development of this population in chronically infected Il21 (-/-) mice. However, Il21 (-/-) mice displayed a defect in IgG production after infection that correlated with a decrease in GC B cell numbers, the CD4(+) and CD8(+) T cell numbers in the brain were reduced over the course of the chronic infection leading to a decrease in total IFN-γ production and an increase in parasite numbers associated with susceptibility to toxoplasmic encephalitis. Together, these results identify a key role for IL-21 in shaping the humoral and cellular response to T. gondii, but indicate that IL-21 has a limited role in regulating immunopathology.
PMID: 23667536 [PubMed - in process]
Up-regulation of Matrix Metalloproteinases-2 and -9 via an Erk1/2/NF-κB Pathway in Murine Mast Cells Infected with Toxoplasma gondii
J Comp Pathol. 2013 May 7. pii: S0021-9975(13)00051-0. doi: 10.1016/j.jcpa.2013.03.002. [Epub ahead of print]
Up-regulation of Matrix Metalloproteinases-2 and -9 via an Erk1/2/NF-κB Pathway in Murine Mast Cells Infected with Toxoplasma gondii
Wang MF, Lu CY, Lai SC.
Institute of Medicine, Chung Shan Medical University, Taichung 402, Taiwan; Department of Pediatrics, Tungs' Taichung MetroHarbor Hospital, Taichung, Taiwan
Mast cells are key effectors in inflammation and contain proteinases that are released on activation. This study investigates associations between extracellular signal-regulated kinase (Erk)1/2, nuclear factor (NF)-κB, matrix metalloproteinase (MMP)-2 and MMP-9 in mast cells infected with Toxoplasma gondii tachyzoites. T. gondii infection led to increased mast cell degranulation. Phosphorylated (p)-Erk1/2 and p-NF-κB were increased significantly in mast cells infected with T. gondii. Pretreatment with the Erk kinase inhibitor PD98059 significantly decreased the expression of p-Erk1/2, p-NF-κB, MMP-2 and MMP-9. Treatment with MG132, an indirect NF-κB inhibitor, effectively reduced p-IκBα, p-NF-κB, MMP-2 and MMP-9 expression. Collectively, these data show that suppression of an Erk1/2/NF-κB signalling pathway caused a reduction in MMP-2 and -9 activities. Inhibiting this signalling pathway for MMP-2 and MMP-9 expression might offer a potential way to control early T. gondii infection. This pathway for the generation of MMP-2 and MMP-9 is important for mast cell secretion and the NF-κB/Erk1/2 signalling pathway may be key in MMP-2 and MMP-9 production in host defense against toxoplasmosis.
PMID: 23664424 [PubMed - as supplied by publisher]
Up-regulation of Matrix Metalloproteinases-2 and -9 via an Erk1/2/NF-κB Pathway in Murine Mast Cells Infected with Toxoplasma gondii
Wang MF, Lu CY, Lai SC.
Institute of Medicine, Chung Shan Medical University, Taichung 402, Taiwan; Department of Pediatrics, Tungs' Taichung MetroHarbor Hospital, Taichung, Taiwan
Mast cells are key effectors in inflammation and contain proteinases that are released on activation. This study investigates associations between extracellular signal-regulated kinase (Erk)1/2, nuclear factor (NF)-κB, matrix metalloproteinase (MMP)-2 and MMP-9 in mast cells infected with Toxoplasma gondii tachyzoites. T. gondii infection led to increased mast cell degranulation. Phosphorylated (p)-Erk1/2 and p-NF-κB were increased significantly in mast cells infected with T. gondii. Pretreatment with the Erk kinase inhibitor PD98059 significantly decreased the expression of p-Erk1/2, p-NF-κB, MMP-2 and MMP-9. Treatment with MG132, an indirect NF-κB inhibitor, effectively reduced p-IκBα, p-NF-κB, MMP-2 and MMP-9 expression. Collectively, these data show that suppression of an Erk1/2/NF-κB signalling pathway caused a reduction in MMP-2 and -9 activities. Inhibiting this signalling pathway for MMP-2 and MMP-9 expression might offer a potential way to control early T. gondii infection. This pathway for the generation of MMP-2 and MMP-9 is important for mast cell secretion and the NF-κB/Erk1/2 signalling pathway may be key in MMP-2 and MMP-9 production in host defense against toxoplasmosis.
PMID: 23664424 [PubMed - as supplied by publisher]
In vitro evaluation of beta-carboline alkaloids as potential anti-Toxoplasma agents
BMC Res Notes. 2013 May 10;6(1):193. [Epub ahead of print]
In vitro evaluation of beta-carboline alkaloids as potential anti-Toxoplasma agents
Alomar ML, Rasse-Suriani FA, Ganuza A, Cóceres VM, Cabrerizo FM, Angel SO.
BACKGROUND:
Toxoplasmosis is a worldwide infection caused by the protozoan parasite Toxoplasma gondii, which causes chorioretinitis and neurological defects in congenitally infected newborns or immunodeficient patients. The efficacy of the current treatment is limited, primarily by serious host toxicity. In recent years, research has focused on the development of new drugs against T. gondii. beta-Carbolines (betaCs), such as harmane, norharmane and harmine, are a group of naturally occurring alkaloids that show microbicidal activity. In this work, harmane, norharmane and harmine were tested against T. gondii.
FINDINGS:
The treatment of extracellular tachyzoites with harmane, norharmane and harmine showed a 2.5 to 3.5-fold decrease in the invasion rates at doses of 40 muM (harmane and harmine) and 2.5 muM (norharmane) compared with the untreated parasites. Furthermore, an effect on the replication rate could also be observed with a decrease of 1 (harmane) and 2 (norharmane and harmine) division rounds at doses of 5 to 12.5 muM. In addition, the treated parasites presented either delayed or no monolayer lysis compared with the untreated parasites.
CONCLUSIONS:
The three betaC alkaloids studied (norharmane, harmane and harmine) exhibit anti-T. gondii effects as evidenced by the partial inhibition of parasite invasion and replication. A dose--response effect was observed at a relatively low drug concentration (< 40 muM), at which no cytotoxic effect was observed on the host cell line (Vero).
PMID: 23663567 [PubMed - as supplied by publisher]
In vitro evaluation of beta-carboline alkaloids as potential anti-Toxoplasma agents
Alomar ML, Rasse-Suriani FA, Ganuza A, Cóceres VM, Cabrerizo FM, Angel SO.
BACKGROUND:
Toxoplasmosis is a worldwide infection caused by the protozoan parasite Toxoplasma gondii, which causes chorioretinitis and neurological defects in congenitally infected newborns or immunodeficient patients. The efficacy of the current treatment is limited, primarily by serious host toxicity. In recent years, research has focused on the development of new drugs against T. gondii. beta-Carbolines (betaCs), such as harmane, norharmane and harmine, are a group of naturally occurring alkaloids that show microbicidal activity. In this work, harmane, norharmane and harmine were tested against T. gondii.
FINDINGS:
The treatment of extracellular tachyzoites with harmane, norharmane and harmine showed a 2.5 to 3.5-fold decrease in the invasion rates at doses of 40 muM (harmane and harmine) and 2.5 muM (norharmane) compared with the untreated parasites. Furthermore, an effect on the replication rate could also be observed with a decrease of 1 (harmane) and 2 (norharmane and harmine) division rounds at doses of 5 to 12.5 muM. In addition, the treated parasites presented either delayed or no monolayer lysis compared with the untreated parasites.
CONCLUSIONS:
The three betaC alkaloids studied (norharmane, harmane and harmine) exhibit anti-T. gondii effects as evidenced by the partial inhibition of parasite invasion and replication. A dose--response effect was observed at a relatively low drug concentration (< 40 muM), at which no cytotoxic effect was observed on the host cell line (Vero).
PMID: 23663567 [PubMed - as supplied by publisher]
Saturday, May 11, 2013
A nucleotide sugar transporter involved in glycosylation of the toxoplasma tissue cyst wall is required for efficient persistence of bradyzoites
PLoS Pathog. 2013 May;9(5):e1003331. doi: 10.1371/journal.ppat.1003331. Epub 2013 May 2.
A nucleotide sugar transporter involved in glycosylation of the toxoplasma tissue cyst wall is required for efficient persistence of bradyzoites
Caffaro CE, Koshy AA, Liu L, Zeiner GM, Hirschberg CB, Boothroyd JC.
Department of Microbiology & Immunology, Stanford University School of Medicine, Stanford, California, United States of America.
Toxoplasma gondii is an intracellular parasite that transitions from acute infection to a chronic infective state in its intermediate host via encystation, which enables the parasite to evade immune detection and clearance. It is widely accepted that the tissue cyst perimeter is highly and specifically decorated with glycan modifications; however, the role of these modifications in the establishment and persistence of chronic infection has not been investigated. Here we identify and biochemically and biologically characterize a Toxoplasma nucleotide-sugar transporter (TgNST1) that is required for cyst wall glycosylation. Toxoplasma strains deleted for the TgNST1 gene (Δnst1) form cyst-like structures in vitro but no longer interact with lectins, suggesting that Δnst1 strains are deficient in the transport and use of sugars for the biosynthesis of cyst-wall structures. In vivo infection experiments demonstrate that the lack of TgNST1 activity does not detectably impact the acute (tachyzoite) stages of an infection or tropism of the parasite for the brain but that Δnst1 parasites are severely defective in persistence during the chronic stages of the infection. These results demonstrate for the first time the critical role of parasite glycoconjugates in the persistence of Toxoplasma tissue cysts.
PMID: 23658519 [PubMed - in process]
A nucleotide sugar transporter involved in glycosylation of the toxoplasma tissue cyst wall is required for efficient persistence of bradyzoites
Caffaro CE, Koshy AA, Liu L, Zeiner GM, Hirschberg CB, Boothroyd JC.
Department of Microbiology & Immunology, Stanford University School of Medicine, Stanford, California, United States of America.
Toxoplasma gondii is an intracellular parasite that transitions from acute infection to a chronic infective state in its intermediate host via encystation, which enables the parasite to evade immune detection and clearance. It is widely accepted that the tissue cyst perimeter is highly and specifically decorated with glycan modifications; however, the role of these modifications in the establishment and persistence of chronic infection has not been investigated. Here we identify and biochemically and biologically characterize a Toxoplasma nucleotide-sugar transporter (TgNST1) that is required for cyst wall glycosylation. Toxoplasma strains deleted for the TgNST1 gene (Δnst1) form cyst-like structures in vitro but no longer interact with lectins, suggesting that Δnst1 strains are deficient in the transport and use of sugars for the biosynthesis of cyst-wall structures. In vivo infection experiments demonstrate that the lack of TgNST1 activity does not detectably impact the acute (tachyzoite) stages of an infection or tropism of the parasite for the brain but that Δnst1 parasites are severely defective in persistence during the chronic stages of the infection. These results demonstrate for the first time the critical role of parasite glycoconjugates in the persistence of Toxoplasma tissue cysts.
PMID: 23658519 [PubMed - in process]
Thursday, May 09, 2013
Toxoplasma gondii cathepsin proteases are undeveloped prominent vaccine antigens against toxoplasmosis
BMC Infect Dis. 2013 May 7;13(1):207. [Epub ahead of print]
Toxoplasma gondii cathepsin proteases are undeveloped prominent vaccine antigens against toxoplasmosis
Zhao G, Zhou A, Lv G, Meng M, Sun M, Bai Y, Han Y, Wang L, Zhou H, Cong H, Zhao Q, Zhu X, He S.
BACKGROUND:
Toxoplasma gondii, an obligate intracellular apicomplexan parasite, infects a wide range of warm-blooded animals including humans. T. gondii expresses five members of the C1 family of cysteine proteases, including cathepsin B-like (TgCPB) and cathepsin L-like (TgCPL) proteins. TgCPB is involved in ROP protein maturation and parasite invasion, whereas TgCPL contributes to proteolytic maturation of proTgM2AP and proTgMIC3. TgCPL is also associated with the residual body in the parasitophorous vacuole after cell division has occurred. Both of these proteases are potential therapeutic targets in T. gondii. The aim of this study was to investigate TgCPB and TgCPL for their potential as DNA vaccines against T. gondii.
METHODS:
Using bioinformatics approaches, we analyzed TgCPB and TgCPL proteins and identified several linear-B cell epitopes and potential Th-cell epitopes in them. Based on these results, we assembled two single-gene constructs (TgCPB and TgCPL) and a multi-gene construct (pTgCPB/TgCPL) with which to immunize BALB/c mice and test their effectiveness as DNA vaccines.
RESULTS:
TgCPB and TgCPL vaccines elicited strong humoral and cellular immune responses in mice, both of which were Th-1 cell mediated. In addition, all of the vaccines protected the mice against infection with virulent T. gondii RH tachyzoites, with the multi-gene vaccine (pTgCPB/TgCPL) providing the highest level of protection.
CONCLUSIONS:
T. gondii CPB and CPL proteases are strong candidates for development as novel DNA vaccines.
PMID: 23651838 [PubMed - as supplied by publisher]
Toxoplasma gondii cathepsin proteases are undeveloped prominent vaccine antigens against toxoplasmosis
Zhao G, Zhou A, Lv G, Meng M, Sun M, Bai Y, Han Y, Wang L, Zhou H, Cong H, Zhao Q, Zhu X, He S.
BACKGROUND:
Toxoplasma gondii, an obligate intracellular apicomplexan parasite, infects a wide range of warm-blooded animals including humans. T. gondii expresses five members of the C1 family of cysteine proteases, including cathepsin B-like (TgCPB) and cathepsin L-like (TgCPL) proteins. TgCPB is involved in ROP protein maturation and parasite invasion, whereas TgCPL contributes to proteolytic maturation of proTgM2AP and proTgMIC3. TgCPL is also associated with the residual body in the parasitophorous vacuole after cell division has occurred. Both of these proteases are potential therapeutic targets in T. gondii. The aim of this study was to investigate TgCPB and TgCPL for their potential as DNA vaccines against T. gondii.
METHODS:
Using bioinformatics approaches, we analyzed TgCPB and TgCPL proteins and identified several linear-B cell epitopes and potential Th-cell epitopes in them. Based on these results, we assembled two single-gene constructs (TgCPB and TgCPL) and a multi-gene construct (pTgCPB/TgCPL) with which to immunize BALB/c mice and test their effectiveness as DNA vaccines.
RESULTS:
TgCPB and TgCPL vaccines elicited strong humoral and cellular immune responses in mice, both of which were Th-1 cell mediated. In addition, all of the vaccines protected the mice against infection with virulent T. gondii RH tachyzoites, with the multi-gene vaccine (pTgCPB/TgCPL) providing the highest level of protection.
CONCLUSIONS:
T. gondii CPB and CPL proteases are strong candidates for development as novel DNA vaccines.
PMID: 23651838 [PubMed - as supplied by publisher]
Wednesday, May 08, 2013
Motile invaded neutrophils in the small intestine of Toxoplasma gondii-infected mice reveal a potential mechanism for parasite spread
Proc Natl Acad Sci U S A. 2013 May 6. [Epub ahead of print]
Motile invaded neutrophils in the small intestine of Toxoplasma gondii-infected mice reveal a potential mechanism for parasite spread
Coombes JL, Charsar BA, Han SJ, Halkias J, Chan SW, Koshy AA, Striepen B, Robey EA.
Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720.
Toxoplasma gondii infection occurs through the oral route, but we lack important information about how the parasite interacts with the host immune system in the intestine. We used two-photon laser-scanning microscopy in conjunction with a mouse model of oral T. gondii infection to address this issue. T. gondii established discrete foci of infection in the small intestine, eliciting the recruitment and transepithelial migration of neutrophils and inflammatory monocytes. Neutrophils accounted for a high proportion of actively invaded cells, and we provide evidence for a role for transmigrating neutrophils and other immune cells in the spread of T. gondii infection through the lumen of the intestine. Our data identify neutrophils as motile reservoirs of T. gondii infection and suggest a surprising retrograde pathway for parasite spread in the intestine.
PMID: 23650399 [PubMed - as supplied by publisher]
Motile invaded neutrophils in the small intestine of Toxoplasma gondii-infected mice reveal a potential mechanism for parasite spread
Coombes JL, Charsar BA, Han SJ, Halkias J, Chan SW, Koshy AA, Striepen B, Robey EA.
Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720.
Toxoplasma gondii infection occurs through the oral route, but we lack important information about how the parasite interacts with the host immune system in the intestine. We used two-photon laser-scanning microscopy in conjunction with a mouse model of oral T. gondii infection to address this issue. T. gondii established discrete foci of infection in the small intestine, eliciting the recruitment and transepithelial migration of neutrophils and inflammatory monocytes. Neutrophils accounted for a high proportion of actively invaded cells, and we provide evidence for a role for transmigrating neutrophils and other immune cells in the spread of T. gondii infection through the lumen of the intestine. Our data identify neutrophils as motile reservoirs of T. gondii infection and suggest a surprising retrograde pathway for parasite spread in the intestine.
PMID: 23650399 [PubMed - as supplied by publisher]
Hepatic stellate cells increase in Toxoplasma gondii infection in mice
Parasit Vectors. 2013 May 4;6(1):135. [Epub ahead of print]
Hepatic stellate cells increase in Toxoplasma gondii infection in mice
Atmaca HT, Gazya C AN, Canpolat SL, Kul OU.
BACKGROUND:
Toxoplasma gondii is a ubiquitous protozoan parasite that can infect humans and animals. The severity of toxoplasmosis varies according to the immune status of the individual, parasite strain, and host species. In mammalian species, it has been observed that severe lesions of acute toxoplasmosis form in visceral organs such as the liver, lung, and spleen. Some epidemiological studies have reported an association of T. gondii infection with liver cirrhosis.
METHODS:
Acute infection was induced in fifteen 30-day-old normal Swiss albino mice. The mice were infected by intraperitoneal inoculation of 5000 T. gondii RH strain tachyzoites. The mice were sacrificed in groups of 5 at 2, 4, and 6 days after inoculation. Another group of 5 mice were used as the controls. Anti-glial fibrillary acidic protein (GFAP) and anti-T. gondii antibodies were used to compare GFAP-immunoreactive cells and anti-T. gondii--immunopositive areas in the liver between the T. gondii-infected groups and the healthy controls, respectively.
RESULTS:
There was a significant correlation between the numbers of GFAP-positive hepatic stellate cells (HSCs) when they were compared with T. gondii antigen immunostaining (p < 0.05). The amount of T. gondii immunostaining increased significantly with the increase in the number of HSCs.
CONCLUSIONS:
There is a significant relationship between the number of HSCs and T. gondii antigens, which may represent an active role of HSCs in liver pathology and the pathobiology of T. gondii-related hepatitis.
PMID: 23642259 [PubMed - as supplied by publisher]
Hepatic stellate cells increase in Toxoplasma gondii infection in mice
Atmaca HT, Gazya C AN, Canpolat SL, Kul OU.
BACKGROUND:
Toxoplasma gondii is a ubiquitous protozoan parasite that can infect humans and animals. The severity of toxoplasmosis varies according to the immune status of the individual, parasite strain, and host species. In mammalian species, it has been observed that severe lesions of acute toxoplasmosis form in visceral organs such as the liver, lung, and spleen. Some epidemiological studies have reported an association of T. gondii infection with liver cirrhosis.
METHODS:
Acute infection was induced in fifteen 30-day-old normal Swiss albino mice. The mice were infected by intraperitoneal inoculation of 5000 T. gondii RH strain tachyzoites. The mice were sacrificed in groups of 5 at 2, 4, and 6 days after inoculation. Another group of 5 mice were used as the controls. Anti-glial fibrillary acidic protein (GFAP) and anti-T. gondii antibodies were used to compare GFAP-immunoreactive cells and anti-T. gondii--immunopositive areas in the liver between the T. gondii-infected groups and the healthy controls, respectively.
RESULTS:
There was a significant correlation between the numbers of GFAP-positive hepatic stellate cells (HSCs) when they were compared with T. gondii antigen immunostaining (p < 0.05). The amount of T. gondii immunostaining increased significantly with the increase in the number of HSCs.
CONCLUSIONS:
There is a significant relationship between the number of HSCs and T. gondii antigens, which may represent an active role of HSCs in liver pathology and the pathobiology of T. gondii-related hepatitis.
PMID: 23642259 [PubMed - as supplied by publisher]
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