toxplasma news feeds

Dual role of the Toxoplasma gondii clathrin adaptor AP1 in the sorting of rhoptry and microneme proteins and in parasite division

The Anti-Toxo Blog - 22 April 2017 - 2:45pm
 2017 Apr 21;13(4):e1006331. doi: 10.1371/journal.ppat.1006331. [Epub ahead of print]
Venugopal K1, Werkmeister E1, Barois N1, Saliou JM1, Poncet A1, Huot L1, Sindikubwabo F2, Hakimi MA2, Langsley G3, Lafont F1, Marion S1.AbstractToxoplasma gondii possesses a highly polarized secretory system, which efficiently assembles de novo micronemes and rhoptries during parasite replication. These apical secretory organelles release their contents into host cells promoting parasite invasion and survival. Using a CreLox-based inducible knock-out strategy and the ddFKBP over-expression system, we unraveled novel functions of the clathrin adaptor complex TgAP1. First, our data indicate that AP1 in T. gondii likely functions as a conserved heterotetrameric complex composed of the four subunits γ, β, μ1, σ1 and interacts with known regulators of clathrin-mediated vesicular budding such as the unique ENTH-domain containing protein, which we named Epsin-like protein (TgEpsL). Disruption of the μ1 subunit resulted in the mis-sorting of microneme proteins at the level of the Trans-Golgi-Network (TGN). Furthermore, we demonstrated that TgAP1 regulates rhoptry biogenesis by activating rhoptry protein exit from the TGN, but also participates in the post-Golgi maturation process of preROP compartments into apically anchored club-shaped mature organelles. For this latter activity, our data indicate a specific functional relationship between TgAP1 and the Rab5A-positive endosome-like compartment. In addition, we unraveled an original role for TgAP1 in the regulation of parasite division. APμ1-depleted parasites undergo normal daughter cell budding and basal complex assembly but fail to segregate at the end of cytokinesis.
PMID:
 
28430827
 
DOI:
 
10.1371/journal.ppat.1006331
Categories: toxoplasma news feeds

CD103+ CD8 T Cells in the Toxoplasma-Infected Brain Exhibit a Tissue-Resident Memory Transcriptional Profile

The Anti-Toxo Blog - 21 April 2017 - 12:37pm
2017 Mar 29;8:335. doi: 10.3389/fimmu.2017.00335. eCollection 2017.
Landrith TA1, Sureshchandra S1, Rivera A1, Jang JC1, Rais M1, Nair MG1, Messaoudi I1, Wilson EH1.
During chronic infection, memory T cells acquire a unique phenotype and become dependent on different survival signals than those needed for memory T cells generated during an acute infection. The distinction between the role of effector and memory T cells in an environment of persistent antigen remains unclear. Here, in the context of chronic Toxoplasma gondii infection, we demonstrate that a population of CD8 T cells exhibiting a tissue-resident memory (TRM) phenotype accumulates within the brain. We show that this population is distributed throughout the brain in both parenchymal and extraparenchymal spaces. Furthermore, this population is transcriptionally distinct and exhibits a transcriptional signature consistent with the TRM observed in acute viral infections. Finally, we establish that the CD103+ TRM population has an intrinsic capacity to produce both IFN-γ and TNF-α, cytokines critical for parasite control within the central nervous system (CNS). The contribution of this population to pro-inflammatory cytokine production suggests an important role for TRM in protective and ongoing immune responses in the infected CNS. Accession number: GSE95105.KEYWORDS: CD103; CD8+ T cell memory; Toxoplasma gondii; chronic infection; neuroimmunology; tissue-resident memory cells
PMID:
28424687
PMCID:
PMC5372813
DOI:
10.3389/fimmu.2017.00335
Categories: toxoplasma news feeds

TgPL2, a patatin-like phospholipase domain-containing protein, is involved in the maintenance of apicoplast lipids homeostasis in Toxoplasma

The Anti-Toxo Blog - 19 April 2017 - 12:33pm

2017 Apr 17. doi: 10.1111/mmi.13694. [Epub ahead of print]
Lévêque MF1, Berry L1, Yamaryo-Botté Y2, Nguyen HM1, Galera M2, Botté CY2, Besteiro S1.
Patatin-like phospholipases are involved in numerous cellular functions, including lipid metabolism and membranes remodeling. The patatin-like catalytic domain, whose phospholipase activity relies on a serine-aspartate dyad and an anion binding box, is widely spread among prokaryotes and eukaryotes. We describe TgPL2, a novel patatin-like phospholipase domain-containing protein from the parasitic protist Toxoplasma gondii. TgPL2 is a large protein, in which the key motifs for enzymatic activity are conserved in the patatin-like domain. Using immunofluorescent assays and immunoelectron microscopy analysis, we have shown that TgPL2 localizes to the apicoplast, a non-photosynthetic plastid found in most apicomplexan parasites. This plastid hosts several important biosynthetic pathways, which makes it an attractive organelle for identifying new potential drug targets. We thus addressed TgPL2 function by generating a conditional knockdown mutant and demonstrated it has an essential contribution for maintaining the integrity of the plastid. In absence of TgPL2, the organelle is rapidly lost and remaining apicoplasts appear enlarged, with an abnormal accumulation of membranous structures, suggesting a defect in lipids homeostasis. More precisely, analyses of lipid content upon TgPL2 depletion suggest this protein is important for maintaining levels of apicoplast-generated fatty acids, and also regulating phosphatidylcholine and lysophosphatidylcholine levels in the parasite. This article is protected by copyright. All rights reserved.
© 2017 John Wiley & Sons Ltd.KEYWORDS: Apicomplexa; Toxoplasma; apicoplast; lipids; patatin; phospholipase
PMID:
28419631
DOI:
10.1111/mmi.13694
Categories: toxoplasma news feeds

Intestinal, extra-intestinal and systemic sequelae of Toxoplasma gondii induced acute ileitis in mice harboring a human gut microbiota

The Anti-Toxo Blog - 18 April 2017 - 12:30pm

2017 Apr 17;12(4):e0176144. doi: 10.1371/journal.pone.0176144. eCollection 2017.
von Klitzing E1, Ekmekciu I1, Kühl AA2, Bereswill S1, Heimesaat MM1.
BACKGROUND: Within seven days following peroral high dose infection with Toxoplasma gondii susceptible conventionally colonized mice develop acute ileitis due to an underlying T helper cell (Th) -1 type immunopathology. We here addressed whether mice harboring a human intestinal microbiota developed intestinal, extra-intestinal and systemic sequelae upon ileitis induction.
METHODOLOGY/PRINCIPAL FINDINGS: Secondary abiotic mice were generated by broad-spectrum antibiotic treatment and associated with a complex human intestinal microbiota following peroral fecal microbiota transplantation. Within three weeks the human microbiota had stably established in the murine intestinal tract as assessed by quantitative cultural and culture-independent (i.e. molecular 16S rRNA based) methods. At day 7 post infection (p.i.) with 50 cysts of T. gondii strain ME49 by gavage human microbiota associated (hma) mice displayed severe clinical, macroscopic and microscopic sequelae indicating acute ileitis. In diseased hma mice increased numbers of innate and adaptive immune cells within the ileal mucosa and lamina propria and elevated intestinal secretion of pro-inflammatory mediators including IFN-γ, IL-12 and nitric oxide could be observed at day 7 p.i. Ileitis development was accompanied by substantial shifts in intestinal microbiota composition of hma mice characterized by elevated total bacterial loads and increased numbers of intestinal Gram-negative commensals such as enterobacteria and Bacteroides / Prevotella species overgrowing the small and large intestinal lumen. Furthermore, viable bacteria translocated from the inflamed ileum to extra-intestinal including systemic compartments. Notably, pro-inflammatory immune responses were not restricted to the intestinal tract as indicated by increased pro-inflammatory cytokine secretion in extra-intestinal (i.e. liver and kidney) and systemic compartments including spleen and serum.
CONCLUSION/SIGNIFICANCE: With respect to the intestinal microbiota composition "humanized" mice display acute ileitis following peroral high dose T. gondii infection. Thus, hma mice constitute a suitable model to further dissect the interactions between pathogens, human microbiota and vertebrate host immunity during acute intestinal inflammation.
PMID:
28414794
DOI:
10.1371/journal.pone.0176144
Categories: toxoplasma news feeds

Apicomplexan autophagy and modulation of autophagy in parasite-infected host cells

The Anti-Toxo Blog - 17 April 2017 - 3:39pm


2017 Feb;40(1):23-30. doi: 10.1016/j.bj.2017.01.001. Epub 2017 Mar 23.

Laté de Laté P1, Pineda M2, Harnett M3, Harnett W4, Besteiro S5, Langsley G6.


Apicomplexan parasites are responsible for a number of important human pathologies. Obviously, as Eukaryotes they share a number of cellular features and pathways with their respective host cells. One of them is autophagy, a process involved in the degradation of the cell's own components. These intracellular parasites nonetheless seem to present a number of original features compared to their very evolutionarily distant host cells. In mammals and other metazoans, autophagy has been identified as an important contributor to the defence against microbial pathogens. Thus, host autophagy also likely plays a key role in the control of apicomplexan parasites, although its potential manipulation and subversion by intracellular parasites creates a complex interplay in the regulation of host and parasite autophagy. In this mini-review, we summarise current knowledge on autophagy in both parasites and their host cells, in the context of infection by three Apicomplexa: Plasmodium, Toxoplasma, and Theileria.
Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.KEYWORDS: Autophagy; Cell signalling; Host cell; Plasmodium; Theileria; Toxoplasma
PMID:
28411879
DOI:
10.1016/j.bj.2017.01.001
Categories: toxoplasma news feeds

Protection induced by virus-like particles containing Toxoplasma gondii microneme protein 8 against highly virulent RH strain of Toxoplasma gondii infection

The Anti-Toxo Blog - 14 April 2017 - 12:46pm
2017 Apr 13;12(4):e0175644. doi: 10.1371/journal.pone.0175644. eCollection 2017.
Lee SH1, Kim AR1, Lee DH1, Rubino I2, Choi HJ2, Quan FS3.
Toxoplasma gondii (T. gondii) microneme protein 8 (MIC8) represents a novel, functional distinct invasion factor. In this study, we generated virus-like particles (VLPs) targeting Toxoplasma gondii MIC8 for the first time, and investigated the protection against highly virulent RH strain of T. gondii in a mouse model. We found that VLP vaccination induced Toxoplasma gondii-specific IgG and IgG1 antibody responses in the sera. Upon challenge infection with RH strain of T. gondii tachyzoites, vaccinated mice showed a significant increase of both IgG antibodies in sera and IgA antibodies in feces compared to those before challenge, and a rapid expansion of both germinal center B cell (B220+, GL7+) and T cell (CD4+, CD8+) populations. Importantly, intranasally immunized mice showed higher neutralizing antibodies and displayed no proinflammatory cytokine IFN-γ in the spleen. Mice were completely protected from a lethal challenge infection with the highly virulent T. gondii (RH) showing no body weight loss (100% survival). Our study shows the effective protection against T. gondii infection provided by VLPs containing microneme protein 8 of T. gondii, thus indicating a potential T. gondii vaccine candidate.
PMID:
28406951
DOI:
10.1371/journal.pone.0175644
Categories: toxoplasma news feeds

Disruption of outer blood-retinal barrier by Toxoplasma gondii-infected monocytes is mediated by paracrinely activated FAK signaling

The Anti-Toxo Blog - 14 April 2017 - 12:46pm
2017 Apr 13;12(4):e0175159. doi: 10.1371/journal.pone.0175159. eCollection 2017.
Song HB1,2,3, Jun HO1, Kim JH1, Lee YH4, Choi MH3, Kim JH1,2,5.
Ocular toxoplasmosis is mediated by monocytes infected with Toxoplasma gondii that are disseminated to target organs. Although infected monocytes can easily access to outer blood-retinal barrier due to leaky choroidal vasculatures, not much is known about the effect of T. gondii-infected monocytes on outer blood-retinal barrier. We prepared human monocytes, THP-1, infected with T. gondii and human retinal pigment epithelial cells, ARPE-19, grown on transwells as an in vitro model of outer blood-retinal barrier. Exposure to infected monocytes resulted in disruption of tight junction protein, ZO-1, and decrease in transepithelial electrical resistance of retinal pigment epithelium. Supernatants alone separated from infected monocytes also decreased transepithelial electrical resistance and disrupted tight junction protein. Further investigation revealed that the supernatants could activate focal adhesion kinase (FAK) signaling in retinal pigment epithelium and the disruption was attenuated by FAK inhibitor. The disrupted barrier was partly restored by blocking CXCL8, a FAK activating factor secreted by infected monocytes. In this study, we demonstrated that monocytes infected with T. gondii can disrupt outer blood-retinal barrier, which is mediated by paracrinely activated FAK signaling. FAK signaling can be a target of therapeutic approach to prevent negative influence of infected monocytes on outer blood-retinal barrier.
PMID:
28406972
DOI:
10.1371/journal.pone.0175159
Categories: toxoplasma news feeds

Toxoplasma Effectors Targeting Host Signaling and Transcription

The Anti-Toxo Blog - 14 April 2017 - 12:45pm
2017 Jul;30(3):615-645. doi: 10.1128/CMR.00005-17.
Hakimi MA1, Olias P2,3, Sibley LD4.
Early electron microscopy studies revealed the elaborate cellular features that define the unique adaptations of apicomplexan parasites. Among these were bulbous rhoptry (ROP) organelles and small, dense granules (GRAs), both of which are secreted during invasion of host cells. These early morphological studies were followed by the exploration of the cellular contents of these secretory organelles, revealing them to be comprised of highly divergent protein families with few conserved domains or predicted functions. In parallel, studies on host-pathogen interactions identified many host signaling pathways that were mysteriously altered by infection. It was only with the advent of forward and reverse genetic strategies that the connections between individual parasite effectors and the specific host pathways that they targeted finally became clear. The current repertoire of parasite effectors includes ROP kinases and pseudokinases that are secreted during invasion and that block host immune pathways. Similarly, many secretory GRA proteins alter host gene expression by activating host transcription factors, through modification of chromatin, or by inducing small noncoding RNAs. These effectors highlight novel mechanisms by which T. gondii has learned to harness host signaling to favor intracellular survival and will guide future studies designed to uncover the additional complexity of this intricate host-pathogen interaction.
Copyright © 2017 American Society for Microbiology.KEYWORDS: chromatin remodeling; epigenetics; immune evasion; innate immunity; intracellular pathogen; serine/threonine kinases; signal transduction; transcription factors
PMID:
28404792
DOI:
10.1128/CMR.00005-17
Categories: toxoplasma news feeds

Investigation of Toxoplasma gondii in semen, testicle and epididymis tissues of primo-infected cats

The Anti-Toxo Blog - 14 April 2017 - 12:44pm
2017 Apr 3. pii: S0304-4017(17)30136-X. doi: 10.1016/j.vetpar.2017.04.003. [Epub ahead of print]
Teixeira WF1, Tozato ME1, Pierucci JC1, Vital GP1, Cruz AC1, Lopes WD2, Cursino MS1, Joaquim SF1, Soares VE3, Langoni H1, Bresciani KD1, Costa AJ1.
This study aimed to investigate the presence of Toxoplasma gondii in semen, testicle and epididymis tissues of cats experimentally infected by this coccidium. A total of 12 male felines without a definite breed that were of reproductive age and serologically negative for T. gondii were selected and distributed to the following three experimental groups: GI, inoculated with 600 tissue cysts of the P strain of T. gondii (isolate III); GII, inoculated with 2×105 tachyzoites of the RH strain (isolate I); and GIII, not inoculated (control group). Prior to inoculation (day -7 and 0) and on post inoculation days (PIDs) 7, 14, 21, 28, 42, 56, and 70, all felines were subjected to assessments of anti-T. gondii IgG by indirect immunofluorescence (IIF) and assessments of parasitemia. Collection of semen (electroejaculation) was performed on the specified dates, followed by nested PCR and bioassays in mice to detect T. gondii. On PID 70, all 12 felines were orchiectomized, and the presence of the parasite in the testicles and epididymides was evaluated by nested PCR, murine bioassay, and histopathological and immunohistochemical analyses. All felines inoculated with T. gondii (GI and GII) seroconverted to the toxoplasmic infection after PID 14; on PID 7, seroconversion of three felines (P4, RH2 and RH4) could observed, and all exhibited detectable titers by PID 64. The GII felines exhibited greater serological titers compared with GI felines. The maximum serological titer (IgG) was observed in feline RH3 (titer 1024), while in other experimental felines, a maximum titer of 256 was detected. Parasitemic peaks were diagnosed in all felines of groups I and II from PIDs 7-42. A total of five parasitemic peaks were diagnosed in GI and nine in GII. In none of the experimental time points was the presence of T. gondii diagnosed in seminal samples collected from the felines or in the testicle or epididymis tissues collected from these animals. Thus, sexual transmission in domestic cats does not appear to be a major route of T. gondii infection, possibly demonstrating the tendency of this protozoan to develop a response directed to the formation and excretion of oocysts in the feces of these definite hosts, which act as its main route of perpetuation in the environment.
Copyright © 2017 Elsevier B.V. All rights reserved.KEYWORDS: Felines; PCR; Sexual transmission; Tachyzoites; Toxoplasmosis
PMID:
28404209
DOI:
10.1016/j.vetpar.2017.04.003
Categories: toxoplasma news feeds

Loss of predator aversion in female rats after Toxoplasma gondii infection is not dependent on ovarian steroids

The Anti-Toxo Blog - 14 April 2017 - 12:41pm
2017 Apr 8. pii: S0889-1591(17)30107-1. doi: 10.1016/j.bbi.2017.04.005. [Epub ahead of print]
Abdulai-Saiku S1, Vyas A2.
Toxoplasma gondii infection reduces aversion to cat odors in male rats. Relevant proximate mechanisms include interaction of gonadal testosterone and brain nonapeptide arginine-vasopressin. Both of these substrates are sexually dimorphic with preferential expression in males; suggesting either absence of behavioral change in females or mediation by analogous neuroendocrine substrates. Here we demonstrate that Toxoplasma gondii infection reduces aversion to cat odor in female rats. This change is not accompanied by altered steroid hormones; cannot be rescued by gonadal removal; and, does not depend on arginine-vasopressin. Thus behavioral change in males and female occur through non-analogous mechanisms that remain hitherto unknown.
Copyright © 2017. Published by Elsevier Inc.KEYWORDS: Apicomplexan parasites; Arginine vasopressin; Behavioral manipulation; Estrogen; Gender; Medial amygdala; Parasites; Progesterone; Testosterone
PMID:
28400143
DOI:
10.1016/j.bbi.2017.04.005
Categories: toxoplasma news feeds

Non-coding RNAs in Host-Pathogen Interactions: Subversion of Mammalian Cell Functions by Protozoan Parasites

The Anti-Toxo Blog - 10 April 2017 - 3:24pm
 2017 Mar 21;8:474. doi: 10.3389/fmicb.2017.00474. eCollection 2017.
Bayer-Santos E1, Marini MM2, da Silveira JF2.AbstractPathogens have evolved mechanisms to modulate host cell functions and avoid recognition and destruction by the host damage response. For many years, researchers have focused on proteins as the main effectors used by pathogens to hijack host cell pathways, but only recently with the development of deep RNA sequencing these molecules were brought to light as key players in infectious diseases. Protozoan parasites such as those from the genera PlasmodiumToxoplasmaLeishmania, and Trypanosomacause life-threatening diseases and are responsible for 1000s of deaths worldwide every year. Some of these parasites replicate intracellularly when infecting mammalian hosts, whereas others can survive and replicate extracellularly in the bloodstream. Each of these parasites uses specific evasion mechanisms to avoid being killed by the host defense system. An increasing number of studies have shown that these pathogens can transfer non-coding RNA molecules to the host cells to modulate their functions. This transference usually happens via extracellular vesicles, which are small membrane vesicles secreted by the microorganism. In this mini-review we will combine published work regarding several protozoan parasites that were shown to use non-coding RNAs in inter-kingdom communication and briefly discuss future perspectives in the field.KEYWORDS: extracellular vesicles; infection; miRNA; non-coding RNA; parasitic diseases; protozoan parasites
PMID:
 
28377760
 
PMCID:
 
PMC5359270
 
DOI:
 
10.3389/fmicb.2017.00474
Categories: toxoplasma news feeds

From Toxoplasmosis to Schizophrenia via NMDA Dysfunction: Peptide Overlap between Toxoplasma gondii and N-Methyl-d-Aspartate Receptors As a Potential Mechanistic Link

The Anti-Toxo Blog - 10 April 2017 - 3:23pm
 2017 Mar 15;8:37. doi: 10.3389/fpsyt.2017.00037. eCollection 2017.
Lucchese G1.AbstractThe present work aims at investigating how Toxoplasma gondii (T. gondii) infection may be linked to N-methyl-d-aspartate receptor (NMDAR) dysfunction in schizophrenia and related disorders and puts forward the hypothesis that immune responses against T. gondii may involve NMDARs. Indeed, the analysis of the protozoan proteome and NMDAR subunits for peptide commonalities shows a massive peptide overlap and supports the possibility that anti-T. gondii immune responses raised during active protozoan infection may cross-react with host NMDARs, determining disruption of neural circuits and cognitive deficits. In particular, the NMDA 2D subunit, which is mainly expressed in parvalbumin-positive interneurons, appears to be a hotspot for potential T. gondii-induced cross-reactive immune attacks.KEYWORDS: N-methyl-d-aspartate receptors; NMDA 2D; Toxoplasma gondii; gamma oscillations; immune cross-reactivity; parvalbumin-positive interneurons; peptide commonality; schizophrenia
PMID:
 
28360866
 
PMCID:
 
PMC5350139
 
DOI:
 
10.3389/fpsyt.2017.00037
Categories: toxoplasma news feeds

An in vitro model of intestinal infection reveals a developmentally regulated transcriptome of Toxoplasma sporozoites and a NF-κB-like signature in infected host cells

The Anti-Toxo Blog - 10 April 2017 - 3:22pm
 2017 Mar 31;12(3):e0173018. doi: 10.1371/journal.pone.0173018. eCollection 2017.
Guiton PS1, Sagawa JM2, Fritz HM2, Boothroyd JC1.AbstractToxoplasmosis is a zoonotic infection affecting approximately 30% of the world's human population. After sexual reproduction in the definitive feline host, Toxoplasma oocysts, each containing 8 sporozoites, are shed into the environment where they can go on to infect humans and other warm-blooded intermediate hosts. Here, we use an in vitro model to assess host transcriptomic changes that occur in the earliest stages of such infections. We show that infection of rat intestinal epithelial cells with mature sporozoites primarily results in higher expression of genes associated with Tumor Necrosis Factor alpha (TNFα) signaling via NF-κB. Furthermore, we find that, consistent with their biology, these mature, invaded sporozoites display a transcriptome intermediate between the previously reported day 10 oocysts and that of their tachyzoite counterparts. Thus, this study uncovers novel host and pathogen factors that may be critical for the establishment of a successful intracellular niche following sporozoite-initiated infection.
PMID:
 
28362800
 
PMCID:
 
PMC5376300
 
DOI:
 
10.1371/journal.pone.0173018
Categories: toxoplasma news feeds

Widespread 5-methylcytosine in the genomes of avian Coccidia and other apicomplexan parasites

The Anti-Toxo Blog - 10 April 2017 - 3:21pm
 2017 Mar 30. doi: 10.1007/s00436-017-5434-x. [Epub ahead of print]
Gong Z1,2, Yin H1,2, Ma X1,2, Liu B1,2, Han Z1,2, Gou L1,2, Cai J3,4.AbstractTo date, little is known about cytosine methylation in the genomic DNA of apicomplexan parasites, although it has been confirmed that this important epigenetic modification exists in many lower eukaryotes, plants, and animals. In the present study, ELISA-based detection demonstrated that low levels of 5-methylcytosine (5-mC) are present in Eimeria spp., Toxoplasma gondii, Cryptosporidium spp., and Neospora caninum. The proportions of 5-mC in genomic DNA were 0.18 ± 0.02% in E tenella sporulated oocysts, 0.19 ± 0.01% in E. tenella second-generation merozoites, 0.22 ± 0.04% in T. gondii tachyzoites, 0.28 ± 0.03% in N. caninum tachyzoites, and 0.06 ± 0.01, 0.11 ± 0.01, and 0.09 ± 0.01% in C. andersoni, C. baileyi, and C. parvum sporulated oocysts, respectively. In addition, we found that the percentages of 5-mC in E. tenella varied considerably at different life stages, with sporozoites having the highest percentage of 5-mC (0.78 ± 0.10%). Similar stage differences in 5-mC were also found in E. maxima, E. necatrix, and E. acervulina, the levels of 5-mC in their sporozoites being 4.3-, 1.8-, 2.5-, and 2.0-fold higher than that of sporulated oocysts, respectively (p < 0.01). Furthermore, a total DNA methyltransferase-like activity was detected in whole cell extracts prepared from E. tenella sporozoites. In conclusion, genomic DNA methylation is present in these apicomplexan parasites and may play a role in the stage conversion of Eimeria.KEYWORDS: 5-Methylcytosine; Apicomplexan parasites; DNA methyltransferase-like activity; Eimeria spp.; Genomic DNA
PMID:
 
28361273
 
DOI:
 
10.1007/s00436-017-5434-x
Categories: toxoplasma news feeds

Optogenetic monitoring identifies phosphatidylthreonine-regulated calcium homeostasis in Toxoplasma gondii

The Anti-Toxo Blog - 10 April 2017 - 3:20pm
 2016 May 2;3(5):215-223. doi: 10.15698/mic2016.05.500.
Kuchipudi A1, Arroyo-Olarte RD1, Hoffmann F1, Brinkmann V1, Gupta N2.AbstractToxoplasma gondii is an obligate intracellular parasite, which inflicts acute as well as chronic infections in a wide range of warm-blooded vertebrates. Our recent work has demonstrated the natural occurrence and autonomous synthesis of an exclusive lipid phosphatidylthreonine in T. gondii. Targeted gene disruption of phosphatidylthreonine synthase impairs the parasite virulence due to unforeseen attenuation of the consecutive events of motility, egress and invasion. However, the underlying basis of such an intriguing phenotype in the parasite mutant remains unknown. Using an optogenetic sensor (gene-encoded calcium indicator, GCaMP6s), we show that loss of phosphatidylthreonine depletes calcium stores in intracellular tachyzoites, which leads to dysregulation of calcium release into the cytosol during the egress phase of the mutant. Consistently, the parasite motility and egress phenotypes in the mutant can be entirely restored by ionophore-induced mobilization of calcium. Collectively, our results suggest a novel regulatory function of phosphatidylthreonine in calcium signaling of a prevalent parasitic protist. Moreover, our application of an optogenetic sensor to monitor subcellular calcium in a model intracellular pathogen exemplifies its wider utility to other entwined systems.KEYWORDS: Toxoplasma gondii; calcium homeostasis; gene-encoded calcium indicator; intracellular parasite; lytic cycle; optogenetics; phosphatidylthreonine
PMID:
 
28357357
 
PMCID:
 
PMC5349149
 
DOI:
 
10.15698/mic2016.05.500
Categories: toxoplasma news feeds

Plant hormone cytokinins control cell cycle progression and plastid replication in apicomplexan parasites

The Anti-Toxo Blog - 28 March 2017 - 1:34pm

2017 Mar 23. pii: S1383-5769(16)30541-4. doi: 10.1016/j.parint.2017.03.003. [Epub ahead of print]
Andrabi SB1, Tahara M2, Matsubara R2, Toyama T3, Aonuma H4, Sakakibara H5, Suematsu M6, Tanabe K7, Nozaki T8, Nagamune K9.
Cytokinins are plant hormones that are involved in regulation of cell proliferation, cell cycle progression, and cell and plastid development. Here, we show that the apicomplexan parasites Toxoplasma gondii and Plasmodium berghei, an opportunistic human pathogen and a rodent malaria agent, respectively, produce cytokinins via a biosynthetic pathway similar to that in plants. Cytokinins regulate the growth and cell cycle progression of T. gondii by mediating expression of the cyclin gene TgCYC4. A natural form of cytokinin, trans-zeatin (t-zeatin), upregulated expression of this cyclin, while a synthetic cytokinin, thidiazuron, downregulated its expression. Immunofluorescence microscopy and quantitative PCR analysis showed that t-zeatin increased the genome-copy number of apicoplast, which are non-photosynthetic plastid, in the parasite, while thidiazuron led to their disappearance. Thidiazuron inhibited growth of T. gondii and Plasmodium falciparum, a human malaria parasite, suggesting that thidiazuron has therapeutic potential as an inhibitor of apicomplexan parasites.
Copyright © 2017. Published by Elsevier B.V.KEYWORDS: Cytokinins; Plant hormones; Plasmodium berghei; Thidiazuron; Toxoplasma gondii
PMID:
28344153
DOI:
10.1016/j.parint.2017.03.003
Categories: toxoplasma news feeds

Stability and function of a putative microtubule organizing center in the human parasite Toxoplasma gondii

The Anti-Toxo Blog - 24 March 2017 - 1:21pm
2017 Mar 22. pii: mbc.E17-01-0045. doi: 10.1091/mbc.E17-01-0045. [Epub ahead of print]
Leung JM1, He Y1, Zhang F2, Hwang YC3, Nagayasu E4, Liu J1, Murray JM1, Hu K5.
The organization of the microtubule cytoskeleton is dictated by microtubule nucleators or organizing centers.  Toxoplasma gondii, an important human parasite, has an array of 22 regularly spaced cortical microtubules stemming from a hypothesized organizing center, the apical polar ring. Here, we examine the functions of the apical polar ring by characterizing two of its components, KinesinA and APR1, and discovered that its putative role in templating can be separated from its mechanical stability. Parasites that lack both KinesinA and APR1 (ΔkinesinAΔapr1) are capable of generating 22 cortical microtubules. However, the apical polar ring is fragmented in live ΔkinesinAΔapr1 parasites, and is undetectable by electron microscopy after detergent extraction. Disintegration of the apical polar ring results in the detachment of groups of microtubules from the apical end of the parasite. These structural defects are linked to a diminished ability of the parasite to move and to invade host cells, as well as decreased secretion of effectors important for these processes. Together, the findings demonstrate the importance of the structural integrity of the apical polar ring and the microtubule array in the Toxoplasma lytic cycle, which is responsible for massive tissue destruction in acute toxoplasmosis.
© 2017 by The American Society for Cell Biology.
PMID:
28331073
DOI:
10.1091/mbc.E17-01-0045
Categories: toxoplasma news feeds

The Toxoplasma Parasitophorous Vacuole: An Evolving Host-Parasite Frontier

The Anti-Toxo Blog - 24 March 2017 - 1:20pm
2017 Mar 19. pii: S1471-4922(17)30065-X. doi: 10.1016/j.pt.2017.02.007. [Epub ahead of print]
Clough B1, Frickel EM2.
The parasitophorous vacuole is a unique replicative niche for apicomplexan parasites, including Toxoplasma gondii. Derived from host plasma membrane, the vacuole is rendered nonfusogenic with the host endolysosomal system. Toxoplasma secretes numerous proteins to modify the forming vacuole, enable nutrient uptake, and set up mechanisms of host subversion. Here we describe the pathways of host-parasite interaction at the parasitophorous vacuole employed by Toxoplasma and host, leading to the intricate balance of host defence versus parasite survival.
Copyright © 2017 Elsevier Ltd. All rights reserved.KEYWORDS: Toxoplasma gondii; guanylate-binding proteins; host–pathogen interaction; immunity-related GTPases; parasitophorous vacuole; rhoptry proteins
PMID:
28330745
DOI:
10.1016/j.pt.2017.02.007
Categories: toxoplasma news feeds

Toxoplasma gondii F-actin forms an extensive filamentous network required for material exchange and parasite maturation

The Anti-Toxo Blog - 23 March 2017 - 12:18pm
 2017 Mar 21;6. pii: e24119. doi: 10.7554/eLife.24119. [Epub ahead of print]
Periz J1, Whitelaw J1, Harding C1, Gras S1, Del Rosario Minina MI1, Latorre-Barragan F1, Lemgruber L1, Reimer MA1, Insall R2, Heaslip A3, Meissner M1.AbstractApicomplexan actin is important during the parasite's life cycle. Its polymerization kinetics are unusual, permitting only short, unstable F-actin filaments. It has not been possible to study actin in vivo and so its physiological roles have remained obscure, leading to models distinct from conventional actin behaviour. Here a modified version of the commercially available Actin-Chromobody® was tested as a novel tool for visualising F-actin dynamics in Toxoplasma gondii. Cb labels filamentous actin structures within the parasite cytosol and labels an extensive F-actin network that connects parasites within the parasitophorous vacuole and allows vesicles to be exchanged between parasites. In the absence of actin, parasites lack a residual body and inter-parasite connections and grow in an asynchronous and disorganized manner. Collectively, these data identify new roles for actin in the intracellular phase of the parasites lytic cycle and provide a robust new tool for imaging parasitic F-actin dynamics.KEYWORDS: cell biology; infectious disease; microbiology
PMID:
 
28322189
 
DOI:
 
10.7554/eLife.24119
Categories: toxoplasma news feeds

Lactate dehydrogenase in Toxoplasma gondii controls virulence, bradyzoite differentiation, and chronic infection

The Anti-Toxo Blog - 23 March 2017 - 12:18pm
 2017 Mar 21;12(3):e0173745. doi: 10.1371/journal.pone.0173745. eCollection 2017.
Abdelbaset AE1,2, Fox BA3, Karram MH2, Abd Ellah MR2, Bzik DJ3, Igarashi M1.AbstractIn the asexual stages, Toxoplasma gondii stage converts between acute phase rapidly replicating tachyzoites and chronic phase slowly dividing bradyzoites. Correspondingly, T. gondii differentially expresses two distinct genes and isoforms of the lactate dehydrogenase enzyme, expressing LDH1 exclusively in the tachyzoite stage and LDH2 preferentially in the bradyzoite stage. LDH catalyzes the interconversion of pyruvate and lactate in anaerobic growth conditions and is utilized for energy supply, however, the precise role of LDH1 and LDH2 in parasite biology in the asexual stages is still unclear. Here, we investigated the biological role of LDH1 and LDH2 in the asexual stages, and the vaccine strain potential of deletion mutants lacking LDH1, LDH2, or both genes (Δldh1, Δldh2 and Δldh1/2). Deletion of LDH1 reduced acute parasite virulence, impaired bradyzoite differentiation in vitro, and markedly reduced chronic stage cyst burdens in vivo. In contrast, deletion of LDH2 impaired chronic stage cyst burdens without affecting virulence or bradyzoite differentiation. Deletion of both LDH1 and LDH2 induced a more severe defect in chronic stage cyst burdens. These LDH mutant phenotypes were not associated with any growth defect. Vaccination of mice with a low dose of mutants deleted for LDH elicited effective protective immunity to lethal challenge infection, demonstrating the vaccine potential of LDH deletion mutants. These results suggest that lactate dehydrogenase in T. gondii controls virulence, bradyzoite differentiation, and chronic infection and reveals the potential of LDH mutants as vaccine strains.
PMID:
 
28323833
 
DOI:
 
10.1371/journal.pone.0173745
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