Wednesday, June 21, 2017

Toxoplasma depends on lysosomal consumption of autophagosomes for persistent infection

 2017 Jun 19;2:17096. doi: 10.1038/nmicrobiol.2017.96.

Abstract

Globally, nearly 2 billion people are infected with the intracellular protozoan Toxoplasma gondii1. This persistent infection can cause severe disease in immunocompromised people and is epidemiologically linked to major mental illnesses2 and cognitive impairment3. There are currently no options for curing this infection. The lack of effective therapeutics is due partly to a poor understanding of the essential pathways that maintain long-term infection. Although it is known that Toxoplasma replicates slowly within intracellular cysts demarcated with a cyst wall, precisely how it sustains itself and remodels organelles in this niche is unknown. Here, we identify a key role for proteolysis within the parasite lysosomal organelle (the vacuolar compartment or VAC) in turnover of autophagosomes and persistence during neural infection. We found that disrupting a VAC-localized cysteine protease compromised VAC digestive function and markedly reduced chronic infection. Death of parasites lacking the VAC protease was preceded by accumulation of undigested autophagosomes in the parasite cytoplasm. These findings suggest an unanticipated function for parasite lysosomal degradation in chronic infection, and identify an intrinsic role for autophagy in the T. gondii parasite and its close relatives. This work also identifies a key element of Toxoplasma persistence and suggests that VAC proteolysis is a prospective target for pharmacological development.
PMID:
 
28628099
 
DOI:
 
10.1038/nmicrobiol.2017.96

The heat shock protein 90 of Toxoplasma gondii is essential for invasion of host cells and tachyzoite growth

 2017;24:22. doi: 10.1051/parasite/2017023. Epub 2017 Jun 19.

Sun H1Zhuo X1Zhao X2Yang Y1Chen X1Yao C3Du A1.

Abstract

Toxoplasma gondii is an obligate intracellular apicomplexan parasite that infects almost all warm-blooded vertebrates. Heat shock proteins (HSP) regulate key signal transduction events in many organisms, and heat shock protein 90 (Hsp90) plays an important role in growth, development, and virulence in several parasitic protozoa. Here, we discovered increased transcription of the Hsp90 gene under conditions for bradyzoite differentiation, i.e. alkaline and heat shock conditions in vitro, suggesting that Hsp90 may be connected with bradyzoite development in T. gondii. A knockout of the TgHsp90 strain (ΔHsp90) and a complementation strain were constructed. The TgHsp90 knockout cells were found to be defective in host-cell invasion, were not able to proliferate in vitro in Vero cells, and did not show long-time survival in mice in vivo. These inabilities of the knockout parasites were restored upon complementation of TgHsp90. These data unequivocally show that TgHsp90 contributes to bradyzoite development, and to invasion and replication of T. gondii in host cells.
PMID:
 
28627357
 
DOI:
 
10.1051/parasite/2017023

Proteomic Differences between Developmental Stages of Toxoplasma gondii Revealed by iTRAQ-Based Quantitative Proteomics

 2017 Jun 2;8:985. doi: 10.3389/fmicb.2017.00985. eCollection 2017.

Wang ZX1Zhou CX1,2Elsheikha HM3He S1,4Zhou DH1Zhu XQ1,5.

Abstract

Toxoplasma gondii has a complex two-host life-cycle between intermediate host and definitive host. Understanding proteomic variations across the life-cycle stages of T. gondii may improve the understanding of molecular adaption mechanism of T. gondiiacross life-cycle stages, and should have implications for the development of new treatment and prevention interventions against T. gondii infection. Here, we utilized LC-MS/MS coupled with iTRAQ labeling technology to identify differentially expressed proteins (DEPs) specific to tachyzoite (T), bradyzoites-containing cyst (C) and sporulated oocyst (O) stages of the cyst-forming T. gondiiPrugniuad (Pru) strain. A total of 6285 proteins were identified in the three developmental stages of T. gondii. Our analysis also revealed 875, 656, and 538 DEPs in O vs. T, T vs. C, and C vs. O, respectively. The up- and down-regulated proteins were analyzed by Gene Ontology enrichment, KEGG pathway and STRING analyses. Some virulence-related factors and ribosomal proteins exhibited distinct expression patterns across the life-cycle stages. The virulence factors expressed in sporulated oocysts and the number of up-regulated virulence factors in the cyst stage were about twice as many as in tachyzoites. Of the 79 ribosomal proteins identified in T. gondii, the number of up-regulated ribosomal proteins was 33 and 46 in sporulated oocysts and cysts, respectively, compared with tachyzoites. These results support the hypothesis that oocyst and cystic stages are able to adapt to adverse environmental conditions and selection pressures induced by the host's immune response, respectively. These findings have important implications for understanding of the developmental biology of T. gondii, which may facilitate the discovery of novel therapeutic targets to better control toxoplasmosis.

KEYWORDS: 

Toxoplasma gondii; differentially expressed protein (DEP); iTRAQ; life-cycle; mass spectrometry; proteomics
PMID:
 
28626452
 
PMCID:
 
PMC5454076
 
DOI:
 
10.3389/fmicb.2017.00985

Monday, June 19, 2017

Schizogony and gametogony of oocyst-deficient T-263 strain of Toxoplasma gondii

 2017 May 27. pii: S0304-4017(17)30225-X. doi: 10.1016/j.vetpar.2017.05.024. [Epub ahead of print]

Abstract

Oocysts are important stage for the spread of Toxoplasma gondii because they are environmentally resistant. Among all hosts of T. gondii, only felids can excrete oocysts. Cats that have excreted T. gondii oocysts after primary infection develop immunity to re-excretion of oocysts, and this immunity appears to be long-lasting. It would be desirable to have a non-infectious vaccine for the prevention of T. gondii infection in cats and to understand mechanism of immunity to excretion of oocysts. An initial step will be to indentify stage/stages of the parasite for induction of immunity. A chemically-induced mutant of T. gondii, T-263, is immunogenic but lacks the capacity to form oocysts in cats. Cats fed live bradyzoites of T-263 do not excrete oocysts after challenge with oocyst producing strains. However, it is not known at what stage of the parasite development the oocyst formation is halted. Here, four cats were fed live tissue cysts of the T-263 strain and examined for enteroepithelial stages and oocyst production. Two cats were administered methyl prednisolone aceatate (20mg/kg) once intramuscularly and these cats were euthanized 5 and 7days post inoculation. No oocysts but immature and mature schizonts (types D and E), male, and female gamonts were detected in two cats euthanized. The remaining two cats did not excrete oocysts examined 3-14days post inoculation, but both seroconverted and developed antibody titers of 1:400 tested by the modification agglutination test, indicating exposure to the inocula. The results demonstrate that the T-263 strain is defective in oocyst formation and the observations should help future studies in identification of genes/factors responsible for oocyst formation in the intestine of cats.

KEYWORDS: 

Gamonts; Oocysts; T-263 strain; Toxoplasma gondii
PMID:
 
28624132
 
DOI:
 
10.1016/j.vetpar.2017.05.024

Wednesday, June 14, 2017

Transcriptional Responses in the Murine Spleen after Toxoplasma gondii Infection: Inflammasome and Mucus-Associated Genes

I 2017 Jun 10;18(6). pii: E1245. doi: 10.3390/ijms18061245.

Abstract

The spleen plays an important role in coordinating both adaptive and innate immune responses. Here, the transcriptional response to T. gondii infection in the murine spleen was characterized concerning inflammasome sensors (two different models: seven days after oral or four weeks after intraperitoneal infection). Additionally, Tff1KO and Tff3KO mice were investigated because TFF genes are often upregulated during inflammation. The expression of the pattern-recognition receptors Nlrp3, Nlrp12, and Nlrp1a was significantly increased after infection. This increase was diminished in Tff1KO and Tff3KO mice pointing towards a positive regulation of the inflammatory response by Tff1 and Tff3. Furthermore, the transcription of Tff1 (encoding a motogenic lectin) and other secretory genes was analyzed, i.e., gastrokines (Gkn), IgG Fc binding protein (Fcgbp), and the mucin Muc2. The corresponding gene products belong to an interactome protecting mucous epithelia. Tff1 was significantly induced after infection, which might increase the motility of immune cells. In contrast, Gkn3, Fcgbp, and Muc2 were downregulated seven days after oral infection; whereas four weeks after i.p. infection only Gkn3 remained downregulated. This might be an indication that Gkn3, Fcgbp, and Muc2 are involved in the transient disruption of the splenic architecture and its reorganization, which is characteristic after T. gondii infection.

KEYWORDS: 

IgG Fc binding protein; MUC2; TFF1; Toxoplasma gondii; gastrokine; inflammasome; inflammation; trefoil factor
PMID:
 
28604600
 
DOI:
 
10.3390/ijms18061245

Parkinson's disease and Toxoplasma gondii Infection: Sero-molecular Assess the Possible Link among Patients

 2017 Jun 8. pii: S0001-706X(16)30989-5. doi: 10.1016/j.actatropica.2017.06.002. [Epub ahead of print]

Abstract

We investigated the possible association between Parkinson's disease (PD), the second most common neurodegenerative disorder and Toxoplasma gondii infection, the most common neurotropic protozoan parasitic infection, using serological and molecular techniques. One hundred and fifteen patients with confirmed PD and 115 healthy subjects in the same age and sex distribution were enrolled in this study. Blood samples were taken from each participant and the sera were screened for anti-Toxoplasma antibodies (IgG and IgM). PCR assay was performed in duplicate using the primer pair targeting the B1 gene of Toxoplasma. Amplicons were directly sequenced to conduct the phylogenetic analysis. The prevalence of Toxoplasma infection based on IgG titer was 53% in case and 55.6% in the control groups, revealing no statistically significant association between Toxoplasma seropositivity and PD (OR=0.90; 95% CI=0.54-1.51; P=0.691). According to PCR assay, the prevalence of Toxoplasma infections was 19.3% in the case and 10.4% in control groups which the difference was statistically significant (OR=3.02; 95% CI=1.46-6.27; P=0.002). Multiple sequence alignment of Toxoplasma gondii isolates manifested a common haplotype by the identity: 93.6-100% and divergence: 0-6.7%. We concluded that T. gondii infection not only could not be a risk factor to PD, but even it could be concluded that patients with PD are in more risk to acquisition of infection. These results provide fresh insights into the ambiguous association between T. gondii infection and PD.

KEYWORDS: 

Parkinson’s disease; Sero-molecular assessment; Toxoplasma gondii infection
PMID:
 
28602836
 
DOI:
 
10.1016/j.actatropica.2017.06.002

Essential role for GABARAP autophagy proteins in interferon-inducible GTPase-mediated host defense


 2017 Jun 12. doi: 10.1038/ni.3767. [Epub ahead of print]

Abstract

Mammalian autophagy-related 8 (Atg8) homologs consist of LC3 proteins and GABARAPs, all of which are known to be involved in canonical autophagy. In contrast, the roles of Atg8 homologs in noncanonical autophagic processes are not fully understood. Here we show a unique role of GABARAPs, in particular gamma-aminobutyric acid (GABA)-A-receptor-associated protein-like 2 (Gabarapl2; also known as Gate-16), in interferon-γ (IFN-γ)-mediated antimicrobial responses. Cells that lacked GABARAPs but not LC3 proteins and mice that lacked Gate-16 alone were defective in the IFN-γ-induced clearance of vacuolar pathogens such as Toxoplasma. Gate-16 but not LC3b specifically associated with the small GTPase ADP-ribosylation factor 1 (Arf1) to mediate uniform distribution of interferon-inducible GTPases. The lack of GABARAPs reduced Arf1 activation, which led to formation of interferon-inducible GTPase-containing aggregates and hampered recruitment of interferon-inducible GTPases to vacuolar pathogens. Thus, GABARAPs are uniquely required for antimicrobial host defense through cytosolic distribution of interferon-inducible GTPases.
PMID:
 
28604719
 
DOI:
 
10.1038/ni.3767

Toxoplasmosis in hematopoietic cell transplant recipients

 2017 Jun 12. doi: 10.1111/tid.12734. [Epub ahead of print]

Abstract

We read with interest the recent article entitled "Allogeneic hematopoietic stem cell transplant recipients and parasitic diseases: A review of the literature of clinical cases and perspectives to screen and follow-up active and latent chronic infections" by Fabiani et al.1 The authors attempted to summarize major parasitic infections in this patient population without using any language or time restriction. However, we have concerns about the details and accuracy of the study, especially with regards to toxoplasmosis. This article is protected by copyright. All rights reserved.

KEYWORDS: 

Toxoplasma ; hematopoietic stem cell transplant; toxoplasmosis
PMID:
 
28605082
 
DOI:
 
10.1111/tid.12734

Identification of compounds that suppress Toxoplasma gondii tachyzoites and bradyzoites

 2017 Jun 13;12(6):e0178203. doi: 10.1371/journal.pone.0178203. eCollection 2017.

Abstract

Drug treatment for toxoplasmosis is problematic, because current drugs cannot eradicate latent infection with Toxoplasma gondii and can cause bone marrow toxicity. Because latent infection remains after treatment, relapse of infection is a problem in both infections in immunocompromised patients and in congenitally infected patients. To identify lead compounds for novel drugs against Toxoplasma gondii, we screened a chemical compound library for anti-Toxoplasma activity, host cell cytotoxicity, and effect on bradyzoites. Of 878 compounds screened, 83 demonstrated >90% parasite growth inhibition. After excluding compounds that affected host cell viability, we further characterized two compounds, tanshinone IIA and hydroxyzine, which had IC50 values for parasite growth of 2.5 μM and 1.0 μM, respectively, and had no effect on host cell viability at 25 μM. Both tanshinone IIA and hydroxyzine inhibited parasite replication after invasion and both reduced the number of in vitro-induced bradyzoites, whereas, pyrimethamine, the current therapy, had no effect on bradyzoites. Both tanshinone IIA and hydroxyzine are potent lead compounds for further medicinal chemistry. The method presented for evaluating compounds for bradyzoite efficacy represents a new approach to the development of anti-Toxoplasma drugs to eliminate latency and treat acute infection.
PMID:
 
28609444
 
DOI:
 
10.1371/journal.pone.0178203