Thursday, May 31, 2007

Young C3H mice infected with Toxoplasma gondii are a novel experimental model of communicating hydrocephalus

Neurol Res. 2007 Mar 12; [Epub ahead of print]

Young C3H mice infected with Toxoplasma gondii are a novel experimental model of communicating hydrocephalus

Harada T, Takamoto M, Jin DH, Tada T, Sugane K.

The effects of leptomeningeal inflammation on the development of hydrocephalus are less understood than those of obstructing the flow of cerebrospinal fluid (CSF) in animal models. We succeeded in introducing a novel experimental model of hydrocephalus and analysed changes in histopathology and CSF flow in mice infected with an avirulent Fukaya strain of Toxoplasma gondii (T. gondii). Six to 7 week-old male mice were orally inoculated with a brain homogenate containing ten T. gondii cysts. The cerebral ventricles became enlarged in all C3H/HeN and C57BL/6 mice 4 weeks after T. gondii infection, but mildly in BALB/c mice. In addition to the lateral ventricle, the third and fourth ventricles and Sylvian aqueducts were dilated in all mice. Lymphocytes and monocytes infiltrated the subarachnoid space. Indian ink particles required more time to pass from the lateral ventricle to the cervical lymph nodes, although they reached the subarachnoid space. Computed tomography ventriculography demonstrated that the CSF was not obstructed during passage through the ventricular systems, but contrast remained static in the lateral ventricle only in infected mice. These results indicated that the infected mice developed communicating type hydrocephalus without obstructive or mass lesions in the ventricles. The hydrocephalus that arises in mice infected with T. gondii is considered a consequence of leptomeningeal inflammation that blocks CSF circulation at the subarachnoid space, implying that leptomeningeal inflammation is important in other types of hydrocephalus. [Neurol Res 2007; 29: 000000].

PMID: 17535576 [PubMed - as supplied by publisher]

Discovery of parasite virulence genes reveals a unique regulator of chromosome condensation 1 ortholog critical for efficient nuclear trafficking

Proc Natl Acad Sci U S A. 2007 May 29; [Epub ahead of print]

Discovery of parasite virulence genes reveals a unique regulator of chromosome condensation 1 ortholog critical for efficient nuclear trafficking

Frankel MB, Mordue DG, Knoll LJ.

Department of Medical Microbiology and Immunology, University of Wisconsin, 1300 University Avenue, Madison, WI 53706.

Eukaryotic parasites are a leading cause of morbidity and mortality worldwide, yet little is known about the genetic basis of their virulence. Here, we present a forward genetic screen to study pathogenesis in the protozoan parasite Toxoplasma gondii. By using modified signature-tagged mutagenesis, the growth of 6,300 T. gondii insertional mutants was compared in cell culture and murine infection to identify genes required specifically in vivo. One of the 39 avirulent mutants is disrupted in a divergent ortholog of the regulator of chromosome condensation 1 (RCC1), which is critical for nuclear trafficking in model systems. Although this RCC1 mutant grows similar to wild type in standard tissue culture conditions, it is growth-impaired under nutrient limitation. Genetic complementation of mutant parasites with the T. gondii RCC1 gene fully restores both virulence in mice and growth under low-nutrient conditions. Further analysis shows that there is a significant defect in nuclear trafficking in the RCC1 mutant. These findings suggest that the rate of nuclear transport is a critical factor affecting growth in low-nutrient conditions in vivo and in vitro. Additionally, we observed that although RCC1 proteins are highly conserved in organisms from humans to yeast, no protozoan parasite encodes a characteristic RCC1. This protein divergence may represent a unique mechanism of nucleocytoplasmic transport. This study illustrates the power of this forward genetics approach to identify atypical virulence mechanisms.

PMID: 17535896 [PubMed - as supplied by publisher]

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Tuesday, May 29, 2007

Protein trafficking to the apicoplast: deciphering the apicomplexan solution to secondary endosymbiosis

Eukaryot Cell. 2007 May 18; [Epub ahead of print]

Protein trafficking to the apicoplast: deciphering the apicomplexan solution to secondary endosymbiosis

Parsons M, Karnataki A, Feagin JE, Derocher A.

Seattle Biomedical Research Institute, 307 Westlake Ave. N., Seattle, WA 98109; Department of Pathobiology, University of Washington, Seattle, WA 98195.

Almost 20 years ago, the first sequence was published from a 35 kb circular molecule found in Plasmodium falciparum, the most virulent of human malaria parasites (20). ...

PMID: 17513565 [PubMed - as supplied by publisher]

A heterologous prime-boost vaccination regime using DNA and a vaccinia virus, both expressing GRA4, induced protective immunity against Toxo

Parasitology. 2007 May 17;:1-8

A heterologous prime-boost vaccination regime using DNA and a vaccinia virus, both expressing GRA4, induced protective immunity against Toxoplasma gondii infection in mice

Zhang G, Huong VT, Battur B, Zhou J, Zhang H, Liao M, Kawase O, Lee EG, Dautu G, Igarashi M, Nishikawa Y, Xuan X.
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.

PMID: 17506929 [PubMed - as supplied by publisher]

GRA2, a new marker for the serodiagnosis of acute Toxoplasma infection

Diagn Microbiol Infect Dis. 2007 May 15

The dense granule protein GRA2, a new marker for the serodiagnosis of acute Toxoplasma infection: comparison of sera collected in both France and Iran from pregnant women

Golkar M, Rafati S, Abdel-Latif MS, Brenier-Pinchart MP, Fricker-Hidalgo H, Sima BK, Babaie J, Pelloux H, Cesbron-Delauw MF, Mercier C.
CNRS UMR 5163, UFR de Biologie, Institut Jean Roget, Universite Joseph Fourier, Campus Sante, Domaine de la Merci, 38042 Grenoble cedex 09, France; Molecular Parasitology Laboratory, Pasteur Institute of Iran, Tehran 13164, Iran.

GRA2 is a highly immunogenic protein secreted from the dense granules of Toxoplasma gondii. Recent success in purifying full-length, soluble GRA2 from bacteria as a thioredoxin (TRX)-(Hisx6) fusion protein led to investigate the antigenicity of the recombinant protein against human sera. On immunoblots, TRX-(Hisx6)-GRA2 was recognized by sera collected in Iran from T. gondii-infected pregnant women. An IgG enzyme-linked immunosorbent assay was developed to evaluate the reactivity of sera, collected from pregnant women both in France and Iran, to the TRX-(Hisx6)-GRA2 fusion protein. Specificity of the test was 96.4%. Sensitivity of the GRA2 enzyme-linked immunosorbent assay ranged from 95.8% (sera collected in France) to 100% (sera collected in Iran) for sera of acute infection and from 65.7% (sera collected in France) to 71.4% (sera collected in Iran) for sera of chronic infection. The recombinant GRA2 could thus advantageously complement previously described T. gondii antigens for the serodiagnosis of acute Toxoplasma infection.

PMID: 17509806 [PubMed - as supplied by publisher]

Toxo triggers secretion of interleukin-12 but low level of interleukin-10 from the THP-1 human monocytic cell line

Cytokine. 2007 May 16; [Epub ahead of print]

Toxoplasma gondii triggers secretion of interleukin-12 but low level of interleukin-10 from the THP-1 human monocytic cell line

Aldebert D, Durand F, Mercier C, Brenier-Pinchart MP, Cesbron-Delauw MF, Pelloux H.
Laboratoire Adaptation et Pathogenie des Microorganismes, UMR 5163 CNRS-Universite Joseph Fourier, Institut J. Roget, BP 170, 38042 Grenoble Cedex 9, France.

Previous studies using both in vitro and in vivo mouse models have demonstrated that a subtle balance between pro- and anti-inflammatory cytokines, among which interleukin-12 (IL-12) and interleukin-10 (IL-10), respectively is crucial to control Toxoplasma infection. However, the few studies performed with human cell lines highlighted important host-related differences in the immune response to Toxoplasma gondii. The goal of our work was thus to study the production of both IL-12 and IL-10 by the THP-1 human monocytic cell line in response to Toxoplasma. We demonstrated that infection by live parasites (RH strain) triggers secretion of IL-12, but low level of IL-10. IL-12 secretion appeared within 8h, up to 48h. We also showed that infection by live parasites is not mandatory since heat-killed parasites, crude tachyzoite lysate as well as excreted/secreted antigens induced significant, yet reduced production of IL-12.

PMID: 17512211 [PubMed - as supplied by publisher]

Treatment of Toxoplasmic Encephalitis in AIDS Patients

J Int Assoc Physicians AIDS Care (Chic Ill). 2007 May 21; [Epub ahead of print]

Randomized Controlled Trial of Pyrimethamine Plus Sulfadiazine Versus Trimethoprim Plus Sulfamethoxazole for Treatment of Toxoplasmic Encephalitis in AIDS Patients

Kongsaengdao S, Samintarapanya K, Oranratnachai K, Prapakarn W, Apichartpiyakul C.

Division of Neurology, Department of Medicine, Rajavithi Hospital.

Background: Toxoplasmic encephalitis (TE), caused by Toxoplasma gondii, is common in AIDS patients. TE can result in tissue destruction via massive inflammation and brain abscess formation. METHODS: Randomized controlled trials were performed in AIDS patients to assess which drug regimen was optimally effective for the treatment of TE. AIDS patients with TE were randomly divided into 3 groups that received a 6-week course of either pyrimethamine (50 mg/ day or 100 mg/day) plus sulfadiazine (4 g/day) and folinic acid (25 mg/day) or trimethoprim (10 mg/kg/day) plus sulfamethoxazole (50 mg/kg/day) (TMP-SMX), and results were evaluated with respect to clinical response, mortality, morbidity, and serious adverse events. The primary outcome was defined as death in the first 6-week period. The secondary outcome was successful treatment within 6 weeks without severe adverse events, bone marrow suppression, drug-induced rash, or any other event that caused a change in the treatment regimen. RESULTS: The results from this study showed that in AIDS patients, TE was most successfully treated with the combination of pyrimethamine (50 mg/day) plus sulfadiazidine (4 g/day) and folinic acid (25 mg/day); failure rates were not significantly different among the 3 treatment groups. Conclusions: Available data suggest that of the currently available options, treatment of TE with pyrimethamine at 50 mg/day plus sulfadiazidine at 4 g/day provides the best primary outcome for AIDS patients with TE; however, because this study was terminated prematurely, we suggest that treatment with intravenous TMP-SMX be further evaluated to determine its efficacy.

PMID: 17517949 [PubMed - as supplied by publisher]

Diagnostic problems and postnatal follow-up in congenital toxoplasmosis

Minerva Pediatr. 2007 Jun;59(3):207-13.

Diagnostic problems and postnatal follow-up in congenital toxoplasmosis

Mazzola A, Casuccio A, Romano A, Schimmenti MG, Titone L, Di Carlo P.

RNAS Civico Benfratelli, G. Di Cristina and M. Ascoli, Palermo, Italy.

AIM: In order to assess the consequences of different clinical approaches in the prenatal management of congenital toxoplasmosis, we retrospectively reviewed 58 pregnant women with Toxoplasma seroconversion and prospectively enrolled their 59 infants, referred to us from 1999 to 2004. METHODS: Data on clinical, laboratory and demographic characteristics of the pregnant women were collected. Their children were entered into a 48-month follow-up programme in which clinical, instrumental, ophthalmologic and serologic evaluations were carried out at birth, at 1, 3, 6, 9, 15, 18, 24, 36 and at 48 months of life. Paediatric treatment with Spiramycin alone or alternated with Pyrime-thamine-Sulphadiazine was administered according to the different clinical cases. RESULTS: Time of infection was dated in the first trimester for 24 women (41%), in the second trimester for 18 women (31%) and in the third trimester for 16 (28%). In the first trimester of pregnancy 20 of the 24 infected women had undergone amniocentesis, while the test had not been performed on any of the women infected in the third trimester. Serological follow-up revealed that 11 (19%) of the infants had been infected. An alternating regimen with Pyrimethamine-Sulphadoxine was administered to the infected children. All the infants were clinically asymptomatic, and the instrumental follow-up revealed specific toxoplasmosis anomalies in 4/11 infected children. CONCLUSION: Our results highlight issues and problems concerning current prenatal diagnostic tests and the therapeutic approach based on PCR testing of amniotic fluid alone. The incidence of ocular-cerebral lesions observed in children born to women with seroconversion in the third trimester raises questions about the diagnostic and therapeutic approach for these women and their offspring. Paediatric therapeutic protocol, with alternating Pyrime-thamine-Sulphadiazine regimen, applied also to asymptomatic children born to women with inadequate prenatal diagnostic management, could prevent severe sequelae.

PMID: 17519865 [PubMed - in process]

Thursday, May 17, 2007

Suicide prevention: disruption of apoptotic pathways by protozoan parasites

Mol Microbiol. 2007 May;64(4):904-16.

Suicide prevention: disruption of apoptotic pathways by protozoan parasites

Carmen JC, Sinai AP.

Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40536, USA.

The modulation of apoptosis has emerged as an important weapon in the pathogenic arsenal of multiple intracellular protozoan parasites. Cryptosporidium parvum, Leishmania spp., Trypanosoma cruzi, Theileria spp., Toxoplasma gondii and Plasmodium spp. have all been shown to inhibit the apoptotic response of their host cell. While the pathogen mediators responsible for this modulation are unknown, the parasites are interacting with multiple apoptotic regulatory systems to render their host cell refractory to apoptosis during critical phases of intracellular infection, including parasite invasion, establishment and replication. Additionally, emerging evidence suggests that the parasite life cycle stage impacts the modulation of apoptosis and possibly parasite differentiation. Dissection of the host-pathogen interactions involved in modulating apoptosis reveals a dynamic and complex interaction that recent studies are beginning to unravel.

PMID: 17501916 [PubMed - in process]

Host Cell-Directed Interactions with Toxo

An article by Jay Radke et al., can be found in this month's issue of Microbe, v2 no. 5, p. 245

Wednesday, May 16, 2007

Atomic resolution insight into host cell recognition by Toxoplasma gondii

EMBO J. 2007 May 10; [Epub ahead of print]

Atomic resolution insight into host cell recognition by Toxoplasma gondii

Blumenschein TM, Friedrich N, Childs RA, Saouros S, Carpenter EP, Campanero-Rhodes MA, Simpson P, Chai W, Koutroukides T, Blackman MJ, Feizi T, Soldati-Favre D, Matthews S.

Division of Molecular Biosciences, Imperial College London, London, UK.

The obligate intracellular parasite Toxoplasma gondii, a member of the phylum Apicomplexa that includes Plasmodium spp., is one of the most widespread parasites and the causative agent of toxoplasmosis. Micronemal proteins (MICs) are released onto the parasite surface just before invasion of host cells and play important roles in host cell recognition, attachment and penetration. Here, we report the atomic structure for a key MIC, TgMIC1, and reveal a novel cell-binding motif called the microneme adhesive repeat (MAR). Using glycoarray analyses, we identified a novel interaction with sialylated oligosaccharides that resolves several prevailing misconceptions concerning TgMIC1. Structural studies of various complexes between TgMIC1 and sialylated oligosaccharides provide high-resolution insights into the recognition of sialylated oligosaccharides by a parasite surface protein. We observe that MAR domains exist in tandem repeats, which provide a highly specialized structure for glycan discrimination. Our work uncovers new features of parasite-receptor interactions at the early stages of host cell invasion, which will assist the design of new therapeutic strategies.

PMID: 17491595 [PubMed - as supplied by publisher]

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Thursday, May 10, 2007

Molecular evolution of the vesicle coat component betaCOP in Toxo

Mol Phylogenet Evol. 2007 Mar 24; [Epub ahead of print]

Molecular evolution of the vesicle coat component betaCOP in Toxoplasma gondii

Smith SS, Pfluger SL, Hjort E, McArthur AG, Hager KM.

Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556-0369, USA; Center for Global Health and Infectious Disease, University of Notre Dame, Notre Dame, IN 146556-0369, USA.

Coatomer coated (COPI) vesicles play a pivotal role for multiple membrane trafficking steps throughout the eukaryotic cell. Our focus is on betaCOP, one of the most well known components of the COPI multi-protein complex. Amino acid differences in betaCOP may dictate functional divergence across species during the course of evolution, especially with regards to the evolutionary pressures on obligate intracellular parasites. A bioinformatic analysis of betaCOP amino acid sequences was conducted for 49 eukaryotic species. Cloning and sequence analysis of the Toxoplasma gondii betaCOP homologue revealed several amino acid insertions unique to T. gondii and one C-terminal insertion that is unique to apicomplexan parasites. These findings led us to investigate the possibility that betaCOP experienced functional divergence during the course of its evolution. Bayesian phylogenetic analysis revealed a tree consistent with pan eukaryote distribution and long-branch lengths were observed among the apicomplexans. Further analysis revealed that kinetoplast betaCOP underwent the most amount of change, leading to perhaps an overall change of function. In comparison, T. gondii exhibited subtle yet specific amino acid changes. The amino acid substitutions did not occur in the same places as other lineages, suggesting that TgbetaCOP has a role specific to the apicomplexans. Our work identifies 48 residues that are likely to be functionally important when comparing apicomplexan, kinetoplastid, and fungal betaCOP.

PMID: 17485226 [PubMed - as supplied by publisher]