Tuesday, February 27, 2007

Toxoplasmosis: Review

Semin Fetal Neonatal Med. 2007 Feb 22; [Epub ahead of print]


Petersen E

Department of Infectious Diseases, Aarhus University Hospital, Aarhus, Denmark.

Infections with Toxoplasma gondii occur worldwide, but are especially prevalent in Europe, South America and Africa. The primary problem for the diagnosis of T. gondii infection is long-lasting IgM-antibodies, thus the presence of T. gondii-specific IgM-antibodies do not necessarily indicate an acute infection. The use of a Toxoplasma-specific IgG-avidity ratio, differentiated Western blots and two-dimensional immunoblots usually resolves diagnostic problems. There is no consensus on the best strategy to control congenital toxoplasmosis. Recent European prospective, but descriptive, studies including a meta-analysis of existing cohorts have found a surprisingly small effect on maternal-fetal transmission and clinical signs in children treated for T. gondii infection diagnosed by pre- and neonatal screening programmes. No randomised studies exist on the treatment of T. gondii infection in pregnant women and newborn children with congenital toxoplasmosis. Atovaquone is the most promising new drug available, but is not yet approved for use in pregnant women and small children.

PMID: 17321812 [PubMed - as supplied by publisher]

Effects of Toxoplasma gondii Infection on the Brain

Schizophr Bull. 2007 Feb 23; [Epub ahead of print]

Effects of Toxoplasma gondii Infection on the Brain

Carruthers VB, Suzuki Y

2Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, MI 48109.

Toxoplasma gondii, an intracellular protozoan parasite, can infect humans in 3 different ways: ingestion of tissue cysts, ingestion of oocysts, or congenital infection with tachyzoites. After proliferation of tachyzoites in various organs during the acute stage, the parasite forms cysts preferentially in the brain and establishes a chronic infection, which is a balance between host immunity and the parasite's evasion of the immune response. A variety of brain cells, including astrocytes and neurons, can be infected. In vitro studies using non-brain cells have demonstrated profound effects of the infection on gene expression of host cells, including molecules that promote the immune response and those involved in signal transduction pathways, suggesting that similar effects could occur in infected brain cells. Interferon-gamma is the essential mediator of the immune response to control T. gondii in the brain and to maintain the latency of chronic infection. Infection also induces the production of a variety of cytokines by microglia, astrocytes, and neurons, which promote or suppress inflammatory responses. The strain (genotype) of T. gondii, genetic factors of the host, and probably the route of infection and the stage (tachyzoite, cyst, or oocyst) of the parasite initiating infection all contribute to the establishment of a balance between the host and the parasite and affect the outcome of the infection.

PMID: 17322557 [PubMed - as supplied by publisher]

Characterization of truncated SAG2 secreted by yeast Pichia

Trop Biomed. 2006 Dec;23(2):186-93.

Characterisation of a truncated Toxoplasma gondii surface antigen 2 (SAG2) secreted by the methylotrophic yeast Pichia pastoris

Lau YL, Shamilah H, Fong MY

Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.

A truncated form of surface antigen 2 (SAG2) of the protozoan parasite Toxoplasma gondii was cloned and expressed in the methylotrophic yeast Pichia pastoris. This recombinant antigen, designated as recSAG2-N, contained only the N-terminal half of the native SAG2. The recSAG2-N was secreted by the Pichia pastoris into the culture supernatant, and it was harvested by using the trichloroacetic acid precipitation method. Specificity of recSAG2-N was evaluated in western blot assays. Fifty human serum samples, including 32 from confirmed cases of toxoplasmosis, were tested. Results from the assays showed that recSAG2-N reacted with sera from the toxoplasmosis cases only. In vivo experiments showed that serum from mice which received recSAG2-N reacted with the native SAG2 of T. gondii.

PMID: 17322821 [PubMed - in process]

Monday, February 26, 2007

Freeze-fracture study of the dynamics of Toxo parasitophorous vacuole development

Micron. 2007 Jan 20; [Epub ahead of print]

Freeze-fracture study of the dynamics of Toxoplasma gondii parasitophorous vacuole development

Lemgruber L, De Souza W, Vommaro RC

Laboratorio de Ultraestrutura Celular Hertha Meyer, Instituto de Biofisica Carlos Chagas Filho, Bloco G, CCS, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil.

Toxoplasma gondii resides in a nonfusogenic parasitophorous vacuole (PV), which provides a safe environment for parasite survival and replication. In this work, we used the freeze-fracture technique to analyze the PV during different times of T. gondii infection in an epithelial cell line. After a short time of interaction with host cell, T. gondii PV membrane already showed a significant quantity of intramembranous particles (IMPs)-293IMPs/mum(2). The IMP density evaluated did not vary until 6h of interaction. As the PV area enlarged with the progression of infection, the density of these particles increased, reaching a stable quantity in the order of 1100particles/mum(2). The IMPs were heterogeneous in size and were found distributed without any special pattern throughout the time of infection studied. The membrane lining the PV presented circular figures, which resembled vesicle fusion areas or attachments of the membranous tubular network, regions free from particles and small depressions, demonstrating to be a dynamic structure. IMPs were found in tubulo-vesicular structures present in the intravacuolar matrix, although rarely observed in elements of the intravacuolar network.

PMID: 17317194 [PubMed - as supplied by publisher]

Saturday, February 24, 2007

Toxo in Individuals With Schizophrenia: Association With Clinical and Demographic Factors and With Mortality

Schizophr Bull. 2007 Feb 20; [Epub ahead of print]

Toxoplasma gondii in Individuals With Schizophrenia: Association With Clinical and Demographic Factors and With Mortality

Dickerson F, Boronow J, Stallings C, Origoni A, Yolken R

The Stanley Research Center at the Sheppard Pratt Health System, 6501 North Charles Street, Baltimore, MD 21204.

Background: Increased rates of exposure to Toxoplasma gondii have been found in individuals with schizophrenia as compared with control groups, but the correlates of Toxoplasma exposure in schizophrenia have not been defined. Methods: We measured IgG class antibodies to Toxoplasma gondii in 358 individuals with schizophrenia. We correlated Toxoplasma antibody status with clinical and demographic variables and examined the effect of Toxoplasma seropositivity on mortality in a follow-up period of up to 5 years. Results: Individuals with schizophrenia who had serological evidence of Toxoplasma infection were more likely to be female but did not differ in age, race, total symptom score, or other demographic or clinical characteristics. However, we found that serological evidence of Toxoplasma was associated with a significantly increased risk of dying of natural causes during the follow-up period (Cox proportional hazard ratio of 4.70; 95% confidence interval, 1.27-17.31, P = .020) adjusted for age, gender, and other clinical and demographic variables. Conclusions: Toxoplasma infection may confer an increased risk for mortality from natural causes in schizophrenia. An understanding of the pathogenesis of Toxoplasma infections in individuals with schizophrenia might lead to new approaches to the management of this disorder.

PMID: 17314085 [PubMed - as supplied by publisher]

The Differential Agglutination (AC/HS) Test as a Diagnostic Aid in Toxoplasmic Lymphadenitis

J Clin Microbiol. 2007 Feb 21; [Epub ahead of print]

The Differential Agglutination (AC/HS) Test as a Diagnostic Aid in Toxoplasmic Lymphadenitis

Montoya JG, Berry A, Rosso F, Remington JS.

Department of Immunology and Infectious Diseases, Research Institute, Palo Alto Medical Foundation, Palo Alto, CA; Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA.

Lymphadenopathy (LN) is the most common clinical manifestation of acute acquired toxoplasma infection in humans. The diagnosis of toxoplasmic lymphadenitis is established by serologic methods and/or lymph node biopsy. In the United States, the AC/HS test has primarily been used in pregnant women as a component of the Toxoplasma Serological Profile (TSP), to distinguish between a recently acquired infection versus an infection acquired in the distant past. We studied the AC/HS test in patients with TL to define its usefulness in individuals presenting with LN and to determine its kinetics after the onset of LN. 109 consecutive patients (158 serum samples) diagnosed serologically and by lymph node biopsy as having TL were studied. Specific patterns in the AC/HS test were noted to be time dependent from the clinical onset of LN (COLN). Acute AC/HS patterns were observed in greater than 75% of patients who by history had developed their TL within 6 months. Acute patterns were not observed beyond month 12(th) except in a single patient in whom an acute pattern (400/800) persisted to month13th after COLN. Equivocal patterns were observed up to 36 months after COLN. Non-acute patterns were only observed in serum samples drawn at least 13 months after COLN. A non-acute pattern in an individual who has COLN of less than 12 months should suggest an etiology other than TL. In such cases, investigation for alternative causes including malignancy should be instigated.

PMID: 17314220 [PubMed - as supplied by publisher]

Friday, February 23, 2007

Toxo apicoplast, complete genome

Toxoplasma gondii apicoplast, complete genome

Thursday, February 22, 2007

New Toxo ATPases

Toxoplasma gondii PMCA-like calcium ATPase A1 (A1) mRNA, complete cds

Toxoplasma gondii golgi-ER-type, P-type ATPase (GERP) mRNA, complete cds

Toxoplasma gondii PMR1-like calcium ATPase (PMR1) mRNA, complete cds

Toxoplasma gondii PMCA-type calcium ATPase A2 (A2) mRNA, complete cds

Tuesday, February 20, 2007

ROP18 Is a Rhoptry Kinase Controlling the Intracellular Proliferation of Toxo

PLoS Pathog. 2007 Feb 16;3(2):e14 [Epub ahead of print]

ROP18 Is a Rhoptry Kinase Controlling the Intracellular Proliferation of Toxoplasma gondii

El Hajj H, Lebrun M, Arold ST, Vial H, Labesse G, Dubremetz JF.

Toxoplasma gondii is an obligate intracellular parasite for which the discharge of apical organelles named rhoptries is a key event in host cell invasion. Among rhoptry proteins, ROP2, which is the prototype of a large protein family, is translocated in the parasitophorous vacuole membrane during invasion. The ROP2 family members are related to protein-kinases, but only some of them are predicted to be catalytically active, and none of the latter has been characterized so far. We show here that ROP18, a member of the ROP2 family, is located in the rhoptries and re-localises at the parasitophorous vacuole membrane during invasion. We demonstrate that a recombinant ROP18 catalytic domain (amino acids 243-539) possesses a protein-kinase activity and phosphorylate parasitic substrates, especially a 70-kDa protein of tachyzoites. Furthermore, we show that overexpression of ROP18 in transgenic parasites causes a dramatic increase in intra-vacuolar parasite multiplication rate, which is correlated with kinase activity. Therefore, we demonstrate, to our knowledge for the first time, that rhoptries can discharge active protein-kinases upon host cell invasion, which can exert a long-lasting effect on intracellular parasite development and virulence.

PMID: 17305424 [PubMed - as supplied by publisher]

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See also:

PLoS Pathog. 2007 Feb 16;3(2):e16 [Epub ahead of print]

The Toxoplasma Kinase ROP18: An Active Member of a Degenerate Family

Sinai AP

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N(6)-benzyladenosine analogues as potential anti-toxoplasma agents

Biochem Pharmacol. 2007 Jan 21; [Epub ahead of print]

Synthesis, biological evaluation and molecular modeling studies of N(6)-benzyladenosine analogues as potential anti-toxoplasma agents

Kim YA, Sharon A, Chu CK, Rais RH, Al Safarjalani ON, Naguib FN, El Kouni MH

University of Georgia College of Pharmacy, Athens, GA 30602, United States.

Toxoplasma gondii is an opportunistic pathogen responsible for toxoplasmosis. T. gondii is a purine auxotroph incapable of de novo purine biosynthesis and depends on salvage pathways for its purine requirements. Adenosine kinase (EC. is the major enzyme in the salvage of purines in these parasites. 6-Benzylthioinosine and analogues were established as "subversive substrates" for the T. gondii, but not for the human adenosine kinase. Therefore, these compounds act as selective anti-toxoplasma agents. In the present study, a series of N(6)-benzyladenosine analogues were synthesized from 6-chloropurine riboside with substituted benzylamines via solution phase parallel synthesis. These N(6)-benzyladenosine analogues were evaluated for their binding affinity to purified T. gondii adenosine kinase. Furthermore, the anti-toxoplasma efficacy and host toxicity of these compounds were tested in cell culture. Certain substituents on the aromatic ring improved binding affinity to T. gondii adenosine kinase when compared to the unsubstituted N(6)-benzyladenosine. Similarly, varying the type and position of the substituents on the aromatic ring led to different degrees of potency and selectivity as anti-toxoplasma agents. Among the synthesized analogues, N(6)-(2,4-dimethoxybenzyl)adenosine exhibited the most favorable anti-toxoplasma activity without host toxicity. The binding mode of the synthesized N(6)-benzyladenosine analogues were characterized to illustrate the role of additional hydrophobic effect and van der Waals interaction within an active site of T. gondii adenosine kinase by induced fit molecular modeling.

PMID: 17306769 [PubMed - as supplied by publisher]

Maternal-fetal transmission of Toxo in interferon-gamma deficient pregnant mice

Parasitol Int. 2007 Jan 24; [Epub ahead of print]

Maternal-fetal transmission of Toxoplasma gondii in interferon-gamma deficient pregnant mice

Shiono Y, Mun HS, He N, Nakazaki Y, Fang H, Furuya M, Aosai F, Yano A

Department of Infection and Host Defense, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.

Toxoplasma gondii infection is generally asymptomatic in immunocompetent persons but can be life-threatening in immunocompromised persons and for fetuses in the case of maternal-fetal transmission. The effect of interferon (IFN)-gamma, which plays a crucial role in the protective immunity against T. gondii infection, on maternal-fetal transmission of T. gondii was analyzed by quantitative competitive polymerase chain reaction targeting T. gondii-specific SAG1 gene. T. gondii loads were obvious in uterus and placenta of wild type (WT) C57BL/6 (B6, susceptible strain) but not BALB/c (resistant strain) pregnant mice. Higher levels of T. gondii were detected in uterus and placenta of IFN-gamma knock-out (GKO) B6 and BALB/c than in those of WT mice. Furthermore, T. gondii was detected in fetus of GKO B6 but not GKO BALB/c, WT B6, or WT BALB/c mice. Thus, not only IFN-gamma but also genetic susceptibility to T. gondii infection was important for the protective immunity of maternal-fetal transmission of T. gondii to fetus via placenta. T. gondii-infected WT mice displayed a low delivery rate with high IFN-gamma production, whereas infected GKO mice did not. Additionally, mean body weight of neonates from T. gondii-infected GKO BALB/c pregnant mice was significantly lower than that of unaborted neonates from WT BALB/c pregnant mice, suggesting the effects of T. gondii infection on intrauterine growth retardation of fetus in pregnant GKO mice.

PMID: 17307382 [PubMed - as supplied by publisher]

Monday, February 19, 2007

Toxo: causing your migraines?

Am J Ther. 2007 January/February;14(1):63-105.

Recurrent Headache as the Main Symptom of Acquired Cerebral Toxoplasmosis in Nonhuman Immunodeficiency Virus-infected Subjects With no Lymphadenopathy: The Parasite May Be Responsible for the Neurogenic Inflammation Postulated as a Cause of Different Types of Headaches

Prandota J.

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Toxo Pneumonia in Immunocompetent Subjects

Clin Infect Dis. 2007 Mar 15;44(6):e62-6. Epub 2007 Feb 8.

Toxoplasma gondii Pneumonia in Immunocompetent Subjects: Case Report and Review

Eudes Leal F, Cavazzana CL, Franco de Andrade H Jr, Jimenez Galisteo A Jr, Silva de Mendonca J, Kallas EG.

Hospital do Servidor Publico Estadual de Sao Paulo, Sao Paulo, SP, Brazil.

Pulmonary toxoplasmosis is rare in immunocompetent subjects. Here, we describe a 41-year-old previously healthy male patient who presented to the emergency department of a hospital with a life-threatening case of pneumonia due to Toxoplasma gondii infection, which responded to specific therapy. Clinical and image-based findings overlap with those for atypical pneumonias, and toxoplasmosis should be considered in the differential diagnosis--especially if immunoglobulin M-specific antibodies are detected.

PMID: 17304443 [PubMed - in process]

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Saturday, February 17, 2007

The Toxo Parasitophorous Vacuole Membrane - REVIEW

J Eukaryot Microbiol. 2007 Jan-Feb;54(1):25-8.

The Toxoplasma gondii Parasitophorous Vacuole Membrane: Transactions Across the Border

Martin AM, Liu T, Lynn BC, Sinai AP.

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

The obligate intracellular protozoan Toxoplasma gondii establishes its replication permissive niche within the infected host cell. This niche, the parasitophorous vacuole (PV), is delimited from the host cell cytoplasm by the PV membrane (PVM). In this chapter we highlight the roles of the PVM in the remodeling of host cell architecture, nutrient acquisition, the manipulation of signaling, and touch upon the potential roles in the parasite developmental cycle. We further present the PVM as a unique and dynamic "organelle" found only within the infected cell where it is established outside the parent organism. Despite its importance little is known about the biology of the PVM. There has, however, been a recent renewal of interest in the PVM, the study of which has become more tractable with the application of both classical approaches as well as genomic and proteomic analyses. In this review we discuss the diverse activities associated with the PVM and present pressing questions that remain to be elucidated regarding this enigmatic organelle.

PMID: 17300514 [PubMed - in process]

Friday, February 16, 2007

Toxo cathepsins

Toxoplasma gondii cathepsin C3 mRNA, complete cds

Toxoplasma gondii cathepsin C2 mRNA, complete cds

Toxoplasma gondii cathepsin C1 mRNA, complete cds

Thursday, February 15, 2007

Protective activity against oocyst shedding in cats vaccinated with crude rhoptry proteins

Vet Parasitol. 2007 Feb 10; [Epub ahead of print]

Protective activity against oocyst shedding in cats vaccinated with crude rhoptry proteins of the Toxoplasma gondii by the intranasal route

Garcia JL, Navarro IT, Biazzono L, Freire RL, Junior JD, Cryssafidis AL, Bugni FM, Cunha IA, Hamada FN, Dias RC.

Protozoology laboratory, Departamento de Medicina Veterinaria Preventiva, Universidade Estadual de Londrina, Postal Box 6001, 86050-970 Londrina, PR, Brazil.

This study evaluated a vaccine made from crude rhoptry proteins of Toxoplasma gondii with Quil-A, which was administered to cats by the intranasal route. Eleven short-hair domestic cats were divided into four groups: G1 (n=3) received three doses (200mug/dose) of the rhoptry vaccine with Quil-A (20mug); G2 (n=3) received PBS with Quil-A (20mug); G3 (n=3) and G4 (n=2) received only PBS. Treatments were administered at days 0, 21, and 42 by the intranasal route. Challenge was done to G1, G2, and G3 animals with 600 cysts of the VEG strain on day 51 (challenge day); G4 animals were unchallenged. The anti-T. gondii IgG and IgA antibody levels from sera were measured by indirect enzyme-linked immunosorbent assay (ELISA). At challenge, two animals from G1 revealed antibody levels for both IgG and IgA; oocysts were not detected in feces of these two cats. There were no differences in hematological values between groups throughout the experiment (p>0.10). Preventable fractions were 67% in G1 and 0% in G2 and G3. Comparatively, G1 animals shed 89.3% and 90.8% less oocysts than G3 and G4, respectively. Two out of three cats were protected against T. gondii oocyst shedding when the rhoptry vaccine was administered by the intranasal route. This is the first study using crude rhoptry proteins as vaccine by the intranasal route in cats to evaluate protection against oocysts shedding.

PMID: 17296268 [PubMed - as supplied by publisher]

SAG2 locus and genetic analysis of Toxo isolates

Parasitol Res. 2007 Feb 13; [Epub ahead of print]

A new perspective on and re-assessment of SAG2 locus as the tool for genetic analysis of Toxoplasma gondii isolates

Fazaeli A, Ebrahimzadeh A.

Department of Medical Parasitology and Mycology, Medical School, Zahedan University of Medical Sciences, Mashahir Square, Zahedan, 98165, Iran.

SAG2 locus, the coding gene of the P22 protein, has been widely used for the molecular epidemiology of Toxoplasma gondii and characterization of the parasite isolates with two separate polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) processes. To re-assess the resolution power and suitability of this genetic marker for molecular characterization of the parasite isolates, a number of 27 Toxoplasma strains from different zymodeme patterns were used in the present study. Both codon and non-codon regions of the SAG2 locus of all 27 strains were amplified and subjected to sequencing and nucleotide alignment. Nucleotide variations clustered the three major genotypes (I, II and III). Some minor genotypes, unidentifiable by SAG2-RFLP, could be identified by sequence comparison. However, there were other genotypes that could not be differentiated from the major types due to having identical sequences. This suggests that a remarkable number of field isolates representing several minor types will be miss-clustered with the major types by using the traditional SAG2-PCR-RFLP method. It was concluded that this technique seems not to be suitable for Toxoplasma population study. Thus, the utilization of more variable markers and other discriminatory methods are also recommended.

PMID: 17297630 [PubMed - as supplied by publisher]

Toxo inhibits Fas/CD95-triggered cell death...

Cell Microbiol. 2007 Feb 7; [Epub ahead of print]

Toxoplasma gondii inhibits Fas/CD95-triggered cell death by inducing aberrant processing and degradation of caspase 8

Vutova P, Wirth M, Hippe D, Gross U, Schulze-Osthoff K, Schmitz I, Luder CG.

Institute for Medical Microbiology, Georg-August-University, Gottingen, Germany.

Ligation of the death receptor Fas/CD95 activates an apoptotic cascade and plays critical roles during infectious diseases. Previous work has established that infection with the intracellular parasite Toxoplasma gondii renders cells resistant to multiple inducers of apoptosis. However, the effect of T. gondii on the death receptor pathway is poorly characterized. Here we have determined the impact of the parasite on apoptosis in type I cells that transduce Fas/CD95 engagement via the death receptor pathway without the need of a mitochondrial amplification loop. The results have shown that T. gondii significantly reduced Fas/CD95-triggered apoptosis by impairing activation of the initiator caspase 8. Parasitic infection diminished the cellular amount of procaspase 8, resulting in its decreased recruitment to the death-inducing signalling complex and the impaired activation of effector caspases. Remarkably, downregulation of caspase 8 protein in T. gondii-infected cells also occurred in the absence of Fas/CD95 engagement and was associated with the appearance of non-canonical caspase 8 cleavage fragments. Distinct parasite proteins were associated with caspase 8 and its proteolytic fragments. These findings indicate that T. gondii aberrantly processes and finally degrades the initiator caspase 8, thereby, blocking Fas/CD95-mediated apoptosis which signals independently of the apoptogenic function of host cell mitochondria.

PMID: 17298390 [PubMed - as supplied by publisher]

Evolving characteristics of toxoplasmosis in HIV+ patients

Clin Microbiol Infect. 2007 Feb 12; [Epub ahead of print]

Evolving characteristics of toxoplasmosis in patients infected with human immunodeficiency virus-1: clinical course and Toxoplasma gondii-specific immune responses

Hoffmann C, Ernst M, Meyer P, Wolf E, Rosenkranz T, Plettenberg A, Stoehr A, Horst HA, Marienfeld K, Lange C.

University Hospital of Schleswig-Holstein, Campus Kiel, Kiel, Germany.

Toxoplasmic encephalitis (TE) is the most important opportunistic infection of the central nervous system in patients infected with human immunodeficiency virus (HIV)-1. This study evaluated the effect of highly active anti-retroviral therapy (HAART) and Toxoplasma gondii-specific immune responses on the occurrence of TE. The clinical characteristics of all patients diagnosed with TE in two centres since 1990 (n = 140) were analysed. Patients were grouped according to the date of diagnosis (period 1, 1990-1993; period 2, 1994-1996; period 3, 1997 onwards). Immune responses to T. gondii were evaluated in a subgroup (n = 12) by interferon (IFN)-gamma-specific ELISPOT tests. There were marked differences in the estimated Kaplan-Meier overall survival (OS), with a 1-year OS (5-year OS) of 41% (7%) in period 1, 56% (29%) in period 2, and 90% (78%) in period 3 (p <0.0001). In period 3, TE was found to be the first AIDS-defining illness more frequently than in earlier periods (74% vs. 38%, p 0.0002). Persistent neurological deficits caused by TE were present in 37% of the patients. Patients with an acute episode of TE or a TE relapse had significantly lower responses in the T. gondii-specific ELISPOT than patients who discontinued maintenance therapy and were relapse-free (p 0.0044). Survival of HIV patients with TE has improved markedly since the introduction of HAART, but persistent neurological deficits are often present in surviving patients. While preventive therapy remains essential, evaluation of T. gondii-specific immune responses may be an important step in improving estimates of the individual risk of TE and TE relapses.

PMID: 17298486 [PubMed - as supplied by publisher]

Wednesday, February 07, 2007

Vaccination as a control strategy against the coccidial parasites Eimeria, Toxo and Neospora

Parasitology. 2006 Oct;133 Suppl:S145-68.

Vaccination as a control strategy against the coccidial parasites Eimeria, Toxoplasma and Neospora

Innes EA, Vermeulen AN

Moredun Research Institute, Pentlands Science Park, Edinburgh EH26 OPZ, UK.

The protozoan parasites Eimeria spp. Toxoplasma gondii and Neospora caninum are significant causes of disease in livestock worldwide and T. gondii is also an important human pathogen. Drugs have been used with varying success to help control aspects of these diseases and commercial vaccines are available for all three groups of parasites. However, there are issues with increasing development of resistance to many of the anti-coccidial drugs used to help control avian eimeriosis and public concerns about the use of drugs in food animals. In addition there are no drugs available that can act against the tissue cyst stage of either T. gondii or N. caninum and thus cure animals or people of infection. All three groups of parasites multiply within the cells of their host species and therefore cell mediated immune mechanisms are thought to be an important component of host protective immunity. Successful vaccination strategies for both Eimeria and Toxoplasma have relied on using a live vaccination approach using attenuated parasites which allows correct processing and presentation of antigen to the host immune system to stimulate appropriate cell mediated immune responses. However, live vaccines can have problems with safety, short shelf-life and large-scale production; therefore there is continued interest in devising new vaccines using defined recombinant antigens. The major challenges in devising novel vaccines are to select relevant antigens and then present them to the immune system in an appropriate manner to enable the induction of protective immune responses. With all three groups of parasites, vaccine preparations comprising antigens from the different life cycle stages may also be advantageous. In the case of Eimeria parasites there are also problems with strain-specific immunity therefore a cocktail of antigens from different parasite strains may be required. Improving our knowledge of the different parasite transmission routes, host-parasite relationships, disease pathogenesis and determining the various roles of the host immune response being at times host-protective, parasite protective and in causing immunopathology will help to tailor a vaccination strategy against a particular disease target. This paper discusses current vaccination strategies to help combat infections with Eimeria, Toxoplasma and Neospora and recent research looking towards developing new vaccine targets and approaches.

PMID: 17274844 [PubMed - in process]

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Expression of Cryptosporidium glycoprotein gp40/15 in Toxo

Mol Biochem Parasitol. 2007 Jan 7; [Epub ahead of print]

Stable expression of Cryptosporidium parvum glycoprotein gp40/15 in Toxoplasma gondii

O'connor RM, Wanyiri JW, Wojczyk BS, Kim K, Ward H

Division of Geographic Medicine and Infectious Diseases, Tufts-New England Medical Center, Boston, MA, United States.

Cryptosporidium is a cause of diarrheal disease worldwide. Parasite glycoproteins involved in invasion of Cryptosporidium into host cells have been investigated as possible targets for effective interventions against this parasite. One of these, Cpgp40/15, is expressed as a precursor protein that is cleaved by a parasite-derived furin-like protease activity into gp15, a glycophosphatidyl inositol anchored surface protein, and gp40, that associates with gp15 and binds to host cells. Investigation of the functions of these glycoproteins requires an expression system that can produce similar glycosylation patterns to the native antigens. Previous work demonstrated that Cpgp40/15 transiently expressed in Toxoplasma gondii was appropriately localized and glycosylated. In this study, T. gondii stable transfectants expressing gp40/15, gp15, gp40 and hemagglutinin (HA) tagged gp40 were generated. T. gondii recombinant gp40HA and gp40/15 (recTggp40HA and recTggp40/15) were isolated from infected cells by HA affinity chromatography and Helix pomatia lectin affinity chromatography, respectively. Mass spectrometry confirmed that recTggp40-HA and native Cpgp40 were similarly glycosylated. Like native Cpgp40/15, recTggp40/15 could be cleaved into the gp40 and gp15 products by human furin or by a furin-like protease activity in T. gondii tachyzoite lysates. However, processing was inefficient in intact tachyzoites. Unlike the N-terminus of native Cpgp40/15, which appears to be processed following signal peptide cleavage, the N-terminus of recTggp40/15 began at the predicted signal sequence cleavage site, 11 amino acids upstream of the N-terminus of native Cpgp40. The ability to express and isolate appropriately glycosylated Cryptosporidium glycoproteins will enable further investigations into host-parasite interactions of this important pathogen.

PMID: 17275106 [PubMed - as supplied by publisher]

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SAG1 is Not Required for Acute Ocular Toxoplasmosis in Mice

Infect Immun. 2007 Feb 5; [Epub ahead of print]

The SAG1 Toxoplasma Surface Protein is Not Required for Acute Ocular Toxoplasmosis in Mice

Charles E, Callegan MC, Blader IJ.

Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104.

The SAG1 Toxoplasma surface protein stimulates acute ileitis. To test if SAG1 is also important in the eye, wild-type or SAG1 knockout parasites were intravitreally injected into mice. No differences in retinal damage or parasite growth were observed indicating that, unlike the intestine, factors besides SAG1 are important for retinal damage.

PMID: 17283084 [PubMed - as supplied by publisher]

Source of host-protective regulatory IL-10 during intracellular protozoan infection

J Exp Med. 2007 Feb 5; [Epub ahead of print]

Conventional T-bet+Foxp3- Th1 cells are the major source of host-protective regulatory IL-10 during intracellular protozoan infection.

Jankovic D, Kullberg MC, Feng CG, Goldszmid RS, Collazo CM, Wilson M, Wynn TA, Kamanaka M, Flavell RA, Sher A.

Immunobiology Section and 2Immunopathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD 20892.

Although interferon gamma (IFN-gamma) secretion is essential for control of most intracellular pathogens, host survival often also depends on the expression of interleukin 10 (IL-10), a cytokine known to counteract IFN-gamma effector functions. We analyzed the source of regulatory IL-10 in mice infected with the protozoan parasite Toxoplasma gondii. Unexpectedly, IFN-gamma-secreting T-bet(+)Foxp3(-) T helper type 1 (Th1) cells were found to be the major producers of IL-10 in these animals. Further analysis revealed that the same IL-10(+)IFN-gamma(+) population displayed potent effector function against the parasite while, paradoxically, also inducing profound suppression of IL-12 production by antigen-presenting cells. Although at any given time point only a fraction of the cells appeared to simultaneously produce IL-10 and IFN-gamma, IL-10 production could be stimulated in IL-10(-)IFN-gamma(+) cells by further activation in vitro. In addition, experiments with T. gondii-specific IL-10(+)IFN-gamma(+) CD4 clones revealed that although IFN-gamma expression is imprinted and triggered with similar kinetics regardless of the state of Th1 cell activation, IL-10 secretion is induced more rapidly from recently activated than from resting cells. These findings indicate that IL-10 production by CD4(+) T lymphocytes need not involve a distinct regulatory Th cell subset but can be generated in Th1 cells as part of the effector response to intracellular pathogens.

PMID: 17283209 [PubMed - as supplied by publisher]

Monday, February 05, 2007

Toxo sugar transporter (ST1) mRNA

Toxoplasma gondii sugar transporter (ST1) mRNA, complete cds

Ligands for Dihydrofolate Reductase from Toxo Inspired by Structural Analysis

J Med Chem. 2007 Feb 2; [Epub ahead of print]

Highly Efficient Ligands for Dihydrofolate Reductase from Cryptosporidium hominis and Toxoplasma gondii Inspired by Structural Analysis.

Pelphrey PM, Popov VM, Joska TM, Beierlein JM, Bolstad ES, Fillingham YA, Wright DL, Anderson AC.

Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, and Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269.

The search for effective therapeutics for cryptosporidiosis and toxoplasmosis has led to the discovery of novel inhibitors of dihydrofolate reductase (DHFR) that possess high ligand efficiency: compounds with high potency and low molecular weight. Detailed analysis of the crystal structure of dihydrofolate reductase-thymidylate synthase from Cryptosporidium hominis and a homology model of DHFR from Toxoplasma gondii inspired the synthesis of a new series of compounds with a propargyl-based linker between a substituted 2,4-diaminopyrimidine and a trimethoxyphenyl ring. An enantiomerically pure compound in this series exhibits IC50 values of 38 and 1 nM against C. hominis and T. gondii DHFR, respectively. Improvements of 368-fold or 5714-fold (C. hominis and T. gondii) relative to trimethoprim were generated by synthesizing just 14 new analogues and by adding only a total of 52 Da to the mass of the parent compound, creating an efficient ligand as an excellent candidate for further study.

PMID: 17269758 [PubMed - as supplied by publisher]

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1,25(OH)2D3 inhibits growth of Toxo

J Steroid Biochem Mol Biol. 2007 Jan 30; [Epub ahead of print]

1,25(OH)2D3 inhibits in vitro and in vivo intracellular growth of apicomplexan parasite Toxoplasma gondii.

Rajapakse R, Uring-Lambert B, Andarawewa KL, Rajapakse RP, Abou-Bacar A, Marcellin L, Candolfi E.

Institut de Parasitologie et de Pathologie et Tropicale, de la Faculte de Medecine, EA 3950 Interactions Cellulaires et Moleculaires Hote-Parasite, 3 rue Koeberle, 67000 Strasbourg, France.

The hormonal form of vitamin D, 1,25-dyhydroxyvitamin D3 (1,25(OH)2D3), is implicated in a wide range of functions other than its classical role in calcium and phosphorous homeostasis. When Toxoplasma gondii-infected BALB/c mice were treated with 1,25(OH)2D3, they succumb to death sooner than their counterparts. But they showed less parasite burden in tissues which was further supported by mild pathological lesions. As an effort to understand the physiological mechanism for the above observation an in vitro study was performed. Fewer parasites were observed when 1,25(OH)2D3 pre-treated murine intestinal epithelial cells were challenged with parasites. Moreover, the observed inhibition was dose-dependent and had a maximum effect with 10(-7)M of 1,25(OH)2D3. However, no observable difference was observed, when pre-incubated parasites were added to cells suggesting that the observed inhibition was a result of an effect from 1,25(OH)2D3 on Toxoplasma intracellular growth. Our data support the notion that 1,25(OH)2D3 may inhibit intra cellular T. gondii parasite proliferation in vivo and in vitro.

PMID: 17270431 [PubMed - as supplied by publisher]

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New Drugs and Drug Targets Against Apicomplexans

Current Drug Targets
Volume 8, Number 1, January 2007

New Drugs and Drug Targets for Human Diseases Caused by Apicomplexan Parasites

This theme issue of CDT brings together a number of leading experts in the field of drug (target) discovery against human apicomplexan parasites and highlights major current concepts in this field.

Table of Contents


Editorial [Hot Topic: New Drugs and Drug Targets for Human Diseases Caused by Apicomplexan Parasites (Guest Editor: Frank Seeber)] pp. 1-2(2) Author: Seeber, Frank

Isoprenoid Biosynthesis of the Apicoplast as Drug Target pp. 3-13(11) Authors: Wiesner, Jochen; Jomaa, Hassan

Fatty Acid Biosynthesis as a Drug Target in Apicomplexan Parasites pp. 15-30(16) Authors: Goodman, C. D.; McFadden, G. I.

Targeting Purine and Pyrimidine Metabolism in Human Apicomplexan Parasites pp. 31-47(17) Author: Hyde, John E.

Mitochondrial Drug Targets in Apicomplexan Parasites pp. 49-60(12) Authors: Mather, Michael W.; Henry, Karl W.; Vaidya, Akhil B.

Targeting Invasion and Egress: From Tools to Drugs? pp. 61-74(14) Authors: Morgan, R. E.; Evans, K M.; Patterson, S.; Catti, F.; Ward, G. E.; Westwood, N. J.

Targeting Nutrient Uptake Mechanisms in Plasmodium pp. 75-88(14) Authors: Kirk, Kiaran; Saliba, Kevin J.

Thursday, February 01, 2007

Evaluation of the immune response induced by multiantigenic DNA vaccine encoding SAG1 and ROP2

Parasitol Res. 2007 Jan 31; [Epub ahead of print]

Evaluation of the immune response induced by multiantigenic DNA vaccine encoding SAG1 and ROP2 of Toxoplasma gondii and the adjuvant properties of murine interleukin-12 plasmid in BALB/c mice.

Zhang J, He S, Jiang H, Yang T, Cong H, Zhou H, Zhang J, Gu Q, Li Y, Zhao Q.

Department of Parasitology, Medical School, Shandong University, No. 44 Wenhuaxi Road, Jinan, Shandong, 250012, People's Republic of China, shenyi.he@hotmail.com.

The heavy incidence and severe or lethal damages of toxoplasmosis clearly indicate the need for the development of a more effective vaccine. In the present study, we constructed a multiantigenic DNA vaccine, eukaryotic plasmid pcDNA3.1-SAG1-ROP2, expressing surface protein SAG1 and rhoptry protein ROP2 of Toxoplasma gondii, and examined the expression ability of the DNA vaccine in HeLa cells by Western blot. Afterwards, we investigated the efficacy of pcDNA3.1-SAG1-ROP2 with or without co-administration of a plasmid encoding murine interleukin-12 (pIL-12) as a genetic adjuvant to protect Bagg albino/c mice against toxoplasmosis. After T. gondii RH strain challenge, mice immunized with pcDNA3.1-SAG1-ROP2 displayed significant high survival rates. Moreover, the protection was markedly enhanced by pIL-12 co-administration. The results of lymphocyte proliferation assay, cytokine, and antibody determinations show that mice immunized with pcDNA3.1-SAG1-ROP2 elicited stronger humoral and Th1-type cellular immune responses than those immunized with single-gene plasmids, empty plasmid, or phosphate-buffered saline. Furthermore, co-immunization with IL-12 genes resulted in a dramatic enhancement of these responses. Our study indicates that the introduction of multiantigenic DNA vaccine is more powerful and efficient than single-gene vaccine, and the co-delivery of pIL-12 further enhanced the potency of multiantigenic DNA vaccine.

PMID: 17265053 [PubMed - as supplied by publisher]