The Synaptic Leap

Am J Trop Med Hyg. 2010 Mar;82(3):464-5.

Annual burden of ocular toxoplasmosis in the United States

Jones JL, Holland GN.

Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at University of California at Los Angeles, Los Angeles, California.

Toxoplasmosis is the most common retinal infection in the United States, and it can severely impact vision. We used data from population-based studies, outbreaks, and the U.S. census to estimate the burden of Toxoplasma gondii infection and ocular toxoplasmosis. We estimate that 1,075,242 persons are infected with T. gondii, 21,505 persons have ocular lesions (both asymptomatic and symptomatic), and 4,839 (range = 2,150-7,527) persons develop symptomatic ocular toxoplasmosis each year in the United States. Toxoplasmosis contributes a significant burden to eye disease in the United States.

PMID: 20207874 [PubMed - in process]

Int J Clin Rheumtol. 2010 Feb 1;5(1):59-74.

Infection in systemic lupus erythematosus: friend or foe?

Francis L, Perl A.

Division of Rheumatology, Department of Medicine State University of New York, College of Medicine 750 East Adams Street Syracuse, New York 13210, USA.

Infectious agents have long been implicated in the pathogenesis of systemic lupus erythematosus. Common viruses, such as the Epstein-Barr virus, transfusion transmitted virus, parvovirus and cytomegalovirus, have an increased prevalence in patients with systemic lupus erythematosus. They may contribute to disease pathogenesis through triggering autoimmunity via structural or functional molecular mimicry, encoding proteins that induce cross-reactive immune responses to self antigens or modulate antigen processing, activation, or apoptosis of B and T cells, macrophages or dendritic cells. Alternatively, some infectious agents, such as malaria, Toxoplasma gondii and Helicobacter pylori, may have a protective effect. Vaccinations may play dual roles by protecting against friend and foe alike.

PMID: 20209114 [PubMed]

Nat Methods. 2010 Mar 7. [Epub ahead of print]

Toxoplasma secreting Cre recombinase for analysis of host-parasite interactions

Koshy AA, Fouts AE, Lodoen MB, Alkan O, Blau HM, Boothroyd JC.

[1] Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA. [2] Division of Infectious Disease, Department of Internal Medicine, Stanford University School of Medicine, Stanford, California, USA.

We describe a Toxoplasma gondii strain that will permit the use of site-specific recombination to study the host-parasite interactions of this organism. This Toxoplasma strain efficiently injects a Cre fusion protein into host cells. In a Cre-reporter cell line, a single parasite invasion induced Cre-mediated recombination in 95% of infected host cells. By infecting Cre-reporter mice with these parasites, we also monitored host-cell infection in vivo.

PMID: 20208532 [PubMed - as supplied by publisher]

Trends Parasitol. 2010 Mar 2. [Epub ahead of print]

Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention

Elmore SA, Jones JL, Conrad PA, Patton S, Lindsay DS, Dubey JP.

Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 1601 Campus Delivery, Fort Collins, CO 80523, USA.

Toxoplasma gondii is a parasite of birds and mammals. Cats are the only definitive host and thus the only source of infective oocysts, but other mammals and birds can develop tissue cysts. Although feline infections are typically asymptomatic, infection during human pregnancy can cause severe disease in the fetus. Cat owners can reduce their pets' exposure risk by keeping all cats indoors and not feeding them raw meat. Humans usually become infected through ingestion of oocyst-contaminated soil and water, tissue cysts in undercooked meat, or congenitally. Because of their fastidious nature, the passing of non-infective oocysts, and the short duration of oocyst shedding, direct contact with cats is not thought to be a primary risk for human infection. Copyright © 2010 Elsevier Ltd. All rights reserved.

PMID: 20202907 [PubMed - as supplied by publisher]

Proc Biol Sci. 2010 Mar 3. [Epub ahead of print]

DNA topoisomerases in apicomplexan parasites: promising targets for drug discovery

García-Estrada C, Prada CF, Fernández-Rubio C, Rojo-Vázquez F, Balaña-Fouce R.

Departamento de Ciencias Biomédicas (INTOXCAL), Universidad de León, , Campus de Vegazana s/n, 24071 León, Spain.

The phylum Apicomplexa includes a large group of protozoan parasites responsible for a wide range of animal and human diseases. Destructive pathogens, such as Plasmodium falciparum and Plasmodium vivax, causative agents of human malaria, Cryptosporidium parvum, responsible of childhood diarrhoea, and Toxoplasma gondii, responsible for miscarriages and abortions in humans, are frequently associated with HIV immunosuppression in AIDS patients. The lack of effective vaccines, along with years of increasing pressure to eradicate outbreaks with the use of drugs, has favoured the formation of multi-drug resistant strains in endemic areas. Almost all apicomplexan of medical interest contain two endosymbiotic organelles that contain their own mitochondrial and apicoplast DNA. Apicoplast is an attractive target for drug testing because in addition to harbouring singular metabolic pathways absent in the host, it also has its own transcription and translation machinery of bacterial origin. Accordingly, apicomplexan protozoa contain an interesting mixture of enzymes to unwind DNA from eukaryotic and prokaryotic origins. On the one hand, the main mechanism of DNA unwinding includes the scission of one-type I-or both DNA strands-type II eukaryotic topoisomerases, establishing transient covalent bonds with the scissile end. These enzymes are targeted by camptothecin and etoposide, respectively, two natural drugs whose semisynthetic derivatives are currently used in cancer chemotherapy. On the other hand, DNA gyrase is a bacterial-borne type II DNA topoisomerase that operates within the apicoplast and is effectively targeted by bacterial antibiotics like fluoroquinolones and aminocoumarins. The present review is an update on the new findings concerning topoisomerases in apicomplexan parasites and the role of these enzymes as targets for therapeutic agents.

PMID: 20200034 [PubMed - as supplied by publisher]

Mucosal Immunol. 2010 Mar 3. [Epub ahead of print]

IL-10 production by CD4(+) effector T cells: a mechanism for self-regulation

Jankovic D, Kugler DG, Sher A.

Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.

The development of Th1 lymphocytes is essential for cell-mediated immunity and resistance against intracellular pathogens. However, if left unregulated, the same response can cause serious damage to host tissues and lead to mortality. A number of different paracrine regulatory mechanisms involving distinct myeloid and lymphoid subpopulations have been implicated in controlling excessive secretion of inflammatory cytokines by Th1 cells. Much of this work has focused on interleukin (IL)-10, a cytokine with broad anti-inflammatory properties, one of which is to counteract the function of Th1 lymphocytes. While studying the role of IL-10 in regulating immunopathology during infection with the intracellular parasite Toxoplasma gondii, we discovered that the host-protective IL-10 derives in an autocrine manner from conventional interferon-gamma (IFN-gamma)-producing T-bet(+) Foxp3(neg) Th1 cells. In the following review, we will discuss these findings that support the general concept that production of IL-10 is an important self-regulatory function of CD4(+) T lymphocytes.Mucosal Immunology advance online publication 3 March 2010. doi:10.1038/mi.2010.8.

PMID: 20200511 [PubMed - as supplied by publisher]

Int J Infect Dis. 2010 Feb 27. [Epub ahead of print]

Treatment of toxoplasmic lymphadenitis with co-trimoxazole: double-blind, randomized clinical trial

Alavi SM, Alavi L.

Joundishapour Infectious and Tropical Diseases Research Center, Infectious Disease Ward, Razi Hospital, Joundishapour University of Medical Sciences, No. 52, West 11 Avenue, Kianabad, Ahvaz, Iran.

BACKGROUND: Lymphadenitis is one of the presenting signs of toxoplasmosis. Co-trimoxazole (CTM) has a good therapeutic effect on ocular and cerebral infections caused by Toxoplasma gondii. Since this infection is endemic in Ahvaz and because of the lack of investigations into the therapeutic effects of CTM in toxoplasmic lymphadenitis (TL), this study was performed from 2005 to 2007 to determine the therapeutic effects of CTM on TL in Ahvaz. METHODS: Forty-six patients with TL were enrolled in this randomized, double-blind, placebo-controlled trial study. Diagnosis was based on clinical examination, serological tests (chemiluminescent), and histopathological examinations. Palpable lymph nodes, IgM >8IU, and follicular hyperplasia were defined as positive findings. Patients were randomly assigned to the comparison groups (23 patients in each group). The CTM patients were treated with 48mg/kg/day CTM divided into two doses, for 1 month. The placebo patients were treated with placebo for 1 month. The primary endpoint for treatment response was 1 month. Follow-up with physical and serological examinations occurred at 6 months. The secondary endpoint was at 6 months. Clinical response was defined as no palpable lymph nodes and serological response as IgM <6IU; a patient was cured if the lymph nodes were no longer palpable and IgM was <6IU. Results were analyzed using SPSS software and the Chi-square test. RESULTS: At the end of treatment, a clinical response was observed in 15 (65.2%) in the CTM group and five (21.7%) in the placebo group. A serological response was seen in 65.2% of the CTM group and 13.0% of the placebo group. The cure rate was 65.2% in the CTM group and 13.1% in the placebo group. There was a significant difference in therapeutic effect between the two groups (52.2%, 95% confidence interval 32.1-72%, p<0.001). There was no difference in the site of infection between the two groups (p>0.05). CONCLUSION: CTM has a good therapeutic effect in TL and may be used in selected patients for whom treatment is required. Copyright © 2010 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

PMID: 20194044 [PubMed - as supplied by publisher]

Infect Immun. 2010 Mar 1. [Epub ahead of print]

CCR7 dependent immunity during acute Toxoplasma gondii infection

Noor S, Habashy AS, Nance JP, Clark RE, Nemati K, Carson MJ, Wilson EH.

Division of Biomedical Sciences, University of California, Riverside, CA 92521, USA.

The chemokine receptor CCR7 is a well established homing receptor for dendritic cells and T cells. Interactions with its ligands CCL19 and CCL21 facilitate priming of immune responses in lymphoid tissue yet CCR7-independent immune responses can be generated in the presence of sufficient antigen. In these studies we investigated the role of CCR7 signaling in the generation of protective immune responses to the intracellular protozoan parasite, Toxoplasma gondii. Results demonstrate a significant increase in the expression of CCL19, CCL21 and CCR7 in peripheral and CNS tissue over the course of infection. Unexpectedly, despite the presence of abundant antigen, CCR7 was an absolute requirement for protective immunity to T. gondii as CCR7(-/-) mice succumbed to the parasite early in the acute phase of infection. Although serum levels of IL-12, IL-6, TNF-alpha, and IL-10 remained unchanged there was a significant decrease in CCL2/MCP-1 and inflammatory monocyte recruitment to the site of infection. In addition, CCR7(-/-) mice failed to produce sufficient IFN-gamma, a critical Th1 associated effector cytokine required to control parasite replication. As a result there was increased parasite dissemination and a significant increase in parasite burden in the lung, liver and brains of infected mice. Adoptive transfer experiments revealed that expression of CCR7 on the T cell compartment alone is sufficient to enable T cell priming, increase IFN-gamma production and allow survival of CCR7(-/-) mice. These data demonstrate an absolute requirement for T cell expression of CCR7 for the generation of protective immune responses to Toxoplasma infection.

PMID: 20194594 [PubMed - as supplied by publisher]

Vaccine. 2010 Feb 25. [Epub ahead of print]

Prime and boost immunization with influenza and adenovirus encoding the Toxoplasma gondii surface antigen 2 (SAG2) induces strong protective immunity

Machado AV, Caetano BC, Barbosa RP, Salgado AP, Rabelo RH, Garcia CC, Bruna-Romero O, Escriou N, Gazzinelli RT.

Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte 31270-910, MG, Brazil; Centro de Pesquisas René Rachou, FIOCRUZ, Belo Horizonte 30190-002, MG, Brazil.

In this work, we explored an original vaccination protocol using recombinant influenza and adenovirus. We constructed recombinant influenza viruses harboring dicistronic NA segments containing the surface antigen 2 (SAG2) from Toxoplasma gondii under control of the duplicated 3' promoter. Recombinant influenza viruses were able to drive the expression of the foreign SAG2 sequence in cell culture and to replicate efficiently both in cell culture and in lungs of infected mice. In addition, mice primed with recombinant influenza virus and boosted with a recombinant adenovirus encoding SAG2 elicited both humoral and cellular immune responses specific for SAG2. Moreover, when immunized animals were challenged with the cystogenic P-Br strain of T. gondii, they displayed up to 85% of reduction in parasite burden. These results demonstrate the potential use of recombinant influenza vectors harboring the dicistronic segments in the development of vaccines against infectious diseases. Copyright © 2010 Elsevier Ltd. All rights reserved.

PMID: 20189485 [PubMed - as supplied by publisher]

Parasitol Res. 2010 Feb 26. [Epub ahead of print]

Evaluation of drug effects on Toxoplasma gondii nuclear and plastid DNA replication using real-time PCR

Zhao Q, Zhang M, Hong L, Zhou K, Lin Y.

School of Life Sciences, Xiamen University, Xiamen, Fujian, China, 361005, zhaoqingxm@yahoo.cn.

Toxoplasma gondii Nicolle and Manceaux, 1908 is a unicellular protozoan that can infect a broad spectrum of organisms including humans. In addition to a nuclear genome, it also carries a circular DNA within a plastid-like organelle (apicoplast) and a linear genome within its mitochondria. The plastid organelle has been shown to be the target of various anti-parasitic drugs or antibiotics. To evaluate the effects of agents on the DNA replication of T. gondii, we tested six drugs (ciprofloxacin, acetylspiramycin, clindamycin, azithromycin, artemether, and sulfadiazine) on the parasite cultured in Hela cells. After drug treatment for 48 h, the parasite growth and DNA replication were evaluated and quantitated using TaqMan real-time quantitative PCR with oligonucleotide primers synthesized based on a gene from the apicoplast genome (ycf24, Genbank accession no. U87145) and a gene from the nuclear genome (uprt, Genbank accession no. U10246). Our results showed that ciprofloxacin was the most effective in inhibiting the replication of the plastid DNA after 48 h drug treatment, with a reduction of 22% in the copy number of the plastid DNA. Artemether was the most effective drug in suppressing the proliferation of tachyzoites. This study also demonstrates that real-time quantitative PCR is a simple and useful technique for monitoring parasite growth and DNA replication.

PMID: 20186551 [PubMed - as supplied by publisher]

Parasitol Res. 2010 Feb 23. [Epub ahead of print]

Toxoplasma gondii microneme protein 8 (MIC8) is a potential vaccine candidate against toxoplasmosis

Liu MM, Yuan ZG, Peng GH, Zhou DH, He XH, Yan C, Yin CC, He Y, Lin RQ, Song HQ, Zhu XQ.

Laboratory of Parasitology, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Street, Tianhe District, Guangzhou, Guangdong Province, 510642, People's Republic of China.

Microneme protein 8 (MIC8) is considered a new essential invasion factor in Toxoplasma gondii. In the present study, a deoxyribonucleic acid vaccine expressing MIC8 of T. gondii was constructed and the immune response it induced in Kunming mice was evaluated. The gene sequence encoding MIC8 was inserted into the eukaryotic expression vector pVAX I, and the pVAX-MIC8 expression plasmid was constructed, and the plasmid diluted with PBS to l00 mg/100 microl was injected into the Kunming mice muscularly. Levels of IgG antibody, gamma-interferon (IFN-gamma), interleukin-2 (IL-2), interleukin-4, and interleukin-10 were detected. The mice were challenged with tachyzoites of the virulent T. gondii RH strain at the 14th day after the last immunization to observe the survival time. The high level of IFN-gamma, IL-2, and IgG antibody indicated that mice vaccinated with recombinant pVAX-MIC8 plasmid could elicit strong cellular and humoral immune responses and showed a significantly increased survival time (10.3 +/- 0.9 days) compared with control mice which died within 5 days of challenge infection. These data demonstrate that the T. gondii MIC8 is a potential vaccine candidate against toxoplasmosis.

PMID: 20177910 [PubMed - as supplied by publisher]

Eukaryot Cell. 2010 Feb 19. [Epub ahead of print]

Use of the kinase inhibitor analog 1NM-PP1 reveals a role for Toxoplasma gondii CDPK1 in the invasion step

Sugi T, Kato K, Kobayashi K, Watanabe S, Kurokawa H, Gong H, Pandey K, Takemae H, Akashi H.

Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.

Toxoplasma gondii CDPK1 (TgCDPK1) was found to be the target of the toxoplasmocidal compound, 1NM-PP1. When TgCDPK1 was mutated at position 128 from glycine to methionine, resistance was gained. Inhibition of gliding motility without inhibition of micronemal secretion by 1NM-PP1 suggests a function for TgCDPK1 in gliding motility.

PMID: 20173034 [PubMed - as supplied by publisher]

Am J Pathol. 2010 Feb 18. [Epub ahead of print]

Removal of Toxoplasma gondii Cysts from the Brain by Perforin-Mediated Activity of CD8+ T Cells

Suzuki Y, Wang X, Jortner BS, Payne L, Ni Y, Michie SA, Xu B, Kudo T, Perkins S.

From the Department of Biomedical Sciences,* Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; the Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, Lexington, Kentucky; and the Department of Pathology, Stanford University School of Medicine, Stanford, California.

Chronic infection with Toxoplasma gondii is one of the most common parasitic infections in humans. Formation of tissue cysts is the basis of persistence of the parasite in infected hosts, and this cyst stage has generally been regarded as untouchable. Here we provide the first evidence that the immune system can eliminate T. gondii cysts from the brains of infected hosts when immune T cells are transferred into infected immunodeficient animals that have already developed large numbers of cysts. This T cell-mediated immune process was associated with accumulation of microglia and macrophages around tissue cysts. CD8(+) immune T cells possess a potent activity to remove the cysts. The initiation of this process by CD8(+) T cells does not require the production of interferon-gamma, the major mediator to prevent proliferation of tachyzoites during acute infection, but does require perforin. These results suggest that CD8(+) T cells induce elimination of T. gondii cysts through their perforin-mediated cytotoxic activity. Our findings provide a new mechanism of the immune system to fight against chronic infection with T. gondii and suggest a possibility of developing a novel vaccine to eliminate cysts from patients with chronic infection and to prevent the establishment of chronic infection after a newly acquired infection.

PMID: 20167872 [PubMed - as supplied by publisher]

Auton Neurosci. 2010 Feb 17. [Epub ahead of print]

Quantitative and morphometric changes of subpopulations of myenteric neurons in swines with toxoplasmosis

Odorizzi L, Moreira NM, Gonçalves GF, da Silva AV, Sant'ana DD, Araújo EJ.

Programa de Pós-Graduação em Ciência Animal, Universidade Paranaense, PR, Brazil.

The consequences of the infection caused by Toxoplasma gondii in myenteric neurons of the jejunum of swines reactive to NADH-diaphorase and NADPH-diaphorase were evaluated in this study. Ten 88-day-old mixed-breed swines (Pietrain and Wessex) were assigned into two groups: Control (n=5) and Experimental (n=5), which orally received 5000 sporulated oocysts from a genotype III T. gondii strain. After 30days, the animals were anesthetized, having part of their jejunum removed and stained with NADPH-diaphorase and NADH-diaphorase. NADPHd-p neurons (nitrergic) presented increase of the number of cells per ganglion and hypertrophy. The number of NADHd-p neurons (metabolic more active) and their nuclear area decreased. Copyright © 2010. Published by Elsevier B.V.

PMID: 20167543 [PubMed - as supplied by publisher]

J Biol Chem. 2010 Feb 17. [Epub ahead of print]

Structural and functional characterization of SporoSAG: A SAG2 related surface antigen from Toxoplasma gondii

Crawford J, Lamb E, Wasmuth J, Grujic O, Grigg ME, Boulanger MJ.

University of Victoria, Canada;

Toxoplasma gondii, the etiological agent of toxoplasmosis, utilizes stage specific expression of antigenically distinct glycosylphosphatidylinositol-tethered surface coat proteins to promote and establish chronic infection. Of the three infective stages of T. gondii, sporozoites are encapsulated in highly infectious oocysts that have been linked to large scale outbreaks of toxoplasmosis. SporoSAG is the dominant surface coat protein expressed on the surface of sporozoites. Using a bioinformatic approach, we show that SporoSAG (Surface Antigen Glycoprotein) clusters with the SAG2 subfamily of the SAG1 related superfamily (SRS) and is nonpolymorphic among the 11 haplogroups of T. gondii strains. In contrast to the immunodominant SAG1 protein expressed on tachyzoites, SporoSAG is non-immunogenic during natural infection. We report the 1.60 A resolution crystal structure of SporoSAG solved using cadmium single anomalous dispersion. SporoSAG crystallized as a monomer and displays unique features of the SRS beta sandwich fold relative to SAG1 and BSR4. Intriguingly, the structural diversity is localized to the upper sheets of the beta sandwich fold and may have important implications for dimerization and host cell ligand recognition. The structure of SporoSAG also reveals an unexpectedly acidic surface that contrasts with the previously determined SAG1 and BSR4 structures where a basic surface is predicted to play a role in binding negatively charged glycosaminoglycans. Our structural and functional characterization of SporoSAG provides a rationale for the evolutionary divergence of this key SRS family member.

PMID: 20164173 [PubMed - as supplied by publisher]

J Biol Chem. 2010 Feb 16. [Epub ahead of print]

MYST-family lysine acetyltransferase facilitates ataxia telangiectasia mutated (ATM) kinase-mediated DNA damage response in Toxoplasma gondii

Vonlaufen N, Naguleswaran A, Coppens I, Sullivan WJ Jr.

Indiana University School of Medicine, United States;

The MYST family of lysine acetyltransferases (KATs) function in a wide variety of cellular operations, including gene regulation and the DNA damage response. Here we report the characterization of the second MYST family KAT in the protozoan parasite Toxoplasma gondii (TgMYST-B). Toxoplasma causes birth defects and is an opportunistic pathogen in the immunocompromised, the latter due to its ability to convert into a latent cyst (bradyzoite). We demonstrate that TgMYST-B can gain access to the parasite nucleus and acetylate histones. Over-expression of recombinant, tagged TgMYST-B reduces growth rate in vitro and confers protection from a DNA alkylating agent. Expression of mutant TgMYST-B produced no growth defect and failed to protect against DNA damage. We demonstrate that cells over-expressing TgMYST-B have increased levels of ATM kinase and phosphorylated H2AX, and that TgMYST-B localizes to the ATM kinase gene. Pharmacological inhibitors of ATM kinase or KATs reverse the slow growth phenotype seen in parasites over-expressing TgMYST-B. These studies are the first to show that a MYST KAT contributes to ATM kinase gene expression, further illuminating the mechanism of how ATM kinase is upregulated to respond to DNA damage.

PMID: 20159970 [PubMed - as supplied by publisher]

J Ocul Biol Dis Infor. 2009 Dec 12;2(4):214-222.

The role of DNA microarrays in Toxoplasma gondii research, the causative agent of ocular toxoplasmosis

Brown KM, Blader IJ.

Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73034 USA.

Ocular toxoplasmosis, which is caused by the protozoan parasite Toxoplasma gondii, is the leading cause of retinochoroiditis. Toxoplasma is an obligate intracellular pathogen that replicates within a parasitophorous vacuole. Infections are initiated by digestion of parasites deposited in cat feces or in undercooked meat. Parasites then disseminate to target tissues that include the retina where they then develop into long-lived asymptomatic tissue cysts. Occasionally, cysts reactivate and growth of newly emerged parasites must be controlled by the host's immune system or disease will occur. The mechanisms by which Toxoplasma grows within its host cell, encysts, and interacts with the host's immune system are important questions. Here, we will discuss how the use of DNA microarrays in transcriptional profiling, genotyping, and epigenetic experiments has impacted our understanding of these processes. Finally, we will discuss how these advances relate to ocular toxoplasmosis and how future research on ocular toxoplasmosis can benefit from DNA microarrays.

PMID: 20157353 [PubMed]

J Neuroimmunol. 2010 Feb 13. [Epub ahead of print]

NF-kappaB1 contributes to T cell-mediated control of Toxoplasma gondii in the CNS

Harris TH, Wilson EH, Tait ED, Buckley M, Shapira S, Caamano J, Artis D, Hunter CA.

Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 380 S University Ave, Philadelphia, PA 19104, United States.

In this study, the role of NF-kappaB1 was examined during toxoplasmosis. While wildtype BALB/c mice generated protective responses, NF-kappaB1(-/-) mice developed Toxoplasmic encephalitis, characterized by increased parasite burden and necrosis in the brain. Susceptibility was primarily associated with a local decrease in the number of CD8(+) T cells and IFN-gamma production, while accessory cell function appeared intact in NF-kappaB1(-/-) mice. Consistent with these findings, T cell transfer studies revealed that NF-kappaB1(-/-) T cells provided SCID mice less protection than wildtype T cells. These results demonstrate an intrinsic role for NF-kappaB1 in T cell-mediated immunity to Toxoplasmagondii. Copyright © 2010 Elsevier B.V. All rights reserved.

PMID: 20156658 [PubMed - as supplied by publisher]

Parasitol Int. 2010 Feb 11. [Epub ahead of print]

Characterization of alpha-phosphoglucomutase isozymes from Toxoplasma gondii

Imada M, Kawashima S, Kanehisa M, Takeuchi T, Asai T.

Department of Tropical Medicine and Parasitology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.

The Toxoplasma gondii genome project has revealed two putative isoforms (TgPGM-I and TgPGM-II) of alpha-phosphoglucomutase (EC 5.4.2.2). We obtained recombinant proteins of these isoforms from the Beverley strain of T. gondii and characterized their properties, particularly the kinetic properties of these isoforms. The specific activities of TgPGM-I and TgPGM-II foralpha-D-glucose 1-phosphate were 338+/-9 and 84+/-6mumol/min/mg protein, respectively, at 37 degrees C under optimal conditions. The Kcat and Km values of TgPGM-I were 398 +/- 11 /s and 0.19+/-0.03mM and those for TgPGM-II were 93+/-7 /s and 3.53+/-0.91mM, respectively, foralpha-D-glucose 1-phosphate. Magnesium ions were the most effective divalent cations for both the enzyme activities. The maximum activities of both the enzymes were obtained in the presence of more than 0.2 mMalpha-D-glucose 1,6-bisphosphate. Although both enzymes were attached to thealpha-phosphohexomutase superfamily, amino acid sequence homology between TgPGM-I and TgPGM-II showed very low overall identity (25%). Noalpha-phosphomannomutase (EC 5.4.2.8) activity was detected for either enzyme. The data indicated that TgPGM-I, but not TgPGM-II, may play an important role in alpha-D-glucose 6-phosphate production. Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.

PMID: 20153838 [PubMed - as supplied by publisher]

Antimicrob Agents Chemother. 2010 Feb 9. [Epub ahead of print]

Dinitroaniline Activity in Toxoplasma gondii Expressing Wild-type or Mutant Alpha-Tubulin

Ma C, Tran J, Gu F, Ochoa R, Li C, Sept D, Werbovetz K, Morrissette N.

Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, 92697; Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109-2099; Division of Medicinal Chemistry & Pharmacognosy, Ohio State University, 332 Parks Hall, 500 West 12th Avenue, Columbus, OH 43210-1291; Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110.

The human parasite Toxoplasma gondii is sensitive to dinitroaniline compounds which selectively disrupt microtubules in diverse protozoa but which have no detectable effect on vertebrate host cell microtubules or other functions. Replication of wild type T. gondii is inhibited by 0.5-2.5 muM oryzalin, but mutant parasites harboring amino acid substitutions in the predicted dinitroaniline binding site confer resistance up to 40 muM oryzalin. However, the precise interaction between dinitroanilines and the binding site in alpha-tubulin remains unclear. We have investigated the activity of 12 dinitroanilines and the related compound amiprophos methyl on wild-type and dinitroaniline-resistant parasite lines that contain proposed binding site mutations. These data indicate that dinitramine is the most effective dinitroaniline to inhibit Toxoplasma growth in wild-type parasites and most resistant lines. Dinitramine has an amine group at the meta position not present in any of the other dinitroanilines tested here that is predicted to form hydrogen-bonds with residues Arg2 and Gln133 according to docking data. Remarkably, although the binding site mutation Ile235Val confers increased resistance to most dinitroanilines, it confers increased sensitivity to GB-II-5, a compound optimized for activity against kinetoplastid tubulin. Kinetoplastid parasites have a valine at position 235 of alpha-tubulin whereas apicomplexan parasites have an isoleucine at this site. We suggest that this heterogeneity in binding site environment influences relative dinitroaniline sensitivity in distinct protozoan lineages and hypothesize that a mutation that makes the apicomplexan dinitroaniline binding site more like the kinetoplastid site increases sensitivity to a dinitroaniline optimized for activity in the latter parasites.

PMID: 20145086 [PubMed - as supplied by publisher]