Wednesday, October 31, 2012

A novel co-infection model with Toxoplasma and Chlamydia trachomatis highlights the importance of host cell manipulation for nutrient scavenging

Cell Microbiol. 2012 Oct 29. doi: 10.1111/cmi.12060. [Epub ahead of print]

A novel co-infection model with Toxoplasma and Chlamydia trachomatis highlights the importance of host cell manipulation for nutrient scavenging

Romano JD, de Beaumont C, Carrasco JA, Ehrenman K, Bavoil PM, Coppens I.

Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, 21205, USA.

Toxoplasma and Chlamydia trachomatis are obligate intracellular pathogens that have evolved analogous strategies to replicate within mammalian cells. Both pathogens are known to extensively remodel the cytoskeleton, and to recruit endocytic and exocytic organelles to their respective vacuoles. However, how important these activities are for infectivity by either pathogen remains elusive. Here, we have developed a novel co-infection system to gain insights into the developmental cycles of Toxoplasma and C. trachomatis by infecting human cells with both pathogens, and examining their respective ability to replicate and scavenge nutrients. We hypothesize that the common strategies used by Toxoplasma and Chlamydia to achieve development results in direct competition of the two pathogens for the same pool of nutrients. We show that a single human cell can harbor Chlamydia and Toxoplasma. In co-infected cells, Toxoplasma is able to divert the content of host organelles, such as cholesterol. Consequently, the infectious cycle of Toxoplasma progresses unimpeded. In contrast, Chlamydia's ability to scavenge selected nutrients is diminished, and the bacterium shifts to a stress-induced persistent growth. Parasite killing engenders an ordered return to normal chlamydial development. We demonstrate that C. trachomatis enters a stress-induced persistence phenotype as a direct result from being barred from its normal nutrient supplies as addition of excess nutrients, e.g., amino acids, leads to substantial recovery of Chlamydia growth and infectivity. Co-infection of C. trachomatis with slow growing strains of Toxoplasma or a mutant impaired in nutrient acquisition does not restrict chlamydial development. Conversely, Toxoplasma growth is halted in cells infected with the highly virulent Chlamydia psittaci. This study illustrates the key role that cellular remodeling plays in the exploitation of host intracellular resources by Toxoplasma and Chlamydia. It further highlights the delicate balance between success and failure of infection by intracellular pathogens in a co-infection system at the cellular level.

PMID: 23107293 [PubMed - as supplied by publisher]

Monday, October 29, 2012

Association of a NOD2 gene polymorphism and Th17 lymphocytes with presumed ocular toxoplasmosis

J Infect Dis. 2012 Oct 24. [Epub ahead of print]

Association of a NOD2 gene polymorphism and Th17 lymphocytes with presumed ocular toxoplasmosis

Dutra MS, Béla SR, Peixoto-Rangel AL, Fakiola M, Cruz AG, Gazzinelli A, Quites HF, Bahia-Oliveira LM, Peixe RG, Campos WR, Higino-Rocha AC, Miller NE, Blackwell JM, Antonelli LR, Gazzinelli RT.

Centro de Pesquisas René Rachou, CPqRR - Fundação Oswaldo Cruz, FIOCRUZ, Avenida Augusto de Lima 1517, Belo Horizonte 30190-002, Minas Gerais, Brazil.

Retinochoroiditis manifests in patients infected with Toxoplasma gondii. Here, we assessed 30 sibships and 89 parent/case trios of presumed ocular toxoplasmosis (POT) to evaluate associations with polymorphisms in the NOD2 gene. Three tag-SNPs within the NOD2 gene were genotyped. The Family Based Association Test (FBAT) showed that the tag-SNP rs3135499 is associated with retinochoroiditis (p=0.039). We then characterized the cellular immune response of 59 cases of POT and 4 of active ocular toxoplasmosis (AOT). We found no differences in IFNγ and IL-2 produced by Th1 lymphocytes when comparing patients with AOT or POT to asymptomatic individuals. Unexpectedly, we found an increased IL-17A production in patients with POT or OAT. In both, patients with POT or AOT, the main cellular source of IL-17A was CD4(+)CD45RO(+)T-bet(-)IFNγ(-) Th17 lymphocytes. Altogether, our results suggest that NOD2 influences the production of IL-17A by CD4(+) T lymphocytes and might contribute to the development of ocular toxoplasmosis.

PMID: 23100559 [PubMed - as supplied by publisher]

Sex-dependent neurotransmitter level changes in brains of Toxoplasma gondii infected mice

Exp Parasitol. 2012 Oct 22. pii: S0014-4894(12)00316-5. doi: 10.1016/j.exppara.2012.10.005. [Epub ahead of print]

Sex-dependent neurotransmitter level changes in brains of Toxoplasma gondii infected mice

Gatkowska J, Wieczorek M, Dziadek B, Dzitko K, Dlugonska H.

Department of Immunoparasitology, Faculty of Biology and Environmental Protection, University of Lodz, 90-237 Lodz, Banacha 12/16, Poland. Electronic address:

The protozoan parasite Toxoplasma gondii has the ability to alter intermediate host behavior, most impressively the natural aversion to cat scent, to favor the predation by the definitive host. However, the underlying mechanism of the observed phenomenon still remains unknown. Since changes in the neurotransmitter level are postulated as a possible contributing factor, the aim of this work was to assess the monoamine systems activity in specified brain regions involved in the natural defense behaviors, emotion evaluation, and motor and sensory stimuli integration in experimentally T. gondii infected mice compared to uninfected controls. Taking into account the natural differences between genders, the experiments were carried out on both male and female mice. Our results revealed statistically significant changes in all tested monoamine systems with regard to both gender and time after T. gondii invasion. Acute toxoplasmosis was accompanied by a decrease in noradrenergic system activity in females and its slight increase in some brain areas of males. Acute invasion also induced a rise in serotonin system activity, mostly in males. The most striking observation was an increase in the dopamine release noted in acutely infected males. We discuss our results in terms of their possible contribution to T. gondii-induced intermediate host behavior alterations and parasite transmission and with regard to postulated relationship between T. gondii seroprevalence and occurrence of certain disorders such as schizophrenia in humans.

PMID: 23098668 [PubMed - as supplied by publisher]

Friday, October 26, 2012

Protein palmitoylation and pathogenesis in apicomplexan parasites

J Biomed Biotechnol. 2012;2012:483969. doi: 10.1155/2012/483969. Epub 2012 Oct 3.

Protein palmitoylation and pathogenesis in apicomplexan parasites

Corvi MM, Alonso AM, Caballero MC.

Laboratorio de Parasitologia Molecular, Instituto Tecnológico de Chascomús (IIBINTECH), CONICET-Universidad Nacional de General San Martín, Intendente Marino Km 8,2, P.O. Box 164, Chascomús, B7130IWA Buenos Aires, Argentina.

Apicomplexan parasites comprise a broad variety of protozoan parasites, including Toxoplasma gondii, Plasmodium, Eimeria, and Cryptosporidium species. Being intracellular parasites, the success in establishing pathogenesis relies in their ability to infect a host-cell and replicate within it. Protein palmitoylation is known to affect many aspects of cell biology. Furthermore, palmitoylation has recently been shown to affect important processes in T. gondii such as replication, invasion, and gliding. Thus, this paper focuses on the importance of protein palmitoylation in the pathogenesis of apicomplexan parasites.

PMID: 23093847 [PubMed - in process]

Wednesday, October 17, 2012

Evolution of apicomplexan secretory organelles

Int J Parasitol. 2012 Oct 12. pii: S0020-7519(12)00232-9. doi: 10.1016/j.ijpara.2012.09.009. [Epub ahead of print]

Evolution of apicomplexan secretory organelles.

Gubbels MJ, Duraisingh MT.

Department of Biology, Boston College, 140 Commonwealth Avenue, Higgins Hall 355, Chestnut Hill, MA 02467, USA.

The alveolate superphylum includes many free-living and parasitic organisms, which are united by the presence of alveolar sacs lying proximal to the plasma membrane, providing cell structure. All species comprising the apicomplexan group of alveolates are parasites and have adapted to the unique requirements of the parasitic lifestyle. Here the evolution of apicomplexan secretory organelles that are involved in the critical process of egress from one cell and invasion of another is explored. The variations within the Apicomplexa and how these relate to species-specific biology will be discussed. In addition, recent studies have identified specific calcium-sensitive molecules that coordinate the various events and regulate the release of these secretory organelles within apicomplexan parasites. Some aspects of this machinery are conserved outside the Apicomplexa, and are beginning to elucidate the conserved nature of the machinery. Briefly, the relationship of this secretion machinery within the Apicomplexa will be discussed, compared with free-living and predatory alveolates, and how these might have evolved from a common ancestor.

 PMID: 23068912 [PubMed - as supplied by publisher]

Modulation of innate immunity by Toxoplasma gondii virulence effectors

Nat Rev Microbiol. 2012 Oct 16;10(11):766-78. doi: 10.1038/nrmicro2858.

Modulation of innate immunity by Toxoplasma gondii virulence effectors.

Hunter CA, Sibley LD.

Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104, USA.

Toxoplasma gondii is a common parasite of animals and humans and can cause serious opportunistic infections. However, the majority of infections are asymptomatic, possibly because the organism has co-evolved with its many vertebrate hosts and has developed multiple strategies to persist asymptomatically for the lifetime of the host. Over the past two decades, infection studies in the mouse, combined with forward-genetics approaches aimed at unravelling the molecular basis of infection, have revealed that T. gondii virulence is mediated, in part, by secretion of effector proteins into the host cell during invasion. Here, we review recent advances that illustrate how these virulence factors disarm innate immunity and promote survival of the parasite.

PMID: 23070557 [PubMed - in process]

Identification of Toxoplasma gondii Genes Responsive to the Host Immune Response during In Vivo Infection

PLoS One. 2012;7(10):e46621. doi: 10.1371/journal.pone.0046621. Epub 2012 Oct 10.

Identification of Toxoplasma gondii Genes Responsive to the Host Immune Response during In Vivo Infection.

Skariah S, Mordue DG.

Department of Microbiology and Immunology, New York Medical College, Valhalla, New York, United States of America.

Toxoplasma gondii is an obligate intracellular protozoa parasite that causes the disease toxoplasmosis. It resides within host cells in a parasitophorous vacuole distinct from the host cell endocytic system. T. gondii was used as a model to investigate how obligate intracellular parasites alter their gene expression in response to the host immune response during infection compared to growth in host cells in vitro. While bacterial pathogens clearly alter gene expression to adapt to the host environment during infection, the degree to which the external environment affects gene expression by obligate intracellular pathogens sequestered within host cells is less clear. The global transcriptome of T. gondii was analyzed in vivo in the presence and absence of the IFN-γ-dependent host innate immune response. The parasites' in vivo transcriptome was also compared to its transcriptome in vitro in fibroblast cells. Our results indicate that the parasite transcriptome is significantly altered during in vivo infection in the presence, but not absence, of IFN-γ-dependent immunity compared with fibroblasts infected in vitro. Many of the parasite genes increased in vivo appear to be common to an early general stress response by the parasite; surprisingly putative oocyst stage specific genes were also disproportionately increased during infection.

PMID: 23071600 [PubMed - in process]

Interventions for Toxoplasma Retinochoroiditis

Ophthalmology. 2012 Oct 11. pii: S0161-6420(12)00698-7. doi: 10.1016/j.ophtha.2012.07.061. [Epub ahead of print]

Interventions for Toxoplasma Retinochoroiditis: A Report by the American Academy of Ophthalmology.

Kim SJ, Scott IU, Brown GC, Brown MM, Ho AC, Ip MS, Recchia FM.

Department of Ophthalmology, Vanderbilt University School of Medicine, Nashville, Tennessee. Electronic address:

To evaluate the available evidence in peer-reviewed publications about the outcomes and safety of interventions for toxoplasma retinochoroiditis (TRC).
Literature searches of the PubMed and the Cochrane Library databases were conducted last on July 20, 2011, with no date restrictions. The searches retrieved 275 unique citations, and 36 articles of possible clinical relevance were selected for full text review. Of these 36 articles, 11 were deemed sufficiently relevant or of interest, and they were rated according to strength of evidence.
Eight of the 11 studies reviewed were randomized controlled studies, and none of them demonstrated that routine antibiotic or corticosteroid treatment of TRC favorably affects visual outcomes or reduces lesion size. There is level II evidence from 1 study suggesting that long-term treatment with combined trimethoprim and sulfamethoxazole prevented recurrent disease in patients with chronic relapsing TRC. Adverse effects of antibiotic treatment were reported in as many as 25% of patients. There was no evidence supporting the efficacy of other nonmedical treatments such as laser photocoagulation.
There is a lack of level I evidence to support the efficacy of routine antibiotic or corticosteroid treatment for acute TRC in immunocompetent patients. There is level II evidence suggesting that long-term prophylactic treatment may reduce recurrences in chronic relapsing TRC. Adverse effects of certain antibiotic regimens are frequent, and patients require regular monitoring and timely discontinuation of the antibiotic in some cases.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.

 PMID: 23062648 [PubMed - as supplied by publisher]

Friday, October 12, 2012

Toxoplasma gondii and homicide

Psychol Rep. 2012 Aug;111(1):196-7.

Toxoplasma gondii and homicide.

Lester D.

Psychology Program, The Richard Stockton College of New Jersey, 101 Vera King Farris Drive, Galloway, NJ 08205-9441, USA.

In a sample of 20 European nations, the prevalence of the brain parasite Toxoplasma gondii was positively associated with national homicide rates, amplifying previous research indicating a positive association of Toxoplasma gondii with suicide rates. Possible causal mechanisms were proposed.

PMID: 23045862 [PubMed - in process]

Isolation of viable Toxoplasma gondii cysts from brain samples for oral infection

Eur Rev Med Pharmacol Sci. 2012 Sep;16(9):1179-83.

Isolation of viable Toxoplasma gondii cysts from brain samples for oral infection.

Puvanesuaran VR, Ibrahim N, Noordin R, Balakrishnan V.

Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia. e-mail:

A method was developed to separate contaminant-free viable Toxoplasma gondii cysts from brain samples of infected mice for molecular biology studies and reinfection.
The mice brains were homogenized and washed with phosphate buffered saline (PBS) Tween 80 prior to fractionation using 19-22% dextran solution. Finally, the supernatant was purified by two-step membrane filtration (100-160 microm and < 10 microm) to obtain pure T. gondii cyst. The isolates were analyzed through microscopic observation, qPCR and by reinfection of new batch of mice.
T. gondii cysts were best isolated with 21% dextran solution and two step filtration.
The method was observed not to disrupt the integrity of the cysts containing bradyzoites. In addition, the isolated cysts in the filtrate were found to be contaminant-free, viable and able to infect healthy mice when introduced orally; which, mimics the natural infectivity pathway.

PMID: 23047500 [PubMed - in process]

Wednesday, October 03, 2012

A chloroplast-derived Toxoplasma gondii GRA4 antigen used as an oral vaccine protects against toxoplasmosis in mice

Plant Biotechnol J. 2012 Oct 1. doi: 10.1111/pbi.12001. [Epub ahead of print]

A chloroplast-derived Toxoplasma gondii GRA4 antigen used as an oral vaccine protects against toxoplasmosis in mic

Del L Yácono M, Farran I, Becher ML, Sander V, Sánchez VR, Martín V, Veramendi J, Clemente M.

Laboratorio de Biotecnología Vegetal, IIB-INTECH, CONICET-UNSAM, Chascomús, Argentina.

The parasitic protozoan Toxoplasma gondii, the causal agent of toxoplasmosis, can infect most mammals and birds. In human medicine, T. gondii can cause complications in pregnant women and immunodeficient individuals, while in veterinary medicine, T. gondii infection has economic importance due to abortion and neonatal loss in livestock. Thus, the development of an effective anti-Toxoplasma vaccine would be of great value. In this study, we analysed the expression of T. gondii GRA4 antigen by chloroplast transformation (chlGRA4) in tobacco plants and evaluated the humoral and cellular responses and the grade of protection after oral administration of chlGRA4 in a murine model. The Western blot analysis revealed a specific 34-kDa band mainly present in the insoluble fractions. The chlGRA4 accumulation levels were approximately 6 μg/g of fresh weight (equivalent to 0.2% of total protein). Oral immunization with chlGRA4 resulted in a decrease of 59% in the brain cyst load of mice compared to control mice. ChlGRA4 immunization elicited both a mucosal immune response characterized by the production of specific IgA, and IFN-γ, IL-4 and IL-10 secretion by mesenteric lymph node cells, and a systemic response in terms of GRA4-specific serum antibodies and secretion of IFN-γ, IL-4 and IL-10 by splenocytes. Our results indicate that oral administration of chlGRA4 promotes the elicitation of both mucosal and systemic balanced Th1/Th2 responses that control Toxoplasma infection, reducing parasite loads.

 PMID: 23020088 [PubMed - as supplied by publisher]

Interferon-γ Restricts Toxoplasma gondii Development in Murine Skeletal Muscle Cells via Nitric Oxide Production and Immunity-Related GTPases

PLoS One. 2012;7(9):e45440. Epub 2012 Sep 14.

Interferon-γ Restricts Toxoplasma gondii Development in Murine Skeletal Muscle Cells via Nitric Oxide Production and Immunity-Related GTPases

Takács AC, Swierzy IJ, Lüder CG.

Institute for Medical Microbiology, University Medical Center, Georg-August-University, Göttingen, Germany.

The apicomplexan parasite Toxoplasma gondii is regularly transmitted to humans via the ingestion of contaminated meat products from chronically infected livestock. This route of transmission requires intracellular development and long-term survival of the parasite within muscle tissue. In this study, we determined the cell-autonomous immunity of mature primary embryonic or C2C12 skeletal muscle cells (SkMCs) to infection with T. gondii. Non-activated SkMCs and control fibroblasts sustained parasite replication; however, interferon (IFN)-γ significantly inhibited parasite growth in SkMCs but not in fibroblasts. Intracellular parasite replication was diminished by IFN-γ whereas host cell invasion was not affected. Tumor necrosis factor (TNF) did not further increase the IFN-γ-triggered host defense of SkMCs against Toxoplasma. Remarkably, IFN-γ alone or in combination with TNF decreased the high level of T. gondii bradyzoite formation being observed in non-activated SkMCs. Stimulation of SkMCs with IFN-γ strongly triggered expression of inducible nitric oxide synthase (iNOS) transcripts, and induced significantly higher levels of nitric oxide (NO) in SkMCs than in fibroblasts. Consequently, pharmacological inhibition of iNOS partially abrogated the IFN-γ-induced toxoplasmacidal activity of SkMCs. In addition, SkMCs strongly up-regulated immunity-regulated GTPases (IRGs) following stimulation with IFN-γ. IRGs accumulated on Toxoplasma-containing vacuoles in SkMCs in a parasite strain-dependent manner. Subsequent vacuole disruption and signs of degenerating parasites were regularly recognized in IFN-γ-treated SkMCs infected with type II parasites. Together, murine SkMCs exert potent toxoplasmacidal activity after stimulation with IFN-γ and have to be considered active participants in the local immune response against Toxoplasma in skeletal muscle.

PMID: 23024821 [PubMed - in process]

Impaired innate immunity in IRAK4 deficient mice leads to defective Type 1 T cell responses, B cell expansion and enhanced susceptibility to infection with Toxoplasma

Infect Immun. 2012 Oct 1. [Epub ahead of print]

Impaired innate immunity in IRAK4 deficient mice leads to defective Type 1 T cell responses, B cell expansion and enhanced susceptibility to infection with Toxoplasma gondi

Béla SR, Dutra MS, Mui E, Montpetit A, Oliveira FS, Oliveira SC, Arantes RM, Antonelli LR, McLeod R, Gazzinelli RT.

Centro de Pesquisas René Rachou, CPqRR - Fundação Oswaldo Cruz, Avenida Augusto de Lima 1517, Belo Horizonte 30190-002, MG, Brazil.

IL1R-associated kinase (IRAK) 4 is a member of the IRAK family, and has an important role in inducing the production of inflammatory mediators. This kinase is downstream of MyD88, an adaptor protein essential for Toll-Like Receptors (TLRs) function. Herein, we investigated the role of this kinase in IRAK4 deficient mice orally infected with the cystogenic ME49 strain of T. gondii. IRAK4(-/-) mice displayed higher morbidity, tissue parasitism and accelerated mortality, when compared to the control mice. Lymphoid folicles and germinal centers from infected IRAK4(-/-) mice were significantly smaller. Consistently, IRAK4(-/-) mice showed a defect on splenic B cell activation and expansion as well as diminished production of IFNγ by T lymphocytes. The myeloid compartment was also affected. Both frequency and ability of dendritic cells (DCs) and monocytes/macrophage to produce IL-12 were significantly decreased, and resistance to infection with Toxoplasma was rescued by treating IRAK4(-/-) mice with rIL-12. Additionally, we report the association of IRAK4 haplotype-tagging single nucleotide polymorphisms (tag-SNPs) with congenital toxoplasmosis in infected affected individuals (rs1461567 and rs4251513, p<0 .023=".023" acquired="acquired" activation="activation" and="and" br="br" cells="cells" development="development" essential="essential" for="for" gondii.="gondii." host="host" immune="immune" immunity="immunity" infection="infection" innate="innate" irak4="irak4" is="is" of="of" p="p" parasite="parasite" resistance="resistance" respectively="respectively" signaling="signaling" specific="specific" t.="t." thus="thus" to="to" via="via" with="with">
PMID: 23027530 [PubMed - as supplied by publisher]

Targeted proteomic dissection of Toxoplasma cytoskeleton sub-compartments using MORN1

Cytoskeleton (Hoboken). 2012 Oct 1. doi: 10.1002/cm.21077. [Epub ahead of print]

Targeted proteomic dissection of Toxoplasma cytoskeleton sub-compartments using MORN

Lorestani A, Ivey FD, Thirugnanam S, Busby MA, Marth GT, Cheeseman IM, Gubbels MJ.

Boston College, Department of Biology, Chestnut Hill, MA 02467, USA.

The basal complex in Toxoplasma functions as the contractile ring in the cell division process. Basal complex contraction tapers the daughter cytoskeleton toward the basal end and is required for daughter segregation. We have previously shown that the protein MORN1 is essential for basal complex assembly and likely acts as a scaffolding protein. To further our understanding of the basal complex we combined subcellular fractionation with an affinity purification of the MORN1 complex and identified its protein composition. We identified two new components of the basal complex, one of which uniquely associated with the basal complexin mature parasites, the first of its kind. In addition, we identified several other novel cytoskeleton proteins with different spatiotemporal dynamics throughout cell division. Since many of these proteins are unique to Apicomplexa this study significantly contributes to the annotation of their unique cytoskeleton. Furthermore we show that G-actin binding protein TgCAP is localized at the apical cap region in intracellular parasites, but quickly re-distributes to a cytoplasmic localization pattern upon egress. © 2012 Wiley-Blackwell, Inc.

 PMID: 23027733 [PubMed - as supplied by publisher]

Influence of Tryptophan Contained in 1-Methyl-Tryptophan on Antimicrobial and Immunoregulatory Functions of Indoleamine 2,3-Dioxygenase

PLoS One. 2012;7(9):e44797. Epub 2012 Sep 13.

Influence of Tryptophan Contained in 1-Methyl-Tryptophan on Antimicrobial and Immunoregulatory Functions of Indoleamine 2,3-Dioxygenase

Schmidt SK, Siepmann S, Kuhlmann K, Meyer HE, Metzger S, Pudelko S, Leineweber M, Däubener W.

Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.

Indoleamine 2,3-dioxygenase (IDO) has been identified as an important antimicrobial and immunoregulatory effector molecule essential for the establishment of tolerance by regulating local tryptophan (Trp) concentrations. On the other hand, the immunosuppressive capacity of IDO can have detrimental effects for the host as it can lead to deleterious alterations of the immune response by promoting tolerance to some types of tumors. To suppress this disadvantageous IDO effect, the competitive inhibitor 1-Methyl-Tryptophan (1-MT) is being tested in clinical trials. However, it remains inconclusive which stereoisomer of 1-MT is the more effective inhibitor of IDO-mediated immunosuppression. While IDO enzyme activity is more efficiently inhibited by 1-L-MT in cell-free or in vitro settings, 1-D-MT is superior to 1-L-MT in the enhancement of anti-tumor responses in vivo.Here, we present new data showing that commercially available 1-L-MT lots contain tryptophan in amounts sufficient to compensate for the IDO-mediated tryptophan depletion in vitro. The addition of 1-L-MT abrogated IDO-mediated antimicrobial effects and permitted the growth of the tryptophan-auxotroph microorganisms Staphylococcus aureus and Toxoplasma gondii. Consistent with this, the tryptophan within 1-L-MT lots was sufficient to antagonize IDO-mediated inhibition of T cell responses. Mass spectrometry (MS) analysis revealed not only tryptophan within 1-L-MT, but also the incorporation of this tryptophan in bacterial and human proteins that were generated in the presence of 1-L-MT in otherwise tryptophan-free conditions. In summary, these data reveal that tryptophan within 1-L-MT can affect the results of in vitro studies in an L-stereospecific and IDO-independent way.

PMID: 23028625 [PubMed - as supplied by publisher]

Monday, October 01, 2012

Endochin-like quinolones are highly efficacious against acute and latent experimental toxoplasmosis

Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15936-41. Epub 2012 Sep 10.

Endochin-like quinolones are highly efficacious against acute and latent experimental toxoplasmosis

Doggett JS, Nilsen A, Forquer I, Wegmann KW, Jones-Brando L, Yolken RH, Bordón C, Charman SA, Katneni K, Schultz T, Burrows JN, Hinrichs DJ, Meunier B, Carruthers VB, Riscoe MK.

Division of Infectious Diseases and Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239.

Toxoplasma gondii is a widely distributed protozoan pathogen that causes devastating ocular and central nervous system disease. We show that the endochin-like quinolone (ELQ) class of compounds contains extremely potent inhibitors of T. gondii growth in vitro and is effective against acute and latent toxoplasmosis in mice. We screened 50 ELQs against T. gondii and selected two lead compounds, ELQ-271 and ELQ-316, for evaluation. ELQ-271 and ELQ-316, have in vitro IC(50) values of 0.1 nM and 0.007 nM, respectively. ELQ-271 and ELQ-316 have ED(50) values of 0.14 mg/kg and 0.08 mg/kg when administered orally to mice with acute toxoplasmosis. Moreover, ELQ-271 and ELQ-316 are highly active against the cyst form of T. gondii in mice at low doses, reducing cyst burden by 76-88% after 16 d of treatment. To investigate the ELQ mechanism of action against T. gondii, we demonstrate that endochin and ELQ-271 inhibit cytochrome c reduction by the T. gondii cytochrome bc(1) complex at 8 nM and 31 nM, respectively. We also show that ELQ-271 inhibits the Saccharomyces cerevisiae cytochrome bc(1) complex, and an M221Q amino acid substitution in the Q(i) site of the protein leads to >100-fold resistance. We conclude that ELQ-271 and ELQ-316 are orally bioavailable drugs that are effective against acute and latent toxoplasmosis, likely acting as inhibitors of the Q(i) site of the T. gondii cytochrome bc(1) complex.

PMID: 23019377 [PubMed - in process]