Thursday, November 24, 2011

An Inside Job: Hacking Into JAK/STAT Signaling Cascades by the Intracellular Protozoan Toxoplasma gondii

Infect Immun. 2011 Nov 21. [Epub ahead of print]

An Inside Job: Hacking Into JAK/STAT Signaling Cascades by the Intracellular Protozoan Toxoplasma gondii.

Denkers EY, Bzik DJ, Fox BA, Butcher BA.

SourceDepartment of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca NY.

The intracellular protozoan Toxoplasma gondii is well known for its skill at invading and living within host cells. New discoveries are now also revealing the astounding ability of the parasite to inject effector proteins into the cytoplasm to seize control of the host cell. This Review summarizes recent advances in our understanding of one such secretory protein called ROP16. This molecule is released from rhoptries into the host cell during invasion. The ROP16 molecule acts as a kinase, directly activating both STAT3 and STAT6 signaling pathways. In macrophages, an important and preferential target cell of parasite infection, the injection of ROP16 has multiple consequences, including down-regulation of proinflammatory cytokine signaling and macrophage deviation to an alternatively activated phenotype.

PMID:22104110[PubMed - as supplied by publisher]

Toxoplasma gondii Triggers Release of Human and Mouse Neutrophil Extracellular Traps

Infect Immun. 2011 Nov 21. [Epub ahead of print]

Toxoplasma gondii Triggers Release of Human and Mouse Neutrophil Extracellular Traps.

Abi Abdallah DS, Lin C, Ball CJ, King MR, Duhamel GE, Denkers EY.

SourceDepartment of Microbiology and Immunology.

Neutrophils have recently been shown to release DNA-based extracellular traps that contribute to microbicidal killing and have also been implicated in autoimmunity. The role of neutrophil extracellular trap (NET) formation in the host response to nonbacterial pathogens has received much less attention. Here, we show that the protozoan pathogen Toxoplasma gondii elicits production of NETs from human and mouse neutrophils. Tachyzoites of each of the three major parasite strain types were efficiently entrapped within NETs, resulting in decreased parasite viability. We also show that Toxoplasma activates a MEK-ERK pathway in neutrophils and that inhibition of this pathway leads to decreased NET formation. To determine if Toxoplasma induced NET formation in vivo we employed a mouse intranasal infection model. We found that administration of tachyzoites by this route induced rapid tissue recruitment of neutrophils with evidence of extracellular DNA release. Taken together, these data indicate a role for NETs in the host innate response to protozoan infection. We propose that NET formation limits infection by direct microbicidal effects on Toxoplasma as well as by interfering with the ability of the parasite to invade target host cells.

PMID:22104111[PubMed - as supplied by publisher]

Infectious agents associated with schizophrenia: A meta-analysis

Schizophr Res. 2011 Nov 18. [Epub ahead of print]

Infectious agents associated with schizophrenia: A meta-analysis.

Arias I, Sorlozano A, Villegas E, Luna JD, McKenney K, Cervilla J, Gutierrez B, Gutierrez J.

SourceCAP El Clot, Institut Català de la Salut, Barcelona, Spain.

Schizophrenia is a highly disabling and limiting disorder for patients and the possibility that infections by some microorganisms may be associated to its development may allow prevention and recovery. In the current study we have done a meta-analysis of studies that have assessed the possible association between detection of different infectious agents and schizophrenia. We report results that support the idea that there is a statistically significant association between schizophrenia and infection by Human Herpesvirus 2 (OR=1.34; CI 95%: 1.09-1.70; p=0.05), Borna Disease Virus (OR=2.03; CI 95%: 1.35-3.06; p<0.01), Human Endogenous Retrovirus W (OR=19.31; CI 95%: 6.74-55.29; p<0.001), Chlamydophila pneumoniae (OR=6.34; CI 95%: 2.83-14.19; p<0.001), Chlamydophila psittaci (OR=29.05; CI 95%: 8.91-94.70; p<0.001) and Toxoplasma gondii (OR=2.70; CI 95%: 1.34-4.42; p=0.005). The implications of these findings are discussed and further research options are also explicated.

Copyright © 2011 Elsevier B.V. All rights reserved.

PMID:22104141[PubMed - as supplied by publisher]

Tuesday, November 22, 2011

Impaired reproductive function of male rats infected with Toxoplasma gondii

Andrologia. 2011 Nov 18. doi: 10.1111/j.1439-0272.2011.01249.x. [Epub ahead of print]

Impaired reproductive function of male rats infected with Toxoplasma gondii.

Abdoli A, Dalimi A, Movahedin M

Source Department of Parasitology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran  Department of Anatomy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.

Toxoplasmosis is one of the classical conditions known to have an adverse effect on female reproductive functions, but a few investigations into male reproductive parameters have been performed. This work was carried out to study the effects of Toxoplasma gondii on reproductive function in male rats. Male rats were infected with the RH strain of T. gondii tachyzoites, and following every 10 days from 10 to 70 postinfection (PI), the percentage of body weight to testis weight ratio as well as epididymal sperm parameters (number, motility, viability, and morphology rates), serum testosterone (ST), intratesticular testosterone (ITT), serum lactate dehydrogenase (SLDH), intratesticular lactate dehydrogenase and fructose in seminal vesicles and coagulating glands were measured. The results of the study showed sperm motility, viability and concentration rates were significantly decreased temporary after infection up to 70 days. Sperm abnormality was also increased during these days. In addition, temporary alteration in ST, ITT, SLDH, intratesticular LDH and fructose in seminal vesicle and coagulating gland was observed PI. These findings suggest that toxoplasmosis can cause impermanent impairment on the reproductive parameters of male rats.

© 2011 Blackwell Verlag GmbH.

PMID:22098674[PubMed - as supplied by publisher]

Monday, November 21, 2011

Mechanisms of Toxoplasma gondii persistence and latency

FEMS Microbiol Rev. 2011 Sep 12. doi: 10.1111/j.1574-6976.2011.00305.x. [Epub ahead of print]

Mechanisms of Toxoplasma gondii persistence and latency.

Sullivan WJ Jr, Jeffers V

SourceDepartment of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA.

Toxoplasma gondii is an obligate intracellular protozoan parasite that causes opportunistic disease, particularly in immunocompromised individuals. Central to its transmission and pathogenesis is the ability of the proliferative stage (tachyzoite) to convert into latent tissue cysts (bradyzoites). Encystment allows Toxoplasma to persist in the host and affords the parasite a unique opportunity to spread to new hosts without proceeding through its sexual stage, which is restricted to felids. Bradyzoite tissue cysts can cause reactivated toxoplasmosis if host immunity becomes impaired. A greater understanding of the molecular mechanisms orchestrating bradyzoite development is needed to better manage the disease. Here, we will review key studies that have contributed to our knowledge about this persistent form of the parasite and how to study it, with a focus on how cellular stress can signal for the reprogramming of gene expression needed during bradyzoite development.

© 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

PMID:22091606[PubMed - as supplied by publisher]

Thursday, November 17, 2011

Fatal Attraction Phenomenon in Humans - Cat Odour Attractiveness Increased for Toxoplasma-Infected Men While Decreased for Infected Women

PLoS Negl Trop Dis. 2011 Nov;5(11):e1389. Epub 2011 Nov 8.

Fatal Attraction Phenomenon in Humans - Cat Odour Attractiveness Increased for Toxoplasma-Infected Men While Decreased for Infected Women.

Flegr J, Lenochová P, Hodný Z, Vondrová M.

SourceDepartment of Biology, Faculty of Science, Charles University, Prague, Czech Republic.

BACKGROUND: Latent toxoplasmosis, a lifelong infection with the protozoan Toxoplasma gondii, has cumulative effects on the behaviour of hosts, including humans. The most impressive effect of toxoplasmosis is the "fatal attraction phenomenon," the conversion of innate fear of cat odour into attraction to cat odour in infected rodents. While most behavioural effects of toxoplasmosis were confirmed also in humans, neither the fatal attraction phenomenon nor any toxoplasmosis-associated changes in olfactory functions have been searched for in them.

PRINCIPAL FINDINGS: Thirty-four Toxoplasma-infected and 134 noninfected students rated the odour of urine samples from cat, horse, tiger, brown hyena and dog for intensity and pleasantness. The raters were blind to their infection status and identity of the samples. No signs of changed sensitivity of olfaction were observed. However, we found a strong, gender dependent effect of toxoplasmosis on the pleasantness attributed to cat urine odour (p = 0.0025). Infected men rated this odour as more pleasant than did the noninfected men, while infected women rated the same odour as less pleasant than did noninfected women. Toxoplasmosis did not affect how subjects rated the pleasantness of any other animal species' urine odour; however, a non-significant trend in the same directions was observed for hyena urine.

CONCLUSIONS: The absence of the effects of toxoplasmosis on the odour pleasantness score attributed to large cats would suggest that the amino acid felinine could be responsible for the fatal attraction phenomenon. Our results also raise the possibility that the odour-specific threshold deficits observed in schizophrenia patients could be caused by increased prevalence of Toxoplasma-infected subjects in this population rather than by schizophrenia itself. The trend observed with the hyena urine sample suggests that this carnivore, and other representatives of the Feliformia suborder, should be studied for their possible role as definitive hosts in the life cycle of Toxoplasma.

PMID:22087345[PubMed - as supplied by publisher]

Congenital parasitic infections: A review

Acta Trop. 2011 Nov 7. [Epub ahead of print]

Congenital parasitic infections: A review.

Carlier Y, Truyens C, Deloron P, Peyron F.

SourceLaboratoire de Parasitologie, Faculté de Médecine, Université Libre de Bruxelles (ULB), CP 616, Route de Lennik 808, 1070 Brussels, Belgium; Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University, Suite 2210, 1440 Canal Street, New Orleans, LA 70112-2797, USA.

This review defines the concepts of maternal-fetal (congenital) and vertical transmissions (mother-to-child) of pathogens and specifies the human parasites susceptible to be congenitally transferred. It highlights the epidemiological features of this transmission mode for the three main congenital parasitic infections due to Toxoplasma gondii, Trypanosoma cruzi and Plasmodium sp. Information on the possible maternal-fetal routes of transmission, the placental responses to infection and timing of parasite transmission are synthesized and compared. The factors susceptible to be involved in parasite transmission and development of congenital parasitic diseases, such as the parasite genotypes, the maternal co-infections and parasitic load, the immunological features of pregnant women and the capacity of some fetuses/neonates to overcome their immunological immaturity to mount an immune response against the transmitted parasites are also discussed and compared. Analysis of clinical data indicates that parasitic congenital infections are often asymptomatic, whereas symptomatic newborns generally display non-specific symptoms. The long-term consequences of congenital infections are also mentioned, such as the imprinting of neonatal immune system and the possible trans-generational transmission. The detection of infection in pregnant women is mainly based on standard serological or parasitological investigations. Amniocentesis and cordocentesis can be used for the detection of some fetal infections. The neonatal infection can be assessed using parasitological, molecular or immunological methods; the place of PCR in such neonatal diagnosis is discussed. When such laboratory diagnosis is not possible at birth or in the first weeks of life, standard serological investigations can also be performed 8-10 months after birth, to avoid detection of maternal transmitted antibodies. The specific aspects of treatment of T. gondii, T. cruzi and Plasmodium congenital infections are mentioned. The possibilities of primary and secondary prophylaxes, as well as the available WHO corresponding recommendations are also presented.

Copyright © 2011. Published by Elsevier B.V.

PMID:22085916[PubMed - as supplied by publisher]

Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study

Bipolar Disord. 2011 Nov;13(7-8):624-629. doi: 10.1111/j.1399-5618.2011.00962.x.

Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study.

Mortensen PB, Pedersen CB, McGrath JJ, Hougaard DM, Nørgaard-Petersen B, Mors O, Børglum AD, Yolken RH.

SourceNational Centre for Register-based Research, Faculty of Social Sciences, University of Aarhus, Aarhus, Denmark Queensland Brain Institute, University of Queensland, St. Lucia, Qld, Australia State Serum Institute, København, Denmark Centre for Psychiatric Research, University Hospital in Aarhus, Psychiatric Hospital, Risskov, Denmark Institute of Human Genetics, University of Aarhus, Aarhus, Denmark Stanley Neurovirology Laboratory, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.

Mortensen PB, Pedersen CB, McGrath JJ, Hougaard DM, Nørgaard-Petersen B, Mors O, Børglum AD, Yolken RH. Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study. Bipolar Disord 2011: 13: 624-629. © 2011 The Authors. Journal compilation © 2011 John Wiley & Sons A/S. Objective:  There is a substantial evidence base linking prenatal exposure to infectious agents and an increased risk of schizophrenia. However, there has been less research examining the potential for these exposures to also contribute to risk for bipolar disorder. The aim of this study was to examine the association between neonatal markers of selected prenatal infections and risk for bipolar disorder. Methods:  Using population-based Danish registers, we examined 127 individuals with a diagnosis of bipolar disorder, and 127 sex and day-of-birth individually matched controls. Based on neonatal dried blood spots, we measured antibodies to herpes simplex virus type 1 (HSV-1) and 2 (HSV-2), cytomegalovirus (CMV), and Toxoplasma gondii. Relative risks were calculated for the matched pairs when examined for optical density units for antibodies to each of the infectious agents. Results:  There was no association between any of the neonatal markers of prenatal infection and risk of bipolar disorder. Conclusions:  In contrast with studies of schizophrenia, our analysis does not support maternal infection with HSV-1, HSV-2, CMV, or Toxoplasma gondii as risk factors for bipolar disorder. However, larger study samples are needed, and data on, for example, specific serotypes of Toxoplasma and indicators of the timing of maternal infection are still warranted.

© 2011 John Wiley and Sons A/S.

PMID:22085475[PubMed - as supplied by publisher]

rROP2(186?533): A Novel Peptide Antigen for Detection of IgM Antibodies Against Toxoplasma gondii

Foodborne Pathog Dis. 2011 Nov 15. [Epub ahead of print]

rROP2(186?533): A Novel Peptide Antigen for Detection of IgM Antibodies Against Toxoplasma gondii.

Liu L, Liu T, Yu L, Cai Y, Zhang A, Xu X, Luo Q, Hu Y, Song W, Lun Z, Lu F, Wang Y, Shen J.

Source1 Anhui Provincial Key Laboratory of Microbiology and Parasitology, Anhui Medical University , Hefei, China .

Abstract Toxoplasma gondii infections are prevalent in a wide range of mammalian hosts including humans. Infection in pregnant women may cause the transmission of parasite to the fetus that makes serious problems. IgM antibodies against Toxoplasma (Toxo-IgM) have been believed to be significant indicators for both recently acquired and congenital toxoplasmosis. So far, however, there has not been any recognized protein of T. gondii that specifically reacts to IgM antibodies. Here, an antigen exclusively for detection of IgM antibodies screened by two-dimensional electrophoresis and mass spectrometry has been reported. The study identified 13 Toxoplasma proteins probed by IgG antibodies and one (rhpotry protein 2 [ROP2]) by IgM antibodies with human sera of Toxo-IgM(?)-IgG(+) and -IgM(+)-IgG(?), respectively, which had been prescreened by Toxo-IgM and -IgG commercial kits from the suspected cases. Following cloning, expression, and purification of the fragment of ROP2(186?533), an enzyme-linked immunosorbent assay with rROP2(186?533) to measure IgM and IgG antibodies was developed. As a result, 100%(48/48) of sera with Toxo-IgM(+)-IgG(?)showed positive Toxo-IgM but none of them (0%) showed positive Toxo-IgG when rROP2(186?533) was used as antigen. Neither Toxo-IgG nor Toxo-IgM antibodies were found when tested with 59 sera of Toxo-IgM(?)-IgG(+). These results indicate that rROP2(186?533) could be used as an antigen that specifically capture Toxo-IgM antibodies and may have a high potential in the serological diagnosis of both acute acquired and congenital toxoplasmosis.

PMID:22085219[PubMed - as supplied by publisher]

Wednesday, November 16, 2011

Tissue barriers of the human placenta to infection with Toxoplasma gondii

Infect Immun. 2011 Nov 14. [Epub ahead of print]

Tissue barriers of the human placenta to infection with Toxoplasma gondii.

Robbins JR, Zeldovich VB, Poukchanski A, Boothroyd JC, Bakardjiev AI.

SourceDepartment of Pediatrics, University of California, San Francisco, California, USA.

Toxoplasma gondii is a ubiquitous, obligate intracellular parasite capable of crossing the placenta to cause spontaneous abortion, pre-term labor or significant disease in the surviving neonate. Exploration of the cellular and histological components of the placental barrier is in its infancy, and both how and where T. gondii breaches it is unknown. The human placenta presents two anatomical interfaces between maternal cells and fetal cells (trophoblasts): 1) the villous region where maternal blood bathes syncytialized trophoblasts for nutrient exchange; and, 2) the maternal decidua, where mononuclear, extravillous trophoblasts anchor the villous region to the uterus. Using first-trimester human placental explants, we demonstrate that the latter site is significantly more vulnerable to infection, despite presenting a vastly smaller surface. This is consistent with past findings concerning two vertically transmitted viruses and one bacterium. We further explore whether three genetically distinct T. gondii types (I, II and III) are capable of preferential placental infection and survival in this model. We find no difference in these strains' ability to infect placental explants; however, slightly slower growth is evident in Type II (Pru) parasites relative to other cell types although this did not quite achieve statistical significance.

PMID:22083708[PubMed - as supplied by publisher]

Tuesday, November 15, 2011

Oral oocyst-induced mouse model of toxoplasmosis

Parasitology. 2011 Nov 14:1-13. [Epub ahead of print]

Oral oocyst-induced mouse model of toxoplasmosis: effect of infection with Toxoplasma gondii strains of different genotypes, dose, and mouse strains (transgenic, out-bred, in-bred) on pathogenesis and mortality.

Dubey JP, Ferreira LR, Martins J, McLeod R.

SourceUnited States Department of Agriculture, Animal Natural Resources Institute, Animal Parasitic Disease Laboratory, BARC-East, Building. 1001, Beltsville, MD 20705-2350, USA.

SUMMARYHumans and other hosts acquire Toxoplasma gondii infection by ingesting tissue cysts in undercooked meat, or by food or drink contaminated with oocysts. Currently, there is no vaccine to prevent clinical disease due this parasite in humans, although, various T. gondii vaccine candidates are being developed. Mice are generally used to test the protective efficacy of vaccines because they are susceptible, reagents are available to measure immune parameters in mice, and they are easily managed in the laboratory. In the present study, pathogenesis of toxoplasmosis was studied in mice of different strains, including Human Leukocyte Antigen (HLA) transgenic mice infected with different doses of T. gondii strains of different genotypes derived from several countries. Based on many experiments, the decreasing order of infectivity and pathogenicity of oocysts was: C57BL/6 background interferon gamma gene knock out (KO), HLA-A*1101, HLA-A*0201, HLA-B*0702, Swiss Webster, C57/black, and BALB/c. Mice fed as few as 1 oocyst of Type I and several atypical strains died of acute toxoplasmosis within 21 days p.i. Some Type II, and III strains were less virulent. The model developed herein should prove to be extremely useful for testing vaccines because it is possible to accurately quantitate a challenge inoculum, test the response to different strains of T. gondii using the same preparations of oocysts which are stable for up to a year, and to have highly reproducible responses to the infection.

PMID:22078010[PubMed - as supplied by publisher]

The placenta: a main role in congenital toxoplasmosis

Trends Parasitol. 2011 Nov 11. [Epub ahead of print]

The placenta: a main role in congenital toxoplasmosis?

Robert-Gangneux F, Murat JB, Fricker-Hidalgo H, Brenier-Pinchart MP, Gangneux JP, Pelloux H.

SourceLaboratoire de Parasitologie-Mycologie, Centre Hospitalier et Universitaire de Rennes, Rennes, France; EA4427-SERAIC, IRSET (Institut de Recherche en Santé Environnement Travail), Université Rennes 1, Rennes, France.

Systemic infections, such as toxoplasmosis, acquired during pregnancy can lead to placental infection and have profound effects on the mother-to-child relationship and the success of pregnancy. Placental permeability to Toxoplasma gondii is a main parameter that determines parasite transmission to the foetus, and the use of antibiotics to decrease placental parasite load and prevent congenital toxoplasmosis has been suggested for decades. Although parasitological examination of the placenta at birth is commonly used to diagnose neonatal congenital toxoplasmosis, this approach can be controversial. Here we argue in favour of placental examination for both diagnostic and epidemiological purposes.

Copyright © 2011 Elsevier Ltd. All rights reserved.

PMID:22079164[PubMed - as supplied by publisher]

Sunday, November 13, 2011

DNA vaccination with a gene encoding Toxoplasma gondii GRA6 induces partial protection against toxoplasmosis in BALB/c mice

Parasit Vectors. 2011 Nov 9;4(1):213. [Epub ahead of print]

DNA vaccination with a gene encoding Toxoplasma gondii GRA6 induces partial protection against toxoplasmosis in BALB/c mice.

Sun XM, Zou J, Saeed A A E, Yan WC, Liu XY, Suo X, Wang H, Chen QJ.

BACKGROUND: Infection with protozoa Toxoplasma gondii causes serious public health problems and is of great economic importance worldwide. Protection from acute toxoplasmosis is known to be mediated by CD8+ T cells, but the T. gondii antigens and host genes required for eliciting protective immunity have been poorly defined. The T. gondii dense granule protein 6 (GRA6), recently proved to be highly immunogenic, produces fully immune protection in T. gondii infected BALB/c mice with an H-2Ld gene. The CD8+ T cell response of H-2Ld mice infected by the T. gondii strain seemed to target entirely to a single GRA6 peptide HF10-H-2Ld complex.

RESULTS: To determine whether GRA6-based DNA vaccine can elicit protective immune response to T. gondii in BALB/c mice, we constructed a eukaryotic expression vector pcDNA3.1-HisGRA6 and tested its immunogenicity in mouse model. BALB/c mice were vaccinated intramuscularly with three doses of GRA6 DNA and then challenged with a lethal dose of T. gondii RH strain tachyzoites. All immunized mice developed high levels of serum anti-GRA6 IgG antibodies, and in vitro splenocyte proliferation was strongly enhanced in mice adjuvanted with levamisole (LMS). Immunization with pcDNA3.1-HisGRA6 with LMS resulted in 53.3% survival of challenged BALB/c mice as compared to 40% survival of BALB/c without levamisole. Additionally, immunized Kunming mice without an allele of H-2Ld failed to survive.

CONCLUSIONS: Our result supports the concept that the immune response is MHC restricted. This study has a major implication for vaccine designs using a single antigen in a population with diverse MHC class I alleles.

PMID:22070984[PubMed - as supplied by publisher]

Protozoan Parasite Toxoplasma gondii Manipulates Mate Choice in Rats by Enhancing Attractiveness of Males

PLoS One. 2011;6(11):e27229. Epub 2011 Nov 2.

Protozoan Parasite Toxoplasma gondii Manipulates Mate Choice in Rats by Enhancing Attractiveness of Males.

Dass SA, Vasudevan A, Dutta D, Soh LJ, Sapolsky RM, Vyas A.

SourceSchool of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore.

Females in various species typically avoid males infected with parasites, while parasite-free males advertise their status through conspicuous phenotypic traits. This process selects for heritable resistance and reduces direct exposure of the female to parasites. Coevolving parasites are likely to attempt to circumvent this obstacle. In this paper, we demonstrate a case of parasitic manipulation of host mate choice. We report that Toxoplasma gondii, a sexually transmitted infection of brown rats, enhances sexual attractiveness of infected males. Thus under some evolutionary niches, parasites can indeed manipulate host sexual signaling to their own advantage.

PMID:22073295[PubMed - in process]

A Monomorphic Haplotype of Chromosome Ia Is Associated with Widespread Success in Clonal and Nonclonal Populations of Toxoplasma gondii

MBio. 2011 Nov 8;2(6). pii: e00228-11. doi: 10.1128/mBio.00228-11. Print 2011.

A Monomorphic Haplotype of Chromosome Ia Is Associated with Widespread Success in Clonal and Nonclonal Populations of Toxoplasma gondii.

Khan A, Miller N, Roos DS, Dubey JP, Ajzenberg D, Dardé ML, Ajioka JW, Rosenthal B, Sibley LD.

SourceDepartment of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.

ABSTRACT Toxoplasma gondii is a common parasite of animals that also causes a zoonotic infection in humans. Previous studies have revealed a strongly clonal population structure that is shared between North America and Europe, while South American strains show greater genetic diversity and evidence of sexual recombination. The common inheritance of a monomorphic version of chromosome Ia (referred to as ChrIa*) among three clonal lineages from North America and Europe suggests that inheritance of this chromosome might underlie their recent clonal expansion. To further examine the diversity and distribution of ChrIa, we have analyzed additional strains with greater geographic diversity. Our findings reveal that the same haplotype of ChrIa* is found in the clonal lineages from North America and Europe and in older lineages in South America, where sexual recombination is more common. Although lineages from all three continents harbor the same conserved ChrIa* haplotype, strains from North America and Europe are genetically separate from those in South America, and these respective geographic regions show limited evidence of recent mixing. Genome-wide, array-based profiling of polymorphisms provided evidence for an ancestral flow from particular older southern lineages that gave rise to the clonal lineages now dominant in the north. Collectively, these data indicate that ChrIa* is widespread among nonclonal strains in South America and has more recently been associated with clonal expansion of specific lineages in North America and Europe. These findings have significant implications for the spread of genetic loci influencing transmission and virulence in pathogen populations. IMPORTANCE Understanding parasite population structure is important for evaluating the potential spread of pathogenicity determinants between different geographic regions. Examining the genetic makeup of different isolates of Toxoplasma gondii from around the world revealed that chromosome Ia is highly homogeneous among lineages that predominate on different continents and within genomes that were otherwise quite divergent. This pattern of recent shared ancestry is highly unusual and suggests that some gene(s) found on this chromosome imparts an unusual fitness advantage that has resulted in its recent spread. Although the basis for the conservation of this particularly homogeneous chromosome is unknown, it may have implications for the transmission of infection and spread of human disease.

PMID:22068979[PubMed - in process]

A Toxoplasma gondii mutant highlights the importance of translational regulation in the apicoplast during animal infection

Mol Microbiol. 2011 Nov 7. doi: 10.1111/j.1365-2958.2011.07879.x. [Epub ahead of print]

A Toxoplasma gondii mutant highlights the importance of translational regulation in the apicoplast during animal infection.

Payne TM, Payne AJ, Knoll LJ.

SourceDepartment of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA.

Toxoplasma gondii is an obligate intracellular parasite of all warm-blooded animals. We previously described a forward genetic screen to identify T. gondii mutants defective in the establishment of a chronic infection. One of the mutants isolated was disrupted in the 3' untranslated region (3'UTR) of an orthologue of bacterial translation elongation factor G (EFG). The mutant does not have a growth defect in tissue culture. Genetic complementation of this mutant with the genomic locus of TgEFG restores virulence in an acute infection mouse model. Epitope tagged TgEFG localized to the apicoplast, via a non-canonical targeting signal, where it functions as an elongation factor for translation in the apicoplast. Comparisons of TgEFG expression constructs with wild-type or mutant 3'UTRs showed that a wild-type 3'UTR is necessary for translation of TgEFG. In tissue culture, the TgEFG transcript is equally abundant in wild-type and mutant parasites; however, during an animal infection, the TgEFG transcript is increased more than threefold in the mutant. These results highlight that in tissue culture, translation in the apicoplast can be diminished, but during an animal infection, translation in the apicoplast must be fully functional.

© 2011 Blackwell Publishing Ltd.

PMID:22059956[PubMed - as supplied by publisher]

Insights into inflammatory bowel disease using Toxoplasma gondii as an infectious trigger

Immunol Cell Biol. 2011 Nov 8. doi: 10.1038/icb.2011.93. [Epub ahead of print]

Insights into inflammatory bowel disease using Toxoplasma gondii as an infectious trigger.

Egan CE, Cohen SB, Denkers EY.

SourceDepartment of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA.

Oral infection of certain inbred mouse strains with the protozoan Toxoplasma gondii triggers inflammatory pathology resembling lesions seen during human inflammatory bowel disease, in particular Crohn's disease (CD). Damage triggered by the parasite is largely localized to the distal portion of the small intestine, and as such is one of only a few models for ileal inflammation. This is important because ileal involvement is a characteristic of CD in over two-thirds of patients. The disease induced by Toxoplasma is mediated by Th1 cells and the cytokines tumor necrosis factor-α and interferon-γ. Inflammation is dependent upon IL-23, also identified by genome-wide association studies as a risk factor in CD. Development of lesions is concomitant with emergence of E. coli that display enhanced adhesion to the intestinal epithelium and subepithelial translocation. Furthermore, depletion of gut flora renders mice resistant to Toxoplasma-triggered ileitis. Recent findings suggest complex CCR2-dependent interactions between lamina propria T cells and intraepithelial lymphocytes in fueling proinflammatory pathology in the intestine. The advantage of the Toxoplasma model is that disease develops rapidly (within 7-10 days of infection) and can be induced in immunodeficient mice by adoptive transfer of mucosal T cells from infected donors. We propose that Toxoplasma acts as a trigger setting into motion a series of events culminating in loss of tolerance in the intestine and emergence of pathogenic T cell effectors. The Toxoplasma trigger model is providing new leaps in our understanding of immunity in the intestine.Immunology and Cell Biology advance online publication, 8 November 2011; doi:10.1038/icb.2011.93.

PMID:22064707[PubMed - as supplied by publisher]

Wednesday, November 02, 2011

Molecular dissection of novel trafficking and processing of the T. gondii rhoptry metalloprotease Toxolysin-1

Traffic. 2011 Oct 28. doi: 10.1111/j.1600-0854.2011.01308.x. [Epub ahead of print]

Molecular dissection of novel trafficking and processing of the T. gondii rhoptry metalloprotease Toxolysin-1.

Hajagos BE, Turetzky JM, Peng ED, Cheng SJ, Ryan CM, Souda P, Whitelegge JP, Lebrun M, Dubremetz JF, Bradley PJ.

SourceDepartment of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles CA 90095-1489 USA Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behaviour, David Geffen School of Medicine, University of California, Los Angeles, California UMR 5539, Centre National de la Recherche Scientifique, Université de Montpellier 2, Montpellier, France.

Toxoplasma gondii utilizes specialized secretory organelles called rhoptries to invade and hijack its host cell. Many rhoptry proteins are proteolytically processed at a highly conserved SΦXE site to remove organellar targeting sequences that may also affect protein activity. We have studied the trafficking and biogenesis of a secreted rhoptry metalloprotease with homology to insulysin that we named Toxolysin-1 (TLN1). Through genetic ablation and molecular dissection of TLN1 we have identified the smallest rhoptry targeting domain yet reported and expanded the consensus sequence of the rhopty pro-domain cleavage site. In addition to removal of its pro-domain, Toxolysin-1 undergoes a C-terminal cleavage event that occurs at a processing site not previously seen in Toxoplasma rhoptry proteins. While pro-domain cleavage occurs in the nascent rhoptries, processing of the C-terminal region precedes commitment to rhoptry targeting, suggesting that it is mediated by a different maturase, and we have identified residues critical for proteolysis. We have additionally shown that both pieces of TLN1 associate in a detergent resistant complex, formation of which is necessary for trafficking of the C-terminal portion to the rhoptries. Together, these studies reveal novel processing and trafficking events that are present in the protein constituents of this unusual secretory organelle.

© 2011 John Wiley & Sons A/S.

PMID:22035499[PubMed - as supplied by publisher]

Methods to produce and safely work with large numbers of Toxoplasma gondii oocysts and bradyzoite cysts

J Microbiol Methods. 2011 Oct 20. [Epub ahead of print]

Methods to produce and safely work with large numbers of Toxoplasma gondii oocysts and bradyzoite cysts.

Fritz H, Barr B, Packham A, Melli A, Conrad PA.

SourceDepartment of Pathology, Microbiology and Immunology, School of Veterinary Medicine, 1 Shields Avenue, University of California Davis, CA 95616, USA.

Two major obstacles to conducting studies with Toxoplasma gondii oocysts are the difficulty in reliably producing large numbers of this life stage and safety concerns because the oocyst is the most environmentally resistant stage of this zoonotic organism. Oocyst production requires oral infection of the definitive feline host with adequate numbers of T. gondii organisms to obtain unsporulated oocysts that are shed in the feces for 3-10days after infection. Since the most successful and common mode of experimental infection of kittens with T. gondii is by ingestion of bradyzoite tissue cysts, the first step in successful oocyst production is to ensure a high bradyzoite tissue cyst burden in the brains of mice that can be used for the oral inoculum. We compared two methods for producing bradyzoite brain cysts in mice, by infecting them either orally or subcutaneously with oocysts. In both cases, oocysts derived from a low passage T. gondii Type II strain (M4) were used to infect eight-ten week-old Swiss Webster mice. First the number of bradyzoite cysts that were purified from infected mouse brains was compared. Then to evaluate the effect of the route of oocyst inoculation on tissue cyst distribution in mice, a second group of mice was infected with oocysts by one of each route and tissues were examined by histology. In separate experiments, brains from infected mice were used to infect kittens for oocyst production. Greater than 1.3 billion oocysts were isolated from the feces of two infected kittens in the first production and greater than 1.8 billion oocysts from three kittens in the second production. Our results demonstrate that oral delivery of oocysts to mice results in both higher cyst loads in the brain and greater cyst burdens in other tissues examined as compared to those of mice that received the same number of oocysts subcutaneously. The ultimate goal in producing large numbers of oocysts in kittens is to generate adequate amounts of starting material for oocyst studies. Given the potential risks of working with live oocysts in the laboratory, we also tested a method of oocyst inactivation by freeze-thaw treatment. This procedure proved to completely inactivate oocysts without evidence of significant alteration of the oocyst molecular integrity.

Copyright © 2011. Published by Elsevier B.V.

PMID:22037023[PubMed - as supplied by publisher]

Movable computer ruler (MCR): A new method for measuring the size of Toxoplasma gondii cysts, tachyzoites and other selected parasites

Exp Parasitol. 2011 Oct 20. [Epub ahead of print]

Movable computer ruler (MCR): A new method for measuring the size of Toxoplasma gondii cysts, tachyzoites and other selected parasites

Otify YZ

SourceDepartment Parasitology, Faculty of Veterinary Medicine, Alexandria University, Edfina, Behira 22758, Egypt.

A new method for measuring the size of parasites and other objects using optical microscopy was developed using a specifically designed movable computer ruler (MCR) derived from digital images of a stage micrometer. Subsequently, MCR can be superimposed on images of parasites to measure their size. MCR derived from the stage micrometer under a particular objective lens can be used to measure the size of an object acquired by the same lens/microscope/camera system. The conditions are fixed for every superimposed image including width, height, pixel number and density. The MCR was tested using selected parasites, and shown to be as accurate as the ocular micrometer disk, screw micrometer eyepiece and image analysis software. The lower technical complexity of the MCR method makes it applicable even in laboratories with limited resources.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID:22041100[PubMed - as supplied by publisher]