1
|
Kolawole BJ, Nwoha RIO, Erin JP, Orakpoghenor O. Probiotic administration enhanced antitrypanosomal effects of diminazene aceturate in dogs experimentally infected with Trypanosoma brucei brucei. JOURNAL OF COMPLEMENTARY & INTEGRATIVE MEDICINE 2022; 19:705-709. [PMID: 35704656 DOI: 10.1515/jcim-2020-0451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
OBJECTIVES This study demonstrated the enhancing actions of probiotic on the antitrypanosomal effects of diminazene aceturate in dogs experimentally infected with Trypanosoma brucei brucei. METHODS Twenty (20) apparently healthy adult local dogs of both sexes were randomly divided into five groups each containing four dogs. Group I were uninfected and untreated while groups III, IV and V were infected. Groups II, III, IV and V were administered multispecies probiotic (MSP) and/or diminazene aceturate (DA). Parasitaemia was determined, clinical signs recorded and blood collected for haematology. RESULTS Results revealed T. b. brucei prepatent periods of 4.75 ± 0.25, (4-5) days and significant decrease of parasitaemia, clinical signs and mortality in groups IV and V compared to group III. Mortalities of 100% (group III), 25% (group IV) and 0% (group V) were recorded. Mean packed cells volume, haemoglobin concentration and red blood cells count showed no significant difference in groups I, II, and V, but were significantly decreased in groups III and IV post-treatment. CONCLUSIONS The administration of MSP to infected dogs enhanced the antitrypanosomal effects of diminazene aceturate.
Collapse
Affiliation(s)
| | | | - Juwon Pius Erin
- Department of Veterinary Pathology, Ahmadu Bello University, Zaria, Nigeria
| | | |
Collapse
|
2
|
Stijlemans B, Schoovaerts M, De Baetselier P, Magez S, De Trez C. The Role of MIF and IL-10 as Molecular Yin-Yang in the Modulation of the Host Immune Microenvironment During Infections: African Trypanosome Infections as a Paradigm. Front Immunol 2022; 13:865395. [PMID: 35464430 PMCID: PMC9022210 DOI: 10.3389/fimmu.2022.865395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 03/14/2022] [Indexed: 11/13/2022] Open
Abstract
African trypanosomes are extracellular flagellated unicellular protozoan parasites transmitted by tsetse flies and causing Sleeping Sickness disease in humans and Nagana disease in cattle and other livestock. These diseases are usually characterized by the development of a fatal chronic inflammatory disease if left untreated. During African trypanosome infection and many other infectious diseases, the immune response is mediating a see-saw balance between effective/protective immunity and excessive infection-induced inflammation that can cause collateral tissue damage. African trypanosomes are known to trigger a strong type I pro-inflammatory response, which contributes to peak parasitaemia control, but this can culminate into the development of immunopathologies, such as anaemia and liver injury, if not tightly controlled. In this context, the macrophage migration inhibitory factor (MIF) and the interleukin-10 (IL-10) cytokines may operate as a molecular “Yin-Yang” in the modulation of the host immune microenvironment during African trypanosome infection, and possibly other infectious diseases. MIF is a pleiotropic pro-inflammatory cytokine and critical upstream mediator of immune and inflammatory responses, associated with exaggerated inflammation and immunopathology. For example, it plays a crucial role in the pro-inflammatory response against African trypanosomes and other pathogens, thereby promoting the development of immunopathologies. On the other hand, IL-10 is an anti-inflammatory cytokine, acting as a master regulator of inflammation during both African trypanosomiasis and other diseases. IL-10 is crucial to counteract the strong MIF-induced pro-inflammatory response, leading to pathology control. Hence, novel strategies capable of blocking MIF and/or promoting IL-10 receptor signaling pathways, could potentially be used as therapy to counteract immunopathology development during African trypanosome infection, as well as during other infectious conditions. Together, this review aims at summarizing the current knowledge on the opposite immunopathological molecular “Yin-Yang” switch roles of MIF and IL-10 in the modulation of the host immune microenvironment during infection, and more particularly during African trypanosomiasis as a paradigm.
Collapse
Affiliation(s)
- Benoit Stijlemans
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.,Myeloid Cell Immunology Laboratory, Vlaams Instituut voor Biotechnologie (VIB) Centre for Inflammation Research, Brussels, Belgium
| | - Maxime Schoovaerts
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Patrick De Baetselier
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.,Myeloid Cell Immunology Laboratory, Vlaams Instituut voor Biotechnologie (VIB) Centre for Inflammation Research, Brussels, Belgium
| | - Stefan Magez
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.,Laboratory of Biomedical Research, Ghent University Global Campus, Incheon, South Korea
| | - Carl De Trez
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| |
Collapse
|
3
|
Kieft R, Zhang Y, Marand AP, Moran JD, Bridger R, Wells L, Schmitz RJ, Sabatini R. Identification of a novel base J binding protein complex involved in RNA polymerase II transcription termination in trypanosomes. PLoS Genet 2020; 16:e1008390. [PMID: 32084124 PMCID: PMC7055916 DOI: 10.1371/journal.pgen.1008390] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 03/04/2020] [Accepted: 01/08/2020] [Indexed: 11/18/2022] Open
Abstract
Base J, β-D-glucosyl-hydroxymethyluracil, is a modification of thymine DNA base involved in RNA Polymerase (Pol) II transcription termination in kinetoplastid protozoa. Little is understood regarding how specific thymine residues are targeted for J-modification or the mechanism of J regulated transcription termination. To identify proteins involved in J-synthesis, we expressed a tagged version of the J-glucosyltransferase (JGT) in Leishmania tarentolae, and identified four co-purified proteins by mass spectrometry: protein phosphatase (PP1), a homolog of Wdr82, a potential PP1 regulatory protein (PNUTS) and a protein containing a J-DNA binding domain (named JBP3). Gel shift studies indicate JBP3 is a J-DNA binding protein. Reciprocal tagging, co-IP and sucrose gradient analyses indicate PP1, JGT, JBP3, Wdr82 and PNUTS form a multimeric complex in kinetoplastids, similar to the mammalian PTW/PP1 complex involved in transcription termination via PP1 mediated dephosphorylation of Pol II. Using RNAi and analysis of Pol II termination by RNA-seq and RT-PCR, we demonstrate that ablation of PNUTS, JBP3 and Wdr82 lead to defects in Pol II termination at the 3'-end of polycistronic gene arrays in Trypanosoma brucei. Mutants also contain increased antisense RNA levels upstream of transcription start sites, suggesting an additional role of the complex in regulating termination of bi-directional transcription. In addition, PNUTS loss causes derepression of silent Variant Surface Glycoprotein genes involved in host immune evasion. Our results suggest a novel mechanistic link between base J and Pol II polycistronic transcription termination in kinetoplastids.
Collapse
Affiliation(s)
- Rudo Kieft
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Yang Zhang
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Alexandre P. Marand
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Jose Dagoberto Moran
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Robert Bridger
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Lance Wells
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Robert J. Schmitz
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Robert Sabatini
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
- * E-mail:
| |
Collapse
|
4
|
Deleeuw V, Phạm HTT, De Poorter I, Janssens I, De Trez C, Radwanska M, Magez S. Trypanosoma brucei brucei causes a rapid and persistent influx of neutrophils in the spleen of infected mice. Parasite Immunol 2019; 41:e12664. [PMID: 31325372 PMCID: PMC6771705 DOI: 10.1111/pim.12664] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 06/29/2019] [Accepted: 07/16/2019] [Indexed: 12/27/2022]
Abstract
Trypanosomosis is a chronic parasitic infection, affecting both humans and livestock. A common hallmark of experimental murine infections is the occurrence of inflammation and the associated remodelling of the spleen compartment. The latter involves the depletion of several lymphocyte populations, the induction of T‐cell‐mediated immune suppression, and the activation of monocyte/macrophage cell populations. Here, we show that in experimental T b brucei infections in mice, these changes are accompanied by the alteration of the spleen neutrophil compartment. Indeed, mature neutrophils are rapidly recruited to the spleen, and cell numbers remain elevated during the entire infection. Following the second peak of parasitemia, the neutrophil cell influx coincides with the rapid reduction of splenic marginal zone (MZ)B and follicular (Fo)B cells, as well as CD8+ T and NK1.1+ cells, the latter encompassing both natural killer (NK) and natural killer T (NKT) cells. This report is the first to show a comprehensive overview of all alterations in spleen cell populations, measured with short intervals throughout the entire course of an experimental T b brucei infection. These data provide new insights into the dynamic interlinked changes in spleen cell numbers associated with trypanosomosis‐associated immunopathology.
Collapse
Affiliation(s)
- Violette Deleeuw
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Laboratory for Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium.,Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
| | - Hien Thi Thu Phạm
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
| | - Isabel De Poorter
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Laboratory for Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium.,Department of Hematology, Erasmus MC, Rotterdam, The Netherlands
| | - Ibo Janssens
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Laboratory for Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium.,Laboratory for Experimental Hematology, University of Antwerp, Edegem, Belgium
| | - Carl De Trez
- Laboratory for Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium
| | - Magdalena Radwanska
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Stefan Magez
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Laboratory for Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium.,Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
| |
Collapse
|
5
|
Liu D, Tong ML, Lin Y, Liu LL, Lin LR, Yang TC. Insights into the genetic variation profile of tprK in Treponema pallidum during the development of natural human syphilis infection. PLoS Negl Trop Dis 2019; 13:e0007621. [PMID: 31329597 PMCID: PMC6675121 DOI: 10.1371/journal.pntd.0007621] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 08/01/2019] [Accepted: 07/09/2019] [Indexed: 01/25/2023] Open
Abstract
Background Although the tprK gene of Treponema pallidum are thought to play a critical role in the pathogenesis of syphilis, the profile of variations in tprK during the development of human syphilis infection have remained unclear. Methods/Principal findings Through next-generation sequencing, we compared the tprK gene of 14 secondary syphilis patients with that of 14 primary syphilis patients, and the results showed an increased number of variants within the seven V regions of the tprK gene in the secondary syphilis samples. The length of the sequences within each V region also presented a 3-bp changing pattern. Interestingly, the frequencies of predominant sequences within the V regions in the secondary syphilis samples were generally decreased compared with those found in the primary syphilis samples, particularly in the V7 region, where a frequency below 60% was found in up to 57% (8/14) of all secondary samples compared with 7% (1/14) of all primary samples. Moreover, the number of minor variants distributed between frequencies of 10 and 49.9% was increased. The alignment of all amino acid sequences within each V region of the primary and secondary syphilis samples revealed that some amino acid sequences, particularly the amino acid sequences IASDGGAIKH and IASEDGSAGNLKH in V1, were highly stable. Additionally, the amino acid sequences in V6 also exhibited notable intrastrain heterogeneity and were likely to form a strain-specific pattern at the interstrain level. Conclusions The identification of different profiles of the tprK gene in primary and secondary syphilis patients indicated that the tprK gene of T. pallidum undergoes constant variation to result in the best adaptation to the host. The highly stable peptides found in V1 are likely promising potential vaccine components. The highly heterogenetic regions (e.g., V6) could help to understand the role of tprK in immune evasion. Antigenic variation of the TprK antigen has been acknowledged to explain the persistence of Treponema pallidum in the host, however, the profile of variations in tprK during the development of human syphilis infection has not been well characterized. Here, we performed next-generation sequencing to compare the variations in tprK between primary and secondary syphilis samples. The profiles of tprK in the samples at different stages showed differences. A higher amount of pool variants within seven V regions was found in the secondary syphilis samples, and the frequencies of their predominant sequences generally decreased with increases in the number of minor variants with frequencies in the range of 10 to 49.9%. However, the length of variable sequences within the V regions of tprK in the secondary syphilis samples also presented a 3-bp changing pattern. Notably, the amino acid sequences IASDGGAIKH and IASEDGSAGNLKH in V1 not only presented a high proportion of interstrain sharing but also were found at a relatively high frequency (above 80%) in the populations. The sequences in V6 of the samples demonstrated substantial variability at the intra- and interstrain levels. These findings could provide insights into the potential syphilis vaccine components and the role of TprK in immune evasion.
Collapse
Affiliation(s)
- Dan Liu
- Center of Clinical Laboratory, Zhongshan Hospital, School of Medicine, Xiamen University, Xiamen, China
- Institute of Infectious Disease, School of Medicine, Xiamen University, Xiamen, China
| | - Man-Li Tong
- Center of Clinical Laboratory, Zhongshan Hospital, School of Medicine, Xiamen University, Xiamen, China
- Institute of Infectious Disease, School of Medicine, Xiamen University, Xiamen, China
| | - Yong Lin
- Center of Clinical Laboratory, Zhongshan Hospital, School of Medicine, Xiamen University, Xiamen, China
| | - Li-Li Liu
- Center of Clinical Laboratory, Zhongshan Hospital, School of Medicine, Xiamen University, Xiamen, China
- Institute of Infectious Disease, School of Medicine, Xiamen University, Xiamen, China
| | - Li-Rong Lin
- Center of Clinical Laboratory, Zhongshan Hospital, School of Medicine, Xiamen University, Xiamen, China
- Institute of Infectious Disease, School of Medicine, Xiamen University, Xiamen, China
| | - Tian-Ci Yang
- Center of Clinical Laboratory, Zhongshan Hospital, School of Medicine, Xiamen University, Xiamen, China
- Institute of Infectious Disease, School of Medicine, Xiamen University, Xiamen, China
- * E-mail:
| |
Collapse
|
6
|
Abstract
African trypanosomes have been around for more than 100 million years, and have adapted to survival in a very wide host range. While various indigenous African mammalian host species display a tolerant phenotype towards this parasitic infection, and hence serve as perpetual reservoirs, many commercially important livestock species are highly disease susceptible. When considering humans, they too display a highly sensitive disease progression phenotype for infections with Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense, while being intrinsically resistant to infections with other trypanosome species. As extracellular trypanosomes proliferate and live freely in the bloodstream and lymphatics, they are constantly exposed to the immune system. Due to co-evolution, this environment however no longer poses a hostile threat, but has become the niche environment where trypanosomes thrive and obligatory await transmission through the bites of tsetse flies or other haematophagic vectors, ideally without causing severe side infection-associated pathology to their host. Hence, African trypanosomes have acquired various mechanisms to manipulate and control the host immune response, evading effective elimination. Despite the extensive research into trypanosomosis over the past 40 years, many aspects of the anti-parasite immune response remain to be solved and no vaccine is currently available. Here we review the recent work on the different escape mechanisms employed by African Trypanosomes to ensure infection chronicity and transmission potential.
Collapse
|
7
|
Reid TB, Molini BJ, Fernandez MC, Lukehart SA. Antigenic variation of TprK facilitates development of secondary syphilis. Infect Immun 2014; 82:4959-67. [PMID: 25225245 PMCID: PMC4249288 DOI: 10.1128/iai.02236-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 09/04/2014] [Indexed: 12/11/2022] Open
Abstract
Although primary syphilis lesions heal spontaneously, the infection is chronic, with subsequent clinical stages. Healing of the primary chancre occurs as antibodies against outer membrane antigens facilitate opsonophagocytosis of the bacteria by activated macrophages. TprK is an outer membrane protein that undergoes antigenic variation at 7 variable regions, and variants are selected by immune pressure. We hypothesized that individual TprK variants escape immune clearance and seed new disseminated lesions to cause secondary syphilis. As in human syphilis, infected rabbits may develop disseminated secondary skin lesions. This study explores the nature of secondary syphilis, specifically, the contribution of antigenic variation to the development of secondary lesions. Our data from the rabbit model show that the odds of secondary lesions containing predominately TprK variant treponemes is 3.3 times higher than the odds of finding TprK variants in disseminated primary lesions (odds ratio [OR] = 3.3 [95% confidence interval {CI}, 0.98 to 11.0]; P = 0.055) and that 96% of TprK variant secondary lesions are likely seeded by single treponemes. Analysis of antibody responses demonstrates significantly higher antibody titers to tprK variable region sequences found in the inoculum compared to reactivity to tprK variant sequences found in newly arising secondary lesions. This suggests that tprK variants escape the initial immune response raised against the V regions expressed in the inoculum. These data further support a role for TprK in immune evasion and suggest that the ability of TprK variants to persist despite a robust immune response is instrumental in the development of later stages of syphilis.
Collapse
Affiliation(s)
- Tara B Reid
- Interdisciplinary Graduate Program in Pathobiology, Department of Global Health, University of Washington, Seattle, Washington, USA
| | - Barbara J Molini
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Mark C Fernandez
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Sheila A Lukehart
- Interdisciplinary Graduate Program in Pathobiology, Department of Global Health, University of Washington, Seattle, Washington, USA Department of Medicine, University of Washington, Seattle, Washington, USA
| |
Collapse
|
8
|
Effect of probiotic (Saccharomyces cerevisiae) supplementation on immune response in Trypanosoma brucei brucei infected rats. Exp Parasitol 2012; 132:434-9. [DOI: 10.1016/j.exppara.2012.09.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 09/24/2012] [Accepted: 09/26/2012] [Indexed: 11/15/2022]
|
9
|
La Greca F, Magez S. Vaccination against trypanosomiasis: can it be done or is the trypanosome truly the ultimate immune destroyer and escape artist? HUMAN VACCINES 2012; 7:1225-33. [PMID: 22205439 PMCID: PMC3323498 DOI: 10.4161/hv.7.11.18203] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To date, human African trypanosomiasis (HAT) still threatens millions of people throughout sub-Sahara Africa, and new approaches to disease prevention and treatment remain a priority. It is commonly accepted that HAT is fatal unless treatment is provided. However, despite the well-described general symptoms of disease progression during distinct stages of the infection, leading to encephalitic complications, coma and death, a substantial body of evidence has been reported suggesting that natural acquired immunity could occur. Hence, if under favorable conditions natural infections can lead to correct immune activation and immune protection against HAT, the development of an effective anti-HAT vaccine should remain a central goal in the fight against this disease.<br />
In this review, we will (1) discuss the vaccine candidates that have been proposed over the past years, (2) highlight the main obstacles that an efficient anti-trypanosomiasis vaccine needs to overcome and (3) critically reflect on the validity of the widely used murine model for HAT.
Collapse
Affiliation(s)
- Florencia La Greca
- Laboratory for Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium
| | | |
Collapse
|
10
|
The trypanosomatid-specific N terminus of RPA2 is required for RNA polymerase I assembly, localization, and function. EUKARYOTIC CELL 2012; 11:662-72. [PMID: 22389385 DOI: 10.1128/ec.00036-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
African trypanosomes are the only organisms known to use RNA polymerase I (pol I) to transcribe protein-coding genes. These genes include VSG, which is essential for immune evasion and is transcribed from an extranucleolar expression site body (ESB). Several trypanosome pol I subunits vary compared to their homologues elsewhere, and the question arises as to how these variations relate to pol I function. A clear example is the N-terminal extension found on the second-largest subunit of pol I, RPA2. Here, we identify an essential role for this region. RPA2 truncation leads to nuclear exclusion and a growth defect which phenocopies single-allele knockout. The N terminus is not a general nuclear localization signal (NLS), however, and it fails to accumulate unrelated proteins in the nucleus. An ectopic NLS is sufficient to reinstate nuclear localization of truncated RPA2, but it does not restore function. Moreover, NLS-tagged, truncated RPA2 has a different subnuclear distribution to full-length protein and is unable to build stable pol I complexes. We conclude that the RPA2 N-terminal extension does not have a role exclusive to the expression of protein-coding genes, but it is essential for all pol I functions in trypanosomes because it directs trypanosomatid-specific interactions with RPA1.
Collapse
|
11
|
Pletinckx K, Stijlemans B, Pavlovic V, Laube R, Brandl C, Kneitz S, Beschin A, De Baetselier P, Lutz MB. Similar inflammatory DC maturation signatures induced by TNF or Trypanosoma brucei antigens instruct default Th2-cell responses. Eur J Immunol 2011; 41:3479-94. [PMID: 21928284 DOI: 10.1002/eji.201141631] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 07/20/2011] [Accepted: 09/15/2011] [Indexed: 12/14/2022]
Abstract
DCs represent the major cell type leading to polarized T-helper (Th) cell responses in vivo. Here, we asked whether the instruction of murine Th2 responses by DCs matured with the proinflammatory cytokine TNF is qualitatively different from maturation by different types of TLR4/MyD88-dependent variant-specific surface glycoproteins (VSGs) of Trypanosoma brucei (T. brucei). The results obtained by analyzing DC surface markers, Notch ligand mRNA, cytokines, asthma, and experimental autoimmune encephalomyelitis (EAE) models as well as performing microarrays indicate that both types of stimuli induce similar inflammatory, semi-mature DC profiles. DCs matured by TNF or VSG treatment expressed a common inflammatory signature of 24 genes correlating with their Th2-polarization capacity. However, the same 24 genes and 4498 additional genes were expressed by DCs treated with LPS that went on to induce Th1 cells. These findings support the concept of a default pathway for Th2-cell induction in DCs matured under suboptimal or inflammatory conditions, independent of the surface receptors and signaling pathways involved. Our data also indicate that quantitative differences in DC maturation might direct Th2- vs Th1-cell responses, since suboptimally matured inflammatory DCs induce default Th2-cell maturation, whereas fully mature DCs induce Th1-cell maturation.
Collapse
Affiliation(s)
- Katrien Pletinckx
- Institute of Virology and Immunobiology, University of Wuerzburg, Wuerzburg, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Ebbinghaus P, Krücken J. Characterization and tissue-specific expression patterns of the Plasmodium chabaudi cir multigene family. Malar J 2011; 10:272. [PMID: 21929749 PMCID: PMC3189184 DOI: 10.1186/1475-2875-10-272] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 09/19/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Variant antigens expressed on the surface of parasitized red blood cells (pRBCs) are important virulence factors of malaria parasites. Whereas Plasmodium falciparum erythrocyte membrane proteins 1 (PfEMP1) are responsible for sequestration of mature parasites, little is known about putative ligands mediating cytoadherence to host receptors in other Plasmodium species. Candidates include members of the pir superfamily found in the human parasite Plasmodium vivax (vir), in the simian pathogen Plasmodium knowlesi (kir) and in the rodent malarias Plasmodium yoelii (yir), Plasmodium berghei (bir) and Plasmodium chabaudi (cir). The aim of this study was to reveal a potential involvement of cir genes in P. chabaudi sequestration. METHODS Subfamilies of cir genes were identified by bioinformatic analyses of annotated sequence data in the Plasmodium Genome Database. In order to examine tissue-specific differences in the expression of cir mRNAs, RT-PCR with subfamily-specific primers was used. In total, 432 cDNA clones derived from six different tissues were sequenced to characterize the transcribed cir gene repertoire. To confirm differences in transcription profiles of cir genes, restriction fragment length polymorphism (RFLP) analyses were performed to compare different host tissues and to identify changes during the course of P. chabaudi infections in immunocompetent mice. RESULTS The phylogenetic analysis of annotated P. chabaudi putative CIR proteins identified two major subfamilies. Comparison of transcribed cir genes from six different tissues revealed significant differences in the frequency clones belonging to individual cir gene subgroups were obtained from different tissues. Further hints of difference in the transcription of cir genes in individual tissues were obtained by RFLP. Whereas only minimal changes in the transcription pattern of cir genes could be detected during the developmental cycle of the parasites, switching to expression of other cir genes during the course of an infection was observed around or after peak parasitemia. CONCLUSIONS The tissue-specific expression of cir mRNAs found in this study indicates correlation between expression of CIR antigens and distribution of parasites in inner organs. Together with comparable results for other members of the pir superfamily this suggests a role of cir and other pir genes in antigenic variation and sequestration of malaria parasites.
Collapse
Affiliation(s)
- Petra Ebbinghaus
- Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Königsweg 67, 14163 Berlin, Germany
| | | |
Collapse
|
13
|
Oberholzer M, Langousis G, Nguyen HT, Saada EA, Shimogawa MM, Jonsson ZO, Nguyen SM, Wohlschlegel JA, Hill KL. Independent analysis of the flagellum surface and matrix proteomes provides insight into flagellum signaling in mammalian-infectious Trypanosoma brucei. Mol Cell Proteomics 2011; 10:M111.010538. [PMID: 21685506 DOI: 10.1074/mcp.m111.010538] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The flagellum of African trypanosomes is an essential and multifunctional organelle that functions in motility, cell morphogenesis, and host-parasite interaction. Previous studies of the trypanosome flagellum have been limited by the inability to purify flagella without first removing the flagellar membrane. This limitation is particularly relevant in the context of studying flagellum signaling, as signaling requires surface-exposed proteins in the flagellar membrane and soluble signaling proteins in the flagellar matrix. Here we employ a combination of genetic and mechanical approaches to purify intact flagella from the African trypanosome, Trypanosoma brucei, in its mammalian-infectious stage. We combined flagellum purification with affinity-purification of surface-exposed proteins to conduct independent proteomic analyses of the flagellum surface and matrix fractions. The proteins identified encompass a broad range of molecular functionalities, including many predicted to function in signaling. Immunofluorescence and RNA interference studies demonstrate flagellum localization and function for proteins identified and provide insight into mechanisms of flagellum attachment and motility. The flagellum surface proteome includes many T. brucei-specific proteins and is enriched for proteins up-regulated in the mammalian-infectious stage of the parasite life-cycle. The combined results indicate that the flagellum surface presents a diverse and dynamic host-parasite interface that is well-suited for host-parasite signaling.
Collapse
Affiliation(s)
- Michael Oberholzer
- Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, CA 90095, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Stijlemans B, Caljon G, Natesan SKA, Saerens D, Conrath K, Pérez-Morga D, Skepper JN, Nikolaou A, Brys L, Pays E, Magez S, Field MC, De Baetselier P, Muyldermans S. High affinity nanobodies against the Trypanosome brucei VSG are potent trypanolytic agents that block endocytosis. PLoS Pathog 2011; 7:e1002072. [PMID: 21698216 PMCID: PMC3116811 DOI: 10.1371/journal.ppat.1002072] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Accepted: 04/04/2011] [Indexed: 11/19/2022] Open
Abstract
The African trypanosome Trypanosoma brucei, which persists within the bloodstream of the mammalian host, has evolved potent mechanisms for immune evasion. Specifically, antigenic variation of the variant-specific surface glycoprotein (VSG) and a highly active endocytosis and recycling of the surface coat efficiently delay killing mediated by anti-VSG antibodies. Consequently, conventional VSG-specific intact immunoglobulins are non-trypanocidal in the absence of complement. In sharp contrast, monovalent antigen-binding fragments, including 15 kDa nanobodies (Nb) derived from camelid heavy-chain antibodies (HCAbs) recognizing variant-specific VSG epitopes, efficiently lyse trypanosomes both in vitro and in vivo. This Nb-mediated lysis is preceded by very rapid immobilisation of the parasites, massive enlargement of the flagellar pocket and major blockade of endocytosis. This is accompanied by severe metabolic perturbations reflected by reduced intracellular ATP-levels and loss of mitochondrial membrane potential, culminating in cell death. Modification of anti-VSG Nbs through site-directed mutagenesis and by reconstitution into HCAbs, combined with unveiling of trypanolytic activity from intact immunoglobulins by papain proteolysis, demonstrates that the trypanolytic activity of Nbs and Fabs requires low molecular weight, monovalency and high affinity. We propose that the generation of low molecular weight VSG-specific trypanolytic nanobodies that impede endocytosis offers a new opportunity for developing novel trypanosomiasis therapeutics. In addition, these data suggest that the antigen-binding domain of an anti-microbial antibody harbours biological functionality that is latent in the intact immunoglobulin and is revealed only upon release of the antigen-binding fragment. Haemoparasites, such as African trypanosomes, have developed potent immune evasion mechanisms to avoid antibody-mediated elimination. Consequently, trypanosome surface antigen-specific immunoglobulins in the absence of complement are non-trypanocidal. In contrast, certain monovalent nanobodies (Nb), monomeric antigen-binding domains derived from camelid Heavy-Chain Antibodies (HCAb) and which have a much lower molecular weight (15 kDa) than classical antibodies (150 kDa), efficiently lyse trypanosomes both in vitro and in vivo. This is surprising as classically immunoglobulin effector functions are mediated via the Fc-domain, which is absent from the Nb. We demonstrate that the Nb-mediated trypanolysis depends on the low molecular weight, monovalency and high affinity and is associated with loss of motility, a major block to endocytosis, energy depletion and cell death. Overall, targeting the parasite surface with low molecular weight, high affinity Nbs is sufficient to exert a direct therapeutic action. Therefore, the exploitation of Nbs against African trypanosomiasis represents a novel therapeutic strategy. Furthermore, demonstration that a high affinity antigen-binding Nb or Fab fragment lacking an effector domain (i.e., Fc-domain or an attached toxin) can exert a direct biological function, suggests that intact antibodies likely harbour latent functionality which only become revealed upon removal of the Fc-domain.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Antibodies, Protozoan/immunology
- Antibodies, Protozoan/pharmacology
- Antibodies, Protozoan/therapeutic use
- Antibody Affinity
- Cells, Cultured
- Down-Regulation/drug effects
- Endocytosis/drug effects
- Humans
- Mice
- Mice, Inbred C57BL
- Models, Biological
- Models, Molecular
- Molecular Sequence Data
- Nanoparticles
- Trypanocidal Agents/pharmacology
- Trypanocidal Agents/therapeutic use
- Trypanosoma brucei brucei/immunology
- Trypanosoma brucei brucei/metabolism
- Trypanosoma brucei brucei/physiology
- Trypanosoma brucei brucei/ultrastructure
- Trypanosomiasis, African/immunology
- Trypanosomiasis, African/metabolism
- Trypanosomiasis, African/therapy
- Variant Surface Glycoproteins, Trypanosoma/immunology
Collapse
Affiliation(s)
- Benoît Stijlemans
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussels, Brussels, Belgium.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Dobson R, Stockdale C, Lapsley C, Wilkes J, McCulloch R. Interactions among Trypanosoma brucei RAD51 paralogues in DNA repair and antigenic variation. Mol Microbiol 2011; 81:434-56. [PMID: 21615552 PMCID: PMC3170485 DOI: 10.1111/j.1365-2958.2011.07703.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Homologous recombination in Trypanosoma brucei is used for moving variant surface glycoprotein (VSG) genes into expression sites during immune evasion by antigenic variation. A major route for such VSG switching is gene conversion reactions in which RAD51, a universally conserved recombinase, catalyses homology-directed strand exchange. In any eukaryote, RAD51-directed strand exchange in vivo is mediated by further factors, including RAD51-related proteins termed Rad51 paralogues. These appear to be ubiquitously conserved, although their detailed roles in recombination remain unclear. In T. brucei, four putative RAD51 paralogue genes have been identified by sequence homology. Here we show that all four RAD51 paralogues act in DNA repair, recombination and RAD51 subnuclear dynamics, though not equivalently, while mutation of only one RAD51 paralogue gene significantly impedes VSG switching. We also show that the T. brucei RAD51 paralogues interact, and that the complexes they form may explain the distinct phenotypes of the mutants as well as observed expression interdependency. Finally, we document the Rad51 paralogues that are encoded by a wide range of protists, demonstrating that the Rad51 paralogue repertoire in T. brucei is unusually large among microbial eukaryotes and that one member of the protein family corresponds with a key, conserved eukaryotic Rad51 paralogue.
Collapse
Affiliation(s)
- Rachel Dobson
- College of Medical Veterinary and Life Sciences, University of Glasgow, Institute of Infection, Immunity and Inflammation, The Wellcome Trust Centre for Molecular Parasitology, Sir Graeme Davis Building, 120 University Place, Glasgow G128TA, UK
| | | | | | | | | |
Collapse
|
16
|
Lehnert S, Kapitonov V, Thilakarathne PJ, Schuit FC. Modeling the asymmetric evolution of a mouse and rat-specific microRNA gene cluster intron 10 of the Sfmbt2 gene. BMC Genomics 2011; 12:257. [PMID: 21605348 PMCID: PMC3212979 DOI: 10.1186/1471-2164-12-257] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 05/23/2011] [Indexed: 12/18/2022] Open
Abstract
Background The total number of miRNA genes in a genome, expression of which is responsible for the miRNA repertoire of an organism, is not precisely known. Moreover, the question of how new miRNA genes arise during evolution is incompletely understood. Recent data in humans and opossum indicate that retrotranspons of the class of short interspersed nuclear elements have contributed to the growth of microRNA gene clusters. Method We studied a large miRNA gene cluster in intron 10 of the mouse Sfmbt2 gene using bioinformatic tools. Results Mice and rats are unique to harbor a 55-65 Kb DNA sequence in intron 10 of the Sfmbt2 gene. This intronic region is rich in regularly repeated B1 retrotransposons together with inverted self-complementary CA/TG microsatellites. The smallest repeats unit, called MSHORT1 in the mouse, was duplicated 9 times in a tandem head-to-tail array to form 2.5 Kb MLONG1 units. The center of the mouse miRNA gene cluster consists of 13 copies of MLONG1. BLAST analysis of MSHORT1 in the mouse shows that the repeat unit is unique for intron 10 of the Sfmbt2 gene and suggest a dual phase model for growth of the miRNA gene cluster: arrangment of 10 MSHORT1 units into MLONG1 and further duplication of 13 head-to-tail MLONG1 units in the center of the miRNA gene cluster. Rats have a similar arrangment of repeat units in intron 10 of the Sfmbt2 gene. The discrepancy between 65 miRNA genes in the mouse cluster as compared to only 1 miRNA gene in the corresponding rat repeat cluster is ascribed to sequence differences between MSHORT1 and RSHORT1 that result in lateral-shifted, less-stable miRNA precursor hairpins for RSHORT1. Conclusion Our data provides new evidence for the emerging concept that lineage-specific retroposons have played an important role in the birth of new miRNA genes during evolution. The large difference in the number of miRNA genes in two closely related species (65 versus 1, mice versus rats) indicates that this species-specific evolution can be a rapid process.
Collapse
Affiliation(s)
- Stefan Lehnert
- Gene Expression Unit, Department of Molecular Cell Biology, Katholieke Universiteit Leuven
| | | | | | | |
Collapse
|
17
|
Sequencing and analysis of chromosomal extremities of Trypanosoma rangeli in comparison with Trypanosoma cruzi lineages. Parasitol Res 2010; 108:459-66. [DOI: 10.1007/s00436-010-2087-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 09/16/2010] [Indexed: 11/25/2022]
|
18
|
Wang QP, Kawahara T, Horn D. Histone deacetylases play distinct roles in telomeric VSG expression site silencing in African trypanosomes. Mol Microbiol 2010; 77:1237-45. [PMID: 20624217 PMCID: PMC2941730 DOI: 10.1111/j.1365-2958.2010.07284.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2010] [Indexed: 01/10/2023]
Abstract
African trypanosomes evade the host immune response through antigenic variation, which is achieved by periodically expressing different variant surface glycoproteins (VSGs). VSG expression is monoallelic such that only one of approximately 15 telomeric VSG expression sites (ESs) is transcribed at a time. Epigenetic regulation is involved in VSG control but our understanding of the mechanisms involved remains incomplete. Histone deacetylases are potential drug targets for diseases caused by protozoan parasites. Here, using recombinant expression we show that the essential Trypanosoma brucei deacetylases, DAC1 (class I) and DAC3 (class II) display histone deacetylase activity. Both DAC1 and DAC3 are nuclear proteins in the bloodstream stage parasite, while only DAC3 remains concentrated in the nucleus in insect-stage cells. Consistent with developmentally regulated localization, DAC1 antagonizes SIR2rp1-dependent telomeric silencing only in the bloodstream form, indicating a conserved role in the control of silent chromatin domains. In contrast, DAC3 is specifically required for silencing at VSG ES promoters in both bloodstream and insect-stage cells. We conclude that DAC1 and DAC3 play distinct roles in subtelomeric gene silencing and that DAC3 represents the first readily druggable target linked to VSG ES control in the African trypanosome.
Collapse
Affiliation(s)
- Qiao-Ping Wang
- London School of Hygiene and Tropical MedicineKeppel Street, London WC1E 7HT, UK
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Key Laboratory of Tropical Diseases Control, Ministry of Education, Zhongshan Medical College, Sun Yat-Sen UniversityGuangzhou 510275, China
| | - Taemi Kawahara
- London School of Hygiene and Tropical MedicineKeppel Street, London WC1E 7HT, UK
| | - David Horn
- London School of Hygiene and Tropical MedicineKeppel Street, London WC1E 7HT, UK
| |
Collapse
|
19
|
|
20
|
Abstract
Parasitic infections previously seen only in developing tropical settings can be currently diagnosed worldwide due to travel and population migration. Some parasites may directly or indirectly affect various anatomical structures of the heart, with infections manifested as myocarditis, pericarditis, pancarditis, or pulmonary hypertension. Thus, it has become quite relevant for clinicians in developed settings to consider parasitic infections in the differential diagnosis of myocardial and pericardial disease anywhere around the globe. Chagas' disease is by far the most important parasitic infection of the heart and one that it is currently considered a global parasitic infection due to the growing migration of populations from areas where these infections are highly endemic to settings where they are not endemic. Current advances in the treatment of African trypanosomiasis offer hope to prevent not only the neurological complications but also the frequently identified cardiac manifestations of this life-threatening parasitic infection. The lack of effective vaccines, optimal chemoprophylaxis, or evidence-based pharmacological therapies to control many of the parasitic diseases of the heart, in particular Chagas' disease, makes this disease one of the most important public health challenges of our time.
Collapse
|
21
|
Stewart M, Haile S, Jha BA, Cristodero M, Li CH, Clayton C. Processing of a phosphoglycerate kinase reporter mRNA in Trypanosoma brucei is not coupled to transcription by RNA polymerase II. Mol Biochem Parasitol 2010; 172:99-106. [PMID: 20363263 DOI: 10.1016/j.molbiopara.2010.03.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 03/08/2010] [Accepted: 03/27/2010] [Indexed: 11/30/2022]
Abstract
Capping of mRNAs is strictly coupled to RNA polymerase II transcription and there is evidence, mainly from metazoans, that other steps in pre-mRNA processing show a similar linkage. In trypanosomes, however, the mRNA cap is supplied by a trans spliced leader sequence. Thus pre-mRNAs transcribed by RNA Polymerase I are capped by trans splicing, and translation-competent transgenic mRNAs can be produced by RNA Polymerase I and T7 RNA polymerase so long as the primary transcript has a splice acceptor signal. We quantified the efficiency of processing of trypanosome pre-mRNAs produced from a plasmid integrated either at the tubulin locus, or in an rRNA spacer, and transcribed by RNA polymerase II, RNA polymerase I or T7 RNA polymerase. The processing efficiencies were similar for primary transcripts from the tubulin locus, produced by RNA polymerase II, and for RNA from an rRNA spacer, transcribed by RNA polymerase I. Primary transcripts produced by T7 RNA polymerase from the tubulin locus were processed almost as well. There was therefore no evidence for recruitment of the 3'-splicing apparatus by the RNA polymerase. Abundant transcripts transcribed from the rRNA locus by T7 RNA polymerase were somewhat less efficiently processed.
Collapse
Affiliation(s)
- Mhairi Stewart
- Zentrum für Molekularbiologie der Universität Heidelberg, ZMBH-DKFZ Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | | | | | | | | | | |
Collapse
|
22
|
From the endometrium physiology to a comprehensive strategy for the discovery of ovarian cancer biomarkers. Oncol Rev 2010. [DOI: 10.1007/s12156-010-0035-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
|
23
|
Gene expression in trypanosomatid parasites. J Biomed Biotechnol 2010; 2010:525241. [PMID: 20169133 PMCID: PMC2821653 DOI: 10.1155/2010/525241] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 11/04/2009] [Indexed: 12/21/2022] Open
Abstract
The parasites Leishmania spp., Trypanosoma brucei, and Trypanosoma cruzi are the trypanosomatid protozoa that cause the deadly human diseases leishmaniasis, African sleeping sickness, and Chagas disease, respectively. These organisms possess unique mechanisms for gene expression such as constitutive polycistronic transcription of protein-coding genes and trans-splicing. Little is known about either the DNA sequences or the proteins that are involved in the initiation and termination of transcription in trypanosomatids. In silico analyses of the genome databases of these parasites led to the identification of a small number of proteins involved in gene expression. However, functional studies have revealed that trypanosomatids have more general transcription factors than originally estimated. Many posttranslational histone modifications, histone variants, and chromatin modifying enzymes have been identified in trypanosomatids, and recent genome-wide studies showed that epigenetic regulation might play a very important role in gene expression in this group of parasites. Here, we review and comment on the most recent findings related to transcription initiation and termination in trypanosomatid protozoa.
Collapse
|
24
|
Tan C, Hsia RC, Shou H, Haggerty CL, Ness RB, Gaydos CA, Dean D, Scurlock AM, Wilson DP, Bavoil PM. Chlamydia trachomatis-infected patients display variable antibody profiles against the nine-member polymorphic membrane protein family. Infect Immun 2009; 77:3218-26. [PMID: 19487469 PMCID: PMC2715660 DOI: 10.1128/iai.01566-08] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 03/04/2009] [Accepted: 05/17/2009] [Indexed: 11/20/2022] Open
Abstract
Genomic analysis of the Chlamydiaceae has revealed a multigene family encoding large, putatively autotransported polymorphic membrane proteins (Pmps) with nine members in the sexually transmitted pathogen Chlamydia trachomatis. While various pathogenesis-related functions are emerging for the Pmps, observed genotypic and phenotypic variation among several chlamydial Pmps in various Chlamydia species has led us to hypothesize that the pmp gene repertoire is the basis of a previously undetected mechanism of antigenic variation. To test this hypothesis, we chose to examine the serologic response of C. trachomatis-infected patients to each Pmp subtype. Immune serum samples were collected from four populations of patients with confirmed C. trachomatis genital infection: 40 women with pelvic inflammatory disease from Pittsburgh, PA; 27 and 34 adolescent/young females from Oakland, CA, and Little Rock, AR, respectively; and 58 adult male patients from Baltimore, MD. The Pmp-specific antibody response was obtained using immunoblot analysis against each of the nine recombinantly expressed Pmps and quantified by densitometry. Our results show that nearly all C. trachomatis-infected patients mount a strong serologic response against individual or multiple Pmp subtypes and that the antibody specificity profile varies between patients. Moreover, our analysis reveals differences in the strengths and specificities of the Pmp subtype-specific antibody reactivity relating to gender and clinical outcome. Overall, our results indicate that the Pmps elicit various serologic responses in C. trachomatis-infected patients and are consistent with the pmp gene family being the basis of a mechanism of antigenic variation.
Collapse
Affiliation(s)
- Chun Tan
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, 21201, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Abstract
The survival ofTrypanosoma brucei relies on the sucessive expression of a single surface protein gene from a family of around 1,000 genes. This switching appears to be partly dictated by epigenetic changes in chromatin.
Collapse
|
26
|
Magez S, Schwegmann A, Atkinson R, Claes F, Drennan M, De Baetselier P, Brombacher F. The role of B-cells and IgM antibodies in parasitemia, anemia, and VSG switching in Trypanosoma brucei-infected mice. PLoS Pathog 2008; 4:e1000122. [PMID: 18688274 PMCID: PMC2483930 DOI: 10.1371/journal.ppat.1000122] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 07/10/2008] [Indexed: 11/24/2022] Open
Abstract
African trypanosomes are extracellular parasitic protozoa, predominantly transmitted by the bite of the haematophagic tsetse fly. The main mechanism considered to mediate parasitemia control in a mammalian host is the continuous interaction between antibodies and the parasite surface, covered by variant-specific surface glycoproteins. Early experimental studies have shown that B-cell responses can be strongly protective but are limited by their VSG-specificity. We have used B-cell (µMT) and IgM-deficient (IgM−/−) mice to investigate the role of B-cells and IgM antibodies in parasitemia control and the in vivo induction of trypanosomiasis-associated anemia. These infection studies revealed that that the initial setting of peak levels of parasitemia in Trypanosoma brucei–infected µMT and IgM−/− mice occurred independent of the presence of B-cells. However, B-cells helped to periodically reduce circulating parasites levels and were required for long term survival, while IgM antibodies played only a limited role in this process. Infection-associated anemia, hypothesized to be mediated by B-cell responses, was induced during infection in µMT mice as well as in IgM−/− mice, and as such occurred independently from the infection-induced host antibody response. Antigenic variation, the main immune evasion mechanism of African trypanosomes, occurred independently from host antibody responses against the parasite's ever-changing antigenic glycoprotein coat. Collectively, these results demonstrated that in murine experimental T. brucei trypanosomiasis, B-cells were crucial for periodic peak parasitemia clearance, whereas parasite-induced IgM antibodies played only a limited role in the outcome of the infection. African trypanosomiasis is a disease caused by different species of extracellular flagellated protozoan trypanosome parasites. Trypanosomes have developed a mechanism of regular antigenic variation of their variant-specific surface glycoprotein (VSG) coat which allows chronic infection. Replacement of this coat occurs at rapid regular time intervals, allowing the parasite to escape from an effective host antibody responses. So far, primary T-cell independent antibody responses have been described to constitute the main host defense mechanism, relying largely on IgM antibody induction. Using genetically engineered B lymphocyte- or IgM-deficient mouse strains, we show that lack of B-cells or IgM did not prevent infection-associated anemia. More importantly, we show that in the absence of IgM, parasitemia was controlled almost as well as in wild-type mice, with only slightly increased mortality. In addition, we show in vivo that antigenic variation is not affected by the lack of IgM.
Collapse
Affiliation(s)
- Stefan Magez
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), Health Science Faculty, University of Cape Town, and International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
- Department of Molecular and Cellular Recognition, VIB, Brussels, Belgium
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Anita Schwegmann
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), Health Science Faculty, University of Cape Town, and International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
| | - Robert Atkinson
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), Health Science Faculty, University of Cape Town, and International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
| | - Filip Claes
- Laboratory of Serology, Institute for Tropical Medicine “Prins Leopold”, Antwerpen, Belgium
| | - Michael Drennan
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), Health Science Faculty, University of Cape Town, and International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
- Department of Molecular and Cellular Recognition, VIB, Brussels, Belgium
| | - Patrick De Baetselier
- Department of Molecular and Cellular Recognition, VIB, Brussels, Belgium
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Frank Brombacher
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), Health Science Faculty, University of Cape Town, and International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
- * E-mail:
| |
Collapse
|
27
|
Möllenbeck M, Zhou Y, Cavalcanti ARO, Jönsson F, Higgins BP, Chang WJ, Juranek S, Doak TG, Rozenberg G, Lipps HJ, Landweber LF. The pathway to detangle a scrambled gene. PLoS One 2008; 3:e2330. [PMID: 18523559 PMCID: PMC2394655 DOI: 10.1371/journal.pone.0002330] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Accepted: 03/26/2008] [Indexed: 01/22/2023] Open
Abstract
Background Programmed DNA elimination and reorganization frequently occur during cellular differentiation. Development of the somatic macronucleus in some ciliates presents an extreme case, involving excision of internal eliminated sequences (IESs) that interrupt coding DNA segments (macronuclear destined sequences, MDSs), as well as removal of transposon-like elements and extensive genome fragmentation, leading to 98% genome reduction in Stylonychia lemnae. Approximately 20–30% of the genes are estimated to be scrambled in the germline micronucleus, with coding segment order permuted and present in either orientation on micronuclear chromosomes. Massive genome rearrangements are therefore critical for development. Methodology/Principal Findings To understand the process of DNA deletion and reorganization during macronuclear development, we examined the population of DNA molecules during assembly of different scrambled genes in two related organisms in a developmental time-course by PCR. The data suggest that removal of conventional IESs usually occurs first, accompanied by a surprising level of error at this step. The complex events of inversion and translocation seem to occur after repair and excision of all conventional IESs and via multiple pathways. Conclusions/Significance This study reveals a temporal order of DNA rearrangements during the processing of a scrambled gene, with simpler events usually preceding more complex ones. The surprising observation of a hidden layer of errors, absent from the mature macronucleus but present during development, also underscores the need for repair or screening of incorrectly-assembled DNA molecules.
Collapse
Affiliation(s)
| | - Yi Zhou
- Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Andre R. O. Cavalcanti
- Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Franziska Jönsson
- Institute of Cell Biology, University Witten/Herdecke, Witten, Germany
| | - Brian P. Higgins
- Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Wei-Jen Chang
- Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Stefan Juranek
- Institute of Cell Biology, University Witten/Herdecke, Witten, Germany
| | - Thomas G. Doak
- Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Grzegorz Rozenberg
- Institute of Advanced Computer Science, Leiden University, Leiden, The Netherlands
| | - Hans J. Lipps
- Institute of Cell Biology, University Witten/Herdecke, Witten, Germany
| | - Laura F. Landweber
- Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
- * E-mail:
| |
Collapse
|
28
|
|
29
|
Stijlemans B, Baral TN, Guilliams M, Brys L, Korf J, Drennan M, Van Den Abbeele J, De Baetselier P, Magez S. A glycosylphosphatidylinositol-based treatment alleviates trypanosomiasis-associated immunopathology. THE JOURNAL OF IMMUNOLOGY 2007; 179:4003-14. [PMID: 17785839 DOI: 10.4049/jimmunol.179.6.4003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The GPI-anchored trypanosome variant surface glycoprotein (VSG) triggers macrophages to produce TNF, involved in trypanosomiasis-associated inflammation and the clinical manifestation of sleeping sickness. Aiming at inhibiting immunopathology during experimental Trypanosoma brucei infections, a VSG-derived GPI-based treatment approach was developed. To achieve this, mice were exposed to the GPI before an infectious trypanosome challenge. This GPI-based strategy resulted in a significant prolonged survival and a substantial protection against infection-associated weight loss, liver damage, acidosis, and anemia; the latter was shown to be Ab-independent and correlated with reduced macrophage-mediated RBC clearance. In addition, GPI-based treatment resulted in reduced circulating serum levels of the inflammatory cytokines TNF and IL-6, abrogation of infection-induced LPS hypersensitivity, and an increase in circulating IL-10. At the level of trypanosomiasis-associated macrophage activation, the GPI-based treatment resulted in an impaired secretion of TNF by VSG and LPS pulsed macrophages, a reduced expression of the inflammatory cytokine genes TNF, IL-6, and IL-12, and an increased expression of the anti-inflammatory cytokine gene IL-10. In addition, this change in cytokine pattern upon GPI-based treatment was associated with the expression of alternatively activated macrophage markers. Finally, the GPI-based treatment also reduced the infection-associated pathology in Trypanosoma congolense and Trypanosoma evansi model systems as well as in tsetse fly challenge experiments, indicating potential field applicability for this intervention strategy.
Collapse
MESH Headings
- Anemia/therapy
- Animals
- Antigens, CD1/physiology
- Antigens, CD1d
- B-Lymphocyte Subsets/drug effects
- B-Lymphocyte Subsets/pathology
- Disease Models, Animal
- Glycosylphosphatidylinositols/therapeutic use
- Inflammation Mediators/therapeutic use
- Lymphopenia/immunology
- Lymphopenia/parasitology
- Lymphopenia/therapy
- Macrophage Activation/drug effects
- Macrophage Activation/immunology
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Knockout
- Signal Transduction/drug effects
- Signal Transduction/immunology
- Trypanosoma brucei brucei/chemistry
- Trypanosoma brucei brucei/immunology
- Trypanosoma brucei brucei/pathogenicity
- Trypanosomiasis, African/immunology
- Trypanosomiasis, African/pathology
- Trypanosomiasis, African/therapy
- Variant Surface Glycoproteins, Trypanosoma/therapeutic use
Collapse
Affiliation(s)
- Benoît Stijlemans
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussels, Pleinlaan 2, Brussels, Belgium.
| | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Lira CBB, Giardini MA, Neto JLS, Conte FF, Cano MIN. Telomere biology of trypanosomatids: beginning to answer some questions. Trends Parasitol 2007; 23:357-62. [PMID: 17580124 DOI: 10.1016/j.pt.2007.06.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Revised: 04/26/2007] [Accepted: 06/06/2007] [Indexed: 11/26/2022]
Abstract
Studies of telomere structure and maintenance in trypanosomatids have provided insights into the evolutionary origin and conservation of some telomeric components shared by trypanosomes and vertebrates. For example, trypanosomatid telomeres are maintained by telomerase and consist of the canonical TTAGGG repeats, which in Trypanosoma brucei can form telomeric loops (t-loops). However, the telomeric chromatin of trypanosomatids is composed of organism-specific proteins and other proteins that share little sequence similarity with their vertebrate counterparts. Because telomere maintenance mechanisms are essential for genome stability, we propose that the particular features shown by the trypanosome telomeric chromatin hold the key for the design of antiparasitic drugs.
Collapse
Affiliation(s)
- Cristina B B Lira
- Laboratório de Telômeros, Departamento de Genética, Instituto de Biociências, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Botucatu, SP, Brazil
| | | | | | | | | |
Collapse
|
31
|
Genest PA, ter Riet B, Cijsouw T, van Luenen HG, Borst P. Telomeric localization of the modified DNA base J in the genome of the protozoan parasite Leishmania. Nucleic Acids Res 2007; 35:2116-24. [PMID: 17329373 PMCID: PMC1874636 DOI: 10.1093/nar/gkm050] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Base J or β-d-glucosylhydroxymethyluracil is a DNA modification replacing a fraction of thymine in the nuclear DNA of kinetoplastid parasites and of Euglena. J is located in the telomeric sequences of Trypanosoma brucei and in other simple repeat DNA sequences. In addition, J was found in the inactive variant surface glycoprotein (VSG) expression sites, but not in the active expression site of T. brucei, suggesting that J could play a role in transcription silencing in T. brucei. We have now looked at the distribution of J in the genomes of other kinetoplastid parasites. First, we analyzed the DNA sequences immunoprecipitated with a J-antiserum in Leishmania major Friedlin. Second, we investigated the co-migration of J- and telomeric repeat-containing DNA sequences of various kinetoplastids using J-immunoblots and Southern blots of fragmented DNA. We find only ∼1% of J outside the telomeric repeat sequences of Leishmania sp. and Crithidia fasciculata, in contrast to the substantial fraction of non-telomeric J found in T. brucei, Trypanosoma equiperdum and Trypanoplasma borreli. Our results suggest that J is a telomeric base modification, recruited for other (unknown) functions in some kinetoplastids and Euglena.
Collapse
Affiliation(s)
| | | | | | | | - Piet Borst
- *To whom Correspondence should be addressed. +31 20 512 2880+31 20 669 1383
| |
Collapse
|
32
|
Faulkner SD, Oli MW, Kieft R, Cotlin L, Widener J, Shiflett A, Cipriano MJ, Pacocha SE, Birkeland SR, Hajduk SL, McArthur AG. In vitro generation of human high-density-lipoprotein-resistant Trypanosoma brucei brucei. EUKARYOTIC CELL 2007; 5:1276-86. [PMID: 16896212 PMCID: PMC1539141 DOI: 10.1128/ec.00116-06] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The host range of African trypanosomes is influenced by innate protective molecules in the blood of primates. A subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I, apolipoprotein L-I, and haptoglobin-related protein is toxic to Trypanosoma brucei brucei but not the human sleeping sickness parasite Trypanosoma brucei rhodesiense. It is thought that T. b. rhodesiense evolved from a T. b. brucei-like ancestor and expresses a defense protein that ablates the antitrypanosomal activity of human HDL. To directly investigate this possibility, we developed an in vitro selection to generate human HDL-resistant T. b. brucei. Here we show that conversion of T. b. brucei from human HDL sensitive to resistant correlates with changes in the expression of the variant surface glycoprotein (VSG) and abolished uptake of the cytotoxic human HDLs. Complete transcriptome analysis of the HDL-susceptible and -resistant trypanosomes confirmed that VSG switching had occurred but failed to reveal the expression of other genes specifically associated with human HDL resistance, including the serum resistance-associated gene (SRA) of T. b. rhodesiense. In addition, we found that while the original active expression site was still utilized, expression of three expression site-associated genes (ESAG) was altered in the HDL-resistant trypanosomes. These findings demonstrate that resistance to human HDLs can be acquired by T. b. brucei.
Collapse
Affiliation(s)
- Sara D Faulkner
- Josephine Bay Paul Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Güther MLS, Lee S, Tetley L, Acosta-Serrano A, Ferguson MA. GPI-anchored proteins and free GPI glycolipids of procyclic form Trypanosoma brucei are nonessential for growth, are required for colonization of the tsetse fly, and are not the only components of the surface coat. Mol Biol Cell 2006; 17:5265-74. [PMID: 17035628 PMCID: PMC1679689 DOI: 10.1091/mbc.e06-08-0702] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The procyclic form of Trypanosoma brucei exists in the midgut of the tsetse fly. The current model of its surface glycocalyx is an array of rod-like procyclin glycoproteins with glycosylphosphatidylinositol (GPI) anchors carrying sialylated poly-N-acetyllactosamine side chains interspersed with smaller sialylated poly-N-acetyllactosamine-containing free GPI glycolipids. Mutants for TbGPI12, deficient in the second step of GPI biosynthesis, were devoid of cell surface procyclins and poly-N-acetyllactosamine-containing free GPI glycolipids. This major disruption to their surface architecture severely impaired their ability to colonize tsetse fly midguts but, surprisingly, had no effect on their morphology and growth characteristics in vitro. Transmission electron microscopy showed that the mutants retained a cell surface glycocalyx. This structure, and the viability of the mutants in vitro, prompted us to look for non-GPI-anchored parasite molecules and/or the adsorption of serum components. Neither were apparent from cell surface biotinylation experiments but [3H]glucosamine biosynthetic labeling revealed a group of previously unidentified high apparent molecular weight glycoconjugates that might contribute to the surface coat. While characterizing GlcNAc-PI that accumulates in the TbGPI12 mutant, we observed inositolphosphoceramides for the first time in this organism.
Collapse
Affiliation(s)
- Maria Lucia Sampaio Güther
- *Division of Biological Chemistry and Molecular Microbiology, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
| | - Sylvia Lee
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow G11 6NU, Scotland, United Kingdom; and
| | - Laurence Tetley
- Institute of Biomedical and Life Science, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Alvaro Acosta-Serrano
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow G11 6NU, Scotland, United Kingdom; and
| | - Michael A.J. Ferguson
- *Division of Biological Chemistry and Molecular Microbiology, Faculty of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
| |
Collapse
|
34
|
Dai Q, Restrepo BI, Porcella SF, Raffel SJ, Schwan TG, Barbour AG. Antigenic variation by Borrelia hermsii occurs through recombination between extragenic repetitive elements on linear plasmids. Mol Microbiol 2006; 60:1329-43. [PMID: 16796672 PMCID: PMC5614446 DOI: 10.1111/j.1365-2958.2006.05177.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The relapsing fever agent Borrelia hermsii undergoes multiphasic antigenic variation through gene conversion of a unique expression site on a linear plasmid by an archived variable antigen gene. To further characterize this mechanism we assessed the repertoire and organization of archived variable antigen genes by sequencing approximately 85% of plasmids bearing these genes. Most archived genes shared with the expressed gene a <or= 62 nucleotide (nt) region, the upstream homology sequence (UHS), that surrounded the start codon. The 59 archived variable antigen genes were arrayed in clusters with 13 repetitive, 214 nt long downstream homology sequence (DHS) elements distributed among them. A fourteenth DHS element was downstream of the expression locus. Informative nucleotide polymorphisms in UHS regions and DHS elements were applied to the analysis of the expression site of relapse serotypes from 60 infected mice in a prospective study. For most recombinations, the upstream crossover occurred in the UHS's second half, and the downstream crossover was in the DHS's second half. Usually the closest archival DHS element was used, but occasionally a more distant DHS was employed. The downstream extragenic crossover site in B. hermsii contrasts with the upstream [corrected] extragenic crossover site for antigenic variation in African trypanosomes.
Collapse
Affiliation(s)
- Qiyuan Dai
- Departments of Microbiology & Molecular Genetics and Medicine, University of California Irvine, Irvine, California
| | - Blanca I. Restrepo
- Department of Microbiology, University of Texas Health Science Center at San Antonio, Texas
- University of Texas Health Science Center at Houston, School of Public Health Brownsville Regional Campus, Brownsville, Texas
| | - Stephen F. Porcella
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana
| | - Sandra J. Raffel
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana
| | - Tom G. Schwan
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana
| | - Alan G. Barbour
- Departments of Microbiology & Molecular Genetics and Medicine, University of California Irvine, Irvine, California
- Department of Microbiology, University of Texas Health Science Center at San Antonio, Texas
- Corresponding author: Pacific-Southwest Center, 3046 Hewitt Hall, University of California Irvine, Irvine, CA 92697-4028; telephone, +1.949.824.5626; fax, +1.949.824.6452;,
| |
Collapse
|
35
|
van Luenen HGAM, Kieft R, Mussmann R, Engstler M, ter Riet B, Borst P. Trypanosomes change their transferrin receptor expression to allow effective uptake of host transferrin. Mol Microbiol 2006; 58:151-65. [PMID: 16164555 DOI: 10.1111/j.1365-2958.2005.04831.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In its mammalian host, Trypanosoma brucei covers its iron requirements by receptor-mediated uptake of host transferrin (Tf). The Tf-receptor (Tf-R) is a heterodimeric membrane protein encoded by expression site-associated gene (ESAG) 6 and 7 located promoter-proximal in a polycistronic expression site (ES). Each of the 20 ESs encodes a slightly different Tf-R; these differences strongly affect the binding affinity for Tfs of different hosts. The Tf-R encoded in the 221 ES has a low affinity for dog Tf. Transfer of trypanosomes with an active 221 ES to dilute dog serum leads to growth arrest, which they can overcome by switching to another ES encoding a Tf-R with higher affinity for dog Tf. Here we show that trypanosomes can also adapt to dilute dog serum without switching but by replacing the ESAG7 gene in the 221 ES by one from another ES, by deleting ESAG7 from the 221 ES with concomitant upregulation of transcription of ESAG7 in 'silent' ESs, by grossly overproducing the 221 Tf-R or by combinations of these alterations. Our results illustrate the striking genetic flexibility of trypanosomes.
Collapse
Affiliation(s)
- Henri G A M van Luenen
- The Netherlands Cancer Institute, Division of Molecular Biology and Centre for Biomedical Genetics, Plesmanlaan 121, 1060 CX Amsterdam, the Netherlands
| | | | | | | | | | | |
Collapse
|
36
|
Coppel RL, Black CG. Parasite genomes. Int J Parasitol 2005; 35:465-79. [PMID: 15826640 DOI: 10.1016/j.ijpara.2005.01.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Revised: 02/24/2005] [Accepted: 02/24/2005] [Indexed: 01/01/2023]
Abstract
The availability of genome sequences and the associated transcriptome and proteome mapping projects has revolutionised research in the field of parasitology. As more parasite species are sequenced, comparative and phylogenetic comparisons are improving the quality of gene prediction and annotation. Genome sequences of parasites are also providing important data sets for understanding parasite biology and identifying new vaccine candidates and drug targets. We review some of the preliminary conclusions from examination of parasite genome sequences and discuss some of the bioinformatics approaches taken in this analysis.
Collapse
Affiliation(s)
- Ross L Coppel
- Department of Microbiology and the Victorian Bioinformatics Consortium, Monash University, Melbourne, Vic. 3800, Australia.
| | | |
Collapse
|
37
|
Shiflett AM, Bishop JR, Pahwa A, Hajduk SL. Human High Density Lipoproteins Are Platforms for the Assembly of Multi-component Innate Immune Complexes. J Biol Chem 2005; 280:32578-85. [PMID: 16046400 DOI: 10.1074/jbc.m503510200] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human innate immunity to non-pathogenic species of African trypanosomes is provided by human high density lipoprotein (HDL) particles. Here we show that native human HDLs containing haptoglobin-related protein (Hpr), apolipoprotein L-I (apoL-I) and apolipoprotein A-I (apoA-I) are the principle antimicrobial molecules providing protection from trypanosome infection. Other HDL subclasses containing either apoA-I and apoL-I or apoA-I and Hpr have reduced trypanolytic activity, whereas HDL subclasses lacking apoL-I and Hpr are non-toxic to trypanosomes. Highly purified, lipid-free Hpr and apoL-I were both toxic to Trypanosoma brucei brucei but with specific activities at least 500-fold less than those of native HDLs, suggesting that association of these apolipoproteins within the HDL particle was necessary for optimal cytotoxicity. These studies show that HDLs can serve as platforms for the assembly of multiple synergistic proteins and that these assemblies may play a critical role in the evolution of primate-specific innate immunity to trypanosome infection.
Collapse
Affiliation(s)
- April M Shiflett
- Josephine Bay Paul Center, Global Infectious Disease Program, Marine Biological Laboratory, Woods Hole, Massachussetts 02543, USA
| | | | | | | |
Collapse
|
38
|
Abstract
Human African trypanosomiasis or sleeping sickness is caused by infection with two subspecies of the tsetse-fly-vectored haemoflagellate parasite Trypanosoma brucei. Historically, epidemic sleeping sickness has caused massive loss of life, and related animal diseases have had a crucial impact on development in sub-Saharan Africa. After a period of moderately successful control during the mid-part of the 20th century, sleeping sickness incidence is currently rising, and control is hampered by a combination of factors, including civil unrest and the possible development of drug resistance by the parasites. The prevailing view is that the disease is invariably fatal without anti-trypanosomal drug treatment. However, there have also been intriguing reports of wide variations in disease severity as well as evidence of asymptomatic carriers of trypanosomes. These differences in the presentation of the disease will be discussed in the context of our knowledge of the immunology of trypanosomiasis. The impact of dysregulated inflammatory responses in both systemic and CNS pathology will be examined and the potential for host genotype variation in disease severity and control will be discussed.
Collapse
Affiliation(s)
- J M Sternberg
- Zoology Building, School of Biological Sciences, University of Aberdeen, UK.
| |
Collapse
|
39
|
Abstract
Similar to the expression of antigen receptor genes in lymphocytes, the mammalian odorant receptor (OR) genes are expressed in a mutually exclusive and monoallelic manner in olfactory sensory neurons (OSNs). DNA rearrangement has long been regarded as a possible mechanism for the allelic exclusion of the OR genes. However, mice cloned from mature OSN nuclei expressed the full repertoire of ORs, and the possibility of irreversible gene translocation was excluded as a mechanism to activate a single OR gene in each OSN. How is allelic exclusion achieved in the olfactory system? Recent transgenic experiments indicated an inhibitory role of the OR protein in preventing further activation of other OR genes. Stochastic activation of an OR gene and negative-feedback regulation by the OR gene product might ensure the maintenance of the one neuron-one receptor rule in the mammalian olfactory system.
Collapse
Affiliation(s)
- Shou Serizawa
- PRESTO program of Japan Science and Technology Agency, Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan
| | | | | |
Collapse
|
40
|
Chappuis F, Loutan L, Simarro P, Lejon V, Büscher P. Options for field diagnosis of human african trypanosomiasis. Clin Microbiol Rev 2005; 18:133-46. [PMID: 15653823 PMCID: PMC544181 DOI: 10.1128/cmr.18.1.133-146.2005] [Citation(s) in RCA: 219] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human African trypanosomiasis (HAT) due to Trypanosoma brucei gambiense or T. b. rhodesiense remains highly prevalent in several rural areas of sub-Saharan Africa and is lethal if left untreated. Therefore, accurate tools are absolutely required for field diagnosis. For T. b. gambiense HAT, highly sensitive tests are available for serological screening but the sensitivity of parasitological confirmatory tests remains insufficient and needs to be improved. Screening for T. b. rhodesiense infection still relies on clinical features in the absence of serological tests available for field use. Ongoing research is opening perspectives for a new generation of field diagnostics. Also essential for both forms of HAT is accurate determination of the disease stage because of the high toxicity of melarsoprol, the drug most widely used during the neurological stage of the illness. Recent studies have confirmed the high accuracy of raised immunoglobulin M levels in the cerebrospinal fluid for the staging of T. b. gambiense HAT, and a promising simple assay (LATEX/IgM) is being tested in the field. Apart from the urgent need for better tools for the field diagnosis of this neglected disease, improved access to diagnosis and treatment for the population at risk remains the greatest challenge for the coming years.
Collapse
Affiliation(s)
- François Chappuis
- Travel and Migration Medicine Unit, Geneva University Hospital, 24 rue Micheli-du-Crest, 1211 Geneva 14, Switzerland.
| | | | | | | | | |
Collapse
|
41
|
Vanhamme L, Pays E. The trypanosome lytic factor of human serum and the molecular basis of sleeping sickness. Int J Parasitol 2004; 34:887-98. [PMID: 15217727 DOI: 10.1016/j.ijpara.2004.04.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 04/20/2004] [Accepted: 04/20/2004] [Indexed: 02/08/2023]
Abstract
Trypanosoma brucei brucei infects a wide range of mammals but is unable to infect humans because this subspecies is lysed by normal human serum (NHS). The trypanosome lytic factor is associated with High Density Lipoproteins (HDLs). Several HDL-associated components have been proposed as candidate lytic factors, and contradictory hypotheses concerning the mechanism of lysis have been suggested. Elucidation of the process by which Trypanosoma brucei rhodesiense resists lysis and causes human sleeping sickness has indicated that the HDL-bound apolipoprotein L-I (apoL-I) could be the long-sought after lytic component of NHS. This research also allowed the identification of a specific diagnostic DNA probe for T. b. rhodesiense, and may lead to the development of novel anti-trypanosome strategies for use in the field.
Collapse
Affiliation(s)
- Luc Vanhamme
- Department of Molecular Biology, Laboratory of Molecular Parasitology, IBMM, University of Brussels, 12, rue des Professeurs Jeener et Brachet, B6041 Gosselies, Belgium
| | | |
Collapse
|
42
|
Becker M, Aitcheson N, Byles E, Wickstead B, Louis E, Rudenko G. Isolation of the repertoire of VSG expression site containing telomeres of Trypanosoma brucei 427 using transformation-associated recombination in yeast. Genome Res 2004; 14:2319-29. [PMID: 15520294 PMCID: PMC525691 DOI: 10.1101/gr.2955304] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Accepted: 08/14/2004] [Indexed: 11/24/2022]
Abstract
Trypanosoma brucei switches between variant surface glycoproteins (VSGs) allowing immune escape. The active VSG is in one of many telomeric bloodstream form VSG expression sites (BESs), also containing expression site-associated genes (ESAGs) involved in host adaptation. The role of BES sequence diversity in parasite virulence can best be understood through analysis of the full repertoire of BESs from a given T. brucei strain. However, few BESs have been cloned, as telomeres are highly underrepresented in standard libraries. We devised a strategy for isolating the repertoire of T. brucei 427 BES-containing telomeres in Saccaromyces cerevisiae by using transformation-associated recombination (TAR). We isolated 182 T. brucei 427 BES TAR clones, 167 of which could be subdivided into minimally 17 BES groups. This set gives us the first view of the breadth and diversity of BESs from one T. brucei strain. Most BESs ranged between 40 and 70 kb (average, 57 +/- 17 kb) and contained most identified ESAGs. Phylogenetic comparison of the cohort of BES promoter and ESAG6 sequences did not show similar trees, indicating rapid evolution most likely mediated by sequence exchange between BESs. This cloning strategy could be used for any T. brucei strain, facilitating research on the biodiversity of telomeric gene families and host-pathogen interactions.
Collapse
Affiliation(s)
- Marion Becker
- Department of Genetics, University of Leicester, University Road, Leicester LE1 7RH, UK
| | | | | | | | | | | |
Collapse
|
43
|
Amiguet-Vercher A, Pérez-Morga D, Pays A, Poelvoorde P, Van Xong H, Tebabi P, Vanhamme L, Pays E. Loss of the mono-allelic control of the VSG expression sites during the development of Trypanosoma brucei in the bloodstream. Mol Microbiol 2004; 51:1577-88. [PMID: 15009886 DOI: 10.1111/j.1365-2958.2003.03937.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Transcription of the variant surface glycoprotein (VSG) gene of Trypanosoma brucei occurs in a single of multiple polycistronic expression sites (ESs). Analysis of RNA from proliferative long slender (LS) bloodstream forms demonstrated that initiation of transcription occurs in different ESs, but inefficient RNA processing and elongation is linked to RNA polymerase arrest in all except one unit at a time. The pattern of ES transcripts was analysed during the transformation of dividing LS forms into quiescent short stumpy (SS) forms. The results demonstrated that the mono-allelic control allowing preferential RNA production from a given ES stops during this process. Accordingly, the steady-state ES transcripts, particularly the VSG mRNA, were strongly reduced. However, transcripts from the beginning of different ESs were still synthesized, and in vitro run-on transcription analysis indicated that RNA polymerase was still fully associated with the promoter-proximal half of the 'active' ES. Analysis of transcripts from two central tandem genes confirmed the existence of a residual decreasing transcriptional gradient in the 'active' ES of SS forms. Thus, in these forms the RNA polymerase of the ES is inactivated in situ. This inactivation is accompanied by a strong overall reduction of nuclear DNA transcription. Although cAMP is involved in the LS to SS transformation, no direct effect of cAMP was observed on the VSG ES control.
Collapse
MESH Headings
- Alleles
- Animals
- Antigenic Variation
- Base Sequence
- DNA, Protozoan/genetics
- Gene Expression Regulation
- Genes, Protozoan
- Molecular Sequence Data
- RNA, Messenger/genetics
- RNA, Messenger/isolation & purification
- RNA, Messenger/metabolism
- RNA, Protozoan/genetics
- RNA, Protozoan/metabolism
- Transcription, Genetic
- Trypanosoma brucei brucei/genetics
- Trypanosoma brucei brucei/growth & development
- Trypanosomiasis, African/parasitology
- Variant Surface Glycoproteins, Trypanosoma/genetics
Collapse
Affiliation(s)
- Amelia Amiguet-Vercher
- Laboratory of Molecular Parasitology, IBMM, Free University of Brussels, 12, rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
44
|
Tabarés E, Ferguson D, Clark J, Soon PE, Wan KL, Tomley F. Eimeria tenella sporozoites and merozoites differentially express glycosylphosphatidylinositol-anchored variant surface proteins. Mol Biochem Parasitol 2004; 135:123-32. [PMID: 15287593 DOI: 10.1016/j.molbiopara.2004.01.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Little is known about glycosylphosphatidylinositol (GPI)-linked surface proteins in the coccidian parasite Eimeria tenella. Examination of 28,550 EST sequences from the sporozoite and second merozoite developmental stages of the parasite led to the identification of 37 potential GPI-linked variant surface proteins, termed EtSAGs. Analysis of the complete nucleotide sequences of 23 EtSAG genes separated them into two multi-gene families. All the predicted EtSAG proteins (which vary in length from 228 to 271 residues) have an N-terminal hydrophobic signal peptide, a C-terminal hydrophobic GPI signal-anchor peptide and an extracellular domain organised around six cysteine residues, the positions of which are conserved within each family. Using specific antibodies against a small number of recombinant-expressed EtSAGs, the surface localisation and GPI-anchorage of members of both families was confirmed experimentally. Expression of EtSAGs is differentially regulated between the oocyst/sporozoite and second generation merozoite stages, with only one expressed specifically in the sporozoite, a small number expressed in both stages and the majority expressed specifically in the second generation merozoite. Preliminary data support a model in which multiple variant surface antigens are co-expressed on individual parasites, rather than a model of antigenic switching. The biological role(s) of EtSAGs and the effect(s) that expression of a complex repertoire of variant surface antigens by the second generation merozoite has on host adapted immunity are unknown.
Collapse
Affiliation(s)
- Enrique Tabarés
- Division of Molecular Biology, Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
| | | | | | | | | | | |
Collapse
|
45
|
Stijlemans B, Conrath K, Cortez-Retamozo V, Van Xong H, Wyns L, Senter P, Revets H, De Baetselier P, Muyldermans S, Magez S. Efficient targeting of conserved cryptic epitopes of infectious agents by single domain antibodies. African trypanosomes as paradigm. J Biol Chem 2004; 279:1256-61. [PMID: 14527957 DOI: 10.1074/jbc.m307341200] [Citation(s) in RCA: 209] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antigen variation is a successful defense system adopted by several infectious agents to evade the host immune response. The principle of this defense strategy in the African trypanosome paradigm involves a dense packing of variant surface glycoproteins (VSG) exposing only highly variable and immuno-dominant epitopes to the immune system, whereas conserved epitopes become inaccessible for large molecules. Reducing the size of binders that target the conserved, less-immunogenic, cryptic VSG epitopes forms an obvious solution to combat these parasites. This goal was achieved by introducing dromedary Heavy-chain antibodies. We found that only these unique antibodies recognize epitopes common to multiple VSG classes. After phage display of their antigen-binding repertoire, we isolated a single domain antibody fragment with high specificity for the conserved Asn-linked carbohydrate of VSG. In sharp contrast to labeled concanavalin-A that stains only the flagellar pocket where carbohydrates are accessible because of less dense VSG packing, the single domain binder stains the entire surface of viable parasites, irrespective of the VSG type expressed. This corroborates the idea that small antibody fragments, but not larger lectins or conventional antibody fragments, are able to penetrate the dense VSG coat to target their epitope. The diagnostic potential of this fluorescently labeled binder was proven by the direct, selective, and sensitive detection of parasites in blood smears. The employment of this binder as a molecular recognition unit in immuno-toxins designed for trypanosomosis therapy becomes feasible as well. This was illustrated by the specific trypanolysis induced by an antibody::beta-lactamase fusion activating a prodrug.
Collapse
Affiliation(s)
- Benoit Stijlemans
- Department of Cellular and Molecular Interactions, Vlaams Interuniversitair Instituut voor Biotechnologie, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
| | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Biebinger S, Helfert S, Steverding D, Ansorge I, Clayton C. Impaired dimerization and trafficking of ESAG6 lacking a glycosyl-phosphatidylinositol anchor. Mol Biochem Parasitol 2003; 132:93-6. [PMID: 14599669 DOI: 10.1016/j.molbiopara.2003.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Susanne Biebinger
- Zentrum für Molekular Biologie der Universität Heidelberg, Im Nevenheimer Feld 282, 69120, Heidelberg, Germany
| | | | | | | | | |
Collapse
|
47
|
Bell JS, McCulloch R. Mismatch repair regulates homologous recombination, but has little influence on antigenic variation, in Trypanosoma brucei. J Biol Chem 2003; 278:45182-8. [PMID: 12933800 DOI: 10.1074/jbc.m308123200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antigenic variation is critical in the life of the African trypanosome, as it allows the parasite to survive in the face of host immunity and enhance its transmission to other hosts. Much of trypanosome antigenic variation uses homologous recombination of variant surface glycoprotein (VSG)-encoding genes into specialized transcription sites, but little is known about the processes that regulate it. Here we describe the effects on VSG switching when two central mismatch repair genes, MSH2 and MLH1, are mutated. We show that disruption of the parasite mismatch repair system causes an increased frequency of homologous recombination, both between perfectly matched DNA molecules and between DNA molecules with divergent sequences. Mismatch repair therefore provides an important regulatory role in homologous recombination in this ancient eukaryote. Despite this, the mismatch repair system has no detectable role in regulating antigenic variation, meaning that VSG switching is either immune to mismatch selection or that mismatch repair acts in a subtle manner, undetectable by current assays.
Collapse
Affiliation(s)
- Joanna S Bell
- Wellcome Centre for Molecular Parasitology, University of Glasgow, Anderson College, 56 Dumbarton Road, Glasgow G11 6NU, Scotland, United Kingdom
| | | |
Collapse
|
48
|
Avliyakulov NK, Hines JC, Ray DS. Sequence elements in both the intergenic space and the 3' untranslated region of the Crithidia fasciculata KAP3 gene are required for cell cycle regulation of KAP3 mRNA. EUKARYOTIC CELL 2003; 2:671-7. [PMID: 12912886 PMCID: PMC178339 DOI: 10.1128/ec.2.4.671-677.2003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
mRNA levels of several Crithidia fasciculata genes involved in DNA metabolism have previously been found to cycle as cells progress through the cell cycle. Octamer consensus sequences in the 5' untranslated regions (5' UTRs) of these transcripts were shown to be required for cycling of these mRNAs. The KAP3 gene encodes a kinetoplast histone H1-like DNA binding protein, and its mRNA levels cycle in parallel with those of the kinetoplast DNA topoisomerase (TOP2), dihydrofolate reductase-thymidylate synthase (DHFR-TS), and the large subunit of the nuclear single-stranded DNA binding protein (RPA1). KAP3 mRNA contains two octamer consensus sequences in its 3' UTR but none in its 5' UTR. Mutation of these octamer sequences was not sufficient to prevent cycling of a sequence-tagged KAP3 mRNA expressed from a plasmid. Mutation of an octamer sequence contained on the precursor transcript but not on the mRNA, in addition to mutation of the two octamer sequences in the 3' UTR, was necessary to abolish cycling of the mRNA. The requirement for a sequence not present on the mature mRNA indicates that regulation of the mRNA levels by the octamer sequences occurs at or prior to splicing of the transcript. Incompletely processed RNAs containing octamer sequences were also found to accumulate during the cell cycle when the mRNA levels were lowest. These RNA species hybridize to both the KAP3 coding sequence and that of the downstream drug resistance gene, indicating a lack of processing within the intergenic region separating these genes. We propose a cell cycle-dependent interference in transcript processing mediated by octamer consensus sequences as a mechanism contributing to the cycling of such transcripts.
Collapse
Affiliation(s)
- Nuraly K Avliyakulov
- Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, University of California-Los Angeles, 90095-1570, USA
| | | | | |
Collapse
|
49
|
Satish S, Bakre AA, Bhattacharya S, Bhattacharya A. Stress-dependent expression of a polymorphic, charged antigen in the protozoan parasite Entamoeba histolytica. Infect Immun 2003; 71:4472-86. [PMID: 12874327 PMCID: PMC166017 DOI: 10.1128/iai.71.8.4472-4486.2003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have identified a novel stress inducible gene, Ehssp1 in Entamoeba histolytica, the causative agent of amebiasis. Ehssp1 belongs to a polymorphic, multigene family and is present on multiple chromosomes. No homologue of this gene was found in the NCBI database. Sequence alignment of the multiple copies, and genomic PCR data restricted the polymorphism to the central region of the gene. This region contains a polypurine stretch that encodes a domain rich in acidic and basic amino acids. Under normal culture conditions only one copy of this multigene family is expressed, as observed by Northern blot and RT-PCR analysis. The size of this copy of the gene is 1,077 nucleotides, encoding a protein of 359 amino acids. The polymorphic domain in this copy is 64 nucleotides long. However, on exposure of cells to stress conditions such as heat shock or oxidative stress, multiple polymorphic copies of the gene are expressed, suggesting a possible role of this gene in adaptation of cells to stress conditions. The gene copy expressed under normal conditions, and the expression profile of cells under heat stress was identical in two different strains of E. histolytica tested. Interestingly, the extent of polymorphism in this gene was very less in E. dispar, a nonpathogenic sibling species of E. histolytica. Ehssp1 was found to be antigenic in invasive amebiasis patients.
Collapse
Affiliation(s)
- S Satish
- School of Life Sciences, Jawaharlal Nehru University, New Delhi-110067, India
| | | | | | | |
Collapse
|
50
|
Gull K. Host-parasite interactions and trypanosome morphogenesis: a flagellar pocketful of goodies. Curr Opin Microbiol 2003; 6:365-70. [PMID: 12941406 DOI: 10.1016/s1369-5274(03)00092-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Trypanosomes are characterised by the possession of a single flagellum and a subpellicular microtubule cytoskeleton. The flagellum is more than an organelle for motility; its position and polarity along with the sub-pellicular cytoskeleton enables the morphogenesis of a distinct flagellar pocket and the flagellar basal body is responsible for positioning and segregating the kinetoplast--the mitochondrial genome. Recent work has highlighted the molecules and morphogenesis of these cytoskeletal/flagellum structures and how dynamic events, occurring in the flagellar pocket and kinetoplast, are critical for host-parasite interactions.
Collapse
Affiliation(s)
- Keith Gull
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
| |
Collapse
|