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Steverding D, Caffrey CR. Should the enzyme name 'rhodesain' be discontinued? Mol Biochem Parasitol 2021; 245:111395. [PMID: 34246720 DOI: 10.1016/j.molbiopara.2021.111395] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 06/21/2021] [Accepted: 07/07/2021] [Indexed: 11/15/2022]
Abstract
Rhodesain is the generic name for the cathepsin L-like peptidase of Trypanosoma brucei rhodesiense. The term rhodesain was derived from the subspecies epithet rhodesiense which itself originated form Rhodesia, a historical region in southern Africa named after the 19th century British imperialist and white supremacist Cecil Rhodes. This tainting could be grounds for discontinuing the name, however, there are also scientific grounds. Specifically, protein sequence comparisons and frequency-based difference profiling reveal that rhodesain is essentially identical (99.87-98.44%) to the cathepsin L-like peptidases of both T. b. brucei and T. b. gambiense. Accordingly, and based on a previously proposed terminology for kinetoplastid C1 peptidases (Caffrey and Steverding, 2009), we suggest the use of the formal term, TbrCATL, to denote the cathepsin L-like peptidases of the T. brucei subspecies. The earlier and informal term, 'brucipain', could also be used.
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Affiliation(s)
- Dietmar Steverding
- Bob Champion Research and Education Centre, Norwich Medical School, University of East Anglia, Norwich, United Kingdom.
| | - Conor R Caffrey
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA
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Decolonising Parasitology: The Case of Trypanosoma brucei rhodesiense. Trends Parasitol 2021; 37:461-464. [PMID: 33858780 DOI: 10.1016/j.pt.2021.03.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 03/17/2021] [Accepted: 03/17/2021] [Indexed: 11/21/2022]
Abstract
Trypanosoma brucei rhodesiense was named after Rhodesia which, in turn, was named after the British imperialist and white supremacist Cecil Rhodes. In the light of the Black Lives Matter movement and contemporary consciousness of postcolonial legacy, it seems opportune to reconsider the subspecies name. Pros and cons of renaming T. b. rhodesiense are discussed.
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Masocha W, Kristensson K. Human African trypanosomiasis: How do the parasites enter and cause dysfunctions of the nervous system in murine models? Brain Res Bull 2018; 145:18-29. [PMID: 29870779 DOI: 10.1016/j.brainresbull.2018.05.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/24/2018] [Accepted: 05/30/2018] [Indexed: 12/27/2022]
Abstract
In this review we describe how Trypanosoma brucei brucei, a rodent pathogenic strain of African trypanosomes, can invade the nervous system, first by localization to the choroid plexus, the circumventricular organs (CVOs) and peripheral ganglia, which have fenestrated vessels, followed by crossing of the blood-brain barrier (BBB) into the white matter, hypothalamus, thalamus and basal ganglia. White blood cells (WBCs) pave the way for the trypanosome neuroinvasion. Experiments with immune deficient mice show that the invasion of WBCs is initiated by the toll-like receptor 9, followed by an augmentation phase that depends on the cytokine IFN-γ and the chemokine CXCL10. Nitric oxide (NO) derived from iNOS then prevents a break-down of the BBB and non-regulated passage of cells. This chain of events is relevant for design of better diagnostic tools to distinguish the different stages of the disease as well as for better understanding of the pathogenesis of the nervous system dysfunctions, which include circadian rhythm changes with sleep pattern disruption, pain syndromes, movement disorders and mental disturbances including dementia.
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Affiliation(s)
- Willias Masocha
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Kuwait University, Kuwait.
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A co-evolutionary arms race: trypanosomes shaping the human genome, humans shaping the trypanosome genome. Parasitology 2017; 142 Suppl 1:S108-19. [PMID: 25656360 PMCID: PMC4413828 DOI: 10.1017/s0031182014000602] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Trypanosoma brucei is the causative agent of African sleeping sickness in humans and one of several pathogens that cause the related veterinary disease Nagana. A complex co-evolution has occurred between these parasites and primates that led to the emergence of trypanosome-specific defences and counter-measures. The first line of defence in humans and several other catarrhine primates is the trypanolytic protein apolipoprotein-L1 (APOL1) found within two serum protein complexes, trypanosome lytic factor 1 and 2 (TLF-1 and TLF-2). Two sub-species of T. brucei have evolved specific mechanisms to overcome this innate resistance, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. In T. b. rhodesiense, the presence of the serum resistance associated (SRA) gene, a truncated variable surface glycoprotein (VSG), is sufficient to confer resistance to lysis. The resistance mechanism of T. b. gambiense is more complex, involving multiple components: reduction in binding affinity of a receptor for TLF, increased cysteine protease activity and the presence of the truncated VSG, T. b. gambiense-specific glycoprotein (TgsGP). In a striking example of co-evolution, evidence is emerging that primates are responding to challenge by T. b. gambiense and T. b. rhodesiense, with several populations of humans and primates displaying resistance to infection by these two sub-species.
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Genetic recombination between human and animal parasites creates novel strains of human pathogen. PLoS Negl Trop Dis 2015; 9:e0003665. [PMID: 25816228 PMCID: PMC4376878 DOI: 10.1371/journal.pntd.0003665] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 03/02/2015] [Indexed: 11/21/2022] Open
Abstract
Genetic recombination between pathogens derived from humans and livestock has the potential to create novel pathogen strains, highlighted by the influenza pandemic H1N1/09, which was derived from a re-assortment of swine, avian and human influenza A viruses. Here we investigated whether genetic recombination between subspecies of the protozoan parasite, Trypanosoma brucei, from humans and animals can generate new strains of human pathogen, T. b. rhodesiense (Tbr) responsible for sleeping sickness (Human African Trypanosomiasis, HAT) in East Africa. The trait of human infectivity in Tbr is conferred by a single gene, SRA, which is potentially transferable to the animal pathogen Tbb by sexual reproduction. We tracked the inheritance of SRA in crosses of Tbr and Tbb set up by co-transmitting genetically-engineered fluorescent parental trypanosome lines through tsetse flies. SRA was readily transferred into new genetic backgrounds by sexual reproduction between Tbr and Tbb, thus creating new strains of the human pathogen, Tbr. There was no evidence of diminished growth or transmissibility of hybrid trypanosomes carrying SRA. Although expression of SRA is critical to survival of Tbr in the human host, we show that the gene exists as a single copy in a representative collection of Tbr strains. SRA was found on one homologue of chromosome IV in the majority of Tbr isolates examined, but some Ugandan Tbr had SRA on both homologues. The mobility of SRA by genetic recombination readily explains the observed genetic variability of Tbr in East Africa. We conclude that new strains of the human pathogen Tbr are being generated continuously by recombination with the much larger pool of animal-infective trypanosomes. Such novel recombinants present a risk for future outbreaks of HAT. Genetic recombination allows transfer of harmful traits between different strains of the same pathogen and enables the emergence of genetically novel pathogen strains that the host population has not previously encountered. This can be particularly important when a pathogen acquires a virulence trait that allows it to spread beyond its normal host population. Here we show that this happens among the single-celled parasites—trypanosomes—that cause human African trypanosomiasis (HAT) or sleeping sickness carried by the tsetse fly. Genetic recombination readily occurs between the human and animal parasites when they are co-transmitted by the tsetse fly, creating new pathogen genotypes or strains. There is a single gene that confers human infectivity and each of the genotypes that inherits this gene is potentially capable of infecting humans. In this way new strains of the human pathogen can be generated by recombination between the human-infective and animal-infective trypanosomes. Such novel recombinants present a risk for future outbreaks of HAT.
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Sekhar GN, Watson CP, Fidanboylu M, Sanderson L, Thomas SA. Delivery of antihuman African trypanosomiasis drugs across the blood-brain and blood-CSF barriers. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 71:245-75. [PMID: 25307219 DOI: 10.1016/bs.apha.2014.06.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Human African trypanosomiasis (HAT or sleeping sickness) is a potentially fatal disease caused by the parasite, Trypanosoma brucei sp. The parasites are transmitted by the bite of insect vectors belonging to the genus Glossina (tsetse flies) and display a life cycle strategy that is equally spread between human and insect hosts. T.b. gambiense is found in western and central Africa whereas, T.b. rhodesiense is found in eastern and southern Africa. The disease has two clinical stages: a blood stage after the bite of an infected tsetse fly, followed by a central nervous system (CNS) stage where the parasite penetrates the brain; causing death if left untreated. The blood-brain barrier (BBB) makes the CNS stage difficult to treat because it prevents 98% of all known compounds from entering the brain, including some anti-HAT drugs. Those that do enter the brain are toxic compounds in their own right and have serious side effects. There are only a few drugs available to treat HAT and those that do are stage specific. This review summarizes the incidence, diagnosis, and treatment of HAT and provides a close examination of the BBB transport of anti-HAT drugs and an overview of the latest drugs in development.
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Affiliation(s)
- Gayathri N Sekhar
- King's College London, Institute of Pharmaceutical Sciences, London, United Kingdom
| | - Christopher P Watson
- King's College London, Institute of Pharmaceutical Sciences, London, United Kingdom
| | - Mehmet Fidanboylu
- King's College London, Institute of Pharmaceutical Sciences, London, United Kingdom
| | - Lisa Sanderson
- King's College London, Institute of Pharmaceutical Sciences, London, United Kingdom
| | - Sarah A Thomas
- King's College London, Institute of Pharmaceutical Sciences, London, United Kingdom.
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Tiberti N, Matovu E, Hainard A, Enyaru JC, Lejon V, Robin X, Turck N, Ngoyi DM, Krishna S, Bisser S, Courtioux B, Büscher P, Kristensson K, Ndung'u JM, Sanchez JC. New biomarkers for stage determination in Trypanosoma brucei rhodesiense sleeping sickness patients. Clin Transl Med 2013; 2:1. [PMID: 23369533 PMCID: PMC3561069 DOI: 10.1186/2001-1326-2-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 12/25/2012] [Indexed: 12/26/2022] Open
Abstract
Accurate stage determination is crucial in the choice of treatment for patients suffering from sleeping sickness, also known as human African trypanosomiasis (HAT). Current staging methods, based on the counting of white blood cells (WBC) and the detection of parasites in the cerebrospinal fluid (CSF) have limited accuracy. We hypothesized that immune mediators reliable for staging T. b. gambiense HAT could also be used to stratify T. b. rhodesiense patients, the less common form of HAT. A population comprising 85 T. b. rhodesiense patients, 14 stage 1 (S1) and 71 stage 2 (S2) enrolled in Malawi and Uganda, was investigated. The CSF levels of IgM, MMP-9, CXCL13, CXCL10, ICAM-1, VCAM-1, neopterin and B2MG were measured and their staging performances evaluated using receiver operating characteristic (ROC) analyses. IgM, MMP-9 and CXCL13 were the most accurate markers for stage determination (partial AUC 88%, 86% and 85%, respectively). The combination in panels of three molecules comprising CXCL13-CXCL10-MMP-9 or CXCL13-CXCL10-IgM significantly increased their staging ability to partial AUC 94% (p value < 0.01). The present study highlighted new potential markers for stage determination of T. b. rhodesiense patients. Further investigations are needed to better evaluate these molecules, alone or in panels, as alternatives to WBC to make reliable choice of treatment.
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Affiliation(s)
- Natalia Tiberti
- Department of Human Protein Sciences, University of Geneva, Geneva, Switzerland.
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Stephens NA, Kieft R, Macleod A, Hajduk SL. Trypanosome resistance to human innate immunity: targeting Achilles' heel. Trends Parasitol 2012; 28:539-45. [PMID: 23059119 DOI: 10.1016/j.pt.2012.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/14/2012] [Accepted: 09/15/2012] [Indexed: 10/27/2022]
Abstract
Trypanosome lytic factors (TLFs) are powerful, naturally occurring toxins in humans that provide sterile protection against infection by several African trypanosomes. These trypanocidal complexes predominantly enter the parasite by binding to the trypanosome haptoglobin/hemoglobin receptor (HpHbR), trafficking to the lysosome, causing membrane damage and, ultimately, cell lysis. Despite TLF-mediated immunity, the parasites that cause human African Trypanosomiasis (HAT), Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense, have developed independent mechanisms of resistance to TLF killing. In this review we describe the parasite defenses that allow trypanosome infections of humans and discuss how targeting these apparent strengths of the parasite may reveal their Achilles' heel, leading to new approaches in the treatment of HAT.
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Affiliation(s)
- Natalie A Stephens
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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Balmer O, Beadell JS, Gibson W, Caccone A. Phylogeography and taxonomy of Trypanosoma brucei. PLoS Negl Trop Dis 2011; 5:e961. [PMID: 21347445 PMCID: PMC3035665 DOI: 10.1371/journal.pntd.0000961] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 01/10/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Characterizing the evolutionary relationships and population structure of parasites can provide important insights into the epidemiology of human disease. METHODOLOGY/PRINCIPAL FINDINGS We examined 142 isolates of Trypanosoma brucei from all over sub-Saharan Africa using three distinct classes of genetic markers (kinetoplast CO1 sequence, nuclear SRA gene sequence, eight nuclear microsatellites) to clarify the evolutionary history of Trypanosoma brucei rhodesiense (Tbr) and T. b. gambiense (Tbg), the causative agents of human African trypanosomosis (sleeping sickness) in sub-Saharan Africa, and to examine the relationship between Tbr and the non-human infective parasite T. b. brucei (Tbb) in eastern and southern Africa. A Bayesian phylogeny and haplotype network based on CO1 sequences confirmed the taxonomic distinctness of Tbg group 1. Limited diversity combined with a wide geographical distribution suggested that this parasite has recently and rapidly colonized hosts across its current range. The more virulent Tbg group 2 exhibited diverse origins and was more closely allied with Tbb based on COI sequence and microsatellite genotypes. Four of five COI haplotypes obtained from Tbr were shared with isolates of Tbb, suggesting a close relationship between these taxa. Bayesian clustering of microsatellite genotypes confirmed this relationship and indicated that Tbr and Tbb isolates were often more closely related to each other than they were to other members of the same subspecies. Among isolates of Tbr for which data were available, we detected just two variants of the SRA gene responsible for human infectivity. These variants exhibited distinct geographical ranges, except in Tanzania, where both types co-occurred. Here, isolates possessing distinct SRA types were associated with identical COI haplotypes, but divergent microsatellite signatures. CONCLUSIONS/SIGNIFICANCE Our data provide strong evidence that Tbr is only a phenotypic variant of Tbb; while relevant from a medical perspective, Tbr is not a reproductively isolated taxon. The wide distribution of the SRA gene across diverse trypanosome genetic backgrounds suggests that a large amount of genetic diversity is potentially available with which human-infective trypanosomes may respond to selective forces such as those exerted by drugs.
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Affiliation(s)
- Oliver Balmer
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.
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Genovese G, Tonna SJ, Knob AU, Appel GB, Katz A, Bernhardy AJ, Needham AW, Lazarus R, Pollak MR. A risk allele for focal segmental glomerulosclerosis in African Americans is located within a region containing APOL1 and MYH9. Kidney Int 2010; 78:698-704. [PMID: 20668430 DOI: 10.1038/ki.2010.251] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genetic variation at the MYH9 locus is linked to the high incidence of focal segmental glomerulosclerosis (FSGS) and non-diabetic end-stage renal disease among African Americans. To further define risk alleles with FSGS we performed a genome-wide association analysis using more than one million single-nucleotide polymorphisms in 56 African-American and 61 European-American patients with biopsy-confirmed FSGS. Results were compared to 1641 European Americans and 1800 African Americans as unselected controls. While no association was observed in the cohort of European Americans, the case-control comparison of African Americans found variants within a 60 kb region of chromosome 22 containing part of the APOL1 and MYH9 genes associated with increased risk of FSGS. This region spans different linkage disequilibrium blocks, and variants associating with disease within this region are in linkage disequilibrium with variants which have shown signals of natural selection. APOL1 is a strong candidate for a gene that has undergone recent natural selection and is known to be involved in the infection by Trypanosoma brucei, a parasite common in Africa that has recently adapted to infect human hosts. Further studies will be required to establish which variants are causally related to kidney disease, what mutations caused the selective sweep, and to ultimately determine if these are the same.
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Affiliation(s)
- Giulio Genovese
- Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
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A spectrum of disease in human African trypanosomiasis: the host and parasite genetics of virulence. Parasitology 2010; 137:2007-15. [PMID: 20663245 DOI: 10.1017/s0031182010000946] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
For over 50 years it has been known that there are considerable differences in the severity and rate of progression of both Trypanosoma brucei rhodesiense and T. b. gambiense infection between individuals. Yet research into the factors, whether parasite or host, which control virulence in Human African trypanosomiasis is in its infancy. In this paper we review the clinical evidence for virulence variation and the epidemiological and experimental data that give clues as to the mechanisms involved. Evidence will be presented for both asymptomatic forms of T. b. gambiense infection and low virulence forms of T. b. rhodesiense infection in humans. While in both cases the mechanisms remain to be elucidated, the overall infection virulence phenotype is determined by both parasite and host genotype.
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Genovese G, Friedman DJ, Ross MD, Lecordier L, Uzureau P, Freedman BI, Bowden DW, Langefeld CD, Oleksyk TK, Uscinski Knob AL, Bernhardy AJ, Hicks PJ, Nelson GW, Vanhollebeke B, Winkler CA, Kopp JB, Pays E, Pollak MR. Association of trypanolytic ApoL1 variants with kidney disease in African Americans. Science 2010; 329:841-5. [PMID: 20647424 DOI: 10.1126/science.1193032] [Citation(s) in RCA: 1422] [Impact Index Per Article: 101.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
African Americans have higher rates of kidney disease than European Americans. Here, we show that, in African Americans, focal segmental glomerulosclerosis (FSGS) and hypertension-attributed end-stage kidney disease (H-ESKD) are associated with two independent sequence variants in the APOL1 gene on chromosome 22 {FSGS odds ratio = 10.5 [95% confidence interval (CI) 6.0 to 18.4]; H-ESKD odds ratio = 7.3 (95% CI 5.6 to 9.5)}. The two APOL1 variants are common in African chromosomes but absent from European chromosomes, and both reside within haplotypes that harbor signatures of positive selection. ApoL1 (apolipoprotein L-1) is a serum factor that lyses trypanosomes. In vitro assays revealed that only the kidney disease-associated ApoL1 variants lysed Trypanosoma brucei rhodesiense. We speculate that evolution of a critical survival factor in Africa may have contributed to the high rates of renal disease in African Americans.
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Affiliation(s)
- Giulio Genovese
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA
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Llewellyn MS, Miles MA, Carrasco HJ, Lewis MD, Yeo M, Vargas J, Torrico F, Diosque P, Valente V, Valente SA, Gaunt MW. Genome-scale multilocus microsatellite typing of Trypanosoma cruzi discrete typing unit I reveals phylogeographic structure and specific genotypes linked to human infection. PLoS Pathog 2009; 5:e1000410. [PMID: 19412340 PMCID: PMC2669174 DOI: 10.1371/journal.ppat.1000410] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 04/01/2009] [Indexed: 11/28/2022] Open
Abstract
Trypanosoma cruzi is the most important parasitic infection in Latin America and is also genetically highly diverse, with at least six discrete typing units (DTUs) reported: Tc I, IIa, IIb, IIc, IId, and IIe. However, the current six-genotype classification is likely to be a poor reflection of the total genetic diversity present in this undeniably ancient parasite. To determine whether epidemiologically important information is "hidden" at the sub-DTU level, we developed a 48-marker panel of polymorphic microsatellite loci to investigate population structure among 135 samples from across the geographic distribution of TcI. This DTU is the major cause of resurgent human disease in northern South America but also occurs in silvatic triatomine vectors and mammalian reservoir hosts throughout the continent. Based on a total dataset of 12,329 alleles, we demonstrate that silvatic TcI populations are extraordinarily genetically diverse, show spatial structuring on a continental scale, and have undergone recent biogeographic expansion into the southern United States of America. Conversely, the majority of human strains sampled are restricted to two distinct groups characterised by a considerable reduction in genetic diversity with respect to isolates from silvatic sources. In Venezuela, most human isolates showed little identity with known local silvatic strains, despite frequent invasion of the domestic setting by infected adult vectors. Multilocus linkage indices indicate predominantly clonal parasite propagation among all populations. However, excess homozygosity among silvatic strains and raised heterozygosity among domestic populations suggest that some level of genetic recombination cannot be ruled out. The epidemiological significance of these findings is discussed.
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Widener J, Nielsen MJ, Shiflett A, Moestrup SK, Hajduk S. Hemoglobin is a co-factor of human trypanosome lytic factor. PLoS Pathog 2007; 3:1250-61. [PMID: 17845074 PMCID: PMC1971115 DOI: 10.1371/journal.ppat.0030129] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Accepted: 07/18/2007] [Indexed: 11/18/2022] Open
Abstract
Trypanosome lytic factor (TLF) is a high-density lipoprotein (HDL) subclass providing innate protection to humans against infection by the protozoan parasite Trypanosoma brucei brucei. Two primate-specific plasma proteins, haptoglobin-related protein (Hpr) and apolipoprotein L-1 (ApoL-1), have been proposed to kill T. b. brucei both singularly or when co-assembled into the same HDL. To better understand the mechanism of T. b. brucei killing by TLF, the protein composition of TLF was investigated using a gentle immunoaffinity purification technique that avoids the loss of weakly associated proteins. HDL particles recovered by immunoaffinity absorption, with either anti-Hpr or anti-ApoL-1, were identical in protein composition and specific activity for T. b. brucei killing. Here, we show that TLF-bound Hpr strongly binds Hb and that addition of Hb stimulates TLF killing of T. b. brucei by increasing the affinity of TLF for its receptor, and by inducing Fenton chemistry within the trypanosome lysosome. These findings suggest that TLF in uninfected humans may be inactive against T. b. brucei prior to initiation of infection. We propose that infection of humans by T. b. brucei causes hemolysis that triggers the activation of TLF by the formation of Hpr-Hb complexes, leading to enhanced binding, trypanolytic activity, and clearance of parasites.
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Affiliation(s)
- Justin Widener
- Program in Pathobiology, Brown University, Providence, Rhode Island, United States of America
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | | | - April Shiflett
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | | | - Stephen Hajduk
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
- * To whom correspondence should be addressed. E-mail:
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Gibson W. Resolution of the species problem in African trypanosomes. Int J Parasitol 2007; 37:829-38. [PMID: 17451719 DOI: 10.1016/j.ijpara.2007.03.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 02/19/2007] [Accepted: 03/01/2007] [Indexed: 12/29/2022]
Abstract
There is a general assumption that eukaryote species are demarcated by morphological or genetic discontinuities. This stems from the idea that species are defined by the ability of individuals to mate and produce viable progeny. At the microscopic level, where organisms often proliferate more by asexual than sexual reproduction, this tidy classification system breaks down and species definition becomes messy and problematic. The dearth of morphological characters to distinguish microbial species has led to the widespread application of molecular methods for identification. As well as providing molecular markers for species identification, gene sequencing has generated the data for accurate estimation of relatedness between different populations of microbes. This has led to recognition of conflicts between current taxonomic designations and phylogenetic placement. In the case of microbial pathogens, the extent to which taxonomy has been driven by utilitarian rather than biological considerations has been made explicit by molecular phylogenetic analysis. These issues are discussed with reference to the taxonomy of the African trypanosomes, where pathogenicity, host range and distribution have been influential in the designation of species and subspecies. Effectively, the taxonomic units recognised are those that are meaningful in terms of human or animal disease. The underlying genetic differences separating the currently recognised trypanosome taxa are not consistent, ranging from genome-wide divergence to presence/absence of a single gene. Nevertheless, if even a minor genetic difference reflects adaptation to a particular parasitic niche, for example, in Trypanosoma brucei rhodesiense, the presence of a single gene conferring the ability to infect humans, then it can prove useful as an identification tag for the taxon occupying that niche. Thus, the species problem can be resolved by bringing together considerations of utility, genetic difference and adaptation.
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Affiliation(s)
- W Gibson
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
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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.
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Affiliation(s)
- Sara D Faulkner
- Josephine Bay Paul Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA
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17
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Gibson W, Peacock L, Ferris V, Williams K, Bailey M. Analysis of a cross between green and red fluorescent trypanosomes. Biochem Soc Trans 2006; 34:557-9. [PMID: 16856859 DOI: 10.1042/bst0340557] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Trypanosoma brucei undergoes genetic exchange in its insect vector, but the mechanism is unknown and no one has yet seen the process. By crossing genetically engineered red and green fluorescent trypanosomes, we have been able to pinpoint the location of genetic exchange in the fly and search for intermediate stages. In experimental crosses of red and green parental trypanosomes, yellow hybrid trypanosomes first appeared in the fly salivary glands as early as 13 days after infection and were observed only in flies with a mixture of red and green trypanosomes in one or both salivary glands. Despite high numbers of flies with mixed infections, yellow trypanosomes were not detected in the fly midgut or proventriculus. The hybrid nature of yellow trypanosomes was confirmed by analysis of molecular karyotypes and microsatellite alleles. As well as yellow hybrids, hybrid trypanosomes with red, green or no fluorescence were also recovered from fly salivary glands. Analysis of microsatellite alleles in parental and progeny clones showed Mendelian inheritance. Our findings are consistent with the hypothesis that mating takes place between trypanosomes in the salivary glands of the fly before they attach to the salivary gland epithelium.
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Affiliation(s)
- W Gibson
- School of Biological Sciences, University of Bristol, Bristol BS81UG, UK.
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18
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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.
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Affiliation(s)
- J M Sternberg
- Zoology Building, School of Biological Sciences, University of Aberdeen, UK.
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19
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MacLean L, Chisi JE, Odiit M, Gibson WC, Ferris V, Picozzi K, Sternberg JM. Severity of human african trypanosomiasis in East Africa is associated with geographic location, parasite genotype, and host inflammatory cytokine response profile. Infect Immun 2004; 72:7040-4. [PMID: 15557627 PMCID: PMC529158 DOI: 10.1128/iai.72.12.7040-7044.2004] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanisms underlying virulence in human African trypanosomiasis are poorly understood, although studies with experimental mice suggest that unregulated host inflammatory responses are associated with disease severity. We identified two trypanosomiasis foci with dramatically different disease virulence profiles. In Uganda, infections followed an acute profile with rapid progression to the late stage (meningoencephalitic infection) in the majority of patients (86.8%). In contrast, infections in Malawi were of a chronic nature, in which few patients progressed to the late stage (7.1%), despite infections of several months' duration. All infections were confirmed to be Trypanosoma brucei rhodesiense by testing for the presence of the serum resistance-associated (SRA) gene, but trypanosomes isolated from patients in Uganda or Malawi were distinguished by an SRA gene polymorphism. The two disease profiles were associated with markedly different levels of tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) in plasma. In Uganda but not Malawi early-stage TNF-alpha was elevated, while in Malawi but not Uganda early-stage TGF-beta was elevated. Thus, rapid disease progression in Uganda is associated with TNF-alpha-mediated inflammatory pathology, whereas in the milder disease observed in Malawi this may be ameliorated by counterinflammatory cytokines. These differing host responses may result either from differing virulence phenotypes of northern and southern trypanosomes or from immune response polymorphisms in the different host populations.
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Affiliation(s)
- Lorna MacLean
- School of Biological Sciences, University of Aberdeen, Zoology Building, Aberdeen AB24 2TZ, Scotland, United Kingdom
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20
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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.
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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
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21
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Jamonneau V, Solano P, Koffi M, Denizot M, Cuny G. [Contributions and limits of the diagnosis of human African trypanosomiasis]. Med Sci (Paris) 2004; 20:871-5. [PMID: 15461963 DOI: 10.1051/medsci/20042010871] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Human African trypanosomiasis, or sleeping sickness, is still a worrying problem in Africa. Sleeping sickness is a disease for which a systematic monitoring is necessary, particularly for the trypanosomiasis caused by Trypanosoma brucei gambiense, which is characterized by a long asymptomatic stage. In the absence of specific clinical signs, mass screening of populations remains the only way to control the disease and to avoid its spreading. The lack of sensitivity and specificity of the diagnosis tests classically used led to the development of molecular tools. PCR amplification of parasite specific sequences has considerably improved the diagnostic of the parasitic infection, the stage diagnosis as well as the post-therapeutic follow-up. But there are limits with a use in routine and research is still necessary to make PCR a real tool for control of sleeping sickness.
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Affiliation(s)
- Vincent Jamonneau
- Institut de recherche pour le développement (IRD), UR 035, Laboratoire de recherche et de coordination sur les trypanosomiases (LRCT), IRD/CIRAD, Campus international de Baillarguet, TA 207G, 34398 Montpellier 5, France.
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22
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Gibson W. Species concepts for trypanosomes: from morphological to molecular definitions? KINETOPLASTID BIOLOGY AND DISEASE 2003; 2:10. [PMID: 14613500 PMCID: PMC280663 DOI: 10.1186/1475-9292-2-10] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/13/2003] [Accepted: 10/28/2003] [Indexed: 11/10/2022]
Abstract
The way species and subspecies names are applied in African trypanosomes of subgenera Trypanozoon and Nannomonas is reviewed in the light of data from molecular taxonomy. In subgenus Trypanozoon the taxonomic importance of pathogenicity, host range and distribution appear to have been inflated relative to actual levels of genetic divergence. The opposite is true for subgenus Nannomonas, where current taxonomic usage badly underrepresents genetic diversity. Data from molecular characterisation studies are revealing a growing number of genotypes, which may represent distinct taxa. Unfortunately few of these genotypes are yet supported by sufficient biological data to be recognized taxonomically. But we may be missing fundamental epidemiological information, because of our inability to distinguish these trypanosomes in host blood morphologically or in tsetse by their developmental cycle. Molecular taxonomy has led the way in identifying these new genotypes and now offers the key to elucidating the biology of these organisms.
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Affiliation(s)
- Wendy Gibson
- School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK.
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23
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Gibson W, Ferris V. Conservation of the genomic location of the human serum resistance associated gene in Trypanosoma brucei rhodesiense. Mol Biochem Parasitol 2003; 130:159-62. [PMID: 12946855 DOI: 10.1016/s0166-6851(03)00168-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Wendy Gibson
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
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24
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Wang J, Böhme U, Cross GAM. Structural features affecting variant surface glycoprotein expression in Trypanosoma brucei. Mol Biochem Parasitol 2003; 128:135-45. [PMID: 12742580 DOI: 10.1016/s0166-6851(03)00055-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The glycosylphosphatidylinositol (GPI)-anchored variant surface glycoprotein (VSG) of Trypanosoma brucei is the most abundant GPI-anchored protein expressed on any cell, and is an essential virulence factor. To determine what structural features affect efficient expression of VSG, we made a series of mutations in two VSGs. Inserting 18 amino acids, between the amino- and carboxy-terminal domains, reduced the expression of VSG 221 to about 3% of the wild-type level. When this insertion was combined with deletion of the single carboxy-terminal subdomain, expression was reduced a further three-fold. In VSG 117, which contains two carboxy-terminal subdomains, point mutation of the intervening N-glycosylation site reduced expression about 15-fold. Deleting the most carboxy-terminal subdomain and intervening region, including the N-glycosylation site, reduced expression to 15-20% of wild type VSG, and deletion of both subdomains reduced expression to <1%. Despite their low abundance, all VSG mutants were GPI anchored on the cell surface. Our results suggest that, for a protein to be efficiently displayed on the surface of bloodstream-form T. brucei, it is essential that it contains the conserved structural motifs of a T. brucei VSG. Serum resistance-associated protein (SRA), which confers human infectivity on T. brucei, strongly resembles a VSG deletion mutant. Expression of three epitope-tagged versions of SRA in T. brucei conferred total resistance to human serum. SRA possesses a canonical GPI signal sequence, but we were unable to obtain unequivocal evidence for the presence of a GPI anchor. SRA was not released during osmotic lysis, indicating that it is not GPI anchored on the cell surface.
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Affiliation(s)
- Jun Wang
- Laboratory of Molecular Parasitology, The Rockefeller University, Box 185, 1230 York Avenue, New York, NY 10021-6399, USA
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