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MacLean L, Myburgh E, Rodgers J, Price HP. Imaging African trypanosomes. Parasite Immunol 2014; 35:283-94. [PMID: 23790101 PMCID: PMC3992894 DOI: 10.1111/pim.12046] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 06/18/2013] [Indexed: 12/18/2022]
Abstract
Trypanosoma brucei are extracellular kinetoplastid parasites transmitted by the blood-sucking tsetse fly. They are responsible for the fatal disease human African trypanosomiasis (HAT), also known as sleeping sickness. In late-stage infection, trypanosomes cross the blood–brain barrier (BBB) and invade the central nervous system (CNS) invariably leading to coma and death if untreated. There is no available vaccine and current late-stage HAT chemotherapy consists of either melarsoprol, which is highly toxic causing up to 8% of deaths, or nifurtimox–eflornithine combination therapy (NECT), which is costly and difficult to administer. There is therefore an urgent need to identify new late-stage HAT drug candidates. Here, we review how current imaging tools, ranging from fluorescent confocal microscopy of live immobilized cells in culture to whole-animal imaging, are providing insight into T. brucei biology, parasite-host interplay, trypanosome CNS invasion and disease progression. We also consider how imaging tools can be used for candidate drug screening purposes that could lead to new chemotherapies.
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Affiliation(s)
- L MacLean
- Centre for Immunology and Infection, Department of Biology/Hull York Medical School, University of York, Heslington, York, UK.
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Myburgh E, Coles JA, Ritchie R, Kennedy PGE, McLatchie AP, Rodgers J, Taylor MC, Barrett MP, Brewer JM, Mottram JC. In vivo imaging of trypanosome-brain interactions and development of a rapid screening test for drugs against CNS stage trypanosomiasis. PLoS Negl Trop Dis 2013; 7:e2384. [PMID: 23991236 PMCID: PMC3749981 DOI: 10.1371/journal.pntd.0002384] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 07/13/2013] [Indexed: 11/18/2022] Open
Abstract
HUMAN AFRICAN TRYPANOSOMIASIS (HAT) MANIFESTS IN TWO STAGES OF DISEASE: firstly, haemolymphatic, and secondly, an encephalitic phase involving the central nervous system (CNS). New drugs to treat the second-stage disease are urgently needed, yet testing of novel drug candidates is a slow process because the established animal model relies on detecting parasitemia in the blood as late as 180 days after treatment. To expedite compound screening, we have modified the GVR35 strain of Trypanosoma brucei brucei to express luciferase, and have monitored parasite distribution in infected mice following treatment with trypanocidal compounds using serial, non-invasive, bioluminescence imaging. Parasites were detected in the brains of infected mice following treatment with diminazene, a drug which cures stage 1 but not stage 2 disease. Intravital multi-photon microscopy revealed that trypanosomes enter the brain meninges as early as day 5 post-infection but can be killed by diminazene, whereas those that cross the blood-brain barrier and enter the parenchyma by day 21 survived treatment and later caused bloodstream recrudescence. In contrast, all bioluminescent parasites were permanently eliminated by treatment with melarsoprol and DB829, compounds known to cure stage 2 disease. We show that this use of imaging reduces by two thirds the time taken to assess drug efficacy and provides a dual-modal imaging platform for monitoring trypanosome infection in different areas of the brain.
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Affiliation(s)
- Elmarie Myburgh
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Jonathan A. Coles
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Ryan Ritchie
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Peter G. E. Kennedy
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Alex P. McLatchie
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jean Rodgers
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Martin C. Taylor
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Michael P. Barrett
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- * E-mail:
| | - James M. Brewer
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Jeremy C. Mottram
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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Trans-sialidase from Trypanosoma brucei as a potential target for DNA vaccine development against African trypanosomiasis. Parasitol Res 2009; 105:1223-9. [PMID: 19582478 DOI: 10.1007/s00436-009-1542-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 06/15/2009] [Indexed: 01/16/2023]
Abstract
African trypanosomiasis (AT), also known as sleeping sickness in humans and Nagana in animals, is a disease caused by the protozoan parasite Trypanosoma brucei. AT is an extremely debilitating disease in human, cattle, and wild animals, and the treatment is difficult with frequent relapses. This work shows that BALB-c mice immunized intramuscularly with a single dose (100 microg) of a plasmid DNA encoding the 5'-terminal region of the trans-sialidase (nTSA) gene of T. brucei brucei are able to produce IgG antibodies that bind to the bloodstream form of T. brucei-protein extract and recognize the recombinant nTSA protein, expressed in Escherichia coli. Furthermore, this DNA vaccination process was able to protect 60% of mice submitted to a challenge assay with the infective form of T. brucei brucei parasites. These results demonstrate that a DNA vaccine coding for trans-sialidase from T. brucei is potentially useful in the prophylaxis of AT.
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Rodgers J, Bradley B, Kennedy PGE. Combination chemotherapy with a substance P receptor antagonist (aprepitant) and melarsoprol in a mouse model of human African trypanosomiasis. Parasitol Int 2007; 56:321-4. [PMID: 17643344 DOI: 10.1016/j.parint.2007.06.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2007] [Revised: 06/13/2007] [Accepted: 06/20/2007] [Indexed: 11/25/2022]
Abstract
Drug therapy for late-stage (encephalitic) human African trypanosomiasis (HAT) is currently very unsatisfactory with the most commonly used drug, melarsoprol, having a 5% overall mortality. There is evidence in a mouse model of HAT that Substance P (SP) receptor antagonism reduces the neuroinflammatory reaction to CNS trypanosome infection. In this study we investigated the effects of combination chemotherapy with melarsoprol and a humanised SP receptor antagonist aprepitant (EMEND) in this mouse model. The melarsoprol/aprepitant drug combination did not produce any clinical signs of illness in mice with CNS trypanosome infection. This lack of any additional or unexpected CNS toxicity in the mouse model of CNS HAT provides valuable safety data for the future possible use of this drug combination in patients with late-stage HAT.
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Affiliation(s)
- Jean Rodgers
- Division of Infection and Immunity, Faculty of Veterinary Medicine, Institute of Comparative Medicine, University of Glasgow Veterinary School, Glasgow, UK
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Human African trypanosomiasis: pharmacological re-engagement with a neglected disease. Br J Pharmacol 2007; 152:1155-71. [PMID: 17618313 DOI: 10.1038/sj.bjp.0707354] [Citation(s) in RCA: 221] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This review discusses the challenges of chemotherapy for human African trypanosomiasis (HAT). The few drugs registered for use against the disease are unsatisfactory for a number of reasons. HAT has two stages. In stage 1 the parasites proliferate in the haemolymphatic system. In stage 2 they invade the central nervous system and brain provoking progressive neurological dysfunction leading to symptoms that include the disrupted sleep wake patterns that give HAT its more common name of sleeping sickness. Targeting drugs to the central nervous system offers many challenges. However, it is the cost of drug development for diseases like HAT, that afflict exclusively people of the world's poorest populations, that has been the principal barrier to new drug development and has led to them becoming neglected. Here we review drugs currently registered for HAT, and also discuss the few compounds progressing through clinical trials. Finally we report on new initiatives that might allow progress to be made in developing new and satisfactory drugs for this terrible disease.
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Barrett MP, Gilbert IH. Targeting of toxic compounds to the trypanosome's interior. ADVANCES IN PARASITOLOGY 2006; 63:125-83. [PMID: 17134653 DOI: 10.1016/s0065-308x(06)63002-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Drugs can be targeted into African trypanosomes by exploiting carrier proteins at the surface of these parasites. This has been clearly demonstrated in the case of the melamine-based arsenical and the diamidine classes of drug that are already in use in the treatment of human African trypanosomiasis. These drugs can enter via an aminopurine transporter, termed P2, encoded by the TbAT1 gene. Other toxic compounds have also been designed to enter via this transporter. Some of these compounds enter almost exclusively through the P2 transporter, and hence loss of the P2 transporter leads to significant resistance to these particular compounds. It now appears, however, that some diamidines and melaminophenylarsenicals may also be taken up by other routes (of yet unknown function). These too may be exploited to target new drugs into trypanosomes. Additional purine nucleoside and nucleobase transporters have also been subverted to deliver toxic agents to trypanosomes. Glucose and amino acid transporters too have been investigated with a view to manipulating them to carry toxins into Trypanosoma brucei, and recent work has demonstrated that aquaglyceroporins may also have considerable potential for drug-targeting. Transporters, including those that carry lipids and vitamins such as folate and other pterins also deserve more attention in this regard. Some drugs, for example suramin, appear to enter via routes other than plasma-membrane-mediated transport. Receptor-mediated endocytosis has been proposed as a possible way in for suramin. Endocytosis also appears to be crucial in targeting natural trypanocides, such as trypanosome lytic factor (TLF) (apolipoprotein L1), into trypanosomes and this offers an alternative means of selectively targeting toxins to the trypanosome's interior. Other compounds may be induced to enter by increasing their capacity to diffuse over cell membranes; in this case depending exclusively on selective activity within the cell rather than selective uptake to impart selective toxicity. This review outlines studies that have aimed to exploit trypanosome nutrient uptake routes to selectively carry toxins into these parasites.
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Affiliation(s)
- Michael P Barrett
- Division of Infection & Immunity, Institute of Biomedical and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8QQ, UK
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Jennings FW, Rodgers J, Bradley B, Gettinby G, Kennedy PGE, Murray M. Human African trypanosomiasis: potential therapeutic benefits of an alternative suramin and melarsoprol regimen. Parasitol Int 2002; 51:381-8. [PMID: 12421636 DOI: 10.1016/s1383-5769(02)00044-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Treatment of late-stage human African trypanosomiasis is complicated by the presence of trypanosomes within the central nervous system (CNS). The regimen commonly prescribed to treat CNS-stage disease involves the use of the trypanocidal drugs suramin and melarsoprol. Suramin does not cross the blood-brain barrier efficiently and therefore, at normal dosages, will not cure CNS-stage infections. An initial treatment with suramin is given to eliminate the parasites from the peripheral tissues. This is followed by a course of intravenous melarsoprol, which can enter the CNS. However, melarsoprol not only produces severe adverse reactions but also is extremely painful to administer. One possible method to help alleviate these problems is to reduce the total amount of melarsoprol in the treatment regimen. This study indicates a synergism between suramin and melarsoprol and demonstrates that experimental murine CNS-trypanosomiasis can be cured with a single intraperitoneal dose of 20 mg/kg suramin followed almost immediately by 0.05 ml (4.5 micromol) topical melarsoprol. These dosages will not cure the infection when administered as monotherapies. Moreover, the timing of the drug administration appears to be crucial to the successful outcome of the regimen. If the interval between injection of suramin and application of topical melarsoprol is extended from 15 min to 3 or 7 days, the infections are not cured. Although extended relapse times occur following these regimens when compared with monotherapy approaches. Thus, there is strong evidence that injected suramin and topical melarsoprol should be given almost simultaneously to achieve the most effective combination of the two drugs.
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Affiliation(s)
- Frank W Jennings
- Department of Veterinary Clinical Studies, University of Glasgow Veterinary School, Bearsden Road, Glasgow G61 1QH, Scotland, UK
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Ogunbanwo JA, Agbonlahor DE, Adamu A, Dalyop P, Elesha SO, Fagbenro-Beyioku AF. Effects of anti-protozoal drugs and histopathological studies on trypanosome species. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2001; 30:73-83. [PMID: 11172994 DOI: 10.1111/j.1574-695x.2001.tb01552.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The trypanosomostatic and trypanosomicidal effects of four anti-protozoal drugs, namely halofantrine hydrochloride, chloroquine phosphate, benzoylmetronidazole and pyrimethamine, on species of trypanosomes, viz. Trypanosoma brucei brucei (MBOS/NG/94/NITR) Bassa strain, T. congolense (MBOS/NG/93/NVRI) Zaria strain and T. brucei gambiense (MHOM/NG/92/NITR) Abraka strain, were investigated. In vitro and in vivo studies on these drugs vis-a-vis the parasites were carried out. The histopathological changes in organs and tissues of experimentally infected rats were also studied. Results from the in vitro studies indicated that halofantrine hydrochloride, chloroquine phosphate, benzoylmetronidazole and pyrimethamine appeared to be effective trypanosomicidal agents against T. brucei brucei (Bassa strain), T. congolense (Zaria strain) and T. brucei gambiense (Abraka strain). The in vivo studies showed that these drugs were sub-curative by prolonging the survival period of the trypanosome-infected rats, but not necessarily curing the infection. Histopathological findings indicated inflammatory reactions characterised by infiltration to variable degrees in the majority of tissues, mostly in the lungs and liver. The most consistent lesions were interstitial pneumonia, multifocal necrosis and oedema. Pathological findings showed the T. brucei brucei and T. brucei gambiense strains studied to be both intravascular and extravascular parasites. These results suggest that halofantrine hydrochloride, chloroquine phosphate, benzoylmetronidazole and pyrimethamine could be used as supportive, suppressive and/or synergistic/additive drugs in the treatment of African trypanosomiasis. Their effects on species of trypanosomes have been studied and are reported for the first time.
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Affiliation(s)
- J A Ogunbanwo
- Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria.
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Abstract
This paper is a review of the current situation of the treatment of human African trypanosomiasis. The existing approved drugs are old, toxic and/or expensive. Therapeutic failures are common. Several factors may contribute to the problems of chemotherapy, including differences in the epidemiology of the disease, difficulties in the diagnosis and staging of the infection, availability, distribution and pharmacologic properties of drugs, standardization of treatment regimens, response to therapy, follow-up period, and relapses and clinical trials. The new therapeutic approaches include the development and approval of new drugs, the use of new therapeutic regimens, the study of drug combinations, and the development of new formulations.
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Affiliation(s)
- J Atouguia
- Centro de Malária e outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Lisboa, Portugal.
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Fernandes JH, Atouguia JM, Peleteiro MC, Jennings FW, Rosário VE. Post-treatment hind-leg paralysis in mice infected with Trypanosoma brucei brucei: a light microscopic study. Acta Trop 1997; 63:179-84. [PMID: 9088431 DOI: 10.1016/s0001-706x(96)00614-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- J H Fernandes
- Centro de Malária e outras Doencas Tropicias (CMDT), Lisbon, Portugal
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Jennings FW, Atouguia JM, Murray M. Topical chemotherapy for experimental murine African CNS-trypanosomiasis: the successful use of the arsenical, melarsoprol, combined with the 5-nitroimidazoles, fexinidazole or MK-436. Trop Med Int Health 1996; 1:590-8. [PMID: 8911443 DOI: 10.1111/j.1365-3156.1996.tb00084.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The 5-nitroimidazoles, MK-436 and fexinidazole dissolved in dimethylsulphoxide can be converted by the addition of hydroxypropylcellulose into gels which facilitates the ease and accuracy of administration. When these gels are used in combination with melarsoprol gel they are capable of curing experimental murine CNS-trypanosomiasis with a one-day treatment. The use of melarsoprol/MK-436 was more efficient than melarsoprol/fexinidazole gels. Thus while a single treatment with 0.1 ml 3.6% melarsoprol gel with 0.1 ml (14.3 mumol) fexinidazole gel cured the infected mice, the same dose of melarsoprol gel with 0.1 ml (4.0 mumol) of MK-436 gel was equally effective. It was also possible to prepare a combined melarsoprol/MK-436 gel which cured experimental CNS-trypanosomiasis with a single treatment. Topical treatment with this melarsoprol/MK-436 gel mixture also resolved clinically the hind leg paralysis which is associated with post-treatment reactive encephalopathy caused by non-curative treatment of CNS-trypanosomiasis.
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Affiliation(s)
- F W Jennings
- Department of Veterinary Parasitology, University of Glasgow, UK
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Jennings FW, Atouguia JM, Murray M. The importance of 2,3-dimercaptopropinol (British anti-lewisite, BAL) in the trypanocidal activity of topical melarsoprol. Acta Trop 1996; 62:83-9. [PMID: 8988309 DOI: 10.1016/s0001-706x(96)00036-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Both melarsomine dichlorhydrate (mel Cy, Cymelarsan) and melarsen oxide can be dissolved in dimethylsulfoxide and converted into a gel by the addition of hydroxypropylcellulose. When Trypanosoma brucei brucei-infected mice are treated topically with these gels the circulating trypanosomes are rapidly cleared from the circulation but the infections relapse soon after the last application. However, when these two compounds are allowed to react with 2,3-dimercaptopropinol (British anti-lewisite, BAL) and form "melarsoprol" their efficacy, especially in the case of mel Cy, is restored to that of commercial melarsoprol (Arsobal) and trypanosomes in the central nervous system (CNS) can be eliminated. This would indicate that the dimercaptopropinol portion of the molecule does not act solely as an "antidote" to arsenic toxicity, but also plays an important role in the absorption of melarsoprol through the skin and/or blood-brain barrier into the CNS and/or into the trypanosome.
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Affiliation(s)
- F W Jennings
- Department of Veterinary Parasitology, University of Glasgow, UK
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