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Emodepside targets SLO-1 channels of Onchocerca ochengi and induces broad anthelmintic effects in a bovine model of onchocerciasis. PLoS Pathog 2021; 17:e1009601. [PMID: 34077488 PMCID: PMC8202924 DOI: 10.1371/journal.ppat.1009601] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 06/14/2021] [Accepted: 05/01/2021] [Indexed: 12/14/2022] Open
Abstract
Onchocerciasis (river blindness), caused by the filarial worm Onchocerca volvulus, is a neglected tropical disease mostly affecting sub-Saharan Africa and is responsible for >1.3 million years lived with disability. Current control relies almost entirely on ivermectin, which suppresses symptoms caused by the first-stage larvae (microfilariae) but does not kill the long-lived adults. Here, we evaluated emodepside, a semi-synthetic cyclooctadepsipeptide registered for deworming applications in companion animals, for activity against adult filariae (i.e., as a macrofilaricide). We demonstrate the equivalence of emodepside activity on SLO-1 potassium channels in Onchocerca volvulus and Onchocerca ochengi, its sister species from cattle. Evaluation of emodepside in cattle as single or 7-day treatments at two doses (0.15 and 0.75 mg/kg) revealed rapid activity against microfilariae, prolonged suppression of female worm fecundity, and macrofilaricidal effects by 18 months post treatment. The drug was well tolerated, causing only transiently increased blood glucose. Female adult worms were mostly paralyzed; however, some retained metabolic activity even in the multiple high-dose group. These data support ongoing clinical development of emodepside to treat river blindness.
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Cho-Ngwa F, Mbah GE, Ayiseh RB, Ndi EM, Monya E, Tumanjong IM, Mainsah EN, Sakanari J, Lustigman S. Development and validation of an Onchocerca ochengi adult male worm gerbil model for macrofilaricidal drug screening. PLoS Negl Trop Dis 2019; 13:e0007556. [PMID: 31260456 PMCID: PMC6625737 DOI: 10.1371/journal.pntd.0007556] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 07/12/2019] [Accepted: 06/18/2019] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Onchocerciasis currently afflicts an estimated 15 million people and is the second leading infectious cause of blindness world-wide. The development of a macrofilaricide to cure the disease has been hindered by the lack of appropriate small laboratory animal models. This study therefore, was aimed at developing and validating the Mongolian gerbil, as an Onchocerca ochengi (the closest in phylogeny to O. volvulus) adult male worm model. METHODOLOGY/PRINCIPAL FINDINGS Mongolian gerbils (Meriones unguiculatus) were each implanted with 20 O. ochengi male worms (collected from infected cattle), in the peritoneum. Following drug or placebo treatments, the implanted worms were recovered from the animals and analyzed for burden, motility and viability. Worm recovery in control gerbils was on average 35%, with 89% of the worms being 100% motile. Treatment of the gerbils implanted with male worms with flubendazole (FBZ) resulted in a significant reduction (p = 0.0021) in worm burden (6.0% versus 27.8% in the control animals); all recovered worms from the treated group had 0% worm motility versus 91.1% motility in control animals. FBZ treatment had similar results even after four different experiments. Using this model, we tested a related drug, oxfendazole (OFZ), and found it to also significantly (p = 0.0097) affect worm motility (22.7% versus 95.0% in the control group). CONCLUSIONS/SIGNIFICANCE We have developed and validated a novel gerbil O. ochengi adult male worm model for testing new macrofilaricidal drugs in vivo. It was also used to determine the efficacy of oxfendazole in vivo.
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Affiliation(s)
- Fidelis Cho-Ngwa
- ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Glory Enjong Mbah
- ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Rene Bilingwe Ayiseh
- ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Emmanuel Menang Ndi
- ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Elvis Monya
- ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Irene Memeh Tumanjong
- ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Evans Ngandung Mainsah
- ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Judy Sakanari
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America
| | - Sara Lustigman
- Lindsley F. Kimball Research Institute, New York City, New York, United States of America
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Voronin D, Tricoche N, Jawahar S, Shlossman M, Bulman CA, Fischer C, Suderman MT, Sakanari JA, Lustigman S. Development of a preliminary in vitro drug screening assay based on a newly established culturing system for pre-adult fifth-stage Onchocerca volvulus worms. PLoS Negl Trop Dis 2019; 13:e0007108. [PMID: 30653499 PMCID: PMC6353222 DOI: 10.1371/journal.pntd.0007108] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 01/30/2019] [Accepted: 12/22/2018] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND The human filarial parasite Onchocerca volvulus is the causative agent of onchocerciasis (river blindness). It causes blindness in 270,000 individuals with an additional 6.5 million suffering from severe skin pathologies. Current international control programs focus on the reduction of microfilaridermia by annually administering ivermectin for more than 20 years with the ultimate goal of blocking of transmission. The adult worms of O. volvulus can live within nodules for over 15 years and actively release microfilariae for the majority of their lifespan. Therefore, protracted treatment courses of ivermectin are required to block transmission and eventually eliminate the disease. To shorten the time to elimination of this disease, drugs that successfully target macrofilariae (adult parasites) are needed. Unfortunately, there is no small animal model for the infection that could be used for discovery and screening of drugs against adult O. volvulus parasites. Here, we present an in vitro culturing system that supports the growth and development of O. volvulus young adult worms from the third-stage (L3) infective stage. METHODOLOGY/PRINCIPAL FINDINGS In this study we optimized the culturing system by testing several monolayer cell lines to support worm growth and development. We have shown that the optimized culturing system allows for the growth of the L3 worms to L5 and that the L5 mature into young adult worms. Moreover, these young O. volvulus worms were used in preliminary assays to test putative macrofilaricidal drugs and FDA-approved repurposed drugs. CONCLUSION The culture system we have established for O. volvulus young adult worms offers a promising new platform to advance drug discovery against the human filarial parasite, O. volvulus and thus supports the continuous pursuit for effective macrofilaricidal drugs. However, this in vitro culturing system will have to be further validated for reproducibility before it can be rolled out as a drug screen for decision making in macrofilaricide drug development programs.
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Affiliation(s)
- Denis Voronin
- Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
- * E-mail:
| | - Nancy Tricoche
- Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
| | - Shabnam Jawahar
- Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
| | - Michael Shlossman
- Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
| | - Christina A. Bulman
- Dept. of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Chelsea Fischer
- Dept. of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | | | - Judy A. Sakanari
- Dept. of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Sara Lustigman
- Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
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Fombad FF, Njouendou AJ, Ndongmo PC, Ritter M, Chunda VC, Metuge HM, Gandjui NVT, Enyong P, Njiokou F, Hoerauf A, Mackenzie CD, Wanji S. Effect of flubendazole on developing stages of Loa loa in vitro and in vivo: a new approach for screening filaricidal agents. Parasit Vectors 2019; 12:14. [PMID: 30621774 PMCID: PMC6323797 DOI: 10.1186/s13071-018-3282-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 12/27/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Loiasis, an often-neglected tropical disease, is a threat to the success of lymphatic filariasis and onchocerciasis elimination programmes in rainforest areas of the central and western Africa. Its control and even its elimination might be possible through the use of a safe macrofilaricide, a prophylactic drug, or perhaps a vaccine. This present study evaluated the effect of flubendazole (FLBZ) on the development of Loa loa L3 in vitro and in vivo. METHODS Infective stages of L. loa were isolated and co-cultured in Dulbecco's Modified Eagle's Medium in the presence of monkey kidney epithelial cells (LLC-MK2) feeder cells. FLBZ and its principal metabolites, reduced flubendazole (RFLBZ) and hydrolyzed flubendazole (HFLBZ), were screened in vitro at concentrations 0.05, 0.1, 0.5, 1 and 10 μg/ml. The viability of the parasites was assessed microscopically daily for 15 days. For in vivo study, a total of 48 CcR3 KO mice were infected subcutaneously with 200 L. loa L3 and treated with 10 mg/kg FLBZ once daily for 5 consecutive days. Twenty-four animals were used as control and received L3 and vehicle. They were dissected at 5, 10, 15 and 20 days post-treatment for worm recovery. RESULTS The motility of L3 larvae in vitro was reduced from the second day of incubation with drugs at in vivo plasma concentration levels, with a strong correlation found between reduced motility and increased drug concentration (Spearman's rho = -0.9, P < 0.0001). Except for HFLBZ (0.05 μg/ml and 0.01 μg/ml), all concentrations of FLBZ, HFLBZ and RFLBZ interrupted the moulting of L. loa infective larvae to L4. In vivo, regardless of the experimental group, there was a decrease in parasite recovery with time. However, at each time point this reduction was more pronounced in the group of animals treated with FLBZ compared to equivalent control. Parasites were recovered from the flubendazole-treated groups only on day 5 post-inoculation at an average rate of 2.1%, a value significantly lower (Mann-Whitney U-test, U = 28, P = 0.0156) than the average of 31.1% recovered from the control group. CONCLUSIONS This study reveals the ability of flubendazole to inhibit the development of L. loa L3 both in vitro and in vivo, and in addition validates the importance of in vitro and animal models of L. loa as tools for the development of drugs against loiasis.
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Affiliation(s)
- Fanny Fri Fombad
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon.,Department of Zoology and Animal Physiology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Abdel Jelil Njouendou
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon.,Department of Biomedical Science, Faculty of Health Science, University of Buea, Buea, Cameroon
| | - Patrick Chounna Ndongmo
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Manuel Ritter
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | - Valerine C Chunda
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Haelly M Metuge
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Narcisse Victor T Gandjui
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Peter Enyong
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Flobert Njiokou
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaounde I, Yaounde, Cameroon
| | - Achim Hoerauf
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany.,German Centre for Infection Research (DZIF), Bonn-Cologne partner site, Bonn, Germany
| | - Charles D Mackenzie
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, MI, 48824, USA.,Filariasis Programmes Support Unit, Liverpool School of Tropical Medicine, Pembroke Place, L3 5QA, Liverpool, UK
| | - Samuel Wanji
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon.
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Njouendou AJ, Fombad FF, O'Neill M, Zofou D, Nutting C, Ndongmo PC, Kengne-Ouafo AJ, Geary TG, Mackenzie CD, Wanji S. Heterogeneity in the in vitro susceptibility of Loa loa microfilariae to drugs commonly used in parasitological infections. Parasit Vectors 2018; 11:223. [PMID: 29615094 PMCID: PMC5883330 DOI: 10.1186/s13071-018-2799-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 03/15/2018] [Indexed: 01/10/2023] Open
Abstract
Background Co-infection with loiasis remains a potential problem in control programs targeting filarial infections. The effects of many anti-parasitic drugs often administered to Loa loa infected people are not well documented. This study compared the in vitro activity of several of these drugs on the viability of L. loa microfilariae (mf). Methods Human strain L. loa mf were isolated from baboon blood using iso-osmotic Percoll gradient, and cultured in RPMI 1640/10% FBS with antimalarial drugs (mefloquine, amodiaquine, artesunate, chloroquine and quinine), anthelmintics (ivermectin, praziquantel, flubendazole and its reduced and hydrolyzed metabolites), two potential trypanocidal agents (fexinidazole and Scynexis-7158) and the anticancer drug imatinib. The drug concentrations used varied between 0.156 μg/ml and 10 μg/ml. Mf motility (CR50 = 50% immotility) and a metabolic viability assay (MTT) were used to assess the effects of these drugs on the parasites. Results Mf in control cultures showed only a slight reduction in motility after 5 days of culture. Active inhibition of Loa loa motility was seen with mefloquine and amodiaquine (CR50 values of 3.87 and 4.05 μg/ml, respectively), immobilizing > 90% mf within the first 24 hours: mefloquine killed the mf after 24 hours of culture at concentrations ≥ 5 μg/ml. SCYX-7158 also induced a concentration-dependent reduction in mf motility, with > 50% reduction in mf motility seen after 5 days at 10 μg/ml. The anticancer drug imatinib reduced mf motility at 10 μg/ml from the first day of incubation to 55% by day 5, and the reduction in motility was concentration-dependent. Praziquantel and fexinidazole were inactive, and FLBZ and its metabolites, as well as ivermectin at concentrations > 5 μg/ml, had very minimal effects on mf motility over the first 4 days of culture. Conclusions The considerable action of the anti-malarial drugs mefloquine and amodiaquine on Loa mf in vitro highlights the possibility of repurposing the existing anti-infectious agents for the development of drugs against loiasis. The heterogeneity in the activity of anti-parasitic agents on Loa loa mf supports the need for further investigation using animal models of loiasis. Electronic supplementary material The online version of this article (10.1186/s13071-018-2799-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Abdel J Njouendou
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Fanny F Fombad
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Maeghan O'Neill
- Institute of Parasitology, McGill University, Ste-Anne-de-Bellevue, QC, H9X 3V9, Canada
| | - Denis Zofou
- Biotechnology unit, Department of Biochemistry and Molecular Biology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Chuck Nutting
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, 49008, USA
| | - Patrick C Ndongmo
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Arnaud J Kengne-Ouafo
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon
| | - Timothy G Geary
- Institute of Parasitology, McGill University, Ste-Anne-de-Bellevue, QC, H9X 3V9, Canada
| | - Charles D Mackenzie
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, MI, 48824, USA.,Filariasis Programmes Support Unit, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Samuel Wanji
- Parasites and Vectors Biology Research Unit (PAVBRU), Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Buea, Cameroon.
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25 Years of the Onchocerca ochengi Model. Trends Parasitol 2016; 32:966-978. [PMID: 27665524 DOI: 10.1016/j.pt.2016.08.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 08/20/2016] [Accepted: 08/30/2016] [Indexed: 01/12/2023]
Abstract
Although of limited veterinary significance, Onchocerca ochengi has become famous as a natural model or 'analogue' of human onchocerciasis (river blindness), which is caused by Onchocerca volvulus. On the basis of both morphological and molecular criteria, O. ochengi is the closest extant relative of O. volvulus and shares several key natural history traits with the human pathogen. These include exploitation of the same group of insect vectors (blackflies of the Simulium damnosum complex) and formation of collagenous nodules with a similar histological structure to human nodules. Here, we review the contribution of this natural system to drug and vaccine discovery efforts, as well as to our basic biological understanding of Onchocerca spp., over the past quarter-century.
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Mbah GE, Ayiseh RB, Cho-Ngwa F. Development and validation of an Onchocerca ochengi microfilarial hamster model for onchocerciasis drug screens. BMC Infect Dis 2016; 16:404. [PMID: 27515037 PMCID: PMC4982420 DOI: 10.1186/s12879-016-1753-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 08/04/2016] [Indexed: 12/02/2022] Open
Abstract
Background Onchocerciasis, caused by the parasitic nematode, Onchocerca volvulus afflicts some 37 million people worldwide, and is the second leading infectious cause of blindness globally. The only currently recommended drug for treatment of the disease, ivermectin, is only microfilaricidal and has serious adverse effects in individuals co-infected with high loads of Loa loa microfilariae (mf), prompting the search for new and better drugs. Onchocerciasis drug discovery studies have so far been based on in vivo models using Onchocerca species which are not the closest to O. volvulus, and which may therefore, not adequately mimic the natural infection in humans. Therefore, this study was carried out to develop a better drug screening model for onchocerciasis, based on the use of cow-derived O. ochengi, the closest known relative of O. volvulus. Methods Mf of O. ochengi were injected subcutaneously at the nape of Syrian hamsters (Mesocricetus auratus) and BALB/c mice. The skin, and especially the earlobes of the animals were examined for mf 15–31 days after infection. For selected model validation, the hamsters were treated with ivermectin at 150 or 600 μg/kg body weight and examined 30 days after infection for mf. For L. loa studies in hamsters, isolated mf were injected intraperitoneally and animal organs were examined on day 26 for mf. Results The Syrian hamsters were found to be the more permissive to O. ochengi mf as fully viable mf were recovered from them on day 30, compared to BALB/c mice where such mf were recovered on day 15, but not 30. However, both animals were not permissive to L. loa mf even by day 15. Interestingly, more than 50 % of the total O. ochengi mf recovered were from the earlobes. The number of mf injected was directly proportional to the number recovered. Ivermectin at both concentrations tested completely eliminated the O. ochengi mf from the hamsters. Conclusion This study reveals the Syrian hamster as an appropriate small animal model for screening of novel compounds against O. ochengi, the closest known relative of O. volvulus.
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Affiliation(s)
- Glory Enjong Mbah
- Department of Biochemistry and Molecular Biology, Faculty of Science, University of Buea, Buea, South West Region, Cameroon
| | - Rene Bilingwe Ayiseh
- Department of Biochemistry and Molecular Biology, Faculty of Science, University of Buea, Buea, South West Region, Cameroon
| | - Fidelis Cho-Ngwa
- Department of Biochemistry and Molecular Biology, Faculty of Science, University of Buea, Buea, South West Region, Cameroon.
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Halliday A, Guimaraes AF, Tyrer HE, Metuge HM, Patrick CNW, Arnaud KOJ, Kwenti TDB, Forsbrook G, Steven A, Cook D, Enyong P, Wanji S, Taylor MJ, Turner JD. A murine macrofilaricide pre-clinical screening model for onchocerciasis and lymphatic filariasis. Parasit Vectors 2014; 7:472. [PMID: 25338621 PMCID: PMC4212127 DOI: 10.1186/s13071-014-0472-z] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 10/02/2014] [Indexed: 03/26/2023] Open
Abstract
Background New drugs effective against adult filariae (macrofilaricides) would accelerate the elimination of lymphatic filariasis and onchocerciasis. Anti-Onchocerca drug development is hampered by the lack of a facile model. We postulated that SCID mice could be developed as a fmacrofilaricide screening model. Methods The filaricides: albendazole (ABZ), diethylcarbamazine (DEC), flubendazole (FBZ), ivermectin (IVM) and the anti-Wolbachia macrofilaricide, minocycline (MIN) were tested in Brugia malayi (Bm)-parasitized BALB/c SCID mice vs vehicle control (VC). Responses were compared to BALB/c wild type (WT). Onchocerca ochengi male worms or onchocercomata were surgically implanted into BALB/c SCID, CB.17 SCID, BALB/c WT mice or Meriones gerbils. Survival was evaluated at 7–15 days. BALB/c SCID were tested to evaluate the responsiveness of pre-clinical macrofilaricides FBZ and rifapentine (RIFAP) against male Onchocerca. Results WT and SCID responded with >95% efficacy following ABZ or DEC treatments against Bm larvae (P < 0.0001). IVM was partially filaricidal against Bm larvae in WT and SCID (WT; 39.8%, P = 0.0356 and SCID; 56.7%, P = 0.026). SCID responded similarly to WT following IVM treatment of microfilaraemias (WT; 79%, P = 0.0194. SCID; 76%, P = 0.0473). FBZ induced a total macrofilaricidal response against adult Bm in WT and SCID (WT; P = 0.0067, SCID; P = 0.0071). MIN induced a >90% reduction in Bm Wolbachia burdens (P < 0.0001) and a blockade of microfilarial release (P = 0.0215) in SCID. Male Onchocerca survival was significantly higher in SCID vs WT mice, but not gerbils, after +15 days (60% vs 22% vs 39% P = 0.0475). Onchocercoma implants had engrafted into host tissues, with evidence of neovascularisation, after +7 days and yielded viable macro/microfilariae ex vivo. FBZ induced a macrofilaricidal effect in Onchocerca male implanted SCID at +5 weeks (FBZ; 1.67% vs VC; 43.81%, P = 0.0089). Wolbachia loads within male Onchocerca were reduced by 99% in implanted SCID receiving RIFAP for +2 weeks. Conclusions We have developed a ‘pan-filarial’ small animal research model that is sufficiently robust, with adequate capacity and throughput, to screen existing and future pre-clinical candidate macrofilaricides. Pilot data suggests a murine onchocercoma xenograft model is achievable.
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Affiliation(s)
- Alice Halliday
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Ana F Guimaraes
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Hayley E Tyrer
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | | | - Chounna Ndongmo Winston Patrick
- Research Foundation for Tropical Diseases and the Environment, Buea, Cameroon. .,Department of Microbiology and Parasitology, Parasite and Vector Research Unit, University of Buea, Buea, Cameroon.
| | - Kengne-Ouafo Jonas Arnaud
- Research Foundation for Tropical Diseases and the Environment, Buea, Cameroon. .,Department of Microbiology and Parasitology, Parasite and Vector Research Unit, University of Buea, Buea, Cameroon.
| | - Tayong Dizzle Bita Kwenti
- Research Foundation for Tropical Diseases and the Environment, Buea, Cameroon. .,Department of Microbiology and Parasitology, Parasite and Vector Research Unit, University of Buea, Buea, Cameroon.
| | - George Forsbrook
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Andrew Steven
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Darren Cook
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Peter Enyong
- Research Foundation for Tropical Diseases and the Environment, Buea, Cameroon.
| | - Samuel Wanji
- Research Foundation for Tropical Diseases and the Environment, Buea, Cameroon. .,Department of Microbiology and Parasitology, Parasite and Vector Research Unit, University of Buea, Buea, Cameroon.
| | - Mark J Taylor
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Joseph D Turner
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
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9
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Geary TG, Mackenzie CD. Progress and challenges in the discovery of macrofilaricidal drugs. Expert Rev Anti Infect Ther 2013; 9:681-95. [PMID: 21819332 DOI: 10.1586/eri.11.76] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Control of human filarial infections currently depends on chemotherapeutic strategies predominantly directed at microfilariae. Doxycycline therapy in an extended daily dose regimen sterilizes and kills adult stages, but the utility of this drug for routine field use remains an issue of concern. No macrofilaricidal drugs with efficacy after one or two doses are available for use, delaying the achievement of the elimination or eradication of onchocerciasis and lymphatic filariasis. Moxidectin, a macrocyclic lactone, is currently in clinical trials for onchocerciasis. A few other drugs that have already been approved for use in veterinary practice or in human medicine for other indications are available for investigation. Early drug discovery pipelines are poorly populated and the process of macrofilaricide discovery and development remains highly challenging. In particular, the lack of convenient, validated animal models in an antifilarial drug discovery pathway is an unresolved issue.
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Affiliation(s)
- Timothy G Geary
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue QC, H9X 3V9, Canada.
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Sharma B. Modulation of phosphofructokinase (PFK) from Setaria cervi, a bovine filarial parasite, by different effectors and its interaction with some antifilarials. Parasit Vectors 2011; 4:227. [PMID: 22152593 PMCID: PMC3261128 DOI: 10.1186/1756-3305-4-227] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Accepted: 12/07/2011] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Phosphofructokinase (ATP: D-fructose-6-phosphate-1-phosphotransferase, EC 2.7.1.11, PFK) is of primary importance in the regulation of glycolytic flux. This enzyme has been extensively studied from mammalian sources but relatively less attention has been paid towards its characterization from filarial parasites. Furthermore, the information about the response of filarial PFK towards the anthelmintics/antifilarial compounds is lacking. In view of these facts, PFK from Setaria cervi, a bovine filarial parasite having similarity with that of human filarial worms, was isolated, purified and characterized. RESULTS The S. cervi PFK was cytosolic in nature. The adult parasites (both female and male) contained more enzyme activity than the microfilarial (Mf) stage of S. cervi, which exhibited only 20% of total activity. The S. cervi PFK could be modulated by different nucleotides and the response of enzyme to these nucleotides was dependent on the concentrations of substrates (F-6-P and ATP). The enzyme possessed wide specificity towards utilization of the nucleotides as phosphate group donors. S. cervi PFK showed the presence of thiol group(s) at the active site of the enzyme, which could be protected from inhibitory action of para-chloromercuribenzoate (p-CMB) up to about 76% by pretreatment with cysteine or β-ME. The sensitivity of PFK from S. cervi towards antifilarials/anthelmintics was comparatively higher than that of mammalian PFK. With suramin, the Ki value for rat liver PFK was 40 times higher than PFK from S. cervi. CONCLUSIONS The results indicate that the activity of filarial PFK may be modified by different effectors (such as nucleotides, thiol group reactants and anthelmintics) in filarial worms depending on the presence of varying concentrations of substrates (F-6-P and ATP) in the cellular milieu. It may possess thiol group at its active site responsible for catalysis. Relatively, 40 times higher sensitivity of filarial PFK towards suramin as compared to the analogous enzyme from the mammalian system indicates that this enzyme could be exploited as a potential chemotherapeutic target against filariasis.
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Affiliation(s)
- Bechan Sharma
- Department of Biochemistry, Faculty of Science, University of Allahabad, Allahabad, UP, India.
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