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Single-Nucleotide Polymorphism Associates' β-Tubulin Isotype-1 Gene in Onchocerca volvulus Populations in Ivermectin-Treated Communities in Taraba State, Nigeria. Acta Parasitol 2022; 67:267-274. [PMID: 34279775 DOI: 10.1007/s11686-021-00427-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 05/24/2021] [Indexed: 10/20/2022]
Abstract
PURPOSE The occurrence of Single-Nucleotide Polymorphisms (SNPs) associated with repeated ivermectin treatment and sub-optimal responses reported by previous findings is of great concern in Onchocerciasis endemic areas. This study investigated SNPs' occurrence after 15 years of ivermectin intervention in Onchocerciasis endemic communities in two Local Government Areas of Taraba State, Nigeria. METHODS Microfilariae samples were collected by skin snip from individuals treated with ivermectin for 10-15 years of annual distribution and preserved in RNAlater® in a 1.5 ml micro-centrifuge tube. Genomic DNA was extracted from microfilariae and residual skin, amplification in two regions within the β-tubulin gene, sequenced and analyzed for SNPs using Bioinformatics tools. RESULTS Three distinct SNP positions: 1183 (T/G), 1188 (T/C) and 1308 (C/T) on the β-tubulin gene on the targeted 1083-1568 bp fragment, associate's with the ivermectin-treated population. Furthermore, SNPs positions detected in this study are 1730 (A/G) and 1794 (T/G) in the β-tub gene in the 1557-1857 (bp) region. The 1794 (T/G) SNP position (Phe243Val) in the exon within the β-tubulin gene region were observed in this study. CONCLUSION The present study indicates that SNPs are observed in Onchocerca volvulus, thus strengthening the warning that genetic changes could occur in some parasite populations in some ivermectin-treated areas.
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Abraham D, Graham-Brown J, Carter D, Gray SA, Hess JA, Makepeace BL, Lustigman S. Development of a recombinant vaccine against human onchocerciasis. Expert Rev Vaccines 2021; 20:1459-1470. [PMID: 34488533 DOI: 10.1080/14760584.2021.1977125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 09/02/2021] [Indexed: 01/02/2023]
Abstract
INTRODUCTION Human onchocerciasis caused by the filarial nematode parasite Onchocerca volvulus remains a major cause of debilitating disease infecting millions primarily in Sub-Saharan Africa. The development of a prophylactic vaccine, along with mass drug administration, would facilitate meeting the goal of onchocerciasis elimination by 2030. AREAS COVERED Models used to study immunity to Onchocerca include natural infection of cattle with Onchocerca ochengi and O. volvulus infective third-stage larvae implanted within diffusion chambers in mice. A vaccine, comprised of two adjuvanted recombinant antigens, induced protective immunity in genetically diverse mice suggesting that it will function similarly in diverse human populations. These antigens were recognized by immune humans and also induced protective immunity against Brugia malayi. We describe the development of a fusion protein composed of the two vaccine antigens with the plan to test the vaccine in cows and non-human primates as a prelude to the initiation of phase 1 clinical trials. EXPERT OPINION The adjuvanted O. volvulus vaccine composed of two antigens Ov-103 and Ov-RAL-2 was shown to be consistently effective at inducing protective immunity using multiple immune mechanisms. The vaccine is ready for further evaluation in other animal models before moving to clinical trials in humans.
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Affiliation(s)
- David Abraham
- Department of Microbiology and Immunology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - John Graham-Brown
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK
| | | | | | - Jessica A Hess
- Department of Microbiology and Immunology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Benjamin L Makepeace
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Sara Lustigman
- Laboratory of Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, NY, USA
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Vanhamme L, Souopgui J, Ghogomu S, Ngale Njume F. The Functional Parasitic Worm Secretome: Mapping the Place of Onchocerca volvulus Excretory Secretory Products. Pathogens 2020; 9:pathogens9110975. [PMID: 33238479 PMCID: PMC7709020 DOI: 10.3390/pathogens9110975] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 11/17/2020] [Accepted: 11/18/2020] [Indexed: 01/15/2023] Open
Abstract
Nematodes constitute a very successful phylum, especially in terms of parasitism. Inside their mammalian hosts, parasitic nematodes mainly dwell in the digestive tract (geohelminths) or in the vascular system (filariae). One of their main characteristics is their long sojourn inside the body where they are accessible to the immune system. Several strategies are used by parasites in order to counteract the immune attacks. One of them is the expression of molecules interfering with the function of the immune system. Excretory-secretory products (ESPs) pertain to this category. This is, however, not their only biological function, as they seem also involved in other mechanisms such as pathogenicity or parasitic cycle (molting, for example). We will mainly focus on filariae ESPs with an emphasis on data available regarding Onchocerca volvulus, but we will also refer to a few relevant/illustrative examples related to other worm categories when necessary (geohelminth nematodes, trematodes or cestodes). We first present Onchocerca volvulus, mainly focusing on the aspects of this organism that seem relevant when it comes to ESPs: life cycle, manifestations of the sickness, immunosuppression, diagnosis and treatment. We then elaborate on the function and use of ESPs in these aspects.
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Affiliation(s)
- Luc Vanhamme
- Department of Molecular Biology, Institute of Biology and Molecular Medicine, IBMM, Université Libre de Bruxelles, Rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium; (J.S.); (F.N.N.)
- Correspondence:
| | - Jacob Souopgui
- Department of Molecular Biology, Institute of Biology and Molecular Medicine, IBMM, Université Libre de Bruxelles, Rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium; (J.S.); (F.N.N.)
| | - Stephen Ghogomu
- Molecular and Cell Biology Laboratory, Biotechnology Unit, University of Buea, Buea P.O Box 63, Cameroon;
| | - Ferdinand Ngale Njume
- Department of Molecular Biology, Institute of Biology and Molecular Medicine, IBMM, Université Libre de Bruxelles, Rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium; (J.S.); (F.N.N.)
- Molecular and Cell Biology Laboratory, Biotechnology Unit, University of Buea, Buea P.O Box 63, Cameroon;
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Hedtke SM, Kuesel AC, Crawford KE, Graves PM, Boussinesq M, Lau CL, Boakye DA, Grant WN. Genomic Epidemiology in Filarial Nematodes: Transforming the Basis for Elimination Program Decisions. Front Genet 2020; 10:1282. [PMID: 31998356 PMCID: PMC6964045 DOI: 10.3389/fgene.2019.01282] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 11/21/2019] [Indexed: 11/25/2022] Open
Abstract
Onchocerciasis and lymphatic filariasis are targeted for elimination, primarily using mass drug administration at the country and community levels. Elimination of transmission is the onchocerciasis target and global elimination as a public health problem is the end point for lymphatic filariasis. Where program duration, treatment coverage, and compliance are sufficiently high, elimination is achievable for both parasites within defined geographic areas. However, transmission has re-emerged after apparent elimination in some areas, and in others has continued despite years of mass drug treatment. A critical question is whether this re-emergence and/or persistence of transmission is due to persistence of local parasites-i.e., the result of insufficient duration or drug coverage, poor parasite response to the drugs, or inadequate methods of assessment and/or criteria for determining when to stop treatment-or due to re-introduction of parasites via human or vector movement from another endemic area. We review recent genetics-based research exploring these questions in Onchocerca volvulus, the filarial nematode that causes onchocerciasis, and Wuchereria bancrofti, the major pathogen for lymphatic filariasis. We focus in particular on the combination of genomic epidemiology and genome-wide associations to delineate transmission zones and distinguish between local and introduced parasites as the source of resurgence or continuing transmission, and to identify genetic markers associated with parasite response to chemotherapy. Our ultimate goal is to assist elimination efforts by developing easy-to-use tools that incorporate genetic information about transmission and drug response for more effective mass drug distribution, surveillance strategies, and decisions on when to stop interventions to improve sustainability of elimination.
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Affiliation(s)
- Shannon M. Hedtke
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Annette C. Kuesel
- Unicef/UNDP/World Bank/World Health Organization Special Programme for Research and Training in Tropical Diseases (TDR), World Health Organization, Geneva, Switzerland
| | - Katie E. Crawford
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Patricia M. Graves
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, QLD, Australia
| | - Michel Boussinesq
- Unité Mixte Internationale 233 "TransVIHMI", Institut de Recherche pour le Développement (IRD), INSERM U1175, University of Montpellier, Montpellier, France
| | - Colleen L. Lau
- Department of Global Health, Research School of Population Health, Australian National University, Acton, ACT, Australia
| | - Daniel A. Boakye
- Parasitology Department, Noguchi Memorial Institute for Medical Research, Accra, Ghana
| | - Warwick N. Grant
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
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Bourguinat C, Keller K, Xia J, Lepage P, McTier TL, Woods DJ, Prichard RK. Genetic profiles of ten Dirofilaria immitis isolates susceptible or resistant to macrocyclic lactone heartworm preventives. Parasit Vectors 2017; 10:504. [PMID: 29143652 PMCID: PMC5688420 DOI: 10.1186/s13071-017-2428-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND For dogs and cats, chemoprophylaxis with macrocyclic lactone (ML) preventives for heartworm disease is widely used in the United States and other countries. Since 2005, cases of loss of efficacy (LOE) of heartworm preventives have been reported in the U.S. More recently, ML-resistant D. immitis isolates were confirmed. Previous work identified 42 genetic markers that could predict ML response in individual samples. For field surveillance, it would be more appropriate to work on microfilarial pools from individual dogs with a smaller subset of genetic markers. METHODS MiSeq technology was used to identify allele frequencies with the 42 genetic markers previously reported. Microfilaria from ten well-characterized new isolates called ZoeKY, ZoeMI, ZoeGCFL, ZoeAL, ZoeMP3, ZoeMO, ZoeAMAL, ZoeLA, ZoeJYD-34, and Metairie were extracted from fresh blood from dogs. DNA were extracted and sequenced with MiSeq technology. Allele frequencies were calculated and compared with the previously reported susceptible, LOE, and resistant D. immitis populations. RESULTS The allele frequencies identified in the current resistant and susceptible isolates were in accordance with the allele frequencies previously reported in related phenotypes. The ZoeMO population, a subset of the ZoeJYD-34 population, showed a genetic profile that was consistent with some reversion towards susceptibility compared with the parental ZoeJYD-34 population. The Random Forest algorithm was used to create a predictive model using different SNPs. The model with a combination of three SNPs (NODE_42411_RC, NODE_21554_RC, and NODE_45689) appears to be suitable for future monitoring. CONCLUSIONS MiSeq technology provided a suitable methodology to work with the microfilarial samples. The list of SNPs that showed good predictability for ML resistance was narrowed. Additional phenotypically well characterized D. immitis isolates are required to finalize the best set of SNPs to be used for large scale ML resistance screening.
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Affiliation(s)
- Catherine Bourguinat
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Sainte Anne de Bellevue, QC, H9X3V9, Canada
| | - Kathy Keller
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Sainte Anne de Bellevue, QC, H9X3V9, Canada
| | - Jianguo Xia
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Sainte Anne de Bellevue, QC, H9X3V9, Canada.,Department of Animal Science, McGill University, Sainte Anne de Bellevue, QC, Canada
| | - Pierre Lepage
- McGill University and Génome Québec Innovation Centre, Montréal, QC, Canada
| | - Tom L McTier
- Zoetis, Veterinary Medicine Research and Development, Kalamazoo, MI, USA
| | - Debra J Woods
- Zoetis, Veterinary Medicine Research and Development, Kalamazoo, MI, USA
| | - Roger K Prichard
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Sainte Anne de Bellevue, QC, H9X3V9, Canada.
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Hess JA, Zhan B, Torigian AR, Patton JB, Petrovsky N, Zhan T, Bottazzi ME, Hotez PJ, Klei TR, Lustigman S, Abraham D. The Immunomodulatory Role of Adjuvants in Vaccines Formulated with the Recombinant Antigens Ov-103 and Ov-RAL-2 against Onchocerca volvulus in Mice. PLoS Negl Trop Dis 2016; 10:e0004797. [PMID: 27387453 PMCID: PMC4936747 DOI: 10.1371/journal.pntd.0004797] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 06/01/2016] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND In some regions in Africa, elimination of onchocerciasis may be possible with mass drug administration, although there is concern based on several factors that onchocerciasis cannot be eliminated solely through this approach. A vaccine against Onchocerca volvulus would provide a critical tool for the ultimate elimination of this infection. Previous studies have demonstrated that immunization of mice with Ov-103 and Ov-RAL-2, when formulated with alum, induced protective immunity. It was hypothesized that the levels of protective immunity induced with the two recombinant antigens formulated with alum would be improved by formulation with other adjuvants known to enhance different types of antigen-specific immune responses. METHODOLOGY/ PRINCIPAL FINDINGS Immunizing mice with Ov-103 and Ov-RAL-2 in conjunction with alum, Advax 2 and MF59 induced significant levels of larval killing and host protection. The immune response was biased towards Th2 with all three of the adjuvants, with IgG1 the dominant antibody. Improved larval killing and host protection was observed in mice immunized with co-administered Ov-103 and Ov-RAL-2 in conjunction with each of the three adjuvants as compared to single immunizations. Antigen-specific antibody titers were significantly increased in mice immunized concurrently with the two antigens. Based on chemokine levels, it appears that neutrophils and eosinophils participate in the protective immune response induced by Ov-103, and macrophages and neutrophils participate in immunity induced by Ov-RAL-2. CONCLUSIONS/SIGNIFICANCE The mechanism of protective immunity induced by Ov-103 and Ov-RAL-2, with the adjuvants alum, Advax 2 and MF59, appears to be multifactorial with roles for cytokines, chemokines, antibody and specific effector cells. The vaccines developed in this study have the potential of reducing the morbidity associated with onchocerciasis in humans.
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Affiliation(s)
- Jessica A. Hess
- Department of Microbiology and Immunology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Bin Zhan
- Department of Pediatrics, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas, United States of America
- Sabin Vaccine Institute and Texas Children’s Hospital Center for Vaccine Development, Houston, Texas, United States of America
| | - April R. Torigian
- Department of Microbiology and Immunology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - John B. Patton
- Department of Microbiology and Immunology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Nikolai Petrovsky
- Department of Diabetes and Endocrinology, Flinders University, Adelaide, Australia
- Vaxine Pty Ltd, Flinders Medical Centre, Bedford Park, Adelaide, Australia
| | - Tingting Zhan
- Division of Biostatistics, Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Maria Elena Bottazzi
- Department of Pediatrics, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas, United States of America
- Sabin Vaccine Institute and Texas Children’s Hospital Center for Vaccine Development, Houston, Texas, United States of America
| | - Peter J. Hotez
- Department of Pediatrics, National School of Tropical Medicine, Baylor College of Medicine, Houston, Texas, United States of America
- Sabin Vaccine Institute and Texas Children’s Hospital Center for Vaccine Development, Houston, Texas, United States of America
| | - Thomas R. Klei
- Department of Pathobiological Sciences, LSU School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America
| | - Sara Lustigman
- Laboratory of Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
| | - David Abraham
- Department of Microbiology and Immunology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
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Vaccines to combat river blindness: expression, selection and formulation of vaccines against infection with Onchocerca volvulus in a mouse model. Int J Parasitol 2014; 44:637-46. [PMID: 24907553 DOI: 10.1016/j.ijpara.2014.04.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 04/15/2014] [Accepted: 04/16/2014] [Indexed: 01/21/2023]
Abstract
Human onchocerciasis is a neglected tropical disease caused by Onchocerca volvulus and an important cause of blindness and chronic disability in the developing world. Although mass drug administration of ivermectin has had a profound effect on control of the disease, additional tools are critically needed including the need for a vaccine against onchocerciasis. The objectives of the present study were to: (i) select antigens with known vaccine pedigrees as components of a vaccine; (ii) produce the selected vaccine antigens under controlled conditions, using two expression systems and in one laboratory and (iii) evaluate their vaccine efficacy using a single immunisation protocol in mice. In addition, we tested the hypothesis that joining protective antigens as a fusion protein or in combination, into a multivalent vaccine, would improve the ability of the vaccine to induce protective immunity. Out of eight vaccine candidates tested in this study, Ov-103, Ov-RAL-2 and Ov-CPI-2M were shown to reproducibly induce protective immunity when administered individually, as fusion proteins or in combination. Although there was no increase in the level of protective immunity induced by combining the antigens into one vaccine, these antigens remain strong candidates for inclusion in a vaccine to control onchocerciasis in humans.
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Prichard RK. Ivermectin resistance and overview of the Consortium for Anthelmintic Resistance SNPs. Expert Opin Drug Discov 2013; 2:S41-52. [PMID: 23489032 DOI: 10.1517/17460441.2.s1.s41] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Ivermectin (IVM) has transformed nematode parasite control in veterinary medicine and the control of some nematode infections in humans, such as onchocerciasais, lymphatic filariasis in Africa and strongyloidiasis. Unfortunately, IVM resistance is now a serious problem for parasite control in livestock and there is a concern about resistance development and spread in nematode parasites of humans. IVM is believed to act by opening glutamate-gated chloride channels and GABA-gated channels in invertebrate neurons or muscle cells, leading to hyperpolarisation of the cells and to an inhibitory paralysis. However, in the filarial nematodes, it is not altogether clear that the effect of IVM is confined to these actions or even whether these are the most important. Alterations in some ligand-gated ion channel (LGIC) receptor subunits may play a role in the mechanisms of IVM resistance in some nematodes, but the evidence that changes in LGICs are the most important cause of IVM resistance in nematodes is far from clear. What is evident is that IVM is an excellent substrate for some ATP-binding cassette transporters, IVM selects for changes in expression levels of ABC transporters, such as P-glycoproteins, and that altered levels of some ABC transporters contribute to IVM resistance. In addition, there is growing evidence that IVM selects on β-tubulin, at least in some nematodes. Based on these various mechanisms, which contribute to IVM resistance, it may become possible to develop panels of molecular markers for IVM resistance in different nematode parasites. In order to stimulate the development of such markers, an international Consortium for Anthelmintic Resistance SNPs (CARS) has been developed to help coordinate marker development, advance our knowledge of helminth biology and possibly assist with the development of new anthelmintic molecules.
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Affiliation(s)
- Roger K Prichard
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Sainte-Anne-de-Bellevue, QC, H9X3V9, Canada 1 514 398 7729 ; +1 514 398 7594 ;
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Nana-Djeunga H, Bourguinat C, Pion SDS, Kamgno J, Gardon J, Njiokou F, Boussinesq M, Prichard RK. Single nucleotide polymorphisms in β-tubulin selected in Onchocerca volvulus following repeated ivermectin treatment: possible indication of resistance selection. Mol Biochem Parasitol 2012; 185:10-8. [PMID: 22677339 DOI: 10.1016/j.molbiopara.2012.05.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 05/24/2012] [Accepted: 05/28/2012] [Indexed: 10/28/2022]
Abstract
The control of onchocerciasis or river blindness by mass treatment of the population with ivermectin (IVM) has been a great success until now, so that in certain foci its elimination has become feasible. However, after more than 20 years of repeated IVM mass treatment, the disease still persists in many endemic countries. Sub-optimal responses and genetic changes have been reported in Onchocerca volvulus populations under high IVM pressure but more work is needed to determine whether resistance is developing. The situation needs to be urgently clarified to preserve the achievements of onchocerciasis control programs. In this study, O. volvulus adult worms were collected from the same individuals, before IVM exposure and following three years of annual or three-monthly treatments at 150 μg/kg or 800 μg/kg. Four single nucleotide polymorphisms (SNPs) occurring in the β-tubulin gene of these parasites were investigated. We found changes in genotype frequencies in O. volvulus β-tubulin gene associated with IVM treatments. The SNP at position 1545 (A/G) showed a significant increase in frequency of the less common nucleotide in the female worms following treatment. After 13 three-monthly treatments, female worm homozygotes with the less common genotype, prior to treatment, increased in frequency. The selected homozygotes, as well as heterozygotes, appeared to be less fertile (without or with very few embryonic stages in their uteri) than the wild-type homozygotes. These results provide additional evidence for genetic selection and strengthen the warning that selection for IVM resistance may be occurring in some O. volvulus populations.
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Affiliation(s)
- Hugues Nana-Djeunga
- General Biology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon.
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Abstract
Lymphatic filariasis and onchocerciasis are parasitic helminth diseases that constitute a serious public health issue in tropical regions. The filarial nematodes that cause these diseases are transmitted by blood-feeding insects and produce chronic and long-term infection through suppression of host immunity. Disease pathogenesis is linked to host inflammation invoked by the death of the parasite, causing hydrocoele, lymphoedema, and elephantiasis in lymphatic filariasis, and skin disease and blindness in onchocerciasis. Most filarial species that infect people co-exist in mutualistic symbiosis with Wolbachia bacteria, which are essential for growth, development, and survival of their nematode hosts. These endosymbionts contribute to inflammatory disease pathogenesis and are a target for doxycycline therapy, which delivers macrofilaricidal activity, improves pathological outcomes, and is effective as monotherapy. Drugs to treat filariasis include diethylcarbamazine, ivermectin, and albendazole, which are used mostly in combination to reduce microfilariae in blood (lymphatic filariasis) and skin (onchocerciasis). Global programmes for control and elimination have been developed to provide sustained delivery of drugs to affected communities to interrupt transmission of disease and ultimately eliminate this burden on public health.
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Affiliation(s)
- Mark J Taylor
- Liverpool School of Tropical Medicine, Liverpool, UK.
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Slatko BE, Taylor MJ, Foster JM. The Wolbachia endosymbiont as an anti-filarial nematode target. Symbiosis 2010; 51:55-65. [PMID: 20730111 PMCID: PMC2918796 DOI: 10.1007/s13199-010-0067-1] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Accepted: 05/13/2010] [Indexed: 01/05/2023]
Abstract
Human disease caused by parasitic filarial nematodes is a major cause of global morbidity. The parasites are transmitted by arthropod intermediate hosts and are responsible for lymphatic filariasis (elephantiasis) or onchocerciasis (river blindness). Within these filarial parasites are intracellular alpha-proteobacteria, Wolbachia, that were first observed almost 30 years ago. The obligate endosymbiont has been recognized as a target for anti-filarial nematode chemotherapy as evidenced by the loss of worm fertility and viability upon antibiotic treatment in an extensive series of human trials. While current treatments with doxycycline and rifampicin are not practical for widespread use due to the length of required treatments and contraindications, anti-Wolbachia targeting nevertheless appears a promising alternative for filariasis control in situations where current programmatic strategies fail or are unable to be delivered and it provides a superior efficacy for individual therapy. The mechanisms that underlie the symbiotic relationship between Wolbachia and its nematode hosts remain elusive. Comparative genomics, bioinfomatic and experimental analyses have identified a number of potential interactions, which may be drug targets. One candidate is de novo heme biosynthesis, due to its absence in the genome sequence of the host nematode, Brugia malayi, but presence in Wolbachia and its potential roles in worm biology. We describe this and several additional candidate targets, as well as our approaches for understanding the nature of the host-symbiont relationship.
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Affiliation(s)
- Barton E. Slatko
- Molecular Parasitology Division, New England Biolabs, 240 County Road, Ipswich, MA 01938 USA
| | - Mark J. Taylor
- Filariasis Research Laboratory, Molecular and Biochemical Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA UK
| | - Jeremy M. Foster
- Molecular Parasitology Division, New England Biolabs, 240 County Road, Ipswich, MA 01938 USA
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Basáñez MG, Pion SDS, Boakes E, Filipe JAN, Churcher TS, Boussinesq M. Effect of single-dose ivermectin on Onchocerca volvulus: a systematic review and meta-analysis. THE LANCET. INFECTIOUS DISEASES 2008; 8:310-22. [DOI: 10.1016/s1473-3099(08)70099-9] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Churcher TS, Schwab AE, Prichard RK, Basáñez MG. An analysis of genetic diversity and inbreeding in Wuchereria bancrofti: implications for the spread and detection of drug resistance. PLoS Negl Trop Dis 2008; 2:e211. [PMID: 18382607 PMCID: PMC2275205 DOI: 10.1371/journal.pntd.0000211] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Accepted: 02/08/2008] [Indexed: 11/24/2022] Open
Abstract
Estimates of genetic diversity in helminth infections of humans often have to rely on genotyping (immature) parasite transmission stages instead of adult worms. Here we analyse the results of one such study investigating a single polymorphic locus (a change at position 200 of the beta-tubulin gene) in microfilariae of the lymphatic filarial parasite Wuchereria bancrofti. The presence of this genetic change has been implicated in benzimidazole resistance in parasitic nematodes of farmed ruminants. Microfilariae were obtained from patients of three West African villages, two of which were sampled prior to the introduction of mass drug administration. An individual-based stochastic model was developed showing that a wide range of allele frequencies in the adult worm populations could have generated the observed microfilarial genetic diversity. This suggests that appropriate theoretical null models are required in order to interpret studies that genotype transmission stages. Wright's hierarchical F-statistic was used to investigate the population structure in W. bancrofti microfilariae and showed significant deficiency of heterozygotes compared to the Hardy-Weinberg equilibrium; this may be partially caused by a high degree of parasite genetic differentiation between hosts. Studies seeking to quantify accurately the genetic diversity of helminth populations by analysing transmission stages should increase their sample size to account for the variability in allele frequency between different parasite life-stages. Helminth genetic differentiation between hosts and non-random mating will also increase the number of hosts (and the number of samples per host) that need to be genotyped, and could enhance the rate of spread of anthelmintic resistance.
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Affiliation(s)
- Thomas S Churcher
- Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, London, United Kingdom.
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Bourguinat C, Ardelli BF, Pion SDS, Kamgno J, Gardon J, Duke BOL, Boussinesq M, Prichard RK. P-glycoprotein-like protein, a possible genetic marker for ivermectin resistance selection in Onchocerca volvulus. Mol Biochem Parasitol 2007; 158:101-11. [PMID: 18215431 DOI: 10.1016/j.molbiopara.2007.11.017] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 10/27/2007] [Accepted: 11/27/2007] [Indexed: 11/29/2022]
Abstract
Ivermectin (IVM) is the only safe drug for mass-treatment of onchocerciasis. IVM resistance has been reported in gastrointestinal nematode parasites of animals. A reduction in response to IVM in Onchocerca volvulus could have significant consequences for the onchocerciasis control programs. We have found evidence that, in O. volvulus, repeated IVM treatment selects for specific alleles, of P-glycoprotein-like protein (PLP), a half-sized ABC transporter. In this study, O. volvulus samples were derived from a clinical trial in Cameroon, in which patients were sampled before, and following 3 years (1994-1997) of IVM treatments. There were four treatment groups: 150 microg/kg (1 x p.a. or 4 x p.a.) and 800 microg/kg (1 x p.a. or 4 x p.a.). DNA of O. volvulus macrofilariae was genotyped over a 476bp region of the PLP gene and at two control genes. Of the six polymorphic positions found in the PLP amplicon, three of them showed significant selection after 4 x p.a. treatment with IVM (total of 13 IVM treatments) in female worms, and one of the same single nucleotide polymorphisms (SNPs) showed significant selection in the male worms. One of the selected SNPs in the female worms caused an amino acid coding change in the putative protein sequence. We found a clear selection of some genotypes, a high SNPs association and a loss of polymorphism following 4 x p.a. treatment with IVM. These PLP SNPs and genotypes could be useful markers to follow selection for IVM resistance in the field.
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Affiliation(s)
- Catherine Bourguinat
- Institute of Parasitology, McGill University, 21 111 Lakeshore Road, Sainte Anne-de-Bellevue, Quebec, Canada H9X3V9
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15
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Abstract
Variation in the strength of selection pressures acting upon different subpopulations may cause density-dependent regulatory processes to act differentially on particular genotypes and may influence the rate of selection of adaptive traits. Using host-helminth parasite systems as examples, we investigate the impact of different positive and negative density dependence on the potential spread of anthelmintic resistance. Following chemotherapy, the negative density-dependent processes restricting parasite population growth will be relaxed, increasing the genetic contribution of resistant parasites to the next generation. Simple deterministic models of directly transmitted nematodes that merge population dynamics and genetics show that the frequency of drug-resistant alleles may increase faster in species whose population size is down-regulated by density-dependent parasite fecundity than in species with density-dependent establishment or parasite mortality. A genetically structured population dynamics model of an indirectly transmitted nematode is used to highlight how population regulation will influence the resistance allele frequency in different parasite lifestages. Results indicate that surveys aimed at monitoring the evolution of drug resistance should consider carefully which life stage to sample, and the time following treatment samples should be collected. Anthelmintic resistance offers a good opportunity to apply fundamental evolutionary and ecological principles to the management of a potentially crucial public health problem.
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Affiliation(s)
- Thomas S Churcher
- Department of Infectious Disease Epidemiology, St. Mary's Campus, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom.
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Prichard RK, Roulet A. ABC transporters and beta-tubulin in macrocyclic lactone resistance: prospects for marker development. Parasitology 2007; 134:1123-32. [PMID: 17608972 DOI: 10.1017/s0031182007000091] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Macrocyclic lactones (MLs) are highly lipophilic anthelmintics which are known to bind to and open ligand-gated ion channels. However, these anthelmintics, and particularly the avermectin members of the ML class of endectocides, are potent substrates for ABC transporters and these transporters may regulate drug concentration in both the host and the parasite. There is accumulating evidence that ivermectin (IVM), and to a lesser extent moxidectin (MOX), selects for certain alleles of P-glycoprotein and other ABC transporter genes, selects for constitutive overexpression of some of these gene products, and induces overexpression of some P-glycoproteins in nematodes. However, such mechanisms of ML resistance do not easily lend themselves to the identification of SNP markers for resistance because of the diversity of ABC transporters in nematodes, the apparent diversity of effects of different MLs, and because regulatory elements for ABC transporter gene expression are not well understood in nematodes. Another non ligand-gated ion channel gene which appears to be under IVM selection, at least in Onchocerca volvulus and Haemonchus contortus, is beta-tubulin, and a simple genetic test for this selection has been described in O. volvulus. However, further work is required to elucidate a reliable marker associated with this gene in H. contortus or other parasitic nematodes of livestock. The possible involvement of ABC transporter genes and beta-tubulin in ML resistance provides a start in developing our understanding of this phenotype and markers for its detection in field populations of parasitic nematodes. However, more work is required before these leads can provide practical SNP markers for ML resistance.
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Affiliation(s)
- R K Prichard
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, Quebec, Canada, H9X 3V9.
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17
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Bourguinat C, Pion SDS, Kamgno J, Gardon J, Duke BOL, Boussinesq M, Prichard RK. Genetic selection of low fertile Onchocerca volvulus by ivermectin treatment. PLoS Negl Trop Dis 2007; 1:e72. [PMID: 17989786 PMCID: PMC2041821 DOI: 10.1371/journal.pntd.0000072] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Accepted: 07/23/2007] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Onchocerca volvulus is the causative agent of onchocerciasis, or "river blindness". Ivermectin has been used for mass treatment of onchocerciasis for up to 18 years, and recently there have been reports of poor parasitological responses to the drug. Should ivermectin resistance be developing, it would have a genetic basis. We monitored genetic changes in parasites obtained from the same patients before use of ivermectin and following different levels of ivermectin exposure. METHODS AND FINDINGS O. volvulus adult worms were obtained from 73 patients before exposure to ivermectin and in the same patients following three years of annual or three-monthly treatment at 150 microg/kg or 800 microg/kg. Genotype frequencies were determined in beta-tubulin, a gene previously found to be linked to ivermectin selection and resistance in parasitic nematodes. Such frequencies were also determined in two other genes, heat shock protein 60 and acidic ribosomal protein, not known to be linked to ivermectin effects. In addition, we investigated the relationship between beta-tubulin genotype and female parasite fertility. We found a significant selection for beta-tubulin heterozygotes in female worms. There was no significant selection for the two other genes. Quarterly ivermectin treatment over three years reduced the frequency of the beta-tubulin "aa" homozygotes from 68.6% to 25.6%, while the "ab" heterozygotes increased from 20.9% to 69.2% in the female parasites. The female worms that were homozygous at the beta-tubulin locus were more fertile than the heterozygous female worms before treatment (67% versus 37%; p = 0.003) and twelve months after the last dose of ivermectin in the groups treated annually (60% versus 17%; p<0.001). Differences in fertility between heterozygous and homozygous worms were less apparent three months after the last treatment in the groups treated three-monthly. CONCLUSIONS The results indicate that ivermectin is causing genetic selection on O. volvulus. This genetic selection is associated with a lower reproductive rate in the female parasites. We hypothesize that this genetic selection indicates that a population of O. volvulus, which is more tolerant to ivermectin, is being selected. This selection could have implications for the development of ivermectin resistance in O. volvulus and for the ongoing onchocerciasis control programmes.
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Affiliation(s)
- Catherine Bourguinat
- Institute of Parasitology, McGill University, Sainte Anne-de-Bellevue,
Quebec, Canada
| | - Sébastien D. S. Pion
- Laboratoire de Neuroparasitologie et
Neuroépidémiologie Tropicale, Faculté de
Médecine, Limoges Cedex, France
| | - Joseph Kamgno
- National Onchocerciasis Task Force Cameroon, Yaoundé,
Cameroon
| | - Jacques Gardon
- UR 24 Epidémiologie et Prévention, Institut de
Recherche pour le Développement, La Paz, Bolivia
| | | | - Michel Boussinesq
- UR 24 Epidémiologie et Prévention,
Département Sociétés et Santé,
Institut de Recherche pour le Développement, Paris Cedex,
France
| | - Roger K. Prichard
- Institute of Parasitology, McGill University, Sainte Anne-de-Bellevue,
Quebec, Canada
- * E-mail:
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18
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Affiliation(s)
- Sara Lustigman
- Laboratory of Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America.
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Eng JKL, Blackhall WJ, Osei-Atweneboana MY, Bourguinat C, Galazzo D, Beech RN, Unnasch TR, Awadzi K, Lubega GW, Prichard RK. Ivermectin selection on beta-tubulin: evidence in Onchocerca volvulus and Haemonchus contortus. Mol Biochem Parasitol 2006; 150:229-35. [PMID: 17007942 DOI: 10.1016/j.molbiopara.2006.08.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 07/29/2006] [Accepted: 08/16/2006] [Indexed: 10/24/2022]
Abstract
Ivermectin resistance is common in trichostrongylid nematodes of livestock, such as Haemonchus contortus. This anthelmintic is the only drug approved for mass administration to control onchocerciasis caused by the nematode parasite, Onchocerca volvulus. In parts of West Africa up to 18 rounds of ivermectin treatment have been administered to communities and there are reports of poor parasitological responses to treatment. Understanding ivermectin resistance and ivermectin selection is an important step to reduce selection pressure for resistance, and to develop molecular markers which can be used to monitor the development of resistance and its spread. Here we report evidence that ivermectin selection changes the frequency of beta-tubulin alleles in both the sheep parasite, H. contortus, and the human parasite, O. volvulus. In O. volvulus we have been able to look at the frequency of beta-tubulin alleles in O. volvulus obtained before any ivermectin was used in humans in Africa, and following its widespread use. In H. contortus, we have been able to look at the frequency of beta-tubulin alleles in a strain which has not seen any anthelmintic selection and in an ivermectin selected strain derived from the unselected strain. We have found ivermectin selects on beta-tubulin in both of these nematode species. In the case of O. volvulus, we had previously reported that ivermectin selects for specific single nucleotide polymorphisms in the O. volvulus beta-tubulin gene. This polymorphism results in three amino acid changes in the H3 helix of beta-tubulin, as well as deletions in an associated intron. We report a simple PCR assay to detect the amplicon length polymorphism, resulting from these intronic deletions, which can be used to monitor the frequency of the beta-tubulin allele selected for by ivermectin in O. volvulus.
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Affiliation(s)
- J K L Eng
- Institute of Parasitology, McGill University, Sainte Anne-de-Bellevue, Quebec, Canada
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