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Jasmer DP, Rosa BA, Tyagi R, Bulman CA, Beerntsen B, Urban JF, Sakanari J, Mitreva M. De novo identification of toxicants that cause irreparable damage to parasitic nematode intestinal cells. PLoS Negl Trop Dis 2020; 14:e0007942. [PMID: 32453724 PMCID: PMC7274465 DOI: 10.1371/journal.pntd.0007942] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 06/05/2020] [Accepted: 05/04/2020] [Indexed: 02/06/2023] Open
Abstract
Efforts to identify new drugs for therapeutic and preventive treatments against parasitic nematodes have gained increasing interest with expanding pathogen omics databases and drug databases from which new anthelmintic compounds might be identified. Here, a novel approach focused on integrating a pan-Nematoda multi-omics data targeted to a specific nematode organ system (the intestinal tract) with evidence-based filtering and chemogenomic screening was undertaken. Based on de novo computational target prioritization of the 3,564 conserved intestine genes in A. suum, exocytosis was identified as a high priority pathway, and predicted inhibitors of exocytosis were tested using the large roundworm (Ascaris suum larval stages), a filarial worm (Brugia pahangi adult and L3), a whipworm (Trichuris muris adult), and the non-parasitic nematode Caenorhabditis elegans. 10 of 13 inhibitors were found to cause rapid immotility in A. suum L3 larvae, and five inhibitors were effective against the three phylogenetically diverse parasitic nematode species, indicating potential for a broad spectrum anthelmintics. Several distinct pathologic phenotypes were resolved related to molting, motility, or intestinal cell and tissue damage using conventional and novel histologic methods. Pathologic profiles characteristic for each inhibitor will guide future research to uncover mechanisms of the anthelmintic effects and improve on drug designs. This progress firmly validates the focus on intestinal cell biology as a useful resource to develop novel anthelmintic strategies.
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Affiliation(s)
- Douglas P Jasmer
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, United States of America
| | - Bruce A Rosa
- Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Rahul Tyagi
- McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Christina A Bulman
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Brenda Beerntsen
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri, United States of America
| | - Joseph F Urban
- U.S. Department of Agriculture, Northeast Area, Agricultural Research Service, Beltsville Agricultural Research Center, Animal Parasite Diseases Laboratory and Beltsville Human Nutrition Research Center, Diet Genomics and Immunology Laboratory, Beltsville, Maryland, United States of America
| | - Judy Sakanari
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Makedonka Mitreva
- Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America.,McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri, United States of America
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Jasmer DP, Rosa BA, Tyagi R, Mitreva M. Omics Driven Understanding of the Intestines of Parasitic Nematodes. Front Genet 2019; 10:652. [PMID: 31402928 PMCID: PMC6669237 DOI: 10.3389/fgene.2019.00652] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Accepted: 06/19/2019] [Indexed: 01/25/2023] Open
Abstract
The biological and molecular complexity of nematodes has impeded research on development of new therapies for treatment and control. We have focused on the versatility of the nematode intestine as a target for new therapies. To that end, it is desirable to establish a broad and deep understanding of the molecular architecture underlying intestinal cell functions at the pan-Nematoda level. Multiomics data were generated to uncover the evolutionary principles underlying both conserved and adaptable features of the nematode intestine. Whole genomes were used to reveal the functional potential of the nematodes, tissue-specific transcriptomes provided a deep assessment of genes that are expressed in the adult nematode intestine, and comparison of selected core species was used to determine a first approximation of the pan-Nematoda intestinal transcriptome. Differentially expressed transcripts were also identified among intestinal regions, with the largest number expressed at significantly higher levels in the anterior region, identifying this region as the most functionally unique compared to middle and posterior regions. Profiling intestinal miRNAs targeting these genes identified the conserved intestinal miRNAs. Proteomics of intestinal cell compartments assigned proteins to several different intestinal cell compartments (intestinal tissue, the integral and peripheral intestinal membranes, and the intestinal lumen). Finally, advanced bioinformatic approaches were used to predict intestinal cell functional categories of seminal importance to parasite survival, which can now be experimentally tested and validated. The data provide the most comprehensive compilation of constitutively and differentially expressed genes, predicted gene regulators, and proteins of the nematode intestine. The information provides knowledge that is essential to understand molecular features of nematode intestinal cells and functions of fundamental importance to the intestine of many, if not all, parasitic nematodes.
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Affiliation(s)
- Douglas P Jasmer
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, United States
| | - Bruce A Rosa
- McDonnell Genome Institute, Washington University, St. Louis, St. Louis, MI, United States
| | - Rahul Tyagi
- McDonnell Genome Institute, Washington University, St. Louis, St. Louis, MI, United States
| | - Makedonka Mitreva
- McDonnell Genome Institute, Washington University, St. Louis, St. Louis, MI, United States.,Department of Internal Medicine, Washington University School of Medicine, St. Louis, MI, United States
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Stutzer C, Richards SA, Ferreira M, Baron S, Maritz-Olivier C. Metazoan Parasite Vaccines: Present Status and Future Prospects. Front Cell Infect Microbiol 2018; 8:67. [PMID: 29594064 PMCID: PMC5859119 DOI: 10.3389/fcimb.2018.00067] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 02/26/2018] [Indexed: 12/21/2022] Open
Abstract
Eukaryotic parasites and pathogens continue to cause some of the most detrimental and difficult to treat diseases (or disease states) in both humans and animals, while also continuously expanding into non-endemic countries. Combined with the ever growing number of reports on drug-resistance and the lack of effective treatment programs for many metazoan diseases, the impact that these organisms will have on quality of life remain a global challenge. Vaccination as an effective prophylactic treatment has been demonstrated for well over 200 years for bacterial and viral diseases. From the earliest variolation procedures to the cutting edge technologies employed today, many protective preparations have been successfully developed for use in both medical and veterinary applications. In spite of the successes of these applications in the discovery of subunit vaccines against prokaryotic pathogens, not many targets have been successfully developed into vaccines directed against metazoan parasites. With the current increase in -omics technologies and metadata for eukaryotic parasites, target discovery for vaccine development can be expedited. However, a good understanding of the host/vector/pathogen interface is needed to understand the underlying biological, biochemical and immunological components that will confer a protective response in the host animal. Therefore, systems biology is rapidly coming of age in the pursuit of effective parasite vaccines. Despite the difficulties, a number of approaches have been developed and applied to parasitic helminths and arthropods. This review will focus on key aspects of vaccine development that require attention in the battle against these metazoan parasites, as well as successes in the field of vaccine development for helminthiases and ectoparasites. Lastly, we propose future direction of applying successes in pursuit of next generation vaccines.
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Affiliation(s)
- Christian Stutzer
- Tick Vaccine Group, Department of Genetics, University of Pretoria, Pretoria, South Africa
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Matthews JB, Geldhof P, Tzelos T, Claerebout E. Progress in the development of subunit vaccines for gastrointestinal nematodes of ruminants. Parasite Immunol 2017; 38:744-753. [PMID: 27726158 DOI: 10.1111/pim.12391] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 10/05/2016] [Indexed: 11/30/2022]
Abstract
The global increase in anthelmintic resistant nematodes of ruminants, together with consumer concerns about chemicals in food, necessitates the development of alternative methods of control for these pathogens. Subunit recombinant vaccines are ideally placed to fill this gap. Indeed, they are probably the only valid option for the long-term control of ruminant parasitic nematodes given the increasing ubiquity of multidrug resistance in a range of worm species across the world. The development of a subunit multicellular parasite vaccine to the point of practical application would be a groundbreaking step in the control of these important endemic infections of livestock. This review summarizes the current status of subunit vaccine development for a number of important gastrointestinal nematodes of cattle and sheep, with a focus on the limitations and problems encountered thus far, and suggestions as to how these hurdles might be overcome.
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Affiliation(s)
- J B Matthews
- Vaccines Division, Moredun Research Institute, Pentlands Science Park, Edinburgh, UK
| | - P Geldhof
- Faculty of Veterinary Medicine, Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium
| | - T Tzelos
- Vaccines Division, Moredun Research Institute, Pentlands Science Park, Edinburgh, UK
| | - E Claerebout
- Faculty of Veterinary Medicine, Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium
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Abstract
Sheep are capable of developing protective immunity to Haemonchus contortus through repeated exposure to this parasite, although this immune protection is the result of a complex interaction among age, gender, physiological status, pregnancy, lactation, nutrition and innate and adaptive immunity in the host animal. There are multiple effectors of the protective immune response, which differ depending on the developmental stage of the parasite being targeted, and our understanding of the effector mechanisms has developed considerably in the 2000s. The rational design of vaccines based on 'natural' or 'exposed' antigens depends on an understanding of this exposure-induced immunity. However, the most effective current vaccines rely on protection via the induction of high circulating antibody levels to 'hidden' gut antigens of H. contortus. The success of this latter strategy has resulted in the launch of a vaccine, which is based on extracts of the parasite's gut, to aid in the control of Haemonchus in Australia. The development of recombinant subunit vaccines based on the components of the successful native vaccine has not yet been achieved and most of the recent successes with recombinant subunit vaccines have focussed on antigens unrelated to the gut antigens. The future integration of an understanding of the immunobiology of this parasite with advances in antigen identification, expression (or synthesis) and presentation is likely to be pivotal to the further development of these recombinant subunit vaccines. Recent progress in each of the components underpinning this integrated approach is summarized in this review.
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Dicker AJ, Inglis NF, Manson EDT, Subhadra S, Illangopathy M, Muthusamy R, Knox DP. Proteomic analysis of Mecistocirrus digitatus and Haemonchus contortus intestinal protein extracts and subsequent efficacy testing in a vaccine trial. PLoS Negl Trop Dis 2014; 8:e2909. [PMID: 24901227 PMCID: PMC4046941 DOI: 10.1371/journal.pntd.0002909] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 04/16/2014] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Gastrointestinal nematode infections, such as Haemonchus contortus and Mecistocirrus digitatus, are ranked in the top twenty diseases affecting small-holder farmers' livestock, yet research into M. digitatus, which infects cattle and buffalo in Asia is limited. Intestine-derived native protein vaccines are effective against Haemonchus, yet the protective efficacy of intestine-derived M. digitatus proteins has yet to be determined. METHODOLOGY/PRINCIPAL FINDINGS A simplified protein extraction protocol (A) is described and compared to an established method (B) for protein extraction from H. contortus. Proteomic analysis of the H. contortus and M. digitatus protein extracts identified putative vaccine antigens including aminopeptidases (H11), zinc metallopeptidases, glutamate dehydrogenase, and apical gut membrane polyproteins. A vaccine trial compared the ability of the M. digitatus extract and two different H. contortus extracts to protect sheep against H. contortus challenge. Both Haemonchus fractions (A and B) were highly effective, reducing cumulative Faecal Egg Counts (FEC) by 99.19% and 99.89% and total worm burdens by 87.28% and 93.64% respectively, compared to the unvaccinated controls. There was no effect on H. contortus worm burdens following vaccination with the M. digitatus extract and the 28.2% reduction in cumulative FEC was not statistically significant. However, FEC were consistently lower in the M. digitatus extract vaccinates compared to the un-vaccinated controls from 25 days post-infection. CONCLUSIONS/SIGNIFICANCE Similar, antigenically cross-reactive proteins are found in H. contortus and M. digitatus; this is the first step towards developing a multivalent native vaccine against Haemonchus species and M. digitatus. The simplified protein extraction method could form the basis for a locally produced vaccine against H. contortus and, possibly M. digitatus, in regions where effective cold chains for vaccine distribution are limited. The application of such a vaccine in these regions would reduce the need for anthelmintic treatment and the resultant selection for anthelmintic resistant parasites.
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Affiliation(s)
- Alison J. Dicker
- Moredun Research Institute, Penicuik, Midlothian, United Kingdom
| | - Neil F. Inglis
- Moredun Research Institute, Penicuik, Midlothian, United Kingdom
| | | | - Subhra Subhadra
- Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India
| | - Manikkavasagan Illangopathy
- Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India
| | - Raman Muthusamy
- Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India
| | - David P. Knox
- Moredun Research Institute, Penicuik, Midlothian, United Kingdom
- * E-mail:
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Rao W, Isaac RE, Keen JN. An analysis of the Caenorhabditis elegans lipid raft proteome using geLC-MS/MS. J Proteomics 2010; 74:242-53. [PMID: 21070894 DOI: 10.1016/j.jprot.2010.11.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 10/20/2010] [Accepted: 11/02/2010] [Indexed: 11/16/2022]
Abstract
Lipid rafts are microdomains of the phospholipid bilayer, proposed to form semi-stable "islands" that act as a platform for several important cellular processes; major classes of raft-resident proteins include signalling proteins and glycosylphosphatidylinositol (GPI)-anchored proteins. Proteomic studies into lipid rafts have been mainly carried out in mammalian cell lines and single cell organisms. The nematode Caenorhabditis elegans, the model organism with a well-defined developmental profile, is ideally suited for the study of this subcellular locale in a complex developmental context. A study of the lipid raft proteome of C. elegans is presented here. A total of 44 proteins were identified from the lipid raft fraction using geLC-MS/MS, of which 40 have been determined to be likely raft proteins after analysis of predicted functions. Prediction of GPI-anchoring of the proteins found 21 to be potentially modified in this way, two of which were experimentally confirmed to be GPI-anchored. This work is the first reported study of the lipid raft proteome in C. elegans. The results show that raft proteins, including numerous GPI-anchored proteins, may have a variety of potentially important roles within the nematode, and will hopefully lead to C. elegans becoming a useful model for the study of lipid rafts.
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Affiliation(s)
- Wei Rao
- Institute of Integrative and Comparative Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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8
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Release of glycoprotein (GP1) from the tegumental surface of Taenia solium by phospholipase C from Clostridium perfringens suggests a novel protein-anchor to membranes. J Biomed Biotechnol 2010; 2010:910375. [PMID: 20130782 PMCID: PMC2814376 DOI: 10.1155/2010/910375] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Accepted: 10/12/2009] [Indexed: 11/17/2022] Open
Abstract
In order to explore how molecules are linked to the membrane surface in larval Taenia solium, whole cysticerci were incubated in the presence of phospholipase C from Clostridium perfringens (PLC). Released material was collected and analyzed in polyacrylamide gels with sodium dodecyl sulfate. Two major bands with apparent molecular weights of 180 and 43 kDa were observed. Western blot of released material and localization assays in cysticerci tissue sections using antibodies against five known surface glycoproteins of T. solium cysticerci indicated that only one, previously called GP1, was released. Similar localization studies using the lectins wheat-germ-agglutinin and Concanavalin A showed that N-acetyl-D-glucosamine, N-acetylneuraminic, sialic acid, αmethyl-D-mannoside, D-manose/glucose, and N-acetyl-D-glucosamine residues are abundantly present on the surface. On the other hand, we find that treatment with PLC releases molecules from the surface; they do not reveal Cross Reacting Determinant (CRD), suggesting a novel anchor to the membrane for the glycoprotein GP1.
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Advances in the sequencing of the genome of the adenophorean nematode Trichinella spiralis. Parasitology 2008; 135:869-80. [PMID: 18598573 DOI: 10.1017/s0031182008004472] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The adenophorean nematodes are evolutionarily distant from other species in the phylum Nematoda. Interspecific comparisons of predicted proteins have supported such an ancient divergence. Accordingly, Trichinella spiralis represents a basal nematode representative for genome sequencing focused on gaining a deeper insight into the evolutionary biology of nematodes. In addition, molecular characteristics that are conserved across the phylum could be of great value for control strategies with broad application. In this review, we describe and summarize progress that has been made on the sequencing and analysis of the T. spiralis genome. The genome sequence was used in preliminary analyses for the investigation of specific questions relating to the biology of T. spiralis and, more generally, to parasitic nematodes. For instance, we evaluated an unusually large DNase II-like protein family, predicted proteins of prospective interest in the parasite-host muscle cell interaction, anthelmintic targets and prospective intestinal genes, the encoded proteins (potentially) linked to immunological control against other nematodes. The results are discussed in relation to characteristics that are broadly conserved among evolutionary distant nematodes. The results lead to expectations that this genome sequence will contribute to advances in research on T. spiralis and other parasitic nematodes.
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Jasmer DP, Lahmers KK, Brown WC. Haemonchus contortus intestine: a prominent source of mucosal antigens. Parasite Immunol 2007; 29:139-51. [PMID: 17266741 DOI: 10.1111/j.1365-3024.2006.00928.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We sought to identify antigens from Haemonchus contortus, an abomasal nematode of small ruminants, that stimulate local (abomasal lymph node, ALN) CD4+ T lymphocyte responses during a primary infection. Results led to a focus on antigens from the parasite intestine. The H. contortus intestine proved to be a major source of antigens that stimulated ALN CD4+, CD25+ T lymphocyte responses during infections in lambs. When stimulated by intestinal antigens, ALN lymphocytes from these lambs expressed IL-4 and IL-13 transcripts, and, more variably, IFN-gamma. An immunoaffinity-purified fraction, enriched for H. contortus apical intestinal membrane proteins, stimulated similar ALN responses. On further fractionation, antigens from six size classes (ranging from 30 to 200 kDa) also stimulated proliferation of ALN lymphocytes. Mass spectrometry analysis of these size classes identified several known apical intestinal membrane proteins from H. contortus. The results show that H. contortus intestinal antigens warrant investigation in strategies to induce mucosal immunity against this parasite. The specific proteins identified have value for this purpose. The results are in contrast with the now generalized idea that H. contortus intestinal antigens are 'hidden' from the host immune system, and this issue is discussed. The approach also has potential application to other gastrointestinal nematode parasites.
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Affiliation(s)
- D P Jasmer
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA.
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Bethony JM, Loukas A, Hotez PJ, Knox DP. Vaccines against blood-feeding nematodes of humans and livestock. Parasitology 2007; 133 Suppl:S63-79. [PMID: 17274849 DOI: 10.1017/s0031182006001818] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This paper summarises the progress towards vaccine development against the major blood-feeding nematodes of man and livestock, the hookworms and Haemonchus contortus, respectively. The impact of the diseases and the drivers for vaccine development are summarized as well as the anticipated impact of the host immune response on vaccine design. The performance requirements are discussed and progress towards these objectives using defined larval and adult antigens, many of these being shared between species. Specific examples include the Ancylostoma secreted proteins and homologues in Haemonchus as well as proteases used for digestion of the blood meal. This discussion shows that many of the major vaccine candidates are shared between these blood-feeding species, not only those from the blood-feeding stages but also those expressed by infective L3s in the early stages of infection. Challenges for the future include: exploiting the expanding genome information for antigen discovery, use of different recombinant protein expression systems, formulation with new adjuvants, and novel methods of field testing vaccine efficacy.
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Affiliation(s)
- J M Bethony
- Centro de Pesquisas René Rachou/CPqRR, A FIOCRUZ em Minas Gerais. Rene Rachou Research Center/CPqRR, The Oswaldo Cruz Foundation, Minas Gerais, Brazil.
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Angulo-Valadez CE, Cepeda-Palacios R, Jacquiet P, Dorchies P, Prévot F, Ascencio-Valle F, Ramirez-Orduña JM, Torres F. Effects of immunization of Pelibuey lambs with Oestrus ovis digestive tract protein extracts on larval establishment and development. Vet Parasitol 2007; 143:140-6. [PMID: 16979824 DOI: 10.1016/j.vetpar.2006.08.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 07/07/2006] [Accepted: 08/02/2006] [Indexed: 10/24/2022]
Abstract
Larval midgut proteins of hematophagous parasites contain strong antigens that can be used for host immunization. This concept has been applied for immunization of Pelibuey sheep against Oestrus ovis L. (Diptera: Oestridae). The aim of this study was to examine the effect of immunization on larval establishment (LE) and development. Immunized lambs (I, n = 6) received two injections of crude gut membrane protein extracts (GMPE) from third instar larvae with Freund's incomplete adjuvant (FIA) on days 0 (Day of first immunization) and 21 (0.4 and 0.45 mg GMPE/lamb, respectively). The control group (C, n = 5) received physiological saline with FIA. Lambs were challenged with first instars on Day 29 (20 larvae) and Day 43 (25 larvae). Blood samples were collected biweekly and IgG titers were analyzed by ELISA. All lambs were slaughtered on Day 90 and number of larvae recovered, larval stage and larval weight were recorded at necropsy. No significant effect of immunization on LE (C = 28.9%; I = 31.0% P > 0.05) was observed. Antibody titers were higher in the immunized group on Day 28 (P < 0.05), but subsequently similar in both groups. Larval physiological age and weight were also significantly (P < 0.05) affected by immunization. Immunization of Pelibuey lambs with GMPE did not affect LE but did delay O. ovis larval development.
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Affiliation(s)
- C E Angulo-Valadez
- Centro de Investigaciones Biológicas del Noroeste, PO Box 128, La Paz, B C S 23000, Mexico
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Yatsuda AP, Krijgsveld J, Cornelissen AWCA, Heck AJR, de Vries E. Comprehensive analysis of the secreted proteins of the parasite Haemonchus contortus reveals extensive sequence variation and differential immune recognition. J Biol Chem 2003; 278:16941-51. [PMID: 12576473 DOI: 10.1074/jbc.m212453200] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Haemonchus contortus is a nematode that infects small ruminants. It releases a variety of molecules, designated excretory/secretory products (ESP), into the host. Although the composition of ESP is largely unknown, it is a source of potential vaccine components because ESP are able to induce up to 90% protection in sheep. We used proteomic tools to analyze ESP proteins and determined the recognition of these individual proteins by hyperimmune sera. Following two-dimensional electrophoresis of ESP, matrix-assisted laser desorption ionization time-of-flight and liquid chromatography-tandem mass spectrometry were used for protein identification. Few sequences of H. contortus have been determined. Therefore, the data base of expressed sequence tags (dbEST) and a data base consisting of contigs from Haemonchus ESTs were also consulted for identification. Approximately 200 individual spots were observed in the two-dimensional gel. Comprehensive proteomics analysis, combined with bioinformatic search tools, identified 107 proteins in 102 spots. The data include known as well as novel proteins such as serine, metallo- and aspartyl proteases, in addition to H. contortus ESP components like Hc24, Hc40, Hc15, and apical gut GA1 proteins. Novel proteins were identified from matches with H. contortus ESTs displaying high similarity with proteins like cyclophilins, nucleoside diphosphate kinase, OV39 antigen, and undescribed homologues of Caenorhabditis elegans. Of special note is the finding of microsomal peptidase H11, a vaccine candidate previously regarded as a "hidden antigen" because it was not found in ESP. Extensive sequence variation is present in the abundant Hc15 proteins. The Hc15 isoforms are differentially recognized by hyperimmune sera, pointing to a possible specific role of Hc15 in the infectious process and/or in immune evasion. This concept and the identification of multiple novel immune-recognized components in ESP should assist future vaccine development strategies.
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Affiliation(s)
- Ana P Yatsuda
- Department of Infectious Diseases and Immunology, Utrecht University, PO Box 80165, 3508 TD, Utrecht, The Netherlands
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Jasmer DP, Karanu F, Davis WC, McGuire TS. Abomasal lymph node responses to Haemonchus contortus intestinal antigens established in kid goats by infection or immunization with intestinal antigens. Parasite Immunol 2003; 25:59-68. [PMID: 12791101 DOI: 10.1046/j.1365-3024.2003.00611.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Immune responses to Haemonchus contortus intestinal antigens were evaluated using abomasal lymph node (ALN) lymphocytes from kid goats protected against challenge infection by immunization with parasite intestinal antigen, and from kids that were challenged after immunization with ovalbumin. ALN lymphocytes from the intestinal antigen-immunized group produced significantly higher antibody levels against intestinal antigens than the ovalbumin group, supporting the theory that immunization contributed to that ALN response. In contrast, intestinal lysates and membrane enriched preparations from intestinal cells stimulated significant proliferation of ALN lymphocytes in both groups. The proliferation was antigen-dependent, since intestinal antigens failed to stimulate proliferation in ALN lymphocytes from unimmunized and uninfected kids. For both the intestinal antigen and ovalbumin immunized groups, CD4+ T lymphocytes predominated in ALN lymphocytes that were stimulated to proliferate by intestinal antigens. The results indicate that H. contortus infection alone can induce ALN lymphocyte responses to intestinal antigens. In contrast to ALN lymphocyte responses, serum antibody against intestinal antigens was generally low to undetectable in ovalbumin-immunized kids following infection. Abomasal mucus from an H. contortus infected lamb was probed with a monoclonal antibody that binds to a periodate sensitive determinant on numerous H. contortus intestinal membrane and secreted proteins. Numerous bands of reactivity were detected, indicating that multiple parasite intestinal antigens were released into abomasal mucus during infection. The results, challenge the general concept that H. contortus intestinal antigens are 'hidden' from the host immune system during an infection. On the contrary, parasite intestinal proteins may be relatively abundant antigens presented to the host during infection. In addition, ALN T lymphocytes appear to provide a more sensitive measure than serum antibody to detect presentation of these antigens to the host immune system.
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Affiliation(s)
- Douglas P Jasmer
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman 99164-7040, USA.
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Knox DP, Redmond DL, Skuce PJ, Newlands GF. The contribution of molecular biology to the development of vaccines against nematode and trematode parasites of domestic ruminants. Vet Parasitol 2001; 101:311-35. [PMID: 11707304 DOI: 10.1016/s0304-4017(01)00558-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Rapid developments in molecular biology have had an enormous impact on the prospects for the development of vaccines to control the major nematode and trematode infestations of livestock. Vaccine candidates are purified using conventional protein chemistry techniques but the limitations imposed by the scarcity of parasite material provide an insurmountable barrier for commercial vaccine production by this means. The ability to purify mRNA from different parasite life-cycle stages and to prepare cDNA expression libraries from it has proven central to the identification of immunogenic parasite proteins. Potentially, protective parasite antigens can now be produced in recombinant form in a variety of vectors and this represents a key breakthrough on the road to commercial vaccine production. The contribution of molecular biology to this process is discussed using several examples, particularly in vaccine development against the pathogenic abomasal nematode of sheep and goats, Haemonchus contortus, and the liver fluke of sheep and cattle, Fasciola hepatica. The difficulties of producing recombinant proteins in the correct form, with appropriate post-translational modification and conformation, are discussed as well as emerging means of antigen delivery including DNA vaccination. The opportunities offered by genome and expressed sequence tag analyses programmes for antigen targeting are discussed in association with developing microarray and proteomics technologies which offer the prospect of large scale, rapid antigen screening and identification.
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Affiliation(s)
- D P Knox
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK.
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Knox DP, Smith WD. Vaccination against gastrointestinal nematode parasites of ruminants using gut-expressed antigens. Vet Parasitol 2001; 100:21-32. [PMID: 11522403 DOI: 10.1016/s0304-4017(01)00480-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To date, proteins isolated from the surface of the gut of gastrointestinal nematodes, particularly Haemonchus contortus, have generally proved to be useful protective antigens and several are being progressed towards recombinant protein-based vaccines. This paper describes the properties of some of the most promising antigens and summarises their performance in laboratory and field based trials. The antigens described include contortin, H11, H-gal-GP, GPI and cysteine proteinases. In addition, the discussion addresses the utility of selected antigens to protect against co-infecting nematode species such as Teladorsagia circumcincta and against related nematode infections such as Ostertagia ostertagi in cattle.
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Affiliation(s)
- D P Knox
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland EH26 0PZ, UK.
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Jasmer DP, Roth J, Myler PJ. Cathepsin B-like cysteine proteases and Caenorhabditis elegans homologues dominate gene products expressed in adult Haemonchus contortus intestine. Mol Biochem Parasitol 2001; 116:159-69. [PMID: 11522349 DOI: 10.1016/s0166-6851(01)00312-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Proteins expressed by nematode intestinal cells are potential targets for parasite control by immune or chemical based strategies. To expand our knowledge on nematode intestinal proteins, expressed sequence tags were generated for 131 cDNA clones from the intestine of adult female Haemonchus contortus. An estimated 55 distinct protein genes or gene families were identified. Predicted proteins represented diverse functions. Several predicted polypeptides were related to H. contortus proteins implicated in inducing protective immunity against challenge infections of this parasite. The dominant intestinal transcripts were represented by cathepsin B-like cysteine protease genes (cbl) (17% of protein coding expressed sequence tags (ESTs) analyzed). An estimated 11 previously undescribed cbl genes were identified, doubling the recognized members of this gene family. Multiple C-type lectin sequences were identified. Other notable sequences included a predicted Y-box binding protein, serine/threonine kinases and a cyclin E-like sequence. Predicted protein homologues were found in Caenorhabditis elegans for all but one H. contortus sequence (99%), while fewer homologues from other parasitic nematodes were found. Many of the proteases, lipase and C-type lectin homologues in C. elegans had apparent signal peptides, suggesting that they are secreted. Several gene products had no obvious similarity outside the phylum Nematoda. The ESTs identified intestinal genes with potential application to immune control, understanding of basic intestinal regulatory processes and refinement of nematode genomic resources.
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Affiliation(s)
- D P Jasmer
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA.
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18
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Abstract
Over the last decade, the anti-parasitics market has been the fastest growing sector of the overall $18 billion animal health market. While drugs for the treatment of parasites of livestock still dominate this sector and will continue to be developed or re-formulated, because of consumer demands for chemical-free food and of concerns regarding the environment and animal welfare there is a growing interest in the development of safe and effective vaccines. There is also a call for vaccines in the lucrative $3 billion-plus companion animal market. These demands for vaccines will add a greater impetus to an area that has seen tremendous success in the last 15 years. A number of anti-parasite vaccines have been developed, e.g. the recombinant 45w and EG95 oncosphere proteins against Taenia ovis and Echinococcus granulosis, respectively, and the Bm86 vaccine against Boophilus microplus. In addition, the cathepsin L vaccines against the liver fluke, Fasciola hepatica, and the H11 vaccine against Haemonchus contortus are progressing well. There are also many additional vaccine candidates for H. contortus and for other nematodes such as Ostertagia and Trichostrongylus spp. that may ultimately lead to broad-spectrum gastrointestinal worm vaccines. Live or attenuated-live vaccines are available for the control of avian coccidiosis, toxplasmosis in sheep and anaplasmosis in cattle, although molecular vaccines against protozoans are still proving elusive. The wealth of information in genomics, proteomics and immunology that has been forthcoming together will new methods of vaccine production and delivery should see many new vaccines reach the marketplace in the near future.
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Affiliation(s)
- J P Dalton
- School of Biotechnology, Dublin City University, Dublin 9, Ireland.
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Coyne CP, Brake D. Characterisation of Haemonchus contortus-derived cell populations propagated in vitro in a tissue culture environment and their potential to induce protective immunity in sheep. Int J Parasitol 2001; 31:359-76. [PMID: 11306114 DOI: 10.1016/s0020-7519(01)00116-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Cell populations derived from viable Haemonchus contortus L(3) larvae were propagated in vitro in a tissue culture environment for a prolonged period (>48 months). Microscopic evaluation of H. contortus-derived cell populations revealed gross morphological characteristics highly analogous to those described for cell types originating from species of plant nematodes propagated in vitro in a tissue culture environment for a briefer period of time (<6 months). The characterisation of extracts harvested from tissue culture populations of H. contortus-derived cells by SDS-PAGE analysis detected molecular fractions of approximately 29, 45, 55, and 200-kDa that closely correlated with reports for preparations obtained from intact/viable H. contortus larvae. Complementary investigations detected the dual biochemical expression of phosphohydrolase and aminopeptidase-M activities based on the hydrolysis of the synthetic enzyme-specific substrates, para-nitrophenylphosphate and leucine-para-nitroanaline, respectively. The identification of phosphohydrolase and aminopeptidase-M-like biochemical activity in fractions harvested from H. contortus-derived cell populations and propagated in vitro in tissue culture served as evidence validating their parasitic-origin. Further validation of H. contortus-derived cell populations propagated in tissue culture entailed the formulation of Triton X-100 extracts containing potential immunoprotective antigens with SEAM adjuvant and its administration by intramuscular injection (100 microg total protein) to healthy sheep (n=8) on day 0 (left rear-limb) and day +14 (right rear-limb). Animals on day 28 subsequently received a single oral challenge of 10,000 infective L(3)-stage H. contortus larvae. Applying ELISA methodologies, increases in antigen-specific IgM and IgG were detected in ovine serum samples. Interpretation of experimental findings revealed that sheep with the greatest antigen-specific humoral immune responses (IgG titre 1/3125) also demonstrated a degree of reduced abomasal H. contortuslarvae burdens (60% reduction). Polyclonal antibody from immunoprotected sheep was subsequently found to recognise both the: (i), digestive tract; and (ii), antigen extracts associated with intact/viable H. contortus larvae. These experimental findings reveal the potential feasibility of propagating parasite-derived cell populations in an in vitro tissue culture environment in a manner that retains their ability to express immunoprotective antigenic fractions.
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Affiliation(s)
- C P Coyne
- Veterinary Pharmacology Research Laboratory, Veterinary Research Program, College of Veterinary Medicine, Mississippi State University 39762, Mississippi, MS, USA.
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Gasser RB, Newton SE. Genomic and genetic research on bursate nematodes: significance, implications and prospects. Int J Parasitol 2000; 30:509-34. [PMID: 10731573 DOI: 10.1016/s0020-7519(00)00021-7] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Molecular genetic research on parasitic nematodes (order Strongylida) is of major significance for many fundamental and applied areas of medical and veterinary parasitology. The advent of gene technology has led to some progress for this group of nematodes, particularly in studying parasite systematics, drug resistance and population genetics, and in the development of diagnostic assays and the characterisation of potential vaccine and drug targets. This paper gives an account of the molecular biology and genetics of strongylid nematodes, mainly of veterinary socio-economic importance, indicates the implications of such research and gives a perspective on genome research for this important parasite group, in light of recent technological advances and knowledge of the genomes of other metazoan organisms.
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Affiliation(s)
- R B Gasser
- Department of Veterinary Science, The University of Melbourne, 250 Princes Highway, Werribee, Victoria, Australia.
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Ponting CP, Pallen MJ. beta-propeller repeats and a PDZ domain in the tricorn protease: predicted self-compartmentalisation and C-terminal polypeptide-binding strategies of substrate selection. FEMS Microbiol Lett 1999; 179:447-51. [PMID: 10518749 DOI: 10.1111/j.1574-6968.1999.tb08761.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Prokaryotic proteases demonstrate a variety of substrate-selection strategies that prevent uncontrolled protein degradation. Proteasomes and ClpXP-like proteases form oligomeric structures that exclude large substrates from central solvated chambers containing their active sites. Monomeric prolyl oligopeptidases have been shown to contain beta-propeller structures that similarly reduce access to their catalytic residues. By contrast, Tsp-like enzymes contain PDZ domains that are thought to specifically target C-terminal polypeptides. We have investigated the sequence of Thermoplasma acidophilum tricorn protease using recently-developed database search methods. The tricorn protease is known to associate into a 20 hexamer capsid enclosing an extremely large cavity that is 37 nm in diameter. It is unknown, however, how this enzyme selects its small oligopeptide substrates. Our results demonstrate the presence in tricorn protease of a PDZ domain and two predicted six-bladed beta-propeller domains. We suggest that the PDZ domain is involved in targeting non-polar C-terminal peptides, similar to those generated by the T. acidophilum proteasome, whereas the beta-propeller domains serve to exclude large substrates from the tricorn protease active site in a similar manner to that previously indicated for prolyl oligopeptidase.
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Affiliation(s)
- C P Ponting
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
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Rehman A, Jasmer DP. Defined characteristics of cathepsin B-like proteins from nematodes: inferred functional diversity and phylogenetic relationships. Mol Biochem Parasitol 1999; 102:297-310. [PMID: 10498185 DOI: 10.1016/s0166-6851(99)00086-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Numerous cathepsin B-like protein sequences (CBLs) have been reported from nematodes. However, the relationships among these proteins remain unclear. Here, expression of several CBL transcripts in the gut of the parasitic nematode Haemonchus contortus was demonstrated. To assess potential functional diversity, multiple nematode CBL sequences were compared with known functional domains of cathepsin B. These domains included the occluding loop, S2' and S2 subsites, and the pro region. Four groups of CBLs were defined based on variable characteristics in the occluding loop region, which incorporates a portion of the S2' subsite. Further diversity was observed in amino acids expected to contribute to the S2 subsite. In addition, short signature sequences near the cysteinyl active site region characterized known CBLs of parasites from the orders Strongylida and Rhabditida. The criteria established were used to identify two predicted CBLs from parasitic (Ascaris suum) and free-living (Caenorhabditis elegans) nematodes as potential orthologues, and provided a basis to evaluate orthologue status of other CBLs. Variability in the domains analyzed suggests substantial functional diversity in enzymatic properties of nematode CBLs. Results suggest that the selective amplification and evolution of distinct CBL lineages has contributed to differences in CBLs among species and groups of nematodes. Nutrient digestion is one potential factor promoting CBL diversification in these organisms.
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Affiliation(s)
- A Rehman
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman 99164-7040, USA
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Smith SK, Pettit D, Newlands GF, Redmond DL, Skuce PJ, Knox DP, Smith WD. Further immunization and biochemical studies with a protective antigen complex from the microvillar membrane of the intestine of Haemonchus contortus. Parasite Immunol 1999; 21:187-99. [PMID: 10320616 DOI: 10.1046/j.1365-3024.1999.00217.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Immunization of sheep with a protective antigen complex from the intestinal cells of Haemonchus contortus in Freund's adjuvant stimulated individually variable antibody responses but still conferred significant protection against parasite infection. Correlation between antibody concentration and degree of protection was suggestive of antibody being the effector mechanism. The antigen is known as Haemonchus galactose-containing glycoprotein complex (H-gal-GP) because it binds to lectins with a specificity for N-acetyl-galactosamine. Polypeptide composition analysis by polyacrylamide gel electrophoresis indicated an apparent molecular weight of about 1000 kDa and SDS gels revealed four major polypeptides, containing between 2 and 5 disulphide linked subunits, nearly all being glycosylated. N-terminal amino acid sequence was obtained from 12 subunits, ten showing homologies with cDNAs from Haemonchus encoding either pepsin, metalloprotease or cysteine protease-like enzymes. pH optima, inhibitor and various substrate studies confirmed that the native complex possessed proteolytic activities in agreement with the sequence data. Although the cDNAs predicted water soluble enzymes, little of the complex was solubilized from worm membranes without the use of a detergent, such as Triton X-100. It is hypothesized that H-gal-GP is a gut membrane associated multiprotease complex which is involved in the digestion of the blood meal and which can be neutralized by specific antibodies with drastic consequences for the parasite.
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Affiliation(s)
- S K Smith
- Moredun Research Institute, International Research Centre, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 OPZ, UK
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Newton SE, Munn EA. The development of vaccines against gastrointestinal nematode parasites, particularly Haemonchus contortus. PARASITOLOGY TODAY (PERSONAL ED.) 1999; 15:116-22. [PMID: 10322325 DOI: 10.1016/s0169-4758(99)01399-x] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many parasitic nematodes are developing resistance to chemical treatment, and the search is on to produce commercially viable molecular vaccines. Much progress has been made with highly protective 'hidden antigens', especially for Haemonchus contortus, and recent work with new 'natural antigens' has yielded promising results. Here, Sue Newton and Ed Munn review the most recent advances in these two main approaches to this problem.
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Affiliation(s)
- S E Newton
- Victorian Institute of Animal Science, 475 Mickleham Road, Attwood, Victoria 3049, Australia.
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Rehman A, Jasmer DP. A tissue specific approach for analysis of membrane and secreted protein antigens from Haemonchus contortus gut and its application to diverse nematode species. Mol Biochem Parasitol 1998; 97:55-68. [PMID: 9879887 DOI: 10.1016/s0166-6851(98)00132-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
General methods to conduct tissue specific analysis are largely lacking for nematodes. An approach is described that focused on isolation of membrane and secreted protein genes from the gut of the parasitic nematode Haemonchus contortus. The approach capitalized on a monoclonal antibody that recognizes multiple membrane and secreted worm proteins. Polyclonal antisera made against these proteins were used to screen expression cDNA libraries made either from adult worm gut or whole worm. The genes identified encode predicted or known membrane and secreted proteins from gut, including a cysteine protease, a zinc metallopeptidase and a previously described GA1 protein. Another gene, Hc40, was isolated from the whole worm cDNA library and is nearly identical to a vaccine patent sequence pBTA879. Tissue analysis demonstrated the intended focus on membrane and secreted proteins from parasite gut was achieved. Proteins related to each of those described were identified from other nematode species through data base analysis. Additionally, this analysis led to (1) identification of homologues of each gene in C. elegans; (2) deduction of a dimorphic structure in the Hc40 protein; (3) recognition of both monomorphic and dimorphic families of Hc40-related proteins; and (4) detection of two apparent classes of transcripts (mep1a and mep1b) that would each encode a divergent version of the putative zinc metallopeptidase MEP1. The tissue specific approach and information base described should generally contribute to investigations on nutrient digestion and related secretory processes in nematode gut.
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Affiliation(s)
- A Rehman
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman 99164-7040, USA
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Lazdunski CJ, Bouveret E, Rigal A, Journet L, Lloubès R, Bénédetti H. Colicin import into Escherichia coli cells. J Bacteriol 1998; 180:4993-5002. [PMID: 9748429 PMCID: PMC107532 DOI: 10.1128/jb.180.19.4993-5002.1998] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- C J Lazdunski
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Biologie Structurale et Microbiologie, CNRS, 13402 Marseille Cedex 20, France.
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Anderson TJ, Blouin MS, Beech RN. Population biology of parasitic nematodes: applications of genetic markers. ADVANCES IN PARASITOLOGY 1998; 41:219-83. [PMID: 9734295 DOI: 10.1016/s0065-308x(08)60425-x] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- T J Anderson
- Wellcome Trust Centre for Epidemiology of Infectious Disease, Department of Zoology, Oxford, UK
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