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Sandeman RM, Bowles VM, Colwell DD. The immunobiology of myiasis infections--whatever happened to vaccination? Parasite Immunol 2015; 36:605-15. [PMID: 25040047 DOI: 10.1111/pim.12128] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 07/03/2014] [Indexed: 12/30/2022]
Abstract
The current state of myiasis vaccine technologies are reviewed mainly in the primary research genera of Lucilia and Hypoderma. The importance of myiasis flies as primary causes of morbidity and mortality in agricultural species and man has not diminished despite the existence of good control strategies. However, the development of vaccines against myiasis infections has been relatively quiescent for more than 10 years despite the rapid development of genomic and proteomic analysis and of skills in data interpretation. The value of vaccine research in an era of chemical primacy is analysed. In fact, recent findings of drug resistance and the impact of animal welfare concerns should mean a renewed interest in alternative controls. The reasons that this has not been true to date are explored and new possibilities discussed.
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Affiliation(s)
- R M Sandeman
- School of Applied Sciences and Engineering, Federation University, Churchill, Vic., Australia
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Seid CA, Curti E, Jones RM, Hudspeth E, Rezende W, Pollet J, Center L, Versteeg L, Pritchard S, Musiychuk K, Yusibov V, Hotez PJ, Bottazzi ME. Expression, purification, and characterization of the Necator americanus aspartic protease-1 (Na-APR-1 (M74)) antigen, a component of the bivalent human hookworm vaccine. Hum Vaccin Immunother 2015; 11:1474-88. [PMID: 25905574 PMCID: PMC4514214 DOI: 10.1080/21645515.2015.1036207] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/13/2015] [Accepted: 03/27/2015] [Indexed: 11/08/2022] Open
Abstract
Over 400 million people living in the world's poorest developing nations are infected with hookworms, mostly of the genus Necator americanus. A bivalent human hookworm vaccine composed of the Necator americanus Glutathione S-Transferase-1 (Na-GST-1) and the Necator americanus Aspartic Protease-1 (Na-APR-1 (M74)) is currently under development by the Sabin Vaccine Institute Product Development Partnership (Sabin PDP). Both monovalent vaccines are currently in Phase 1 trials. Both Na-GST-1 and Na-APR-1 antigens are expressed as recombinant proteins. While Na-GST-1 was found to express with high yields in Pichia pastoris, the level of expression of Na-APR-1 in this host was too low to be suitable for a manufacturing process. When the tobacco plant Nicotiana benthamiana was evaluated as an expression system, acceptable levels of solubility, yield, and stability were attained. Observed expression levels of Na-APR-1 (M74) using this system are ∼300 mg/kg. Here we describe the achievements and obstacles encountered during process development as well as characterization and stability of the purified Na-APR-1 (M74) protein and formulated vaccine. The expression, purification and analysis of purified Na-APR-1 (M74) protein obtained from representative 5 kg reproducibility runs performed to qualify the Na-APR-1 (M74) production process is also presented. This process has been successfully transferred to a pilot plant and a 50 kg scale manufacturing campaign under current Good Manufacturing Practice (cGMP) has been performed. The 50 kg run has provided a sufficient amount of protein to support the ongoing hookworm vaccine development program of the Sabin PDP.
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Affiliation(s)
- Christopher A Seid
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
| | - Elena Curti
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
| | - R Mark Jones
- Fraunhofer Center for Molecular Biotechnology; Newark, DE, USA
| | - Elissa Hudspeth
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
| | - Wanderson Rezende
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
| | - Jeroen Pollet
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
| | - Lori Center
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
| | - Leroy Versteeg
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
| | - Sonya Pritchard
- Fraunhofer Center for Molecular Biotechnology; Newark, DE, USA
| | | | - Vidadi Yusibov
- Fraunhofer Center for Molecular Biotechnology; Newark, DE, USA
| | - Peter J Hotez
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
- Department of Biology; Baylor University; Waco, TX, USA
| | - Maria Elena Bottazzi
- Departments of Pediatrics and Molecular Virology and Microbiology; National School of Tropical Medicine; Baylor College of Medicine; Houston, TX, USA
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development; Houston, TX, USA
- Department of Biology; Baylor University; Waco, TX, USA
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Asojo OA, Ceccarelli C. Structure of glutathione S-transferase 1 from the major human hookworm parasite Necator americanus (Na-GST-1) in complex with glutathione. Acta Crystallogr F Struct Biol Commun 2014; 70:1162-6. [PMID: 25195885 PMCID: PMC4157412 DOI: 10.1107/s2053230x1401646x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 07/15/2014] [Indexed: 11/10/2022] Open
Abstract
Glutathione S-transferase 1 from Necator americanus (Na-GST-1) is a vaccine candidate for hookworm infection that has a high affinity for heme and metal porphyrins. As part of attempts to clarify the mechanism of heme detoxification by hookworm GSTs, co-crystallization and soaking studies of Na-GST-1 with the heme-like molecules protoporphyrin IX disodium salt, hematin and zinc protoporphyrin were undertaken. While these studies did not yield the structure of the complex of Na-GST-1 with any of these molecules, co-crystallization experiments resulted in the first structures of the complex of Na-GST-1 with the substrate glutathione. The structures of the complex of Na-GST-1 with glutathione were solved from pathological crystalline aggregates comprising more than one crystal form. These first structures of the complex of Na-GST-1 with the substrate glutathione were solved by molecular replacement from data collected with a sealed-tube home source using the previously reported apo structure as the search model.
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Affiliation(s)
- Oluwatoyin A. Asojo
- National School of Tropical Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Christopher Ceccarelli
- National School of Tropical Medicine, Baylor College of Medicine, Houston, TX 77030, USA
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Malik A, Jagirdar H, Rabbani N, Khan MS, Ahmed A, Al-Senaidy AM, Ismael MA. Optimization of storage and stability of camel liver glutathione S-transferase. Prep Biochem Biotechnol 2014; 45:650-66. [PMID: 25036813 DOI: 10.1080/10826068.2014.940973] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Glutathione S-transferases (GSTs) are multifunctional enzymes and play an important role in cellular detoxification. Besides this, GSTs act as cytosolic carrier proteins that bind hydrophobic compounds such as heme, bilirubin, steroids, and polycyclic hydrocarbons. GST has great importance in biotechnology, as it is a target for vaccine and drug development and biosensors development for xenobiotics. Moreover, the GST tag has been extensively used for protein expression and purification. Until now, biophysical properties of camel liver GST have not been characterized. In the present study we have purified camel (Camelus dromedarius) liver GST to homogeneity in a single step by affinity chromatography with 23.4-fold purification and 60.6% yield. Our results showed that maximal activity of GST was at pH 6.5 and it was stable in the pH range of 5 to 10. The optimum temperature was 55°C and the Tm was 57°C. The chemical chaperone glycerol (3.3 M) was able to protect GST activity and aggregation against thermal denaturation by stabilizing the protein structure at 50 and 57°C, respectively. However, L-arginine (125 mM) did not protect GST against thermal stress. Far-ultraviolet circular dichroism (CD) spectra showed that glycerol protected the secondary structure of GST while L-arginine induced conformational changes under thermal stress. In conclusion, our studies on the GST stability suggest that glycerol works as a stabilizer and L-arginine acts as a destabilizer.
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Affiliation(s)
- Ajamaluddin Malik
- a Protein Research Chair, Department of Biochemistry, College of Science , King Saud University , Riyadh , Saudi Arabia
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55
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Hawdon JM. Controlling Soil-Transmitted Helminths: Time to Think Inside the Box? J Parasitol 2014; 100:166-88. [DOI: 10.1645/13-412.1] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Zhan B, Beaumier CM, Briggs N, Jones KM, Keegan BP, Bottazzi ME, Hotez PJ. Advancing a multivalent 'Pan-anthelmintic' vaccine against soil-transmitted nematode infections. Expert Rev Vaccines 2014; 13:321-31. [PMID: 24392641 PMCID: PMC3934375 DOI: 10.1586/14760584.2014.872035] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ascaris lumbricoides The Sabin Vaccine Institute Product Development Partnership is developing a Pan-anthelmintic vaccine that simultaneously targets the major soil-transmitted nematode infections, in other words, ascariasis, trichuriasis and hookworm infection. The approach builds off the current bivalent Human Hookworm Vaccine now in clinical development and would ultimately add both a larval Ascaris lumbricoides antigen and an adult-stage Trichuris trichiura antigen from the parasite stichosome. Each selected antigen would partially reproduce the protective immunity afforded by UV-attenuated Ascaris eggs and Trichuris stichosome extracts, respectively. Final antigen selection will apply a ranking system that includes the evaluation of expression yields and solubility, feasibility of process development and the absence of circulating antigen-specific IgE among populations living in helminth-endemic regions. Here we describe a five year roadmap for the antigen discovery, feasibility and antigen selection, which will ultimately lead to the scale-up expression, process development, manufacture, good laboratory practices toxicology and preclinical evaluation, ultimately leading to Phase 1 clinical testing.
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Affiliation(s)
- Bin Zhan
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development, National School of Tropical Medicine, Baylor College of Medicine , Houston, TX , USA
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Acevedo N, Mohr J, Zakzuk J, Samonig M, Briza P, Erler A, Pomés A, Huber CG, Ferreira F, Caraballo L. Proteomic and immunochemical characterization of glutathione transferase as a new allergen of the nematode Ascaris lumbricoides. PLoS One 2013; 8:e78353. [PMID: 24223794 PMCID: PMC3817249 DOI: 10.1371/journal.pone.0078353] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 09/20/2013] [Indexed: 12/04/2022] Open
Abstract
Helminth infections and allergy have evolutionary and clinical links. Infection with the nematode Ascaris lumbricoides induces IgE against several molecules including invertebrate pan-allergens. These antibodies influence the pathogenesis and diagnosis of allergy; therefore, studying parasitic and non-parasitic allergens is essential to understand both helminth immunity and allergy. Glutathione transferases (GSTs) from cockroach and house dust mites are clinically relevant allergens and comparative studies between them and the GST from A. lumbricoides (GSTA) are necessary to evaluate their allergenicity. We sought to analyze the allergenic potential of GSTA in connection with the IgE response to non-parasitic GSTs. IgE to purified GSTs from Ascaris (nGSTA and rGSTA), house dust mites (rDer p 8, nBlo t 8 and rBlo t 8), and cockroach (rBla g 5) was measured by ELISA in subjects from Cartagena, Colombia. Also, multidimensional proteomic approaches were used to study the extract of A. lumbricoides and investigate the existence of GST isoforms. We found that among asthmatics, the strength of IgE levels to GSTA was significantly higher than to mite and cockroach GSTs, and there was a strong positive correlation between IgE levels to these molecules. Specific IgE to GSTA was found in 13.2% of controls and 19.5% of asthmatics. In addition nGSTA induced wheal and flare in skin of sensitized asthmatics indicating that it might be of clinical relevance for some patients. Frequency and IgE levels to GSTA were higher in childhood and declined with age. At least six GST isoforms in A. lumbricoides bind human IgE. Four isoforms were the most abundant and several amino acid substitutions were found, mainly on the N-terminal domain. In conclusion, a new allergenic component of Ascaris has been discovered; it could have clinical impact in allergic patients and influence the diagnosis of mite and cockroach allergy in tropical environments.
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Affiliation(s)
- Nathalie Acevedo
- Institute for Immunological Research, University of Cartagena, Cartagena, Colombia
- Foundation for the Development of Medical and Biological Sciences, Cartagena, Colombia
| | - Jens Mohr
- Department of Molecular Biology, Division of Chemistry and Bioanalytics, University of Salzburg, Salzburg, Austria
| | - Josefina Zakzuk
- Institute for Immunological Research, University of Cartagena, Cartagena, Colombia
- Foundation for the Development of Medical and Biological Sciences, Cartagena, Colombia
| | - Martin Samonig
- Department of Molecular Biology, Division of Chemistry and Bioanalytics, University of Salzburg, Salzburg, Austria
| | - Peter Briza
- Department of Molecular Biology, Division of Allergy and Immunology, University of Salzburg, Salzburg, Austria
| | - Anja Erler
- Department of Molecular Biology, Division of Allergy and Immunology, University of Salzburg, Salzburg, Austria
| | - Anna Pomés
- Indoor Biotechnologies Inc., Charlottesville, Virginia, United States of America
| | - Christian G. Huber
- Department of Molecular Biology, Division of Chemistry and Bioanalytics, University of Salzburg, Salzburg, Austria
| | - Fatima Ferreira
- Department of Molecular Biology, Division of Allergy and Immunology, University of Salzburg, Salzburg, Austria
| | - Luis Caraballo
- Institute for Immunological Research, University of Cartagena, Cartagena, Colombia
- Foundation for the Development of Medical and Biological Sciences, Cartagena, Colombia
- * E-mail:
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58
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Kelleher A, Zhan B, Asojo OA. Structure of monomeric Na-GST-3, a glutathione S-transferase from the major human hookworm parasite Necator americanus. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:839-43. [PMID: 23908024 PMCID: PMC3729155 DOI: 10.1107/s1744309113017661] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Accepted: 06/26/2013] [Indexed: 11/10/2022]
Abstract
Necator americanus is the major cause of human hookworm infection, which is a global cause of anemia in the developing world. Ongoing efforts to control hookworm infection include the identification of candidate vaccine antigens as well as potential therapeutic targets from the infective L3 larval stages and adult stages of the parasite. One promising family of proteins are the adult-stage-secreted cytosolic glutathione S-transferases (GSTs). Nematode GSTs facilitate the inactivation and degradation of a variety of electrophilic substrates (drugs) via the nucleophilic addition of reduced glutathione. Parasite GSTs also play significant roles in multi-drug resistance and the modulation of host immune defense mechanisms. Here, the structure of Na-GST-3, one of three GSTs secreted by adult-stage N. americanus, is reported. Unlike most GST structures, the Na-GST-3 crystal contains a monomer in the asymmetric unit. However, the monomer forms a prototypical GST dimer across the crystallographic twofold. A glutathione from the fermentation process is bound to the monomer. The overall binding cavity of Na-GST-3 is reminiscent of that of other N. americanus GSTs and is larger and capable of binding a wider array of ligands than GSTs from organisms that have other major detoxifying mechanisms. Furthermore, despite having low sequence identity to the host GST, Na-GST-3 has a greater tertiary-structure similarity to human sigma-class GST than was observed for the other N. americanus GSTs.
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Affiliation(s)
- Alan Kelleher
- Department of Pediatrics and National School of Tropical Medicine, Baylor College of Medicine, 1102 Bates Avenue BCM 320, Houston, TX 77030, USA
| | - Bin Zhan
- Department of Pediatrics and National School of Tropical Medicine, Baylor College of Medicine, 1102 Bates Avenue BCM 320, Houston, TX 77030, USA
| | - Oluwatoyin A. Asojo
- Department of Pediatrics and National School of Tropical Medicine, Baylor College of Medicine, 1102 Bates Avenue BCM 320, Houston, TX 77030, USA
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Ansell BRE, Schnyder M, Deplazes P, Korhonen PK, Young ND, Hall RS, Mangiola S, Boag PR, Hofmann A, Sternberg PW, Jex AR, Gasser RB. Insights into the immuno-molecular biology of Angiostrongylus vasorum through transcriptomics--prospects for new interventions. Biotechnol Adv 2013; 31:1486-500. [PMID: 23895945 DOI: 10.1016/j.biotechadv.2013.07.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 06/28/2013] [Accepted: 07/16/2013] [Indexed: 10/26/2022]
Abstract
Angiostrongylus vasorum is a metastrongyloid nematode of dogs and other canids of major clinical importance in many countries. In order to gain first insights into the molecular biology of this worm, we conducted the first large-scale exploration of its transcriptome, and predicted essential molecules linked to metabolic and biological processes as well as host immune responses. We also predicted and prioritized drug targets and drug candidates. Following Illumina sequencing (RNA-seq), 52.3 million sequence reads representing adult A. vasorum were assembled and annotated. The assembly yielded 20,033 contigs, which encoded proteins with 11,505 homologues in Caenorhabditis elegans, and additional 2252 homologues in various other parasitic helminths for which curated data sets were publicly available. Functional annotation was achieved for 11,752 (58.6%) proteins predicted for A. vasorum, including peptidases (4.5%) and peptidase inhibitors (1.6%), protein kinases (1.7%), G protein-coupled receptors (GPCRs) (1.5%) and phosphatases (1.2%). Contigs encoding excretory/secretory and immuno-modulatory proteins represented some of the most highly transcribed molecules, and encoded enzymes that digest haemoglobin were conserved between A. vasorum and other blood-feeding nematodes. Using an essentiality-based approach, drug targets, including neurotransmitter receptors, an important chemosensory ion channel and cysteine proteinase-3 were predicted in A. vasorum, as were associated small molecular inhibitors/activators. Future transcriptomic analyses of all developmental stages of A. vasorum should facilitate deep explorations of the molecular biology of this important parasitic nematode and support the sequencing of its genome. These advances will provide a foundation for exploring immuno-molecular aspects of angiostrongylosis and have the potential to underpin the discovery of new methods of intervention.
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Affiliation(s)
- Brendan R E Ansell
- Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria, Australia
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60
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Morris D, Khurasany M, Nguyen T, Kim J, Guilford F, Mehta R, Gray D, Saviola B, Venketaraman V. Glutathione and infection. Biochim Biophys Acta Gen Subj 2013; 1830:3329-49. [DOI: 10.1016/j.bbagen.2012.10.012] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 10/10/2012] [Accepted: 10/12/2012] [Indexed: 01/16/2023]
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61
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Yuan X, Fleming MD, Hamza I. Heme transport and erythropoiesis. Curr Opin Chem Biol 2013; 17:204-11. [PMID: 23415705 DOI: 10.1016/j.cbpa.2013.01.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 01/15/2013] [Accepted: 01/16/2013] [Indexed: 11/24/2022]
Abstract
In humans, systemic heme homeostasis is achieved via coordinated regulation of heme synthesis, transport and degradation. Although the heme biosynthesis and degradation pathways have been well characterized, the pathways for heme trafficking and incorporation into hemoproteins remain poorly understood. In the past few years, researchers have exploited genetic, cellular and biochemical tools, to identify heme transporters and, in the process, reveal unexpected functions for this elusive group of proteins. However, given the complexity of heme trafficking pathways, current knowledge of heme transporters is fragmented and sometimes contradictory. This review seeks to focus on recent studies on heme transporters with specific emphasis on their functions during erythropoiesis.
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Affiliation(s)
- Xiaojing Yuan
- Department of Animal & Avian Sciences, University of Maryland, College Park, MD 20742, USA
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62
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Molecular cloning and characterisation of in vitro immune response against astacin-like metalloprotease Ace-MTP-2 from Ancylostoma ceylanicum. Exp Parasitol 2013; 133:472-82. [PMID: 23376445 DOI: 10.1016/j.exppara.2013.01.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 12/03/2012] [Accepted: 01/09/2013] [Indexed: 11/23/2022]
Abstract
Ancylostoma ceylanicum belongs to the group of parasites commonly known as hookworms, blood-sucking nematodes which infect around 576 million people and hundreds of millions of animals. The interactions between these parasites and host immune systems are complicated and yet to be determined. Hookworm infections are usually long lasting and recurrent, due in part to their ability to synthesize macromolecules capable of modulating the host immune response. The interaction of parasite proteins with host immune systems has been proven, but so far there is no data describing the influence of astacin-like metalloproteases (expressed among different parasitic nematodes) on the human immune system. The cDNA encoding A. ceylanicum metalloprotease 2 (Ace-mtp-2) was cloned using RACE-PCR. Computational analysis was used to examine the immunogenicity and recombinant Ace-MTP-2 was used to investigate its influence on human THP-1 monocytes and macrophages. The Ace-mtp-2 gene encodes an astascin-like metalloprotease, with a theoretical molecular mass of 26.7 kDa. The protease has a putative signal peptide, 11 potential phosphorylation sites, and two disulfide bridges revealed by computational analysis. Maximal expression of Ace-mtp-2 by A. ceylanicum occurs in the adult stage of the parasite, and Western blot indicates the secretory nature of the protease. This suggests the protease is working at the host-parasite interface and would likely be exposed to the hosts immune response. Recombinant protein were expressed in Escherichia coli and Pichia pastoris. Recombinant Ace-MTP-2 amplified the in vitro release of TNFα and induced release of IFNγ by lipopolysaccharide activated THP-1 macrophages. The presence of Ace-MTP-2 in secretory products of the adult parasite and the induction of IFNγ release may suggest an important role for Ace-MTP-2 in host-parasite interactions since IFNγ is suggested to be responsible for the protective immune response against adult hookworms.
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Hotez PJ, Bethony JM. Parasitic disease vaccines. Vaccines (Basel) 2013. [DOI: 10.1016/b978-1-4557-0090-5.00059-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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64
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Pearson MS, Tribolet L, Cantacessi C, Periago MV, Valero MA, Valerio MA, Jariwala AR, Hotez P, Diemert D, Loukas A, Bethony J. Molecular mechanisms of hookworm disease: stealth, virulence, and vaccines. J Allergy Clin Immunol 2012; 130:13-21. [PMID: 22742835 DOI: 10.1016/j.jaci.2012.05.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 05/24/2012] [Accepted: 05/25/2012] [Indexed: 12/31/2022]
Abstract
Hookworms produce a vast repertoire of structurally and functionally diverse molecules that mediate their long-term survival and pathogenesis within a human host. Many of these molecules are secreted by the parasite, after which they interact with critical components of host biology, including processes that are key to host survival. The most important of these interactions is the hookworm's interruption of nutrient acquisition by the host through its ingestion and digestion of host blood. This results in iron deficiency and eventually the microcytic hypochromic anemia or iron deficiency anemia that is the clinical hallmark of hookworm infection. Other molecular mechanisms of hookworm infection cause a systematic suppression of the host immune response to both the parasite and to bystander antigens (eg, vaccines or allergens). This is achieved by a series of molecules that assist the parasite in the stealthy evasion of the host immune response. This review will summarize the current knowledge of the molecular mechanisms used by hookworms to survive for extended periods in the human host (up to 7 years or longer) and examine the pivotal contributions of these molecular mechanisms to chronic hookworm parasitism and host clinical outcomes.
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Affiliation(s)
- Mark S Pearson
- Center for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Cairns, Australia.
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He G, Chen S, Wang T, Yan Y, Zhang Z, Li D, Yu H, Xie Y, Wang C, Gu X, Wang S, Peng X, Yang G. Sequence Analysis of the Bs-Ag1 Gene of Baylisascaris schroederi from the Giant Panda and an Evaluation of the Efficacy of a Recombinant Baylisascaris schroederi Bs-Ag1 Antigen in Mice. DNA Cell Biol 2012; 31:1174-81. [DOI: 10.1089/dna.2011.1395] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Affiliation(s)
- Guangzhi He
- Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China
| | - Sijie Chen
- Sichuan Entry-Exit Inspection and Quarantine Bureau, Chengdu, China
| | - Tao Wang
- Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China
| | - Yubo Yan
- Sichuan Entry-Exit Inspection and Quarantine Bureau, Chengdu, China
| | - Zhihe Zhang
- The Sichuan Key Laboratory for Conservation Biology on Endangered Wildlife-Developing Toward a State Key Laboratory for China, Chengdu Research Base of Giant Panda Breeding, Chengdu, Sichuan, China
| | - Desheng Li
- China Conservation and Research Center for Giant Panda, Wolong, China
| | - Hua Yu
- Sichuan Entry-Exit Inspection and Quarantine Bureau, Chengdu, China
| | - Yue Xie
- Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China
| | - Chengdong Wang
- China Conservation and Research Center for Giant Panda, Wolong, China
| | - Xiaobin Gu
- Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China
| | - Shuxian Wang
- Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China
| | - Xuerong Peng
- Department of Chemistry, College of Life and Basic Science, Sichuan Agricultural University, Ya'an, China
| | - Guangyou Yang
- Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China
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Plieskatt JL, Rezende WC, Olsen CM, Trefethen JM, Joshi SB, Middaugh CR, Hotez PJ, Bottazzi ME. Advances in vaccines against neglected tropical diseases: enhancing physical stability of a recombinant hookworm vaccine through biophysical and formulation studies. Hum Vaccin Immunother 2012; 8:765-76. [PMID: 22495115 DOI: 10.4161/hv.19726] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A bivalent recombinant vaccine for human hookworm disease is under development. One of the lead candidate antigens in the vaccine is a glutathione S-transferase cloned from the hookworm Necator americanus (Na-GST-1) which is expressed in the yeast Pichia pastoris. Based on preliminary studies demonstrating that the recombinant protein was not stable in an acetate buffer at pH 6, we undertook an extensive stability analysis of the molecule. To improve and optimize stability we complemented traditional methods employed for macromolecule and vaccine stabilization with biophysical techniques that were incorporated into a systematic process based on an eigenvector approach. Large data sets, obtained from a variety of experimental methods were used to establish a color map ("empirical phase diagram") of the physical stability of the vaccine antigen over a wide range of temperature and pH. The resulting map defined "apparent phase boundaries" that were used to develop high throughput screening assays. These assays were then employed to identify excipients that stabilized the antigen against physical degradation that could otherwise result in losses of physicochemical integrity, immunogenicity, and potency of the vaccine. Based on these evaluations, the recombinant Na-GST-1 antigen was reformulated and ultimately produced under Good Manufacturing Practices and with an acceptable stability profile.
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Affiliation(s)
- Jordan L Plieskatt
- Department of Microbiology, Immunology and Tropical Medicine, The George Washington University, Washington, DC, USA.
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Goud GN, Deumic V, Gupta R, Brelsford J, Zhan B, Gillespie P, Plieskatt JL, Tsao EI, Hotez PJ, Bottazzi ME. Expression, purification, and molecular analysis of the Necator americanus glutathione S-transferase 1 (Na-GST-1): a production process developed for a lead candidate recombinant hookworm vaccine antigen. Protein Expr Purif 2012; 83:145-51. [PMID: 22503665 DOI: 10.1016/j.pep.2012.03.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 03/23/2012] [Indexed: 11/18/2022]
Abstract
The enzyme Necator americanus glutathione S-transferase 1 (Na-GST-1) belongs to a unique Nu class of GSTs and is a lead candidate antigen in a bivalent human hookworm vaccine. Here we describe the expression of Na-GST-1 in the yeast Pichia pastoris at the 20 L manufacturing scale and its purification process performed by three chromatographic steps, comprised of a Q Sepharose XL anion exchange column, followed by a Butyl Sepharose HP hydrophobic affinity column and a Superdex 75 size-exclusion column. Approximately 1.5 g of recombinant protein was recovered at an overall process yield of 51%, with a purity grade of 98% and the absence of detectable host cell protein. By mass spectrometry the recombinant protein exhibits a mass of 23,676Da, which closely matches the predicted molecular mass of the protein. The expression and purification methods described here are suitable for further scale-up product development and for its use to design formulation processes suitable to generate a vaccine for clinical testing.
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Affiliation(s)
- Gaddam Narsa Goud
- Department of Microbiology, Immunology & Tropical Medicine, George Washington University Medical Center, Washington, DC, USA
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Xue J, Zhan B, Guo J, He N, Qiang HQ, Hotez P, Xiao SH. Acquired hookworm immunity in the golden hamster (Mesocricetus auratus) elicited by living Necator americanus third-stage infective larvae. Exp Parasitol 2012; 130:6-12. [DOI: 10.1016/j.exppara.2011.10.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 06/01/2011] [Accepted: 10/07/2011] [Indexed: 11/26/2022]
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Schneider B, Jariwala AR, Periago MV, Gazzinelli MF, Bose SN, Hotez PJ, Diemert DJ, Bethony JM. A history of hookworm vaccine development. HUMAN VACCINES 2011; 7:1234-44. [PMID: 22064562 DOI: 10.4161/hv.7.11.18443] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The human hookworms Necator americanus and Ancylostoma duodenale remain among the most common infections of humans in areas of rural poverty in the developing regions of the world, with an estimated 1 billion people infected with one or more of these parasites. Herein, we review the nearly 100 years of research, development, animal testing, and fieldwork that have led to our current progress in recombinant hookworm vaccines. We begin with the identification of hookworm at the start of the 20th century in Southern US, then discuss the progress in developed countries to eliminate human hookworm infection, and then the industrial development and field use in the 1970s a canine hookworm vaccine(Ancylostoma caninum), and finally our progress to date in the development and clinical testing of an array of recombinant antigens to prevent human hookworm disease from N. americanus infection. Special attention is given to the challenges faced in the development of a vaccine against a blood-feeding nematode, including the epidemiology of infection (high prevalence of infection), pathogenesis (chronic infection that increases with the age of the host), and a robust immune response that fails to confer the protection in the host and a concomitant absence of correlates of protection by a successful vaccine could be developed and tested. Finally, we provide the optimal and acceptable profiles of a human hookworm vaccine, including the proposed indication, target population, and route of administration, as developed by the Human Hookworm Vaccine Initiative, the only group currently working on vaccines targeting this parasite.
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Affiliation(s)
- Brent Schneider
- Department of Microbiology, Immunology and Tropical Medicine, The George Washington University Medical Center; Washington, DC USA
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Abraham D, Hess JA, Mejia R, Nolan TJ, Lok JB, Lustigman S, Nutman TB. Immunization with the recombinant antigen Ss-IR induces protective immunity to infection with Strongyloides stercoralis in mice. Vaccine 2011; 29:8134-40. [PMID: 21856350 DOI: 10.1016/j.vaccine.2011.08.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 07/20/2011] [Accepted: 08/05/2011] [Indexed: 10/17/2022]
Abstract
Human intestinal infections with the nematode Strongyloides stercoralis remain a significant problem worldwide and a vaccine would be a useful addition to the tools available to prevent and control this infection. The goal of this study was to test single antigens for their efficacy in a vaccine against S. stercoralis larvae in mice. Alum was used as the adjuvant in these studies and antigens selected for analysis were either recognized by protective human IgG (Ss-TMY-1, Ss-EAT-6, and Ss-LEC-5) or were known to be highly immunogenic in humans (Ss-NIE-1 and Ss-IR). Only mice immunized with the Ss-IR antigen demonstrated a significant decrease of approximately 80% in the survival of larval parasites in the challenge infection. Antibodies, recovered from mice with protective immunity to S. stercoralis after immunization with Ss-IR, were used to locate the antigen in the larvae. Confocal microscopy revealed that IgG from mice immunized with Ss-IR bound to the surface of the parasites and observations by electron microscopy indicated that IgG bound to granules in the glandular esophagus. Serum collected from mice immunized with Ss-IR passively transferred immunity to naïve mice. These studies demonstrate that Ss-IR, in combination with alum, induces high levels of protective immunity through an antibody dependent mechanism and may therefore be suitable for further development as a vaccine against human strongyloidiasis.
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Affiliation(s)
- David Abraham
- Department of Microbiology and Immunology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA.
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Bal M, Mandal N, Achary KG, Das MK, Kar SK. Immunoprophylactic potential of filarial glutathione-s-transferase in lymphatic filariaisis. ASIAN PAC J TROP MED 2011; 4:185-91. [PMID: 21771450 DOI: 10.1016/s1995-7645(11)60066-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 11/08/2010] [Accepted: 12/15/2010] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE To elucidates the immunoprophylactic potential of glutathion-s-transferase (GST) from cattle filarial parasite Setaria digitata (S. digitata) against lymphatic filariasis. METHODS GST was purified through affinity chromatography (SdGST) and chacterized by SDS-PAGE and Nano-LC MS/MS analysis. Antibody isotypes to SdGST were measured by ELISA. Antibody dependant cellular cytotoxicity (ADCC) was performed in vitro using sera from immunized animals and immune individuals. T-cell proliferation and cytokine response to SdGST in different groups of filariasis were measured. Immunoprophylactic potential of SdGST was evaluate in animal model. RESULTS SdGST exhibited 30-fold enhancement of enzyme activity over crude parasitic extract. It was found to be 26 kDa by SDS-PAGE. Nano LC-MS/MS analysis followed by blast search showed 100% homology with Dirofilaria immitis (D. immitis) and only 43% with Homo sapiens (H. sapiens). Immunoblotting analysis showed putatively immune individuals carry significant level of antibodies to SdGST as compared with microfilaraemics. Immunized sera and sera endemic normal could neutralize the enzymatic activity of SdGST and inducing in vitro cytotoxicity of microfilariae. Peripheral blood mononuclear cells (PBMC) from endemic normals upon stimulation with SdGST showed a mixed type of Th1/Th2 response. SdGST immunization clear microfilariae from circulation in S. digitata implanted mastomys. CONCLUSIONS The heterologous GST could be potentially developed as a vaccine candidate against lymphatic filarial parasite.
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Affiliation(s)
- Madhusmita Bal
- Division of Immunology, Regional Medical Research Centre (Indian Council of Medical Research) Chandrasekharpur, Bhubaneswar-751023, India.
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Bethony JM, Cole RN, Guo X, Kamhawi S, Lightowlers MW, Loukas A, Petri W, Reed S, Valenzuela JG, Hotez PJ. Vaccines to combat the neglected tropical diseases. Immunol Rev 2011; 239:237-70. [PMID: 21198676 DOI: 10.1111/j.1600-065x.2010.00976.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The neglected tropical diseases (NTDs) represent a group of parasitic and related infectious diseases such as amebiasis, Chagas disease, cysticercosis, echinococcosis, hookworm, leishmaniasis, and schistosomiasis. Together, these conditions are considered the most common infections in low- and middle-income countries, where they produce a level of global disability and human suffering equivalent to better known conditions such as human immunodeficiency virus/acquired immunodeficiency syndrome and malaria. Despite their global public health importance, progress on developing vaccines for NTD pathogens has lagged because of some key technical hurdles and the fact that these infections occur almost exclusively in the world's poorest people living below the World Bank poverty line. In the absence of financial incentives for new products, the multinational pharmaceutical companies have not embarked on substantive research and development programs for the neglected tropical disease vaccines. Here, we review the current status of scientific and technical progress in the development of new neglected tropical disease vaccines, highlighting the successes that have been achieved (cysticercosis and echinococcosis) and identifying the challenges and opportunities for development of new vaccines for NTDs. Also highlighted are the contributions being made by non-profit product development partnerships that are working to overcome some of the economic challenges in vaccine manufacture, clinical testing, and global access.
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Affiliation(s)
- Jeffrey M Bethony
- Microbiology, Immunology, and Tropical Medicine, George Washington University Medical Center, Washington, DC 20037, USA.
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Twenty-first century progress toward the global control of human hookworm infection. Curr Infect Dis Rep 2011; 13:210-7. [PMID: 21462001 DOI: 10.1007/s11908-011-0182-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Hookworms are bloodsucking nematodes that afflict up to 740 million persons in tropical and subtropical regions, with Asia and sub-Saharan Africa exhibiting particularly high infection rates. Prevalence, intensity, and pathology often vary considerably at both the regional and local level, and may be influenced by coinfection with other parasitic infections such as malaria. Immunoepidemiological studies suggest that hookworms manipulate the host immune response and may provide some protection from allergy and asthma. There has been substantial progress in elucidating the molecular pathogenesis of hookworm disease, with anticoagulants, protease inhibitors, digestive proteases, and novel excretory/secretory proteins being of particular interest. Mass chemotherapy remains a mainstay of hookworm control strategies, although continued use of drugs may lead to reduced efficacy and treatment failures have been observed. Consequently, a need exists for innovative approaches, such as vaccination; recent studies have identified and/or evaluated candidate vaccine antigens in human and animal models.
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Jariwala AR, Oliveira LM, Diemert DJ, Keegan B, Plieskatt JL, Periago MV, Bottazzi ME, Hotez PJ, Bethony JM. Potency testing for the experimental Na-GST-1 hookworm vaccine. Expert Rev Vaccines 2011; 9:1219-30. [PMID: 20923271 DOI: 10.1586/erv.10.107] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Over the next decade, a new generation of vaccines will target the neglected tropical diseases (NTDs). The goal of most NTD vaccines will be to reduce the morbidity and decrease the chronic debilitating nature of these often-forgotten infections – outcomes that are hard to measure in the traditional potency testing paradigm. The absence of measurable correlates of protection, a lack of permissive animal models for lethal infection, and a lack of clinical indications that do not include the induction of sterilizing immunity required us to reconsider the traditional bioassay methods for determining vaccine potency. Owing to these limitations, potency assay design for NTD vaccines will increasingly rely on a paradigm where potency testing is one among many tools to ensure that a manufacturing process yields a product of consistent quality. Herein, we discuss the evolution of our thinking regarding the design of a potency assay along these newly defined lines and its application to the release of the experimental Necator americanus-glutathione-S- transferase-1 (Na-GST-1) vaccine to prevent human hookworm infection. We discuss the necessary steps to accomplish the design and implementation of such a new potency assay as a resource for the burgeoning NTD vaccine community. Our experience is that much of the existing information is proprietary and needs to be pulled together in a single source to aid in our overall understanding of potency testing.
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Jiang D, Zhan B, Mayor RS, Gillespie P, Keegan B, Bottazzi ME, Hotez P. Ac-AP-12, a novel factor Xa anticoagulant peptide from the esophageal glands of adult Ancylostoma caninum. Mol Biochem Parasitol 2011; 177:42-8. [PMID: 21251931 DOI: 10.1016/j.molbiopara.2011.01.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 01/03/2011] [Accepted: 01/06/2011] [Indexed: 10/18/2022]
Abstract
Immunoscreening an Ancylostoma caninum cDNA library with canine hookworm-infected dog serum resulted in the isolation of a 461 bp cDNA encoding Ac-AP-12, a new 9.1 kDa anticoagulant peptide (100 amino acids) with 43-69% amino acid homology to other nematode anticoagulant peptides (NAPs) from Ancylostoma hookworms. Messenger RNA transcription and expression of Ac-AP-12 was unique to the adult stage of A. caninum. The yeast expressed recombinant Ac-AP-12 demonstrated potent anticoagulant activity on human blood plasma in a concentration dependent manner, and was shown to specifically inhibit human factor Xa activity. Immunolocalization with specific rabbit antiserum showed that Ac-AP-12 was exclusively located in the esophageal glands of adult hookworm. Ac-AP-12 is hypothesized to facilitate both parasite blood feeding and digestion.
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Affiliation(s)
- Desheng Jiang
- Department of Microbiology, Immunology and Tropical Medicine, The George Washington University and the Sabin Vaccine Institute, Washington, DC 20037, USA
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Joachim A, Lautscham E, Christoffers J, Ruttkowski B. Oesophagostomum dentatum: effect of glutathione S-transferase (GST) inhibitors on GST activity and larval development. Exp Parasitol 2011; 127:762-7. [PMID: 21241694 DOI: 10.1016/j.exppara.2011.01.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 12/22/2010] [Accepted: 01/11/2011] [Indexed: 10/18/2022]
Abstract
Sulphobromophthalein (SBP) inhibits isolated glutathione S-transferase of the porcine nodule worm Oesophagostomum dentatum (Od-GST) and reduces larval development in vitro. In this study possible inhibitory effects of various inhibitors were evaluated in an enzymatic (CDNB) assay with isolated Od-GST and in a larval development assay (LDA). Reversibility was tested in the LDA by removing the inhibitor from culture halfway through the cultivation period. SBP, indomethacin and ethacrynic acid inhibited both enzyme activity and larval development in a dose-dependent and reversible manner. HQL-79 also reduced larval development but had only a minor effect on the isolated enzyme. The phospholipase A(2) inhibitors dexamethasone and hydrocortisone had no major effect. High thermal stability of Od-GST was demonstrated with increasing activity between 4 and 50°C. Differences between Od-GST and GST of other organisms indicate structural and possibly functional peculiarities and highlight the potential of such enzymes as targets of intervention.
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Affiliation(s)
- Anja Joachim
- Institute of Parasitology, Department of Pathobiology, University of Veterinary Medicine Vienna, Veterinaerplatz 1, A-1210 Vienna, Austria.
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Developing vaccines to combat hookworm infection and intestinal schistosomiasis. Nat Rev Microbiol 2010; 8:814-26. [PMID: 20948553 DOI: 10.1038/nrmicro2438] [Citation(s) in RCA: 208] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Hookworm infection and schistosomiasis rank among the most important health problems in developing countries. Both cause anaemia and malnutrition, and schistosomiasis also results in substantial intestinal, liver and genitourinary pathology. In sub-Saharan Africa and Brazil, co-infections with the hookworm, Necator americanus, and the intestinal schistosome, Schistosoma mansoni, are common. The development of vaccines for these infections could substantially reduce the global disability associated with these helminthiases. New genomic, proteomic, immunological and X-ray crystallographic data have led to the discovery of several promising candidate vaccine antigens. Here, we describe recent progress in this field and the rationale for vaccine development.
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