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Xu M, Liu P, Huang Q, Xu S, Dumont HJ, Han BP. High-quality genome of Diaphanosoma dubium provides insights into molecular basis of its broad ecological adaptation. iScience 2023; 26:106006. [PMID: 36798432 PMCID: PMC9926121 DOI: 10.1016/j.isci.2023.106006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 07/20/2022] [Accepted: 01/13/2023] [Indexed: 01/19/2023] Open
Abstract
Diaphanosoma dubium Manuilova, 1964, is a widespread planktonic water flea in Asian freshwater. Although sharing similar ecological roles with species of Daphnia, studies on D. dubium and its congeners are still few and lacking a genome for the further studies. Here, we assembled a high quality and chromosome level genome of D. dubium by combining long reads sequencing and Hi-C technologies. The total length of assembled genome was 101.8 Mb, with 98.92 Mb (97.2%) anchored into 22 chromosomes. Through comparative genomic analysis, we found the genes, involved in anti-ROS, detoxification, protein digestion, germ cells regulation and protection, underwent expansion in D. dubium. These genes and their expansion helpfully explain its widespread geographical distribution and dominance in eutrophic waters. This study provides insight into the adaptive evolution of D. dubium at genomic perspectives, and the present high quality genomic resource will be a footstone for future omics studies of the species and its congeners.
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Affiliation(s)
- Meng Xu
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou 510632, China
| | - Ping Liu
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou 510632, China,College of Environmental Science and Engineering, Yangzhou University, Yangzhou 225127, China
| | - Qi Huang
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou 510632, China
| | - Shaolin Xu
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou 510632, China
| | - Henri J. Dumont
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou 510632, China,Ghent University, Department of Biology, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Bo-Ping Han
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou 510632, China,Corresponding author
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Pritchard DI, Diemert D, Bottazzi ME, Hawdon JM, Correa-Oliveira R, Bethony JM. Controlled Infection of Humans with the Hookworm Parasite Necator americanus to Accelerate Vaccine Development : The Human Hookworm Vaccination/Challenge Model (HVCM). Curr Top Microbiol Immunol 2021. [PMID: 34328562 DOI: 10.1007/82_2021_237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
In this chapter, we describe the scientific, technical, clinical and regulatory aspects of establishing a controlled human hookworm infection (CHHI) model in non-endemic and endemic geographical regions, to facilitate a pathway towards accelerated vaccine development. The success achieved in establishing the CHHI platform specifically allows the Human Hookworm Vaccine Initiative (HHVI) to accelerate its progress by establishing a human hookworm vaccination/challenge model (HVCM) in a hookworm endemic area of Brazil. The HVCM will permit the rapid and robust determination of clinical efficacy in adults, allowing for early selection of the most efficacious human hookworm vaccine (HHV) candidate(s) to advance into later-stage pivotal paediatric clinical trials and reduce the overall number of participants required to assess efficacy (Diemert et al. 2018).
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Affiliation(s)
- David I Pritchard
- Parasite Immunology, University of Nottingham, Nottingham, UK.
- HIC-Vac, London, UK.
| | - David Diemert
- Department of Medicine, The George Washington University, Washington, DC, USA
| | - Maria Elena Bottazzi
- Department of Pediatrics, Section of Pediatric Tropical Medicine, Texas Children's Hospital Center for Vaccine Development, National School of Tropical Medicine, Baylor College of Medicine, Houston, TX, USA
| | - John M Hawdon
- Department of Microbiology, Immunology and Tropical Medicine, The George Washington University, Washington, DC, USA
| | | | - Jeffrey M Bethony
- Department of Microbiology, Immunology and Tropical Medicine, The George Washington University, Washington, DC, USA
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3
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Wang F, Chen Q, Zhang R, Li D, Ling Y, Song R. The anti-phytoalexin gene Bx-cathepsin W supports the survival of Bursaphelenchus xylophilus under Pinus massoniana phytoalexin stress. BMC Genomics 2019; 20:779. [PMID: 31655568 PMCID: PMC6815438 DOI: 10.1186/s12864-019-6167-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 10/02/2019] [Indexed: 11/10/2022] Open
Abstract
Background Pine trees challenged by Bursaphelenchus xylophilus invasion produce phytoalexins to combat this nematode. Nevertheless, the phytoalexins of Asian pine trees are ineffective against B. xylophilus. The anti-phytoalexin genes of B. xylophilus disable almost all Asian pine phytoalexins, which has allowed B. xylophilus to devastate pine forests in eastern Asia over the last four decades. However, to date, the factors that stimulate anti-phytoalexin gene expression and the mechanisms by which these genes act are not well understood. Results Here, we described anti-phytoalexin genes in B. xylophilus using transcriptomic and bioinformatics analyses. The genes that were induced by both Pinus massoniana and carvone and had similarly elevated expression trends were considered anti-phytoalexin genes. Altogether, 187 anti-phytoalexin genes were identified, including 4 cathepsin genes. KEGG pathway enrichment indicated that those cathepsins were related to the Lysosome pathway. Since cathepsins help to maintain metabolic homeostasis by participating in the degradation of heterophagic and autophagic material, the lysosomal cathepsin gene Bx-cathepsin W was cloned and characterized. The results of the RNAi assessment indicated that the knockdown of Bx-cathepsin W reduced the survival rates of B. xylophilus under carvone or P. massoniana stress. The correlation between Bx-cathepsin W and the susceptibility of pines showed that Bx-cathepsin W might help improve the anti-phytotoxin ability of B. xylophilus. Conclusions The results indicated that the anti-phytoalexin gene Bx-cathepsin W supported the survival of B. xylophilus under P. massoniana phytoalexin stress. The cDNA library sequencing, differentially expressed gene identification, and WGCNA algorithm analysis provided insight at a systemic level into the gene regulation of B. xylophilus in response to the immune reaction of P. massoniana. These results will lead to a better understanding of the function of nematode defenses in host innate immunity.
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Affiliation(s)
- Feng Wang
- Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education, School of Forestry, Northeast Forestry University, Harbin, 150040, Heilongjiang, People's Republic of China
| | - Qiaoli Chen
- Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education, School of Forestry, Northeast Forestry University, Harbin, 150040, Heilongjiang, People's Republic of China
| | - Ruizhi Zhang
- Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education, School of Forestry, Northeast Forestry University, Harbin, 150040, Heilongjiang, People's Republic of China
| | - Danlei Li
- Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education, School of Forestry, Northeast Forestry University, Harbin, 150040, Heilongjiang, People's Republic of China
| | - Yaming Ling
- Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education, School of Forestry, Northeast Forestry University, Harbin, 150040, Heilongjiang, People's Republic of China
| | - Ruiqing Song
- Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education, School of Forestry, Northeast Forestry University, Harbin, 150040, Heilongjiang, People's Republic of China.
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Molina-Fernández D, Benítez R, Adroher FJ, Malagón D. Differential proteolytic activity in Anisakis simplex s.s. and Anisakis pegreffii, two sibling species from the complex Anisakis simplex s.l., major etiological agents of anisakiasis. Acta Trop 2019; 195:44-50. [PMID: 30995435 DOI: 10.1016/j.actatropica.2019.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Revised: 04/02/2019] [Accepted: 04/02/2019] [Indexed: 11/18/2022]
Abstract
Proteolytic activity was studied in two sibling species of Anisakis (Nematoda: Anisakidae), A. simplex s.s. and A. pegreffii, throughout their in vitro development from third larval stage (L3) from the host fish (L3-0h) to fourth larval stage (L4) obtained in culture. Proteases have a significant role in the lifecycle of the parasite and in the pathogen-host relationship. Proteolytic activity peaks were detected at pH 6.0 and 8.5. Protease activity was detected in all the developmental stages of the two species studied at both pH values. These pH values were used for assaying with specific inhibitors which permitted the determination of metalloprotease activity, and, to a lesser extent, that of serine and cysteine protease. Aspartic protease activity was only detected at pH 6.0. At this pH, L4 larvae showed higher proteolytic activity than L3 larvae in both species (p < 0.001), the majority of activity being due to metalloproteases and aspartic proteases, which could be related to nutrition, especially the latter, as occurs in invertebrates. At pH 8.5, proteolytic activity was higher in A. simplex s.s. than in A. pegreffii (p < 0.01). At this pH, the majority of activity was due to metalloproteases in all developmental phases of both species, although, in L3-0h, the activity of these proteases was significantly higher (p < 0.03) in A. simplex s.s. than in A. pegreffii. This could be related to the greater invasive capacity of the former. Serine proteases have frequently been implicated in the invasive capacity and pathogenicity of some parasites. This may be related to the significantly higher activity (p ≤ 0.05) of serine protease in all the larval stages of A. simplex studied at pH 6.0. Thus, there are interspecific differences in proteases that have been related to pathogenesis in nematodes. These differences could thus be contributing to the previously reported differences in pathogenicity between these two Anisakis species.
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Affiliation(s)
- Dolores Molina-Fernández
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Granada, 18071 Granada, Spain
| | - Rocío Benítez
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Granada, 18071 Granada, Spain
| | - Francisco Javier Adroher
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Granada, 18071 Granada, Spain.
| | - David Malagón
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Granada, 18071 Granada, Spain
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Chauhan VM, Pritchard DI. Haematophagic Caenorhabditis elegans. Parasitology 2019; 146:314-320. [PMID: 30355366 PMCID: PMC6485396 DOI: 10.1017/s0031182018001518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Caenorhabditis elegans is a free-living nematode that resides in soil and typically feeds on bacteria. We postulate that haematophagic C. elegans could provide a model to evaluate vaccine responses to intestinal proteins from hematophagous nematode parasites, such as Necator americanus. Human erythrocytes, fluorescently labelled with tetramethylrhodamine succinimidyl ester, demonstrated a stable bright emission and facilitated visualization of feeding events with fluorescent microscopy. C. elegans were observed feeding on erythrocytes and were shown to rupture red blood cells upon capture to release and ingest their contents. In addition, C. elegans survived equally on a diet of erythrocytes. There was no statistically significant difference in survival when compared with a diet of Escherichia coli OP50. The enzymes responsible for the digestion and detoxification of haem and haemoglobin, which are key components of the hookworm vaccine, were found in the C. elegans intestine. These findings support our postulate that free-living nematodes could provide a model for the assessment of neutralizing antibodies to current and future hematophagous parasite vaccine candidates.
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Affiliation(s)
- Veeren M Chauhan
- School of Pharmacy, University of Nottingham, Boots Sciences Building, University Park, Nottingham, NG7 2RD, UK
| | - David I Pritchard
- School of Pharmacy, University of Nottingham, Boots Sciences Building, University Park, Nottingham, NG7 2RD, UK
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Goupil LS, Ivry SL, Hsieh I, Suzuki BM, Craik CS, O’Donoghue AJ, McKerrow JH. Cysteine and Aspartyl Proteases Contribute to Protein Digestion in the Gut of Freshwater Planaria. PLoS Negl Trop Dis 2016; 10:e0004893. [PMID: 27501047 PMCID: PMC4976874 DOI: 10.1371/journal.pntd.0004893] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 07/11/2016] [Indexed: 01/06/2023] Open
Abstract
Proteases perform numerous vital functions in flatworms, many of which are likely to be conserved throughout the phylum Platyhelminthes. Within this phylum are several parasitic worms that are often poorly characterized due to their complex life-cycles and lack of responsiveness to genetic manipulation. The flatworm Schmidtea mediterranea, or planaria, is an ideal model organism to study the complex role of protein digestion due to its simple life cycle and amenability to techniques like RNA interference (RNAi). In this study, we were interested in deconvoluting the digestive protease system that exists in the planarian gut. To do this, we developed an alcohol-induced regurgitation technique to enrich for the gut enzymes in S. mediterranea. Using a panel of fluorescent substrates, we show that this treatment produces a sharp increase in proteolytic activity. These enzymes have broad yet diverse substrate specificity profiles. Proteomic analysis of the gut contents revealed the presence of cysteine and metallo-proteases. However, treatment with class-specific inhibitors showed that aspartyl and cysteine proteases are responsible for the majority of protein digestion. Specific RNAi knockdown of the cathepsin B-like cysteine protease (SmedCB) reduced protein degradation in vivo. Immunohistochemistry and whole-mount in situ hybridization (WISH) confirmed that the full-length and active forms of SmedCB are found in secretory cells surrounding the planaria intestinal lumen. Finally, we show that the knockdown of SmedCB reduces the speed of tissue regeneration. Defining the roles of proteases in planaria can provide insight to functions of conserved proteases in parasitic flatworms, potentially uncovering drug targets in parasites.
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Affiliation(s)
- Louise S. Goupil
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States of America
| | - Sam L. Ivry
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States of America
| | - Ivy Hsieh
- Department of Pathology, University of California, San Francisco, San Francisco, California, United States of America
| | - Brian M. Suzuki
- Skaggs School of Pharmacy and Pharmaceutical Chemistry, University of California, San Diego, La Jolla, California, United States of America
| | - Charles S. Craik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States of America
| | - Anthony J. O’Donoghue
- Skaggs School of Pharmacy and Pharmaceutical Chemistry, University of California, San Diego, La Jolla, California, United States of America
| | - James H. McKerrow
- Skaggs School of Pharmacy and Pharmaceutical Chemistry, University of California, San Diego, La Jolla, California, United States of America
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7
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An antigenic recombinant serine protease from Trichinella spiralis induces protective immunity in BALB/c mice. Parasitol Res 2013; 112:3229-38. [PMID: 23828191 DOI: 10.1007/s00436-013-3500-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 06/11/2013] [Indexed: 10/26/2022]
Abstract
In this study, we report the cloning and characterization of a cDNA encoding a Trichinella serine protease gene (TspSP-1.3) from GenBank. The recombinant TspSP-1.3 protein (rTspSP-1.3) was expressed in an Escherichia coli expression system and purified with Ni-affinity chromatography. Real-time quantitative PCR analysis revealed that TspSP-1.3 was expressed at significantly higher levels in muscle larvae and adult worms than in newborn larvae. TspSP-1.3 was detected in excretory-secretory proteins of Trichinella spiralis with western blotting. Immunization with the rTspSP-1.3 antigen induced humoral immune responses, which manifested as elevated specific anti-rTspSP-1.3 IgG and IgE antibodies and a mixed Th1/Th2 response. To determine whether purified rTspSP-1.3 had good antigenicity and could be a vaccine candidate for the control of T. spiralis infection, we immunized BALB/c mice with rTspSP-1.3 and subsequently challenged the mice with T. spiralis larvae. The results showed that mice vaccinated with rTspSP-1.3 exhibited an average reduction in the muscle larvae burden of 39 % relative to the control group. These results suggest that TspSP-1.3 could be a novel vaccine candidate for controlling Trichinella infection.
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Rebello KM, Siqueira CRD, Ribeiro EL, Valente RH, Mota EM, Perales J, Neves-Ferreira AGDC, Lenzi HL. Proteolytic activity in the adult and larval stages of the human roundworm parasite Angiostrongylus costaricensis. Mem Inst Oswaldo Cruz 2013; 107:752-9. [PMID: 22990964 DOI: 10.1590/s0074-02762012000600008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 05/09/2012] [Indexed: 11/21/2022] Open
Abstract
Angiostrongylus costaricensis is a nematode that causes abdominal angiostrongyliasis, a widespread human parasitism in Latin America. This study aimed to characterize the protease profiles of different developmental stages of this helminth. First-stage larvae (L1) were obtained from the faeces of infected Sigmodon hispidus rodents and third-stage larvae (L3) were collected from mollusks Biomphalaria glabrata previously infected with L1. Adult worms were recovered from rodent mesenteric arteries. Protein extraction was performed after repeated freeze-thaw cycles followed by maceration of the nematodes in 40 mM Tris base. Proteolysis of gelatin was observed by zymography and found only in the larval stages. In L3, the gelatinolytic activity was effectively inhibited by orthophenanthroline, indicating the involvement of metalloproteases. The mechanistic class of the gelatinases from L1 could not be precisely determined using traditional class-specific inhibitors. Adult worm extracts were able to hydrolyze haemoglobin in solution, although no activity was observed by zymography. This haemoglobinolytic activity was ascribed to aspartic proteases following its effective inhibition by pepstatin, which also inhibited the haemoglobinolytic activity of L1 and L3 extracts. The characterization of protease expression throughout the A. costaricensis life cycle may reveal key factors influencing the process of parasitic infection and thus foster our understanding of the disease pathogenesis.
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9
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Malagón D, Benítez R, Adroher FJ, Díaz-López M. Proteolytic activity in Hysterothylacium aduncum (Nematoda: Anisakidae), a fish gastrointestinal parasite of worldwide distribution. Vet Parasitol 2011; 183:95-102. [PMID: 21802207 DOI: 10.1016/j.vetpar.2011.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 07/01/2011] [Accepted: 07/05/2011] [Indexed: 10/18/2022]
Abstract
Proteases have a significant role in the life cycle of parasites and the pathogen-host relationship, being regarded as important virulence factors. In the parasitic nematode Hysterothylacium aduncum proteolytic activity was measured during in vitro development from third larval stage (L3) to mature adult, using DQ red casein as a fluorogenic substrate. Proteolytic activity was detected in all the developmental stages studied and at all pH values within the range employed (2.0-7.5). The assay with specific inhibitors permitted the determination of metalloprotease activity, and, to a lesser extent, that of aspartate- and cysteine-protease. Serine-protease activity was the lowest of those studied. In L3 recently collected from the host fish (L3-0 h), the greatest activity was found at an optimum pH of 4.0 and was mainly inhibited by 1,10-phenathroline (metalloprotease inhibitor). This metalloprotease activity in L3-0 h (infective stage) may be related to the invasion of the host tissues by this larva. In the other developmental stages, the greatest protease activity was found at pH 5.5, although at pH 4.0 a lower activity peak was detected. On the other hand, our data show that the proteolytic activity of the nematode varies according to the presence of pepsin (an aspartic-protease) in the culture medium. Thus, at pH 4.0, activity was greater in the absence of pepsin, with increasing aspartic-protease activity. Together with the detection of aspartic-, cysteine- and metallo-protease (enzymes involved in digestion in invertebrates) in all the developmental stages of the parasite taking place in the digestive tract of the host fish, this allows us to suggest that the pepsin in the culture medium mimics the predigestion conditions in the habitat of the worm within the host and that the activity detected may have, amongst others, a digestive function.
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Affiliation(s)
- David Malagón
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Granada, 18071 Granada, Spain
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10
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Balasubramanian N, Toubarro D, Simões N. Biochemical study and in vitro insect immune suppression by a trypsin-like secreted protease from the nematode Steinernema carpocapsae. Parasite Immunol 2010; 32:165-75. [PMID: 20398179 DOI: 10.1111/j.1365-3024.2009.01172.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A trypsin-like serine protease was purified by gel filtration and anion-exchange chromatography from the excretory-secretory products of parasitic phase Steinernema carpocapsae. The purified protease exhibited a molecular mass of about 29 kDa by SDS-PAGE and displayed a pI of 6.3. This protease exhibited high activity with trypsin-specific substrate N-Ben-Phe-Val-Arg-p-nitroanilide and was highly sensitive to aprotinin and benzamidine. The purified trypsin protease digested the chromogenic substrate N-Ben-Phe-Val-Arg-p-nitroanilide with K(m), V(max) and k(cat) values of 594.2 mum, 0.496 mum/min and 22.8/s, respectively. The optimal pH and temperature for protease activity were 9 and 30 degrees C, respectively. Internal amino acid sequencing yielded 150 amino acids and these were homologous to other trypsin sequences. In vitro investigation was carried out to monitor prophenoloxidase suppression in Galleria mellonella by the purified protease; about 38.9-52.6% suppression of prophenoloxidase was observed. The purified protease affected insect haemocyte spreading, causing cells to become spherical or round. Protease-treated actin filaments were highly disorganized in haemocytes. In vitro, G. mellonella haemocytes recognized infective juveniles of Heterorhabditis bacteriophora; however, S. carpocapsae and Steinernema glaseri were not recognized. We provide experimental evidence that the purified trypsin has the potential to alter host haemocytes, actin filaments and to inhibit host haemolymph melanization.
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Affiliation(s)
- N Balasubramanian
- CIRN and Department of Biology, University of Azores, Ponta Delgada, Portugal.
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11
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Antigen-driven basophil activation is indicative of early Necator americanus infection in IgE-seronegative patients. J Allergy Clin Immunol 2009; 124:1343-50.e7. [DOI: 10.1016/j.jaci.2009.07.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Revised: 07/15/2009] [Accepted: 07/15/2009] [Indexed: 11/22/2022]
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12
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Balasubramanian N, Hao YJ, Toubarro D, Nascimento G, Simões N. Purification, biochemical and molecular analysis of a chymotrypsin protease with prophenoloxidase suppression activity from the entomopathogenic nematode Steinernema carpocapsae. Int J Parasitol 2009; 39:975-84. [PMID: 19249304 DOI: 10.1016/j.ijpara.2009.01.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 01/16/2009] [Accepted: 01/19/2009] [Indexed: 10/21/2022]
Abstract
A chymotrypsin serine protease (designated Sc-CHYM) was purified by gel filtration and anion-exchange chromatography from excretory-secretory products of parasitic stage Steinernema carpocapsae. The purified protease had an apparent molecular mass of 30kDa and displayed a pI of 5.9. This protease demonstrated high activity against the chymotrypsin-specific substrate N-Succinyl-Ala-Ala-Pro-Phe-p-nitroanilide and was highly sensitive to the inhibitor aprotinin. This protease digested the chromogenic substrate N-Succinyl-Ala-Ala-Pro-Phe-p-nitroanilide with K(m), V(max) and k(cat) values of 409microM/min, 0.389microM/min and 24.9s(-1), respectively. The protease was most active at pH 8.0 and 35 degrees C, and its proteolytic activity was almost completely reduced after incubation at 75 degrees C for 30min. In vitro, this enzyme suppressed prophenoloxidase activity. In vivo, demonstration of encapsulation and melanization by purified chymotrypsin imbibed beads showed it could prevent hemocyte encapsulation and melanization by 12 and 24h, respectively. Sequence comparison and evolutionary marker analysis showed that the putative protein was a chymotrypsin-like protease with potential degradative, developmental and fibrinolytic functions. Expression pattern analysis revealed that the gene expression of Sc-CHYM was up-regulated in the parasitic stage. Sc-CHYM was clustered with several insect chymotrypsins and formed an ancestral branch in the phylogenetic tree, suggesting that Sc-CHYM branched off at an early stage of cluster divergence. The results of this study suggest that Sc-CHYM is a new member of the chymotrypsin serine protease family and that it might act as a virulence factor in host-parasite interactions.
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Delcroix M, Sajid M, Caffrey CR, Lim KC, Dvorák J, Hsieh I, Bahgat M, Dissous C, McKerrow JH. A Multienzyme Network Functions in Intestinal Protein Digestion by a Platyhelminth Parasite. J Biol Chem 2006; 281:39316-29. [PMID: 17028179 DOI: 10.1074/jbc.m607128200] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteases frequently function not only as individual enzymes but also in cascades or networks. A notable evolutionary switch occurred in one such protease network that is involved in protein digestion in the intestine. In vertebrates, this is largely the work of trypsin family serine proteases, whereas in invertebrates, cysteine proteases of the papain family and aspartic proteases assume the role. Utilizing a combination of protease class-specific inhibitors and RNA interference, we deconvoluted such a network of major endopeptidases functioning in invertebrate intestinal protein digestion, using the parasitic helminth, Schistosoma mansoni as an experimental model. We show that initial degradation of host blood proteins is ordered, occasionally redundant, and substrate-specific. Although inhibition of parasite cathepsin D had a greater effect on primary cleavage of hemoglobin, inhibition of cathepsin B predominated in albumin degradation. Nevertheless, in both cases, inhibitor combinations were synergistic. An asparaginyl endopeptidase (legumain) also synergized with cathepsin B and L in protein digestion, either by zymogen activation or facilitating substrate cleavage. This protease network operates optimally in acidic pH compartments either in the gut lumen or in vacuoles of the intestinal lining cells. Defining the role of each of these major enzymes now provides a clearer understanding of the function of a complex protease network that is conserved throughout invertebrate evolution. It also provides insights into which of these proteases are logical targets for development of chemotherapy for schistosomiasis, a major global health problem.
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Affiliation(s)
- Melaine Delcroix
- Department of Pathology, Tropical Disease Research Unit and Sandler Center for Basic Research in Parasitic Diseases, University of California, San Francisco, California 94158, USA.
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Choi JH, Lee JH, Yu HS, Jeong HJ, Kim J, Hong YC, Kong HH, Chung DI. Molecular and biochemical characterization of hemoglobinase, a cysteine proteinase, in Paragonimus westermani. THE KOREAN JOURNAL OF PARASITOLOGY 2006; 44:187-96. [PMID: 16969056 PMCID: PMC2532661 DOI: 10.3347/kjp.2006.44.3.187] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The mammalian trematode Paragonimus westermani is a typical digenetic parasite, which can cause paragonimiasis in humans. Host tissues and blood cells are important sources of nutrients for development, growth and reproduction of P. westermani. In this study, a cDNA clone encoding a 47 kDa hemoglobinase of P. westermani was characterized by sequencing analysis, and its localization was investigated immunohistochemically. The phylogenetic tree prepared based on the hemoglobinase gene showed high homology with hemoglobinases of Fasciola hepatica and Schistosoma spp. Moreover, recombinant P. westermani hemoglobinase degradaded human hemoglobin at acidic pH (from 3.0 to 5.5) and its activity was almost completely inhibited by E-64, a cysteine proteinase inhibitor. Immunohistochemical studies showed that P. westermani hemoglobinase was localized in the epithelium of the adult worm intestine implying that the protein has a specific function. These observations suggest that hemoglobinase may act as a digestive enzyme for acquisition of nutrients from host hemoglobin. Further investigations may provide insights into hemoglobin catabolism in P. westermani.
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Affiliation(s)
- Joon-Hyuck Choi
- Department of Parasitology, Kyungpook National University School of Medicine, Daegu, Korea
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15
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Williamson AL, Lecchi P, Turk BE, Choe Y, Hotez PJ, McKerrow JH, Cantley LC, Sajid M, Craik CS, Loukas A. A Multi-enzyme Cascade of Hemoglobin Proteolysis in the Intestine of Blood-feeding Hookworms. J Biol Chem 2004; 279:35950-7. [PMID: 15199048 DOI: 10.1074/jbc.m405842200] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Blood-feeding pathogens digest hemoglobin (Hb) as a source of nutrition, but little is known about this process in multicellular parasites. The intestinal brush border membrane of the canine hookworm, Ancylostoma caninum, contains aspartic proteases (APR-1), cysteine proteases (CP-2), and metalloproteases (MEP-1), the first of which is known to digest Hb. We now show that Hb is degraded by a multi-enzyme, synergistic cascade of proteolysis. Recombinant APR-1 and CP-2, but not MEP-1, digested native Hb and denatured globin. MEP-1, however, did cleave globin fragments that had undergone prior digestion by APR-1 and CP-2. Proteolytic cleavage sites within the Hb alpha and beta chains were determined for the three enzymes, identifying a total of 131 cleavage sites. By scanning synthetic combinatorial peptide libraries with each enzyme, we compared the preferred residues cleaved in the libraries with the known cleavage sites within Hb. The semi-ordered pathway of Hb digestion described here is surprisingly similar to that used by Plasmodium to digest Hb and provides a potential mechanism by which these hemoglobinases are efficacious vaccines in animal models of hookworm infection.
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Affiliation(s)
- Angela L Williamson
- Department of Microbiology and Tropical Medicine, The George Washington University, Washington, DC 20037, USA
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16
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Williamson AL, Brindley PJ, Knox DP, Hotez PJ, Loukas A. Digestive proteases of blood-feeding nematodes. Trends Parasitol 2003; 19:417-23. [PMID: 12957519 DOI: 10.1016/s1471-4922(03)00189-2] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Blood-feeding parasites employ a battery of proteolytic enzymes to digest the contents of their bloodmeal. Host haemoglobin is a major substrate for these proteases and, therefore, a driving force in the evolution of parasite-derived proteolytic enzymes. This review will focus on the digestive proteases of the major blood-feeding nematodes - hookworms (Ancylostoma spp. and Necator americanus) and the ruminant parasite, Haemonchus contortus - but also compares and contrasts these proteases with recent findings from schistosomes and malaria parasites. Haematophagous nematodes express proteases of different mechanistic classes in their intestines, many of which have proven or putative roles in degradation of haemoglobin and other proteins involved in nutrition. Moreover, the fine specificity of the relationships between digestive proteases and their substrate proteins provides a new molecular paradigm for understanding host-parasite co-evolution. Numerous laboratories are actively investigating these molecules as antiparasite vaccine targets.
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Affiliation(s)
- Angela L Williamson
- Department of Microbiology and Tropical Medicine, George Washington University Medical Center, Washington DC 20037, USA
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17
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Phillips C, Coward WR, Pritchard DI, Hewitt CRA. Basophils express a type 2 cytokine profile on exposure to proteases from helminths and house dust mites. J Leukoc Biol 2003; 73:165-71. [PMID: 12525574 DOI: 10.1189/jlb.0702356] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The proteolytic activities frequently associated with sources of allergens and parasite secretions have been suggested as important immunomodulators. We have investigated whether the protease activity of the house dust mite allergen Der p1 and the secreted proteases of the hookworm Necator americanus are able to directly induce type 2 cytokine production by basophils. Der p1 and the secretions of N. americanus induced interleukin (IL)-4, IL-5, and IL-13 but not interferon-gamma mRNA in KU812 basophils. Enzyme-linked immunosorbent assay confirmed that IL-4 and IL-13 were secreted. A nonproteolytic antigen failed to induce cytokine expression, and preincubation of Der p1 or N. americanus secretions with protease inhibitors inhibited cytokine expression. Data were confirmed using basophils purified from human peripheral blood. We speculate that this innate mechanism may contribute to the development of a cytokine milieu that could promote immunoglobulin E synthesis, eosinophil recruitment, and the development of type 2 T cells.
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Affiliation(s)
- Clair Phillips
- Department of Microbiology and Immunology, Institute for Lung Health, University of Leicester, University Road, Leicester LE1 9HN, United Kingdom
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18
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Lecaille F, Kaleta J, Brömme D. Human and parasitic papain-like cysteine proteases: their role in physiology and pathology and recent developments in inhibitor design. Chem Rev 2002; 102:4459-88. [PMID: 12475197 DOI: 10.1021/cr0101656] [Citation(s) in RCA: 393] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fabien Lecaille
- Mount Sinai School of Medicine, Department of Human Genetics, Fifth Avenue at 100th Street, New York, New York 10029, USA
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19
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Abstract
Hookworms infect perhaps one-fifth of the entire human population, yet little is known about their interaction with our immune system. The two major species are Necator americanus, which is adapted to tropical conditions, and Ancylostoma duodenale, which predominates in more temperate zones. While having many common features, they also differ in several key aspects of their biology. Host immune responses are triggered by larval invasion of the skin, larval migration through the circulation and lungs, and worm establishment in the intestine, where adult worms feed on blood and mucosa while injecting various molecules that facilitate feeding and modulate host protective responses. Despite repeated exposure, protective immunity does not seem to develop in humans, so that infections occur in all age groups (depending on exposure patterns) and tend to be prolonged. Responses to both larval and adult worms have a characteristic T-helper type 2 profile, with activated mast cells in the gut mucosa, elevated levels of circulating immunoglobulin E, and eosinophilia in the peripheral blood and local tissues, features also characteristic of type I hypersensitivity reactions. The longevity of adult hookworms is determined probably more by parasite genetics than by host immunity. However, many of the proteins released by the parasites seem to have immunomodulatory activity, presumably for self-protection. Advances in molecular biotechnology enable the identification and characterization of increasing numbers of these parasite molecules and should enhance our detailed understanding of the protective and pathogenetic mechanisms in hookworm infections.
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Affiliation(s)
- A Loukas
- Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, Brisbane, QLD 4006, Australia.
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Ali F, Brown A, Stanssens P, Timothy LM, Soule HR, Pritchard DI. Vaccination with neutrophil inhibitory factor reduces the fecundity of the hookworm Ancylostoma ceylanicum. Parasite Immunol 2001; 23:237-49. [PMID: 11309134 DOI: 10.1046/j.1365-3024.2001.00383.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neutrophil inhibitory factor (NIF), a protein isolated from hookworms of the genus Ancylostoma, inhibits CD11b/18-dependent leucocyte function, binding to the I domain of CD11b. Historically, NIF was serendipitously isolated from whole worm extracts during a search for novel antihaemostatic agents, and little is known of its source or biological significance to the parasite. NIF has also been identified as a possible hookworm vaccine candidate. Ancylostoma ceylanicum recombinant NIF, expressed in its active form in Pichia pastoris, was purified and its functional activity confirmed using neutrophil adhesion assays and confirmatory immunoassay. Recombinant NIF was subsequently used in vaccination trials in the A. ceylanicum-hamster model system for human hookworm infection. Vaccinated and challenged animals were not protected in terms of worm burden or haematocrit values, despite the presence of high levels of specific antibody against NIF. However, adult worms resident in vaccinated animals showed a significant reduction in fecundity (85.8% by day 21 postinfection), indicating a degree of protection against subsequent transmission by vaccination. These data indicate that targeted vaccination with recombinant subunit material, derived from a known and effective immune suppressant secreted by the parasite, may offer partial protection against the transmission of hookworm infection. Furthermore, we can also report that a biological activity characteristic of NIF is detectable in the secretions of A. ceylanicum using two complementary bioassays. Complete neutralization of this secreted activity by vaccination in combination with other vaccine candidates may result in improved protection against A. ceylanicum infection.
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Affiliation(s)
- F Ali
- The Boots Science Institute, University of Nottingham, University Park, Nottingham NG7 2RD, UK
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21
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Pritchard DI, Brown A. Is Necator americanus approaching a mutualistic symbiotic relationship with humans? Trends Parasitol 2001; 17:169-72. [PMID: 11282505 DOI: 10.1016/s1471-4922(01)01941-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The hookworm Necator americanus establishes infections of impressive longevity in the immunologically hostile environment of its human host. In the process, it promotes pronounced T-helper 2 (Th2) cell activity, which in turn seemingly affords the host at least a degree of protection. Given the relatively asymptomatic nature of infection, we argue here that Necator americanus might be approaching a mutualistic symbiotic relationship with humans. In our view, infection is controlled by the immune system while being supported by a subtle immune-evasion strategy that is tolerated and possibly beneficial to the host in certain immunological circumstances, such as in counterbalancing potentially damaging Th1 responses.
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Affiliation(s)
- D I Pritchard
- Boots Science Institute, School of Pharmaceutical Sciences, University of Nottingham, University Park, NG7 2RD, Nottingham, UK.
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Culley FJ, Brown A, Conroy DM, Sabroe I, Pritchard DI, Williams TJ. Eotaxin is specifically cleaved by hookworm metalloproteases preventing its action in vitro and in vivo. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:6447-53. [PMID: 11086084 DOI: 10.4049/jimmunol.165.11.6447] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Eotaxin is a potent eosinophil chemoattractant that acts selectively through CCR3, which is expressed on eosinophils, basophils, mast cells, and Th2-type T cells. This arm of the immune system is believed to have evolved to control helminthic parasites. We hypothesized that helminths may employ mechanisms to inhibit eosinophil recruitment, to prolong worm survival in the host. We observed that the excretory/secretory products of the hookworm Necator americanus inhibited eosinophil recruitment in vivo in response to eotaxin, but not leukotriene B(4), a phenomenon that could be prevented by the addition of protease inhibitors. Using Western blotting, N. americanus supernatant was shown to cause rapid proteolysis of eotaxin, but not IL-8 or eotaxin-2. N. americanus homogenate was fractionated by gel filtration chromatography, and a FACS-based bioassay measured the ability of each fraction to inhibit the activity of a variety of chemokines. This resulted in two peaks of eotaxin-degrading activity, corresponding to approximately 15 and 50 kDa molecular mass. This activity was specific for eotaxin, as responses to other agonists tested were unaffected. Proteolysis of eotaxin was prevented by EDTA and phenanthroline, indicating that metalloprotease activity was involved. Production of enzymes inactivating eotaxin may be a strategy employed by helminths to prevent recruitment and activation of eosinophils at the site of infection. As such this represents a novel mechanism of regulation of chemokine function in vivo. The existence of CCR3 ligands other than eotaxin (e.g., eotaxin-2) may reflect the evolution of host counter measures to parasite defense systems.
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Affiliation(s)
- F J Culley
- Leukocyte Biology Section, Biomedical Sciences Division, Imperial College School of Medicine, South Kensington, London, United Kingdom.
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23
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Hotez PJ. Pediatric geohelminth infections: Trichuriasis, ascariasis, and hookworm infections. ACTA ACUST UNITED AC 2000. [DOI: 10.1053/spid.2000.9637] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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24
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Taiwo FA, Brophy PM, Pritchard DI, Brown A, Wardlaw A, Patterson LH. Cu/Zn superoxide dismutase in excretory-secretory products of the human hookworm Necator americanus. An electron paramagnetic spectrometry study. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 264:434-8. [PMID: 10491088 DOI: 10.1046/j.1432-1327.1999.00626.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
EPR spectrometry was used to investigate the effect of excretory/secretory product from Necator americanus on superoxide radical anions generated by xanthine/xanthine oxidase as a measure of excretory/secretory product superoxide dismutase activity. Using 1,1',5,5'-dimethylpyrollidine-N-oxide (DMPO) as a superoxide spin-trapping agent a 12-line EPR spectrum characteristic of the DMPO-OOH adduct was observed to decrease in the presence of excretory/secretory product. Superoxide dismutase activity was proportional to excretory/secretory protein concentration, was inhibited with cyanide treatment and was progressively destroyed with increasing time of heat denaturation of excretory/secretory product. Using a purpose-built chamber the superoxide dismutase activity of excretory/secretory product from live worms in culture was shown to accumulate with time to a maximum at 4 h. The electron paramagnetic resonance spectrum obtained for the frozen excretory/secretory product of N. americanus recorded at 77 K is typical of Cu(II) in a protein matrix. The results are consistent with the presence of an active Cu/Zn superoxide dismutase in excretory/secretory product from N. americanus and demonstrate a method for the unequivocal determination of the fate of superoxide anions in the presence of live worms.
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Affiliation(s)
- F A Taiwo
- School of Pharmacy, De Montfort University, Leicester, UK.
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25
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Abstract
Parasitic infection is highly allergenic, and the present paper illustrates how parasites might disrupt the regulation of IgE synthesis, resulting in heightened Th-2 responses. The study of parasites, and dysregulation of the IgE network, could in turn provide information relating to the aetiology of allergic diseases such as asthma and atopic dermatitis.
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26
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Lilley CJ, Urwin PE, Atkinson HJ, McPherson MJ. Characterization of cDNAs encoding serine proteinases from the soybean cyst nematode Heterodera glycines. Mol Biochem Parasitol 1997; 89:195-207. [PMID: 9364965 DOI: 10.1016/s0166-6851(97)00116-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Three cDNAs encoding serine proteinases (HGSPI-III) were isolated from a cDNA library constructed from feeding females of Heterodera glycines. The library was screened with three separate serine proteinase gene fragments amplified from cDNA of H. glycines using consensus oligonucleotide primers. Each predicted protein contains a secretion signal sequence, a propeptide and a mature protein of 226-296 amino acids. One of the predicted enzymes, HGSP-II has 41% identity to a chymotrypsin-like enzyme from the mollusc, Haliotis rufescens, and analysis of key residues involved in substrate binding also suggests a chymotrypsin-like specificity. HGSP-I and HGSP-III show greatest homology to kallikreins but sequence analysis does not allow prediction of their substrate preferences. Southern blot analysis suggests that HGSP-II and HGSP-III are encoded by single-copy genes in contrast to HGSP-I which may have two or more homologues. The regions encoding the mature proteinases were cloned into an expression vector and recombinant protein produced in Escherichia coli. Both HGSP-I and HGSP-II were shown, after refolding, to cleave the synthetic peptide N-CBZ-Phe-Arg-7-amido-4-methylcoumarin, and this activity could be inhibited by the cowpea trypsin inhibitor, CpTI. HGSP-III showed no activity against the synthetic substrates tested. The information gained from these studies indicates that serine proteinases are an important group of enzymes in H. glycines and further characterization will aid the development of a proteinase inhibitor-based approach for transgenic plant resistance to plant parasitic nematodes.
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Affiliation(s)
- C J Lilley
- Centre for Plant Biochemistry and Biotechnology, University of Leeds, UK
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28
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Hotez PJ, Hawdon JM, Cappello M, Jones BF, Ghosh K, Volvovitz F, Xiao SH. Molecular approaches to vaccinating against hookworm disease. Pediatr Res 1996; 40:515-21. [PMID: 8888276 DOI: 10.1203/00006450-199610000-00001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Anthelminthic drug chemotherapy has failed as an acceptable approach to hookworm control in the less developed countries of the tropics. The development of a genetically engineered vaccine against hookworm infection would be a major advance in our efforts to control this parasitic disease. We have produced several lead recombinant hookworm vaccine antigens. Their development is based on scientific principles that were generated almost 70 years ago when investigators first began to attenuate living infective hookworm larvae. Those early studies on attenuated live vaccines highlighted the importance of secreted larval antigens for eliciting protective immunity in dogs challenged with Ancylostoma caninum. The two major secreted larval antigens have been recently identified as Ancylostoma secreted protein-1 (ASP-1) and ASP-2. The predicted amino acid sequences of the ASP cDNAs together with experimental immunogenicty data using the expressed recombinant protein suggest that the ASPs are promising vaccine antigens. Preliminary hookworm challenge data in mice immunized with recombinant ASP-1 helps to validate this assumption. Alternative vaccines based on either genetic immunization (DNA vaccines) or immunization with recombinant molecules expressed from adult hookworm cDNAs are also under evaluation. Optimization of vaccine route, delivery system, and adjuvant formulations will be required before future planned phase I testing in humans. Vaccine development for a target population living in rural areas of less developed countries will require innovative solutions to financing and manufacture.
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Affiliation(s)
- P J Hotez
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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