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Das KC, Konhar R, Biswal DK. Fasciola gigantica vaccine construct: an in silico approach towards identification and design of a multi-epitope subunit vaccine using calcium binding EF-hand proteins. BMC Immunol 2023; 24:1. [PMID: 36604615 PMCID: PMC9813462 DOI: 10.1186/s12865-022-00535-y] [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: 04/10/2022] [Accepted: 12/21/2022] [Indexed: 01/07/2023] Open
Abstract
Continuous attempts have been made to pinpoint candidate vaccine molecules and evaluate their effectiveness in order to commercialise such vaccines for the treatment of tropical fascioliasis in livestock. The pathophysiology of fascioliasis can be related to liver damage brought on by immature flukes that migrate and feed, as well as immunological reactions to chemicals produced by the parasites and alarm signals brought on by tissue damage. Future research should, in our opinion, concentrate on the biology of invasive parasites and the resulting immune responses, particularly in the early stages of infection. The goal of the current study was to use the calcium-binding proteins from F. gigantica to create a multi-epitope subunit vaccine. The adjuvant, B-cell epitopes, CTL epitopes, and HTL epitopes that make up the vaccine construct are all connected by certain linkers. The antigenicity, allergenicity, and physiochemical properties of the vaccine construct were examined. The vaccine construct was docked with toll-like receptor 2, and simulations of the molecular dynamics of the complex's stability, interaction, and dynamics were run. After performing in silico cloning and immunosimulation, it was discovered that the construct was suitable for further investigation. New vaccination technologies and adjuvant development are advancing our food safety procedures since vaccines are seen as safe and are accepted by the user community. This research is also applicable to the F. hepatica system.
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Affiliation(s)
- Kanhu Charan Das
- grid.412227.00000 0001 2173 057XBioinformatics Centre, North-Eastern Hill University, Shillong, Meghalaya India
| | - Ruchishree Konhar
- grid.412227.00000 0001 2173 057XBioinformatics Centre, North-Eastern Hill University, Shillong, Meghalaya India ,grid.417639.eInformatics and Big Data, CSIR-Institute of Genomics and Integrative Biology, Delhi, India
| | - Devendra Kumar Biswal
- grid.412227.00000 0001 2173 057XBioinformatics Centre, North-Eastern Hill University, Shillong, Meghalaya India
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2
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A mysterious family of calcium-binding proteins from parasitic worms. Biochem Soc Trans 2017; 44:1005-10. [PMID: 27528745 DOI: 10.1042/bst20150270] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Indexed: 12/23/2022]
Abstract
There is a family of proteins from parasitic worms which combine N-terminal EF-hand domains with C-terminal dynein light chain-like domains. Data are accumulating on the biochemistry and cell biology of these proteins. However, little is known about their functions in vivo Schistosoma mansoni expresses 13 family members (SmTAL1-SmTAL13). Three of these (SmTAL1, SmTAL2 and SmTAL3) have been subjected to biochemical analysis which demonstrated that they have different molecular properties. Although their overall folds are predicted to be similar, small changes in the EF-hand domains result in differences in their ion binding properties. Whereas SmTAL1 and SmTAL2 are able to bind calcium (and some other) ions, SmTAL3 appears to be unable to bind any divalent cations. Similar biochemical diversity has been seen in the CaBP proteins from Fasciola hepatica Four family members are known (FhCaBP1-4). All of these bind to calcium ions. However, FhCaBP4 dimerizes in the presence of calcium ions, FhCaBP3 dimerizes in the absence of calcium ions and FhCaBP2 dimerizes regardless of the prevailing calcium ion concentration. In both the SmTAL and FhCaBP families, the proteins also differ in their ability to bind calmodulin antagonists and related drugs. Interestingly, SmTAL1 interacts with praziquantel (the drug of choice for treating schistosomiasis). The pharmacological significance (if any) of this finding is unknown.
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3
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Tsoneva D, Minev B, Frentzen A, Zhang Q, Wege AK, Szalay AA. Humanized Mice with Subcutaneous Human Solid Tumors for Immune Response Analysis of Vaccinia Virus-Mediated Oncolysis. MOLECULAR THERAPY-ONCOLYTICS 2017; 5:41-61. [PMID: 28480327 PMCID: PMC5415323 DOI: 10.1016/j.omto.2017.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 03/02/2017] [Indexed: 12/20/2022]
Abstract
Oncolytic vaccinia virus (VACV) therapy is an alternative cancer treatment modality that mediates targeted tumor destruction through a tumor-selective replication and an induction of anti-tumor immunity. We developed a humanized tumor mouse model with subcutaneous human tumors to analyze the interactions of VACV with the developing tumors and human immune system. A successful systemic reconstitution with human immune cells including functional T cells as well as development of tumors infiltrated with human T and natural killer (NK) cells was observed. We also demonstrated successful in vivo colonization of such tumors with systemically administered VACVs. Further, a new recombinant GLV-1h376 VACV encoding for a secreted human CTLA4-blocking single-chain antibody (CTLA4 scAb) was tested. Surprisingly, although proving CTLA4 scAb's in vitro binding ability and functionality in cell culture, beside the significant increase of CD56bright NK cell subset, GLV-1h376 was not able to increase cytotoxic T or overall NK cell levels at the tumor site. Importantly, the virus-encoded β-glucuronidase as a measure of viral titer and CTLA4 scAb amount was demonstrated. Therefore, studies in our "patient-like" humanized tumor mouse model allow the exploration of newly designed therapy strategies considering the complex relationships between the developing tumor, the oncolytic virus, and the human immune system.
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Affiliation(s)
- Desislava Tsoneva
- Department of Biochemistry, Biocenter, University of Wuerzburg, 97074 Wuerzburg, Germany
| | - Boris Minev
- Department of Radiation Medicine and Applied Sciences, Rebecca & John Moores Comprehensive Cancer Center, University of California, San Diego, CA 92093, USA.,Genelux Corporation, San Diego Science Center, San Diego, CA 92109, USA
| | - Alexa Frentzen
- Genelux Corporation, San Diego Science Center, San Diego, CA 92109, USA
| | - Qian Zhang
- Genelux Corporation, San Diego Science Center, San Diego, CA 92109, USA
| | - Anja K Wege
- Department of Gynecology and Obstetrics, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Aladar A Szalay
- Department of Biochemistry, Biocenter, University of Wuerzburg, 97074 Wuerzburg, Germany.,Department of Radiation Medicine and Applied Sciences, Rebecca & John Moores Comprehensive Cancer Center, University of California, San Diego, CA 92093, USA.,Genelux Corporation, San Diego Science Center, San Diego, CA 92109, USA.,Rudolph Virchow Center for Experimental Biomedicine, University of Wuerzburg, 97080 Wuerzburg, Germany
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Cheung S, Thomas CM, Timson DJ. FhCaBP1 (FH22): A Fasciola hepatica calcium-binding protein with EF-hand and dynein light chain domains. Exp Parasitol 2016; 170:109-115. [PMID: 27693219 DOI: 10.1016/j.exppara.2016.09.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/21/2016] [Accepted: 09/27/2016] [Indexed: 11/18/2022]
Abstract
FH22 has been previously identified as a calcium-binding protein from the common liver fluke, Fasciola hepatica. It is part of a family of at least four proteins in this organism which combine an EF-hand containing N-terminal domain with a C-terminal dynein light chain-like domain. Here we report further biochemical properties of FH22, which we propose should be renamed FhCaBP1 for consistency with other family members. Molecular modelling predicted that the two domains are linked by a flexible region and that the second EF-hand in the N-terminal domain is most likely the calcium ion binding site. Native gel electrophoresis demonstrated that the protein binds both calcium and manganese ions, but not cadmium, magnesium, strontium, barium, cobalt, copper(II), iron (II), nickel, zinc, lead or potassium ions. Calcium ion binding alters the conformation of the protein and increases its stability towards thermal denaturation. FhCaBP1 is a dimer in solution and calcium ions have no detectable effect on the protein's ability to dimerise. FhCaBP1 binds to the calmodulin antagonists trifluoperazine and chlorpromazine. Overall, the FhCaBP1's biochemical properties are most similar to FhCaBP2 a fact consistent with the close sequence and predicted structural similarity between the two proteins.
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Affiliation(s)
- Sarah Cheung
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK
| | - Charlotte M Thomas
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK; Institute for Global Food Security, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, UK
| | - David J Timson
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK; School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Lewes Road, Brighton, BN2 4GJ, UK.
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5
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Tewari AK, Kurup SP, Baidya S, Barta JR, Sharma B. Protective antibody and cytokine responses in mice following immunization with recombinant beta-tubulin and subsequent Trypanosoma evansi challenge. Parasit Vectors 2015; 8:580. [PMID: 26566996 PMCID: PMC4644280 DOI: 10.1186/s13071-015-1189-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 10/30/2015] [Indexed: 11/24/2022] Open
Abstract
Background Trypanosomosis or Surra, caused by the flagellated hemoprotozoan parasite Trypanosoma evansi, is a disease of economic importance through its wide prevalence in domestic livestock in tropical countries. In the absence of a protective vaccine, management of the disease relies on a few available chemotherapeutic agents. Although humoral immunity is the mainstay of resistance to T. evansi, the ability of the parasite to vary its immunodominant surface proteins to subvert the immune system has forced vaccine efforts to target a variety of invariant epitopes. Beta tubulin, an integral component of the trypanosome cytoskeleton, was therefore targeted using the recombinant form of the protein for immunization. Methods The 1329 bp coding sequence of beta tubulin gene was PCR amplified and cloned in pQE-TriSystem expression vector. Recombinant beta tubulin was heterologously expressed in Escherichia coli as a 46 KDa fusion protein and used for immunization of mice. The Ig response was studied by ELISA, whereas the cytokine response was measured using a cytometric bead-based assay quantified by flow cytometry. Result Immunization with recombinant beta (β)-tubulin protein induced a beta-tubulin specific humoral immune response of predominantly IgG2a isotype. Lethal challenge with T. evansi blood-form trypomastigotes post-immunization elicited a robust anamnestic response. An abundance of IFN-γ further confirmed the Th-1 bias of the protective response. We also observed extended survival and better control of the challenge infection in the immunized mice. Conclusions A robust anamnestic response following challenge including a Th-1 serum cytokine profile coupled with increased survival is indicative of protective immunity in the immunized mice. These observations suggest that β-tubulin of T. evansi is a viable antigenic target for development of a vaccine against this important livestock pathogen.
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Affiliation(s)
- Anup Kumar Tewari
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, N1G 2W1, Canada. .,Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh, 243 122, India.
| | - Samarchith P Kurup
- Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh, 243 122, India. .,Department of Microbiology, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA.
| | - Surajit Baidya
- Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh, 243 122, India. .,Department of Parasitology, West Bengal University of Animal and Fishery Sciences, 37 & 68, Kshudiram Bose Sarani, Belgachia, Kolkata, West Bengal, 700037, India.
| | - John R Barta
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, N1G 2W1, Canada.
| | - Bhaskar Sharma
- Division of Animal Biochemistry, Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh, 243 122, India.
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FhCaBP2: a Fasciola hepatica calcium-binding protein with EF-hand and dynein light chain domains. Parasitology 2015; 142:1375-86. [DOI: 10.1017/s0031182015000736] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
SUMMARYFhCaBP2 is a Fasciola hepatica protein which belongs to a family of helminth calcium-binding proteins which combine an N-terminal domain containing two EF-hand motifs and a C-terminal dynein light chain-like (DLC-like) domain. Its predicted structure showed two globular domains joined by a flexible linker. Recombinant FhCaBP2 interacted reversibly with calcium and manganese ions, but not with magnesium, barium, strontium, copper (II), colbalt (II), iron (II), nickel, lead or potassium ions. Cadmium (II) ions appeared to bind non-site-specifically and destabilize the protein. Interaction with either calcium or magnesium ions results in a conformational change in which the protein's surface becomes more hydrophobic. The EF-hand domain alone was able to interact with calcium and manganese ions; the DLC-like domain was not. Alteration of a residue (Asp-58 to Ala) in the second EF-hand motif in this domain abolished ion-binding activity. This suggests that the second EF-hand is the one responsible for ion-binding. FhCaBP2 homodimerizes and the extent of dimerization was not affected by calcium ions or by the aspartate to alanine substitution in the second EF-hand. The isolated EF-hand and DLC-like domains are both capable of homodimerization. FhCaBP2 interacted with the calmodulin antagonists trifluoperazine, chlorpromazine, thiamylal and W7. Interestingly, while chlorpromazine and thiamylal interacted with the EF-hand domain (as expected), trifluoperazine and W7 bound to the DLC-like domain. Overall, FhCaBP2 has distinct biochemical properties compared with other members of this protein family from Fasciola hepatica, a fact which supports the hypothesis that these proteins have different physiological roles.
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Specific humoral response of hosts with variable schistosomiasis susceptibility. Immunol Cell Biol 2015; 94:52-65. [PMID: 26044065 DOI: 10.1038/icb.2015.61] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 05/11/2015] [Accepted: 05/29/2015] [Indexed: 01/08/2023]
Abstract
The schistosome blood flukes are some of the largest global causes of parasitic morbidity. Further study of the specific antibody response during schistosomiasis may yield the vaccines and diagnostics needed to combat this disease. Therefore, for the purposes of antigen discovery, sera and antibody-secreting cell (ASC) probes from semi-permissive rats and sera from susceptible mice were used to screen a schistosome protein microarray. Following Schistosoma japonicum infection, rats had reduced pathology, increased antibody responses and broader antigen recognition profiles compared with mice. With successive infections, rat global serological reactivity and the number of recognized antigens increased. The local antibody response in rat skin and lung, measured with ASC probes, increased after parasite migration and contributed antigen-specific antibodies to the multivalent serological response. In addition, the temporal variation of anti-parasite serum antibodies after infection and reinfection followed patterns that appear related to the antigen driving the response. Among the 29 antigens differentially recognized by the infected hosts were numerous known vaccine candidates, drug targets and several S. japonicum homologs of human schistosomiasis resistance markers-the tegument allergen-like proteins. From this set, we prioritized eight proteins that may prove to be novel schistosome vaccine and diagnostic antigens.
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Thomas CM, Fitzsimmons CM, Dunne DW, Timson DJ. Comparative biochemical analysis of three members of the Schistosoma mansoni TAL family: Differences in ion and drug binding properties. Biochimie 2014; 108:40-7. [PMID: 25447146 PMCID: PMC4300400 DOI: 10.1016/j.biochi.2014.10.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 10/21/2014] [Indexed: 01/03/2023]
Abstract
The tegumental allergen-like (TAL) proteins from Schistosoma mansoni are part of a family of calcium binding proteins found only in parasitic flatworms. These proteins have attracted interest as potential drug or vaccine targets, yet comparatively little is known about their biochemistry. Here, we compared the biochemical properties of three members of this family: SmTAL1 (Sm22.6), SmTAL2 (Sm21.7) and SmTAL3 (Sm20.8). Molecular modelling suggested that, despite similarities in domain organisation, there are differences in the three proteins’ structures. SmTAL1 was predicted to have two functional calcium binding sites and SmTAL2 was predicted to have one. Despite the presence of two EF-hand-like structures in SmTAL3, neither was predicted to be functional. These predictions were confirmed by native gel electrophoresis, intrinsic fluorescence and differential scanning fluorimetry: both SmTAL1 and SmTAL2 are able to bind calcium ions reversibly, but SmTAL3 is not. SmTAL1 is also able to interact with manganese, strontium, iron(II) and nickel ions. SmTAL2 has a different ion binding profile interacting with cadmium, manganese, magnesium, strontium and barium ions in addition to calcium. All three proteins form dimers and, in contrast to some Fasciola hepatica proteins from the same family; dimerization is not affected by calcium ions. SmTAL1 interacts with the anti-schistosomal drug praziquantel and the calmodulin antagonists trifluoperazine, chlorpromazine and W7. SmTAL2 interacts only with W7. SmTAL3 interacts with the aforementioned calmodulin antagonists and thiamylal, but not praziquantel. Overall, these data suggest that the proteins have different biochemical properties and thus, most likely, different in vivo functions. SmTAL1, SmTAL2 and SmTAL3 have different predicted structures. SmTAL1 and SmTAL2, but not SmTAL3 reversibly bind calcium ions. SmTAL1 and SmTAL2 bind an overlapping but different range of other cations. All three proteins form dimers; calcium ions have no effect on the dimerization. SmTAL1 binds to praziquantel; SmTAL1 and SmTAL3 bind calmodulin antagonists.
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Affiliation(s)
- Charlotte M Thomas
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK; Institute for Global Food Security, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, UK
| | | | - David W Dunne
- Department of Pathology, University of Cambridge, Cambridge, CB2 1QP, UK
| | - David J Timson
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK; Institute for Global Food Security, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, UK.
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Schistosoma japonicum tegumental protein 20.8, role in reproduction through its calcium binding ability. Parasitol Res 2013; 113:491-7. [DOI: 10.1007/s00436-013-3678-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 10/31/2013] [Indexed: 10/26/2022]
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Banford S, Drysdale O, Hoey EM, Trudgett A, Timson DJ. FhCaBP3: a Fasciola hepatica calcium binding protein with EF-hand and dynein light chain domains. Biochimie 2012; 95:751-8. [PMID: 23142130 DOI: 10.1016/j.biochi.2012.10.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 10/31/2012] [Indexed: 11/17/2022]
Abstract
A DNA sequence encoding a protein with predicted EF-hand and dynein light chain binding domains was identified in a Fasciola hepatica EST library. Sequence analysis of the encoded protein revealed that the most similar known protein was the Fasciola gigantica protein FgCaBP3 and so this newly identified protein was named FhCaBP3. Molecular modelling of FhCaBP3 predicted a highly flexible N-terminal region, followed by a domain containing two EF-hand motifs the second of which is likely to be a functioning divalent ion binding site. The C-terminal domain of the protein contains a dynein light chain like region. Interestingly, molecular modelling predicts that calcium ion binding to the N-terminal domain destabilises the β-sheet structure of the C-terminal domain. FhCaBP3 can be expressed in, and purified from, Escherichia coli. The recombinant protein dimerises and the absence of calcium ions appeared to promote dimerisation. Native gel shift assays demonstrated that the protein bound to calcium and manganese ions, but not to magnesium, barium, zinc, strontium, nickel, copper or cadmium ions. FhCaBP3 interacted with the calmodulin antagonists trifluoperazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and chlorpromazine as well as the myosin regulatory light chain-binding drug praziquantel. Despite sequence and structural similarities to other members of the same protein family from F. hepatica, FhCaBP3 has different biochemical properties to the other well characterised family members, FH22 and FhCaBP4. This suggests that each member of this trematode calcium-binding family has discrete functional roles within the organism.
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Affiliation(s)
- Samantha Banford
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
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Orr R, Kinkead R, Newman R, Anderson L, Hoey EM, Trudgett A, Timson DJ. FhCaBP4: a Fasciola hepatica calcium-binding protein with EF-hand and dynein light chain domains. Parasitol Res 2012; 111:1707-13. [DOI: 10.1007/s00436-012-3010-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 06/11/2012] [Indexed: 01/30/2023]
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Zhang Z, Xu H, Gan W, Zeng S, Hu X. Schistosoma japonicum calcium-binding tegumental protein SjTP22.4 immunization confers praziquantel schistosomulumicide and antifecundity effect in mice. Vaccine 2012; 30:5141-50. [PMID: 22683520 DOI: 10.1016/j.vaccine.2012.05.056] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 04/27/2012] [Accepted: 05/22/2012] [Indexed: 11/19/2022]
Abstract
A family of platyhelminth tegument-specific proteins comprising of one or two calcium ion binding EF-hand and a dynein light chain-like domain, termed tegumental proteins, are considered as candidates of vaccine. In this study, we cloned and characterized SjTP22.4, a novel membrane-anchored tegumental protein in Schistosoma japonicum with theoretic MW of 22.4. The recombinant SjTP22.4 could be recognized by S. japonicum infected sera. Immunofluorescence revealed that this protein is not only located on the surface of tegument of adult and schistosomulum and cercaria, but also in the parenchymatous tissues and intestinal epithelium. Circular dichroism (CD) measurement demonstrated rSjTP22.4 had Ca(2+)-binding ability. The rSjTP22.4 vaccination without adjuvants produced comparable high level of antibody with that of immunization with adjuvants together indicated it was an antigen of strong antigenicity. The level of IgG1 is much higher than that of IgG2a and IgE is nearly negative in S. japonicum-infected and rSjTP22.4 immunized mice. In cercaria challenge experiment, mice vaccinated with SjTP22.4 showed no reduction in adult burden and egg production, comparing with the control mice, but 41% decrease in egg mature rate and 32% reduction in liver egg granuloma area. However, the SjTP22.4 immunized mice that received praziquantel treatment at 10d post infection caused 26% reduction in adult burden and 53% decrease in egg mature rate, comparing with the control mice only received praziquantel treatment. In conclusion, SjTP22.4 is a valuable vaccine candidate for S. japonicum of anti-pathogenesis and anti-transmission effect and plays a synergetic role in praziquantel to kill schistosomulum.
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Affiliation(s)
- Zhaoping Zhang
- Department of Parasitology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
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Zhou Y, Zhang H, Sun XJ, Zheng D, Liang YJ, Luo J, Wang Y, Zhang ZS. Murine CD8+T cell cytotoxicity against schistosomula induced by inoculation of schistosomal 22.6/26GST coupled Sepharose 4B beads. Vaccine 2012; 30:2440-7. [DOI: 10.1016/j.vaccine.2012.01.068] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 01/16/2012] [Accepted: 01/21/2012] [Indexed: 10/14/2022]
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Kurup SP, Tewari AK. Induction of protective immune response in mice by a DNA vaccine encoding Trypanosoma evansi beta tubulin gene. Vet Parasitol 2012; 187:9-16. [PMID: 22317783 DOI: 10.1016/j.vetpar.2012.01.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 12/27/2011] [Accepted: 01/03/2012] [Indexed: 11/19/2022]
Abstract
Surra, caused by Trypanosoma evansi, is an economically important veterinary disease of the tropics. Lack of effective drugs or vaccines have made surra a severe economic burden particularly in Asia and sub-Saharan Africa. In this study, a naked DNA construct encoding full length T. evansi beta (β) tubulin gene was used to immunize mice, to elicit a T. evansi β tubulin protein specific humoral immune response, delineated by ELISA. The serum cytokine profile post immunization, as determined by flow cytometry bead based assay, showed a predominant T helper cell Type 1 (Th1) response with significant increase in levels of IFNγ and TNFα. Lethal challenge with T. evansi blood-form trypomastigotes post immunization generated a β tubulin specific recall response and a stronger Th1 type serum cytokine profile which correlated with an extended survival and better control of parasitemia in the immunized mice.
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Affiliation(s)
- Samarchith P Kurup
- Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh 243 122, India
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Cloning and expression of 21.1-kDa tegumental protein of Clonorchis sinensis and human antibody response to it as a trematode–nematode pan-specific serodiagnosis antigen. Parasitol Res 2010; 108:161-8. [DOI: 10.1007/s00436-010-2050-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 09/03/2010] [Indexed: 10/19/2022]
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16
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Molecular characterization and expression of the MYND-ZF gene from Clonorchis sinensis. Parasitol Res 2010; 107:1249-55. [DOI: 10.1007/s00436-010-1995-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2010] [Accepted: 07/14/2010] [Indexed: 10/19/2022]
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Anti-VEGF single-chain antibody GLAF-1 encoded by oncolytic vaccinia virus significantly enhances antitumor therapy. Proc Natl Acad Sci U S A 2009; 106:12915-20. [PMID: 19617539 DOI: 10.1073/pnas.0900660106] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We previously reported that the replication-competent vaccinia virus (VACV) GLV-1h68 shows remarkable oncolytic activity and efficacy in different animal models as a single treatment modality and also in combination with chemotherapy [Yu YA, et al. (2009) Mol Cancer Ther 8:141-151]. Here, we report the construction of 3 VACV strains encoding GLAF-1, a previously undescribed engineered single-chain antibody (scAb). This unique scAb is transcribed from 3 vaccinia promoters (synthetic early, early/late, and late) and directed against both human and murine VEGFs. The expression of GLAF-1 was demonstrated in cell cultures. Also, the replication efficiency of all GLAF-1-expressing VACV strains in cell culture was similar to that of the parental GLV-1h68 virus. Successful tumor-specific delivery and continued production of functional scAb derived from individual VACV strains were obtained in tumor xenografts following a single intravenous injection of the virus. The VACV strains expressing the scAb exhibited significantly enhanced therapeutic efficacy in comparison to treatment of human tumor xenografts with the parental virus GLV-1h68. This enhanced efficacy was comparable to the concomitant treatment of tumors with a one-time i.v. injection of GLV-1h68 and multiple i.p. injections of Avastin. Taken together, the VACV-mediated delivery and production of immunotherapeutic anti-VEGF scAb in colonized tumors may open the way for a unique therapy concept: tumor-specific, locally amplified drug therapy in humans.
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Li SQ, Yang WB, Lun ZR, Ma LJ, Xi SM, Chen QL, Song XW, Kang J, Yang LZ. Immunization with recombinant actin from Trypanosoma evansi induces protective immunity against T. evansi, T. equiperdum and T. b. brucei infection. Parasitol Res 2008; 104:429-35. [DOI: 10.1007/s00436-008-1216-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Accepted: 09/23/2008] [Indexed: 11/29/2022]
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Huang Y, Zhou Z, Hu X, Wei Q, Xu J, Wu Z, Yu X. A novel tegumental protein 31.8 kDa of Clonorchis sinensis: sequence analysis, expression, and immunolocalization. Parasitol Res 2007; 102:77-81. [PMID: 17768637 DOI: 10.1007/s00436-007-0728-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Accepted: 08/14/2007] [Indexed: 11/24/2022]
Abstract
The complementary DNA (cDNA) plasmid libraries of adult worm, metacercariae and egg of Clonorchis sinensis (C. sinensis) were constructed for researches on genomics and proteomics of C. sinensis. The full-length cDNA sequence encoding tegumental protein 31.8 kDa (CsTP31.8) was identified from the adult cDNA library. The cDNA sequence has been submitted to the GeneBank Database with accession number ABK60086. This novel cDNA sequence contains 828 bp with a putative open reading frame of 275 amino acids. The deduced amino acid sequence shows identity to membrane-associate antigens or tegumental antigens of other species. There were conserved calcium-binding EF hand and dynein light chain type 1 in the sequence. CsTP31.8 transcripts were detected in cDNA libraries of adult worm and metacercariae but not in that of egg. Recombinant CsTP31.8 was expressed and purified from Escherichia coli BL21 (DE3). CsTP31.8 was immunolocalized at the tegument of adult C. sinensis by using antirecombinant CsTP31.8 sera.
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Affiliation(s)
- Yan Huang
- Department of Parasitology, Zhongshan School of Medicine, Sun Yat-Sen University, 74th, Zhongshan Road 2, Guangzhou, 510089, People's Republic of China
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Li SQ, Fung MC, Reid SA, Inoue N, Lun ZR. Immunization with recombinant beta-tubulin fromTrypanosoma evansiinduced protection againstT. evansi,T. equiperdumandT. b. bruceiinfection in mice. Parasite Immunol 2007; 29:191-9. [PMID: 17371456 DOI: 10.1111/j.1365-3024.2006.00933.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The beta-tubulin gene of Trypanosoma evansi (STIB 806) was cloned and expressed in Escherichia coli. The predicted amino acid sequence of T. evansi beta-tubulin shows 100%, 99.8%, 99.1%, and 98.6% homology with T. equiperdum, T. b. brucei, T. cruzi and T. danilewskyi, respectively, but is diverse from that of T. cyclops, showing only 51.6% of homology. Recombinant beta-tubulin was expressed as inclusion bodies in E. coli. It was purified and renatured for immunological studies. Mice immunized with the renatured recombinant beta-tubulin were protected from lethal challenge with T. evansi STIB 806, T. equiperdum STIB 818 and T. b. brucei STIB 940, showing 83.3%, 70% and 76.7% protection, respectively. Serum collected from the rabbit immunized with recombinant beta-tubulin inhibited the growth of T. evansi, T. equiperdum and T. b. brucei in vitro. Serum from mice and rabbits immunized with recombinant beta-tubulin recognized only T. evansi beta-tubulin and not mouse beta-tubulin. The results of this study demonstrated that the recombinant T. evansi beta-tubulin is a potential candidate for the development of a vaccine to prevent animal trypanosomiasis caused by these three trypanosome species.
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Affiliation(s)
- S-Q Li
- Centre for Parasitic Organisms, State Key Laboratory of Biocontrol and Key Laboratory for Tropical Diseases Control of the Ministry of Education, School of Life Sciences, Sun Yat-Sen (Zhongshan) University, Guangzhou, P.R. China
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Fitzsimmons CM, McBeath R, Joseph S, Jones FM, Walter K, Hoffmann KF, Kariuki HC, Mwatha JK, Kimani G, Kabatereine NB, Vennervald BJ, Ouma JH, Dunne DW. Factors Affecting Human IgE and IgG Responses to Allergen-Like Schistosoma mansoni Antigens: Molecular Structure and Patterns of in vivo Exposure. Int Arch Allergy Immunol 2006; 142:40-50. [PMID: 17019080 DOI: 10.1159/000095997] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Accepted: 07/27/2006] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The human IgE response is associated with allergy and with host defence against parasitic worms. A response to Sm22.6, the dominant IgE antigen in adult Schistosoma mansoni worms, correlates with resistance to re-infection after treatment. Sm22.6 is one of a family of EF-hand containing parasite proteins with sequence similarity to dynein light chain (DLC) and with major non-parasite allergens. Here we compare human IgE and IgG responses to other family members, Sm20.8 and Sm21.7, as well as to SmDLC1, relating these to antigen structure and expression in parasite life stages. METHODS Recombinant antigens were used in ELISA to measure antibody isotype responses in 177 cases from an endemic area, before and 7 weeks after treatment. Parasite antigen expression was assessed by RT-PCR and Western blotting. RESULTS Levels of antibodies to Sm22.6 and Sm20.8 (but not to Sm21.7 or SmDLC1) showed posttreatment increases in all but young children. Many produced IgE to Sm22.6 and Sm20.8 (2 EF-hands), few to Sm21.7 (1 EF-hand) or SmDLC1 (no EF-hands). Sm21.7 was expressed in cercariae, adults and eggs, Sm22.6 and Sm20.8 were concentrated in the adult. CONCLUSIONS These studies suggest that IgE antigens Sm22.6 and Sm20.8 are only released to boost antibodies when adult worms die, whilst Sm21.7 and SmDLC1 are released constantly from eggs dying in host tissue. IgE responses to these allergen-like molecules may be influenced by patterns of exposure and the number of EF-hand motifs.
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Lin YL, He S. Sm22.6 antigen is an inhibitor to human thrombin. Mol Biochem Parasitol 2006; 147:95-100. [PMID: 16499980 DOI: 10.1016/j.molbiopara.2006.01.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 12/10/2005] [Accepted: 01/25/2006] [Indexed: 11/18/2022]
Abstract
The physiological role of Schistosomiasis mansoni 22.6 antigen (sm22.6 Ag) and its pathogenic effect on the human host has never been reported. Recombinant sm22.6 Ag is a homogenous polymer under non-denaturing/non-reducing conditions, and an inhibitor to human thrombin. Kinetic and Western blot assays show that the recombinant protein interacts with human thrombin and inhibits proteolytic activity of the protease. Tests of whole blood revealed that coagulation time was significantly delayed (3-5 times longer) in the presence of the recombinant protein at a concentration similar to thrombin in normal blood samples. Kinetic studies revealed that the delayed coagulation time was due to the inhibition of alpha-thrombin proteolytic activity by the parasite protein in an irreversible pattern, and a reversible inhibition to gamma-thrombin. Also, Western blot analysis under non-denaturing/non-reducing conditions showed that sm22.6 Ag binds to both alpha- and gamma-thrombin. Our results strongly suggest that sm22.6 antigen plays a role in down-regulation of coagulation in humans.
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Affiliation(s)
- Ya-Ling Lin
- Department of Parasitology, China Medical University School of Medicine, Taichung, 92 Hseu-shi road, Taichung, Taiwan, ROC
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Zhang Y, Taylor MG, Johansen MV, Bickle QD. Vaccination of mice with a cocktail DNA vaccine induces a Th1-type immune response and partial protection against Schistosoma japonicum infection. Vaccine 2001; 20:724-30. [PMID: 11738735 DOI: 10.1016/s0264-410x(01)00420-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Several defined vaccine candidate antigens of Schistosoma japonicum have shown promise in large animal vaccination experiments. However, vaccination of mice in the laboratory with either single recombinant antigens or DNA encoding forms of the individual antigens has so far failed to induce significant protection against S. japonicum cercarial challenge infection as judged by worm reduction, although specific antibodies were generated. This is in contrast to the results achieved using radiation-attenuated vaccines which are highly protective. Even in large animal vaccination experiments, the protection levels obtained with single defined antigens were far below those achieved using the attenuated vaccines. One possible interpretation is that the immune responses induced by single antigen vaccination may not be strong enough to combat the challenging infection. We, therefore, carried out mouse vaccination experiments using a cocktail DNA vaccine comprising four DNA plasmids encoding four different S. japonicum antigens, Sj62, Sj28, Sj23 and Sj14-3-3, respectively. We, also investigated whether co-injection of the mouse IL-12 encoding plasmid with the cocktail DNA vaccine was able to enhance the Th1 responses and hence the protective immunity. Three intramuscular injections of the cocktail DNA vaccine induced a significant Th1-type cellular response with high level of IFN-gamma production by splenocytes upon in vitro stimulation with recombinant antigens. Importantly, significant IgG antibody responses were also induced against crude worm antigens. In two out of three experiments, significant resistance (34-37 and 44-45%, respectively) was demonstrated while another experiment did not show any protection against S. japonicum cercarial challenge infection. Co-injection of the IL-12 encoding DNA did not further enhance these responses, nor the level of resistance, compared with the cocktail DNA alone.
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Affiliation(s)
- Y Zhang
- Immunology Unit, Department of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
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Loukas A, Jones MK, King LT, Brindley PJ, McManus DP. Receptor for Fc on the surfaces of schistosomes. Infect Immun 2001; 69:3646-51. [PMID: 11349025 PMCID: PMC98357 DOI: 10.1128/iai.69.6.3646-3651.2001] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Schistosoma mansoni masks its surface with adsorbed host proteins including erythrocyte antigens, immunoglobulins, major histocompatibility complex class I, and beta(2)-microglobulin (beta(2)m), presumably as a means of avoiding host immune responses. How this is accomplished has not been explained. To identify surface receptors for host proteins, we biotinylated the tegument of live S. mansoni adults and mechanically transformed schistosomula and then removed the parasite surface with detergent. Incubation of biotinylated schistosome surface extracts with human immunoglobulin G (IgG) Fc-Sepharose resulted in purification of a 97-kDa protein that was subsequently identified as paramyosin (Pmy), using antiserum specific for recombinant Pmy. Fc also bound recombinant S. mansoni Pmy and native S. japonicum Pmy. Antiserum to Pmy decreased the binding of Pmy to Fc-Sepharose, and no proteins bound after removal of Pmy from extracts. Fluoresceinated human Fc bound to the surface, vestigial penetration glands, and nascent oral cavity of mechanically transformed schistosomula, and rabbit anti-Pmy Fab fragments ablated the binding of Fc to the schistosome surface. Pmy coprecipitated with host IgG from parasite surface extracts, indicating that complexes formed on the parasite surface as well as in vitro. Binding of Pmy to Fc was not inhibited by soluble protein A, suggesting that Pmy does not bind to the region between the CH2 and CH3 domains used by many other Fc-binding proteins. beta(2)m did not bind to the schistosome Fc receptor (Pmy), a finding that contradicts reports from earlier workers but did bind to a heteromultimer of labeled schistosomula surface proteins. This is the first report of the molecular identity of a schistosome Fc receptor; moreover it demonstrates an additional aspect of the unusual and multifunctional properties of Pmy from schistosomes and other parasitic flatworms.
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Affiliation(s)
- A Loukas
- Molecular Parasitology Laboratory, Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, Queensland 4006, The University of Queensland, Queensland 4072, Australia.
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25
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Scott JC, McManus DP. Molecular cloning and enzymatic expression of the 28-kDa glutathione S-transferase of Schistosoma japonicum: evidence for sequence variation but lack of consistent vaccine efficacy in the murine host. Parasitol Int 2000; 49:289-300. [PMID: 11077263 DOI: 10.1016/s1383-5769(00)00058-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Glutathione S-transferases (GSTs) have long been regarded as attractive vaccine (and drug) targets in schistosomes due to their suspected role in detoxification processes. Indeed, the 28-kDa GST of Schistosoma mansoni (SmGST28) has proven efficacy as an antigen for protective immunity reducing worm burden, female fecundity and egg viability. In contrast, the vaccinating effects of the bacterial expressed homologue of Philippine S. japonicum (SjpGST28) have proved disappointing, possibly because this recombinant form was an incomplete sequence, lacking five N-terminal amino acids which may have affected its vaccination efficacy. Here we describe the cloning and functional enzymatic expression of a complete cDNA encoding SjpGST28. We report also on the immunogenicity and vaccine efficacy of this molecule as a purified recombinant protein and as a DNA plasmid vaccine in the murine model. We further describe the cloning of several complete cDNAs encoding the Chinese homologue of SjpGST28 and the identification of 3 SjcGST28 sequence variants which are probably encoded by distinct alleles.
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Affiliation(s)
- J C Scott
- Molecular Parasitology Unit, Australian Centre for International and Tropical Health and Nutrition, The University of Queensland, Post Office Royal Brisbane Hospital, Herston, Queensland 4029, Brisbane, Australia
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26
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Li Y, Auliff A, Jones MK, Yi X, McManus DP. Immunogenicity and immunolocalization of the 22.6 kDa antigen of Schistosoma japonicum. Parasite Immunol 2000; 22:415-24. [PMID: 10972848 DOI: 10.1046/j.1365-3024.2000.00319.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The 22.6 kDa tegumental-associated antigens of Schistosoma mansoni (Sm22.6) and Schistosoma japonicum (Sj22.6) are of recognized interest in schistosomiasis vaccine development, although no direct vaccination/challenge experiments using either Sm22.6 or Sj22.6 had been previously described. We report that Escherichia coli-expressed reSj22.6 failed to protect mice or water buffaloes against subsequent challenge with S. japonicum cercariae. This was despite the fact that specific IgG (buffaloes) and IgG and IgE (CBA mice) antibodies were generated against the 22.6 kDa molecule, observations consistent with some of our earlier findings. We could find no evidence from immunolocalization studies that Sj22.6 is expressed or exposed on the surface of the adult parasite since it appears to be restricted to the apical cytoplasm of the tegument and is not associated with the apical or basal membrane or any membrane-bound structures in the apical cytoplasm. Nevertheless, Sj22.6 must be released to the immune system during the course of infection because specific anti-Sj22.6 IgG antibodies were present in the sera of nonvaccinated but challenged mice. We conclude that it may be necessary to produce reSj22.6 in a more relevant expression system, such as baculovirus, to further establish its vaccine potential and that detailed immunochemical and immunolocalization studies of early developmental stages may be necessary to determine how Sj22.6 is released or shed in S. japonicum infections.
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Affiliation(s)
- Y Li
- Molecular Parasitology Unit, Tropical Health Program, Australian Centre for International and Tropical Health and Nutrition, The Queensland Institute of Medical Research and the University of Queensland, Australia
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27
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Scott JC, McManus DP. Characterisation and expression of a cDNA encoding the 80-kDa large subunit of Schistosoma japonicum calpain. Parasitol Int 2000; 48:205-14. [PMID: 11227760 DOI: 10.1016/s1383-5769(99)00021-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We describe the cloning of a full length calpain-encoding cDNA constructed from two truncated cDNAs isolated from a cDNA library prepared with mRNA isolated from adult worms of the Philippine strain of Schistosoma japonicum. The cDNA sequence is 2.456 kb in length and predicts a protein of 758 residues with a molecular mass of 86.61 kDa and an isoelectric point of 5.34. Probes spanning the entire calpain cDNA hybridised to multiple bands in genomic DNAs of Philippine (SjP) and Chinese (SjC) S. japonicum, with some restriction fragment length polymorphisms evident between the two strains. Northern hybridisation analysis indicated that the cDNA codes for a single RNA transcript between 2.6 and 3.6 kb in size in the SjP and SjC genomes. After subcloning in the QIA express vectors pQE-31 and pQE-40 and subsequent expression, the recombinant protein was purified and shown to bind calcium. The availability of recombinant S. japonicum calpain will allow its future evaluation as a vaccine candidate, especially in light of recent work with the S. mansoni homologue which has provided evidence that this protein may be a target of protective immunity.
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Affiliation(s)
- J C Scott
- Molecular Parasitology Unit, Australian Centre for International and Tropical Health and Nutrition, Cooperative Research Centre for Vaccine Technology, University of Queensland, Australia
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28
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Abstract
The search for an effective vaccine against schistosomiasis, a parasitic disease currently affecting over 200 million people, remains a desirable but as yet challenging and elusive goal. Progress in the area has been relatively slow but research demonstrating the ability of humans to acquire natural immunity to schistosome infection, together with the successful use in animals of attenuated vaccines, supplemented with encouraging results obtained with defined antigens, suggests that development of a vaccine is achievable. Noteworthy also are recent immune correlate findings which shed light on the complex, putatively protective immune responses in humans, which have improved the prospects of success. With the first human clinical trial having been completed with a schistosome vaccine candidate, this review examines current progress aimed at achieving the objective of a safe and effective vaccine for widespread use against schistosomiasis. The review emphasises work undertaken in the author's laboratory and those of his chief collaborators in the search for a vaccine against schistosomiasis japonica, a disease of major public health significance in The People's Republic of China and The Philippines. Schistosomiasis vaccines should not be considered as the panacea for schistosomiasis control as, when available, it is generally envisaged that they would be used as one component of an integrated strategy complementing currently available and effective tools such as chemotherapy, improvements to sanitation, piped water supply, effective sewage draining and health education.
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Affiliation(s)
- D P McManus
- Molecular Parasitology Unit, Australian Centre for International and Tropical Health and Nutrition, Queensland Institute of Medical Research, Australia.
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McManus DP, Ross AG, Sleigh AC, Williams GM, Yang W, Li YS, Li Y, Acosta L, Waine GJ. Production of interleukin-10 by peripheral blood mononuclear cells from residents of a marshland area in China endemic for Schistosoma japonicum. Parasitol Int 1999; 48:169-77. [PMID: 11269278 DOI: 10.1016/s1383-5769(99)00015-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Interleukin-10 (IL-10) cytokine production was assessed using peripheral blood mononuclear cells (PBMC) from 67 individuals living in an area endemic for schistosomiasis japonica in China (Dongting Lake, Hunan Province), and 11 control subjects from a non-endemic part of the same Province. Production of IL-10 was measured following in vitro stimulation of PBMC using whole parasite extract (SWAP) or a panel of recombinant Schistosoma japonicum antigens (22-kDa tegumental membrane-associated antigen, glyceraldehyde-3-phosphate dehydrogenase, paramyosin, 14-kDa fatty acid-binding protein and 28-kDa glutathione S-transferase) which are of recognized interest in the development of protective immunity to schistosomiasis. Significantly, PBMC isolated from the exposed population compared with the non-exposed population produced higher levels of IL-10. There was a trend towards higher mean levels of IL-10 release in putatively resistant (insusceptible) (consistently egg negative but highly exposed) individuals compared with susceptible (egg-positive) subjects from the exposed population. Analysis of individual exposure (the duration of water contact and the percent body surface area in contact with water, expressed as m2 h/day) vs. IL-10 production indicated a weak but consistent and statistically significant inverse correlation, with lower levels of exposure being associated with higher levels of IL-10. These results suggest an association between IL-10 production and resistance to S. japonicum in subjects from this Chinese population exposed to infection.
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Affiliation(s)
- D P McManus
- Molecular Parasitology Unit, The Bancroft Centre, The Queensland Institute of Medical Research, Brisbane, Australia.
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30
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Ruiz de Eguino AD, Machín A, Casais R, Castro AM, Boga JA, Martín-Alonso JM, Parra F. Cloning and expression in Escherichia coli of a Fasciola hepatica gene encoding a calcium-binding protein. Mol Biochem Parasitol 1999; 101:13-21. [PMID: 10413039 DOI: 10.1016/s0166-6851(99)00012-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A Fasciola hepatica cDNA clone of 994 bp was isolated from an adult worm cDNA expression library using a rabbit serum against the excretory-secretory antigens. The nucleotide sequence of the cDNA clone revealed the presence of an open reading frame of 572 bp which encoded a 22 kDa polypeptide (Fh22) showing putative EF-hand domains. This gene was expressed in Escherichia coli and the recombinant protein used for the production of specific antibodies. Immunoblotting studies using the anti-Fh22 serum showed the presence of a polypeptide of similar molecular mass in the excretory-secretory extract of the adult parasite. The recombinant Fh22 polypeptide showed calcium-dependent electrophoretic mobility (decreased with Ca2(+)-ions and increased with EGTA). The observed behaviour of recombinant Fh22 in gel filtration experiments also suggested calcium-induced conformational changes.
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Affiliation(s)
- A D Ruiz de Eguino
- Departamento de Bioquímica y Biología Molecular, Instituto Universitario de Biotecnología de Asturias (CSIC), Universidad de Oviedo, Spain
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31
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Scott JC, McManus DP. Molecular cloning and functional expression of a cDNA encoding the major endoplasmic reticulum-associated calcium-binding protein, calreticulin, from Philippine strain Schistosoma japonicum. Parasitol Int 1999; 48:35-46. [PMID: 11269324 DOI: 10.1016/s1383-5769(98)00039-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We describe the cloning of a full length calreticulin (CR)-encoding cDNA clone isolated by immunoscreening of a cDNA library prepared with mRNA from adult worms of the Philippine strain of Schistosoma japonicum, the cause of Asian schistosomiasis. The sequence of the cDNA is presented, and its molecular characterisation and functional expression as a Ca2+-binding protein described. The potential role of CR in inducing protective immunity in the schistosomes is discussed.
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Affiliation(s)
- J C Scott
- Molecular Parasitology Unit, Australian Centre for International and Tropical Health and Nutrition, The University of Queensland and The Queensland Institute of Medical Research, Australia
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32
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Scott JC, McManus DP. Identification of novel 70-kDa heat shock protein-encoding cDNAs from Schistosoma japonicum. Int J Parasitol 1999; 29:437-44. [PMID: 10333327 DOI: 10.1016/s0020-7519(98)00227-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A diverse range of organisms respond to a variety of chemical, physiological and temperature-associated stresses by a rapid and transient increase in the synthesis of heat shock proteins. We immunoscreened a Uni-ZAP XR cDNA library, prepared from mRNA isolated from the Philippine strain of the Asian bloodfluke, Schistosoma japonicum, using hyperimmune rabbit sera raised against soluble adult S. japonicum proteins. Six 70-kDa heat shock protein-encoding cDNA clones were identified which, upon further analysis, were separated into two distinct protein groups within the 70-kDa heat shock protein family, the 70-kDa heat shock proteins and the immunoglobulin heavy chain-binding proteins/glucose-related proteins (Grp78). A representative from both groups was fully sequenced and compared with homologous sequences available in the GenBank/EMBL database as the first stage in determining the role of their expression products in the regulation of S. japonicum development, in the induction of immunity, and whether they act as molecular chaperones capable of modulating the correct folding or repair of proteins within this species of schistosome.
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Affiliation(s)
- J C Scott
- Molecular Parasitology Unit, Australian Centre for International and Tropical Health and Nutrition, The University of Queensland, Post Office Royal Brisbane Hospital, Herston
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33
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Hafalla JC, Alamares JG, Acosta LP, Dunne DW, Ramirez BL, Santiago ML. Molecular identification of a 21.7 kDa schistosoma japonicum antigen as a target of the human IgE response. Mol Biochem Parasitol 1999; 98:157-61. [PMID: 10029318 DOI: 10.1016/s0166-6851(98)00160-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- J C Hafalla
- Schistosomiasis Study Group, Research Institute for Tropical Medicine, Alabang, Muntinlupa, Philippines.
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34
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Waine GJ, Mazzer DR, McManus DP. DNA immunization by intramuscular injection or gene gun induces specific IgG antibodies against a Schistosoma japonicum 22 kDa antigen, Sj22, when fused to the murine Ig K-chain secretory leader sequence. Parasite Immunol 1999; 21:53-6. [PMID: 10081772 DOI: 10.1046/j.1365-3024.1999.00183.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The 22 kDa tegumental surface membrane-associated antigen of Schistosoma japonica, Sj22, is of recognized interest in schistosomiasis vaccine research. However, previous attempts to induce antibody responses against Sj22 by DNA immunization have been unsuccessful. In this report we demonstrate that fusing the Sj22 cDNA to the murine immunoglobulin Ig kappa-chain secretory leader sequence results in the generation of antigen-specific IgG antibodies following DNA immunization. Mice were immunized into the skin with DNA-coated gold microspheres using a gene-gun, or into the quadriceps muscle by intramuscular injection. Both methods of delivery generated antigen-specific IgG antibodies against the 22 kDa schistosome antigen. The use of a secretory leader sequence, such as the murine Ig-kappa chain used in this study, may facilitate the induction of host antibody responses following DNA immunization with other parasite cDNAs.
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Affiliation(s)
- G J Waine
- Molecular Parasitology Unit, Australian Centre for International and Tropical Health and Nutrition, Queensland Institute of Medical Research, Royal Brisbane Hospital, Australia
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35
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Molecular cloning and expression of a Schistosoma japonicum tegumental membrane-associated antigen from Japanese strain. Parasitol Int 1998. [DOI: 10.1016/s1383-5769(98)00033-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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36
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Abstract
There are no vaccines currently available to control the major human parasitic diseases, although there is evidence of acquired immunity and resistance to reinfection in most of the parasitic infections. The present manuscript concentrates on the vaccines for parasitic diseases that are in the most advanced stages of development: malaria, leishmaniasis and schistosomiasis. Vaccines for malaria and leishmaniasis have been taken to clinical trials while vaccines for schistosomiasis are being considered for Phase I (assessment of safety and immune responsiveness in volunteers). We have attempted to give a factual account of the present status of knowledge of vaccines against human parasitic diseases, emphasizing both the successes and setbacks. We do not intend to cover the enormous literature in the field but have concentrated on the most promising antigenic preparations. Finally, some new approaches for the development of vaccines are discussed including nucleic acid vaccines and the use of cytokines as adjuvants.
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Affiliation(s)
- F G Abath
- Departamento de Imunologia, Centro de Pesquisas Aggeu Magalhães, Cidade Universitaria, Recife-PE, Brazil.
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37
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Mohamed MM, Shalaby KA, LoVerde PT, Karim AM. Characterization of Sm20.8, a member of a family of schistosome tegumental antigens. Mol Biochem Parasitol 1998; 96:15-25. [PMID: 9851603 DOI: 10.1016/s0166-6851(98)00088-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Two cDNA clones each encoding a 20.8-kDa protein (Sm20.8) were identified from the human blood fluke Schistosoma mansoni sporocyst and adult worm cDNA expression libraries by antibodies derived from rabbits vaccinated with irradiated cercariae and purified over an NP-40 extract of 3h schistosomula. Each identified cDNA has an open reading frame encoding a protein of 181 amino acids and shows homology (29-30%) with Sm21.7, Sm22.6, and Sj22.6, previously identified as belonging to a family of soluble schistosome tegumental antigens. An EF-hand calcium-binding motif is found in Sm20.8 protein in two different positions. However, neither motif binds 45calcium (45Ca) Recombinant Sm20.8 showed immunoreactivity with sera from infected humans and rabbits vaccinated with irradiated cercariae. Polyclonal rabbit sera against the Sm20.8 recognized the native protein in an extract of infected snail (sporocyst), cercariae, 3 hour schistosomules (3 h NP-40) and an adult worm preparation but not in uninfected snail tissue or eggs. Further demonstration that Sm20.8 was expressed in the different developmental stages of the parasite was by RT-PCR. Confocal microscopy demonstrates that Sm20.8 localizes to the tegument of adult worms and 3 h np-40. The IgG fraction specific to Sm20.8 mediated complement killing of schistosomules in vitro by 34%. Vaccination of mice with naked DNA containing the Sm20.8 gene and subsequently challenged with cercariae showed 30% reduction in worm burden compared to controls.
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Affiliation(s)
- M M Mohamed
- Department of Biochemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
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38
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Santiago ML, Hafalla JC, Kurtis JD, Aligui GL, Wiest PM, Olveda RM, Olds GR, Dunne DW, Ramirez BL. Identification of the Schistosoma japonicum 22.6-kDa antigen as a major target of the human IgE response: similarity of IgE-binding epitopes to allergen peptides. Int Arch Allergy Immunol 1998; 117:94-104. [PMID: 9784652 DOI: 10.1159/000023995] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Human resistance to reinfection with Schistosoma mansoni and Schistosoma haematobium correlates with elevated IgE titers against worm antigens (soluble worm antigen preparation, SWAP). In S. mansoni infection, low levels of reinfection following chemotherapy are associated with the recognition of a cloned tegumental protein Sm22.6. Because of potential species-specific differences in resistance to schistosomes, we attempted to identify Schistosoma japonicum antigens recognized by human IgE. Following a survey of 176 infected individuals in Leyte, Philippines, we show that IgE antibodies from the majority of older, high-IgE/SWAP responders recognize antigens in the 22 (Sj22)-, 45-, 78- and 97-kDa range in SWAP. Limited IgE cross-reactivity between Sj22 and Sm22 was observed following a comparison of Filipino IgE responses to these antigens. The antigen was cloned from an adult S. japonicum lambda-ZAP cDNA library (Mindoro strain) by immunoscreening with pooled high-titer IgE antisera and a rabbit anti-Sj22 polyclonal antibody. The deduced amino acid sequence of the identified cDNA clone, MJ-1, showed significant homology to Sm22.6 (74%) and Sj22.6 (99%). Although the molecular sequence of Sj22.6 has already been reported, this is the first demonstration of its recognition by human IgE, thereby strengthening its potential as a vaccine candidate. Using an overlapping peptide approach, four IgE-binding epitopes were identified in Sj22.6, two of which exhibited similarities to known IgE-binding epitopes from codfish (Gad c 1) and beta-lactoglobulin-related allergens. These findings suggest that allergy and protective immunity to helminth infection may be linked by the structural similarities of epitopes recognized by human IgE.
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Affiliation(s)
- M L Santiago
- Schistosomiasis Study Group, Research Institute for Tropical Medicine, Alabang, Muntinlupa City, Philippines
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39
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Waine GJ, Yang W, Ross AG, Li YS, Sleigh AC, Kalinna BH, Scott JC, Mazzer D, Li Y, McManus DP. Differential antigen-stimulated proliferation of human mononuclear cells by recombinant Schistosoma japonicum antigens in a Chinese population. Clin Exp Immunol 1998; 112:69-73. [PMID: 9566792 PMCID: PMC1904938 DOI: 10.1046/j.1365-2249.1998.00542.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Peripheral blood mononuclear cells (PBMC) from 117 individuals living on two islands in an area (Dongting Lake) endemic for schistosomiasis japonica in China, and 15 control individuals from a non-endemic area of China, were assessed for antigen-stimulated proliferation against five recombinant Schistosoma japonicum antigens of recognized interest in the development of immunity to schistosomiasis. Two recombinant antigens, paramyosin and 28-kD glutathione-S-transferase, stimulated cellular proliferation (stimulation index > or = 3.0) in 38.5% and 42.5% of subjects, respectively, a level similar to that induced by a soluble whole parasite extract (51.3%). In contrast, three other recombinant antigens tested--a fatty acid binding protein, 22-kD tegumental membrane-associated antigen, and glyceraldehyde-3-phosphate dehydrogenase--stimulated PBMC proliferation in only 3-8% of subjects. Moreover, we also identified a positive association between the degree of exposure, and cellular proliferation following stimulation with recombinant paramyosin or whole parasite extract. Highly significant differences in antigen-stimulated proliferation were also observed between the two islands, Niangashan and Qingshan. The whole parasite extract stimulated proliferation in 90% of subjects from Niangashan island compared with only 42.1% of subjects from Qingshan island (chi2 = 16.88, P = 0.00004), while glutathione-S-transferase stimulated proliferation in 77.3% of subjects from Niangashan island compared with only 34.7% of subjects from Qingshan island (chi2 = 13.09, P = 0.003). A similar, but not significant, trend was observed for paramyosin and the fatty-acid binding protein. The identification of differential cellular proliferative responses to specific schistosome antigens within an infected human population may have important practical implications for vaccine development against schistosomiasis japonica.
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Affiliation(s)
- G J Waine
- Molecular Parasitology Unit, The Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Australia
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40
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Hoffmann KF, Strand M. Molecular characterization of a 20.8-kDa Schistosoma mansoni antigen. Sequence similarity to tegumental associated antigens and dynein light chains. J Biol Chem 1997; 272:14509-15. [PMID: 9169407 DOI: 10.1074/jbc.272.23.14509] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Survival of Schistosoma mansoni within the infected host requires the parasite to actively maintain its protective tegument. The components responsible for this maintenance are therefore attractive targets for immunoprophylaxis or chemotherapy. Here we report the molecular characterization of a 20.8-kDa tegumental antigen with sequence similarity to dynein light chains and tegumental associated antigens. A cDNA encoding the 20.8-kDa polypeptide contains an open reading frame of 181 amino acids and predicts an isoelectric point of 7.27. Expression of the 20.8-kDa antigen is developmentally regulated, with the highest concentration found in cercariae. Our data show that the 20.8-kDa polypeptide specifically interacts with a S. mansoni 10.4-kDa dynein light chain that we have previously described (Hoffmann, K. F., and Strand, M. (1996) J. Biol. Chem. 271, 26117-26123). Velocity sedimentation analysis of a parasite extract demonstrated that this 10.4-kDa dynein light chain and the 20.8-kDa polypeptide were present in a complex that sedimented at 4.4 Svedberg units. We have also shown by antibody cross-reactivity that a 20.8-kDa homolog of the S. mansoni antigen is present in Schistosoma japonicum, but not in Schistosoma hematobium or Fasciola hepatica. Because the 20.8-kDa polypeptide displays ideal characteristics of a potential vaccine candidate, including (i) expression in the tegument, (ii) significant divergence from mammalian brain cytoplasmic dynein, and (iii) a conserved homolog in S. japonicum, we are currently evaluating its immunoprophylactic efficacy.
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Affiliation(s)
- K F Hoffmann
- Department of Pharmacology and Molecular Sciences, Center for Monoclonal Studies, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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41
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Abstract
Development of a vaccine for schistosomiasis, a parasitic disease currently affecting over 200 million people worldwide, has been targeted as a priority by the World Health Organisation. Research demonstrating the ability of humans to acquire natural immunity to schistosome infection, together with the successful use of attenuated vaccines in animals both under laboratory and field conditions, suggest that development of a human vaccine is feasible. Attenuated vaccines for schistosomiasis are considered neither safe nor practicable for human use, however, and therefore other approaches must be considered. This review examines progress currently being undertaken in a number of different areas towards achieving the goal of a safe and effective human vaccine for schistosomiasis.
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Affiliation(s)
- G J Waine
- Molecular Parasitology Unit, Queensland Institute of Medical Research, Australia.
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Yang W, Scott JC, McManus DP. A molecular comparison of glyceraldehyde-3-phosphate dehydrogenase and a 22.6-kDa tegument membrane-associated antigen from Chinese and Philippine Schistosoma japonicum. Parasitol Int 1997. [DOI: 10.1016/s1383-5769(97)00008-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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43
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Abstract
The recent successful immunization of experimental animals using nucleic acids has provided a revolutionary new approach in vaccinology. In this article, Gary Waine and Don McManus examine the potential of nucleic acid vaccines for their effectiveness not only against infectious and parasitic organisms exhibiting an intracellular phase during their life cycle, but also against parasitic helminths, whose life cycle stages are either predominantly or completely extracellular.
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Affiliation(s)
- G J Waine
- Tropical Health Programme, Molecular Parasitology Unit, Queensland Institute of Medical Research, Brisbane, Australia.
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Becker MM, Kalinna BH, Waine GJ, McManus DP. Gene cloning, overproduction and purification of a functionally active cytoplasmic fatty acid-binding protein (Sj-FABPC) from the human blood fluke Schistosoma japonicum. Gene 1994; 148:321-5. [PMID: 7958962 DOI: 10.1016/0378-1119(94)90706-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We report the gene cloning, molecular characterisation and purification of a 14.7-kDa functionally active recombinant (re) cytoplasmic fatty acid-binding protein (Sj-FABPC) from the Chinese strain of the human bloodfluke Schistosoma japonicum (Sj). As schistosomes are unable to synthesise long chain fatty acids and sterols de novo and must, therefore, take up these lipids from the host, Sj-FABPC is an attractive vaccine and/or drug target. Clone 39 (C39), which contains the entire Sj-FABPC gene, was isolated from a Sj lambda ZAPII cDNA expression library immunoscreened with hyperimmune rabbit serum (HRS) raised against soluble adult Sj proteins. The complete ORF (open reading frame) of Sj-FABPC encodes a protein of 132 amino acids (aa) of 14.7 kDa. The aa sequence of Sj-FABPC exhibits 91% identity to a FABP of S. mansoni (Sm14) and 45% identity to a FABP of Fasciola hepatica (Fh15), putative vaccine candidates for schistosomiasis. Sj-FABPC was subcloned into the QIAexpress vector, pQE-10, and subsequently expressed in Escherichia coli. The re-Sj-FABPC, purified under non-denaturing conditions, was recognized by sera from patients with acute and chronic schistosomiasis japonica. The purified re-Sj-FABPC was also shown to bind to palmitic acid with high affinity. The functional expression of Sj-FABPC will facilitate studies on re-Sj-FABPC to assess its potential as a drug and/or vaccine candidate.
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Affiliation(s)
- M M Becker
- Molecular Parasitology Unit, Queensland Institute of Medical Research, Brisbane, Australia
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