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Zhao G, Dong H, Dai L, Xie H, Sun H, Zhang J, Wang Q, Xu C, Yin K. Proteomics analysis of Toxoplasma gondii merozoites reveals regulatory proteins involved in sexual reproduction. Microb Pathog 2024; 186:106484. [PMID: 38052278 DOI: 10.1016/j.micpath.2023.106484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 10/18/2023] [Accepted: 11/29/2023] [Indexed: 12/07/2023]
Abstract
Sexual reproduction plays a crucial role in the transmission and life cycle of toxoplasmosis. The merozoites are the only developmental stage capable of differentiation into male and female gametes, thereby initiating sexual reproduction to form oocysts that are excreted into the environment. Hence, our study aimed to perform proteomic analyses of T. gondii Pru strain merozoites, a pre-sexual developmental stage in cat IECs, and tachyzoites, an asexual developmental stage, using the tandem mass tag (TMT) method in order to identify the differentially expressed proteins (DEPs) of merozoites. Proteins functions were subjected to cluster analysis, and DEPs were validated through the qPCR method. The results showed that a total of 106 proteins were identified, out of which 85 proteins had quantitative data. Among these, 15 proteins were differentially expressed within merozoites, with four exhibiting up-regulation and being closely associated with the material and energy metabolism as well as the cell division of T. gondii. Two novel DEPs, namely S8GHL5 and A0A125YP41, were identified, and their homologous family members have been demonstrated to play regulatory roles in oocyte maturation and spermatogenesis in other species. Therefore, they may potentially exhibit regulatory functions during the differentiation of micro- and macro-gametophytes at the initiation stage of sexual reproduction in T. gondii. In conclusion, our results showed that the metabolic and divisional activities in the merozoites surpass those in the tachyzoites, thereby providing structural, material, and energetic support for gametophytes development. The discovery of two novel DEPs associated with sexual reproduction represents a significant advancement in understanding Toxoplasma sexual reproduction initiation and oocyst formation.
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Affiliation(s)
- Guihua Zhao
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Hongjie Dong
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Lisha Dai
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Huanhuan Xie
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Hang Sun
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Junmei Zhang
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Qi Wang
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Chao Xu
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
| | - Kun Yin
- Shandong Institute of Parasitic Diseases, Shandong First Medical University & Shandong Academy of Medical Sciences, 11 Taibai Middle Road, Jining City, Shandong Province, 272033, China.
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Perrin AJ, Bisson C, Faull PA, Renshaw MJ, Lees RA, Fleck RA, Saibil HR, Snijders AP, Baker DA, Blackman MJ. Malaria Parasite Schizont Egress Antigen-1 Plays an Essential Role in Nuclear Segregation during Schizogony. mBio 2021; 12:e03377-20. [PMID: 33688001 PMCID: PMC8092294 DOI: 10.1128/mbio.03377-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 01/25/2021] [Indexed: 01/08/2023] Open
Abstract
Malaria parasites cause disease through repeated cycles of intraerythrocytic proliferation. Within each cycle, several rounds of DNA replication produce multinucleated forms, called schizonts, that undergo segmentation to form daughter merozoites. Upon rupture of the infected cell, the merozoites egress to invade new erythrocytes and repeat the cycle. In human malarial infections, an antibody response specific for the Plasmodium falciparum protein PF3D7_1021800 was previously associated with protection against malaria, leading to an interest in PF3D7_1021800 as a candidate vaccine antigen. Antibodies to the protein were reported to inhibit egress, resulting in it being named schizont egress antigen-1 (SEA1). A separate study found that SEA1 undergoes phosphorylation in a manner dependent upon the parasite cGMP-dependent protein kinase PKG, which triggers egress. While these findings imply a role for SEA1 in merozoite egress, this protein has also been implicated in kinetochore function during schizont development. Therefore, the function of SEA1 remains unclear. Here, we show that P. falciparum SEA1 localizes in proximity to centromeres within dividing nuclei and that conditional disruption of SEA1 expression severely impacts the distribution of DNA and formation of merozoites during schizont development, with a proportion of SEA1-null merozoites completely lacking nuclei. SEA1-null schizonts rupture, albeit with low efficiency, suggesting that neither SEA1 function nor normal segmentation is a prerequisite for egress. We conclude that SEA1 does not play a direct mechanistic role in egress but instead acts upstream of egress as an essential regulator required to ensure the correct packaging of nuclei within merozoites.IMPORTANCE Malaria is a deadly infectious disease. Rationally designed novel therapeutics will be essential for its control and eradication. The Plasmodium falciparum protein PF3D7_1021800, annotated as SEA1, is under investigation as a prospective component of a malaria vaccine, based on previous indications that antibodies to SEA1 interfere with parasite egress from infected erythrocytes. However, a consensus on the function of SEA1 is lacking. Here, we demonstrate that SEA1 localizes to dividing parasite nuclei and is necessary for the correct segregation of replicated DNA into individual daughter merozoites. In the absence of SEA1, merozoites develop defectively, often completely lacking a nucleus, and, consequently, egress is impaired and/or aberrant. Our findings provide insights into the divergent mechanisms by which intraerythrocytic malaria parasites develop and divide. Our conclusions regarding the localization and function of SEA1 are not consistent with the hypothesis that antibodies against it confer protective immunity to malaria by blocking merozoite egress.
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Affiliation(s)
- Abigail J Perrin
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Claudine Bisson
- Department of Biological Sciences, Institute of Structural & Molecular Biology, Birkbeck College, University of London, London, United Kingdom
- Centre for Ultrastructural Imaging, Guy's Campus, King's College London, London, United Kingdom
| | - Peter A Faull
- Mass Spectrometry Proteomics Platform, The Francis Crick Institute, London, United Kingdom
| | - Matthew J Renshaw
- Advanced Light Microscopy, The Francis Crick Institute, London, United Kingdom
| | - Rebecca A Lees
- Department of Biological Sciences, Institute of Structural & Molecular Biology, Birkbeck College, University of London, London, United Kingdom
| | - Roland A Fleck
- Centre for Ultrastructural Imaging, Guy's Campus, King's College London, London, United Kingdom
| | - Helen R Saibil
- Department of Biological Sciences, Institute of Structural & Molecular Biology, Birkbeck College, University of London, London, United Kingdom
| | - Ambrosius P Snijders
- Mass Spectrometry Proteomics Platform, The Francis Crick Institute, London, United Kingdom
| | - David A Baker
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Michael J Blackman
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
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Wang X, Xie Y, Jiang N, Wang J, Liang H, Liu D, Yang N, Sang X, Feng Y, Chen R, Chen Q. Enhanced Antimalarial Efficacy Obtained by Targeted Delivery of Artemisinin in Heparin-Coated Magnetic Hollow Mesoporous Nanoparticles. ACS Appl Mater Interfaces 2021; 13:287-297. [PMID: 33356111 DOI: 10.1021/acsami.0c20070] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Malaria is one of the deadliest infectious diseases threatening half of the world population. With the deterioration of the parasiticidal effect of the current antimalarials, novel approaches such as screening of more specific inhibitors and targeted delivery of drugs have been under intensive research. Herein, we prepare hollow mesoporous ferrite nanoparticles (HMFNs) of 200 nm with ferromagnetic properties using a one-pot hydrothermal reaction. A magnetically targeted drug-delivery system coloaded with artemisinin in the inner magnetite shell and heparin on the outer mesoporous shell (HMFN@ART@HEP) is developed. Specific targeting of the magnetic nanoparticles to the parasite-infected erythrocytes is achieved by the attraction between the HMFNs and hemozoin (paramagnetic), a vital metabolite of plasmodium in the erythrocytic stage. With the hemozoin production reaching the maximum during the schizont period of the parasite, HMFN@ART@HEPs are adsorbed to the infected red blood cells (iRBCs), which not only interferes with the release of merozoites but also significantly enhances the inhibitory efficacy due to the increased local concentration of artemisinin. Subsequently, the heparin coated on the surface of the nanoparticles can efficiently interfere with the invasion of freshly released merozoites to new RBCs through the specific interaction between the parasite-derived ligands and heparin, which further increases the inhibitory effect on malaria. As a cluster of heparin, heparin-coated nanoparticles provide stronger blocking capability than free heparin, resulting from multivalent interactions with surface receptors on merozoite. Thus, we have developed a HMFN-based delivery system with considerable antimalarial efficacy, which is a promising platform for treatment against malaria.
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Affiliation(s)
- Xinyi Wang
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
- College of Basic Sciences, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
| | - Yiwei Xie
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Ning Jiang
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Jingyi Wang
- College of Information and Electrical Engineering, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
| | - Hongrui Liang
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Dingyuan Liu
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Na Yang
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Xiaoyu Sang
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Ying Feng
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Ran Chen
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
| | - Qijun Chen
- Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, Key Laboratory of Zoonosis, College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110866, China
- The Research Unit for Pathogenic Mechanisms of Zoonotic Parasites, Chinese Academy of Medical Sciences, 120 Dongling Road, Shenyang 110866, China
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Lu C, Zheng X, Zhang W, Zhao H, MacRaild CA, Norton RS, Zhuang Y, Wang J, Zhang X. Interaction of merozoite surface protein 2 with lipid membranes. FEBS Lett 2019; 593:288-295. [PMID: 30588612 DOI: 10.1002/1873-3468.13320] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 11/26/2018] [Accepted: 12/16/2018] [Indexed: 11/07/2022]
Abstract
Merozoite surface protein 2 (MSP2) is a potential vaccine candidate against malaria, although its functional role is yet to be elucidated. Previous studies showed that MSP2 can interact with membranes, which may facilitate merozoite invasion into the host cell. The N-terminal 25 residues of MSP2 (MSP21-25 ), which may be aggregated on the merozoite surface, play a key role in the interaction with membranes. Here, we investigated the effects of MSP21-25 -membrane interactions on the conformation and aggregation of MSP21-25 and on membrane integrity, using nanodiscs and small unilamellar vesicles as mimetics of cell membranes. MSP21-25 -membrane interactions induced the peptide to form β-structure and to aggregate, depending on the lipid composition of the membrane. Nonfibrillar aggregates in turn disrupted the membrane.
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Affiliation(s)
- Chenghui Lu
- School of Life Sciences, Anhui University, Hefei, China
- Anhui Provincial Engineering Technology Research Center of Microorganisms and Biocatalysis, Hefei, China
| | - Xue Zheng
- School of Life Sciences, Anhui University, Hefei, China
- Anhui Provincial Engineering Technology Research Center of Microorganisms and Biocatalysis, Hefei, China
| | - Wei Zhang
- School of Life Sciences, Anhui University, Hefei, China
- Anhui Provincial Engineering Technology Research Center of Microorganisms and Biocatalysis, Hefei, China
| | - Hongxin Zhao
- High Magnetic Field Laboratory, Key Laboratory of Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China
| | - Christopher A MacRaild
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Raymond S Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Yonglong Zhuang
- Modern Experimental Technology Center, Anhui University, Hefei, China
| | - Junfeng Wang
- High Magnetic Field Laboratory, Key Laboratory of Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China
- Institute of Physical Science and Information Technology, Anhui University, Hefei, China
| | - Xuecheng Zhang
- School of Life Sciences, Anhui University, Hefei, China
- Anhui Provincial Engineering Technology Research Center of Microorganisms and Biocatalysis, Hefei, China
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Collins CR, Hackett F, Atid J, Tan MSY, Blackman MJ. The Plasmodium falciparum pseudoprotease SERA5 regulates the kinetics and efficiency of malaria parasite egress from host erythrocytes. PLoS Pathog 2017; 13:e1006453. [PMID: 28683142 PMCID: PMC5500368 DOI: 10.1371/journal.ppat.1006453] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 06/07/2017] [Indexed: 02/06/2023] Open
Abstract
Egress of the malaria parasite Plasmodium falciparum from its host red blood cell is a rapid, highly regulated event that is essential for maintenance and completion of the parasite life cycle. Egress is protease-dependent and is temporally associated with extensive proteolytic modification of parasite proteins, including a family of papain-like proteins called SERA that are expressed in the parasite parasitophorous vacuole. Previous work has shown that the most abundant SERA, SERA5, plays an important but non-enzymatic role in asexual blood stages. SERA5 is extensively proteolytically processed by a parasite serine protease called SUB1 as well as an unidentified cysteine protease just prior to egress. However, neither the function of SERA5 nor the role of its processing is known. Here we show that conditional disruption of the SERA5 gene, or of both the SERA5 and related SERA4 genes simultaneously, results in a dramatic egress and replication defect characterised by premature host cell rupture and the failure of daughter merozoites to efficiently disseminate, instead being transiently retained within residual bounding membranes. SERA5 is not required for poration (permeabilization) or vesiculation of the host cell membrane at egress, but the premature rupture phenotype requires the activity of a parasite or host cell cysteine protease. Complementation of SERA5 null parasites by ectopic expression of wild-type SERA5 reversed the egress defect, whereas expression of a SERA5 mutant refractory to processing failed to rescue the phenotype. Our findings implicate SERA5 as an important regulator of the kinetics and efficiency of egress and suggest that proteolytic modification is required for SERA5 function. In addition, our study reveals that efficient egress requires tight control of the timing of membrane rupture. Malaria, a disease that kills hundreds of thousands of people each year, is caused by a single-celled parasite that grows in red blood cells of infected individuals. Following each round of parasite multiplication, the infected red cells are actively ruptured in a process called egress, releasing a new generation of parasites. Egress is essential for progression to clinical disease, but little is known about how it is controlled. In this work we set out to address the function in egress of a Plasmodium falciparum protein called SERA5, an abundant component of the vacuole in which the parasite grows. We show that parasites lacking SERA5 (or lacking both SERA5 and a closely-related protein called SERA4) undergo accelerated but defective egress in which the bounding vacuole and red cell membranes do not rupture properly. This impedes the escape and subsequent replication of the newly-developed parasites. We also show that modification of SERA5 by parasites proteases just prior to egress is important for SERA5 function. Our results show that SERA5 is a ‘negative regulator’ of egress, controlling the speed of the pathway that leads to disruption of the membranes surrounding the intracellular parasite. Our findings increase our understanding of the molecular mechanisms underlying malarial egress and show that efficient egress requires tight control of the timing of membrane rupture.
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Affiliation(s)
- Christine R. Collins
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Fiona Hackett
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Jonathan Atid
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Michele Ser Ying Tan
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Michael J. Blackman
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
- Department of Pathogen Molecular Biology, London School of Hygiene & Tropical Medicine, London, United Kingdom
- * E-mail:
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França CT, Hostetler JB, Sharma S, White MT, Lin E, Kiniboro B, Waltmann A, Darcy AW, Li Wai Suen CSN, Siba P, King CL, Rayner JC, Fairhurst RM, Mueller I. An Antibody Screen of a Plasmodium vivax Antigen Library Identifies Novel Merozoite Proteins Associated with Clinical Protection. PLoS Negl Trop Dis 2016; 10:e0004639. [PMID: 27182597 PMCID: PMC4868274 DOI: 10.1371/journal.pntd.0004639] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 03/29/2016] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Elimination of Plasmodium vivax malaria would be greatly facilitated by the development of an effective vaccine. A comprehensive and systematic characterization of antibodies to P. vivax antigens in exposed populations is useful in guiding rational vaccine design. METHODOLOGY/PRINCIPAL FINDINGS In this study, we investigated antibodies to a large library of P. vivax entire ectodomain merozoite proteins in 2 Asia-Pacific populations, analysing the relationship of antibody levels with markers of current and cumulative malaria exposure, and socioeconomic and clinical indicators. 29 antigenic targets of natural immunity were identified. Of these, 12 highly-immunogenic proteins were strongly associated with age and thus cumulative lifetime exposure in Solomon Islanders (P<0.001-0.027). A subset of 6 proteins, selected on the basis of immunogenicity and expression levels, were used to examine antibody levels in plasma samples from a population of young Papua New Guinean children with well-characterized individual differences in exposure. This analysis identified a strong association between reduced risk of clinical disease and antibody levels to P12, P41, and a novel hypothetical protein that has not previously been studied, PVX_081550 (IRR 0.46-0.74; P<0.001-0.041). CONCLUSION/SIGNIFICANCE These data emphasize the benefits of an unbiased screening approach in identifying novel vaccine candidate antigens. Functional studies are now required to establish whether PVX_081550 is a key component of the naturally-acquired protective immune response, a biomarker of immune status, or both.
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Affiliation(s)
- Camila T. França
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Jessica B. Hostetler
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | - Sumana Sharma
- Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | - Michael T. White
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Center for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Enmoore Lin
- Vector Borne Diseases Unit, PNG Institute of Medical Research, Madang, Papua New Guinea
| | - Benson Kiniboro
- Vector Borne Diseases Unit, PNG Institute of Medical Research, Madang, Papua New Guinea
| | - Andreea Waltmann
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Andrew W. Darcy
- National Health Training & Research Institute, Ministry of Health, Honiara, Solomon Islands
| | - Connie S. N. Li Wai Suen
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Peter Siba
- Vector Borne Diseases Unit, PNG Institute of Medical Research, Madang, Papua New Guinea
| | - Christopher L. King
- Center for Global Health & Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Julian C. Rayner
- Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, United Kingdom
- * E-mail: (JCR); (RMF); (IM)
| | - Rick M. Fairhurst
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (JCR); (RMF); (IM)
| | - Ivo Mueller
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
- * E-mail: (JCR); (RMF); (IM)
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Hostetler JB, Sharma S, Bartholdson SJ, Wright GJ, Fairhurst RM, Rayner JC. A Library of Plasmodium vivax Recombinant Merozoite Proteins Reveals New Vaccine Candidates and Protein-Protein Interactions. PLoS Negl Trop Dis 2015; 9:e0004264. [PMID: 26701602 PMCID: PMC4689532 DOI: 10.1371/journal.pntd.0004264] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Accepted: 11/05/2015] [Indexed: 11/27/2022] Open
Abstract
Background A vaccine targeting Plasmodium vivax will be an essential component of any comprehensive malaria elimination program, but major gaps in our understanding of P. vivax biology, including the protein-protein interactions that mediate merozoite invasion of reticulocytes, hinder the search for candidate antigens. Only one ligand-receptor interaction has been identified, that between P. vivax Duffy Binding Protein (PvDBP) and the erythrocyte Duffy Antigen Receptor for Chemokines (DARC), and strain-specific immune responses to PvDBP make it a complex vaccine target. To broaden the repertoire of potential P. vivax merozoite-stage vaccine targets, we exploited a recent breakthrough in expressing full-length ectodomains of Plasmodium proteins in a functionally-active form in mammalian cells and initiated a large-scale study of P. vivax merozoite proteins that are potentially involved in reticulocyte binding and invasion. Methodology/Principal Findings We selected 39 P. vivax proteins that are predicted to localize to the merozoite surface or invasive secretory organelles, some of which show homology to P. falciparum vaccine candidates. Of these, we were able to express 37 full-length protein ectodomains in a mammalian expression system, which has been previously used to express P. falciparum invasion ligands such as PfRH5. To establish whether the expressed proteins were correctly folded, we assessed whether they were recognized by antibodies from Cambodian patients with acute vivax malaria. IgG from these samples showed at least a two-fold change in reactivity over naïve controls in 27 of 34 antigens tested, and the majority showed heat-labile IgG immunoreactivity, suggesting the presence of conformation-sensitive epitopes and native tertiary protein structures. Using a method specifically designed to detect low-affinity, extracellular protein-protein interactions, we confirmed a predicted interaction between P. vivax 6-cysteine proteins P12 and P41, further suggesting that the proteins are natively folded and functional. This screen also identified two novel protein-protein interactions, between P12 and PVX_110945, and between MSP3.10 and MSP7.1, the latter of which was confirmed by surface plasmon resonance. Conclusions/Significance We produced a new library of recombinant full-length P. vivax ectodomains, established that the majority of them contain tertiary structure, and used them to identify predicted and novel protein-protein interactions. As well as identifying new interactions for further biological studies, this library will be useful in identifying P. vivax proteins with vaccine potential, and studying P. vivax malaria pathogenesis and immunity. Trial Registration ClinicalTrials.gov NCT00663546 Plasmodium vivax causes malaria in millions of people each year, primarily in Southeast Asia and Central and South America. P. vivax has a dormant liver stage, which can lead to disease recurrence in infected individuals even in the absence of mosquito transmission. The development of vaccines that target blood-stage P. vivax parasites is therefore likely to be an essential component of any worldwide effort to eradicate malaria. Studying P. vivax is very difficult as this parasite grows poorly in the laboratory and invades only small numbers of young red blood cells in patients. Due to these and other challenges, only a handful of P. vivax proteins have been tested as potential vaccines. To generate more vaccine candidates, we expressed the entire ectodomains of 37 proteins that are predicted to be involved in P. vivax invasion of red blood cells. Antibodies from Cambodian patients with P. vivax malaria recognized heat-sensitive epitopes in the majority of these proteins, suggesting that they are natively folded. We also used the proteins to screen for both predicted and novel protein-protein interactions, confirming that the proteins are functional and further supporting their potential as vaccine candidates. As a new community resource, this P. vivax recombinant protein library will facilitate future studies of P. vivax pathogenesis and immunity, and greatly expands the list of candidate vaccine antigens.
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Affiliation(s)
- Jessica B. Hostetler
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- Malaria Programme, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Sumana Sharma
- Malaria Programme, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - S. Josefin Bartholdson
- Malaria Programme, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Gavin J. Wright
- Malaria Programme, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Rick M. Fairhurst
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (RMF); (JCR)
| | - Julian C. Rayner
- Malaria Programme, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- * E-mail: (RMF); (JCR)
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8
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Cheng Y, Wang B, Sattabongkot J, Lim CS, Tsuboi T, Han ET. Immunogenicity and antigenicity of Plasmodium vivax merozoite surface protein 10. Parasitol Res 2014; 113:2559-68. [PMID: 24764159 DOI: 10.1007/s00436-014-3907-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 04/09/2014] [Indexed: 11/26/2022]
Abstract
Among the proteins involved in the invasion by merozoite, the glycosylphosphatidylinositol-anchored proteins (GPI-APs) are suggested as potential vaccine candidates because of their localization to apical organelles and the surface; these candidates are predicted to play essential roles during invasion. As a GPI-AP, Plasmodium vivax merozoite surface protein 10 (PvMSP-10) induces high antibody titers. However, such high antibody titers have shown no protective efficacy for animals challenged with P. vivax parasites in a previous study. To adequately evaluate the immunogenicity and further characterize PvMSP-10 in order to understand its vaccine potential, we assessed its immunogenicity by immunizing BALB/c mice with cell-free expressed recombinant PvMSP-10 protein. The antigenicity of MSP-10 was analyzed, and we found 42% sensitivity and 95% specificity using serum samples from P. vivax-infected Korean patients. The IgG1 and IgG3 were the predominant immunoreactive antibodies against PvMSP-10 in vivax patient sera, and IgG1 and IgG3 and Th1-type cytokines were predominantly secreted in PvMSP-10-immunized mice. We conclude that the immunogenicity and antigenicity of MSP-10 may serve as a potential vaccine against vivax malaria.
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Affiliation(s)
- Yang Cheng
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Hyoja2-dong, Chuncheon, Gangwon-do, 200-701, Republic of Korea
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9
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Okitsu SL, Boato F, Mueller MS, Li DB, Vogel D, Westerfeld N, Zurbriggen R, Robinson JA, Pluschke G. Antibodies elicited by a virosomally formulated Plasmodium falciparum serine repeat antigen-5 derived peptide detect the processed 47 kDa fragment both in sporozoites and merozoites. Peptides 2007; 28:2051-60. [PMID: 17875342 DOI: 10.1016/j.peptides.2007.08.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 08/04/2007] [Accepted: 08/07/2007] [Indexed: 11/22/2022]
Abstract
Serine repeat antigen-5 (SERA5) is a candidate antigen for inclusion into a malaria subunit vaccine. During merozoite release and reinvasion the 120 kDa SERA5 precursor protein (P120) is processed, and a complex consisting of an N-terminal 47 kDa (P47) and a C-terminal 18kDa (P18) processing product associates with the surface of merozoites. This complex is thought to be involved in merozoite invasion of and/or egress from host erythrocytes. Here we describe the synthesis and immunogenic properties of virosomally formulated synthetic phosphatidylethanolamine (PE)-peptide conjugates, incorporating amino acid sequence stretches from the N-terminus of Plasmodium falciparum SERA5. Choosing an appropriate sequence was crucial for the development of a peptide that elicited high titers of parasite cross-reactive antibodies in mice. Monoclonal antibodies (mAbs) raised against the optimized peptide FB-23 incorporating amino acids 57-94 of SERA5 bound to both P120 and to P47. Western blotting analysis proved for the first time the presence of SERA5 P47 in sporozoites. In immunofluorescence assays, the mAbs stained SERA5 in all its predicted localizations. The virosomal formulation of peptide FB-23 is suitable for use in humans and represents a candidate component for a multi-valent malaria subunit vaccine targeting both sporozoites and blood stage parasites.
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Affiliation(s)
- Shinji L Okitsu
- Molecular Immunology, Swiss Tropical Institute, CH-4002 Basel, Switzerland
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10
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Gillrie MR, Krishnegowda G, Lee K, Buret AG, Robbins SM, Looareesuwan S, Gowda DC, Ho M. Src-family kinase dependent disruption of endothelial barrier function by Plasmodium falciparum merozoite proteins. Blood 2007; 110:3426-35. [PMID: 17693580 PMCID: PMC2200906 DOI: 10.1182/blood-2007-04-084582] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Pulmonary complication in severe Plasmodium falciparum malaria is manifested as a prolonged impairment of gas transfer or the more severe acute respiratory distress syndrome (ARDS). In either clinical presentation, vascular permeability is a major component of the pathologic process. In this report, we examined the effect of clinical P falciparum isolates on barrier function of primary dermal and lung microvascular endothelium in vitro. We showed that parasite sonicates but not intact infected erythrocytes disrupted endothelial barrier function in a Src-family kinase-dependent manner. The abnormalities were manifested both as discontinuous immunofluorescence staining of the junctional proteins ZO-1, claudin 5, and VE-cadherin and the formation of interendothelial gaps in monolayers. These changes were associated with a loss in total protein content of claudin 5 and redistribution of ZO-1 from the cytoskeleton to the membrane and the cytosolic and nuclear fractions. There was minimal evidence of a proinflammatory response or direct cellular cytotoxicity or cell death. The active component in sonicates appeared to be a merozoite-associated protein. Increased permeability was also induced by P falciparum glycophosphatidylinositols (GPIs) and food vacuoles. These results demonstrate that parasite components can alter endothelial barrier function and thus contribute to the pathogenesis of severe falciparum malaria.
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Affiliation(s)
- Mark R Gillrie
- Department of Microbiology and Infectious Diseases, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada
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11
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Proellocks NI, Kovacevic S, Ferguson DJ, Kats LM, Morahan BJ, Black CG, Waller KL, Coppel RL. Plasmodium falciparum Pf34, a novel GPI-anchored rhoptry protein found in detergent-resistant microdomains. Int J Parasitol 2007; 37:1233-41. [PMID: 17521656 PMCID: PMC2712672 DOI: 10.1016/j.ijpara.2007.03.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 02/28/2007] [Accepted: 03/22/2007] [Indexed: 10/23/2022]
Abstract
Apicomplexan parasites are characterised by the presence of specialised organelles, such as rhoptries, located at the apical end of invasive forms that play an important role in invasion of the host cell and formation of the parasitophorous vacuole. In this study, we have characterised a novel Plasmodium falciparum rhoptry protein, Pf34, encoded by a single exon gene located on chromosome 4 and expressed as a 34kDa protein in mature asexual stage parasites. Pf34 is expressed later in the life cycle than the previously described rhoptry protein, Rhoptry Associated Membrane Antigen (RAMA). Orthologues of Pf34 are present in other Plasmodium species and a potential orthologue has also been identified in Toxoplasma gondii. Indirect immunofluorescence assays show that Pf34 is located at the merozoite apex and localises to the rhoptry neck. Pf34, previously demonstrated to be glycosyl-phosphatidyl-inositol (GPI)-anchored [Gilson, P.R., Nebl, T., Vukcevic, D., Moritz, R.L., Sargeant, T., Speed, T.P., Schofield, L., Crabb, B.S. (2006) Identification and stoichiometry of GPI-anchored membrane proteins of the human malaria parasite Plasmodium falciparum. Mol. Cell. Proteomics 5, 1286-1299.], is associated with parasite-derived detergent-resistant microdomains (DRMs). Pf34 is carried into the newly invaded ring, consistent with a role for Pf34 in the formation of the parasitophorous vacuole. Pf34 is exposed to the human immune system during infection and is recognised by human immune sera collected from residents of malaria endemic areas of Vietnam and Papua New Guinea.
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Affiliation(s)
- Nicholas I. Proellocks
- NHMRC Program in Malaria, Department of Microbiology, Monash University, VIC 3800, Australia
| | - Svetozar Kovacevic
- NHMRC Program in Malaria, Department of Microbiology, Monash University, VIC 3800, Australia
| | - David J.P. Ferguson
- Nuffield Department of Pathology, Oxford University, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom
| | - Lev M. Kats
- NHMRC Program in Malaria, Department of Microbiology, Monash University, VIC 3800, Australia
| | - Belinda J. Morahan
- NHMRC Program in Malaria, Department of Microbiology, Monash University, VIC 3800, Australia
| | - Casilda G. Black
- NHMRC Program in Malaria, Department of Microbiology, Monash University, VIC 3800, Australia
| | - Karena L. Waller
- NHMRC Program in Malaria, Department of Microbiology, Monash University, VIC 3800, Australia
| | - Ross L. Coppel
- NHMRC Program in Malaria, Department of Microbiology, Monash University, VIC 3800, Australia
- Victorian Bioinformatics Consortium, Monash University, VIC 3800, Australia
- Corresponding Author. Ross L. Coppel, Department of Microbiology, Monash University, VIC 3800, Australia., Tel.: +61 3 9905 4822; fax: +61 3 9905 4811., E-mail address:
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12
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Aboge GO, Jia H, Kuriki K, Zhou J, Nishikawa Y, Igarashi I, Fujisaki K, Suzuki H, Xuan X. Molecular characterization of a novel 32-kDa merozoite antigen of Babesia gibsoni with a better diagnostic performance by enzyme-linked immunosorbent assay. Parasitology 2007; 134:1185-94. [PMID: 17381888 DOI: 10.1017/s0031182007002594] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We cloned and expressed a novel gene encoding a 32-kDa merozoite protein of Babesia gibsoni (BgP32). The length of nucleotide sequence of the cDNA was 1464 bp with an open reading frame of 969 bp. The truncated recombinant BgP32 (rBgP32) without a signal peptide and C-terminal hydrophobic sequence was expressed in Escherichia coli as a soluble glutathione-S-transferase (GST) fusion protein. Western blotting demonstrated that the native protein was 32-kDa, consistent with molecular weight of the predicted mature polypeptide. Enzyme-linked immunosorbent assay (ELISA) using rBgP32 detected specific antibodies from 8 days to 541 days post-infection in the sequential sera from a dog experimentally infected with B. gibsoni. Moreover, the antigen did not cross-react with B. canis subspecies and closely related protozoan parasites, indicating that rBgP32 is a specific diagnostic antigen. Analysis of 47 sera taken from dogs with anaemic signs revealed that rBgP32 detected a higher proportion of B. gibsoni seropositive samples (77%) than its previously identified rBgP50 (68%) homologue. These results indicate that the BgP32 is a novel immunodominant antigen of B. gibsoni, and rBgP32 might be useful for diagnosis of B. gibsoni infection.
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Affiliation(s)
- G O Aboge
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan
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13
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Miska KB, Fetterer RH, Lillehoj HS, Jenkins MC, Allen PC, Harper SB. Characterisation of macrophage migration inhibitory factor from Eimeria species infectious to chickens☆. Mol Biochem Parasitol 2007; 151:173-83. [PMID: 17194492 DOI: 10.1016/j.molbiopara.2006.10.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Revised: 10/27/2006] [Accepted: 10/31/2006] [Indexed: 11/22/2022]
Abstract
Macrophage migration inhibitory factor (MIF) was the first cytokine to be identified almost 40 years ago. Homologues of MIF have been isolated recently from invertebrates, making it an interesting molecule from an evolutionary as well as functional perspective. The present study represents the first report of MIF homologues in apicomplexan parasites, belonging to the genus Eimeria. A single full-length clone was isolated from Eimeria acervulina that shared between 35 and 38% amino acid identity with MIFs of vertebrates. A MIF cDNA from Eimeria tenella shared 64% amino acid identity with E. acervulina MIF. The mRNA expression was highest in merozoites, whereas developing oocysts and sporozoites expressed low to undetectable levels. Protein expression patterns were nearly identical to that observed by reverse transcriptase polymerase chain reaction (RT-PCR), suggesting strong developmental regulation. Immunofluorescence staining and co-localisation studies of E. acervulina merozoites indicated that MIF is distributed throughout the cytosol, and appears to be concentrated in the apical end of the parasite. The presence of MIF was detected in excretory/secretory (ES) products collected from E. acervulina merozoites, and isoelectric focusing indicated that three MIF isoforms are present in this stage. Phylogenetic analysis revealed that apicomplexan MIF sequences form a sister relationship to MIF-like molecules from Arabidopsis thaliana.
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Affiliation(s)
- Katarzyna B Miska
- USDA/ARS, Animal Parasitic Diseases Laboratory, 10300 Baltimore Ave. BARC-East, Beltsville, MD 20705, USA.
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Stack CM, Lowther J, Cunningham E, Donnelly S, Gardiner DL, Trenholme KR, Skinner-Adams TS, Teuscher F, Grembecka J, Mucha A, Kafarski P, Lua L, Bell A, Dalton JP. Characterization of the Plasmodium falciparum M17 Leucyl Aminopeptidase. J Biol Chem 2007; 282:2069-80. [PMID: 17107951 DOI: 10.1074/jbc.m609251200] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amino acids generated from the catabolism of hemoglobin by intra-erythrocytic malaria parasites are not only essential for protein synthesis but also function in maintaining an osmotically stable environment, and creating a gradient by which amino acids that are rare or not present in hemoglobin are drawn into the parasite from host serum. We have proposed that a Plasmodium falciparum M17 leucyl aminopeptidase (PfLAP) generates and regulates the internal pool of free amino acids and therefore represents a target for novel antimalarial drugs. This enzyme has been expressed in insect cells as a functional 320-kDa homo-hexamer that is optimally active at neutral or alkaline pH, is dependent on metal ions for activity, and exhibits a substrate preference for N-terminally exposed hydrophobic amino acids, particularly leucine. PfLAP is produced by all stages in the intra-erythrocytic developmental cycle of malaria but was most highly expressed by trophozoites, a stage at which hemoglobin degradation and parasite protein synthesis are elevated. The enzyme was located by immunohistochemical methods and by transfecting malaria cells with a PfLAP-green fluorescent protein construct, to the cytosolic compartment of the cell at all developmental stages, including segregated merozoites. Amino acid dipeptide analogs, such as bestatin and its derivatives, are potent inhibitors of the protease and also block the growth of P. falciparum malaria parasites in culture. This study provides a biochemical basis for the antimalarial activity of aminopeptidase inhibitors. Availability of functionally active recombinant PfLAP, coupled with a simple enzymatic readout, will aid medicinal chemistry and/or high throughput approaches for the future design/discovery of new antimalarial drugs.
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Affiliation(s)
- Colin M Stack
- Institute for the Biotechnology of Infectious Diseases, University of Technology Sydney, Level 6, Building 4, Corner of Thomas and Harris Street, Ultimo, Sydney, New South Wales 2007, Australia
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