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Lyons FMT, Gabriela M, Tham WH, Dietrich MH. Plasmodium 6-Cysteine Proteins: Functional Diversity, Transmission-Blocking Antibodies and Structural Scaffolds. Front Cell Infect Microbiol 2022; 12:945924. [PMID: 35899047 PMCID: PMC9309271 DOI: 10.3389/fcimb.2022.945924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/22/2022] [Indexed: 11/30/2022] Open
Abstract
The 6-cysteine protein family is one of the most abundant surface antigens that are expressed throughout the Plasmodium falciparum life cycle. Many members of the 6-cysteine family have critical roles in parasite development across the life cycle in parasite transmission, evasion of the host immune response and host cell invasion. The common feature of the family is the 6-cysteine domain, also referred to as s48/45 domain, which is conserved across Aconoidasida. This review summarizes the current approaches for recombinant expression for 6-cysteine proteins, monoclonal antibodies against 6-cysteine proteins that block transmission and the growing collection of crystal structures that provide insights into the functional domains of this protein family.
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Affiliation(s)
- Frankie M. T. Lyons
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Mikha Gabriela
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Wai-Hong Tham
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Melanie H. Dietrich
- The Walter and Eliza Hall Institute of Medical Research, Infectious Diseases and Immune Defence Division, Parkville, VIC, Australia
- Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
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2
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de Jong RM, Tebeje SK, Meerstein‐Kessel L, Tadesse FG, Jore MM, Stone W, Bousema T. Immunity against sexual stage Plasmodium falciparum and Plasmodium vivax parasites. Immunol Rev 2020; 293:190-215. [PMID: 31840844 PMCID: PMC6973022 DOI: 10.1111/imr.12828] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 10/30/2019] [Accepted: 11/14/2019] [Indexed: 12/25/2022]
Abstract
The efficient spread of malaria from infected humans to mosquitoes is a major challenge for malaria elimination initiatives. Gametocytes are the only Plasmodium life stage infectious to mosquitoes. Here, we summarize evidence for naturally acquired anti-gametocyte immunity and the current state of transmission blocking vaccines (TBV). Although gametocytes are intra-erythrocytic when present in infected humans, developing Plasmodium falciparum gametocytes may express proteins on the surface of red blood cells that elicit immune responses in naturally exposed individuals. This immune response may reduce the burden of circulating gametocytes. For both P. falciparum and Plasmodium vivax, there is a solid evidence that antibodies against antigens present on the gametocyte surface, when co-ingested with gametocytes, can influence transmission to mosquitoes. Transmission reducing immunity, reducing the burden of infection in mosquitoes, is a well-acknowledged but poorly quantified phenomenon that forms the basis for the development of TBV. Transmission enhancing immunity, increasing the likelihood or intensity of transmission to mosquitoes, is more speculative in nature but is convincingly demonstrated for P. vivax. With the increased interest in malaria elimination, TBV and monoclonal antibodies have moved to the center stage of malaria vaccine development. Methodologies to prioritize and evaluate products are urgently needed.
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MESH Headings
- Antibodies, Blocking/immunology
- Antibodies, Protozoan/immunology
- Host-Parasite Interactions/immunology
- Humans
- Immunity
- Immunomodulation
- Life Cycle Stages
- Malaria Vaccines/immunology
- Malaria, Falciparum/immunology
- Malaria, Falciparum/parasitology
- Malaria, Falciparum/prevention & control
- Malaria, Falciparum/transmission
- Malaria, Vivax/immunology
- Malaria, Vivax/parasitology
- Malaria, Vivax/prevention & control
- Malaria, Vivax/transmission
- Plasmodium falciparum/growth & development
- Plasmodium falciparum/immunology
- Plasmodium vivax/growth & development
- Plasmodium vivax/immunology
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Affiliation(s)
- Roos M. de Jong
- Radboud Institute for Molecular Life SciencesRadboud University Medical CenterNijmegenThe Netherlands
| | | | - Lisette Meerstein‐Kessel
- Radboud Institute for Health SciencesRadboud University Medical CenterNijmegenThe Netherlands
- Centre for Molecular and Biomolecular InformaticsRadboud Institute for Molecular Life SciencesNijmegenThe Netherlands
| | - Fitsum G. Tadesse
- Armauer Hansen Research InstituteAddis AbabaEthiopia
- Radboud Institute for Health SciencesRadboud University Medical CenterNijmegenThe Netherlands
| | - Matthijs M. Jore
- Radboud Institute for Molecular Life SciencesRadboud University Medical CenterNijmegenThe Netherlands
| | - Will Stone
- Department of Immunology and InfectionLondon School of Hygiene and Tropical MedicineLondonUK
| | - Teun Bousema
- Radboud Institute for Health SciencesRadboud University Medical CenterNijmegenThe Netherlands
- Department of Immunology and InfectionLondon School of Hygiene and Tropical MedicineLondonUK
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3
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Mamedov T, Cicek K, Miura K, Gulec B, Akinci E, Mammadova G, Hasanova G. A Plant-Produced in vivo deglycosylated full-length Pfs48/45 as a Transmission-Blocking Vaccine Candidate against malaria. Sci Rep 2019; 9:9868. [PMID: 31285498 PMCID: PMC6614448 DOI: 10.1038/s41598-019-46375-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 06/27/2019] [Indexed: 12/25/2022] Open
Abstract
Pfs48/45 is a leading antigen candidate for a transmission blocking (TB) vaccine. However, efforts to produce affordable, safe and correctly folded full-length Pfs48/45 using different protein expression systems have not produced an antigen with satisfactory TB activity. Pfs48/45 has 16 cysteines involved in disulfide bond formation, and the correct formation is critical for proper folding and induction of TB antibodies. Moreover, Pfs48⁄45 is not a glycoprotein in the native hosts, but contains potential glycosylation sites, which are aberrantly glycosylated during expression in eukaryotic systems. Here, we demonstrate for the first time that full length, Endo H in vivo enzymatic deglycosylated Pfs48/45 antigen is produced at a high level in plants and is structurally stable at elevated temperatures. Sera from mice immunized with this antigen showed strong inhibition in SMFA. Thus, Endo H in vivo enzymatic deglycosylated Pfs48/45 is a promising candidate for the development of an affordable TB vaccine, which may have the potential to save millions.
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Affiliation(s)
- Tarlan Mamedov
- Akdeniz University, Department of Agricultural Biotechnology, Dumlupınar Boulevard 07058 Campus, Antalya, Turkey.
- Azerbaijan National Academy of Science, Department of Biology and Medical Science, 24 Istiglaliyyat Street, Baku, Azerbaijan.
| | - Kader Cicek
- Akdeniz University, Department of Agricultural Biotechnology, Dumlupınar Boulevard 07058 Campus, Antalya, Turkey
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, USA
| | - Burcu Gulec
- Akdeniz University, Department of Agricultural Biotechnology, Dumlupınar Boulevard 07058 Campus, Antalya, Turkey
| | - Ersin Akinci
- Akdeniz University, Department of Agricultural Biotechnology, Dumlupınar Boulevard 07058 Campus, Antalya, Turkey
| | - Gunay Mammadova
- Akdeniz University, Department of Agricultural Biotechnology, Dumlupınar Boulevard 07058 Campus, Antalya, Turkey
| | - Gulnara Hasanova
- Akdeniz University, Department of Agricultural Biotechnology, Dumlupınar Boulevard 07058 Campus, Antalya, Turkey
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4
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Othman AS, Lin JW, Franke-Fayard BM, Kroeze H, van Pul FJA, Chevalley-Maurel S, Ramesar J, Marin-Mogollon C, Jore MM, Morin MJ, Long CA, Sauerwein R, Birkett A, Miura K, Janse CJ, Khan SM. Expression of full-length Plasmodium falciparum P48/45 in P. berghei blood stages: A method to express and evaluate vaccine antigens. Mol Biochem Parasitol 2018; 224:44-49. [PMID: 30053393 PMCID: PMC11040549 DOI: 10.1016/j.molbiopara.2018.07.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/10/2018] [Accepted: 07/19/2018] [Indexed: 12/16/2022]
Abstract
The transmission-blocking vaccine candidate Pfs48/45 from the human malaria parasite Plasmodium falciparum is known to be difficult to express in heterologous systems, either as full-length protein or as correctly folded protein fragments that retain conformational epitopes. In this study we express full-length Pfs48/45 in the rodent parasite P. berghei. Pfs48/45 is expressed as a transgene under control of the strong P. berghei schizont-specific msp1 gene promoter (Pfs48/45@PbMSP1). Pfs48/45@PbMSP1 schizont-infected red blood cells produced full-length Pfs48/45 and the structural integrity of Pfs48/45 was confirmed using a panel of conformation-specific monoclonal antibodies that bind to different Pfs48/45 epitopes. Sera from mice immunized with transgenic Pfs48/45@PbMSP1 schizonts showed strong transmission-reducing activity in mosquitoes infected with P. falciparum using standard membrane feeding. These results demonstrate that transgenic rodent malaria parasites expressing human malaria antigens may be used as means to evaluate immunogenicity and functionality of difficult to express malaria vaccine candidate antigens.
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Affiliation(s)
- Ahmad Syibli Othman
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands; Faculty of Health Sciences, Universiti Sultan Zainal Abidin, Terengganu, Malaysia
| | - Jing-Wen Lin
- Division of Pediatric Infectious Diseases, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University and Collaboration Innovation Center, Chengdu, China
| | - Blandine M Franke-Fayard
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Hans Kroeze
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Fiona J A van Pul
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Séverine Chevalley-Maurel
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Jai Ramesar
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Catherin Marin-Mogollon
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Matthijs M Jore
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | - Carole A Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, NIH, Rockville, Maryland, USA
| | - Robert Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, NIH, Rockville, Maryland, USA
| | - Chris J Janse
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Shahid M Khan
- Leiden Malaria Research Group, Parasitology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.
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5
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Agrawal A, Bisharyan Y, Papoyan A, Bednenko J, Cardarelli J, Yao M, Clark T, Berkmen M, Ke N, Colussi P. Fusion to Tetrahymena thermophila granule lattice protein 1 confers solubility to sexual stage malaria antigens in Escherichia coli. Protein Expr Purif 2018; 153:7-17. [PMID: 30081196 PMCID: PMC6189453 DOI: 10.1016/j.pep.2018.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 07/31/2018] [Accepted: 08/02/2018] [Indexed: 11/30/2022]
Abstract
A transmission-blocking vaccine targeting the sexual stages of Plasmodium species could play a key role in eradicating malaria. Multiple studies have identified the P. falciparum proteins Pfs25 and Pfs48/45 as prime targets for transmission-blocking vaccines. Although significant advances have been made in recombinant expression of these antigens, they remain difficult to produce at large scale and lack strong immunogenicity as subunit antigens. We linked a self-assembling protein, granule lattice protein 1 (Grl1p), from the ciliated protozoan, Tetrahymena thermophila, to regions of the ectodomains of either Pfs25 or Pfs48/45. We found that resulting protein chimera could be produced in E. coli as nanoparticles that could be readily purified in soluble form. When produced in the E. coli SHuffle strain, fusion to Grl1p dramatically increased solubility of target antigens while at the same time directing the formation of particles with diameters centering on 38 and 25 nm depending on the antigen. In a number of instances, co-expression with chaperone proteins and induction at a lower temperature further increased expression and solubility. Based on Western blotting and ELISA analysis, Pfs25 and Pfs48/45 retained their transmission-blocking epitopes within E. coli-derived particles, and the particles themselves elicited strong antibody responses in rabbits when given with an aluminum-based adjuvant. Antibodies against Pfs25-containing nanoparticles blocked parasite transmission in standard membrane-feeding assays. In conclusion, fusion to Grl1p can act as a solubility enhancer for proteins with limited solubility while retaining correct folding, which may be useful for applications such as the production of vaccines and other biologics.
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Affiliation(s)
| | | | | | | | | | | | - Theodore Clark
- TetraGenetics Inc, Arlington, MA, USA; Department of Immunology and Microbiology, Cornell University, Ithaca, NY, USA
| | | | - Na Ke
- New England Biolabs, Ipswich, MA, USA
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6
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Singh SK, Roeffen W, Mistarz UH, Chourasia BK, Yang F, Rand KD, Sauerwein RW, Theisen M. Construct design, production, and characterization of Plasmodium falciparum 48/45 R0.6C subunit protein produced in Lactococcus lactis as candidate vaccine. Microb Cell Fact 2017; 16:97. [PMID: 28569168 PMCID: PMC5452637 DOI: 10.1186/s12934-017-0710-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 05/26/2017] [Indexed: 01/10/2023] Open
Abstract
Background The sexual stages of Plasmodium falciparum are responsible for the spread of the parasite in malaria endemic areas. The cysteine-rich Pfs48/45 protein, exposed on the surface of sexual stages, is one of the most advanced antigens for inclusion into a vaccine that will block transmission. However, clinical Pfs48/45 sub-unit vaccine development has been hampered by the inability to produce high yields of recombinant protein as the native structure is required for the induction of functional transmission-blocking (TB) antibodies. We have investigated a downstream purification process of a sub-unit (R0.6C) fragment representing the C-terminal 6-Cys domain of Pfs48/45 (6C) genetically fused to the R0 region (R0) of asexual stage Glutamate Rich Protein expressed in Lactococcus lactis. Results A series of R0.6C fusion proteins containing features, which aim to increase expression levels or to facilitate protein purification, were evaluated at small scale. None of these modifications affected the overall yield of recombinant protein. Consequently, R0.6C with a C-terminal his tag was used for upstream and downstream process development. A simple work-flow was developed consisting of batch fermentation followed by two purification steps. As such, the recombinant protein was purified to homogeneity. The composition of the final product was verified by HPLC, mass spectrometry, SDS-PAGE and Western blotting with conformation dependent antibodies against Pfs48/45. The recombinant protein induced high levels of functional TB antibodies in rats. Conclusions The established production and purification process of the R0.6C fusion protein provide a strong basis for further clinical development of this candidate transmission blocking malaria vaccine. Electronic supplementary material The online version of this article (doi:10.1186/s12934-017-0710-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Susheel K Singh
- Department for Congenital Disorders, Statens Serum Institut, Artillerivej 5, 2300, Copenhagen, Denmark.,Department of International Health, Immunology and Microbiology, Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Will Roeffen
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Ulrik H Mistarz
- Department of Pharmacy, University of Copenhagen, Copenhagen, Denmark
| | - Bishwanath Kumar Chourasia
- Department for Congenital Disorders, Statens Serum Institut, Artillerivej 5, 2300, Copenhagen, Denmark.,Department of International Health, Immunology and Microbiology, Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Fen Yang
- Department of Pharmacy, University of Copenhagen, Copenhagen, Denmark
| | - Kasper D Rand
- Department of Pharmacy, University of Copenhagen, Copenhagen, Denmark
| | - Robert W Sauerwein
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Michael Theisen
- Department for Congenital Disorders, Statens Serum Institut, Artillerivej 5, 2300, Copenhagen, Denmark. .,Department of International Health, Immunology and Microbiology, Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark. .,Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
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7
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Theisen M, Jore MM, Sauerwein R. Towards clinical development of a Pfs48/45-based transmission blocking malaria vaccine. Expert Rev Vaccines 2017; 16:329-336. [PMID: 28043178 DOI: 10.1080/14760584.2017.1276833] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION Malaria is a devastating vector-borne disease caused by the Plasmodium parasite, resulting in almost 0.5 million casualties per year. The parasite has a complex life-cycle that includes asexual replication in human red blood cells, causing symptomatic malaria, and sexual stages which are essential for the transmission to the mosquito vector. A vaccine targeting the sexual stages of the parasite and thus blocking transmission will be instrumental for the eradication of malaria. One of the leading transmission blocking vaccine candidates is the sexual stage antigen Pfs48/45. Areas covered: PubMed was searched to review the progress and future prospects for clinical development of a Pfs48/45-based subunit vaccine. We will focus on biological function, naturally acquired immunity, functional activity of specific antibodies, sequence diversity, production of recombinant protein and preclinical studies. Expert commentary: Pfs48/45 is one of the lead-candidates for a transmission blocking vaccine and should be further explored in clinical trials.
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Affiliation(s)
- Michael Theisen
- a Department for Congenital disorders , State Serum Institute , Copenhagen , Denmark.,b Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology , University of Copenhagen , Copenhagen , Denmark.,c Department of Infectious Diseases , Copenhagen University Hospital, Rigshospitalet , Copenhagen , Denmark
| | - Matthijs M Jore
- d Department of Medical Microbiology , Radboud University Medical Center , Nijmegen , The Netherlands
| | - Robert Sauerwein
- d Department of Medical Microbiology , Radboud University Medical Center , Nijmegen , The Netherlands
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8
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Datta D, Bansal GP, Gerloff DL, Ellefsen B, Hannaman D, Kumar N. Immunogenicity and malaria transmission reducing potency of Pfs48/45 and Pfs25 encoded by DNA vaccines administered by intramuscular electroporation. Vaccine 2017; 35:264-272. [PMID: 27912985 PMCID: PMC5192010 DOI: 10.1016/j.vaccine.2016.11.072] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2016] [Revised: 11/03/2016] [Accepted: 11/22/2016] [Indexed: 01/06/2023]
Abstract
Pfs48/45 and Pfs25 are leading candidates for the development of Plasmodium falciparum transmission blocking vaccines (TBV). Expression of Pfs48/45 in the erythrocytic sexual stages and presentation to the immune system during infection in the human host also makes it ideal for natural boosting. However, it has been challenging to produce a fully folded, functionally active Pfs48/45, using various protein expression platforms. In this study, we demonstrate that full-length Pfs48/45 encoded by DNA plasmids is able to induce significant transmission reducing immune responses. DNA plasmids encoding Pfs48/45 based on native (WT), codon optimized (SYN), or codon optimized and mutated (MUT1 and MUT2), to prevent any asparagine (N)-linked glycosylation were compared with or without intramuscular electroporation (EP). EP significantly enhanced antibody titers and transmission blocking activity elicited by immunization with SYN Pfs48/45 DNA vaccine. Mosquito membrane feeding assays also revealed improved functional immunogenicity of SYN Pfs48/45 (N-glycosylation sites intact) as compared to MUT1 or MUT2 Pfs48/45 DNA plasmids (all N-glycosylation sites mutated). Boosting with recombinant Pfs48/45 protein after immunization with each of the different DNA vaccines resulted in significant boosting of antibody response and improved transmission reducing capabilities of all four DNA vaccines. Finally, immunization with a combination of DNA plasmids (SYN Pfs48/45 and SYN Pfs25) also provides support for the possibility of combining antigens targeting different life cycle stages in the parasite during transmission through mosquitoes.
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Affiliation(s)
- Dibyadyuti Datta
- Department of Tropical Medicine, School of Public Health and Tropical Medicine and Vector-Borne Infectious Disease Research Center, Tulane University, New Orleans, LA, United States
| | - Geetha P Bansal
- Department of Tropical Medicine, School of Public Health and Tropical Medicine and Vector-Borne Infectious Disease Research Center, Tulane University, New Orleans, LA, United States
| | | | - Barry Ellefsen
- ICHOR Medical Systems Inc., San Diego, CA, United States
| | - Drew Hannaman
- ICHOR Medical Systems Inc., San Diego, CA, United States
| | - Nirbhay Kumar
- Department of Tropical Medicine, School of Public Health and Tropical Medicine and Vector-Borne Infectious Disease Research Center, Tulane University, New Orleans, LA, United States.
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9
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The s48/45 six-cysteine proteins: mediators of interaction throughout the Plasmodium life cycle. Int J Parasitol 2016; 47:409-423. [PMID: 27899328 DOI: 10.1016/j.ijpara.2016.10.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 10/01/2016] [Accepted: 10/05/2016] [Indexed: 01/05/2023]
Abstract
During their life cycle Plasmodium parasites rely upon an arsenal of proteins that establish key interactions with the host and vector, and between the parasite sexual stages, with the purpose of ensuring infection, reproduction and proliferation. Among these is a group of secreted or membrane-anchored proteins known as the six-cysteine (6-cys) family. This is a small but important family with only 14 members thus far identified, each stage-specifically expressed during the parasite life cycle. 6-cys proteins often localise at the parasite surface or interface with the host and vector, and are conserved in different Plasmodium species. The unifying feature of the family is the s48/45 domain, presumably involved in adhesion and structurally related to Ephrins, the ligands of Eph receptors. The most prominent s48/45 members are currently under functional investigation and are being pursued as vaccine candidates. In this review, we examine what is known about the 6-cys family, their structure and function, and discuss future research directions.
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10
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Roeffen W, Theisen M, van de Vegte-Bolmer M, van Gemert G, Arens T, Andersen G, Christiansen M, Sevargave L, Singh SK, Kaviraj S, Sauerwein R. Transmission-blocking activity of antibodies to Plasmodium falciparum GLURP.10C chimeric protein formulated in different adjuvants. Malar J 2015; 14:443. [PMID: 26552428 PMCID: PMC4640242 DOI: 10.1186/s12936-015-0972-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 10/27/2015] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Plasmodium falciparum is transmitted from person to person by Anopheles mosquitoes after completing its sexual reproductive cycle within the infected mosquito. An efficacious vaccine holds the potential to interrupt development of the parasite in the mosquito leading to control and possibly eradication of malaria. A multi-component, R0.10C, was developed comprising P. falciparum glutamate-rich protein (R0) fused in frame to a correctly folded fragment of Pfs48/45 (10C). Here, a series of novel adjuvants were screened for their ability to elicit transmission-blocking (TB) antibodies. METHODS The recombinant fusion protein R0.10C was produced in Lactococcus lactis and purified by affinity-chromatography on a monoclonal antibody (mAb 85RF45.1) against a major epitope for TB antibodies (epitope 1) harboured on R0.10C. Immune-purified R0.10C was mixed with a series of adjuvants and tested in mice and rats. RESULTS In general, all R0.10C formulations elicited high levels of antibodies recognizing native Pfs48/45 in macrogametes/zygotes. TB activity of anti-R0.10C antisera was assessed in the standard membrane-feeding assay (SMFA). Potency of different adjuvant/R0.10C combinations was tested in mice and rats using aluminium hydroxide (Alum), Alum with micellar and emulsion formulations of a synthetic TLR4 agonist, Glucopyranosyl Lipid Adjuvant (GLA), stable emulsion (SE)/GLA, AbISCO-100 and Freund's adjuvant (as reference). All formulations produced high antibody titres recognizing the native Pfs48/45 protein in macrogametes/zygotes. Interestingly, the GLA-Alum combination adjuvant was the most potent inducer of TB antibodies based on serum collected after two immunizations. In agreement with previous observations, biological activity in the SMFA correlated well with the level of anti-Pfs48/45 antibodies. CONCLUSION The combined data provide a strong basis for entering the next phase of clinical grade R0.10C production and testing.
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Affiliation(s)
- Will Roeffen
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands.
| | - Michael Theisen
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark. .,Department of International Health, Immunology, and Microbiology, Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark. .,Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
| | | | - GeertJan van Gemert
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands.
| | - Theo Arens
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands.
| | - Gorm Andersen
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark.
| | - Michael Christiansen
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark.
| | | | | | | | - Robert Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands.
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11
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Draper SJ, Angov E, Horii T, Miller LH, Srinivasan P, Theisen M, Biswas S. Recent advances in recombinant protein-based malaria vaccines. Vaccine 2015; 33:7433-43. [PMID: 26458807 PMCID: PMC4687528 DOI: 10.1016/j.vaccine.2015.09.093] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 09/05/2015] [Accepted: 09/28/2015] [Indexed: 01/03/2023]
Abstract
Protein-based vaccines remain the cornerstone approach for B cell and antibody induction against leading target malaria antigens. Advances in antigen selection, immunogen design and epitope-focusing are advancing the field. New heterologous expression platforms are enabling cGMP production of next-generation protein vaccines. Next-generation antigens, protein-based immunogens and virus-like particle (VLP) delivery platforms are in clinical development. Protein-based vaccines will form part of a highly effective multi-component/multi-stage/multi-antigen subunit formulation against malaria.
Plasmodium parasites are the causative agent of human malaria, and the development of a highly effective vaccine against infection, disease and transmission remains a key priority. It is widely established that multiple stages of the parasite's complex lifecycle within the human host and mosquito vector are susceptible to vaccine-induced antibodies. The mainstay approach to antibody induction by subunit vaccination has been the delivery of protein antigen formulated in adjuvant. Extensive efforts have been made in this endeavor with respect to malaria vaccine development, especially with regard to target antigen discovery, protein expression platforms, adjuvant testing, and development of soluble and virus-like particle (VLP) delivery platforms. The breadth of approaches to protein-based vaccines is continuing to expand as innovative new concepts in next-generation subunit design are explored, with the prospects for the development of a highly effective multi-component/multi-stage/multi-antigen formulation seeming ever more likely. This review will focus on recent progress in protein vaccine design, development and/or clinical testing for a number of leading malaria antigens from the sporozoite-, merozoite- and sexual-stages of the parasite's lifecycle–including PfCelTOS, PfMSP1, PfAMA1, PfRH5, PfSERA5, PfGLURP, PfMSP3, Pfs48/45 and Pfs25. Future prospects and challenges for the development, production, human delivery and assessment of protein-based malaria vaccines are discussed.
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Affiliation(s)
- Simon J Draper
- The Jenner Institute, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Headington, Oxford OX3 7DQ, UK.
| | - Evelina Angov
- Walter Reed Army Institute of Research, U. S. Military Malaria Research Program, Malaria Vaccine Branch, 503 Robert Grant Avenue, Silver Spring, MD 20910, USA
| | - Toshihiro Horii
- Department of Molecular Protozoology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 561-873, Japan
| | - Louis H Miller
- Malaria Cell Biology Section, Laboratory of Malaria and Vector Research, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Prakash Srinivasan
- Malaria Cell Biology Section, Laboratory of Malaria and Vector Research, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Michael Theisen
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark; Centre for Medical Parasitology at Department of International Health, Immunology, and Microbiology and Department of Infectious Diseases, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Sumi Biswas
- The Jenner Institute, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Headington, Oxford OX3 7DQ, UK
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12
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Comparative assessment of transmission-blocking vaccine candidates against Plasmodium falciparum. Sci Rep 2015; 5:11193. [PMID: 26063320 PMCID: PMC4463016 DOI: 10.1038/srep11193] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 04/23/2015] [Indexed: 02/08/2023] Open
Abstract
Malaria transmission-blocking vaccines (TBVs) target the development of Plasmodium parasites within the mosquito, with the aim of preventing malaria transmission from one infected individual to another. Different vaccine platforms, mainly protein-in-adjuvant formulations delivering the leading candidate antigens, have been developed independently and have reported varied transmission-blocking activities (TBA). Here, recombinant chimpanzee adenovirus 63, ChAd63, and modified vaccinia virus Ankara, MVA, expressing AgAPN1, Pfs230-C, Pfs25, and Pfs48/45 were generated. Antibody responses primed individually against all antigens by ChAd63 immunization in BALB/c mice were boosted by the administration of MVA expressing the same antigen. These antibodies exhibited a hierarchy of inhibitory activity against the NF54 laboratory strain of P. falciparum in Anopheles stephensi mosquitoes using the standard membrane feeding assay (SMFA), with anti-Pfs230-C and anti-Pfs25 antibodies giving complete blockade. The observed rank order of inhibition was replicated against P. falciparum African field isolates in A. gambiae in direct membrane feeding assays (DMFA). TBA achieved was IgG concentration dependent. This study provides the first head-to-head comparative analysis of leading antigens using two different parasite sources in two different vector species, and can be used to guide selection of TBVs for future clinical development using the viral-vectored delivery platform.
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Wu Y, Sinden RE, Churcher TS, Tsuboi T, Yusibov V. Development of malaria transmission-blocking vaccines: from concept to product. ADVANCES IN PARASITOLOGY 2015; 89:109-52. [PMID: 26003037 DOI: 10.1016/bs.apar.2015.04.001] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Despite decades of effort battling against malaria, the disease is still a major cause of morbidity and mortality. Transmission-blocking vaccines (TBVs) that target sexual stage parasite development could be an integral part of measures for malaria elimination. In the 1950s, Huff et al. first demonstrated the induction of transmission-blocking immunity in chickens by repeated immunizations with Plasmodium gallinaceum-infected red blood cells. Since then, significant progress has been made in identification of parasite antigens responsible for transmission-blocking activity. Recombinant technologies accelerated evaluation of these antigens as vaccine candidates, and it is possible to induce effective transmission-blocking immunity in humans both by natural infection and now by immunization with recombinant vaccines. This chapter reviews the efforts to produce TBVs, summarizes the current status and advances and discusses the remaining challenges and approaches.
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Affiliation(s)
- Yimin Wu
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, Rockville, MD, USA
| | | | - Thomas S Churcher
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
| | - Takafumi Tsuboi
- Division of Malaria Research, Ehime University, Matsuyama, Ehime, Japan
| | - Vidadi Yusibov
- Fraunhofer USA Center for Molecular Biotechnology, Newark, DE, USA
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Wang F, Wang X, Yu X, Fu L, Liu Y, Ma L, Zhai C. High-level expression of endo-β-N-acetylglucosaminidase H from Streptomyces plicatus in Pichia pastoris and its application for the deglycosylation of glycoproteins. PLoS One 2015; 10:e0120458. [PMID: 25781897 PMCID: PMC4362766 DOI: 10.1371/journal.pone.0120458] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 01/22/2015] [Indexed: 11/22/2022] Open
Abstract
Endo-β-N-acetylglucosaminidase H (Endo H, EC3.2.1.96) is a glycohydrolase that is widely used in the study of glycoproteins. The present study aimed to assess the effect of high-level endo-β-N-acetylglucosaminidase H expression in Pichia pastoris. The DNA coding sequence of this enzyme was optimized based on the codon usage bias of Pichia pastoris and synthesized through overlapping PCR. This novel gene was cloned into a pHBM905A vector and introduced into Pichia pastoris GS115 for secretary expression. The yield of the target protein reached approximately 397 mg/l after a 6-d induction with 1% (v/v) methanol in shake flasks, which is much higher than that observed upon heterologous expression in Escherichia coli and silkworm. This recombinant enzyme was purified and its enzymatic features were studied. Its specific activity was 461573 U/mg. Its optimum pH and temperature were pH 5.5 and 37°C, respectively. Moreover, our study showed that the N-linked glycan side-chains of several recombinant proteins expressed in Pichia pastoris can be efficiently removed through either the co-fermentation of this recombinant strain with strains expressing substrates or by mixing the cell culture supernatants of the endo-β-N-acetylglucosaminidase H expressing strain with strains expressing substrates after fermentation. This is the first report of high-level endo-β-N-acetylglucosaminidase H expression in Pichia pastoris and the application of this enzyme in the deglycosylation of raw glycoproteins heterologously expressed in Pichia pastoris using simplified methods.
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Affiliation(s)
- Fei Wang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, People’s Republic of China
| | - Xiaojuan Wang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, People’s Republic of China
| | - Xiaolan Yu
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, People’s Republic of China
| | - Lin Fu
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, People’s Republic of China
| | - Yunyun Liu
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, People’s Republic of China
| | - Lixin Ma
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, People’s Republic of China
- * E-mail: (LM); (CZ)
| | - Chao Zhai
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, People’s Republic of China
- * E-mail: (LM); (CZ)
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Singh SK, Roeffen W, Andersen G, Bousema T, Christiansen M, Sauerwein R, Theisen M. A Plasmodium falciparum 48/45 single epitope R0.6C subunit protein elicits high levels of transmission blocking antibodies. Vaccine 2015; 33:1981-6. [PMID: 25728318 DOI: 10.1016/j.vaccine.2015.02.040] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/11/2015] [Accepted: 02/15/2015] [Indexed: 10/23/2022]
Abstract
The sexual stage Pfs48/45 antigen is a well-established lead candidate for a transmission blocking (TB) vaccine because of its critical role in parasite fertilization. We have recently produced the carboxy-terminal 10C-fragment of Pfs48/45 containing three known epitopes for TB antibodies as a chimera with the N-terminal region of GLURP (R0). The resulting fusion protein elicited high titer TB antibodies in rodents. To increase the relatively low yield of correctly folded Pfs48/45 we have generated a series of novel chimera truncating the 10C-fragments to 6 cysteine residues containing sub-units (6C). All constructs harbor the major epitope I for TB antibodies. One of these sub-units (R0.6Cc), produced high yields of correctly folded conformers, which could be purified by a simple 2-step procedure. Purified R0.6Cc was stable and elicits high titer TB antibodies in rats. The yield, purity and stability of R0.6Cc allows for further clinical development.
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Affiliation(s)
- Susheel K Singh
- Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institut, Copenhagen, Denmark; Centre for Medical Parasitology at Department of International Health, Immunology, and Microbiology, University of Copenhagen, and Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Will Roeffen
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Gorm Andersen
- Centre for Medical Parasitology at Department of International Health, Immunology, and Microbiology, University of Copenhagen, and Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Immunology & Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Michael Christiansen
- Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institut, Copenhagen, Denmark
| | - Robert Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Michael Theisen
- Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institut, Copenhagen, Denmark; Centre for Medical Parasitology at Department of International Health, Immunology, and Microbiology, University of Copenhagen, and Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
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16
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Prokhnevsky A, Mamedov T, Leffet B, Rahimova R, Ghosh A, Mett V, Yusibov V. Development of a single-replicon miniBYV vector for co-expression of heterologous proteins. Mol Biotechnol 2015; 57:101-10. [PMID: 25280556 DOI: 10.1007/s12033-014-9806-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In planta production of recombinant proteins, including vaccine antigens and monoclonal antibodies, continues gaining acceptance. With the broadening range of target proteins, the need for vectors with higher performance is increasing. Here, we have developed a single-replicon vector based on beet yellows virus (BYV) that enables co-delivery of two target genes into the same host cell, resulting in transient expression of each target. This BYV vector maintained genetic stability during systemic spread throughout the host plant, Nicotiana benthamiana. Furthermore, we have engineered a miniBYV vector carrying the sequences encoding heavy and light chains of a monoclonal antibody (mAb) against protective antigen (PA) of Bacillius anthracis, and achieved the expression of the full-length functional anti-PA mAb at ~300 mg/kg of fresh leaf tissue. To demonstrate co-expression and functionality of two independent proteins, we cloned the sequences of the Pfs48/45 protein of Plasmodium falciparum and endoglycosidase F (PNGase F) from Flavobacterium meningosepticum into the miniBYV vector under the control of two subgenomic RNA promoters. Agroinfiltration of N. benthamiana with this miniBYV vector resulted in accumulation of biologically active Pfs48/45 that was devoid of N-linked glycosylation and had correct conformation and epitope display. Overall, our findings demonstrate that the new BYV-based vector is capable of co-expressing two functionally active recombinant proteins within the same host cell.
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Affiliation(s)
- Alex Prokhnevsky
- Fraunhofer USA Center for Molecular Biotechnology, 9 Innovation Way, Suite 200, Newark, DE, 19711, USA
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17
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Nikolaeva D, Draper SJ, Biswas S. Toward the development of effective transmission-blocking vaccines for malaria. Expert Rev Vaccines 2015; 14:653-80. [PMID: 25597923 DOI: 10.1586/14760584.2015.993383] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The continued global burden of malaria can in part be attributed to a complex lifecycle, with both human hosts and mosquito vectors serving as transmission reservoirs. In preclinical models of vaccine-induced immunity, antibodies to parasite sexual-stage antigens, ingested in the mosquito blood meal, can inhibit parasite survival in the insect midgut as judged by ex vivo functional studies such as the membrane feeding assay. In an era of renewed political momentum for malaria elimination and eradication campaigns, such observations have fueled support for the development and implementation of so-called transmission-blocking vaccines. While leading candidates are being evaluated using a variety of promising vaccine platforms, the field is also beginning to capitalize on global '-omics' data for the rational genome-based selection and unbiased characterization of parasite and mosquito proteins to expand the candidate list. This review covers the progress and prospects of these recent developments.
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Affiliation(s)
- Daria Nikolaeva
- The Jenner Institute, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Headington, Oxford OX3 7DQ, UK
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18
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Theisen M, Roeffen W, Singh SK, Andersen G, Amoah L, van de Vegte-Bolmer M, Arens T, Tiendrebeogo RW, Jones S, Bousema T, Adu B, Dziegiel MH, Christiansen M, Sauerwein R. A multi-stage malaria vaccine candidate targeting both transmission and asexual parasite life-cycle stages. Vaccine 2014; 32:2623-30. [DOI: 10.1016/j.vaccine.2014.03.020] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 02/28/2014] [Accepted: 03/05/2014] [Indexed: 11/27/2022]
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Crosnier C, Wanaguru M, McDade B, Osier FH, Marsh K, Rayner JC, Wright GJ. A library of functional recombinant cell-surface and secreted P. falciparum merozoite proteins. Mol Cell Proteomics 2013; 12:3976-86. [PMID: 24043421 PMCID: PMC3861738 DOI: 10.1074/mcp.o113.028357] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Malaria, an infectious disease caused by parasites of the Plasmodium genus, is one of the world's major public health concerns causing up to a million deaths annually, mostly because of P. falciparum infections. All of the clinical symptoms are associated with the blood stage of the disease, an obligate part of the parasite life cycle, when a form of the parasite called the merozoite recognizes and invades host erythrocytes. During erythrocyte invasion, merozoites are directly exposed to the host humoral immune system making the blood stage of the parasite a conceptually attractive therapeutic target. Progress in the functional and molecular characterization of P. falciparum merozoite proteins, however, has been hampered by the technical challenges associated with expressing these proteins in a biochemically active recombinant form. This challenge is particularly acute for extracellular proteins, which are the likely targets of host antibody responses, because they contain structurally critical post-translational modifications that are not added by some recombinant expression systems. Here, we report the development of a method that uses a mammalian expression system to compile a protein resource containing the entire ectodomains of 42 P. falciparum merozoite secreted and cell surface proteins, many of which have not previously been characterized. Importantly, we are able to recapitulate known biochemical activities by showing that recombinant MSP1-MSP7 and P12-P41 directly interact, and that both recombinant EBA175 and EBA140 can bind human erythrocytes in a sialic acid-dependent manner. Finally, we use sera from malaria-exposed immune adults to profile the relative immunoreactivity of the proteins and show that the majority of the antigens contain conformational (heat-labile) epitopes. We envisage that this resource of recombinant proteins will make a valuable contribution toward a molecular understanding of the blood stage of P. falciparum infections and facilitate the comparative screening of antigens as blood-stage vaccine candidates.
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Affiliation(s)
- Cécile Crosnier
- Cell Surface Signalling laboratory, Wellcome Trust Sanger Institute, Cambridge CB10 1HH, UK
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20
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Mamedov T, Yusibov V. In vivo deglycosylation of recombinant proteins in plants by co-expression with bacterial PNGase F. Bioengineered 2013; 4:338-42. [PMID: 23328084 PMCID: PMC3813534 DOI: 10.4161/bioe.23449] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 12/25/2012] [Accepted: 12/30/2012] [Indexed: 11/19/2022] Open
Abstract
At present, several eukaryotic expression systems including yeast, insect and mammalian cells and plants are used for the production of recombinant proteins. Proteins with potential N-glycosylation sites are efficiently glycosylated when expressed in these systems. However, the ability of the eukaryotic expression systems to glycosylate may be not desirable for some proteins. If target proteins that do not carry N-linked glycans in the native host contain potential N-linked glycosylation sites, they can be aberrantly glycosylated in the eukaryotic expression systems, thus, potentially impairing biological activity. Recently, we have developed a strategy of enzymatic deglycosylation of proteins in vivo by co-introducing bacterial PNGase F via agroinfiltration followed by transient expression in plants. (1) Here, we summarize our work on this topic and its potential implications.
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Affiliation(s)
- Tarlan Mamedov
- Fraunhofer USA Center for Molecular Biotechnology; Newark, DE USA
| | - Vidadi Yusibov
- Fraunhofer USA Center for Molecular Biotechnology; Newark, DE USA
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21
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Mamedov T, Ghosh A, Jones RM, Mett V, Farrance CE, Musiychuk K, Horsey A, Yusibov V. Production of non-glycosylated recombinant proteins in Nicotiana benthamiana plants by co-expressing bacterial PNGase F. PLANT BIOTECHNOLOGY JOURNAL 2012; 10:773-82. [PMID: 22520228 DOI: 10.1111/j.1467-7652.2012.00694.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Application of tools of molecular biology and genomics is increasingly leading towards the development of recombinant protein-based biologics. As such, it is leading to an increased diversity of targets that have important health applications and require more flexible approaches for expression because of complex post-translational modifications. For example, Plasmodium parasites may have complex post-translationally modified proteins such as Pfs48/45 that do not carry N-linked glycans (Exp. Parasitol. 1998; 90, 165.) but contain potential N-linked glycosylation sites that can be aberrantly glycosylated during expression in mammalian and plant systems. Therefore, it is important to develop strategies for producing non-glycosylated forms of these targets to preserve biological activity and native conformation. In this study, we are describing in vivo deglycosylation of recombinant N-glycosylated proteins as a result of their transient co-expression with bacterial PNGase F (Peptide: N-glycosidase F). In addition, we show that the recognition of an in vivo deglycosylated plant-produced malaria vaccine candidate, Pfs48F1, by monoclonal antibodies I, III and V raised against various epitopes (I, III and V) of native Pfs48/45 of Plasmodium falciparum, was significantly stronger compared to that of the glycosylated form of plant-produced Pfs48F1. To our knowledge, neither in vivo enzymatic protein deglycosylation has been previously achieved in any eukaryotic system, including plants, nor has bacterial PNGase F been expressed in the plant system. Thus, here, we report for the first time the expression in plants of an active bacterial enzyme PNGase F and the production of recombinant proteins of interest in a non-glycosylated form.
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Affiliation(s)
- Tarlan Mamedov
- Fraunhofer USA Center for Molecular Biotechnology, Newark, DE, USA.
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22
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Jones CS, Luong T, Hannon M, Tran M, Gregory JA, Shen Z, Briggs SP, Mayfield SP. Heterologous expression of the C-terminal antigenic domain of the malaria vaccine candidate Pfs48/45 in the green algae Chlamydomonas reinhardtii. Appl Microbiol Biotechnol 2012; 97:1987-95. [DOI: 10.1007/s00253-012-4071-7] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 03/28/2012] [Accepted: 03/29/2012] [Indexed: 12/18/2022]
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23
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Arredondo SA, Cai M, Takayama Y, MacDonald NJ, Anderson DE, Aravind L, Clore GM, Miller LH. Structure of the Plasmodium 6-cysteine s48/45 domain. Proc Natl Acad Sci U S A 2012; 109:6692-7. [PMID: 22493233 PMCID: PMC3340019 DOI: 10.1073/pnas.1204363109] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The s48/45 domain was first noted in Plasmodium proteins more than 15 y ago. Previously believed to be unique to Plasmodium, the s48/45 domain is present in other aconoidasidans. In Plasmodium, members of the s48/45 family of proteins are localized on the surface of the parasite in different stages, mostly by glycosylphosphatydylinositol-anchoring. Members such as P52 and P36 seem to play a role in invasion of hepatocytes, and Pfs230 and Pfs48/45 are involved in fertilization in the sexual stages and have been consistently studied as targets of transmission-blocking vaccines for years. In this report, we present the molecular structure for the s48/45 domain corresponding to the C-terminal domain of the blood-stage protein Pf12 from Plasmodium falciparum, obtained by NMR. Our results indicate that this domain is a β-sandwich formed by two sheets with a mixture of parallel and antiparallel strands. Of the six conserved cysteines, two pairs link the β-sheets by two disulfide bonds, and the third pair forms a bond outside the core. The structure of the s48/45 domain conforms well to the previously defined surface antigen 1 (SAG1)-related-sequence (SRS) fold observed in the SAG family of surface antigens found in Toxoplasma gondii. Despite extreme sequence divergence, remarkable spatial conservation of one of the disulfide bonds is observed, supporting the hypothesis that the domains have evolved from a common ancestor. Furthermore, a homologous domain is present in ephrins, raising the possibility that the precursor of the s48/45 and SRS domains emerged from an ancient transfer to Apicomplexa from metazoan hosts.
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Affiliation(s)
| | | | | | | | - D. Eric Anderson
- Mass Spectrometry Facility, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - L. Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894
| | | | - Louis H. Miller
- Laboratory of Malaria Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852
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Abstract
Nearly two-thirds of the proteins encoded by Plasmodium falciparum, the parasite that causes the most deadly form of malaria, are annotated as "hypothetical." The yeast two-hybrid assay, which requires no prior knowledge about the target protein, has great potential to provide functional information about these uncharacterized proteins. However, P. falciparum yeast two-hybrid screens are hampered by the poor expression of P. falciparum genes in yeast. AU-rich sequences in nascent P. falciparum transcripts resemble the 3' end processing sites in yeast mRNAs, and are prematurely cleaved and polyadenylated. In most cases, these aberrant messages are degraded and yield no protein. To overcome this limitation, we have developed methods to extensively fragment P. falciparum genes. Novel yeast two-hybrid vectors, in which auxotrophic markers are fused to the 3' ends of the cloned inserts, are employed to identify those gene fragments that are expressed in yeast. In this chapter, we provide detailed protocols for fragmenting P. falciparum genes, creating P. falciparum activation domain libraries, and performing P. falciparum yeast two-hybrid screens. Though focused on P. falciparum, the approaches described here are applicable to other organisms and are likely to be especially useful for those with AT-rich genomes, which are also likely to be poorly expressed in yeast.
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Affiliation(s)
- Douglas J LaCount
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA
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25
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Coutinho-Abreu IV, Ramalho-Ortigao M. Transmission blocking vaccines to control insect-borne diseases: a review. Mem Inst Oswaldo Cruz 2010; 105:1-12. [PMID: 20209323 DOI: 10.1590/s0074-02762010000100001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 12/17/2009] [Indexed: 11/22/2022] Open
Abstract
Insect-borne diseases are responsible for severe mortality and morbidity worldwide. As control of insect vector populations relies primarily on the use of insecticides, the emergence of insecticide resistance as well to unintended consequences of insecticide use pose significant challenges to their continued application. Novel approaches to reduce pathogen transmission by disease vectors are been attempted, including transmission-blocking vaccines (TBVs) thought to be a feasible strategy to reduce pathogen burden in endemic areas. TBVs aim at preventing the transmission of pathogens from infected to uninfected vertebrate host by targeting molecule(s) expressed on the surface of pathogens during their developmental phase within the insect vector or by targeting molecules expressed by the vectors. For pathogen-based molecules, the majority of the TBV candidates selected as well as most of the data available regarding the effectiveness of this approach come from studies using malaria parasites. However, TBV candidates also have been identified from midgut tissues of mosquitoes and sand flies. In spite of the successes achieved in the potential application of TBVs against insect-borne diseases, many significant barriers remain. In this review, many of the TBV strategies against insect-borne pathogens and their respective ramification with regards to the immune response of the vertebrate host are discussed.
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Affiliation(s)
- Iliano V Coutinho-Abreu
- Biology of Disease Vectors Laboratory, Department of Entomology, Kansas State University, Manhattan, KS 66506, USA
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Heterologous expression of plasmodial proteins for structural studies and functional annotation. Malar J 2008; 7:197. [PMID: 18828893 PMCID: PMC2567985 DOI: 10.1186/1475-2875-7-197] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Accepted: 10/01/2008] [Indexed: 11/10/2022] Open
Abstract
Malaria remains the world's most devastating tropical infectious disease with as many as 40% of the world population living in risk areas. The widespread resistance of Plasmodium parasites to the cost-effective chloroquine and antifolates has forced the introduction of more costly drug combinations, such as Coartem®. In the absence of a vaccine in the foreseeable future, one strategy to address the growing malaria problem is to identify and characterize new and durable antimalarial drug targets, the majority of which are parasite proteins. Biochemical and structure-activity analysis of these proteins is ultimately essential in the characterization of such targets but requires large amounts of functional protein. Even though heterologous protein production has now become a relatively routine endeavour for most proteins of diverse origins, the functional expression of soluble plasmodial proteins is highly problematic and slows the progress of antimalarial drug target discovery. Here the status quo of heterologous production of plasmodial proteins is presented, constraints are highlighted and alternative strategies and hosts for functional expression and annotation of plasmodial proteins are reviewed.
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Denis-Quanquin S, Lamouroux L, Lougarre A, Mahéo S, Saves I, Paquereau L, Demange P, Fournier D. Protein expression from synthetic genes: Selection of clones using GFP. J Biotechnol 2007; 131:223-30. [PMID: 17720272 DOI: 10.1016/j.jbiotec.2007.07.725] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 06/25/2007] [Accepted: 07/13/2007] [Indexed: 11/18/2022]
Abstract
Construction of synthetic genes is today the most elegant way to optimize the heterologous expression of a recombinant protein. However, the selection of positive clones that incorporate the correct synthetic DNA fragments is a bottleneck as current methods of gene synthesis introduce 3.5 nucleotide deletions per kb. Furthermore, even when all predictable optimizations for protein production have been introduced into the synthetic gene, production of the protein is often disappointing: protein is produced in too low amounts or end up in inclusion bodies. We propose a strategy to overcome these two problems simultaneously by cloning the synthetic gene upstream of a reporter gene. This permits the selection of clones devoid of frame-shift mutations. In addition, beside nucleotide deletion, an average of three non-neutral mutations per kb are introduced during gene synthesis. Using a reporter protein downstream of the synthetic gene, allows the selection of clones with random mutations improving the expression or the folding of the protein of interest. The problem of errors found in synthetic genes is then turned into an advantage since it provides polymorphism useful for molecular evolution. The use of synthetic genes appears as an alternative to the error-prone PCR strategy to generate the variations necessary in protein engineering experiments.
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Girard MP, Reed ZH, Friede M, Kieny MP. A review of human vaccine research and development: malaria. Vaccine 2006; 25:1567-80. [PMID: 17045367 DOI: 10.1016/j.vaccine.2006.09.074] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2006] [Accepted: 09/25/2006] [Indexed: 11/18/2022]
Abstract
The last several years have seen significant progress in the development of vaccines against malaria. Most recently, proof-of-concept of vaccine-induced protection from malaria infection and disease was demonstrated in African children. Pursued by various groups and on many fronts, several other candidate vaccines are in early clinical trials. Yet, despite the optimism and promise, an effective malaria vaccine is not yet available, in part because of the lack of understanding of the types of immune responses needed for protection, added to the difficulty of identifying, selecting and producing the appropriate protective antigens from a parasite with a genome of well over five thousand genes and to the frequent need to enhance the immunogenicity of purified antigens through the use of novel adjuvants or delivery systems. Insufficient clinical trial capacity and normative research functions such as local ethical committee reviews also contribute to slow down the development process. This article attempts to summarize the state of the art of malaria vaccine development.
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Affiliation(s)
- Marc P Girard
- University Paris 7, 39 rue Seignemartin, FR-69008 Lyon, France.
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Yuan P, Hendriks EF, Fernandez HR, O'Sullivan WJ, Stewart TS. Functional expression of the gene encoding cytidine triphosphate synthetase from Plasmodium falciparum which contains two novel sequences that are potential antimalarial targets. Mol Biochem Parasitol 2006; 143:200-8. [PMID: 16051382 DOI: 10.1016/j.molbiopara.2005.06.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2005] [Accepted: 06/03/2005] [Indexed: 11/27/2022]
Abstract
CTP synthetase (E C 6.3.4.2 UTP: ammonia ligase (ADP-forming)) catalyses the formation of CTP from UTP and, in the human parasite Plasmodium falciparum, is the sole source of cytidine nucleotides. It is thus a potential chemotherapeutic target, especially as the gene sequence indicated that the encoded GAT-domain of the enzyme contains two extended peptide segments (42aa and 223aa as compared to the host enzyme). Here, we circumvent the codon usage problems associated with the high A/T content of the P. falciparum sequence, especially evident in sequences encoding the extra peptides, to successfully express active recombinant P. falciparum CTP synthetase using preferred E. coli codons. This partially synthetic gene produced recombinant enzyme, containing the additional segments, which was functionally assayed for activity in vitro. We also show the native enzyme contains the additional peptides using immunoblots with antibodies derived from the recombinant protein. Confocal microscopy, using antibodies to the recombinant protein, provided evidence that the enzyme is expressed in vivo. This establishes for the first time that P. falciparum contain active CTP synthetase and that this enzyme contains two novel insert sequences in the functional enzyme.
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Affiliation(s)
- Ping Yuan
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
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Kirk K, Martin RE, Bröer S, Howitt SM, Saliba KJ. Plasmodium permeomics: membrane transport proteins in the malaria parasite. Curr Top Microbiol Immunol 2005; 295:325-56. [PMID: 16265897 DOI: 10.1007/3-540-29088-5_13] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Membrane transport proteins are integral membrane proteins that mediate the passage across the membrane bilayer of specific molecules and/or ions. Such proteins serve a diverse range of physiological roles, mediating the uptake of nutrients into cells, the removal of metabolic wastes and xenobiotics (including drugs), and the generation and maintenance of transmembrane electrochemical gradients. In this chapter we review the present state of knowledge of the membrane transport mechanisms underlying the cell physiology of the intraerythrocytic malaria parasite and its host cell, considering in particular physiological measurements on the parasite and parasitized erythrocyte, the annotation of transport proteins in the Plasmodium genome, and molecular methods used to analyze transport protein function.
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Affiliation(s)
- K Kirk
- School of Biochemistry and Molecular Biology, The Australian National University, 0200 Canberra, ACT, Australia.
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Gerloff DL, Creasey A, Maslau S, Carter R. Structural models for the protein family characterized by gamete surface protein Pfs230 of Plasmodium falciparum. Proc Natl Acad Sci U S A 2005; 102:13598-603. [PMID: 16155126 PMCID: PMC1224620 DOI: 10.1073/pnas.0502378102] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ps230 is the largest representative of a 10-member family of proteins found in all Plasmodium species. The family is defined by partially conserved, cysteine-rich double domains that are approximately 350 aa in length and have one to three predicted disulfide bridges in each half. In Plasmodium falciparum, the most dangerous human malaria, Pf12 is the smallest member of the family, comprising just one double domain. Pfs230, with 7 double domains, and Pfs48/45 and Pfs47, with 1.5 double domains each, are found on the gamete surfaces and are thus potential candidates for a transmission-blocking vaccine. Fold prediction analyses of the double domains in Pfs230 reveal structural resemblance to SAG1 (surface antigen 1), a surface protein with a double beta-sandwich structure from another apicomplexan parasite, Toxoplasma gondii. Template-directed modeling onto SAG1 clearly establishes the structural link between SAG1 and Pfs230 and produces positions for the cysteines that accord with the disulfide-bonding arrangement predicted for the Pfs230 family in earlier work. A highly clustered region of polymorphisms within the second double domain in Pfs230 maps to one side of the sandwich surface. This observation suggests that this region may be functional and reinforces the validity of these molecular models for the core domains of the Pfs230 family of proteins.
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Affiliation(s)
- Dietlind L Gerloff
- Institute of Structural and Molecular Biology, University of Edinburgh, EH9 3JR Edinburgh, United Kingdom.
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Zhang H, Howard EM, Roepe PD. Analysis of the antimalarial drug resistance protein Pfcrt expressed in yeast. J Biol Chem 2002; 277:49767-75. [PMID: 12351620 DOI: 10.1074/jbc.m204005200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in the novel membrane protein Pfcrt were recently found to be essential for chloroquine resistance (CQR) in Plasmodium falciparum, the parasite responsible for most lethal human malaria (Fidock, D. A., Nomura, T., Talley, A. K., Cooper, R. A., Dzekunov, S. M., Ferdig, M. T., Ursos, L. M., Sidhu, A. B., Naude, B., Deitsch, K. W., Su, X. Z., Wootton, J. C., Roepe, P. D., and Wellems, T. E. (2000) Mol. Cell 6, 861-871). Pfcrt is localized to the digestive vacuolar membrane of the intraerythrocytic parasite and may function as a transporter. Study of this putative transport function would be greatly assisted by overexpression in yeast followed by characterization of membrane vesicles. Unfortunately, the very high AT content of malarial genes precludes efficient heterologous expression. Thus, we back-translated Pfcrt to design idealized genes with preferred yeast codons, no long poly(A) sequences, and minimal stem-loop structure. We synthesized a designed gene with a two-step PCR method, fused this to N- and C-terminal sequences to aid membrane insertion and purification, and now report efficient expression of wild type and mutant Pfcrt proteins in the plasma membrane of Saccharomyces cerevisiae and Pichia pastoris yeast. To our knowledge, this is the first successful expression of a full-length malarial parasite integral membrane protein in yeast. Purified membranes and inside-out plasma membrane vesicle preparations were used to analyze wild type versus CQR-conferring mutant Pfcrt function, which may include effects on H(+) transport (Dzekunov, S., Ursos, L. M. B., and Roepe, P. D. (2000) Mol. Biochem. Parasitol. 110, 107-124), and to perfect a rapid purification of biotinylated Pfcrt. These data expand on the role of Pfcrt in conferring CQR and define a productive route for analysis of important P. falciparum transport proteins and membrane associated vaccine candidates.
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Affiliation(s)
- Hanbang Zhang
- Department of Chemistry, Lombardi Cancer Center, Georgetown University, 37th and O Streets, Washington, D. C. 20057-1227, USA
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Peterson DS, Gao Y, Asokan K, Gaertig J. The circumsporozoite protein of Plasmodium falciparum is expressed and localized to the cell surface in the free-living ciliate Tetrahymena thermophila. Mol Biochem Parasitol 2002; 122:119-26. [PMID: 12106865 DOI: 10.1016/s0166-6851(02)00079-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Heterologous expression is an important tool for characterization of protein function, structural studies, and production of antigen. While many different host systems have been utilized for the expression of Plasmodium falciparum proteins, the extreme AT-richness of its genome represents an obstacle to efficient expression. In addition, primary sequence motifs such as glycosyl phosphatidyl-inositol (GPI) cleavage/attachment sites of P. falciparum are not recognized in currently used expression hosts. Recently, DNA-mediated transformation has been used for expression of heterologous genes in the ciliated protozoan Tetrahymena thermophila. We report the stable expression of full-length P. falciparum circumsporozoite (CS) protein in T. thermophila. The expressed gene utilized the native CS protein N-terminal secretory signal sequence and the C-terminal GPI anchoring signal. Immunofluorescence imaging demonstrated that the CS protein was localized to the cell surface of Tetrahymena. Metabolic labeling with tritiated myristate resulted in incorporation of label into the recombinant CS protein, indicating that the protein was bound to the cell surface via a GPI anchor. This is the first report of the recognition of targeting and GPI anchoring signals of the P. falciparum CS protein in a heterologous expression host.
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Affiliation(s)
- David S Peterson
- Department of Medical Microbiology and Parasitology, University of Georgia, Athens 30602, USA.
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Abstract
Malaria is still a leading cause of morbidity and mortality in human populations. Problems, including drug-resistant parasites and insecticide resistant mosquitoes, ensure the continued hold of malaria in the tropics and sub-tropics. Each year around 100 million cases of malaria result in at least 50,000 deaths outside of sub-Saharan Africa; within sub-Saharan Africa itself, malaria causes around one million child deaths per year. New approaches for malaria control are badly needed and much effort has gone to develop malaria vaccines. In addition to giving personal protection, most such vaccines would also tend to reduce the transmission of malaria. One class of vaccine is being developed specifically for this purpose--the malaria transmission-blocking vaccines (TBV). TBVs are based upon antigens expressed on the surface of the sexual and mosquito mid-gut stages of malaria parasites. These antigens are the targets of antibodies induced by vaccination of the host and ingested with the parasites in a mosquito blood meal. The antibodies act by inhibiting the parasite's development within the mosquito itself and they thereby prevent the onward transmission of the parasites. TBVs could contribute to the total interruption of malaria transmission in many locations with relatively low transmission rates, mostly outside sub-Saharan Africa. Under almost all transmission rates, however, TBVs would help reduce malaria incidence and malaria-related morbidity and mortality. Promising recombinant TBV candidate antigens for the two main human malaria parasite species, Plasmodium falciparum and Plasmodium vivax, have been produced and tested in the laboratory; one has undergone early clinical trials.
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Affiliation(s)
- A Stowers
- Malaria Vaccine Development Unit, Laboratory of Parasitic Diseases, NIAID/NIH, 5640 Fishers Lane, Rockville, MD 20852, USA
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