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Ghosh A, Mishra A, Devi R, Narwal SK, Nirdosh, Srivastava PN, Mishra S. A Micronemal Protein, Scot1, Is Essential for Apicoplast Biogenesis and Liver Stage Development in Plasmodium berghei. ACS Infect Dis 2024; 10:3013-3025. [PMID: 39037752 DOI: 10.1021/acsinfecdis.4c00362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Plasmodium sporozoites invade hepatocytes, transform into liver stages, and replicate into thousands of merozoites that infect erythrocytes and cause malaria. Proteins secreted from micronemes play an essential role in hepatocyte invasion, and unneeded micronemes are subsequently discarded for replication. The liver-stage parasites are potent immunogens that prevent malarial infection. Late liver stage-arresting genetically attenuated parasites (GAPs) exhibit greater protective efficacy than early GAP. However, the number of late liver-stage GAPs for generating GAPs with multiple gene deletions is limited. Here, we identified Scot1 (Sporozoite Conserved Orthologous Transcript 1), which was previously shown to be upregulated in sporozoites, and by endogenous tagging with mCherry, we demonstrated that it is expressed in the sporozoite and liver stages in micronemes. Using targeted gene deletion in Plasmodium berghei, we showed that Scot1 is essential for late liver-stage development. Scot1 KO sporozoites grew normally into liver stages but failed to initiate blood-stage infection in mice due to impaired apicoplast biogenesis and merozoite formation. Bioinformatic studies suggested that Scot1 is a metal-small-molecule carrier protein. Remarkably, supplementation with metals in the culture of infected Scot1 KO cells did not rescue their phenotype. Immunization with Scot1 KO sporozoites in C57BL/6 mice confers protection against malaria via infection. These proof-of-concept studies will enable the generation of P. falciparum Scot1 mutants that could be exploited to generate GAP malaria vaccines.
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Affiliation(s)
- Ankit Ghosh
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Akancha Mishra
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Raksha Devi
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Sunil Kumar Narwal
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Nirdosh
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Pratik Narain Srivastava
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Satish Mishra
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Nirdosh, Shukla H, Mishra S. An ApiAp2 Transcription Factor with a Dispensable Role in Plasmodium berghei Life Cycle. ACS Infect Dis 2024; 10:1904-1913. [PMID: 38752809 DOI: 10.1021/acsinfecdis.4c00240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
Malaria parasites have a complex life cycle and undergo replication and population expansion within vertebrate hosts and mosquito vectors. These developmental transitions rely on changes in gene expression and chromatin reorganization that result in the activation and silencing of stage-specific genes. The ApiAp2 family of DNA-binding proteins plays an important role in regulating gene expression in malaria parasites. Here, we characterized the ApiAp2 protein in Plasmodium berghei, which we termed Ap2-D. In silico analysis revealed that Ap2-D has three beta-sheets followed by a helix at the C-terminus for DNA binding. Using gene tagging with 3XHA-mCherry, we found that Ap2-D is expressed in Plasmodium blood stages and is present in the parasite cytoplasm and nucleus. Surprisingly, our gene deletion study revealed a completely dispensable role for Ap2-D in the entirety of the P. berghei life cycle. Ap2-D KO parasites were found to grow in the blood successfully and progress through the mosquito midgut and salivary glands. Sporozoites isolated from mosquito salivary glands were infective for hepatocytes and achieved similar patency as WT in mice. We emphasize the importance of genetic validation of antimalarial drug targets before progressing them to drug discovery.
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Affiliation(s)
- Nirdosh
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Himadri Shukla
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Satish Mishra
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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3
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Nicholas J, Kolli SK, Subramani PA, De SL, Ogbondah MM, Barnes SJ, Ntumngia FB, Adams JH. Comparative analyses of functional antibody-mediated inhibition with anti-circumsporozoite monoclonal antibodies against transgenic Plasmodium berghei. Malar J 2023; 22:335. [PMID: 37936181 PMCID: PMC10629016 DOI: 10.1186/s12936-023-04765-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 10/24/2023] [Indexed: 11/09/2023] Open
Abstract
BACKGROUND Acquired functional inhibitory antibodies are one of several humoral immune mechanisms used to neutralize foreign pathogens. In vitro bioassays are useful tools for quantifying antibody-mediated inhibition and evaluating anti-parasite immune antibodies. However, a gap remains in understanding of how antibody-mediated inhibition in vitro translates to inhibition in vivo. In this study, two well-characterized transgenic Plasmodium berghei parasite lines, PbmCh-luc and Pb-PfCSP(r), and murine monoclonal antibodies (mAbs) specific to P. berghei and Plasmodium falciparum circumsporozoite protein (CSP), 3D11 and 2A10, respectively, were used to evaluate antibody-mediated inhibition of parasite development in both in vitro and in vivo functional assays. METHODS IC50 values of mAbs were determined using an established inhibition of liver-stage development assay (ILSDA). For the in vivo inhibition assay, mice were passively immunized by transfer of the mAbs and subsequently challenged with 5.0 × 103 sporozoites via tail vein injection. The infection burden in both assays was quantified by luminescence and qRT-PCR of P. berghei 18S rRNA normalized to host GAPDH. RESULTS The IC50 values quantified by relative luminescence of mAbs 3D11 and 2A10 were 0.396 µg/ml and 0.093 µg/ml, respectively, against transgenic lines in vitro. Using the highest (> 90%) inhibitory antibody concentrations in a passive transfer, an IC50 of 233.8 µg/ml and 181.5 µg/ml for mAbs 3D11 and 2A10, respectively, was observed in vivo. At 25 µg (250 µg/ml), the 2A10 antibody significantly inhibited liver burden in mice compared to control. Additionally, qRT-PCR of P. berghei 18S rRNA served as a secondary validation of liver burden quantification. CONCLUSIONS Results from both experimental models, ILSDA and in vivo challenge, demonstrated that increased concentrations of the homologous anti-CSP repeat mAbs increased parasite inhibition. However, differences in antibody IC50 values between parasite lines did not allow a direct correlation between the inhibition of sporozoite invasion in vitro by ILSDA and the inhibition of mouse liver stage burden. Further studies are needed to establish the conditions for confident predictions for the in vitro ILSDA to be a predictor of in vivo outcomes using this model system.
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Affiliation(s)
- Justin Nicholas
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, 33612, USA
| | - Surendra Kumar Kolli
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Pradeep Annamalai Subramani
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Sai Lata De
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
- Department of Infectious Disease & Immunology, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Madison M Ogbondah
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Samantha J Barnes
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - Francis Babila Ntumngia
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA
| | - John H Adams
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa, FL, 33612, USA.
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Mishra A, Varshney A, Mishra S. Regulation of Atg8 membrane deconjugation by cysteine proteases in the malaria parasite Plasmodium berghei. Cell Mol Life Sci 2023; 80:344. [PMID: 37910326 PMCID: PMC11073460 DOI: 10.1007/s00018-023-05004-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 09/22/2023] [Accepted: 10/16/2023] [Indexed: 11/03/2023]
Abstract
During macroautophagy, the Atg8 protein is conjugated to phosphatidylethanolamine (PE) in autophagic membranes. In Apicomplexan parasites, two cysteine proteases, Atg4 and ovarian tumor unit (Otu), have been identified to delipidate Atg8 to release this protein from membranes. Here, we investigated the role of cysteine proteases in Atg8 conjugation and deconjugation and found that the Plasmodium parasite consists of both activities. We successfully disrupted the genes individually; however, simultaneously, they were refractory to deletion and essential for parasite survival. Mutants lacking Atg4 and Otu showed normal blood and mosquito stage development. All mice infected with Otu KO sporozoites became patent; however, Atg4 KO sporozoites either failed to establish blood infection or showed delayed patency. Through in vitro and in vivo analysis, we found that Atg4 KO sporozoites invade and normally develop into early liver stages. However, nuclear and organelle differentiation was severely hampered during late stages and failed to mature into hepatic merozoites. We found a higher level of Atg8 in Atg4 KO parasites, and the deconjugation of Atg8 was hampered. We confirmed Otu localization on the apicoplast; however, parasites lacking Otu showed no visible developmental defects. Our data suggest that Atg4 is the primary deconjugating enzyme and that Otu cannot replace its function completely because it cleaves the peptide bond at the N-terminal side of glycine, thereby irreversibly inactivating Atg8 during its recycling. These findings highlight a role for the Atg8 deconjugation pathway in organelle biogenesis and maintenance of the homeostatic cellular balance.
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Affiliation(s)
- Akancha Mishra
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Aastha Varshney
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Satish Mishra
- Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
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Nicholas J, De SL, Thawornpan P, Brashear AM, Kolli SK, Subramani PA, Barnes SJ, Cui L, Chootong P, Ntumngia FB, Adams JH. Preliminary characterization of Plasmodium vivax sporozoite antigens as pre-erythrocytic vaccine candidates. PLoS Negl Trop Dis 2023; 17:e0011598. [PMID: 37703302 PMCID: PMC10519608 DOI: 10.1371/journal.pntd.0011598] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 09/25/2023] [Accepted: 08/15/2023] [Indexed: 09/15/2023] Open
Abstract
Plasmodium vivax pre-erythrocytic (PE) vaccine research has lagged far behind efforts to develop Plasmodium falciparum vaccines. There is a critical gap in our knowledge of PE antigen targets that can induce functionally inhibitory neutralizing antibody responses. To overcome this gap and guide the selection of potential PE vaccine candidates, we considered key characteristics such as surface exposure, essentiality to infectivity and liver stage development, expression as recombinant proteins, and functional immunogenicity. Selected P. vivax sporozoite antigens were surface sporozoite protein 3 (SSP3), sporozoite microneme protein essential for cell traversal (SPECT1), sporozoite surface protein essential for liver-stage development (SPELD), and M2 domain of MAEBL. Sequence analysis revealed little variation occurred in putative B-cell and T-cell epitopes of the PE candidates. Each antigen was tested for expression as refolded recombinant proteins using an established bacterial expression platform and only SPELD failed. The successfully expressed antigens were immunogenic in vaccinated laboratory mice and were positively reactive with serum antibodies of P. vivax-exposed residents living in an endemic region in Thailand. Vaccine immune antisera were tested for reactivity to native sporozoite proteins and for their potential vaccine efficacy using an in vitro inhibition of liver stage development assay in primary human hepatocytes quantified on day 6 post-infection by high content imaging analysis. The anti-PE sera produced significant inhibition of P. vivax sporozoite invasion and liver stage development. This report provides an initial characterization of potential new PE candidates for a future P. vivax vaccine.
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Affiliation(s)
- Justin Nicholas
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Sai Lata De
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Pongsakorn Thawornpan
- Department of Clinical Microbiology and Applied Technology, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand
| | - Awtum M. Brashear
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Surendra Kumar Kolli
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Pradeep Annamalai Subramani
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Samantha J. Barnes
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Liwang Cui
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Patchanee Chootong
- Department of Clinical Microbiology and Applied Technology, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand
| | - Francis Babila Ntumngia
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - John H. Adams
- Center for Global Health and Interdisciplinary Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
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Tanneru N, Nivya MA, Adhikari N, Saxena K, Rizvi Z, Sudhakar R, Nagwani AK, Atul, Mohammed Abdul Al-Nihmi F, Kumar KA, Sijwali PS. Plasmodium DDI1 is a potential therapeutic target and important chromatin-associated protein. Int J Parasitol 2023; 53:157-175. [PMID: 36657610 DOI: 10.1016/j.ijpara.2022.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 10/13/2022] [Accepted: 11/10/2022] [Indexed: 01/18/2023]
Abstract
DNA damage inducible 1 protein (DDI1) is involved in a variety of cellular processes including proteasomal degradation of specific proteins. All DDI1 proteins contain a ubiquitin-like (UBL) domain and a retroviral protease (RVP) domain. Some DDI1 proteins also contain a ubiquitin-associated (UBA) domain. The three domains confer distinct activities to DDI1 proteins. The presence of a RVP domain makes DDI1 a potential target of HIV protease inhibitors, which also block the development of malaria parasites. Hence, we investigated the DDI1 of malaria parasites to identify its roles during parasite development and potential as a therapeutic target. DDI1 proteins of Plasmodium and other apicomplexan parasites share the UBL-RVP domain architecture, and some also contain the UBA domain. Plasmodium DDI1 is expressed across all the major life cycle stages and is important for parasite survival, as conditional depletion of DDI1 protein in the mouse malaria parasite Plasmodium berghei and the human malaria parasite Plasmodium falciparum compromised parasite development. Infection of mice with DDI1 knock-down P. berghei was self-limiting and protected the recovered mice from subsequent infection with homologous as well as heterologous parasites, indicating the potential of DDI1 knock-down parasites as a whole organism vaccine. Plasmodium falciparum DDI1 (PfDDI1) is associated with chromatin and DNA-protein crosslinks. PfDDI1-depleted parasites accumulated DNA-protein crosslinks and showed enhanced susceptibility to DNA-damaging chemicals, indicating a role of PfDDI1 in removal of DNA-protein crosslinks. Knock-down of PfDDI1 increased susceptibility to the retroviral protease inhibitor lopinavir and antimalarial artemisinin, which suggests that simultaneous inhibition of DDI1 could potentiate antimalarial activity of these drugs. As DDI1 knock-down parasites confer protective immunity and it could be a target of HIV protease inhibitors, Plasmodium DDI1 is a potential therapeutic target for malaria control.
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Affiliation(s)
- Nandita Tanneru
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India
| | - M Angel Nivya
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India
| | - Navin Adhikari
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India
| | - Kanika Saxena
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, UP, India
| | - Zeba Rizvi
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India
| | - Renu Sudhakar
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India
| | - Amit Kumar Nagwani
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India
| | - Atul
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India
| | | | - Kota Arun Kumar
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | - Puran Singh Sijwali
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, TS, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, UP, India.
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Targetome Analysis of Malaria Sporozoite Transcription Factor AP2-Sp Reveals Its Role as a Master Regulator. mBio 2023; 14:e0251622. [PMID: 36622145 PMCID: PMC9973277 DOI: 10.1128/mbio.02516-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Malaria transmission to humans begins with sporozoite infection of the liver. The elucidation of gene regulation during the sporozoite stage will promote the investigation of mechanisms of liver infection by this parasite and contribute to the development of strategies for preventing malaria transmission. AP2-Sp is a transcription factor (TF) essential for the formation of sporozoites or sporogony, which takes place in oocysts in the midguts of infected mosquitoes. To understand the role of this TF in the transcriptional regulatory system of this stage, we performed chromatin immunoprecipitation sequencing (ChIP-seq) analyses using whole mosquito midguts containing late oocysts as starting material and explored its genome-wide target genes. We identified 697 target genes, comprising those involved in distinct processes parasites experience during this stage, from sporogony to development into the liver stage and representing the majority of genes highly expressed in the sporozoite stage. These results suggest that AP2-Sp determines basal patterns of gene expression by targeting a broad range of genes directly. The ChIP-seq analyses also showed that AP2-Sp maintains its own expression by a transcriptional autoactivation mechanism (positive-feedback loop) and induces all TFs reported to be transcribed at this stage, including AP2-Sp2, AP2-Sp3, and SLARP. The results showed that AP2-Sp exists at the top of the transcriptional cascade of this stage and triggers the formation of this stage as a master regulator. IMPORTANCE The sporozoite stage plays a central role in malaria transmission from a mosquito to vertebrate host and is an important target for antimalarial strategies. AP2-Sp is a candidate master transcription factor for the sporozoite stage. However, study of its role in gene regulation has been hampered because of difficulties in performing genome-wide studies of gene regulation in this stage. Here, we conquered this problem and revealed that AP2-Sp has the following prominent features as a master transcription factor. First, it determines the repertory of gene expression during this stage. Second, it maintains its own expression through a transcriptional positive-feedback loop and induces all other transcription factors specifically expressed in this stage. This study represents a major breakthrough in fully understanding gene regulation in this important malarial stage.
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Ruberto AA, Bourke C, Vantaux A, Maher SP, Jex A, Witkowski B, Snounou G, Mueller I. Single-cell RNA sequencing of Plasmodium vivax sporozoites reveals stage- and species-specific transcriptomic signatures. PLoS Negl Trop Dis 2022; 16:e0010633. [PMID: 35926062 PMCID: PMC9380936 DOI: 10.1371/journal.pntd.0010633] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 08/16/2022] [Accepted: 07/04/2022] [Indexed: 11/24/2022] Open
Abstract
Background Plasmodium vivax sporozoites reside in the salivary glands of a mosquito before infecting a human host and causing malaria. Previous transcriptome-wide studies in populations of these parasite forms were limited in their ability to elucidate cell-to-cell variation, thereby masking cellular states potentially important in understanding malaria transmission outcomes. Methodology/Principal findings In this study, we performed transcription profiling on 9,947 P. vivax sporozoites to assess the extent to which they differ at single-cell resolution. We show that sporozoites residing in the mosquito’s salivary glands exist in distinct developmental states, as defined by their transcriptomic signatures. Additionally, relative to P. falciparum, P. vivax displays overlapping and unique gene usage patterns, highlighting conserved and species-specific gene programs. Notably, distinguishing P. vivax from P. falciparum were a subset of P. vivax sporozoites expressing genes associated with translational regulation and repression. Finally, our comparison of single-cell transcriptomic data from P. vivax sporozoite and erythrocytic forms reveals gene usage patterns unique to sporozoites. Conclusions/Significance In defining the transcriptomic signatures of individual P. vivax sporozoites, our work provides new insights into the factors driving their developmental trajectory and lays the groundwork for a more comprehensive P. vivax cell atlas. Plasmodium vivax is the second most common cause of malaria worldwide. It is particularly challenging for malaria elimination as it forms both active blood-stage infections, as well as asymptomatic liver-stage infections that can persist for extended periods of time. The activation of persister forms in the liver (hypnozoites) are responsible for relapsing infections occurring weeks or months following primary infection via a mosquito bite. How P. vivax persists in the liver remains a major gap in understanding of this organism. It has been hypothesized that there is pre-programming of the infectious sporozoite while it is in the salivary-glands that determines if the cell’s fate once in the liver is to progress towards immediate liver stage development or persist for long-periods as a hypnozoite. The aim of this study was to see if such differences were distinguishable at the transcript level in salivary-gland sporozoites. While we found significant variation amongst sporozoites, we did not find clear evidence that they are transcriptionally pre-programmed as has been suggested. Nevertheless, we highlight several intriguing patterns that appear to be P. vivax specific relative to non-relapsing species that cause malaria prompting further investigation.
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Affiliation(s)
- Anthony A. Ruberto
- Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France
| | - Caitlin Bourke
- Division of Population Health and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Kingdom of Cambodia
| | - Steven P. Maher
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Aaron Jex
- Division of Population Health and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Kingdom of Cambodia
| | - Georges Snounou
- Commissariat à l’Énergie Atomique et aux Énergies Alternatives-Université Paris Sud 11-INSERM U1184, Immunology of Viral Infections and Autoimmune Diseases (IMVA-HB), Infectious Disease Models and Innovative Therapies (IDMIT) Department, Institut de Biologie François Jacob (IBFJ), Direction de la Recherche Fondamentale (DRF), Fontenay-aux-Roses, France
| | - Ivo Mueller
- Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France
- Division of Population Health and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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Narwal SK, Nayak B, Mehra P, Mishra S. Protein kinase 9 is not required for completion of the Plasmodium berghei life cycle. Microbiol Res 2022; 260:127051. [DOI: 10.1016/j.micres.2022.127051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 04/11/2022] [Accepted: 04/20/2022] [Indexed: 10/18/2022]
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10
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Disrupting a Plasmodium berghei putative phospholipase impairs efficient egress of merosomes. Int J Parasitol 2022; 52:547-558. [DOI: 10.1016/j.ijpara.2022.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 03/09/2022] [Accepted: 03/21/2022] [Indexed: 01/23/2023]
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Singh D, Patri S, Narahari V, Segireddy RR, Dey S, Saurabh A, Macha V, Prabhu NP, Srivastava A, Kolli SK, Kota AK. A Conserved Plasmodium Structural Integrity Maintenance Protein (SIMP) is associated with sporozoite membrane and is essential for maintaining shape and infectivity. Mol Microbiol 2022; 117:1324-1339. [PMID: 35301756 DOI: 10.1111/mmi.14894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 03/07/2022] [Accepted: 03/08/2022] [Indexed: 11/27/2022]
Abstract
Plasmodium sporozoites are extracellular forms introduced during mosquito bite that selectively invade mammalian hepatocytes. Sporozoites are delimited by a cell membrane that is linked to the underlying acto-myosin molecular motor. While membrane proteins with roles in motility and invasion have been well studied, very little is known about proteins that maintain the sporozoite shape. We demonstrate that in Plasmodium berghei (Pb) a conserved hypothetical gene, PBANKA_1422900 specifies sporozoite structural integrity maintenance protein (SIMP) required for maintaining the sporozoite shape and motility. Sporozoites lacking SIMP exhibited loss of regular shape, extensive membrane blebbing at multiple foci and membrane detachment. The mutant sporozoites failed to infect hepatocytes, though the altered shape did not affect the organisation of cytoskeleton or inner membrane complex (IMC). Interestingly, the components of IMC failed to extend under the membrane blebs likely suggesting that SIMP may assist in anchoring the membrane to IMC. Endogenous C-terminal HA tagging localized SIMP to membrane and revealed the C-terminus of the protein to be extracellular. Since SIMP is highly conserved amongst Plasmodium species, these findings have important implications for utilising it as a novel sporozoite specific vaccine candidate.
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Affiliation(s)
- Dipti Singh
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Smita Patri
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Veeda Narahari
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Rameswara R Segireddy
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Sandeep Dey
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Archi Saurabh
- Department of Biotechnology & Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Vijay Macha
- National Institute of Animal Biotechnology, Gachibowli, Hyderabad, 500032, India
| | - N Prakash Prabhu
- Department of Biotechnology & Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Anand Srivastava
- National Institute of Animal Biotechnology, Gachibowli, Hyderabad, 500032, India
| | - Surendra Kumar Kolli
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Arun Kumar Kota
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
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12
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Kolli SK, Salman AM, Ramesar J, Chevalley-Maurel S, Kroeze H, Geurten FGA, Miyazaki S, Mukhopadhyay E, Marin-Mogollon C, Franke-Fayard B, Hill AVS, Janse CJ. Screening of viral-vectored P. falciparum pre-erythrocytic candidate vaccine antigens using chimeric rodent parasites. PLoS One 2021; 16:e0254498. [PMID: 34252120 PMCID: PMC8274855 DOI: 10.1371/journal.pone.0254498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/28/2021] [Indexed: 11/19/2022] Open
Abstract
To screen for additional vaccine candidate antigens of Plasmodium pre-erythrocytic stages, fourteen P. falciparum proteins were selected based on expression in sporozoites or their role in establishment of hepatocyte infection. For preclinical evaluation of immunogenicity of these proteins in mice, chimeric P. berghei sporozoites were created that express the P. falciparum proteins in sporozoites as an additional copy gene under control of the uis4 gene promoter. All fourteen chimeric parasites produced sporozoites but sporozoites of eight lines failed to establish a liver infection, indicating a negative impact of these P. falciparum proteins on sporozoite infectivity. Immunogenicity of the other six proteins (SPELD, ETRAMP10.3, SIAP2, SPATR, HT, RPL3) was analyzed by immunization of inbred BALB/c and outbred CD-1 mice with viral-vectored (ChAd63 or ChAdOx1, MVA) vaccines, followed by challenge with chimeric sporozoites. Protective immunogenicity was determined by analyzing parasite liver load and prepatent period of blood stage infection after challenge. Of the six proteins only SPELD immunized mice showed partial protection. We discuss both the low protective immunogenicity of these proteins in the chimeric rodent malaria challenge model and the negative effect on P. berghei sporozoite infectivity of several P. falciparum proteins expressed in the chimeric sporozoites.
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Affiliation(s)
- Surendra Kumar Kolli
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Ahmed M. Salman
- Nuffield Department of Medicine, The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Jai Ramesar
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | | | - Hans Kroeze
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Fiona G. A. Geurten
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Shinya Miyazaki
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Ekta Mukhopadhyay
- Nuffield Department of Medicine, The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | | | - Adrian V. S. Hill
- Nuffield Department of Medicine, The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Chris J. Janse
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
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13
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Novel insights from the Plasmodium falciparum sporozoite-specific proteome by probabilistic integration of 26 studies. PLoS Comput Biol 2021; 17:e1008067. [PMID: 33930021 PMCID: PMC8115857 DOI: 10.1371/journal.pcbi.1008067] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 05/12/2021] [Accepted: 04/06/2021] [Indexed: 11/19/2022] Open
Abstract
Plasmodium species, the causative agent of malaria, have a complex life cycle involving two hosts. The sporozoite life stage is characterized by an extended phase in the mosquito salivary glands followed by free movement and rapid invasion of hepatocytes in the human host. This transmission stage has been the subject of many transcriptomics and proteomics studies and is also targeted by the most advanced malaria vaccine. We applied Bayesian data integration to determine which proteins are not only present in sporozoites but are also specific to that stage. Transcriptomic and proteomic Plasmodium data sets from 26 studies were weighted for how representative they are for sporozoites, based on a carefully assembled gold standard for Plasmodium falciparum (Pf) proteins known to be present or absent during the sporozoite life stage. Of 5418 Pf genes for which expression data were available at the RNA level or at the protein level, 975 were identified as enriched in sporozoites and 90 specific to them. We show that Pf sporozoites are enriched for proteins involved in type II fatty acid synthesis in the apicoplast and GPI anchor synthesis, but otherwise appear metabolically relatively inactive in the salivary glands of mosquitos. Newly annotated hypothetical sporozoite-specific and sporozoite-enriched proteins highlight sporozoite-specific functions. They include PF3D7_0104100 that we identified to be homologous to the prominin family, which in human has been related to a quiescent state of cancer cells. We document high levels of genetic variability for sporozoite proteins, specifically for sporozoite-specific proteins that elicit antibodies in the human host. Nevertheless, we can identify nine relatively well-conserved sporozoite proteins that elicit antibodies and that together can serve as markers for previous exposure. Our understanding of sporozoite biology benefits from identifying key pathways that are enriched during this life stage. This work can guide studies of molecular mechanisms underlying sporozoite biology and potential well-conserved targets for marker and drug development. When a person is bitten by an infectious malaria mosquito, sporozoites are injected into the skin with mosquito saliva. These sporozoites then travel to the liver, invade hepatocytes and multiply before the onset of the symptom-causing blood stage of malaria. By integrating published data, we contrast sporozoite protein expression with other life stages to filter out the unique features of sporozoites that help us understand this stage. We used a “guideline” that we derived from the literature on individual proteins so that we knew which proteins should be present or absent at the sporozoite stage, allowing us to weigh 26 data sets for their relevance to sporozoites. Among the newly discovered sporozoite-specific genes are candidates for fatty acid synthesis while others might play a role keeping the sporozoites in an inactive state in the mosquito salivary glands. Furthermore, we show that most sporozoite-specific proteins are genetically more variable than non-sporozoite proteins. We identify a set of conserved sporozoite proteins against which antibodies can serve as markers of recent exposure to sporozoites or that can serve as vaccine candidates. Our predictions of sporozoite-specific proteins and the assignment of previously unknown functions give new insights into the biology of this life stage.
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Plasmodium Ape1 is a multifunctional enzyme in mitochondrial base excision repair and is required for efficient transition from liver to blood stage infection. DNA Repair (Amst) 2021; 101:103098. [PMID: 33743509 DOI: 10.1016/j.dnarep.2021.103098] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 03/01/2021] [Accepted: 03/09/2021] [Indexed: 02/02/2023]
Abstract
The malaria parasite has a single mitochondrion which carries multiple tandem repeats of its 6 kb genome encoding three proteins of the electron transport chain. There is little information about DNA repair mechanisms for mitochondrial genome maintenance in Plasmodium spp. Of the two AP-endonucleases of the BER pathway encoded in the parasite nuclear genome, the EndoIV homolog PfApn1 has been identified as a mitochondrial protein with restricted functions. We explored the targeting and biochemical properties of the ExoIII homolog PfApe1. PfApe1 localized in the mitochondrion and exhibited AP-site cleavage, 3'-5' exonuclease, 3'-phosphatase, nucleotide incision repair (NIR) and RNA cleavage activities indicating a wider functional role than PfApn1. The parasite enzyme differed from human APE1 in possessing a large, disordered N-terminal extension. Molecular modelling revealed conservation of structural domains but variations in DNA-interacting residues and an insertion in the α-8 loop suggested differences with APE1. Unlike APE1, where AP-site cleavage and NIR activities could be mutually exclusive based on pH and Mg2+ ion concentration, PfApe1 was optimally active under similar conditions suggesting that it can function both as an AP-endonuclease in BER and directly cleave damaged bases in NIR under similar physiological conditions. To investigate the role of Ape1 in malaria life cycle, we disrupted the gene by double-cross-over homologous recombination. Ape1 knockout (KO) P. berghei parasites showed normal development of blood and mosquito stages. However, inoculation of mice with Ape1 KO salivary gland sporozoites revealed a reduced capacity to initiate blood stage infection. Ape1 KO parasites underwent normal liver stage development until merozoites egressed from hepatocytes. Our results indicated that the delay in pre-patent period was due to the inability of Ape1 KO merosomes to infect erythrocytes efficiently.
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15
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Srivastava PN, Narwal SK, Mishra S. Mitochondrial apurinic/apyrimidinic endonuclease Apn1 is not critical for the completion of the Plasmodium berghei life cycle. DNA Repair (Amst) 2021; 101:103078. [PMID: 33711786 DOI: 10.1016/j.dnarep.2021.103078] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/22/2021] [Accepted: 02/24/2021] [Indexed: 12/14/2022]
Abstract
Mitochondrion is an essential organelle in malaria parasite and its DNA must be maintained for optimal function during its complex life cycle. Base excision repair is one of the major pathways by which this is achieved. Apurinic/apyrimidinic (AP) endonucleases are important components of this pathway as they create a nick at the 5'-phosphodiester bond in the AP site and generate free 5'-phosphate and 3'-hydroxyl groups. Two class II AP endonucleases (Apn1 and Ape1) have been annotated in the Plasmodium berghei genome. Using reverse genetic approaches, we provide direct evidence that Apn1 is exclusively localized to the mitochondria of P. berghei. Surprisingly, our gene deletion study revealed a completely dispensable role of Apn1 for the entirety of the P. berghei life cycle. Apn1- parasites were found to successfully grow in the blood. They were transmitted normally to the mosquito midguts and salivary glands. Sporozoites obtained from the salivary glands were infective and achieved similar patency as WT. Our results help emphasize the non-availability of this enzyme as a plausible drug target. We also emphasize the importance of genetic validation of antimalarial drug targets before furthering them down the drug discovery pipeline.
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Affiliation(s)
- Pratik Narain Srivastava
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Sunil Kumar Narwal
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Satish Mishra
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, 226031, India; Academy of Scientific and Innovative Research, Ghaziabad, India.
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16
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Marwah M, Narain Srivastava P, Mishra S, Nagarsenker M. Functionally engineered 'hepato-liposomes': Combating liver-stage malaria in a single prophylactic dose. Int J Pharm 2020; 587:119710. [PMID: 32739383 DOI: 10.1016/j.ijpharm.2020.119710] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 07/25/2020] [Accepted: 07/27/2020] [Indexed: 01/09/2023]
Abstract
Primaquine continues to remain the gold standard molecule with an incumbent toxicity profile, as far as radical treatment of malaria is concerned. Better molecules are available at experimental level but their targeted delivery is a challenge. The present work identifies 'Decoquinate (DQN)' as a repurposed, safer drug molecule with a potential to function as an appealing replacement for primaquine active against liver-stage malaria. The work focuses on delivering the highly lipophilic DQN (log P ~ 5) in a liposomal carrier system to 'sporozoite infested hepatocytes' using two different in-house synthesized hepatotropic ligands. Functionally engineered 'hepato-liposomes' exhibit differences in their DQN loading capacities but no significant change in morphology or particle size and are also not affected by freeze drying. Two ligands, targeting different receptors on hepatocytes, have been compared for their in vitro and in vivo drug delivery efficiency in liver stage malaria. The studies reveal superior antimalarial efficacy of differently designed DQN loaded liposomes and demonstrate antimalarial efficacy at a low dose of 0.5 mg/kg for a repurposed molecule like DQN. The in vivo studies successfully discriminate the functional efficiency of the carriers and establish the importance of design in liposomal drug delivery for malarial prophylaxis.
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Affiliation(s)
- Megha Marwah
- Department of Pharmaceutics, Bombay College of Pharmacy, Kalina, Santacruz (East), Mumbai, India
| | - Pratik Narain Srivastava
- Division Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Satish Mishra
- Division Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India.
| | - Mangal Nagarsenker
- Department of Pharmaceutics, Bombay College of Pharmacy, Kalina, Santacruz (East), Mumbai, India.
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17
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Gupta R, Mishra A, Choudhary HH, Narwal SK, Nayak B, Srivastava PN, Mishra S. Secreted protein with altered thrombospondin repeat (SPATR) is essential for asexual blood stages but not required for hepatocyte invasion by the malaria parasite Plasmodium berghei. Mol Microbiol 2019; 113:478-491. [PMID: 31755154 DOI: 10.1111/mmi.14432] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 11/30/2022]
Abstract
Upon entering its mammalian host, the malaria parasite productively invades two distinct cell types, that is, hepatocytes and erythrocytes during which several adhesins/invasins are thought to be involved. Many surface-located proteins containing thrombospondin Type I repeat (TSR) which help establish host-parasite molecular crosstalk have been shown to be essential for mammalian infection. Previous reports indicated that antibodies produced against Plasmodium falciparum secreted protein with altered thrombospondin repeat (SPATR) block hepatocyte invasion by sporozoites but no genetic evidence of its contribution to invasion has been reported. After failing to generate Spatr knockout in Plasmodium berghei blood stages, a conditional mutagenesis system was employed. Here, we show that SPATR plays an essential role during parasite's blood stages. Mutant salivary gland sporozoites exhibit normal motility, hepatocyte invasion, liver stage development and rupture of the parasitophorous vacuole membrane resulting in merosome formation. But these mutant hepatic merozoites failed to establish a blood stage infection in vivo. We provide direct evidence that SPATR is not required for hepatocyte invasion but plays an essential role during the blood stages of P. berghei.
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Affiliation(s)
- Roshni Gupta
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Akancha Mishra
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India.,Academy of Scientific and Innovative Research, Ghaziabad, India
| | - Hadi Hasan Choudhary
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Sunil Kumar Narwal
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Bandita Nayak
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India.,Academy of Scientific and Innovative Research, Ghaziabad, India
| | - Pratik Narain Srivastava
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Satish Mishra
- Division of Molecular Parasitology and Immunology, CSIR-Central Drug Research Institute, Lucknow, India.,Academy of Scientific and Innovative Research, Ghaziabad, India
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18
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Transcriptomics and proteomics reveal two waves of translational repression during the maturation of malaria parasite sporozoites. Nat Commun 2019; 10:4964. [PMID: 31673027 PMCID: PMC6823429 DOI: 10.1038/s41467-019-12936-6] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 10/09/2019] [Indexed: 02/08/2023] Open
Abstract
Plasmodium sporozoites are transmitted from infected mosquitoes to mammals, and must navigate the host skin and vasculature to infect the liver. This journey requires distinct proteomes. Here, we report the dynamic transcriptomes and proteomes of both oocyst sporozoites and salivary gland sporozoites in both rodent-infectious Plasmodium yoelii parasites and human-infectious Plasmodium falciparum parasites. The data robustly define mRNAs and proteins that are upregulated in oocyst sporozoites (UOS) or upregulated in infectious sporozoites (UIS) within the salivary glands, including many that are essential for sporozoite functions in the vector and host. Moreover, we find that malaria parasites use two overlapping, extensive, and independent programs of translational repression across sporozoite maturation to temporally regulate protein expression. Together with gene-specific validation experiments, these data indicate that two waves of translational repression are implemented and relieved at different times during sporozoite maturation, migration and infection, thus promoting their successful development and vector-to-host transition. Here, the authors report transcriptomes and proteomes of oocyst sporozoite and salivary gland sporozoite stages in rodent-infectious Plasmodium yoelii parasites and human infectious Plasmodium falciparum parasites and define two waves of translational repression during sporozoite maturation.
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Jillapalli R, Narwal SK, Kolli SK, Mastan BS, Segireddy RR, Dey S, Srivastava PN, Mishra S, Kumar KA. A Plasmodium berghei putative serine-threonine kinase 2 ( PBANKA_0311400) is required for late liver stage development and timely initiation of blood stage infection. Biol Open 2019; 8:bio.042028. [PMID: 31444161 PMCID: PMC6737972 DOI: 10.1242/bio.042028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In Plasmodium, protein kinases govern key biological processes of the parasite life cycle involved in the establishment of infection, dissemination and sexual reproduction. The rodent malaria model Plasmodium berghei encodes for 66 putative eukaryotic protein kinases (ePKs) as identified through modelling domain signatures and are highly conserved in Plasmodium falciparum. We report here the functional characterisation of a putative serine-threonine kinase PBANKA_0311400 identified in this kinome analysis and designate it as Pbstk2. To elucidate its role, we knocked out Pbstk2 locus and performed a detailed phenotypic analysis at different life cycle stages. The Pbstk2 knockout (KO) was not compromised in asexual blood stage propagation, transmission and development in the mosquito vector. The Pbstk2 KO produced viable salivary gland sporozoites that successfully transformed into exo-erythrocytic forms (EEFs) and were morphologically indistinguishable from wild-type GFP (WT GFP) with regard to size and shape until 48 h. An intravenous dose of 1×103Pbstk2 KO sporozoites in C57BL/6 mice failed to establish blood stage infection and a higher dose of 5X103 showed a 2–3 day delay in prepatency as compared to WT GFP parasites. Consistent with such an observation, analysis of in vitro EEF development at 62 h revealed that the hepatic merozoite numbers were reduced to nearly 40% as compared to WT GFP and showed meagre expression of MSP1. Our studies provide evidence for the role of PbSTK2 in late liver stage development and for the successful establishment of a timely blood stage infection. Summary: Requirement of a putative serine threonine kinase 2 (PBANKA_0311400) for Plasmodium berghei liver stage development.
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Affiliation(s)
- Ravi Jillapalli
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | - Sunil Kumar Narwal
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Surendra Kumar Kolli
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | - Babu S Mastan
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | - Rameswara Reddy Segireddy
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | - Sandeep Dey
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | | | - Satish Mishra
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Kota Arun Kumar
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
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20
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Togiri J, Segireddy RR, Mastan BS, Singh D, Kolli SK, Ghosh A, Al-Nihmi FMA, Maruthi M, Choudhary HH, Dey S, Mishra S, Kumar KA. Plasmodium berghei sporozoite specific genes- PbS10 and PbS23/SSP3 are required for the development of exo-erythrocytic forms. Mol Biochem Parasitol 2019; 232:111198. [PMID: 31251952 DOI: 10.1016/j.molbiopara.2019.111198] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 06/17/2019] [Accepted: 06/23/2019] [Indexed: 10/26/2022]
Abstract
Plasmodium sporozoites are infective forms of the parasite to mammalian hepatocytes. Sporozoite surface or secreted proteins likely play an important role in recognition, invasion and successful establishment of hepatocyte infection. By approaches of reverse genetics, we report the functional analysis of two Plasmodium berghei (Pb) sporozoite specific genes- PbS10 and PbS23/SSP3 that encode for proteins with a putative signal peptide. The expression of both genes was high in oocyst and salivary gland sporozoite stages as compared to other life cycle stages and PbS23/SSP3 protein was detected in salivary gland sporozoites. Both mutants were indistinguishable to wild-type parasites with regard to asexual growth in RBC, ability to complete sexual reproduction and form sporozoites in vector host. While the sporozoite stage of both mutants were able to glide and invade hepatocytes normally in vitro and in vivo, PbS10 mutants suffered growth attenuation at an early stage while PbS23/SSP3 mutants manifested defect during late exo-erythrocytic form maturation. Interestingly, both mutants gave rare breakthrough infections, suggesting that while both were critical for liver stage development, their depletion did not completely abrogate blood stage infection. These findings have important implications for weakening sporozoites by multiple gene attenuation towards the generation of a safe whole organism vaccine.
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Affiliation(s)
- Jyothi Togiri
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Rameswara Reddy Segireddy
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Babu S Mastan
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Dipti Singh
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Surendra Kumar Kolli
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Ankit Ghosh
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | | | - Mulaka Maruthi
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Hadi Hasan Choudhary
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Sandeep Dey
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Satish Mishra
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Kota Arun Kumar
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India.
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21
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Choudhary HH, Gupta R, Mishra S. PKAc is not required for the preerythrocytic stages of Plasmodium berghei. Life Sci Alliance 2019; 2:2/3/e201900352. [PMID: 31142638 PMCID: PMC6545604 DOI: 10.26508/lsa.201900352] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 05/22/2019] [Accepted: 05/22/2019] [Indexed: 12/12/2022] Open
Abstract
The mutant salivary gland sporozoites lacking PKAc are able to glide, invade hepatocytes, and mature into hepatic merozoites, which release successfully from the merosome, however, fail to initiate blood stage infection when inoculated into mice. Plasmodium sporozoites invade hepatocytes to initiate infection in the mammalian host. In the infected hepatocytes, sporozoites undergo rapid expansion and differentiation, resulting in the formation and release of thousands of invasive merozoites into the bloodstream. Both sporozoites and merozoites invade their host cells by activation of a signaling cascade followed by discharge of micronemal content. cAMP-dependent protein kinase catalytic subunit (PKAc)–mediated signaling plays an important role in merozoite invasion of erythrocytes, but its role during other stages of the parasite remains unknown. Becaused of the essentiality of PKAc in blood stages, we generated conditional mutants of PKAc by disrupting the gene in Plasmodium berghei sporozoites. The mutant salivary gland sporozoites were able to glide, invaded hepatocytes, and matured into hepatic merozoites which were released successfully from merosome, however failed to initiate blood stage infection when inoculated into mice. Our results demonstrate that malaria parasite complete preerythrocytic stages development without PKAc, raising the possibility that the PKAc independent signaling operates in preerythrocytic stages of P. berghei.
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Affiliation(s)
| | - Roshni Gupta
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Satish Mishra
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow, India .,Academy of Scientific and Innovative Research, Ghaziabad, India
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Kumar V, Behl A, Kapoor P, Nayak B, Singh G, Singh AP, Mishra S, Kang TS, Mishra PC, Hora R. Inner membrane complex 1l protein of Plasmodium falciparum links membrane lipids with cytoskeletal element 'actin' and its associated motor 'myosin'. Int J Biol Macromol 2018; 126:673-684. [PMID: 30599160 DOI: 10.1016/j.ijbiomac.2018.12.239] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 12/25/2018] [Accepted: 12/26/2018] [Indexed: 01/14/2023]
Abstract
The inner membrane complex (IMC) is a defining feature of apicomplexans comprising of lipid and protein components involved in gliding motility and host cell invasion. Motility of Plasmodium parasites is accomplished by an actin and myosin based glideosome machinery situated between the parasite plasma membrane (PPM) and IMC. Here, we have studied in vivo expression and localization of a Plasmodium falciparum (Pf) IMC protein 'PfIMC1l' and characterized it functionally by using biochemical assays. We have identified cytoskeletal protein 'actin' and motor protein 'myosin' as novel binding partners of PfIMC1l, alongside its interaction with the lipids 'cholesterol' and 'phosphatidyl-inositol 4, 5 bisphosphate' (PIP2). While actin and myosin compete for interaction with PfIMC1l, actin and either of the lipids (cholesterol or PIP2) simultaneously bind PfIMC1l. Interestingly, PfIMC1l showed enhanced binding with actin in the presence of calcium ions, and displayed direct binding with calcium. Based on our in silico analysis and experimental data showing PfIMC1l-actin/myosin and PfIMC1l-lipid interactions, we propose that this protein may anchor the IMC membrane with the parasite gliding apparatus. Considering its binding with key proteins involved in motility viz. myosin and actin (with calcium dependence), we suggest that PfIMC1l may have a role in the locomotion of Plasmodium.
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Affiliation(s)
- Vikash Kumar
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Ankita Behl
- Department of Biotechnology, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Payal Kapoor
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Bandita Nayak
- CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, India
| | - Gurbir Singh
- Department of Chemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Amrit Pal Singh
- Department of Pharmaceutical Science, Guru Nanak Dev University, Amritsar, Punjab, India
| | - Satish Mishra
- CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, India
| | - Tejwant Singh Kang
- Department of Chemistry, Guru Nanak Dev University, Amritsar, Punjab, India
| | | | - Rachna Hora
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, Punjab, India.
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23
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Roth A, Adapa SR, Zhang M, Liao X, Saxena V, Goffe R, Li S, Ubalee R, Saggu GS, Pala ZR, Garg S, Davidson S, Jiang RHY, Adams JH. Unraveling the Plasmodium vivax sporozoite transcriptional journey from mosquito vector to human host. Sci Rep 2018; 8:12183. [PMID: 30111801 PMCID: PMC6093925 DOI: 10.1038/s41598-018-30713-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 08/03/2018] [Indexed: 02/07/2023] Open
Abstract
Malaria parasites transmitted by mosquito bite are remarkably efficient in establishing human infections. The infection process requires roughly 30 minutes and is highly complex as quiescent sporozoites injected with mosquito saliva must be rapidly activated in the skin, migrate through the body, and infect the liver. This process is poorly understood for Plasmodium vivax due to low infectivity in the in vitro models. To study this skin-to-liver-stage of malaria, we used quantitative bioassays coupled with transcriptomics to evaluate parasite changes linked with mammalian microenvironmental factors. Our in vitro phenotyping and RNA-seq analyses revealed key microenvironmental relationships with distinct biological functions. Most notable, preservation of sporozoite quiescence by exposure to insect-like factors coupled with strategic activation limits untimely activation of invasion-associated genes to dramatically increase hepatocyte invasion rates. We also report the first transcriptomic analysis of the P. vivax sporozoite interaction in salivary glands identifying 118 infection-related differentially-regulated Anopheles dirus genes. These results provide important new insights in malaria parasite biology and identify priority targets for antimalarial therapeutic interventions to block P. vivax infection.
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Affiliation(s)
- Alison Roth
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Swamy R Adapa
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Min Zhang
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Xiangyun Liao
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Vishal Saxena
- Molecular Parasitology and System Biology Lab, Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Rajasthan, India
| | - Raaven Goffe
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Suzanne Li
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Ratawan Ubalee
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Gagandeep S Saggu
- Laboratory of Malaria and Vector Research, National Institute of Allergic and Infectious Diseases, National Institute of Health, Rockville, Maryland, USA
| | - Zarna R Pala
- Molecular Parasitology and System Biology Lab, Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Rajasthan, India
| | - Shilpi Garg
- Molecular Parasitology and System Biology Lab, Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Rajasthan, India
| | - Silas Davidson
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Rays H Y Jiang
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA.
| | - John H Adams
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA.
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24
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Nyboer B, Heiss K, Mueller AK, Ingmundson A. The Plasmodium liver-stage parasitophorous vacuole: A front-line of communication between parasite and host. Int J Med Microbiol 2017; 308:107-117. [PMID: 28964681 DOI: 10.1016/j.ijmm.2017.09.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 08/19/2017] [Accepted: 09/11/2017] [Indexed: 12/13/2022] Open
Abstract
The intracellular development and differentiation of the Plasmodium parasite in the host liver is a prerequisite for the actual onset of malaria disease pathology. Since liver-stage infection is clinically silent and can be completely eliminated by sterilizing immune responses, it is a promising target for urgently needed innovative antimalarial drugs and/or vaccines. Discovered more than 65 years ago, these stages remain poorly understood regarding their molecular repertoire and interaction with their host cells in comparison to the pathogenic erythrocytic stages. The differentiating and replicative intrahepatic parasite resides in a membranous compartment called the parasitophorous vacuole, separating it from the host-cell cytoplasm. Here we outline seminal work that contributed to our present understanding of the fundamental dynamic cellular processes of the intrahepatic malarial parasite with both specific host-cell factors and compartments.
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Affiliation(s)
- Britta Nyboer
- Centre for Infectious Diseases, Parasitology, University Hospital Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Kirsten Heiss
- Centre for Infectious Diseases, Parasitology, University Hospital Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany; Centre for Infection Research (DZIF), D 69120 Heidelberg, Germany
| | - Ann-Kristin Mueller
- Centre for Infectious Diseases, Parasitology, University Hospital Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany; Centre for Infection Research (DZIF), D 69120 Heidelberg, Germany,.
| | - Alyssa Ingmundson
- Department of Molecular Parasitology, Institute of Biology, Humboldt University Berlin, Philippstrasse 13, 10115 Berlin, Germany.
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25
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Proteogenomic analysis of the total and surface-exposed proteomes of Plasmodium vivax salivary gland sporozoites. PLoS Negl Trop Dis 2017; 11:e0005791. [PMID: 28759593 PMCID: PMC5552340 DOI: 10.1371/journal.pntd.0005791] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 08/10/2017] [Accepted: 07/10/2017] [Indexed: 12/29/2022] Open
Abstract
Plasmodium falciparum and Plasmodium vivax cause the majority of human malaria cases. Research efforts predominantly focus on P. falciparum because of the clinical severity of infection and associated mortality rates. However, P. vivax malaria affects more people in a wider global range. Furthermore, unlike P. falciparum, P. vivax can persist in the liver as dormant hypnozoites that can be activated weeks to years after primary infection, causing relapse of symptomatic blood stages. This feature makes P. vivax unique and difficult to eliminate with the standard tools of vector control and treatment of symptomatic blood stage infection with antimalarial drugs. Infection by Plasmodium is initiated by the mosquito-transmitted sporozoite stage, a highly motile invasive cell that targets hepatocytes in the liver. The most advanced malaria vaccine for P. falciparum (RTS,S, a subunit vaccine containing of a portion of the major sporozoite surface protein) conferred limited protection in Phase III trials, falling short of WHO-established vaccine efficacy goals. However, blocking the sporozoite stage of infection in P. vivax, before the establishment of the chronic liver infection, might be an effective malaria vaccine strategy to reduce the occurrence of relapsing blood stages. It is also thought that a multivalent vaccine comprising multiple sporozoite surface antigens will provide better protection, but a comprehensive analysis of proteins in P. vivax sporozoites is not available. To inform sporozoite-based vaccine development, we employed mass spectrometry-based proteomics to identify nearly 2,000 proteins present in P. vivax salivary gland sporozoites. Analysis of protein post-translational modifications revealed extensive phosphorylation of glideosome proteins as well as regulators of transcription and translation. Additionally, the sporozoite surface proteins CSP and TRAP, which were recently discovered to be glycosylated in P. falciparum salivary gland sporozoites, were also observed to be similarly modified in P. vivax sporozoites. Quantitative comparison of the P. vivax and P. falciparum salivary gland sporozoite proteomes revealed a high degree of similarity in protein expression levels, including among invasion-related proteins. Nevertheless, orthologs with significantly different expression levels between the two species could be identified, as well as highly abundant, species-specific proteins with no known orthologs. Finally, we employed chemical labeling of live sporozoites to isolate and identify 36 proteins that are putatively surface-exposed on P. vivax salivary gland sporozoites. In addition to identifying conserved sporozoite surface proteins identified by similar analyses of other Plasmodium species, our analysis identified several as-yet uncharacterized proteins, including a putative 6-Cys protein with no known ortholog in P. falciparum. Malaria is one of the most important infectious diseases in the world with hundreds of millions of new cases every year. Malaria is caused by parasites of the genus Plasmodium which have a complex life cycle, alternating between mosquito and mammalian hosts. Human infections are initiated with a sporozoite inoculum deposited into the skin by parasite-infected mosquitoes as they probe for blood. Sporozoites must locate blood vessels and enter the circulation to reach the liver where they invade and grow in hepatocytes. In the case of Plasmodium vivax, one of the two Plasmodium species responsible for the majority of the disease burden in the world, the parasite has the ability to persist for months in the liver after the initial infection and its activation causes the recurring appearance of the parasite in the blood. Though all clinical symptoms are attributable to the blood stages, it is only by attacking the transmission stages before the formation of hypnozoites (the persisting parasites in the liver) that an impact on the burden of vivax malaria can be achieved. We used state-of-the-art mass spectrometry-based proteomics tools to identify the total protein make-up of P. vivax sporozoites. By analyzing which proteins are exposed to the parasite surface and determining the degree of protein’s post-translational modifications, our investigation will aid the understanding of the novel biology of sporozoites and importantly, advise the development of potential vaccine candidates targeting this parasite stage.
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26
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Kreutzfeld O, Müller K, Matuschewski K. Engineering of Genetically Arrested Parasites (GAPs) For a Precision Malaria Vaccine. Front Cell Infect Microbiol 2017; 7:198. [PMID: 28620583 PMCID: PMC5450620 DOI: 10.3389/fcimb.2017.00198] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 05/04/2017] [Indexed: 01/08/2023] Open
Abstract
Continuous stage conversion and swift changes in the antigenic repertoire in response to acquired immunity are hallmarks of complex eukaryotic pathogens, including Plasmodium species, the causative agents of malaria. Efficient elimination of Plasmodium liver stages prior to blood infection is one of the most promising malaria vaccine strategies. Here, we describe different genetically arrested parasites (GAPs) that have been engineered in Plasmodium berghei, P. yoelii and P. falciparum and compare their vaccine potential. A better understanding of the immunological mechanisms of prime and boost by arrested sporozoites and experimental strategies to enhance vaccine efficacy by further engineering existing GAPs into a more immunogenic form hold promise for continuous improvements of GAP-based vaccines. A critical hurdle for vaccines that elicit long-lasting protection against malaria, such as GAPs, is safety and efficacy in vulnerable populations. Vaccine research should focus on solutions toward turning malaria into a vaccine-preventable disease, which would offer an exciting new path of malaria control.
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Affiliation(s)
- Oriana Kreutzfeld
- Department of Molecular Parasitology, Institute of Biology, Humboldt UniversityBerlin, Germany
| | - Katja Müller
- Department of Molecular Parasitology, Institute of Biology, Humboldt UniversityBerlin, Germany
| | - Kai Matuschewski
- Department of Molecular Parasitology, Institute of Biology, Humboldt UniversityBerlin, Germany
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