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Huynh MH, Carruthers VB. Toxoplasma gondii excretion of glycolytic products is associated with acidification of the parasitophorous vacuole during parasite egress. PLoS Pathog 2022; 18:e1010139. [PMID: 35512005 PMCID: PMC9113570 DOI: 10.1371/journal.ppat.1010139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 05/17/2022] [Accepted: 03/28/2022] [Indexed: 11/19/2022] Open
Abstract
The Toxoplasma gondii lytic cycle is a repetition of host cell invasion, replication, egress, and re-invasion into the next host cell. While the molecular players involved in egress have been studied in greater detail in recent years, the signals and pathways for triggering egress from the host cell have not been fully elucidated. A perforin-like protein, PLP1, has been shown to be necessary for permeabilizing the parasitophorous vacuole (PV) membrane or exit from the host cell. In vitro studies indicated that PLP1 is most active in acidic conditions, and indirect evidence using superecliptic pHluorin indicated that the PV pH drops prior to parasite egress. Using ratiometric pHluorin, a GFP variant that responds to changes in pH with changes in its bimodal excitation spectrum peaks, allowed us to directly measure the pH in the PV prior to and during egress by live-imaging microscopy. A statistically significant change was observed in PV pH during ionomycin or zaprinast induced egress in both wild-type RH and Δplp1 vacuoles compared to DMSO-treated vacuoles. Interestingly, if parasites are chemically paralyzed, a pH drop is still observed in RH but not in Δplp1 tachyzoites. This indicates that the pH drop is dependent on the presence of PLP1 or motility. Efforts to determine transporters, exchangers, or pumps that could contribute to the drop in PV pH identified two formate-nitrite transporters (FNTs). Auxin induced conditional knockdown and knockouts of FNT1 and FNT2 reduced the levels of lactate and pyruvate released by the parasites and lead to an abatement of vacuolar acidification. While additional transporters and molecules are undoubtedly involved, we provide evidence of a definitive reduction in vacuolar pH associated with induced and natural egress and characterize two transporters that contribute to the acidification. Toxoplasma gondii is a single celled intracellular parasite that infects many different animals, and it is thought to infect up to one third of the human population. This parasite must rupture out of its replicative compartment and the host cell to spread from one cell to another. Previous studies indicated that a decrease in pH occurs within the replicative compartment near the time of parasite exit from host cells, an event termed egress. However, it remained unknown whether the decrease in pH is directly tied to egress and, if so, what is responsible for the decrease in pH. Here we used a fluorescent reporter protein to directly measure pH within the replicative compartment during parasite egress. We found that pH decreases immediately prior to parasite egress and that this decrease is linked to parasite disruption of membranes. We also identified a family of transporters that release acidic products from parasite use of glucose for energy as contributing to the decrease in pH during egress. Our findings provide new insight that connects parasite glucose metabolism to acidification of its replicative compartment during egress from infected cells.
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Affiliation(s)
- My-Hang Huynh
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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3D holotomographic monitoring of Ca ++ dynamics during ionophore-induced Neospora caninum tachyzoite egress from primary bovine host endothelial cells. Parasitol Res 2021; 121:1169-1177. [PMID: 34386856 PMCID: PMC8986705 DOI: 10.1007/s00436-021-07260-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 07/18/2021] [Indexed: 12/04/2022]
Abstract
Neospora caninum represents an obligate intracellular parasite that belongs to the phylum Apicomplexa and is a major abortive agent in bovines. During merogony, N. caninum tachyzoites invade and proliferate in host cells in vivo, including endothelial cells of lymphatic and blood vessels. The egress at the end of the lytic cycle is tightly regulated in apicomplexans. Evidence in Toxoplasma gondii shows that Ca++ signalling governs tachyzoite egress. Much less is known on egress mechanisms of N. caninum. Here, we show, using 3D live cell holotomographic microscopy in fluo-4 AM-loaded N. caninum-infected BUVEC, that treatments with the calcium ionophore A23187 at 24- and 42-h post-infection (h p. i.) induced a fast and sustained increase in Ca++ signals in parallel to tachyzoite egress. A23187 treatments exclusively triggered tachyzoite release at 42-h p. i. but failed to do so at 24-h p. i. indicating a role for meront maturation in calcium-induced tachyzoite egress. Overall, we show that live cell 3D holotomographic analysis in combination with epifluorescence is a suitable tool to study calcium dynamics related to coccidian egress or other important cell functions.
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Structural, Functional, and Metabolic Alterations in Human Cerebrovascular Endothelial Cells during Toxoplasma gondii Infection and Amelioration by Verapamil In Vitro. Microorganisms 2020; 8:microorganisms8091386. [PMID: 32927732 PMCID: PMC7564162 DOI: 10.3390/microorganisms8091386] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/01/2020] [Accepted: 09/08/2020] [Indexed: 12/12/2022] Open
Abstract
Toxoplasma gondii (T. gondii), the causative agent of toxoplasmosis, is a frequent cause of brain infection. Despite its known ability to invade the brain, there is still a dire need to better understand the mechanisms by which this parasite interacts with and crosses the blood–brain barrier (BBB). The present study revealed structural and functional changes associated with infection and replication of T. gondii within human brain microvascular endothelial cells (BMECs) in vitro. T. gondii proliferated within the BMECs and disrupted the integrity of the cerebrovascular barrier through diminishing the cellular viability, disruption of the intercellular junctions and increasing permeability of the BMEC monolayer, as well as altering lipid homeostasis. Proton nuclear magnetic resonance (1H NMR)-based metabolomics combined with multivariate data analysis revealed profiles that can be attributed to infection and variations in the amounts of certain metabolites (e.g., amino acids, fatty acids) in the extracts of infected compared to control cells. Notably, treatment with the Ca2+ channel blocker verapamil rescued BMEC barrier integrity and restricted intracellular replication of the tachyzoites regardless of the time of treatment application (i.e., prior to infection, early- and late-infection). This study provides new insights into the structural and functional changes that accompany T. gondii infection of the BMECs, and sheds light upon the ability of verapamil to inhibit the parasite proliferation and to ameliorate the adverse effects caused by T. gondii infection.
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Firdaus ER, Park JH, Lee SK, Park Y, Cha GH, Han ET. 3D morphological and biophysical changes in a single tachyzoite and its infected cells using three-dimensional quantitative phase imaging. JOURNAL OF BIOPHOTONICS 2020; 13:e202000055. [PMID: 32441392 DOI: 10.1002/jbio.202000055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 05/18/2020] [Accepted: 05/19/2020] [Indexed: 06/11/2023]
Abstract
Toxoplasma gondii is an apicomplexan parasite that causes toxoplasmosis in the human body and commonly infects warm-blooded organisms. Pathophysiology of its diseases is still an interesting issue to be studied since T gondii can infect nearly all nucleated cells. Imaging techniques are crucial for studying its pathophysiology. In T gondii-infected cells structural and biochemical alterations occurred. To study that modification, we use digital holotomography to investigate the structure and biochemical alteration of single tachyzoite and its infected cells in a label-free and quantitative manner. Quantification analysis was done by measuring the refractive index distribution, which provides information about the concentration and dry mass of individual cells. This study showed that holotomography could be effectively used to identify the structural and biochemical alteration in tremendously different cells in supporting pathophysiological research in particular for T gondii-caused diseases.
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Affiliation(s)
- Egy Rahman Firdaus
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
| | - Ji-Hoon Park
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
| | - Seong-Kyun Lee
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
| | - YongKeun Park
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea
| | - Guang-Ho Cha
- Department of Medical Science & Infection Biology, Chungnam National University, School of Medicine, Daejeon, Korea
| | - Eun-Taek Han
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
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López-Osorio S, Chaparro-Gutiérrez JJ, Gómez-Osorio LM. Overview of Poultry Eimeria Life Cycle and Host-Parasite Interactions. Front Vet Sci 2020; 7:384. [PMID: 32714951 PMCID: PMC7351014 DOI: 10.3389/fvets.2020.00384] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 05/29/2020] [Indexed: 11/13/2022] Open
Abstract
Apicomplexan parasites of the genus Eimeria are organisms which invade the intestinal tract, causing coccidiosis, an enteric disease of major economic importance worldwide. The disease causes high morbidity ranging from an acute, bloody enteritis with high mortality, to subclinical disease. However, the presence of intestinal lesions depends on the Eimeria species. The most important poultry Eimeria species are: E. tenella, E. necatrix, E. acervulina, E. maxima, E. brunetti, E. mitis, and E. praecox. Key points to better understanding the behavior of this species are the host-parasite interactions and its life cycle. The present paper reviews the literature available regarding the life cycle and the initial host-parasite interaction. More studies are needed to better understand these interactions in poultry Eimerias, taking into account that almost all the information available was generated from other apicomplexan parasites that generate human disease.
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Affiliation(s)
- Sara López-Osorio
- CIBAV Research Group, Facultad de Ciencias Agrarias, Universidad de Antioquia, Medellín, Colombia
| | | | - Luis M. Gómez-Osorio
- CIBAV Research Group, Facultad de Ciencias Agrarias, Universidad de Antioquia, Medellín, Colombia
- Alura Animal Health and Nutrition, Medellin, Colombia
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Agordzo SK, Badu K, Addo MG, Owusu CK, Mutala AH, Tweneboah A, Abbas DA, Ayisi-Boateng NK. Seroprevalence, risk factors and impact of Toxoplasma gondii infection on haematological parameters in the Ashanti region of Ghana: a cross-sectional study. AAS Open Res 2020; 2:166. [PMID: 32734139 PMCID: PMC7369427 DOI: 10.12688/aasopenres.13022.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2020] [Indexed: 11/24/2022] Open
Abstract
Background: Toxoplasma gondii is an obligate, intracellular, apicomplexan parasite that causes toxoplasmosis. Although the global prevalence of toxoplasmosis has been estimated to be approximately 30%, there is limited seroprevalence data in Ghana, with a dearth of information on the impact of T. gondii on haematological parameters in exposed persons. Methods: Questionnaires were administered to 300 consenting individuals to obtain demographic information and assessment of their risk of exposure to T. gondii. Using anti- T. gondii IgG/IgM combo test kits, seropositivity to parasite-specific IgG and/or IgM was determined. A haematological analyser was used to measure haematological parameters. Results: There was an overall seroprevalence of 50.3% (n=151), with 49.7% (n=149) of the study participants seropositive for IgG and 1% (n=3) testing positive for IgM. Furthermore, the observed seroprevalence among pregnant women was 56.4% (n=62). With regard to settlement type, a seroprevalence of 55.6% was observed in the rural community, 50.6% in the peri-urban community and 47.1% in the urban community. The study identified cat ownership, contact with cat litter, contact with raw meat [RR (95% CI: 1.76 (1.23-2.53), 1.66 (1.03-2.67), 1.25(1.00-1.57)] and age (p<0.001) as risk factors for infection. Analyses of haematological data revealed significant reduction in the white blood cell, lymphocytes and mean corpuscular volume levels in seropositive males (p=0.0223, 0.0275, and 0.0271) respectively. Only the mean corpuscular volume of seropositive females reduced significantly as compared to the seronegative counterparts (p=0.0035). Conclusions: About half of the study population, including women of reproductive age carried antibodies against T. gondii, raising concerns about the risk of congenital toxoplasmosis and anaemia. We, therefore, recommend that screening for Toxoplasma gondii be included in the routine screening of pregnant women seeking antenatal care and further investigation should be conducted on the haematological implications of infection in humans.
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Affiliation(s)
- Samuel Kekeli Agordzo
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Kingsley Badu
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
- Kumasi Centre for Collaborative Research for Tropical Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Mathew Glover Addo
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Christian Kwasi Owusu
- Kumasi Centre for Collaborative Research for Tropical Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Abdul-Hakim Mutala
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Austine Tweneboah
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Dawood Ackom Abbas
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Nana Kwame Ayisi-Boateng
- School of Medicine and Dentistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
- The University Hospital, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
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7
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Njiri OA, Zhang X, Zhang Y, Wu B, Jiang L, Li Q, Liu W, Chen T. CD209 C-Type Lectins Promote Host Invasion, Dissemination, and Infection of Toxoplasma gondii. Front Immunol 2020; 11:656. [PMID: 32391004 PMCID: PMC7190871 DOI: 10.3389/fimmu.2020.00656] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 03/23/2020] [Indexed: 01/24/2023] Open
Abstract
Toxoplasma gondii, the causative agent of toxoplasmosis and a major opportunistic parasite associated with AIDS, is able to invade host cells of animals and humans. Studies suggested that the ability of host invasion by the tachyzoite, the infectious form of T. gondii, is essential for the pathogenicity to promote its dissemination to other parts of animal hosts. However, the detailed molecular mechanisms for host invasion and dissemination of the parasites are not clear. On the other hand, viruses and bacteria are able to interact with and hijack DC-SIGN (CD209) C-type lectin on antigen presenting cells (APCs), such as dendritic cells and macrophages as the Trojan horses to promote host dissemination. In this study, we showed that invasion of T. gondii into host cells was enhanced by this parasite-CD209 interaction that were inhibited by ligand mimicking-oligosaccharides and the anti-CD209 antibody. Furthermore, covering the exposures of DC-SIGN by these oligosaccharides reduced parasite burden, host spreading and mortality associated with T. gondii infection. These results suggested that interaction of T. gondii to APCs expressing DC-SIGN might promote host dissemination and infection. Can the blockage of this interaction with Mannan and/or anti-CD209 antibody be developed as a prevention or treatment method for T. gondii infection?
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Affiliation(s)
- Olivia Adhiambo Njiri
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China.,Department of Biological Sciences, Faculty of Science, Engineering and Technology, Chuka University, Chuka, Kenya
| | - Xiaoyan Zhang
- Division of Parasitology, Department of Pathogen Biology, School of Basic Sciences, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yingmiao Zhang
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China
| | - Bicong Wu
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China
| | - Lingyu Jiang
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China
| | - Qiao Li
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China
| | - Wenqi Liu
- Division of Parasitology, Department of Pathogen Biology, School of Basic Sciences, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Tie Chen
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China
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8
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Agordzo SK, Badu K, Addo MG, Owusu CK, Mutala AH, Tweneboah A, Abbas DA, Ayisi-Boateng NK. Seroprevalence, risk factors and impact of Toxoplasma gondii infection on haematological parameters in the Ashanti region of Ghana: a cross-sectional study. AAS Open Res 2019; 2:166. [PMID: 32734139 PMCID: PMC7369427 DOI: 10.12688/aasopenres.13022.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/2019] [Indexed: 03/30/2024] Open
Abstract
Background: Toxoplasma gondii is an obligate, intracellular, apicomplexan parasite that causes toxoplasmosis. Although the global prevalence of toxoplasmosis has been estimated to be approximately 30%, there is limited seroprevalence data in Ghana, with a dearth of information on the impact of T. gondii on haematological parameters in exposed persons. Methods: Questionnaires were administered to 300 consenting individuals to obtain demographic information and assessment of their risk of exposure to T. gondii. Using anti- T. gondii IgG/IgM combo test kits, seropositivity to parasite-specific IgG and/or IgM was determined. A haematological analyser was used to measure haematological parameters. Results: The participants included 58 males and 242 females, and ranged in age from 6 months to 84 years, with a median age of 27 years. There was an overall seroprevalence of 50.3% (n=151), with 49.7% (n=149) of the study participants seropositive for IgG and 1% (n=3) testing positive for IgM. Furthermore, the observed seroprevalence among pregnant women was 56.4% (n=62). With regards to the different communities in which the hospitals were located, a seroprevalence of 55.6% was observed in the rural community, 50.6% in the peri-urban community and 47.1% in the urban community. The study identified cat ownership, contact with cat litter [RR (95% CI: 1.76 (1.23-2.53), 1.66 (1.03-2.67), 1.25(1.00-1.57)] and age (p<0.001) as risk factors for infection. Analyses of haematological data also revealed significant differences between the red blood cell counts (p=0.038) and mean corpuscular volumes (p=0.0007) of seropositive and seronegative study participants. Conclusions: About half of the study population, including a significant number of women of reproductive age carried antibodies against T. gondii, raising questions about the risk of congenital toxoplasmosis, as well as possible links to anaemia. We, therefore, recommend that screening for Toxoplasma gondii be included in the routine screening of pregnant women seeking antenatal care.
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Affiliation(s)
- Samuel Kekeli Agordzo
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Kingsley Badu
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
- Kumasi Centre for Collaborative Research for Tropical Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Mathew Glover Addo
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Christian Kwasi Owusu
- Kumasi Centre for Collaborative Research for Tropical Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Abdul-Hakim Mutala
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Austine Tweneboah
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Dawood Ackom Abbas
- Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, AK 192, Ghana
| | - Nana Kwame Ayisi-Boateng
- School of Medicine and Dentistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
- The University Hospital, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
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9
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Safronova A, Araujo A, Camanzo ET, Moon TJ, Elliott MR, Beiting DP, Yarovinsky F. Alarmin S100A11 initiates a chemokine response to the human pathogen Toxoplasma gondii. Nat Immunol 2018; 20:64-72. [PMID: 30455460 PMCID: PMC6291348 DOI: 10.1038/s41590-018-0250-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 10/01/2018] [Indexed: 12/31/2022]
Abstract
Toxoplasma gondii is a common protozoan parasite that infects up to one-third of the world’s population. Notably, very little is known about innate immune-sensing mechanisms for this obligate intracellular parasite by human cells. Here, by applying an unbiased biochemical screening approach, we have identified that human monocytes recognized the presence of T. gondii infection via detection of the alarmin S100A11 protein, which is released from parasite-infected cells via caspase-1-dependent mechanisms. S100A11 induced a potent chemokine response to T. gondii via engagement of its receptor RAGE and regulated monocyte recruitment in vivo by inducing expression of the chemokine CCL2. Our experiments have revealed a sensing system for T. gondii by human cells that is based on detection infection-mediated release of alarmin S100A11 and RAGE-dependent induction of CCL2, a crucial chemokine required for host resistance to the parasite.
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Affiliation(s)
- Alexandra Safronova
- Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, USA
| | - Alessandra Araujo
- Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, USA
| | - Ellie T Camanzo
- Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, USA
| | - Taylor J Moon
- Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, USA
| | - Michael R Elliott
- Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, USA
| | - Daniel P Beiting
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Felix Yarovinsky
- Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, USA.
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10
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Abstract
Neutrophils are a major player in host immunity to infection; however, the mechanisms by which human neutrophils respond to the intracellular protozoan parasite Toxoplasma gondii are still poorly understood. In the current study, we found that, whereas primary human monocytes produced interleukin-1beta (IL-1β) in response to T. gondii infection, human neutrophils from the same blood donors did not. Moreover, T. gondii inhibited lipopolysaccharide (LPS)-induced IL-1β synthesis in human peripheral blood neutrophils. IL-1β suppression required active parasite invasion, since heat-killed or mycalolide B-treated parasites did not inhibit IL-1β release. By investigating the mechanisms involved in this process, we found that T. gondii infection of neutrophils treated with LPS resulted in reduced transcript levels of IL-1β and NLRP3 and reduced protein levels of pro-IL-1β, mature IL-1β, and the inflammasome sensor NLRP3. In T. gondii-infected neutrophils stimulated with LPS, the levels of MyD88, TRAF6, IKKα, IKKβ, and phosphorylated IKKα/β were not affected. However, LPS-induced IκBα degradation and p65 phosphorylation were reduced in T. gondii-infected neutrophils, and degradation of IκBα was reversed by treatment with the proteasome inhibitor MG-132. Finally, we observed that T. gondii inhibited the cleavage and activity of caspase-1 in human neutrophils. These results indicate that T. gondii suppression of IL-1β involves a two-pronged strategy whereby T. gondii inhibits both NF-κB signaling and activation of the NLRP3 inflammasome. These findings represent a novel mechanism of T. gondii evasion of human neutrophil-mediated host defense by targeting the production of IL-1β. Toxoplasma gondii is an obligate intracellular parasite that infects approximately one-third of humans worldwide and can invade virtually any nucleated cell in the human body. Although it is well documented that neutrophils infiltrate the site of acute T. gondii infection, there is limited understanding of how human neutrophils respond to T. gondii. Neutrophils control infectious pathogens by a variety of mechanisms, including the release of the cytokine IL-1β, a major driver of inflammation during infection. This study reveals that T. gondii is able to inhibit IL-1β production in human neutrophils by impairing the activation of the NF-κB signaling pathway and by inhibiting the inflammasome, the protein complex responsible for IL-1β maturation. This two-pronged strategy of targeting the IL-1β pathway may facilitate the survival and spread of T. gondii during acute infection.
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11
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Molecular mechanisms that mediate invasion and egress of malaria parasites from red blood cells. Curr Opin Hematol 2017; 24:208-214. [PMID: 28306665 DOI: 10.1097/moh.0000000000000334] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE OF REVIEW Malaria parasites invade and multiply in diverse host cells during their complex life cycle. Some blood stage parasites transform into male and female gametocytes that are transmitted by female anopheline mosquitoes. The gametocytes are activated in the mosquito midgut to form male and female gametes, which egress from RBCs to mate and form a zygote. Here, we will review our current understanding of the molecular mechanisms that mediate invasion and egress by malaria parasites at different life cycle stages. RECENT FINDINGS A number of key effector molecules such as parasite protein ligands for receptor-engagement during invasion as well as proteases and perforin-like proteins that mediate egress have been identified. Interestingly, these parasite-encoded effectors are located in internal, vesicular organelles and are secreted in a highly regulated manner during invasion and egress. Here, we will review our current understanding of the functional roles of these effectors as well as the signaling pathways that regulate their timely secretion with accurate spatiotemporal coordinates. SUMMARY Understanding the molecular basis of key processes such as host cell invasion and egress by malaria parasites could provide novel targets for development of inhibitors to block parasite growth and transmission.
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12
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Singh S, Chitnis CE. Molecular Signaling Involved in Entry and Exit of Malaria Parasites from Host Erythrocytes. Cold Spring Harb Perspect Med 2017; 7:cshperspect.a026815. [PMID: 28507195 DOI: 10.1101/cshperspect.a026815] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
During the blood stage, Plasmodium spp. merozoites invade host red blood cells (RBCs), multiply, exit, and reinvade uninfected RBCs in a continuing cycle that is responsible for all the clinical symptoms associated with malaria. Entry into (invasion) and exit from (egress) RBCs are highly regulated processes that are mediated by an array of parasite proteins with specific functional roles. Many of these parasite proteins are stored in specialized apical secretory vesicles, and their timely release is critical for successful invasion and egress. For example, the discharge of parasite protein ligands to the apical surface of merozoites is required for interaction with host receptors to mediate invasion, and the timely discharge of proteases and pore-forming proteins helps in permeabilization and dismantling of limiting membranes during egress. This review focuses on our understanding of the signaling mechanisms that regulate apical organelle secretion during host cell invasion and egress by malaria parasites. The review also explores how understanding key signaling mechanisms in the parasite can open opportunities to develop novel strategies to target Plasmodium parasites and eliminate malaria.
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Affiliation(s)
- Shailja Singh
- Department of Parasites and Insect Vectors, Institut Pasteur, 75015 Paris, France.,Shiv Nadar University, Gautam Buddha Nagar, Uttar Pradesh 201314, India
| | - Chetan E Chitnis
- Department of Parasites and Insect Vectors, Institut Pasteur, 75015 Paris, France.,Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi 110067, India
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13
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Tosh KW, Mittereder L, Bonne-Annee S, Hieny S, Nutman TB, Singer SM, Sher A, Jankovic D. The IL-12 Response of Primary Human Dendritic Cells and Monocytes to Toxoplasma gondii Is Stimulated by Phagocytosis of Live Parasites Rather Than Host Cell Invasion. THE JOURNAL OF IMMUNOLOGY 2015; 196:345-56. [PMID: 26597011 DOI: 10.4049/jimmunol.1501558] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/21/2015] [Indexed: 12/11/2022]
Abstract
As a major natural host for Toxoplasma gondii, the mouse is widely used for the study of the immune response to this medically important protozoan parasite. However, murine innate recognition of toxoplasma depends on the interaction of parasite profilin with TLR11 and TLR12, two receptors that are functionally absent in humans. This raises the question of how human cells detect and respond to T. gondii. In this study, we show that primary monocytes and dendritic cells from peripheral blood of healthy donors produce IL-12 and other proinflammatory cytokines when exposed to toxoplasma tachyzoites. Cell fractionation studies determined that IL-12 and TNF-α secretion is limited to CD16(+) monocytes and the CD1c(+) subset of dendritic cells. In direct contrast to their murine counterparts, human myeloid cells fail to respond to soluble tachyzoite extracts and instead require contact with live parasites. Importantly, we found that tachyzoite phagocytosis, but not host cell invasion, is required for cytokine induction. Together these findings identify CD16(+) monocytes and CD1c(+) dendritic cells as the major myeloid subsets in human blood-producing innate cytokines in response to T. gondii and demonstrate an unappreciated requirement for phagocytosis of live parasites in that process. This form of pathogen sensing is distinct from that used by mice, possibly reflecting a direct involvement of rodents and not humans in the parasite life cycle.
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Affiliation(s)
- Kevin W Tosh
- Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; Department of Biology, Georgetown University, Washington, DC 20057; and
| | - Lara Mittereder
- Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Sandra Bonne-Annee
- Helminth Immunology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Sara Hieny
- Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Thomas B Nutman
- Helminth Immunology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Steven M Singer
- Department of Biology, Georgetown University, Washington, DC 20057; and
| | - Alan Sher
- Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Dragana Jankovic
- Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892;
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14
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Gliding motility in apicomplexan parasites. Semin Cell Dev Biol 2015; 46:135-42. [DOI: 10.1016/j.semcdb.2015.09.020] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 09/25/2015] [Indexed: 11/22/2022]
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15
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Moreira-Souza ACA, Marinho Y, Correa G, Santoro GF, Coutinho CMLM, Vommaro RC, Coutinho-Silva R. Pyrimidinergic Receptor Activation Controls Toxoplasma gondii Infection in Macrophages. PLoS One 2015; 10:e0133502. [PMID: 26192447 PMCID: PMC4507979 DOI: 10.1371/journal.pone.0133502] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 06/29/2015] [Indexed: 12/20/2022] Open
Abstract
Infection by the protozoan parasite Toxoplasma gondii is highly prevalent worldwide and may have serious clinical manifestations in immunocompromised patients. T. gondii is an obligate intracellular parasite that infects almost any cell type in mammalian hosts, including immune cells. The immune cells express purinergic P2 receptors in their membrane--subdivided into P2Y and P2X subfamilies--whose activation is important for infection control. Here, we examined the effect of treatment with UTP and UDP in mouse peritoneal macrophages infected with T. gondii tachyzoites. Treatment with these nucleotides reduced parasitic load by 90%, but did not increase the levels of the inflammatory mediators NO and ROS, nor did it modulate host cell death by apoptosis or necrosis. On the other hand, UTP and UDP treatments induced early egress of tachyzoites from infected macrophages, in a Ca2+-dependent manner, as shown by scanning electron microscopy analysis, and videomicroscopy. In subsequent infections, prematurely egressed parasites had reduced infectivity, and could neither replicate nor inhibit the fusion of lysosomes to the parasitophorous vacuole. The use of selective agonists and antagonists of the receptor subtypes P2Y2 and P2Y4 and P2Y6 showed that premature parasite egress may be mediated by the activation of these receptor subtypes. Our results suggest that the activity of P2Y host cell receptors controls T. gondii infection in macrophages, highlighting the importance of pyrimidinergic signaling for innate immune system response against infection. Finally the P2Y receptors should be considered as new target for the development of drugs against T. gondii infection.
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MESH Headings
- Animals
- Apoptosis/drug effects
- Cells, Cultured
- Female
- Host-Parasite Interactions/drug effects
- Macrophages/metabolism
- Macrophages/parasitology
- Macrophages/ultrastructure
- Macrophages, Peritoneal/metabolism
- Macrophages, Peritoneal/parasitology
- Macrophages, Peritoneal/ultrastructure
- Male
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Microscopy, Electron, Scanning
- Microscopy, Electron, Transmission
- Microscopy, Fluorescence
- Nitric Oxide/metabolism
- Purinergic P2Y Receptor Agonists/pharmacology
- Purinergic P2Y Receptor Antagonists/pharmacology
- Reactive Oxygen Species/metabolism
- Receptors, Purinergic P2Y/metabolism
- Suramin/pharmacology
- Toxoplasma/physiology
- Uridine Diphosphate/pharmacology
- Uridine Triphosphate/pharmacology
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Affiliation(s)
- Aline Cristina Abreu Moreira-Souza
- Laboratório de Imunofisiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
- Instituto Nacional de Ciência e Tecnologia para Pesquisa Translacional em Saúde e Ambiente na Região Amazônica (INPeTAm/UFRJ), Rio de Janeiro, RJ, 21941–902, Brazil
| | - Ygor Marinho
- Laboratório de Imunofisiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
- Instituto Nacional de Ciência e Tecnologia para Pesquisa Translacional em Saúde e Ambiente na Região Amazônica (INPeTAm/UFRJ), Rio de Janeiro, RJ, 21941–902, Brazil
| | - Gladys Correa
- Laboratório de Imunofisiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
- Instituto Nacional de Ciência e Tecnologia para Pesquisa Translacional em Saúde e Ambiente na Região Amazônica (INPeTAm/UFRJ), Rio de Janeiro, RJ, 21941–902, Brazil
| | - Giani França Santoro
- Laboratório de Imunofisiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
- Laboratório de Inovações, Terapias, Ensino e Bioprodutos (LITEB), Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, 21.040–900, Brazil
- Instituto Nacional de Ciência e Tecnologia para Pesquisa Translacional em Saúde e Ambiente na Região Amazônica (INPeTAm/UFRJ), Rio de Janeiro, RJ, 21941–902, Brazil
| | - Claudia Mara Lara Melo Coutinho
- Laboratório de Inovações, Terapias, Ensino e Bioprodutos (LITEB), Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, 21.040–900, Brazil
- Instituto de Biologia, Universidade Federal Fluminense, Niterói, RJ, 24020–140, Brazil
| | - Rossiane Claudia Vommaro
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
| | - Robson Coutinho-Silva
- Laboratório de Imunofisiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941–902, Brazil
- Instituto Nacional de Ciência e Tecnologia para Pesquisa Translacional em Saúde e Ambiente na Região Amazônica (INPeTAm/UFRJ), Rio de Janeiro, RJ, 21941–902, Brazil
- * E-mail:
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16
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The Apicomplexan CDC/MACPF-like pore-forming proteins. Curr Opin Microbiol 2015; 26:48-52. [PMID: 26025132 DOI: 10.1016/j.mib.2015.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 05/01/2015] [Accepted: 05/06/2015] [Indexed: 11/22/2022]
Abstract
Pore-forming proteins (PFPs) encompass a broad family of proteins that are used for virulence or immune defense. Members of the cholesterol-dependent cytolysins (CDCs) and membrane attack complex/perforin (MACPF) family of PFPs form large β-barrel pores in the membrane. The CDC/MACPF proteins contain a characteristic four-stranded β-sheet that is flanked by two α-helical bundles, which unfold to form two transmembrane β-hairpins. Apicomplexan eukaryotic parasites express CDC/MACPFs termed perforin-like proteins (PLPs). Here we review recent studies that provide key insights into the assembly and regulation of the Apicomplexan PLP (ApiMACPF) molecular pore-forming mechanisms, which are necessary for the osmotically driven rupture of the parasitophorous vacuole and host cell membrane, and cell traversal by these parasites.
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17
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Randall LM, Hunter CA. Parasite dissemination and the pathogenesis of toxoplasmosis. Eur J Microbiol Immunol (Bp) 2014; 1:3-9. [PMID: 24466431 DOI: 10.1556/eujmi.1.2011.1.3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- L M Randall
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania Hill Pavilion, 380 South University Avenue, Philadelphia, PA 19146 USA
| | - C A Hunter
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania Hill Pavilion, 380 South University Avenue, Philadelphia, PA 19146 USA
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18
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Treeck M, Sanders JL, Gaji RY, LaFavers KA, Child MA, Arrizabalaga G, Elias JE, Boothroyd JC. The calcium-dependent protein kinase 3 of toxoplasma influences basal calcium levels and functions beyond egress as revealed by quantitative phosphoproteome analysis. PLoS Pathog 2014; 10:e1004197. [PMID: 24945436 PMCID: PMC4063958 DOI: 10.1371/journal.ppat.1004197] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 05/05/2014] [Indexed: 12/19/2022] Open
Abstract
Calcium-dependent protein kinases (CDPKs) are conserved in plants and apicomplexan parasites. In Toxoplasma gondii, TgCDPK3 regulates parasite egress from the host cell in the presence of a calcium-ionophore. The targets and the pathways that the kinase controls, however, are not known. To identify pathways regulated by TgCDPK3, we measured relative phosphorylation site usage in wild type and TgCDPK3 mutant and knock-out parasites by quantitative mass-spectrometry using stable isotope-labeling with amino acids in cell culture (SILAC). This revealed known and novel phosphorylation events on proteins predicted to play a role in host-cell egress, but also a novel function of TgCDPK3 as an upstream regulator of other calcium-dependent signaling pathways, as we also identified proteins that are differentially phosphorylated prior to egress, including proteins important for ion-homeostasis and metabolism. This observation is supported by the observation that basal calcium levels are increased in parasites where TgCDPK3 has been inactivated. Most of the differential phosphorylation observed in CDPK3 mutants is rescued by complementation of the mutants with a wild type copy of TgCDPK3. Lastly, the TgCDPK3 mutants showed hyperphosphorylation of two targets of a related calcium-dependent kinase (TgCDPK1), as well as TgCDPK1 itself, indicating that this latter kinase appears to play a role downstream of TgCDPK3 function. Overexpression of TgCDPK1 partially rescues the egress phenotype of the TgCDPK3 mutants, reinforcing this conclusion. These results show that TgCDPK3 plays a pivotal role in regulating tachyzoite functions including, but not limited to, egress.
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Affiliation(s)
- Moritz Treeck
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - John L. Sanders
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Rajshekhar Y. Gaji
- Department of Pharmacology and Toxicology, School of Medicine, University of Indianapolis, Indianapolis, Indiana, United States of America
| | - Kacie A. LaFavers
- Department of Pharmacology and Toxicology, School of Medicine, University of Indianapolis, Indianapolis, Indiana, United States of America
| | - Matthew A. Child
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Gustavo Arrizabalaga
- Department of Pharmacology and Toxicology, School of Medicine, University of Indianapolis, Indianapolis, Indiana, United States of America
| | - Joshua E. Elias
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California, United States of America
| | - John C. Boothroyd
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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19
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Abstract
A wide spectrum of pathogenic bacteria and protozoa has adapted to an intracellular life-style, which presents several advantages, including accessibility to host cell metabolites and protection from the host immune system. Intracellular pathogens have developed strategies to enter and exit their host cells while optimizing survival and replication, progression through the life cycle, and transmission. Over the last decades, research has focused primarily on entry, while the exit process has suffered from neglect. However, pathogen exit is of fundamental importance because of its intimate association with dissemination, transmission, and inflammation. Hence, to fully understand virulence mechanisms of intracellular pathogens at cellular and systemic levels, it is essential to consider exit mechanisms to be a key step in infection. Exit from the host cell was initially viewed as a passive process, driven mainly by physical stress as a consequence of the explosive replication of the pathogen. It is now recognized as a complex, strategic process termed "egress," which is just as well orchestrated and temporally defined as entry into the host and relies on a dynamic interplay between host and pathogen factors. This review compares egress strategies of bacteria, pathogenic yeast, and kinetoplastid and apicomplexan parasites. Emphasis is given to recent advances in the biology of egress in mycobacteria and apicomplexans.
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20
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Szumowski SC, Estes KA, Troemel ER. Preparing a discreet escape: Microsporidia reorganize host cytoskeleton prior to non-lytic exit from C. elegans intestinal cells. WORM 2013; 1:207-11. [PMID: 24058850 PMCID: PMC3670220 DOI: 10.4161/worm.20501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 04/24/2012] [Indexed: 11/25/2022]
Abstract
Intracellular pathogens commonly invade and replicate inside of intestinal cells and exit from these cells is a crucial step in pathogen transmission. For convenience, studies of intracellular pathogens are often conducted using in vitro cell culture systems, which unfortunately lack important features of polarized, intact intestinal epithelial cells. The nematode C. elegans provides a tractable system to study intracellular pathogens in vivo, where features of differentiated epithelial cells are easily visualized. In a recent paper, we used C. elegans as a host organism to study the exit strategy of Nematocida parisii, a naturally occurring intracellular pathogen in the microsporidia phylum. We showed that N. parisii remodels the C. elegans host cytoskeleton, and then exits host cells in an actin-dependent, non-lytic fashion. These findings illuminate key details about the transmission of microsporidia, which are poorly understood but ubiquitous pathogens. More generally, these findings have implications for exit strategies used by other intracellular pathogens that also infect epithelial cells.
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Affiliation(s)
- Suzannah C Szumowski
- Division of Biological Sciences; Section of Cell and Developmental Biology; University of California San Diego; La Jolla, CA USA
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21
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Blackman MJ, Carruthers VB. Recent insights into apicomplexan parasite egress provide new views to a kill. Curr Opin Microbiol 2013; 16:459-64. [PMID: 23725669 PMCID: PMC3755044 DOI: 10.1016/j.mib.2013.04.008] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 04/23/2013] [Accepted: 04/25/2013] [Indexed: 01/20/2023]
Abstract
A hallmark of apicomplexan pathogens such as Plasmodium, Toxoplasma and Cryptosporidium is that they invade, replicate within, and then egress from their host cells. Egress usually results in lysis of the host cell, with deleterious consequences for the host. In the case of malaria, for example, much of the disease pathology is associated with cyclical waves of host erythrocyte destruction. This review highlights recent advances in mapping the signaling pathways that lead to egress and the parasite molecules involved in responding to and transmitting those signals. The review also discusses new findings for effector molecules that mediate disruption of the bounding membranes that enclose the intracellular parasite and the manner in which membrane rupture occurs to finally release invasive forms of the parasite.
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Affiliation(s)
- Michael J. Blackman
- Division of Parasitology, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
| | - Vern B. Carruthers
- Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-5620
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22
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Human innate immunity to Toxoplasma gondii is mediated by host caspase-1 and ASC and parasite GRA15. mBio 2013; 4:mBio.00255-13. [PMID: 23839215 PMCID: PMC3705447 DOI: 10.1128/mbio.00255-13] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Interleukin-1β (IL-1β) functions as a key regulator of inflammation and innate immunity. The protozoan parasite Toxoplasma gondii actively infects human blood monocytes and induces the production of IL-1β; however, the host and parasite factors that mediate IL-1β production during T. gondii infection are poorly understood. We report that T. gondii induces IL-1β transcript, processing/cleavage, and release from infected primary human monocytes and THP-1 cells. Treating monocytes with the caspase-1 inhibitor Ac-YVAD-CMK reduced IL-1β release, suggesting a role for the inflammasome in T. gondii-induced IL-1β production. This was confirmed by performing short hairpin RNA (shRNA) knockdown of caspase-1 and of the inflammasome adaptor protein ASC. IL-1β induction required active parasite invasion of monocytes, since heat-killed or mycalolide B-treated parasites did not induce IL-1β. Among the type I, II, and III strains of T. gondii, the type II strain induced substantially more IL-1β mRNA and protein release than did the type I and III strains. Since IL-1β transcript is known to be induced downstream of NF-κB signaling, we investigated a role for the GRA15 protein, which induces sustained NF-κB signaling in a parasite strain-specific manner. By infecting human monocytes with a GRA15-knockout type II strain and a type I strain stably expressing type II GRA15, we determined that GRA15 is responsible for IL-1β induction during T. gondii infection of human monocytes. This research defines a pathway driving human innate immunity by describing a role for the classical inflammasome components caspase-1 and ASC and the parasite GRA15 protein in T. gondii-induced IL-1β production. IMPORTANCE Monocytes are immune cells that protect against infection by increasing inflammation and antimicrobial activities in the body. Upon infection with the parasitic pathogen Toxoplasma gondii, human monocytes release interleukin-1β (IL-1β), a "master regulator" of inflammation, which amplifies immune responses. Although inflammatory responses are critical for host defense against infection, excessive inflammation can result in tissue damage and pathology. This delicate balance underscores the importance of understanding the mechanisms that regulate IL-1β during infection. We have investigated the molecular pathway by which T. gondii induces the synthesis and release of IL-1β in human monocytes. We found that specific proteins in the parasite and the host cell coordinate to induce IL-1β production. This research is significant because it contributes to a greater understanding of human innate immunity to infection and IL-1β regulation, thereby enhancing our potential to modulate inflammation in the body.
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23
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Garrison E, Treeck M, Ehret E, Butz H, Garbuz T, Oswald BP, Settles M, Boothroyd J, Arrizabalaga G. A forward genetic screen reveals that calcium-dependent protein kinase 3 regulates egress in Toxoplasma. PLoS Pathog 2012; 8:e1003049. [PMID: 23209419 PMCID: PMC3510250 DOI: 10.1371/journal.ppat.1003049] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 10/08/2012] [Indexed: 12/26/2022] Open
Abstract
Egress from the host cell is a crucial and highly regulated step in the biology of the obligate intracellular parasite, Toxoplasma gondii. Active egress depends on calcium fluxes and appears to be a crucial step in escaping the attack from the immune system and, potentially, in enabling the parasites to shuttle into appropriate cells for entry into the brain of the host. Previous genetic screens have yielded mutants defective in both ionophore-induced egress and ionophore-induced death. Using whole genome sequencing of one mutant and subsequent analysis of all mutants from these screens, we find that, remarkably, four independent mutants harbor a mis-sense mutation in the same gene, TgCDPK3, encoding a calcium-dependent protein kinase. All four mutations are predicted to alter key regions of TgCDPK3 and this is confirmed by biochemical studies of recombinant forms of each. By complementation we confirm a crucial role for TgCDPK3 in the rapid induction of parasite egress and we establish that TgCDPK3 is critical for formation of latent stages in the brains of mice. Genetic knockout of TgCDPK3 confirms a crucial role for this kinase in parasite egress and a non-essential role for it in the lytic cycle. Toxoplasma gondii, an important human pathogen, is an obligate intracellular parasite, thus getting in and out of cells is key for its survival. The process by which Toxoplasma exits cells, known as egress, is controlled by calcium fluxes and can be triggered by ionophores. In vivo, rapid egress from the host cell has been identified as a means to escape attack by the innate immune system. At the molecular level, calcium dependent events in this parasite are regulated in part by plant like calcium dependent kinases, which share no homology to human kinases and are thus ideal drug targets. In this study we revisited 4 mutant parasite lines that were independently selected for an inability to undergo egress in response to ionophores. In all four mutants we have identified the Calcium Dependent Kinase 3 as the gene responsible for the defects. We have shown that two of these mutants, which are in a genetic background that allows virulence studies, also have a strong phenotype in vivo. That is, the parasites fail to form latent stages in mice. This work provides important information that a single kinase is responsible for the formation of latent stages that are important for transmission of the parasite.
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Affiliation(s)
- Erin Garrison
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, United States of America
| | - Moritz Treeck
- Stanford University School of Medicine, Department of Microbiology and Immunology, Stanford, California, United States of America
| | - Emma Ehret
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, United States of America
| | - Heidi Butz
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, United States of America
| | - Tamila Garbuz
- Indiana University School of Medicine, Department of Pharmacology and Toxicology, Indianapolis, Indiana, United States of America
| | - Benji P. Oswald
- University of Idaho, The Institute for Bioinformatics and Evolutionary Studies, Moscow, Idaho, United States of America
| | - Matt Settles
- University of Idaho, The Institute for Bioinformatics and Evolutionary Studies, Moscow, Idaho, United States of America
| | - John Boothroyd
- Stanford University School of Medicine, Department of Microbiology and Immunology, Stanford, California, United States of America
| | - Gustavo Arrizabalaga
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, United States of America
- Indiana University School of Medicine, Department of Pharmacology and Toxicology, Indianapolis, Indiana, United States of America
- * E-mail:
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24
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Enhanced egress of intracellular Eimeria tenella sporozoites by splenic lymphocytes from coccidian-infected chickens. Infect Immun 2011; 79:3465-70. [PMID: 21628515 DOI: 10.1128/iai.01334-10] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Egress, which describes the mechanism that some intracellular parasites use to exit from parasitophorous vacuoles and host cells, plays a very important role in the parasite life cycle and is central to Eimeria propagation and pathogenesis. Despite the importance of egress in the intracellular parasite's life cycle, very little information is known on this process compared to other steps, e.g., invasion. The present study was conducted to investigate the interplay between the host adaptive immune system and Eimeria egression. Splenic lymphocytes or soluble immune factors were incubated with parasite-infected host cells for 3 or 5 h, and the percentage of egress was calculated according to an established formula. Viability of egressed parasites and host cells was tested using trypan blue exclusion and annexin V and propidium iodide staining, respectively. We found that premature egression of sporozoites from Eimeria tenella-infected primary chicken kidney cells or from chicken peripheral blood mononuclear cells occurred when the cells were cocultured in vitro with spleen lymphocytes from E. tenella-infected chickens but not when they were cocultured with splenocytes from uninfected chickens. Eimeria-specific antibodies and cytokines (gamma interferon [IFN-γ], interleukin-2 [IL-2], and IL-15), derived from E. tenella-primed B and T lymphocytes, respectively, were capable of promoting premature egress of sporozoites from infected host cells. Both egressed parasites and host cells were viable, although the latter showed reduced reinvasion ability. These results suggest a novel, immune-mediated mechanism that the host exploits to interrupt the normal Eimeria life cycle in vivo and thereby block the release of mature parasites into the environment.
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25
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Gaji RY, Behnke MS, Lehmann MM, White MW, Carruthers VB. Cell cycle-dependent, intercellular transmission of Toxoplasma gondii is accompanied by marked changes in parasite gene expression. Mol Microbiol 2010; 79:192-204. [PMID: 21166903 DOI: 10.1111/j.1365-2958.2010.07441.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Intracellular microbes have evolved efficient strategies for transitioning from one cell to another in a process termed intercellular transmission. Here we show that host cell transmission of the obligate intracellular parasite Toxoplasma gondii is closely tied to specific cell cycle distributions, with egress and reinvasion occurring most proficiently by parasites in the G1 phase. We also reveal that Toxoplasma undergoes marked changes in mRNA expression when transitioning from the extracellular environment to its intracellular niche. These mRNA level changes reflect a modal switch from expression of proteins involved in invasion, motility and signal transduction in extracellular parasites to expression of metabolic and DNA replication proteins in intracellular parasites. Host cell binding and signalling associated with the discharge of parasite secretory proteins was not sufficient to induce this switch in gene expression, suggesting that the regulatory mechanisms responsible are tied to the establishment of the intracellular environment. The genes whose expression increased after parasite invasion belong to a progressive cascade known to underlie the parasite division cycle indicating that the unique relationship between the G1 phase and invasion effectively synchronizes short-term population growth. This work provides new insight into how this highly successful parasite competently transits from cell to cell.
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Affiliation(s)
- Rajshekhar Y Gaji
- Department of Microbiology and Immunology, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA
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Bottova I, Sauder U, Olivieri V, Hehl AB, Sonda S. The P-glycoprotein inhibitor GF120918 modulates Ca2+-dependent processes and lipid metabolism in Toxoplasma gondii. PLoS One 2010; 5:e10062. [PMID: 20386707 PMCID: PMC2851653 DOI: 10.1371/journal.pone.0010062] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 03/15/2010] [Indexed: 11/18/2022] Open
Abstract
Up-regulation of the membrane-bound efflux pump P-glycoprotein (P-gp) is associated with the phenomenon of multidrug-resistance in pathogenic organisms, including protozoan parasites. In addition, P-gp plays a role in normal physiological processes, however our understanding of these P-gp functions remains limited. In this study we investigated the effects of the P-gp inhibitor GF120918 in Toxoplasma gondii, a model apicomplexan parasite and an important human pathogen. We found that GF120918 treatment severely inhibited parasite invasion and replication. Further analyses of the molecular mechanisms involved revealed that the P-gp inhibitor modulated parasite motility, microneme secretion and egress from the host cell, all cellular processes known to depend on Ca2+ signaling in the parasite. In support of a potential role of P-gp in Ca2+-mediated processes, immunoelectron and fluorescence microscopy showed that T. gondii P-gp was localized in acidocalcisomes, the major Ca2+ storage in the parasite, at the plasma membrane, and in the intravacuolar tubular network. In addition, metabolic labeling of extracellular parasites revealed that inhibition or down-regulation of T. gondii P-gp resulted in aberrant lipid synthesis. These results suggest a crucial role of T. gondii P-gp in essential processes of the parasite biology and further validate the potential of P-gp activity as a target for drug development.
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Affiliation(s)
- Iveta Bottova
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
| | | | | | - Adrian B. Hehl
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
| | - Sabrina Sonda
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
- * E-mail:
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Tomita T, Yamada T, Weiss LM, Orlofsky A. Externally triggered egress is the major fate of Toxoplasma gondii during acute infection. THE JOURNAL OF IMMUNOLOGY 2009; 183:6667-80. [PMID: 19846885 DOI: 10.4049/jimmunol.0900516] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The apicomplexan parasite Toxoplasma gondii expands during acute infection via a cycle of invasion, intracellular replication, and lytic egress. Physiological regulation has not yet been demonstrated for either invasion or egress. We now report that, in contrast to cell culture systems, in which egress occurs only after five or more parasite divisions (2-3 days), intracellular residence is strikingly abbreviated in inflammatory cells in vivo, and early egress (after zero to two divisions) is the dominant parasite fate in acutely infected mice. Adoptive transfer experiments demonstrate rapid, reciprocal, kinetically uniform parasite transfer between donor and recipient compartments, with a t(1/2) of approximately 3 h. Inflammatory macrophages are major participants in this cycle of lytic egress and reinfection, which drives rapid macrophage turnover. Inflammatory triggering cells, principally macrophages, elicit egress in infected target macrophages, a process we term externally triggered egress (ETE). The mechanism of ETE does not require reactive oxygen or nitrogen species, the mitochondrial permeability transition pore, or a variety of signal transduction mediators, but is dependent on intracellular calcium and is highly sensitive to SB203580, an inhibitor of p38 MAPK as well as a related parasite-encoded kinase. SB203580 both inhibited the initiation of ETE and altered the progression of egress. Parasites recently completing a cycle of egress and reinfection were preferentially restricted in vivo, supporting a model in which ETE may favor host defense by a process of haven disruption. ETE represents a novel example of interaction between a parasite infectious cycle and host microenvironment.
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Affiliation(s)
- Tadakimi Tomita
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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28
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Caldas LA, de Souza W, Attias M. Microscopic analysis of calcium ionophore activated egress of Toxoplasma gondii from the host cell. Vet Parasitol 2009; 167:8-18. [PMID: 19875235 DOI: 10.1016/j.vetpar.2009.09.051] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 09/09/2009] [Accepted: 09/28/2009] [Indexed: 11/17/2022]
Abstract
Toxoplasma gondii invades and destroys nucleated cells of warm blooded hosts in a process which involves several steps: recognition, adhesion, penetration, multiplication inside a parasitophorous vacuole (PV) and egress. The last one is the least understood. Parasite egress from LLC-MK2 cells infected with the RH strain of T. gondii was artificially triggered with 4BrA23187 calcium ionophore. The combination of videomicroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) showed that egress does not result from host cell rupture due to overloading with tachyzoites. Videomicroscopy showed that upon calcium ionophore administration parasite rosettes disassemble, the contour of the parasitophorous vacuole disappears and each tachyzoite takes a separate route to the extracellular medium. FESEM and TEM showed the fragmentation of the intravacuolar network, the fragmentation of parasitophorous vacuole membrane and individual tachyzoites with extruded conoids migrating through the cytosol, tightly surrounded by remnants of parasitophorous vacuole membrane or free in the cytosol. Both videomicroscopy and FESEM showed that a single parasite can cross the host cell membrane without disrupting it, while a large number of parasites, egressing simultaneously, rupture the membrane and the cell as a whole. These data suggest that invasion and egress share less similarities than previously believed.
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Affiliation(s)
- Lucio Ayres Caldas
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil
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29
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Frénal K, Soldati-Favre D. Role of the parasite and host cytoskeleton in apicomplexa parasitism. Cell Host Microbe 2009; 5:602-11. [PMID: 19527887 DOI: 10.1016/j.chom.2009.05.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 05/22/2009] [Accepted: 05/28/2009] [Indexed: 11/25/2022]
Abstract
The phylum Apicomplexa includes a large and diverse group of obligate intracellular parasites that rely on actomyosin-based motility to migrate, enter host cells, and egress from infected cells. To ensure their intracellular survival and replication, the apicomplexans have evolved sophisticated strategies for subversion of the host cytoskeleton. Given the properties in common between the host and parasite cytoskeleton, dissecting their individual contribution to the establishment of parasitic infection has been challenging. Nevertheless, recent studies have provided new insights into the mechanisms by which parasites subvert the dynamic properties of host actin and tubulin to promote their entry, development, and egress.
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Affiliation(s)
- Karine Frénal
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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30
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Abstract
Egress is a pivotal step in the life cycle of intracellular pathogens initiating the transition from an expiring host cell to a fresh target cell. While much attention has been focused on understanding cell invasion by intracellular pathogens, recent work is providing a new appreciation of mechanisms and therapeutic potential of microbial egress. This review highlights recent insight into cell egress by apicomplexan parasites and emerging contributions of membranolytic and proteolytic secretory products, along with host proteases. New findings suggest that Toxoplasma gondii secretes a pore-forming protein, TgPLP1, during egress that facilitates parasite escape from the cell by perforating the parasitophorous membrane. Also, in a cascade of proteolytic events, Plasmodium falciparum late-stage schizonts activate and secrete a subtilisin, PfSUB1, which processes enigmatic putative proteases called serine-repeat antigens that contribute to merozoite egress. A new report also suggests that calcium-activated host proteases called calpains aid parasite exit, possibly by acting upon the host cytoskeleton. Together these discoveries reveal important new molecular players involved in the principal steps of egress by apicomplexans.
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Affiliation(s)
- Marijo S Roiko
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, 48109, USA
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31
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Blader IJ, Saeij JP. Communication between Toxoplasma gondii and its host: impact on parasite growth, development, immune evasion, and virulence. APMIS 2009; 117:458-76. [PMID: 19400868 DOI: 10.1111/j.1600-0463.2009.02453.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Toxoplasma gondii is an obligate intracellular protozoan parasite that can infect most warm-blooded animals and cause severe and life-threatening disease in developing fetuses and in immune-compromised patients. Although Toxoplasma was discovered over 100 years ago, we are only now beginning to appreciate the importance of the role that parasite modulation of its host has on parasite growth, bradyzoite development, immune evasion, and virulence. The goal of this review is to highlight these findings, to develop an integrated model for communication between Toxoplasma and its host, and to discuss new questions that arise out of these studies.
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Affiliation(s)
- Ira J Blader
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
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Santos JM, Lebrun M, Daher W, Soldati D, Dubremetz JF. Apicomplexan cytoskeleton and motors: key regulators in morphogenesis, cell division, transport and motility. Int J Parasitol 2008; 39:153-62. [PMID: 19028497 DOI: 10.1016/j.ijpara.2008.10.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Revised: 10/13/2008] [Accepted: 10/16/2008] [Indexed: 10/21/2022]
Abstract
Protozoan parasites of the phylum Apicomplexa undergo a lytic cycle whereby a single zoite produced by the previous cycle has to encounter a host cell, invade it, multiply to differentiate into a new zoite generation and escape to resume a new cycle. At every step of this lytic cycle, the cytoskeleton and/or the gliding motility apparatus play a crucial role and recent results have elucidated aspects of these processes, especially in terms of the molecular characterization and interaction of the increasing number of partners involved, and the signalling mechanisms implicated. The present review aims to summarize the most recent findings in the field.
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Affiliation(s)
- Joana M Santos
- Department of Microbiology and Molecular Medicine, Faculty of Medicine-University of Geneva CMU, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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Wendelken JL, Rowland EC. Agglutination of Trypanosoma cruzi in infected cells treated with serum from chronically infected mice. J Parasitol 2008; 95:337-44. [PMID: 18922039 DOI: 10.1645/ge-1757.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Accepted: 10/06/2008] [Indexed: 11/10/2022] Open
Abstract
The protozoan parasite Trypanosoma cruzi is the causative agent of Chagas disease. The chronic stage of infection is characterized by a production of neutralizing antibodies in the vertebrate host. A polyclonal antibody, anti-egressin, has been found to inhibit egress of parasites from the host cell late in the intracellular cycle, after the parasites have transformed from the replicative amastigote into the trypomastigote. It has also been found that BALB/c mouse fibroblasts in the late stages of parasite infection become permeable to molecules as large as antibodies, leading to the possibility that anti-egressin affects the intracellular parasites. This project addresses the fate of the intracellular trypomastigotes that have been inhibited from egressing the host cell. Extended cultures of infected fibroblasts treated with chronic mouse serum reduced parasite egress at all time points measured. Parasites released from infected fibroblasts treated with chronic serum had a reduced ability to infect fibroblasts in culture, yet did not lose infectivity entirely. Absorption of chronic serum with living trypomastigotes removed the anti-egressin effect. The possibility that the target of anti-egressin is a parasite surface component is further indicated by the agglutination of extracellular trypomastigotes by chronic serum. The possibility that cross-linking by antibody occurs intracellularly, thus inhibiting egress, was reinforced by cleaving purified IgG into Fab fragments, which did not inhibit egress when added to infected cultures. From this work, it is proposed that the current, best explanation of the mechanism of egress inhibition by anti-egressin is intracellular agglutination, preventing normal parasite-driven egress.
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Affiliation(s)
- Jennifer L Wendelken
- Tropical Disease Institute, Ohio University College of Osteopathic Medicine, Athens, Ohio 45701, USA
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Plattner F, Yarovinsky F, Romero S, Didry D, Carlier MF, Sher A, Soldati-Favre D. Toxoplasma profilin is essential for host cell invasion and TLR11-dependent induction of an interleukin-12 response. Cell Host Microbe 2008; 3:77-87. [PMID: 18312842 DOI: 10.1016/j.chom.2008.01.001] [Citation(s) in RCA: 261] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 11/14/2007] [Accepted: 01/08/2008] [Indexed: 11/24/2022]
Abstract
Apicomplexan parasites exhibit actin-dependent gliding motility that is essential for migration across biological barriers and host cell invasion. Profilins are key contributors to actin polymerization, and the parasite Toxoplasma gondii possesses a profilin-like protein that is recognized by Toll-like receptor TLR11 in the host innate immune system. Here, we show by conditional disruption of the corresponding gene that T.gondii profilin, while not required for intracellular growth, is indispensable for gliding motility, host cell invasion, active egress from host cells, and virulence in mice. Furthermore, parasites lacking profilin are unable to induce TLR11-dependent production in vitro and in vivo of the defensive host cytokine interleukin-12. Thus, profilin is an essential element of two aspects of T. gondii infection. Like bacterial flagellin, profilin plays a role in motility while serving as a microbial ligand recognized by the host innate immune system.
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Affiliation(s)
- Fabienne Plattner
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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