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Ilyas M, Stapleton F, Willcox MDP, Henriquez F, Peguda HK, Rayamajhee B, Zahid T, Petsoglou C, Carnt NA. Epidemiology of and Genetic Factors Associated with Acanthamoeba Keratitis. Pathogens 2024; 13:142. [PMID: 38392880 PMCID: PMC10892102 DOI: 10.3390/pathogens13020142] [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: 12/15/2023] [Revised: 01/14/2024] [Accepted: 01/31/2024] [Indexed: 02/25/2024] Open
Abstract
Acanthamoeba keratitis (AK) is a severe, rare protozoal infection of the cornea. Acanthamoeba can survive in diverse habitats and at extreme temperatures. AK is mostly seen in contact lens wearers whose lenses have become contaminated or who have a history of water exposure, and in those without contact lens wear who have experienced recent eye trauma involving contaminated soil or water. Infection usually results in severe eye pain, photophobia, inflammation, and corneal epithelial defects. The pathophysiology of this infection is multifactorial, including the production of cytotoxic proteases by Acanthamoeba that degrades the corneal epithelial basement membrane and induces the death of ocular surface cells, resulting in degradation of the collagen-rich corneal stroma. AK can be prevented by avoiding risk factors, which includes avoiding water contact, such as swimming or showering in contact lenses, and wearing protective goggles when working on the land. AK is mostly treated with an antimicrobial therapy of biguanides alone or in combination with diaminidines, although the commercial availability of these medicines is variable. Other than anti-amoeba therapies, targeting host immune pathways in Acanthamoeba disease may lead to the development of vaccines or antibody therapeutics which could transform the management of AK.
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Affiliation(s)
- Muhammad Ilyas
- Primary & Secondary Healthcare Department, Punjab 54000, Pakistan; (M.I.)
| | - Fiona Stapleton
- School of Optometry and Vision Science, University of NSW, Sydney, NSW 2052, Australia (H.K.P.)
| | - Mark D. P. Willcox
- School of Optometry and Vision Science, University of NSW, Sydney, NSW 2052, Australia (H.K.P.)
| | - Fiona Henriquez
- School of Health and Life Sciences, The University of the West of Scotland, Glasgow G72 0LH, UK
| | - Hari Kumar Peguda
- School of Optometry and Vision Science, University of NSW, Sydney, NSW 2052, Australia (H.K.P.)
| | - Binod Rayamajhee
- School of Optometry and Vision Science, University of NSW, Sydney, NSW 2052, Australia (H.K.P.)
| | - Tasbiha Zahid
- Primary & Secondary Healthcare Department, Punjab 54000, Pakistan; (M.I.)
| | | | - Nicole A. Carnt
- School of Optometry and Vision Science, University of NSW, Sydney, NSW 2052, Australia (H.K.P.)
- Centre for Vision Research, Westmead Institute for Medical Research, Sydney, NSW 2145, Australia
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SLAMF7/STAT6 Pathway Inhibits Innate Immune Response in Late-Stage Human Acanthamoeba Keratitis: A Comparative Transcriptome Analysis. Microorganisms 2023; 11:microorganisms11020365. [PMID: 36838330 PMCID: PMC9961001 DOI: 10.3390/microorganisms11020365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/27/2023] [Accepted: 01/29/2023] [Indexed: 02/05/2023] Open
Abstract
Acanthamoeba keratitis (AK) is a blinding corneal infection caused by the protozoan Acanthamoeba. The long-term course of AK suggests the host immunity could not kill Acanthamoeba rapidly. The immune status is still unclear in the late stage of AK. The comparative transcriptome analysis was made based on the bulk RNA sequencing of cornea tissues from AK patients and donors. Differentially expressed genes and enriched signaling pathways were calculated. CIBERSORT algorithm was used for immune infiltration analysis of cornea tissue between AK and normal controls. A total of 2668 differentially expressed genes, including 1477 upregulated genes and 1191 downregulated genes, were detected. Gene Ontology analysis revealed that the pathways were significantly enriched in leukocyte migration, regulation of T-cell activation, the external side of plasma membrane, collagen-containing extracellular matrix, immune receptor activity, and cytokine binding. The Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the pathways were significantly enriched in the cytokine-cytokine receptor interaction, hematopoietic cell lineage, and Staphylococcus aureus infection pathway. The immune infiltration profiles varied little between AK and normal controls. Compared with normal tissue, cornea tissue of AK contained a higher proportion of M0 macrophages and CD8 T cells, while resting memory CD4 T cells contributed to a relatively lower portion (p < 0.05). Finally, the expression levels of cell markers and SLAMF7/STAT6 pathway were confirmed by histopathology examinations, RT-qPCR, and Western blot.
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Various brain-eating amoebae: the protozoa, the pathogenesis, and the disease. Front Med 2021; 15:842-866. [PMID: 34825341 DOI: 10.1007/s11684-021-0865-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 04/25/2021] [Indexed: 10/19/2022]
Abstract
Among various genera of free-living amoebae prevalent in nature, some members are identified as causative agents of human encephalitis, in which Naegleria fowleri followed by Acanthamoeba spp. and Balamuthia mandrillaris have been successively discovered. As the three dominant genera responsible for infections, Acanthamoeba and Balamuthia work as opportunistic pathogens of granulomatous amoebic encephalitis in immunocompetent and immunocompromised individuals, whereas Naegleria induces primary amoebic meningoencephalitis mostly in healthy children and young adults as a more violent and deadly disease. Due to the lack of typical symptoms and laboratory findings, all these amoebic encephalitic diseases are difficult to diagnose. Considering that subsequent therapies are also affected, all these brain infections cause significant mortality worldwide, with more than 90% of the cases being fatal. Along with global warming and population explosion, expanding areas of human and amoebae activity in some regions lead to increased contact, resulting in more serious infections and drawing increased public attention. In this review, we summarize the present information of these pathogenic free-living amoebae, including their phylogeny, classification, biology, and ecology. The mechanisms of pathogenesis, immunology, pathophysiology, clinical manifestations, epidemiology, diagnosis, and therapies are also discussed.
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Sarink MJ, van der Meijs NL, Denzer K, Koenderman L, Tielens AGM, van Hellemond JJ. Three encephalitis-causing amoebae and their distinct interactions with the host. Trends Parasitol 2021; 38:230-245. [PMID: 34758928 DOI: 10.1016/j.pt.2021.10.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 10/11/2021] [Accepted: 10/18/2021] [Indexed: 01/21/2023]
Abstract
Naegleria fowleri, Balamuthia mandrillaris, and Acanthamoeba spp. can cause devastating brain infections in humans which almost always result in death. The symptoms of the three infections overlap, but brain inflammation and the course of the disease differ, depending on the amoeba that is responsible. Understanding the differences between these amoebae can result in the development of strategies to prevent and treat these infections. Recently, numerous scientific advancements have been made in the understanding of pathogenicity mechanisms in general, and the basic biology, epidemiology, and the human immune response towards these amoebae in particular. In this review, we combine this knowledge and aim to identify which factors can explain the differences between the lethal brain infections caused by N. fowleri, B. mandrillaris, and Acanthamoeba spp.
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Affiliation(s)
- Maarten J Sarink
- Erasmus MC, University Medical Center Rotterdam, Department of Medical Microbiology and Infectious Diseases, Rotterdam, The Netherlands
| | - Nadia L van der Meijs
- Erasmus MC, University Medical Center Rotterdam, Department of Medical Microbiology and Infectious Diseases, Rotterdam, The Netherlands
| | - Kristin Denzer
- Center for Translational Immunology (CTI), University Medical Center Utrecht, Utrecht, The Netherlands
| | - Leo Koenderman
- Center for Translational Immunology (CTI), University Medical Center Utrecht, Utrecht, The Netherlands; Department of Respiratory Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Aloysius G M Tielens
- Erasmus MC, University Medical Center Rotterdam, Department of Medical Microbiology and Infectious Diseases, Rotterdam, The Netherlands
| | - Jaap J van Hellemond
- Erasmus MC, University Medical Center Rotterdam, Department of Medical Microbiology and Infectious Diseases, Rotterdam, The Netherlands.
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Niederkorn JY. The biology of Acanthamoeba keratitis. Exp Eye Res 2020; 202:108365. [PMID: 33221372 DOI: 10.1016/j.exer.2020.108365] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/10/2020] [Accepted: 11/13/2020] [Indexed: 12/31/2022]
Abstract
Acanthamoeba keratitis (AK) is a rare protozoal infection of the cornea. At least eight species of Acanthamoeba are known to cause this sight-threatening disease of the ocular surface. Acanthamoeba spp. exist in a wide array of niches ranging from thermal springs to under ice and every conceivable habitat in between. Contact lens wear is the leading risk factor for AK and is practiced by over 30 million individuals in the United States, yet the incidence of AK is less than 33 cases per one million contact lens wearers. Serological studies have reported that 90%-100% of individuals with no history of AK possess antibodies specific for Acanthamoeba antigens indicating that exposure to this organism is commonplace, yet disease is remarkably rare. Animal studies have shed light on the pathobiology and immunobiology of AK and indicate that a constellation of factors including the ocular surface microbiome and the microbiome of Acanthamoeba itself contribute to the pathogenesis of AK. Interesting, secretory antibodies produced by the adaptive immune response can prevent the initiation of corneal infection, but once Acanthamoeba trophozoites breach the corneal epithelium the adaptive immune system is helpless in altering the course of AK. It has been almost 50 years since AK was first described, yet many questions remain unanswered about this curious and enigmatic disease of the ocular surface.
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Affiliation(s)
- Jerry Y Niederkorn
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA.
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6
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Mohammed I, Said DG, Dua HS. Human antimicrobial peptides in ocular surface defense. Prog Retin Eye Res 2017; 61:1-22. [DOI: 10.1016/j.preteyeres.2017.03.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/22/2017] [Accepted: 03/27/2017] [Indexed: 01/17/2023]
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Wojtkowiak-Giera A, Derda M, Kolasa-Wołosiuk A, Hadaś E, Kosik-Bogacka D, Solarczyk P, Jagodziński PP, Wandurska-Nowak E. Toll-like receptors in the brain of mice following infection with Acanthamoeba spp. Parasitol Res 2016; 115:4335-4344. [PMID: 27511368 PMCID: PMC5056946 DOI: 10.1007/s00436-016-5217-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 07/28/2016] [Indexed: 12/02/2022]
Abstract
The Toll-like receptors (TLRs) of the innate immune system play an important role in the recognition of pathogens such as bacteria, viruses, fungi, and parasites. In this study, we examined the changes in the level of expression of TLR2 and TLR4 mRNA and protein in the brains of mice infected with Acanthamoeba spp. The Acanthamoeba strains were isolated from a patient with Acanthamoeba keratitis (AK) (Ac55) and Malta Lake (Ac43). In the brain isolated from mice at 2 days post-infection (dpi) with Acanthamoeba strains Ac55 and Ac43, mRNAs for TLR2 and TLR4 were significantly more strongly expressed in comparison with the uninfected mice. In Acanthamoeba-infected mice, TLR2 and TLR4 expression was detected in neurons, glial cells, and endothelial cells within the neocortex. These receptors showed more intense expression in ependymocytes of the choroid plexus of infected mice at 2 dpi. Increased levels of TLR2 and TLR4 mRNA expression in infected mice suggest the involvement of these TLRs in the recognition of Acanthamoeba spp. pathogen-associated molecular patterns (PAMPs).
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Affiliation(s)
- Agnieszka Wojtkowiak-Giera
- Department of Biology and Medical Parasitology, Poznan University of Medical Sciences, 10 Fredry Street, 61-701, Poznan, Poland
| | - Monika Derda
- Department of Biology and Medical Parasitology, Poznan University of Medical Sciences, 10 Fredry Street, 61-701, Poznan, Poland.
| | - Agnieszka Kolasa-Wołosiuk
- Department of Histology and Embryology, Pomeranian Medical University, 71 Powstancow Wielkopolskich Street, 70-111, Szczecin, Poland
| | - Edward Hadaś
- Department of Biology and Medical Parasitology, Poznan University of Medical Sciences, 10 Fredry Street, 61-701, Poznan, Poland
| | - Danuta Kosik-Bogacka
- Department of Biology and Medical Parasitology, Pomeranian Medical University, 72 Powstancow Wielkopolskich Street, 70-111, Szczecin, Poland
| | - Piotr Solarczyk
- Department of Biology and Medical Parasitology, Poznan University of Medical Sciences, 10 Fredry Street, 61-701, Poznan, Poland
| | - Paweł P Jagodziński
- Department of Biochemistry and Molecular Biology, Poznan University of Medical Sciences, 6 Swiecickiego Street, 60-781, Poznań, Poland
| | - Elżbieta Wandurska-Nowak
- Department of Biology and Medical Parasitology, Poznan University of Medical Sciences, 10 Fredry Street, 61-701, Poznan, Poland
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Taube MA, del Mar Cendra M, Elsahn A, Christodoulides M, Hossain P. Pattern recognition receptors in microbial keratitis. Eye (Lond) 2015; 29:1399-415. [PMID: 26160532 DOI: 10.1038/eye.2015.118] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 05/31/2015] [Indexed: 12/12/2022] Open
Abstract
Microbial keratitis is a significant cause of global visual impairment and blindness. Corneal infection can be caused by a wide variety of pathogens, each of which exhibits a range of mechanisms by which the immune system is activated. The complexity of the immune response to corneal infection is only now beginning to be elucidated. Crucial to the cornea's defences are the pattern-recognition receptors: Toll-like and Nod-like receptors and the subsequent activation of inflammatory pathways. These inflammatory pathways include the inflammasome and can lead to significant tissue destruction and corneal damage, with the potential for resultant blindness. Understanding the immune mechanisms behind this tissue destruction may enable improved identification of therapeutic targets to aid development of more specific therapies for reducing corneal damage in infectious keratitis. This review summarises current knowledge of pattern-recognition receptors and their downstream pathways in response to the major keratitis-causing organisms and alludes to potential therapeutic approaches that could alleviate corneal blindness.
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Affiliation(s)
- M-A Taube
- Division of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK.,University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - M del Mar Cendra
- Division of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - A Elsahn
- Division of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK.,University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - M Christodoulides
- Division of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - P Hossain
- Division of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK.,University Hospital Southampton NHS Foundation Trust, Southampton, UK
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Pathogenic strains of Acanthamoeba are recognized by TLR4 and initiated inflammatory responses in the cornea. PLoS One 2014; 9:e92375. [PMID: 24633052 PMCID: PMC3954866 DOI: 10.1371/journal.pone.0092375] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 02/21/2014] [Indexed: 12/18/2022] Open
Abstract
Free-living amoebae of the Acanthamoeba species are the causative agent of Acanthamoeba keratitis (AK), a sight-threatening corneal infection that causes severe pain and a characteristic ring-shaped corneal infiltrate. Innate immune responses play an important role in resistance against AK. The aim of this study is to determine if Toll-like receptors (TLRs) on corneal epithelial cells are activated by Acanthamoeba, leading to initiation of inflammatory responses in the cornea. Human corneal epithelial (HCE) cells constitutively expressed TLR1, TLR2, TLR3, TLR4, and TLR9 mRNA, and A. castellanii upregulated TLR4 transcription. Expression of TLR1, TLR2, TLR3, and TLR9 was unchanged when HCE cells were exposed to A. castellanii. IL-8 mRNA expression was upregulated in HCE cells exposed to A. castellanii. A. castellanii and lipopolysaccharide (LPS) induced significant IL-8 production by HCE cells as measured by ELISA. The percentage of total cells positive for TLR4 was higher in A. castellanii stimulated HCE cells compared to unstimulated HCE cells. A. castellanii induced upregulation of IL-8 in TLR4 expressing human embryonic kidney (HEK)-293 cells, but not TLR3 expressing HEK-293 cells. TLR4 neutralizing antibody inhibited A. castellanii-induced IL-8 by HCE and HEK-293 cells. Clinical strains but not soil strains of Acanthamoeba activated TLR4 expression in Chinese hamster corneas in vivo and in vitro. Clinical isolates but not soil isolates of Acanthamoeba induced significant (P< 0.05) CXCL2 production in Chinese hamster corneas 3 and 7 days after infection, which coincided with increased inflammatory cells in the corneas. Results suggest that pathogenic species of Acanthamoeba activate TLR4 and induce production of CXCL2 in the Chinese hamster model of AK. TLR4 may be a potential target in the development of novel treatment strategies in Acanthamoeba and other microbial infections that activate TLR4 in corneal cells.
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Siddiqui R, Khan NA. Biology and pathogenesis of Acanthamoeba. Parasit Vectors 2012; 5:6. [PMID: 22229971 PMCID: PMC3284432 DOI: 10.1186/1756-3305-5-6] [Citation(s) in RCA: 359] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 01/10/2012] [Indexed: 12/18/2022] Open
Abstract
Acanthamoeba is a free-living protist pathogen, capable of causing a blinding keratitis and fatal granulomatous encephalitis. The factors that contribute to Acanthamoeba infections include parasite biology, genetic diversity, environmental spread and host susceptibility, and are highlighted together with potential therapeutic and preventative measures. The use of Acanthamoeba in the study of cellular differentiation mechanisms, motility and phagocytosis, bacterial pathogenesis and evolutionary processes makes it an attractive model organism. There is a significant emphasis on Acanthamoeba as a Trojan horse of other microbes including viral, bacterial, protists and yeast pathogens.
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Acanthamoeba produces disseminated infection in locusts and traverses the locust blood-brain barrier to invade the central nervous system. BMC Microbiol 2010; 10:186. [PMID: 20615207 PMCID: PMC2908093 DOI: 10.1186/1471-2180-10-186] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 07/08/2010] [Indexed: 11/22/2022] Open
Abstract
Background Many aspects of Acanthamoeba granulomatous encephalitis remain poorly understood, including host susceptibility and chronic colonization which represent important features of the spectrum of host-pathogen interactions. Previous studies have suggested locusts as a tractable model in which to study Acanthamoeba pathogenesis. Here we determined the mode of parasite invasion of the central nervous system (CNS). Results Using Acanthamoeba isolates belonging to the T1 and T4 genotypes, the findings revealed that amoebae induced sickness behaviour in locusts, as evidenced by reduced faecal output and weight loss and, eventually, leading to 100% mortality. Significant degenerative changes of various tissues were observed by histological sectioning. Both isolates produced disseminated infection, with viable amoebae being recovered from various tissues. Histological examination of the CNS showed that Acanthamoeba invaded the locust CNS, and this is associated with disruption of the perineurium cell/glial cell complex, which constitutes the locust blood-brain barrier. Conclusions This is the first study to demonstrate that Acanthamoeba invades locust brain by modulating the integrity of the insect's blood-brain barrier, a finding that is consistent with the human infection. These observations support the idea that locusts provide a tractable model to study Acanthamoeba encephalitis in vivo. In this way the locust model may generate potentially useful leads that can be tested subsequently in mammalian systems, thus replacing the use of vertebrates at an early stage, and reducing the numbers of mammals required overall.
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Alizadeh H, Neelam S, Niederkorn JY. Role of activated macrophages in Acanthamoeba keratitis. J Parasitol 2008; 93:1114-20. [PMID: 18163346 DOI: 10.1645/ge-1083r.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The purpose of this study was to determine whether activating the conjunctival macrophages would affect the course of Acanthamoeba spp. keratitis in a Chinese hamster model of this disease. Chinese hamster spleen cells were stimulated with concanavalin A (Con A), and interferon gamma (IFN-gamma) -containing supernatants were collected 24 hr later. The IFN-gamma-containing supernatants were loaded into liposomes, which were fed to peritoneal macrophages in vitro. Macrophage activation was assessed by testing for production of nitric oxide (NO) with the use of Griess reagent. Conjunctival macrophages were activated in situ by subconjunctival injection of liposomes containing Con A-activated spleen cell culture supernatants. Control liposomes were loaded with phosphate-buffered saline (PBS). Macrophages exposed to supernatants from Con A-stimulated spleen cells produced 4-fold-higher amounts of NO than unstimulated macrophages. Activation of macrophages via subconjunctival injection of liposomes containing supernatants from Con A-stimulated spleen cell cultures resulted in rapid resolution of the corneal infection. Approximately 80% of animals treated with PBS-containing liposomes demonstrated evidence of corneal disease at day 14 compared to 10% incidence of infection in the Con A-treated group. Moreover, at all time points examined, the clinical appearance of the keratitis in animals treated with liposomes containing Con A supernatant was significantly reduced compared to the group treated with liposomes containing PBS (P < 0.05). Macrophages stimulated with IFN-gamma-containing supernatants killed significant numbers of the trophozoites in vitro (P < 0.05). Killing was inhibited by cytochalasin D, but not by L-N6-1-iminoethyl-L-lysine dihydrochloride (L-NIL), which is a selective inhibitor of inducible NO synthase (INOS).
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Affiliation(s)
- Hassan Alizadeh
- Department of Ophthalmology and Microbiology, University of Texas Southwestern Medical Center, Dallas 75390-9057, USA.
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Li L, Sun X. Impaired innate immunity of ocular surface is the key bridge between extended contact lens wearing and occurrence of Acanthamoeba keratitis. Med Hypotheses 2007; 70:260-4. [PMID: 17689022 DOI: 10.1016/j.mehy.2007.05.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 05/13/2007] [Indexed: 11/28/2022]
Abstract
Acanthamoeba keratitis is a progressive, sight-threatening corneal disease. Extended wearing contact lens is one of predisposed factors. Early studies mostly focused on "improper contact-lens hygiene", which described that contact lens wearers have more opportunities to contact with pathogens directly and prone to get A. keratitis. However, improper contact-lens hygiene can not explain the phenomenon that Acanthamoeba protozoon were found in normal individuals' lens-cases. So there might be other factors related with A. keratitis. Recently, more attention has been paid on the influence of extended wearing contact lens on the innate immunity of ocular surface. It has been proven that in contact lens wearers the reactivity of polymorphonuclear leucocytes (PMNs) and the concentration of certain inflammatory mediators were significantly altered compared with that in non-lens wearers. Moreover, other studies showed the important contributions of innate immunity on occurrence and development of A. keratitis. With the contribution of extended wearing contact lens on immunity and the relation between innate immunity and Acanthamoeba, we suggest that the impaired innate immunity of ocular surface may be a key bridge between extended wearing contact lens and A. keratitis. With the impaired innate immunity caused by extended contact-lens wearing, the Acanthamoeba trophozoites and cysts could not be easily killed, therefore A. keratitis was occurred and aggravated. Understanding the immunological mechanism of extended contact lens wearing on the A. keratitis may give more contributions on the research of the disease, and facilitate the production of contact lens with much higher biocompatibility.
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Affiliation(s)
- Li Li
- Beijing Institute of Ophthalmology, Beijing TongRen Ophthalmic Center, Capital University of Medical Sciences, 17 Hou Gou Lane, Chong Nei Street, Beijing 100005, PR China
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Abstract
Acanthamoeba is an opportunistic protozoan that is widely distributed in the environment and is well recognized to produce serious human infections, including a blinding keratitis and a fatal encephalitis. This review presents our current understanding of the burden of Acanthamoeba infections on human health, their pathogenesis and pathophysiology, and molecular mechanisms associated with the disease, as well as virulence traits of Acanthamoeba that may be targets for therapeutic interventions and/or the development of preventative measures.
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Affiliation(s)
- Naveed Ahmed Khan
- School of Biological and Chemical Sciences, Birkbeck College, University of London, London, UK.
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Clarke DW, Niederkorn JY. The immunobiology of Acanthamoeba keratitis. Microbes Infect 2006; 8:1400-5. [PMID: 16697233 DOI: 10.1016/j.micinf.2005.12.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Revised: 11/30/2005] [Accepted: 12/14/2005] [Indexed: 11/28/2022]
Abstract
Acanthamoeba spp. are free-living amoebae that cause Acanthamoeba keratitis, a blinding corneal infection. The innate immune apparatus is crucial for the resolution of the disease. With the exception of mucosal antibody, elements of the adaptive immune system fail to prevent infection or contribute to its resolution in experimental animals.
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Affiliation(s)
- Daniel W Clarke
- Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9057, USA
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Pugine SMP, Faria MFD, Maia AAM, Valle CRD, Boschini C, Poleti MD, Silva MRMD, De Melo MP. Effect of Cysticercus cellulosae fractions on the respiratory burst of pig neutrophils. Rev Inst Med Trop Sao Paulo 2005; 47:91-4. [PMID: 15880220 DOI: 10.1590/s0036-46652005000200006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neutrophils, eosinophils and macrophages are cells that interact with invading parasites and naive hosts have been shown to have anti-parasitic activity. The initial reaction of these leukocytes is the generation of reactive oxygen species (ROS) to play in parasite expulsion. The present work was carried out to study the effect of total extract, scolex and membrane fractions from Cysticercus cellulosae on respiratory burst by pig neutrophils. Hydrogen peroxide (H2O2) production by neutrophils incubated with metacestode fractions from C. cellulosae showed an increase of: 190% (total extract), 120% (scolex) and 44% (membrane). High antioxidant catalatic activity (33%, 28%, 28% by total extract, scolex and membrane, respectively) was observed in neutrophils incubated with metacestode fractions, which could be an attempt at self-protection. Scolex and membrane fractions increased the phagocytic capacity of neutrophils (44% and 28%, respectively). On the other hand, total cysticerci did not alter the phagocytosis, possibly due to modifications in membrane function, caused by high ROS production from neutrophils in the presence of total cysticerci. Total fraction from C. cellulosae is toxic for neutrophils as shown by the decrease in phagocytic capacity, probably caused by high levels of ROS formation. The difference in toxicity of total extract, scolex and membrane fractions on neutrophils can be explained by the presence of an antigenic effect of the vesicular fluid in the total extract of C. cellulosae.
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Affiliation(s)
- Silvana Marina Piccoli Pugine
- Department of Basic Science, Faculty of Zootechny and Food Engineering, University of São Paulo, Pirassununga, Brazil
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Said NA, Shoeir AT, Panjwani N, Garate M, Cao Z. Local and systemic humoral immune response during acute and chronic Acanthamoeba keratitis in rabbits. Curr Eye Res 2005; 29:429-39. [PMID: 15764087 DOI: 10.1080/02713680490522470] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE To study local and systemic antibody responses during the course of acute and chronic Acanthamoeba keratitis in a rabbit model. The role of secretory IgA (sIgA) in innate and adaptive immunity is investigated. METHODS Acanthamoeba keratitis was induced by intrastromal injection of live trophozoites in rabbits with and without prior oral immunization with aqueous Acanthamoeba antigen. The severity score of the ensuing keratitis was followed. Anti-Acanthamoeba antibodies in tears and sera were determined before infection and on a weekly basis postinfection for 6 weeks. The role of mucosal IgA as a link between the innate and adaptive immunity to Acanthamoeba was evaluated. RESULTS Acanthamoeba keratitis was significantly milder in animals infected after oral immunization than in naïve animals. Mucosal sIgA bound Acanthamoeba in a concentration-dependent, mannose-mediated manner. It significantly inhibited Acanthamoeba binding to rabbit corneal epithelium in vitro and in vivo. Anti-Acanthamoeba IgA significantly influenced amoebic lysis by neutrophils. CONCLUSIONS Mucosal IgA protects the external ocular surface by virtue of anti-adhesin properties displayed by the mannosylated residues on the heavy chains of IgA molecule (innate immunity) as well as specific antigen-binding sites (adaptive immunity). Immune IgA also augmented neutrophil-mediated amoebic lysis (adaptive immunity).
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Affiliation(s)
- Neveen A Said
- Parasitology Department, Research Institute of Ophthalmology, Giza, Egypt.
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Abstract
Acanthamoeba spp. are free-living amebae that inhabit a variety of air, soil, and water environments. However, these amebae can also act as opportunistic as well as nonopportunistic pathogens. They are the causative agents of granulomatous amebic encephalitis and amebic keratitis and have been associated with cutaneous lesions and sinusitis. Immuno compromised individuals, including AIDS patients, are particularly susceptible to infections with Acanthamoeba. The immune defense mechanisms that operate against Acanthamoeba have not been well characterized, but it has been proposed that both innate and acquired immunity play a role. The ameba's life cycle includes an active feeding trophozoite stage and a dormant cyst stage. Trophozoites feed on bacteria, yeast, and algae. However, both trophozoites and cysts can retain viable bacteria and may serve as reservoirs for bacteria with human pathogenic potential. Diagnosis of infection includes direct microscopy of wet mounts of cerebrospinal fluid or stained smears of cerebrospinal fluid sediment, light or electron microscopy of tissues, in vitro cultivation of Acanthamoeba, and histological assessment of frozen or paraffin-embedded sections of brain or cutaneous lesion biopsy material. Immunocytochemistry, chemifluorescent dye staining, PCR, and analysis of DNA sequence variation also have been employed for laboratory diagnosis. Treatment of Acanthamoeba infections has met with mixed results. However, chlorhexidine gluconate, alone or in combination with propamidene isethionate, is effective in some patients. Furthermore, effective treatment is complicated since patients may present with underlying disease and Acanthamoeba infection may not be recognized. Since an increase in the number of cases of Acanthamoeba infections has occurred worldwide, these protozoa have become increasingly important as agents of human disease.
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Affiliation(s)
- Francine Marciano-Cabral
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia 23298-0678, USA.
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Hurt M, Apte S, Leher H, Howard K, Niederkorn J, Alizadeh H. Exacerbation of Acanthamoeba keratitis in animals treated with anti-macrophage inflammatory protein 2 or antineutrophil antibodies. Infect Immun 2001; 69:2988-95. [PMID: 11292716 PMCID: PMC98252 DOI: 10.1128/iai.69.5.2988-2995.2001] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neutrophils are thought to be involved in many infectious diseases and have been found in high numbers in the corneas of patients with Acanthamoeba keratitis. Using a Chinese hamster model of keratitis, conjunctival neutrophil migration was manipulated to determine the importance of neutrophils in this disease. Inhibition of neutrophil recruitment was achieved by subconjunctival injection with an antibody against macrophage inflammatory protein 2 (MIP-2), a powerful chemotactic factor for neutrophils which is secreted by the cornea. In other experiments, neutrophils were depleted by intraperitoneal injection of anti-Chinese hamster neutrophil antibody. The inhibition of neutrophils to the cornea resulted in an earlier onset and more severe infection compared to controls. Anti-MIP-2 antibody treatment produced an almost 35% reduction of myeloperoxidase activity in the cornea 6 days postinfection, while levels of endogenous MIP-2 secretion increased significantly. Recruitment of neutrophils into the cornea via intrastromal injections of recombinant MIP-2 generated an initially intense inflammation that resulted in the rapid resolution of the corneal infection. The profound exacerbation of Acanthamoeba keratitis seen when neutrophil migration was inhibited, combined with the rapid clearing of the disease in the presence of increased neutrophils, strongly suggests that neutrophils play an important role in combating Acanthamoeba infections in the cornea.
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Affiliation(s)
- M Hurt
- Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA
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El-Ghaysh A, Turner RJ, Brophy PM, Barrett J. Effect of Fasciola gigantica somatic extracts and excretory/secretory products on superoxide production by activated neutrophils. Vet Parasitol 1999; 84:91-100. [PMID: 10435794 DOI: 10.1016/s0304-4017(99)00089-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Somatic extracts and excretory/secretory (ES) products from Fasciola gigantica suppress the release of toxic oxygen intermediates by activated sheep neutrophils. At the concentrations used both the somatic extracts and ES products had no effect on neutrophil viability and in both cases the inhibitory effect was reversible. In the somatic extracts, heating or treatment with trypsin destroyed the inhibitory effect. However, the ES products contained at least two immunomodulatory factors. One was less than 10 kDa, the other greater than 50 kDa and both factors were heat and trypsin stable. By acting locally and only causing temporary inhibition of neutrophil function F. gigantica can protect itself from immune mediated oxidative damage without compromising the host's response elsewhere.
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Affiliation(s)
- A El-Ghaysh
- Parasitology Department, Faculty of Veterinary Medicine, Cairo University, Egypt
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Abstract
Acanthamoeba species are an important cause of microbial keratitis that may cause severe ocular inflammation and visual loss. The first cases were recognized in 1973, but the disease remained very rare until the 1980s, when an increase in incidence mainly associated with contact lens wear was reported. There is an increased risk when contact lens rinsing and soaking solutions are prepared with nonsterile water and salt tablets. The clinical picture is often characterized by severe pain with an early superficial keratitis that is often treated as herpes simplex infection. Subsequently a characteristic radial perineural infiltration may be seen, and ring infiltration is common. Limbitis and scleritis are frequent. Laboratory diagnosis is primarily by culture of epithelial samples inoculated onto agar plates spread with bacteria. Direct microscopy of samples using stains for the cyst wall or immunostaining may also be employed. A variety of topically applied therapeutic agents are thought to be effective, including propamidine isethionate, clotrimazole, polyhexamethylene biguanide, and chlorhexidine. Various combinations of these and other agents have been employed, often resulting in medical cure, especially if treatment is commenced early in the course of the disease. Penetrating keratoplasty is preferably avoided in inflamed eyes, but may be necessary in severe cases to preserve the globe or, when the infection has resolved, to restore corneal clarity for optical reasons.
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