Abstract
Amoebae of the genus Acanthamoeba are etiological agents of granulomatous amoebic encephalitis (GAE). Recently, through an in vivo GAE model, Acanthamoeba trophozoites were immunolocalized in contact with the peripheral nervous system (PNS) cells—Schwann cells (SC). In this study, we analyzed in greater detail the in vitro early morphological events (1, 2, 3, and 4 h) during the interaction of A. culbertsoni trophozoites (ATCC 30171) with SC from Rattus norvegicus (ATCC CRL-2941). Samples were processed for scanning and transmission electron microscopy as well as confocal microscopy. After 1 h of interaction, amoebae were observed to be adhered to the SC cultures, emitting sucker-like structures associated with micro-phagocytic channels. In addition, evidence of necrosis was identified since edematous organelles as well as multivesicular and multilamellar bodies characteristics of autophagy were detected. At 2 h, trophozoites migrated beneath the SC culture in which necrosis and autophagy persisted. By 3 and 4 h, extensive lytic zones were observed. SC necrosis was confirmed by confocal microscopy. We reported for the first time the induction of autophagic and necrotic processes in PNS cells, associated in part with the contact-dependent pathogenic mechanisms of A. culbertsoni trophozoites.
Highlights
Free-living amoebae (FLA) of the genus Acanthamoeba are cosmopolitan protozoans commonly found in natural environments, they play a significant ecological role in controlling bacterial populations.Pathogens 2020, 9, 458; doi:10.3390/pathogens9060458 www.mdpi.com/journal/pathogensSome species of this genus, in addition to being ecologically relevant, are important in the medical field, due to their ability to exist as free-living organisms and as parasites, becoming a threat to the health and life of the hosts [1,2]
Several authors have carried out studies to describe the pathogenic mechanisms of these protozoa in different tissues and cell lines, such as Madin–Darby Canine Kidney cells (MDCK) cells [11], corneal tissue [10], neuroblastoma cells [12,13], microglial cells [15,16,17], and brain microvascular endothelial cells [6,18]; until now, no reports about the invasion mechanisms that these amoebae carry out in peripheral nervous system (PNS) cells, in Schwann cells (SC), have been published
The strain in study, A. culbertsoni (ATCC® 30171TM), was the first FLA to be reported as a pathogenic amoeba for mammals [23]; for that reason we considered it important to reactivate its virulence in order to maintain the strain in optimal conditions
Summary
Free-living amoebae (FLA) of the genus Acanthamoeba are cosmopolitan protozoans commonly found in natural environments, they play a significant ecological role in controlling bacterial populations.Pathogens 2020, 9, 458; doi:10.3390/pathogens9060458 www.mdpi.com/journal/pathogensSome species of this genus, in addition to being ecologically relevant, are important in the medical field, due to their ability to exist as free-living organisms and as parasites, becoming a threat to the health and life of the hosts [1,2]. Free-living amoebae (FLA) of the genus Acanthamoeba are cosmopolitan protozoans commonly found in natural environments, they play a significant ecological role in controlling bacterial populations. Some species of this genus, in addition to being ecologically relevant, are important in the medical field, due to their ability to exist as free-living organisms and as parasites, becoming a threat to the health and life of the hosts [1,2]. Acanthamoeba are etiological agents of Acanthamoeba keratitis (AK), a painful, vision–threatening infection occurring primarily in immunocompetent persons and contact lens users [3]. In the central nervous system (CNS), they are etiological agents of granulomatous amoebic encephalitis (GAE), which mostly occurs in people with metabolic, physiological, and immunological disorders, reporting greater than 90% mortality. GAE infection is characterized by a chronic protracted slowly progressive CNS, which may involve the lungs and skin [2,4].
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