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Query: UMLS:C0022568 (keratitis)
 5,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acanthamoeba spp. are ubiquitous free-living protozoa found in a wide range of environmental niches. They are resistant to disinfectants, temperature variation and desiccation and are responsible for two recognised diseases in humans, granulomatous amoebic encephalitis and keratitis. Both infections are rare, although the latter is currently receiving more attention following the association between Acanthamoeba and the wearing of contact lenses. Laboratory diagnosis is unusual but not beyond the bounds of most routine clinical microbiology departments. In this review the various aspects surrounding the ecology, pathogenicity and laboratory detection of Acanthamoeba spp. are considered.
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PMID:Acanthamoeba: ecology, pathogenicity and laboratory detection. 875 92

Corneal infection with herpes simplex virus-1 in immunocompetent mice induces an immunopathologic response termed herpetic stromal keratitis (HSK). The earliest sign of disease is neutrophil infiltration, which lasts for 48 to 72 h and then disappears. However, a secondary neutrophil infiltration, this time more massive, occurs, beginning 8 to 9 days postinfection, a time in which HSK becomes clinically evident. The role of neutrophils in HSK expression was investigated by eliminating such cells using a specific mAb (RB6-8C5). In neutrophil-depleted immunocompetent mice, virus replicated more abundantly, but no effects on HSK expression were observed, possibly because sustained neutropenia could not be maintained. However, using a severe combined immunodeficient mouse model, in which HSK does not occur unless given adoptive transfer of CD4+ T cells, the effects of neutrophil depletion were more pronounced. There were significantly less incidence and severity of HSK in CD4+ T cell-reconstituted severe combined immunodeficient mice that were depleted of neutrophils as compared with controls. Neutrophil-depleted mice displayed moderate to severe periocular skin lesions, progressively became cachetic, and developed signs of encephalitis. Virus was recovered at higher titers and for longer periods from eyes of neutrophil-depleted animals. Brain virus titers were also significantly higher on day 12 postinfection as compared with control animals. These results suggest that herpes simplex virus infection of the cornea rapidly invokes recruitment of neutrophils that may aid in viral clearance, and that neutrophils directly or indirectly serve as agonists in perpetuating a CD4+ T cell-mediated inflammatory reaction.
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PMID:On the essential involvement of neutrophils in the immunopathologic disease: herpetic stromal keratitis. 901 83

Burkholderia pickettii is a facultative pathogen that has been isolated from patient sources and environmental sources including respiratory therapy solutions, deionized water and aqueous disinfectants. The organism has been associated with septicemia and respiratory tract infections. In our investigation, Burkholderia pickettii (biovar 2) was for the first time isolated from Acanthamoeba sp. (group II), a free living amoeba species recovered from the wet area of a physiotherapy unit. Pathogenic strains of acanthamoebae may cause amoebic-encephalitis (AE) and keratitis. Light and electron microscopic examinations showed that in a first step, the bacterial were phagocytized by the amoebae. In contrast to Enterobacter cloacae and Escherichia coli that were used as food organisms and digested within food vacuoles, Burkholderia pickettii caused the amoebae to develop large vacuoles filled with completely intact and motile bacteria. 3-5 days after infection, Pseudomonas pickettii had multiplied within the enlarging parasitophorous vacuoles. Ultrastructural changes in the host cells occurred and the amoebae finally underwent rupture or lysis. In cocultivation assays we could not only reinfect the original host amoeba but Acanthamoeba strains from other habitats could successfully be infected with Burkholderia pickettii as well.
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PMID:Isolation of an Acanthamoeba strain with intracellular Burkholderia pickettii infection. 914 16

Replication-defective mutants of herpes simplex virus 1 (HSV-1) elicit immune responses in mice that reduce acute and latent infection after corneal challenge and are protective against development of disease. To understand the basis for the protective immunity induced by this new form of immunization, we investigated the contribution of various components of the immune response to protection against corneal infection and disease. Passive transfer of sera from mice immunized with the replication-defective mutant virus, d301, its parental HSV-1 strain, or uninfected cell lysate was used to examine the role of antibody. Despite posttransfer neutralizing antibody titers equivalent to those in control mice directly immunized with mutant virus, recipients of immune serum showed no reductions in primary replication in the eye, keratitis, or latent infection of the nervous system. However, immune serum protected mice from encephalitis and death. To examine the contribution of T cell subsets to protection, mice were immunized once with mutant virus and then were depleted in vivo of CD4+ or CD8+ T cells prior to corneal challenge. CD4 depletion resulted in higher titers of challenge virus in the eye at 3 to 4 days after challenge compared to control mice. Latent infection of the nervous system was increased by depletion of CD4+ T cells but not by depletion of CD8+ T cells keratitis developed only in a portion of the CD8+ T cell-depleted mice, suggesting that an immunopathologic potential of CD4+ T cells is held in check when immune CD8+ T cells are also present. Taken together, these data support a role for antibody induced by immunization with a replication-defective virus principally in protecting the central nervous system from disease, roles for CD4+ T cells in reducing primary replication in the eye and protecting against latent infection of the nervous system, and a role for CD8+ T cells in regulating the immunopathologic activity of CD4+ T cells.
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PMID:Contributions of antibody and T cell subsets to protection elicited by immunization with a replication-defective mutant of herpes simplex virus type 1. 943 23

Naegleria fowleri, Acanthamoeba spp. and Balamuthia mandrillaris are free-living amoebae that occasionally may induce pathology in human beings. CNS disease due to N. fowleri, called "primary" amoebic meningoencephalitis, is acquired after exposure to polluted waters in swimming pools, rivers, and lakes. The clinical course is acute, often fulminant and characterized pathologically by necrotizing hemorrhagic meningoencephalitis, involving mainly the base of the brain, brainstem and cerebellum. In contrast, some Acanthamoeba spp. and B. mandrillaris cause opportunistic, chronic "granulomatous" encephalitis in subjects pathologically or iatrogenically immunocompromised. There are, most likely, foci of protozoa in lung and skin reaching the CNS by hematogenous route. Only Acanthamoeba spp. can also produce severe, subacute keratitis, mainly today in contact lens wearers.
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PMID:[Human pathology caused by free-living amoebae]. 961 66

Acanthamoeba spp. are free-living amebae associated with amebic keratitis and chronic granulomatous amebic encephalitis. The present studies were undertaken to compare the pathogenicity of three species of Acanthamoeba in B6C3F1 mice after intranasal challenge with Acanthamoeba-induced cytopathogenicity for different macrophage populations. The ability of murine macrophage cell lines and activated murine peritoneal macrophages to lyse Acanthamoeba has been assessed by coincubating macrophages with 3H-uridine labeled amebae. Conversely, destruction of macrophages by Acanthamoeba was determined by measuring the release of chromium-51 from radiolabeled macrophages. Acanthamoeba culbertsoni, which is highly pathogenic for mice, destroys macrophage cultures in vitro. Activated primary peritoneal macrophages were more resistant to Acanthamoeba-mediated destruction than macrophage cell lines activated in vitro. Activated macrophages were capable of limited destruction of Acanthamoeba polyphaga and Acanthamoeba castellanii. Acanthamoeba-specific antibodies increased the amebicidal activity of activated macrophages. Macrophage-mediated destruction was by contact-dependent cytolysis and by ingestion of amebae. Conditioned medium obtained from macrophage cultures after treatment with lipopolysaccharide and interferon gamma was neither cytolytic nor cytostatic for Acanthamoeba spp. Purified recombinant cytokines including tumor necrosis factor alpha, interleukin 1 alpha, and interleukin 1 beta, alone or in combination, were not cytolytic for Acanthamoeba trophozoites.
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PMID:The interaction of Acanthamoeba spp. with activated macrophages and with macrophage cell lines. 970 82

The effect of 100 polar and 100 nonpolar plant extract materials obtained from Southeast Asia were evaluated for amebicidal activity in vitro against three species of Acanthamoeba. A. culbertsoni, A. castellanii, and A. polyphaga, the causative agents of granulomatous amebic encephalitis and amebic keratitis, were studied in vitro to determine whether the plant extracts exhibited amebicidal activity or induced encystment of the amebae. Of the 200 plant extracts tested, extracts obtained from three plants (Ipomoea sp., Kaempferia galanga, and Cananga odorata) were amebicidal for all three species of Acanthamoeba and a fourth extract prepared from Gastrochilus panduratum was lytic for A. polyphaga and growth-inhibitory for A. castellanii and A. culbertsoni. Three plant extracts induced encystment of all three species of Acanthamoeba. Select plant extracts were tested as well for tumoricidal activity against B103 neuroblastoma cells. Some plant extracts that exhibited tumoricidal activity for B103 cells were not amebicidal for Acanthamoeba spp. Additionally, the polar and nonpolar extracts that exhibited amebicidal activity were also tested for activity against primary murine peritoneal macrophage cultures. Plant extracts that demonstrated tumoricidal or amebicidal activity were not lytic for normal macrophage cultures.
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PMID:Amebicidal activity of plant extracts from Southeast Asia on Acanthamoeba spp. 976 4

Herpetic stromal keratitis (HSK) is a CD4+ T cell-controlled immunopathologic lesion in the eye that results from infection with herpes simplex virus (HSV). Target Ags involved in HSK remain undefined. In this study, we determined if HSK could be induced in animals genetically incapable of generating HSV Ag-specific CD4+ T cells. Mice bearing transgenic TCR specific to OVA peptide 323-339 (DO11.10) were crossed to SCID mice whose offspring (Tg-SCID) possessed CD4+ T cells, >98% of which expressed the OVA peptide-specific TCR. HSV infection of Tg-SCID mice was lethal, and mice failed to generate detectable T cell responses even after repeated immunization with a mutant avirulent virus (AN-1). Immunization with AN-1 virus followed by ocular challenge with HSV resulted in ocular inflammation before encephalitis, in contrast to the protection conferred in the control BALB/c and DO11.10 mice. These results indicate that clinical HSK may not require viral Ag recognition by CD4+ T cells and that T cells of irrelevant specificity can be recruited, activated, and driven into effector function in the HSV-infected cornea. This is suggested to represent a bystander activation effect resulting from the presence of proinflammatory mediators resulting from HSV replication.
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PMID:Virus-induced immunoinflammatory lesions in the absence of viral antigen recognition. 978 Feb 5

A one year round survey was conducted for isolation of free living amoebae (FLA) in the city of San Luis Potosi, (SLP), Mexico, which is placed in a desert environment. Samples were taken by modified impinger method and cultivated in laboratory conditions for FLA isolation following a week period of rehidration. 57 strains were isolated, 39% belonged to Acanthamoeba genus (which is important because it bears opportunistic pathogens that produce amoebic keratitis and granulomatous amoebic encephalitis in humans), 16% to Hartmannella, 9% to Vahlkampfia and the other proportion was divided among 6 other genera. The isolations were more abundant during dry season and the main genera were present in all four stands. The difference among them was the species variety which is discused as connected with abundance of organic wastes and lack of urbanization near the stations.
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PMID:Amoebological study of the atmosphere of San Luis Potosi, SLP, Mexico. 985 7

Free-living amoebae cause three well-defined disease entities: a rapidly fatal primary meningoencephalitis, a chronic granulomatous amoebic encephalitis (GAE), and a chronic amoebic keratitis. GAE occurs in immunocompromised persons. Recently, another type of free-living amoeba, Balamuthia mandrillaris, has been shown to cause GAE. The finding that this amoeba has caused infection in some healthy children has raised the possibility that humans may lack immunity to B. mandrillaris. Human serum was examined for the presence of surface antibodies specific for this amoeba by immunofluorescence. Sera from adults contained titers of 1/64-1/256 of anti-B. mandrillaris antibodies (IgM and IgG classes), which did not cross-react with other amoebae. Cord blood contained very low antibody levels, but levels similar to those in adults were seen in serum of 1- to 5-year-old children.
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PMID:Serum antibodies to Balamuthia mandrillaris, a free-living amoeba recently demonstrated to cause granulomatous amoebic encephalitis. 1019 Dec 43


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