The interaction between Acanthamoeba polyphaga and human osteoblastic cells in vitro

A history of over 40 years of potentially pathogenic free-living amoeba studies in Brazil - a systematic review

Free-living amoeba (FLA) group includes the potentially pathogenic genera Acanthamoeba, Naegleria, Balamuthia, Sappinia, and Vermamoeba, causative agents of human infections (encephalitis, keratitis, and disseminated diseases). In Brazil, the first report on pathogenic FLA was published in the 70s and showed meningoencephalitis caused by Naegleria spp. FLA studies are emerging, but no literature review is available to investigate this trend in Brazil critically. Thus, the present work aims to integrate and discuss these data. Scopus, PubMed, and Web of Science were searched, retrieving studies from 1974 to 2020. The screening process resulted in 178 papers, which were clustered into core and auxiliary classes and sorted into five categories: wet-bench studies, dry-bench studies, clinical reports, environmental identifications, and literature reviews. The papers dating from the last ten years account for 75% (134/178) of the total publications, indicating the FLA topic has gained Brazilian interest. Moreover, 81% (144/178) address Acanthamoeba-related matter, revealing this genus as the most prevalent in all categories. Brazil’s Southeast, South, and Midwest geographic regions accounted for 96% (171/178) of the publications studied in the present work. To the best of our knowledge, this review is the pioneer in summarising the FLA research history in Brazil.

Entamoeba gingivalis Exerts Severe Pathogenic Effects on the Oral Mucosa

The protozoan Entamoeba gingivalis colonizes the healthy oral mucosa with a prevalence of 15%. Colonization can be asymptomatic, and it is considered not pathogenic. However, it is able to invade lacerated oral mucosa, where it ingests fragments of live cells, suggesting pathogenous potential. Here, we characterized the transcriptomes of gingival cells after infection with E. gingivalis using RNA sequencing and observed pathogen interaction with the epithelial monolayer barrier by scanning electron microscopy. In epithelial and fibroblast cells, strongest differential expression showed gene set “chemokines and inflammatory molecules in myeloid cells” (area under the curve [AUC] = 0.9, effect size 5.15, adjusted P = 3.1 × 10⁻¹⁹) and “cell cycle and growth arrest” (AUC = 0.91, effect size = 4.56, adjusted P = 4.8 × 10⁻⁹), respectively. The most upregulated genes were TNF (fold change 430) and IL8 (fold change 359) in epithelial cells and ZN331 (fold change 18) in fibroblasts. We showed that E. gingivalis killed live epithelial cells by trogocytosis, demonstrating strong pathogenic potential.

Occurrence and characterization of Acanthamoeba similar to genotypes T4, T5, and T2/T6 isolated from environmental sources in Brasília, Federal District, Brazil

Species of Acanthamoeba can cause keratitis and brain infections. The characterization of environmental isolates is necessary to analyze the risk of human infection. We aimed at identifying and genotyping Acanthamoeba isolates from soil, swimming pools, and water features in Brasília, Federal District, Brazil, as well as determining their physiological characteristics and pathogenic potential. Among the 18 isolates studied, eight were similar to genotype T5, five to T4, and one to T2/T6, classified by the sequence analysis of 18S rDNA. Genotypes of four isolates were not determined. Ten isolates (55%) grew at 37 °C and seven (39%) grew in media with 1.5M mannitol, which are the physiological parameters associated with pathogenic Acanthamoeba; also, four isolates from swimming pools presented high pathogenic potential. Our results indicate a widespread distribution of potentially pathogenic Acanthamoeba T4, T5, and T2/T6 in different environmental sources in Brasília, revealing the potential risk of human infection and the need of preventive measures.

Phylogenetic evidence for a new genotype of Acanthamoeba (Amoebozoa, Acanthamoebida)

Acanthamoeba are widespread free-living amoebae, able to cause infection in animals, with keratitis and granulomatous encephalitis as major diseases in humans. Recent developments in the subgenus classification are based on the determination of the nucleotide sequence of the 18S rDNA. By this mean, Acanthamoeba have been clustered into 15 sequence types or genotypes, called T1 to T15. In this study, we analysed near full 18S rDNA of an Acanthamoeba recovered from an environmental sample and various unidentified Acanthamoeba sequences retrieved from GenBank. We provided phylogenetic evidence for a new genotype, which we proposed to name T16.

Biological characterization of a clinical and an environmental isolate of Acanthamoeba polyphaga: analysis of relevant parameters to decode pathogenicity

Acanthamoeba spp. consists of free-living amoebae, widespread in nature, which occasionally can cause human infections including granulomatous amoebic encephalitis and amoebic keratitis. Acanthamoeba pathogenesis is not entirely known and correlations between pathogenic potential and taxonomy are complex issues. In order to decipher the definition of a pathogenic amoeba, the objective of this work was to decipher the definition of pathogenic amoeba by characterizing two isolates of Acanthamoeba polyphaga obtained from different origins (a keratitis patient and freshwater), looking for differences among them. The clinical isolate grew faster in Peptone-yeast extract-glucose (PYG) medium, transformed more rapidly from a trophozoite to cyst and exhibited increased cytopathic effect on cultured cells. Morphological differences were also noted, since freshwater amoebae presented more acanthopodia than the clinical isolate. Moreover, actin labeling demonstrated that microfilament organization varies between isolates, with the presence of locomotory structures as lobopodia and lamellipodia in the keratitis isolate, which were less adherent on plastic. Zymography demonstrated that the keratitis isolates presented higher proteolytic activity and also were more able to invade collagen matrices. Altogether, we conclude that a group of stable physiological characteristics exist in Acanthamoeba that can be related to pathogenicity.