Genome-wide identification of pathogenicity factors of the free-living amoeba Naegleria fowleri

Abstract

BackgroundThe free-living amoeba Naegleria fowleri is the causative agent of the rapidly progressing and typically fatal primary amoebic meningoencephalitis (PAM) in humans. Despite the devastating nature of this disease, which results in > 97% mortality, knowledge of the pathogenic mechanisms of the amoeba is incomplete. This work presents a comparative proteomic approach based on an experimental model in which the pathogenic potential of N. fowleri trophozoites is influenced by the compositions of different media.ResultsAs a scaffold for proteomic analysis, we sequenced the genome and transcriptome of N. fowleri. Since the sequence similarity of the recently published genome of Naegleria gruberi was far lower than the close taxonomic relationship of these species would suggest, a de novo sequencing approach was chosen. After excluding cell regulatory mechanisms originating from different media compositions, we identified 22 proteins with a potential role in the pathogenesis of PAM. Functional annotation of these proteins revealed, that the membrane is the major location where the amoeba exerts its pathogenic potential, possibly involving actin-dependent processes such as intracellular trafficking via vesicles.ConclusionThis study describes for the first time the 30 Mb-genome and the transcriptome sequence of N. fowleri and provides the basis for the further definition of effective intervention strategies against the rare but highly fatal form of amoebic meningoencephalitis.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-496) contains supplementary material, which is available to authorized users.

Naegleria fowleri: Sources of infection, pathophysiology, diagnosis, and management; a review

“…Amphotericin B acts on target cells by binding to ergosterol present in the cell membrane alter membrane permeability by forming pores and hence cause cell death. However, the use of this drug alone or in combination with other drugs treated not more than a dozen patients successfully while approximately more than 350 cases of PAM have been reported worldwide . The number of patients treated with amphotericin B is 36 while only three (8%) patients survived …”

“…However, the use of this drug alone or in combination with other drugs treated not more than a dozen patients successfully while approximately more than 350 cases of PAM have been reported worldwide. 79,80 The number of patients treated with amphotericin B is 36 while only three (8%) patients survived. 21 Several experiments were performed to determine the efficacy of amphotericin in combination with other drugs because of its several side effects.…”

Primary Amebic Meningoencephalitis: What Have We Learned in the Last 5 Years?

“…Sometimes, a genomic comparison between a pathogenic species and a closely related non-pathogenic species can help identify pathogenicity or virulence factors. The genome of a non-pathogenic Naegleria species, N. gruberi , was sequenced in 2010 and the genome sequence of N. fowleri was reported in 2014 [35, 36]. However, comparison of the two suggest that the N. gruberi genome is too diverse to compare to N. fowleri to identify pathogenicity or virulence factors in the latter ameba.…”

“…Comparative studies using transcriptomic and proteomic data from highly and weakly virulent N. fowleri trophozoites have identified about two dozen potential targets that may be directly involved in amebic pathogenicity and virulence [36]. Recently, a matrix-assisted laser-desorption-ionization-time-of-flight (MALDITOF) mass spectrometry approach has been used to identify protein biomarkers for pathogenic N. fowleri using 18 N. fowleri strains (including 14 from PAM cases and 4 from environmental sources) and 6 non-pathogenic Naegleria species: N. gruberi , N. lovaniensis , N. australiensis , N. dunnebackei , N. jadinii , and N. italica [39].…”

Closed-Tube Barcoding

“…Originally, all Naegleria were grouped in the species N. gruberi, but then an opportunistic human pathogenic species was found and named N. fowleri (Fulton 1970). Studies quickly showed that the genus is extremely diverse (Fulton 1993), a conclusion confirmed by the marked differences in gene sequences and gene order between the genomes of N. gruberi (Fritz-Laylin et al 2010) and N. fowleri (Zysset-Burri et al 2014). Studies by several methods, but mostly using sequences of the ITS1 region of the ribosomal plasmid present in all species, have indicated that there are about 40 species in the genus Naegleria (De Jonckheere 2004, 2008.…”