Immunodominant antigens in Naegleria fowleri excretory–secretory proteins were potential pathogenic factors

Abstract

Naegleria fowleri, a ubiquitous pathogenic freeliving amoeba, is the most virulent species and causes primary amoebic meningoencephalitis in laboratory animals and humans. The parasite secretes various inducing molecules as biological responses, which are thought to be involved in pathophysiological and immunological events during infection. To investigate what molecules of N. fowleri excretory-secretory proteins (ESPs) are related with amoebic pathogenicity, N. fowleri ESPs fractionated by two-dimensional electrophoresis were reacted with N. fowleri infection or immune sera. To identify immunodominant ESPs, six major protein spots were selected and analyzed by N-terminal sequencing. Finally, six proteins, 58, 40, 24, 21, 18, and 16 kDa of molecular weight, were partially cloned and matched with reference proteins as follow: 58 kDa of exendin-3 precursor, 40 kDa of secretory lipase, 24 kDa of cathepsin B-like proteases and cysteine protease, 21 kDa of cathepsin B, 18 kDa of peroxiredoxin, and 16 kDa of thrombin receptor, respectively. These results suggest that N. fowleri ESPs contained important proteins, which may play an important role in the pathogenicity of N. fowleri.

Peroxiredoxins in Parasites

“…N. fowleri is a free-living amoeba that causes primary amoebic meningoencephalitis, a rare but acute and frequently fatal central nervous system disease. The genome has not yet been sequenced, but an 18-kDa Prx (matching a Prx1 from Aedes aegypti by its N-terminal sequence) was identified as an excretory-secretory pathogenic factor in N. fowleri infection (122). While it was not cloned and so may not be a Prx1, the sequenced genome of the nonpathogenic Naegleria gruberi (84) contains a Prx1 and a Prx5 (NCBI accession numbers XP_002678814 and XP_002680895, respectively).…”

Naegleria fowleriLysate Induces Strong Cytopathic Effects and Pro-inflammatory Cytokine Release in Rat Microglial Cells

“…However, the precise mechanisms by which they exert their pathogenicity are unknown. Previous researches have suggested that infection may evoke both contact-dependent and contact-independent CNS pathology [7-11]. …”

“…To elucidate the contact-independent mechanism for amebic pathogenicity, researchers have attempted to examine the cytopathic effects of incubating N. fowleri secreted proteins (excretory-secretory proteins; ESPs) or acanthamoebic lysate or their secreted proteins against a number of target cell types [9-11,14,15]. However, no studies have examined the specific effects of N. fowleri lysate on microglial cells in experimental models of PAM.…”

“…Kim et al [10,11] performed an LDH release assay to evaluate the cytotoxicity of N. fowleri ESPs on human microglial cells or Chinese hamster ovary (CHO) cells, and likewise found a time- and dose-dependent rise in cytotoxicity consistent with a pathogenic role for ESPs [10,11]. An analysis of N. fowleri whole-cell lysate found 2 major protein bands (13 and 21 kDa), predicted to be the Nfa1 and proteinase proteins [11,21]. These may constitute efficacious cytolytic factors in amebic lysate, and an in-depth fractionation and biochemical characterization will help elucidate the pathogenicity induced by amebic lysate.…”

NLRP3 Inflammasome Activation in THP-1 Target Cells Triggered by Pathogenic Naegleria fowleri

“…In the contact-dependent mechanisms, the Nfa1 protein and actin protein were characterized and identified in N. fowleri infections (11,30). In addition, excretory-secretory proteins (ESPs) released from N. fowleri have also been identified, and these may play an important role in its pathogenicity (31).…”