In vitro interactions between Neoparamoeba sp. and Atlantic salmon epithelial cells

Abstract

Neoparamoeba sp., including the putative aetiological agent of amoebic gill disease in cultured fish (N. pemaquidensis), were incubated in vitro with an Atlantic salmon gill epithelium (RGE-2) cell line. Proliferation by the amoeba population was dependent upon culture osmolarity; no growth occurred at 330 mm x kg(-1) but a sixfold increase was observed at 1000 mm x kg(-1). At 780 mm x kg(-1) there was a fourfold increase in the amoeba population but a concurrent decrease in RGE-2 cell density that was significantly greater than that caused by the high culture osmolarity alone. This apparent cytopathic effect (CPE) developed rapidly and resulted in complete cytolysis of the monolayer in 5 days. CPE occurred in multiple foci and presented as cell vacuolation, rounding and clumping, and the rapid clearance of large areas of the cell monolayer. The possibility that CPE is because of the presence of Neoparamoeba sp. derived cytolytic products is discussed in the context of the pathology of the disease in vivo and the occurrence of secreted cytopathogenic compounds in other amoeba species.

Neoparamoeba perurans loses virulence during clonal culture

“…An ECP from Neoparamoeba sp. (isolated from AGD affected gills) also showed a CPE in a salmon cell line (Butler and Nowak, 2004). The production of ECPs by free-living amoebae that induce host-cell cytopathic effects in vitro is well documented (Serrano-Luna et al, 2013).…”

Changes in the interbranchial lymphoid tissue of Atlantic salmon (Salmo salar) affected by amoebic gill disease

“…A cytopathic effect of Neoparamoeba pemaquidensis in the gill epithelium of Atlantic salmon has been suggested [29,30]. A protease-like exotoxin released by N. perurans has been proposed to stimulate the necrosis of epithelial cells seen ultrastructurally in affected Atlantic salmon [31].…”

Respiratory pathogenesis of amoebic gill disease (AGD) in experimentally infected Atlantic salmon Salmo salar

“…Although the precise cause of AGD-associated mortality remains unknown, this, along with the results from the present study, suggests that AGDassociated mortality in cultured fish is not caused by respiratory failure. Powell et al (2002a,b) have suggested AGD may possibly be associated with cardiovascular dysfunction, perhaps due in part to possible cytopathic effects of the amoebae (Butler & Nowak 2004); however, the actual cardiovascular responses of Atlantic salmon to infection, or extracellular amoeba products, have not been examined.…”