A multicomponent hemolytic system in the pathogenic amoeba Naegleria fowleri

Abstract

A hemolytic activity associated with postnuclear supernatant fractions of Naegleriafowkri has been partially characterized in an attempt to isolate cytolytic molecules that may participate in naeglerial cytopathogenicity. Hemolysis by naeglerial postnuclear supernatant fractions was sensitive to heat and trypsin hydrolysis, and was inhibited by divalent cations. The m,%jority of the hemolytic activity was nonlatent and associated with a particle fraction sedimenting at 48,000 x g (maximum) for 1 h. This particle-associated hemolytic activity appears to be membrane associated, as high salt concentration, chelating agents, and pH extremes were ineffective in solubilizing the hemolytic activity, whereas treatment with 0.15% Zwittergent 3-12, a dipolar ionic detergent, results in 98% release of the sedimentable hemolysin. The sigmoidal nature of the progress curve of postnuclear supernatant hemolysis, as well as synergistic interactions between fractions of amoebal whole cell extracts, suggests that the hemolytic activity has a multicomponent nature, with at least two and possibly three components participating in the hemolytic event. The significance of these findings in the context of naeglerial cytopathogenicity is discussed.

Free fatty acids released from phospholipids are the major heat-stable hemolytic factor of Entamoeba histolytica trophozoites

“…This cytolytic model for E. histolytica is consistent with the pathogenic role that phospholipases appear to play in other protozoa (10,11,16,20,36). Virulent Naegleria fowleri trophozoites contain much larger amounts of phospholipases than attenuated N. fowleri and avirulent Naegleria sp.…”

“…trophozoites (11). The potentiating role of an amphipatic factor in the phospholipase cytolytic mechanism has been proposed also for N. fowleri (16). Pathogenic T. congolense autolysates are highly hemolytic, whereas those of T. lewisi may be activated with bee venom phospholipase (33).…”

The immune response toNaegleria fowleriamebae and pathogenesis of infection

“…Naegleria fowleri trophozoites have been shown to destroy nerve cells, as well as other cell types, by trogocytosis (i.e. piecemeal ingestion) using a 'food-cup' structure on their surface (Brown, 1979;Marciano-Cabral et al, 1982; and by the release of cytolytic molecules (Lowrey & McLaughlin, 1984, 1985. The mode that is applied to destroy target cells in vitro, however, is dependent on the ameba strain.…”

A Biochemical Comparison of Proteases from Pathogenic Naegleria fowleri and Non‐Pathogenic Naegleria gruberi

“…However, various in vitro studies suggest the presence of several virulence factors that could be involved in the pathogenesis of PAM. Some of these factors are the presence of adhesins (Han et al 2004), pore‐forming proteins (Herbs et al 2002; Young and Lowrey 1989), phospholipases (Barbour and Marciano‐Cabral 2001; Hysmith and Franson 1982), a multicomponent hemolytic system (Lowrey and McLaughlin 1984), the migration pattern of pathogenic strains (Thong and Ferrante 1986), phagocytosis (Marciano‐Cabral 1988), contact‐dependent lysis (Marciano‐Cabral and Fulford 1986), elastase (Ferrante and Bates 1988), and a secreted cysteine protease with cytopathic effects (Aldape et al 1994).…”