While Naegleria fowleri is an etiological agent of primary amebic meningoencephalitis, the mecahnisms by which this organism produces host brain cell injury is not understood. Lipolytic enzymes of the amebae have been suggested to play a role in the pathogenesis of primary amebic meningoencephalitis. However, the occurrence, characteristics, and regulation of such enzymes in the invading cells, or their effect on host cells has not been examined. Therefore, we propose to carefully compare the phospholipases (A1, A2, C, spingomyelinases and lysophospholipases) of pathogenic (N. fowleri) and (N. gruberi) species of Naegleria, and those enzymes that appear in the culture media. We wish to determine if these enzymes can perturb and/or degrade brain cell membranes. Lipolytic enzymes from both N. fowleri, N. gruberi, and their growth media will be quantitatted and characterized with respect to intracellular localization, pH, and cation requirements, substrate and positional specificities; physiological and pharmacological modulators of activity will be studied. Phospholipases will be isolated from the cells and/or media, and their ability to perturb biomembranes and function (ion permeability and cell viability) of cultured neural cwlls will be tested. The extent of host cell injury will be correlated to phospholipid degradation by quantitative thin layer and gas-liquid chromatography. Hopefully this study will demonstrate the role of lipolytic enzymes in the pathogenesis of Naegleria-induced primary amebic meningoencephalitis. Such a study may provide a better understanding of other protozoan diseases, and may illustrate a basic mechanism of membrane and cell injury common to a variety of diseased states and could lead to efficacious drug treatment.