Cytopathogenicity of Naegleria fowled for Cultured Rat Neuroblastoma Cells1

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Abstract
The cytopathogenicity of Naegleria fowleri strain LEE (ATCC‐30894) for cultured rat neuroblastoma cells (B‐103) has been investigated. Both live N. fowleri amoebae and Naegleria lysates added to 51Cr‐labeled B‐103 cells caused release of radiolabel, which was dependent upon the ratio of amoebae to target cells or to the lysate concentration. Lysates of N. fowleri strains LEE, NF‐66, NF‐69, and HB‐4 were equally injurious to B‐103 target cells whereas lysates of strains 6088 and KUL were less cytotoxic. Highly pathogenic mouse‐passaged strain LEE were less cytotoxic than axenically grown amoebae. Maximum cytotoxicity was observed in lysates from amoebae in late exponential or early stationary phase of growth. Cytopathogenicity of lysates was reduced after heating at 44°C for 60 min or at 60°C for 30 min. Cytotoxicity was stable during storage at 4°C or at −20°C for 26 h. Neither live amoebae nor lysates injured B‐103 target cells at 4°C. Live amoebae and lysates injured B‐103 by a time, temperature, and concentration dependent process.