Cytopathogenicity of Acanthamoeba isolates on rat glial C6 cell line

The pathogenicity of Acanthamoeba isolates from keratitis patients (the Hamburg isolate from Germany, H-1 and a Philippine isolate, IB-1-7) as well as an environmental isolate, W4 was assayed in vitro using rat glial C6 cell line. Results indicate that both live amebae and cell-free supenatants from H-1 and IB-1-7 clones produced cytopathic effects (CPE) on rat glial C6 cells in a dose-and-time-dependent fashion. A dose of 10(5) cells/ml induced death and moderate areas of destruction of individual cells after 48 hours of incubation. Results of both free zone capillary electrophoresis and sodium dodecyl sulphate polyacrylamide gel electrophoresis suggest the release of amebic products to the culture medium that could at least partially explain the observed cytopathogenicity after 48 hours. Furthermore, results of SDS-PAGE indicate differences between the secretions of the isolates, with bands produced by the two ocular isolates that were not seen with the environmental isolates. That the secretions can produce a cytopathic effect (CPE) has been shown by the cytotoxicity assays using protein concentrations of the secretory products. Protein concentration of 0.30 microg/microl of culture supenatants from H-1 and IB-1-7 clones produced similar effects on the cell monolayers after 2 hours of incubation. This concentration caused the highest % cell death as measured by both trypan blue exclusion (TBE) and 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl-tetrazolium bromide (MTT) assays. In contrast, using W4 clone, corresponding concentrations of both trophozoites and culture supernatant did not cause significant cell death and cellular disintegration.