[Cell-mediated immunity in mice infected with Acanthamoeba culbertsoni]

Pathogenic free-living amoebae in Korea

Acanthamoeba and Naegleria are widely distributed in fresh water, soil and dust throughout the world, and cause meningoencephalitis or keratoconjunctivitis in humans and other mammals. Korean isolates, namely, Naegleria sp. YM-1 and Acanthamoeba sp. YM-2, YM-3, YM-4, YM-5, YM-6 and YM-7, were collected from sewage, water puddles, a storage reservoir, the gills of a fresh water fish, and by corneal washing. These isolates were categorized into three groups based on the mortalities of infected mice namely, highly virulent (YM-4), moderately virulent (YM-2, YM-5 and YM-7) and nonpathogenic (YM-3). In addition, a new species of Acanthamoeba was isolated from a freshwater fish in Korea and tentatively named Korean isolate YM-4. The morphologic characters of its cysts were similar to those of A. culbertsoni and A. royreba, which were previously designated as Acanthamoeba group III. Based on experimentally infected mouse mortality, Acanthamoeba YM-4 was highly virulent. The isoenzymes profile of Acanthamoeba YM-4 was similar to that of A. royreba. Moreover, an anti-Acanthamoeba YM-4 monoclonal antibody reacted only with Acanthamoeba YM-4, and not with A. culbertsoni. Random amplified polymorphic DNA marker analysis and RFLP analysis of mitochondrial DNA and of a 18S small subunit ribosomal RNA, placed Acanthamoeba YM-4 in a separate cluster based on phylogenic distances. Thus Acanthamoeba YM-4 was identified as a new species, and assigned Acanthamoeba sohi. Up to the year 2002 in Korea, two clinical cases were found to be infected with Acanthamoeba spp. These patients died of meningoencephalitis. In addition, one case of Acanthamoeba pneumonia with an immunodeficient status was reported and Acanthamoeba was detected in several cases of chronic relapsing corneal ulcer, chronic conjunctivitis, and keratitis.

[Interleukin-2 production and alteration of T cell subsets in mice infected with Naegleria fowleri]

Naegleria fowleri is the cause of primary amoebic meningoencephalitis in man. IL-2 levels after stimulation of T lymphocytes by PHA or N. fowleri lysates, the amounts of T lymphocyte subsets and the blastogenic responses of T lymphocytes in mice after infected with pathogenic N. fowleri were studied comparing between two study groups, one 1 x 10(4) trophozoites inoculated mice and the other 1 x 10(5) trophozoites inoculated mice. All experimental samples were obtained on the day 7, 14 and 24 after inoculation. The mice inoculated with 1 x 10(4) trophozoites showed a 14.3% mortality rate, and 72.2% in the mice inoculated with 1 x 10(5) trophozoites. The IL-2 levels on day 14 of two experimental groups were significantly decreased as compared with the control group. Thy 1.2+ T cells in the total spleen lymphocytes of 1 x 10(5) trophozoites inoculated group on day 7 were significantly increased compared with the control group. There was no significant difference between 1 x 10(4) trophozoites inoculated group and the control group. L3T4+ T cells and Ly2+ T cells in the total spleen lymphocytes of 1 x 105 trophozoites inoculated group on day 7 were significantly increased compared with the control group. The DNA S fraction of T cells in the spleen of 1 x 10(5) trophozoites inoculated group was significantly increased on day 7. The amount of S fractions of DNA were sequentially decreased on day 14 and 24, but they were also significantly increased compared with the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

[Natural killer cell activity in mice infected with free-living amoeba with reference to their pathogenicity]

The purpose of this observation was to investigate the natural killer cell activities in mice infected with pathogenic free-living amoeba, Naegleria fowleri and Acanthamoeba culbertsoni according to the infection doses, and infected with non-pathogenic free-living amoeba, Naegleria gruberi. The natural killer cell activity was examined by means of target binding capacity, active NK cell and maximum recycling capacity of the mice after inoculating free-living amoebae with low and high doses. The mice infected with 1,103, 1,105 A. culbertsoni trophozoites showed mortality rates of 6.9% and 65.5%, respectively. The mice infected with 1,104, 1,105 N. fowleri trophozoites showed mortality rates of 5.9% and 72.2%, respectively. The NK cell activities in all experimental groups increased significantly on day 1 after infection as compared with control group, and then remarkably declined thereafter, there was no difference of the cytotoxic activity of the NK cells in mice among inoculation doses of pathogenic free-living amoebae. The target binding capacities of NK cells and percentages of activated NK cells in mice infected with pathogenic free-living amoebae were significantly increased a day after infection, as compared with control group. There was no difference of the maximal recycling capacities of NK cells in all experimental groups as compared with control group. There was significant difference in the cytotoxic activity and single cell cytotoxicity of NK cells between the experimental groups infected with pathogenic free-living amoebae and that infected with non-pathogenic free-living amoebae.