Taxonomy Acanthamoeba royreba sp. n. from a Human Tumor Cell Culture*

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Abstract
Acanthamoeba royreba was isolated from a culture of an established line of human choriocarcinoma cells. The identification of this strain, originally called the Oak Ridge strain, and the establishment of a new species for it were based on morphologic, serologic and immunochemical studies. In general, the structure of the trophozoite did not differ significantly from that of other species of Acanthamoeba, except that a body which more closely resembled a centriole than material described previously as centriolar satelites was observed in trophozoites examined with EM. The dimensions of the trophozoite were the smallest among the species of Acanthamoeba. The cyst was typical of the genus, but differed from those of other species by its smaller size and the presence of numerous ostioles. Studies of the Oak Ridge strain by immunofluorescence using antisera developed against the isolate and A. culbertsoni, A. castellanii, A. polyphaga, A. rhysodes, A. astronyxis and A. palestinensis revealed the antigenic uniqueness of the Oak Ridge strain. Immunoelectrophoretic analyses of soluble proteins of the Oak Ridge strain showed that it shared .apprx. 1/2 of its antigenic structure with A. castellanii and A. culbertsoni. The antigenic differences of the isolate from other Acanthamoeba spp. were deduced from comparison of the antigenic constitution of these species and the Oak Ridge strain with A. culbertsoni and A. castellanii. Although the strain was initially recognized by its cytopathogenicity for cultures, it did not produce acute infections in mice after intranasal inoculation of 1 .times. 104 amebae/mouse.