Identification of "Ryan Virus" as an amoeba of the genus Hartmannella.

A recent paper (Pereira, et al., 1966) reported the isolation in Britain of several strains of an antibiotic-resistant infective agent that caused unusual cytopathic effects when inoculated into cell cultures. The new agent was evidently recoverable from the respiratory tract in certain patients, mostly young children, with illnesses of varying severity but with fever and respiratory symptoms as common features. Primary isolations were made in HeLa or monkey-kidney-cell cultures, and the agent was successfully subcultured in a wide range of cell types. Nuclear changes with eosinophilic inclusions developed within 24 hours in inoculated cultures, followed in two to three days by disintegration of the cell sheet. The effect was suppressed by 5-fluoro-deoxyuridine ; however, it was not possible to separate infectivity from cell debris. It was concluded that the respon- sible agent was a virus, firmly cell-associated and perhaps related to the varicella-cytomegalovirus subgroup of the herpes viruses. It was provisionally called Ryan virus. For further characterization of the agent, cell cultures and a number of normal and inoculated organ cultures of human embryo trachea were passed to the Laboratory of Cytopathology, National Institute for Medical Research, for electron microscopy and cytological study. This has revealed the presence of a protozoal cell-type in all specimens inoculated with the Ryan agent; the findings, as detailed below, suggest that the cytopathic changes previously reported are attributable to an amoeba of the genus Hartniannella.