Investigations of virus-protozoa relationships in the model of the free-living ciliate Tetrahymena pyriformis and adenovirus type 3

Cultures of the free-living ciliate, Tetrahymena pyriformis, strain GL were experimentally infected with adenovirus type 3 (Ad3). The course of interaction was followed over a five-day period and in four successively passaged subcultures in virus-free medium. Possible presence of viral genomic DNA in the ciliates was assayed by DNA-DNA hybridization, allowing the detection of 100 pg of homologous DNA. The presence of viral protein was tested by time-resolved fluoroimmunoassay (TR FIA) enabling to detect less than 5 ng of Ad3 hexon antigen per ml. In ciliate culture supernatants the presence of virus was tested by TR FIA and by estimation of viral titers (PFU tests). Viral genome was detected in the ciliates over the first two days post-infection and not later. Antigen concentration in the supernatant was negative by the fourth day of the experiment and on the tenth day no virus was detected by PFU tests. During passages in virus-free medium, viral genome was detected only in the ciliates of the first subculture, the antigen concentration was negative after the second passage. In addition, no viral titer could be detected after this time. Our data do not support the hypothesis that Ad3-replication takes place in T. pyriformis.