Latent viral infection of cells in tissue culture. I. Studies on latent infection of chick embryo tissues with psittacosis virus.

Chick embryo tissues maintained for from 11 to 28 days in Hank's balanced salt solution lost their capacity to support the multiplication of psittacosis virus. The virus however infected such cells, as active multiplication of the virus occurred on the addition of beef embryo extract to this nutritionally poor medium at any period up to 28 days of cultivation in balanced salt solution. The virus remained in a state of latency for as long as 15 days in these starved cells in a non-infectious phase. These results obtained in this in vitro model system for the investigation of latent infections of cells with psittacosis virus suggest that cell nutrition as well as an alteration in the immunological defenses of the host may prove to be an important factor in the activation of latent viral infections.