Cytomegalovirus interference in vitro.

Cytomegalovirus (CMV) was shown to induce a state of viral interference in human embryo fibroblast cultures (HEF). This interference was characterized by: (i) requirement for infectious virus; (ii) a latent period (48 to 96 h) for establishment of the interference; (iii) activity against a representative group of heterologous viruses; (iv) loss of interfering activity when challenged with a high multiplicity of infection; (v) lack of effect on adsorption of virus; (vi) mediation by a soluble product of CMV-cell interaction that it is not blocked by anti-CMV antibody; and (vii) absence of detectable interferon, although the soluble mediator shares a number of characteristics with interferon. This state of interference in HEF cultures could be simulated by extended exposure to subdetectable levels of human interferon. It is postulated that CMV induced the production of a soluble, interferon-like mediator of viral interference and that continuous exposure of the HEF culture to this mediator resulted in the development of resistance to a number of heterologous viruses.