ALTHOUGH rubella virus can be propagated in a wide range of cell types from several species of animal, there is still only a limited number of tissues in which visible cytopathic effects have been reported.1 Furthermore, despite the large variety of human embryonic organs which may be damaged by rubella virus,2 the only two human tissue cultures known to show cytopathic effects are amnion and adult thyroid.3,4
Attempts have been made to explain this paradox by Plotkin et al.5 They saw no cytopathic effects in any human embryonic system tested but found that the number of generations for which an infected cell population could be cultivated might be severely curtailed if the culture was chronically infected with rubella virus.
The limited number of laboratory assay systems for rubella virus based on recognition of cytopathology has led to the widespread adoption of refinement of the indirect interference