Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 86

The transformation assay provides a method for determining the titers of some retroviruses that do not form plaques. For example, when Rous sarcoma virus transforms chicken embryo cells, the cells lose their contact inhibition (the property that governs whether cells in culture grow as a single monolayer [see Volume II, Chapter 6]) and become heaped up on one another. The transformed cells form small piles, or foci, that can be distinguished easily from the rest of the monolayer (Fig. 2.9). Infectivity is expressed in focus-forming units per milliliter.