Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 81

One of the most important procedures in virology is measuring the virus titer, the concentration of infectious virus particles in a sample. This parameter is determined by inoculating serial dilutions of virus into host cell cultures, chicken embryos, or laboratory animals and monitoring for evidence of virus multiplication. The response may be quantitative (as in assays for plaques, fluorescent foci, infectious centers, or abnormal growth and morphology) or all-or-none, in which the presence or absence of infection is measured (as in an end-point dilution assay). Please note that “titer” is not a verb.

Figure 2.6 Growth of viruses in embryonated eggs. The cutaway view of an embryonated chicken egg shows the different routes by which viruses are inoculated into eggs and the distinct compartments in which particular viruses may propagate.

Figure 2.7 Plaques formed by different animal viruses. (A) Photomicrograph of a single plaque formed by pseudorabies virus in bovine kidney cells. Shown are unstained cells (left) and cells stained with the chromogenic substrate X-Gal (5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside), which is converted to a blue compound by the product of the lacZ gene carried by the virus (right). Courtesy of B. Banfield, Princeton University. (B) Plaques formed by poliovirus on human HeLa cells stained with crystal violet. (C) Illustration of the sequential spread of a cytopathic virus from an initial infected cell to neighboring cells, resulting in a plaque.