CHEMISTRY OF VIRAL INFECTED CELLS *

Upon the basis of limited data available ten years ago, a concept of viral infection became popular in which the cell was redirected after infection to the exclusive production of virus. These original data (Cohen, 1949) that concerned the quantitative accounting of the nucleoproteins during the infectious sequence, offered a direct line of investigation into the mechanism of this redirection and into the genesis of the cytopathic effect of the Ta phage of Escherichia coli. Since the early work of Cohen, there have been few attempts to establish an accounting of large molecules during infection with other viruses, particularly in well-defined systems of animal virsues. Such investigation is complicated by the fact that the yield of virus from infected animal cells is frequently low relative to the cell mass. What determines the yield is an interesting problem in itself, as well as how that viral production leads to cell destruction. At present there is no simple answer. It may be that the cytopathic effect terminates the viral production rather than the latter mediating the cytopathic effect. However, a quantitative analysis of cells and fractions thereof infected with poliovirus was undertaken in our laboratory several years ago, and it was quickly established that, although the amount of virus formed was small, there were indeed massive increases in the total RNA and protein of the cell during the infectious process (Ackermann et al., 1959). These results have been confirmed elsewhere by microspectrophotometric analysis of single infected cells (G. Barski, personal communication; Tenebaum, 1957). They are further supported by the series of studies of the proteins and enzymes of cells infected with poliovirus (Matzelt el d., 1958). If a viral cytopathic effect requires a specific or locally restricted synthesis of an amount of material large relative to the cell mass, this is available in the poliovirus infection. Since the report of these changes in cells induced by infection with the poliovirus, alterations of nucleic acid content of cells have been observed during the infectious sequence of several viral systems. Data concerning this point were collected in many laboratories and are not entirely comparable in all respects, but they have been summarized in TABLE 1. In these examples, the infected cells do not seem to be devoted to the exclusive production of materials that constitute what is usually regarded as the viral body.