A Transmissible Interfering Stomatitis Virus Component of Vesicular Preparations

Abstract

Serial (more than two) undiluted passages of vesicular stomatitis virus in chick embryo cell monolayers gave low virus yields (e.g., 10 plaque-forming units (pfu/cell) compared with dilute passage (e.g., 1000 pfu/cell). It was concluded that the low yields resulted from production of a transmissible interfering component since a mixture of undiluted passage with dilute passage virus stocks also gave low yields. Lack of some cells, lack of time for complete growth, genotypic viral change, virus inactivation, poor cultures or media variations were excluded as explanations. Yield increase with inoculum dilution was marked with undiluted passage but not with dilute passage stocks. Multiple infection with liver virus (dilute passage stocks) gave high yields, and mixed infection between plaque-forming units and transmissible interfering component (T) was required for interference and for propagation of T. Heat or u.v.-inactivation of live virus did not render it able to interfere (i.e., did not form T). The interference was mostly exclusion (all-or-none) with some slowing of release, since cells which released plaque-forming units released the normal number. T by itself was not toxic, and those cells which received T but not plaque-forming units in the first cycle of growth were protected from degeneration for several days. Cells which received T and plaque-forming units were killed whether or not they released virus.