Abstract
Treatment of dimethyl sulfoxide-stimulated Friend erythroleukemic cells (clone 745) with mouse interferon (50 U/ml) led to the following changes: (i) a net decrease (40 to 60%) in both the total number of apparently newly synthesized virion particles per cell section and in the average number of cell sections containing one or more virion particles; (ii) a large decrease (80 to 90%) in the number of particles released into the supernatant fluid, as assayed by reverse transcriptase activity; (iii) an initial increase in the number of "immature" or "enveloped A-type" virions followed by an increase in the accumulation of empty, core shell-like particles; and (iv) a decrease in the number of cytoplasmic vacuolar structures, which have been implicated as a major site of virus production and which we show here by serial sectioning to be, in several instances, invaginations of the plasma membrane. The effects on virus production were noticeable 2 h after interferon addition and reached their full extent by 13 h. We conclude from these observations that interferon acts upon the late stage(s) of virion maturation, leading both to a decrease in virion production as well as to the formation of defective particles. In contrast, a small but significant increase in the rate at which globin mRNA and hemoglobin accumulate is observed after interferon treatment.