- Volume 42, Issue 2, 1979

The study of human cytomegalovirus (HCMV) in cultures of human embryo lung fibroblasts, pre-treated with actinomycin D, has shown that under these conditions the virus infection does not proceed beyond the ‘early’ events of the virus replication cycle.

In the same experimental conditions the growth of poliovirus type 1, vaccinia virus and herpes simplex type 1 virus, was completely unaffected.

These results suggest that the complete HCMV replication cycle requires some cellular function(s) between early transcription of the input virus genome and virus DNA synthesis.

In G1-arrested cells infected between 1 and 12 h after having been stimulated by fresh serum to progress to S phase, polyoma virus DNA synthesis proceeded in the first half of S phase, and virus and whole cellular DNA accumulated at about the same time. However, in cells infected later than 14 h after serum stimulation, virus DNA synthesis was shifted to the next S phase. Thus, a permissive cell attains competence for polyoma virus DNA replication at a precise moment during an S phase initiated by fresh serum, which can efficiently replace the early virus host DNA stimulation function. When cells were incubated in serum that had lost its capacity to stimulate host DNA synthesis by pre-absorption with growing cells, normal yields of polyoma DNA could nevertheless be observed, which shows that extensive replication of host DNA does not seem to be an obligatory condition for virus DNA replication.

The influence of araT on the synthesis of HSV of types 1 and 2 including a TK(-) variant, on the activity of the dThd and the dCyd kinases and on the incorporation of radioactivity into insoluble or soluble material after infection was studied. AraT inhibited different parameters of the replication of a TK(-) variant; it is possibly phosphorylated by enzymes other than the deoxypyrimidine kinase and therefore it is less selectively phosphorylated than dThd. The mode of action of araT on herpes replication must be studied in more detail.

Mengovirus particles adsorbed to Ehrlich ascites tumour cells are redistributed into patches and caps without the action of antibodies. Thus capping may be an early signal in picornavirus infection.