Structural proteins of two different plaque-size phenotypes of fowlpox virus.

Structural polypeptides of two plaque-purified variant isolates of fowlpox virus differing in plaque morphology and size were examined by Coomassie blue-staining and immunoblot analysis of purified virions. A total of 30 structural polypeptides were observed, ranging in molecular weight from 14,100 to 122,600. A late polypeptide of 36,400 molecular weight was quite prominent in the small-plaque clone but absent in the large-plaque clone. Two other polypeptides, of 33,700 and 34,800 molecular weight, were present in virions from large-plaque virus and cell lysates of both clones but were absent in the small-plaque virions. These differences were observed whether the viruses were grown in chorioallantoic membrane or in chicken embryo fibroblast cultures. No difference was observed between the growth curves of the two virus clones. Differences observed in the polypeptides of the two viruses may be due to changes in the less conserved regions of viral DNA and may be used for differentiation of virus isolates.

Fowlpox virus polypeptides: sequential appearance and virion associated polypeptides.

The polypeptides associated with fowlpox virus (FPV) infection of chicken embryo skin (CES) cells were examined by metabolic labelling with [35S]-methionine and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Polypeptide synthesis was followed over the first 48 hours post infection, as this was shown to be the period of viable virus production in CES cells. In contrast to infection with vaccinia virus (VV), which leads to a rapid total inhibition of host polypeptide synthesis in a number of cell lines, FPV infection of CES cells failed to cause a complete shut down of host polypeptide synthesis, with only a small number of host polypeptides being inhibited. A total of 21 FPV coded or induced polypeptides were resolved by metabolic labelling. As with VV, these polypeptides can be divided into two groups, the pre-replicative polypeptides containing a single member of 70,000 daltons, synthesised before viral DNA replication, and the post-replicative polypeptides, synthesised only after viral DNA replication has commenced. FPV DNA replication was shown to commence between 12 and 16 hours post-infection and to continue up to 48 hours post-infection. As also observed with VV, two temporally distinct classes of post-replicative polypeptides were identified based on their time of synthesis post-infection. The examination of purified FPV and VV by SDS-PAGE and coomassie blue staining allowed the resolution of 57 FPV particle associated polypeptides and 27 VV associated polypeptides.