Summary
Viral and cellular growth and sequential content of total protein and DNA were studied in chick epithelium infected in vivo with fowlpox virus. The first evidence of epithelial hyperplasia associated so prominently with fowlpox was noted after 48 hours of infection and was manifest as a 2.5-fold increase in cell number at 72 hours postinoculation. The initiation of viral replication preceded hyperplasia by at least 12 hours, and the titer increased exponentiallly through 96 hours of infection. Development of the mature lesion was accompanied by 7-fold increases in protein and DNA content of infected epithelium. Although viral replication was initiated prior to induction of the proliferative response and was subsequently concomitant with hyperplasia, production of infectious virus was limited during this period to only 1% of the maximum titer. Thus, while all discernible evidence of cellular proliferation was confined to the period of infection between 48 and 72 hours postinoculation, 99% of the total virus was attained between 72 and 96 hours. It is proposed that the pathogenesis of the in vivo lesion of fowlpox involves two almost distinct biological phases consisting of initiation of viral replicaton and epithelial hyperplasia with concomitant production of a very small percentage of the total virus during the first 72 hours of infection, followed by cessation of cellular proliferation with production of almost all infectious virus.
