Biosynthesis of host and viral deoxyribonucleic acid during hyperplastic fowlpox infection in vivo.

The synthesis of deoxyribonucleic acid (DNA) during in vivo infection of chick epithelium with fowlpox virus was examined by incorporation of tritiated thymidine into the acid-insoluble fraction. The proportion of precursor incorporated into host and viral DNA at various times after infection was determined by chromatography on columns of methylated albumin-kieselguhr. The first 60-hr period of infection was characterized by the synthesis of predominantly host DNA, the rate of production of which increased markedly over the control between 36 and 48 hr postinoculation (PI). Although the replication of viral DNA began between 12 and 24 hr PI, the rate of synthesis was very low during the first 60 hr. In contrast, an abrupt increase in the rate of viral DNA synthesis occurred between 60 and 72 hr PI, concomitantly with a sharp decline of host DNA synthesis. Subsequently, between 72 and 96 hr, the ratio of synthesis of viral DNA to host DNA progressively increased to a maximum of greater than 2:1. The temporal relationship of this biphasic pattern of host and viral DNA synthesis to hyperplasia and viral replication is discussed.