Studies on the Temperature-dependent DNA Replication of the Herpesvirus of the Turkey in Chicken Embryo Fibroblasts

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Abstract
Development of cytopathogenic changes in chicken embryo fibroblasts (CEF) infected with the herpesvirus of the turkey, strain PB-THVI, and the release of virus particles into the supernatant of infected cultures is accelerated at temperatures higher than 37.degree. C and is fastest at 41.degree. C, the normal body temperature of chickens. Growth rate of HVT in CEF cultures was followed by determination of the number of virus genome equivalents within infected cells at various time intervals p.i. [post-inoculation]. Temperature-dependent increase in amount of virus DNA/infected cell could be detected, which is highest at 41.degree. C. All temperatures tested (34, 36, 41 and 43.degree. C) the number of virus genome equivalents/infected cell ultimately reaches the same level. During infection, virus DNA in CEF cultures at 37 and 41.degree. C becomes associated with the cellular DNA, as determined by neutral CsCl gradients of the total cellular DNA and hybridization of each fraction with 32P-labeled virus-specific complementary RNA. Association of virus to cellular DNA occurs earlier at 41 than at 37.degree. C. The same proportion (45%) of the total virus DNA appears associated with cellular DNA at both temperatures. A temperature shift to CEF cultures infected with PB-THVI from 41 to 37.degree. C 24 h p.i. resulted in the same replication kinetics of virus DNA as was found at 41.degree. C.