Suppressed Synthesis of Viral DNA, Protein, and Mature Virions during Replication of Canine Herpesvirus at Elevated Temperature

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Abstract
Canine herpesvirus was synthesized optimally in canine renal cell cultures incubated at 36 C-37 C. Yields of infectious virus at 40 C were only about 0.1% of those obtained at 36 C. Studies to delineate the steps in viral biosynthesis suppressed at 40 C revealed that synthesis of viral DNA continued, although the rate of synthesis was reduced to 50% of that at 36 C. Specific viral proteins were made at the elevated temperature, but only 50% of normal amounts were present. When DNA synthesis was blocked with cytosine arabinoside, formation of viral protein was dramatically arrested, indicating that continued production of viral DNA was required to make viral antigens. While titers of infectivity decreased 103- to 104-fold at 40 C, synthesis of viral DNA and protein were reduced only 50%. Infected cells incubated at 36 C for up to 8 hr and shifted to 40 C made infectious virus as if the whole growth cycle took place at 40 C. When infected cells were kept at 40 C for 8 hr and then shifted to 36 C, titers of infectious virus were as if the whole growth cycle occurred at 36 C. It is suggested, therefore, that formation of infectious canine herpesvirus is suppressed at 40 C due to a combination of decreased viral DNA and protein synthesis, in conjunction with deranged maturation of virions.

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