Three DNA viruses, vaccinia, herpes simplex, and adenoviruses, have been studied for thermal inactivation in the presence of monovalent and divalent cations. Na+ protected vaccinia and adenoviruses from inactivation at 50°C, but Mg++ and Ca++ markedly increased the rate of inactivation of all three agents. This confirms our earlier observation with another DNA virus (vacuolating SV40) (12) and is in contrast to the remarkable stabilizing effect exerted by divalent cations on the small RNA viruses (9, 10).


This work was supported in part by the Epidemiology Fund, Houston, Texas, and in part by a training grant, 2E-74, from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, U. S. Public Health Service, Bethesda, Md.

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