Effect of Cations on Thermal Inactivation of Vaccinia, Herpes Simplex, and Adenoviruses¹

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).