STUDIES OF MOUSE POLYOMA VIRUS INFECTION : II. VIRUS STABILITY

Mouse polyoma virus was stored at 4° and –60°C. for 8 weeks without any loss in hemagglutination or infectivity titer; storage at 37° for 8 weeks reduced infectivity titer by approximately 2.5 log₁₀ units. Repeated freezing and thawing of infectious tissue culture fluid had no effect on virus titer. The stability of the virus to storage for 1 week at 4°C. was unaffected by suspension of infected tissue culture fluid in saline, demineralized distilled water, or 5 per cent horse serum in Eagle's basal medium. Heating the virus for 30 minutes at 60°C. had no effect on infectivity and hemagglutination titers. Heating at 65°C. for 30 minutes produced a 3 log unit loss of infectivity and a 4-fold decline in HA titer, and heating at 70°C. for 30 minutes usually produced complete inactivation of infectivity and HA. The virus was resistant to ultraviolet irradiation; ultraviolet irradiation for 2 hours caused a 4 log unit decrease in infectivity titer without affecting the HA titer. The virus was resistant to exposure to 2 per cent phenol and 50 per cent ethyl alcohol but was inactivated by 100 per cent ethyl alcohol, and ethyl alcohol-iodine mixtures. Lyophilization had no effect on the stability of the virus.