Studies of mouse polyoma virus infection. II. Virus stability.

Mouse polyoma virus was stored at 4 degrees and -60 degrees C. for 8 weeks without any loss in hemagglutination or infectivity titer; storage at 37 degrees for 8 weeks reduced infectivity titer by approximately 2.5 log(10) 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 degrees 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 degrees C. had no effect on infectivity and hemagglutination titers. Heating at 65 degrees C. for 30 minutes produced a 3 log unit loss of infectivity and a 4-fold decline in HA titer, and heating at 70 degrees 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.