Thermostability of Human Immunodeficiency Virus (HIV‐1) in a Liquid Matrix Is Far Higher than That of an Ecotropic Murine Leukemia Virus

For prevention of HIV infection, which is fatal to man and has no known remedy, sterilization of contaminated materials is particularly important. Before applying any sterilization procedures, they have to be checked by accurately following the kinetics of plaque reduction. Though this is almost self‐evident, such studies have been few. Here, a microplaque assay of HIV is established using HPB‐ALL human T‐cells immobilized on a poly‐L‐lysine‐coated plastic dish. This assay was used to compare the ultraviolet and heat inactivation kinetics of HIV (titrated by this method) with those of Moloney murine leukemia virus (MLV) in a liquid matrix. Though the ultraviolet sensitivities of these viruses were identical (D(10)=2,800 ergs/mm(2)), HIV was far more resistant to high temperatures (50°C 70°C) than MLV. This implies that these two viruses have different virion structures, though both are members of retroviridae. The higher thermostability of HIV should be taken into account when HIV‐contaminated materials are handled.