Synergistic Inactivation of Viruses by Heat and Ionizing Radiation

Abstract

Viral inactivation by heat and/or ionizing radiation is analyzed in terms of a kinetic model. The phenomenon of synergistic viral inactivation observed when viruses are exposed to the simultaneous application of heat and ionizing radiation is interpreted within the framework provided by this three-term model. Data on the inactivation of T4 bacteriophage by heat and/or ionizing radiation is presented, and the kinetic model is used to provide a description of observed dose rate and temperature dependences. Extension of the model to other viral systems inactivated by heat and ionizing radiation is considered, and the general applicability of these analyses suggests that the kinetic model may well serve as an extension of target theory in describing the radiobiological effects of ionizing radiation.

Heat-acclerated radioinactivation of attenuated poliovirus

“…This fmding substantiates previous studies on viral inaetivation by eombined treatment [9] and suggests that a synërgistie response may be the common response of viruses to heat and ionizing radiation under appropriate eonditions of temperature and dose rate. This fmding substantiates previous studies on viral inaetivation by eombined treatment [9] and suggests that a synërgistie response may be the common response of viruses to heat and ionizing radiation under appropriate eonditions of temperature and dose rate.…”

“…Fig. The data presented in Table I was used to determine the parametrie values for the generic forms of the inactivation rate parameters [9] by fitting the model to the entire set of data using a least squares norm: The increased rate of inactivation of poliovirus in a composite heat and radiation environment (Fig. The dashed line desigaates the rate of inactiv&tion which would be expected if virus inactivation in a composite therm&l and r&di&tion environment was simply the sum of the rates of inactiv&tion due to hegt (kT) and ionizing radi&tion (kn).…”

“…(2) l~R = crd (3) ]CTn = r~d/T e « e -~/RT (4) have been previously deseribed [9]. The constants K, h, and Rare respectively Boltzmann's constant, Planck's constant, and the gas constant.…”

“…Such considerations into the inactivation of viruses by either heat or ionizing radiation prompted a previous study into the inactivation of viruses by combined heat and ionizing radiation treatment [9]. For appropriate ehoiccs of terapcraturc and radiation dose rate, it was found that viruses are inactivated in a syrmrgistic manner when exposed to a combined heat and ionizing radiation environment.…”

Some general regularities of synergistic interaction of hyperthermia with various physical and chemical inactivating agents

“…This pattern was observed independently of the agent (ionizing radiation, UV light, ultrasound, and zinc sulphate) and the cell line (yeast or bacterial cells) used in this investigation. Noteworthy is the fact that such a dependence of the synergistic e ect on the temperature under which the exposure occurred was also obtained for the combined action of ionizing radiation and heat on bacteriophage 18 , bacterial spores Bacillus subtilis var. niger 19 , as well as for cultured mammalian cells subjected to the simultaneous treatment of hyperthermia with some chemical inactivating agents 20 .…”