Thermal inactivation studies of a coronavirus, transmissible gastroenteritis virus

The thermolability of transmissible gastroenteritis virus (TGEV) was studied between 31 and 55 degrees C using two different strains. The loss of infectivity followed first order kinetics except at the highest temperature. The values of the thermodynamic parameters indicated that the mechanisms involved above and below 45 degrees C are clearly distinct. The rates of inactivation were greater at alkaline than at neutral pH, yet the name of the reaction appeared unchanged. Using four independent stocks of mutagenized virus, we failed to select thermal-resistant mutants by survivor selection at 38 degrees C. In contrast, thermal-resistant mutants were consistently obtained at 54 degrees C. However, the latter did not show any increased stability at 38 degrees C, confirming the fact that a different inactivation process takes place at high and at physiological temperatures.