Evidence for the existence of a thermolabile element in adenovirus type 5 that plays a role during an early stage of infection.

In an attempt to learn the molecular mechanism behind the initial steps (before genome expression) of adenovirus infection, the effect of temperature treatment of adenovirus type 5 particles on their infectivity was studied. It was found that adenovirus type 5 could be inactivated by temperature treatment at between 43 and 44 degrees C. Both biochemical and biophysical examination of adenovirus particles failed to disclose any significant changes after exposure to temperatures up to 45 degrees C. Further, viral particles treated with the same temperature range retained their ability to attach to cell surface receptors and to penetrate the plasma membrane. Application of a temperature pulse of 44 degrees C to adenovirus-infected HeLa cells indicates that the infection can be inhibited by exposure of infected cells to a brief temperature pulse of 44 degrees C between 10 and 50 min postadsorption with a mid-point of 30 min postadsorption. In addition, electron microscopic examination of HeLa cells following a temperature pulse of 44 degrees C suggests that there is a failure to accumulate viral particles at the perinuclear region. These findings support the hypothesis that adenovirus contains a thermolabile element which plays a crucial role during an early stage of infection. Possible correlation of this element with the adenovirus endogenous protein kinase is also examined and discussed.