The use of ceiling temperature and reactivation in the isolation of pox virus hybrids

Abstract

A simple method for the isolation of pox virus hybrids on the C.A.M. has been described. One parental virus was used as a heat-inactivated suspension. The other parent was used in the active state, but at a temperature higher than its ceiling temperature. Under these conditions the inactive parent was reactivated so that pocks resulted only from the cells infected with both parental viruses. Many of these pocks were unlike those of either parent. Such lesions were found to contain a high proportion of hybrids. In these experiments, alastrim was crossed with rabbit pox and variola major with cowpox.The term ‘heat-tethered’ has been used to describe virus whose intracellular cycle of development has been arrested by incubation at too high a temperature. Heat-tethered virus has interesting properties and two of these have been described. When the temperature is lowered, heat-tethered virus will start to grow again. Its reactivating potential has been mentioned above. A more detailed account of the properties of heat-tethered virus is being prepared.