Infectiousness of the Shope papilloma virus after growth in embryonic, neoplastic, and cancerous states of domestic rabbit skin.

Transfer of the Shope virus from the cottontail to the domestic rabbit results in the formation of papillomas indistinguishable from those of the original host, but, in the majority of cases, such passage is associated with a loss of infectivity. The presence of virus in the domestic papillomas can be demonstrated by immunological technics, and loss of pathogenicity is referred to as masking. It has been suggested that masking of the virus is a function of the body fluids of the domestic rabbit, but studies undertaken in this laboratory indicate, rather, that the process is independent of body fluids and related to a variation in the constitution of the epithelial cells of the epidermis (2, 3, 4, 8). The investigation to be reported was undertaken in an attempt to determine whether the ability to mask the virus was limited to the adult state of domestic rabbit epidermis or shared by embryonic and neoplastic states.