The relationship of the papilloma virus to a carcinoma derived from the virus-induced rabbit

carcinoma derived from the virus-induced rabbit papillontá has been the subject of numerous stud iss. Early work indicated that the carcinoma (V2) did not contain papilloma virus demonstrable by the usual infectivity tests. Nevertheless, there was reason to believe that papilloma antigen was pres cut in the V2 carcinoma cell, since the host rabbits developed specific papilloma complement-fixing antibodies during the course of intramuscular pas sage of the carcinoma (7). However, some time be tween the fifth and eighth years of continuous pas sage, a change occurred in the antigenic make-up of the V2 carcinoma so that host rabbits no longer developed papilloma antibodies. Despite the ap parent loss of papilloma antigen, the V2 carcinoma has retained all its original characteristics (6). Re cent studies of seven other papilloma-derived car cinomas have produced significant new findings (9). When these tumors were established in baby domestic rabbits, it was discovered that the car cinomas elicited little or no papilloma antibody; but small amounts of papilloma virus were demon strated in three of six tumors. Later, when the same carcinomas were transferred to adult do mestic rabbits, papilloma virus could no longer be demonstrated in extracts of the carcinomas, al though the rabbits bearing the tumors did develop specific papilloma complement-fixing antibodies in their sera. It has long been recognized that it was difficult, or often impossible, to demonstrate papilloma virus in the papifiomas of domestic rabbits, al though large amounts of virus usually could be iso lat@ed from cottontail rabbit papillomas (10). Therefore, it seemed probable that the papilloma virus, if present in V2 carcinomas, would be diffi cult to demonstrate when the tumor was growing in the domestic rabbit. Therefore, from time to time, unsuccessful attempts have been made to es tablish the V2 tumor in cottontail rabbits with the