Neoplasms and haemorrhagic disease induced in adult hamsters with polyoma virus.

FOLLOWING experiments by Gross1 and others, it is generally accepted that oncogenic viruses are especially active when inoculated in new-born or suckling animals. Stewart, Eddy et al.2,3 produced a wide range of malignancies by inoculating polyoma virus in new-born or very young mice, hamsters and rats. One of the possible explanations of the high receptivity of animals during the perinatal age is absence of mature, immunologically competent cells. Accordingly, we tried, as did Defendi and Koprowski4, to protect suckling hamsters against virus action by simultaneous inoculation of homologous, mature lymph node and spleen cells. In our hands this procedure was without effect. Consequently we attempted to verify in a series of experiments whether adult hamsters actually respond to the action of the polyoma virus.