Oncogenic activity of the BK type of human papova virus in inbred rat strains

The oncogenicity of the human polyomavirus BK (BKV) was tested in newborn inbred rats. It was found that the tumor rate was negatively correlated with the levels of T antibody 3 months after inoculation and the frequency of animals with detectable T antibodies 1.5 months after inoculation. By contrast, no influence of viral HI titers on the tumor rates was found. Thymectomy of animals resulted in most experiments in increased tumor rates. Inoculation with BKV of animals later than 24 hours after birth yielded a decrease of tumor rates. The results obtained suggest that T antibody titers present at a critical time after inoculation are associated with low oncogenicity of BKV. The oncogenicity of BKV was comparatively tested in rat strains possessing the allele "l" or the allele "a", respectively. The oncogenicity was significantly higher in rats with the allele "l" than in rats with the allele "a". Rats with the allele "l" showed lower T antibody response than rats with the allele "a". These differences could be explained by the finding that cells of "a" origin showed in vitro a higher percentage of T antigen bearing cells than did cells of a strain possessing the allele "l". In comparison to previous results obtained with BKV inoculated outbred WISTAR rats, the oncogenicity of comparable BKV doses in inbred rats was generally higher and the latency period of tumor manifestation shortened.