Age effects on the host and tissue response to Rous sarcoma virus (RSV)

Summary

The age factor was found to exert significant effects on the response of embryos to Rous sarcoma virus (RSV) and on tumor formation in chick embryo tissue exposed to this virus and subsequently transplanted to the rat brain. Tumors and hemorrhagic blebs developed with high frequency in 7- and 8 day old embryos inoculated intra-allantoically or into the yolk sac. Older embryos showed fewer lesions. This decrease in frequency of response was not seen when the virus was administered intravenously. These observations were interpreted as signifying an alteration in extra-embryonic tissues. On the other hand, the failure of the large majority of three day old embryos to respond to the virusin ovo and the low frequency of transformations of three day old tissues used in the heterologous transplantation experiments indicated a low capacity of tumor formation on the part of the immature tissues. In the transplantation experiments, eight and nine day old embryo tissues showed the maximum degree of malignant transformation. Somewhat fewer transformations were obtained in transplants of tissues from 15 day old embryos. Tissues of hatched chicks responded with a very low frequency of conversions.