(Science: molecular biology) proteins coded by viral genes that are expressed early in the replication cycle of papovaviruses such as sV40 and polyoma. Essential for normal viral replication, they are also expressed in nonpermissive cells transformed by these viruses.
Originally detected as tumour antigens by immunofluorescence with antisera from tumour bearing animals. SV40 has two, large T and small t, polyoma has three, large, middle and small. Appear to be collectively responsible for transformation by these viruses.
Antigens that can be found in the presence of a cancer inducing virus (an oncogene).