Adult Syrian hamster kidney cells were transfected with a mixture of p
lasmids containing human papillomavirus type 16 (HPV16) E6/E7 open rea
ding frames (ORFs), activated Ha-ras gene and neomycin resistence gene
. From these cultures two lines were isolated which were oncogenic for
newborn and 5-day-old but not for 3-week-old hamsters. Sublines oncog
enic for 3-7-week-old hamsters were derived from tumours formed in ani
mals inoculated within 5 days of birth. The cells contained HPV16 DNA
in an integrated form and HPV16 transcripts. The transcript patterns i
n low and high oncogenicity sublines were different. Very few tumour-b
earing animals possessed antibodies reactive with E6- and E7-derived s
ynthetic peptides. On the other hand, a majority of these animals gave
a positive reaction in the lymphoproliferation assay with either E6 a
nd E7 peptides or extracts from the transformed cells.