Feline sarcoma virus in vitro infection of human cells. Influence of chemical carcinogens on focus formation.

Human fibroblast cells treated with benzo[alpha]pyrene (BP), aflatoxin B1 (AFB1) or N-acetoxy-2-fluorenylacetamide (A-AAF) inhibited Snyder-Theilen feline sarcoma virus (ST-FeSV) focus formation. Inhibition of focus formation resulting from chemical treatment was not related to cytotoxic concentrations of chemicals in that little or not effect on cells surviving treatment was observed. Maximum inhibition of focus formation occurred with BP when the cells were treated before infection. By contrast, maximum inhibition of focus formation occurred with A-AAF and AFB1 when the cells were treated after virus infection. Inhibition of focus formation by BP and AFB1 was eliminated when virus infected cells were treated 48-96 h post-infection. While no infectious virus was detected in either chemical treated or untreated ST-FeSV virus infected cultures, comparable levels of virus-directed RNA dependent DNA polymerase enzyme assay (RDDP) activity were found in both treated and untreated cultures. The data show that the inhibitory effect on focus formation is chemically mediated while the inhibition of virus synthesis is not.