ENHANCEMENT AND INHIBITION OF AVIAN SARCOMA VIRUSES BY POLYCATIONS AND POLYANIONS

Polycations enhance the infectivity of avian sarcoma viruses for chick embryo fibroblast cultures up to 80-fold. The enhancement is restricted to members of avian tumor virus subgroups B, C, and D and to RSV(O). Subgroup A viruses are either unaffected or inhibited by polycations. The polycation-mediated enhancement is at least in part due to an increased adsorption rate of virus to cell, but may also involve penetration. Viral growth rates are not influenced by cationic polymers. Polyanions reduce the infectivity of avian sarcoma viruses and are also able to neutralize the virus-enhancing activity of polycations. An exception is dextran sulfate which causes virus inhibition only at low concentrations (less than 4 μg/ml), but enhances viral infectivity at higher concentrations. Extracts from normal or leukosis virus-infected chick embryo fibroblasts also enhance focus formation by certain avian sarcoma viruses. The characteristics of this enhancement are similar to that mediated by polycations. © 1969.