Intracellular neutralization of SV40 tumor antigens following microinjection of specific antibody

Abstract

Summary Hamster sera raised against SV40 tumors contain antibodies which recognize the SV40 large and small T antigens. IgG from such sera and from preimmune hamster serum has been purified and injected into green monkey kidney cells and murine fibroblasts infected with SV40. The results of these maneuvers were marked and selective immune IgG inhibition of SV40 DNA synthesis in the former case and a substantial reduction in virus-induced abortive transformation in the latter. The immune IgG fraction used in these studies lacked detectable antibody against any of the late viral proteins. Furthermore, it was inhibitory to both of these processes when injected 6 hr after virus infection. Thus the observed inhibition does not result from a block to viral penetration and uncoating. Injection of immune IgG did not significantly reduce the viability of SV40-infected murine fibroblasts. Moreover, the cloning efficiency in methylcellulose of an isogenic cell line transformed by murine sarcoma virus was not specifically inhibited by immune IgG injection. In addition, when parallel cultures of a rat fibroblast line infected by either polyoma or SV40 were injected with immune or preimmune IgG, only the immune IgG-injected, SV40-infected culture sustained a reduction in subsequent cloning efficiency in methylcellulose. In keeping with this result, the immune IgG used had no detectable affinity for the large, middle or small polyoma T antigens. Thus we conclude that injection of antibody from anti-SV40 tumor sera into SV40-infected cells results in a significant blockade of elements of large and/or small T antigen function.