Nucleic acid sequences of primate type C viruses in normal and neoplastic human tissues

Abstract

RECENT reports on the isolation of type C viruses from human cells have generated considerable controversy because of the close relationship of the viruses to the type C viruses of subhuman primates^1–5. These findings have been interpreted as evidence for contamination despite the repeated isolation of some type C viruses from separate clinical specimens or from separate frozen primary cell stocks of the same donor^6–9. Our laboratory has described a type C virus which is released from the HEL–12 strain of normal human embryonic lung fibroblasts⁵. The HEL–12 virus is related immunologically to simian sarcoma (woolly monkey fibrosarcoma) virus (SiSV) and the endogenous type C viruses of baboons and domestic cats^9–11. To demonstrate that the HEL–12 virus is not an adventitious contaminant, fresh human tissues were examined for antigenic cross-reactivity with HEL–12 virus antigens. Some patients with myelogenous leukemia contain circulating immunoglobulins which specifically inhibit the reverse transcriptases of HEL–12 virus and primate type C viruses¹². In addition, the glomerular immune complexes in patients with systemic lupus erythematosus contain antigens related to HEL–12 virus proteins¹³. Using the techniques of molecular hybridisation, we demonstrate here that HEL–12 cells contain proviral DNA sequences before antigen expression or spontaneous virus release can be detected. We also present evidence for the existence of nucleic acid sequences homologous to HEL–12 viral RNA in the DNAs from certain cancer patients.