Antibodies in human sera reactive against an internal structural protein of human T-cell lymphoma virus

Although retroviruses (RNA tumour viruses) have been implicated in the causation of naturally occurring leukaemias and lymphomas of animals ¹, it is not yet clear whether they are involved in the human versions of these malignant diseases, particularly because of the difficulty in isolating viruses truly ascribable to human origin^2,3. However, a novel type C retrovirus (called HTLV_CR) has been isolated in our laboratory from T cells (fresh and in culture) from a lymph node biopsy of a patient (C.R.) with cutaneous T-cell lymphoma (mycosis fungoides)⁴ and a very similar virus (HTLV_MB) from the peripheral blood T cells of another patient (M.B.) with cutaneous T-cell leukaemia (Sézary syndrome, see accompanying report⁵). The nucleic acid sequence ⁶, the reverse transcriptase⁷ and the major internal structural protein (p24)⁸ of HTLV_CR are not significantly related to any of the known retroviruses; nucleic acid sequences and p24 protein of HTLV_MB have been recognized in fresh and cultured cells ⁵. We now describe the results of a limited survey of the occurrence, in patients with T-cell malignancies (and among normal people), of antibodies against HTLV_CR proteins. We find that antibodies against p24 are present in human sera (including those of patient C.R. and his wife), and that these are specifically directed at HTLV_CR proteins and not at cell-specific determinants - in other words, the immunological reactions are not those reported in human sera^9-11 against animal virus glycoproteins which, lacking virus specificity, are directed against the carbohydrate residues of the glycoprotein^12,13. The antibodies against HTLV are thus the first evidence for a specific immune response in humans against a retrovirus.