There have been reports of patients with lymphotropic retrovirus (HTLV-I)-associated diseases who did not have antibodies to structural proteins of the virus (eg, reference 1). Most patients with mycosis fungoides, who are serologically negative have HTLV-I Tax sequence in their blood and skininfiltrating lymphocytes. 2, 3 Although patients with mycosis fungoides lack antibodies to the structural proteins of the virus, such as env and gag, more than 80% have antibodies to Tax protein when tested by western blot. 4 This condition of negative standard HTLV-I antibody tests, and positivity for Tax antibody and Tax sequence in lymphocytes, previously seen only in individuals with disease, was found in six of eight healthy relatives of our patients with mycosis fungoides tested to date. Because Tax is the transforming/transactivating component of the virus, it seemed important to find out whether there are healthy individuals who carry HTLV-I Tax, but who could, nevertheless, become blood donors because they are negative for antibodies to HTLV-I/II by standard serological tests used in US blood-transfusion centres since 1988. 5 Specimens were collected from 100 non-consecutive, randomly selected, volunteer blood donors at the New York University Medical Center Blood Bank. All donors were white and none had risk factors which would have excluded them from donating blood. Mononuclear leucocytes were isolated by Ficoll/Hypaque gradient centrifugation and their extracts subjected to PCR and southern blot analysis with primers SK43/44 and probe SK45. 2 Each specimen was processed in a different area and at a different time to preclude contamination. Plasma samples were tested for antibodies to recombinant Tax by ELISA and western-blot assays as reported for plasmas obtained from patients with mycosis fungoides. 4 Known HTLV-positive and HTLV-negative cell and plasma samples were run side by side with the volunteer donors’ specimens. Unexpectedly, mononuclear cells of 11/100 donors proved to harbour the Tax sequence and eight of these also had antibodies to Tax protein. All donors who had antibodies to the Tax protein by western blot, had Tax sequences in their cells—92/100 individuals tested were Tax-antibody negative, and no individual lacking the Tax sequence had antibodies to Tax protein (0/89).

Accurately to establish the prevalence of a Tax-only condition in our non-endemic region’s population will require study of a larger cohort. The significance of Tax-only in terms of pathogenicity and transmissibility and its implications regarding the safety of the blood supply need to be further investigated.