Reexamination of human T cell lymphotropic virus (HTLV-IyII) prevalence (mycosis fungoidesyinjection drug usersyTaxyHTLV proviral sequenceyHTLV antibodies)

In the United States, blood donors are being screened for infection with human T cell lymphotropic viruses I and II (HTLV-IyII) by serologic means, which detect antibodies to the structural proteins of these viruses. Because patients with mycosis fungoides (MF) usually do not have such antibodies even though their cells harbor HTLV-I Tax andyor pol proviral sequences, it was questioned whether the prevalence of HTLV infection among healthy blood donors may also be underestimated by current means of testing. To examine this possibility, a study on specimens of relatives of mycosis fungoides patients (MFR) was begun. In addition, to collect data more expeditiously, a cohort of former injection drug users (IDUs) was tested by routine serologic methods, as well as by PCRySouthern blot analysis for Tax, pol, and gag proviral sequences and Western blot analysis for antibodies to the Tax gene product. To date, 6y8 MFRs and 42y81 (51.8%) of HIV-negative IDUs proved to be positive for HTLV, whereas routine serology identified none of the MFR and only 18y81 (22.2%) of the IDUs. Among the latter test subjects, the incidence of HTLV-I also proved to be 10 times higher than expected. Therefore, it is likely that among healthy blood donors infection with HTLV-IyII is more prevalent than is currently assumed. Since Tax is the transforming sequence of HTLV-IyII, testing for Tax sequences and antibodies to its gene product may be desirable in blood transfusion and tissue donor facilities. The first human retrovirus, human T cell lymphotropic virus type I (HTLV-I), was discovered more than 15 years ago (1, 2). Since that time numerous investigators have studied its pathogenicity, epidemiology, and molecular biology (for reviews see refs. 3–5). The etiologic role of HTLV-I in adult T cell leukemiaylymphoma and tropical spastic paraparesisyHTLVI-associated myelopathy has been well established. The vast majority of patients with these diseases have antibodies to the structural proteins of the virus (6). While in the United States the prevalence of infection with HTLV-I appears to be quite low, blood used for transfusion is nevertheless being tested routinely by enzyme-linked immunosorbent (ELISA) andyor Western blot assays (7, 8). On this basis, the prevalence of HTLV-I infection among Americans without obvious risk factors, such as origin from an endemic region or intravenous drug abuse has been estimated to be about 0.016% (9). It may be as high as 0.1% in some locations (10). Our suspicion that infection with HTLV-I among Caucasian Americans may be higher than determined by routinely used methods was aroused by studies on the cutaneous T cell lymphoma mycosis fungoides (MF) (11, 12). MF patients usually do not have antibodies to the structural proteins of the virus, but harbor proviral sequences of HTLV-I in their peripheral blood mononuclear cells (PBMCs) and skin (11–14). A high percentage of these patients were also shown to have antibodies to HTLV-I Tax (15), an antigen not included in commercially available HTLV serologic test kits. This led us to begin a study of healthy relatives of MF patients who were serologically negative for antibodies to HTLV-I when their specimens were tested at a major blood transfusion center. Of the first eight individuals tested, six proved to have Tax sequences in their PBMCs and antibodies to the Tax antigen by Western blot analysis. Since family studies of a relatively rare disease manifested mostly in middle-aged and elderly individuals are time consuming, a more expeditious approach was chosen to determine whether currently used serologic methods are adequate to establish the true prevalence of HTLV infection among blood donors. Accordingly, a cohort of individuals among whom the prevalence of HTLV infection was known to be high, i.e., former injection drug users (IDUs), was selected for study. Matched sera and PBMCs obtained from 81 HIV-negative methadone clinic attendees were tested by routine serologic methods, as well as for Tax, pol and gag proviral sequences by PCRy Southern blot analysis and antibodies to viral structural proteins as well as to the Tax gene product. Routine serology proved 18y81 (22.2%) of these specimens to be positive for antibodies to HTLV, which concurred with results obtained by other investigators. On the other hand, 39y81 (48.1%) were found positive for HTLV proviral sequences by biomolecular means and 42 (51.8%) were positive when both serologic tests and PCRySouthern blot analyses were used. Together, the results of these studies suggest that the prevalence of infection with HTLV, particularly when efforts are made to detect Tax sequences, may be considerably higher than is currently believed. MATERIALS AND METHODS Study Subjects and Specimens. The eight healthy individuals who were relatives of Tax-positive MF patients consisted of (i) the wives of MF patients JH and LDeV, (ii) the mother of MF patient AD, (iii) the daughter of male MF patient JB, and (iv) the husband, two daughters, and one son of MF patient ZA. The MF patients were Caucasian Americans as reported elsewhere (12). Neither they nor their relatives had any recognized risk factors. The cells and sera were processed as described (12). The IDU specimens consisted of paired sera and PBMCs obtained from 81 former IDUs enrolled in methadone maintenance programs of Bellevue Hospital, Beth Israel, and The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked ‘‘advertisement’’ in accordance with 18 U.S.C. §1734 solely to indicate this fact. © 1997 by The National Academy of Sciences 0027-8424y97y946403-5$2.00y0 Abbreviations: HTLV-I, human T cell lymphotropic virus type I; MF, mycosis fungoides; MFR, relatives of MF patients; PBMCs, peripheral blood mononuclear cells; IDUs, injection drug users. †To whom reprint requests should be addressed at: Department of Medicine, New York University Medical Center, Room TH-445, 550 First Avenue, New York, NY 10016.