Seroprevalence of human T-cell lymphotropic virus type 1 among homosexual men in the United States

HTLV-1 Transmission and HIV Pre-exposure Prophylaxis: A Scoping Review

HIV pre-exposure prophylaxis (HIV-PrEP) is effective in reducing the likelihood of HIV acquisition in HIV-negative people at high risk of exposure. Guidelines recommend testing for sexually transmitted infections (STIs) before starting, and periodically on PrEP, including bacterial infections, HIV, hepatitis C virus, and, for those who are non-immune, hepatitis B virus. Diagnosed infections can be promptly treated to reduce onward transmission. HTLV-1 is not mentioned; however, it is predominantly sexually transmitted, causes adult T-cell leukaemia/lymphoma (ATL) or myelopathy in 10% of those infected, and is associated with an increased risk of death in those without any classically HTLV-associated condition. The 2021 WHO Technical Report on HTLV-1 called for the strengthening of global public health measures against its spread. In this scoping review, we, therefore, (1) discuss the epidemiological context of HIV-PrEP and HTLV-1 transmission; (2) present current knowledge of antiretrovirals in relation to HTLV-1 transmission prevention, including nucleos(t)ide reverse transcriptase inhibitors (NRTIs) and integrase strand transfer inhibitors (INSTIs); and (3) identify knowledge gaps where data are urgently required to inform global public health measures to protect HIV-PrEP users from HTLV-1 acquisition. We suggest that systematic seroprevalence studies among PrEP-using groups, including men who have sex with men (MSM), people who inject drugs (PWIDs), and female sex workers (FSWs), are needed. Further data are required to evaluate antiretroviral efficacy in preventing HTLV-1 transmission from in vitro studies, animal models, and clinical cohorts. PrEP delivery programmes should consider prioritizing the long-acting injectable INSTI, cabotegravir, in HTLV-1 endemic settings.

Human T cell leukemia virus (HTLV-I/II) serodiagnostic testing: disparate results among a cohort of intravenous drug users

Three hundred and forty-six sera collected over a 2-year period from 154 San Francisco IV drug users were subjected to HTLV-I/II RIPA, Western blot (WB), Du Pont ELISA, and p24 radioimmunoassay (RIA). Tests were performed at separate sites and code not broken until study end. RIPA-positive and -negative controls consisted of Japanese adult T cell leukemia patients, healthy blood donors, and non-IV drug-using HIV-positive men. RIPA identified HTLV-I/II-positive sera not identified by the other tests. Positive RIPAs were noted in 43% of negative ELISAs (n = 279), 34% of negative WBs (n = 243), and 40% of negative RIAs (n = 270). Seventy-two sera were negative by all 3 assays, but were RIPA positive. All sera positive by RIA (n = 76) and WB (n = 67), and 66 of 67 by ELISA, were positive by RIPA. Thirty-five of 36 indeterminate WBs were RIPA positive. Seven samples indeterminate by RIPA were negative by WB and RIA; one of seven was positive by ELISA. In all instances, samples negative by RIPA (n = 154) were ELISA, p24 RIA, and WB negative or indeterminate. We conclude that when studying HTLV-I/II-endemic cohorts, screening ELISA or RIA followed by confirmatory WB or RIPA only of seropositive samples may result in a substantial number of undetected cases. Additional studies focusing on performance characteristics of serodiagnostic tests are needed to ensure accurate inferences are made in assessing HTLV-I/II prevalence rates among high-risk groups. The RIPA may be a uniquely sensitive assay to detect HTLV-I/II gene-encoded products.

Seroprevalence of HTLV-1 and HTLV-2 among intravenous drug users and persons in clinics for sexually transmitted diseases

Background. The human T-cell lymphotropic virus Type I (HTLV-I) is associated with adult T-cell leukemia and myelopathy, whereas HTLV-II infection has uncertain clinical consequences. We assessed the seroprevalence of these retroviruses among intravenous drug users and among patients seen at clinics for sexually transmitted diseases (STD clinics).

METHODS

We used serum samples that were collected in eight cities in 1988 and 1989 during surveys of human immunodeficiency virus infection among intravenous drug users entering treatment and persons seen in STD clinics. The serum samples were tested for antibodies to HTLV, and positive specimens were tested further by a synthetic peptide-based enzyme-linked immunosorbent assay to differentiate between HTLV-I and HTLV-II.

RESULTS

Among 3217 intravenous drug users in 29-drug-treatment centers, the median seroprevalence rates of HTLV varied widely according to city (range, 0.4 percent in Atlanta to 17.6 percent in Los Angeles). Seroprevalence increased sharply with age, to 32 percent in persons over 44 years of age. HTLV infection was more common among blacks (15.5 percent) and Hispanics (10.7 percent) than among whites (4.1 percent), and it was strongly associated with a history of heroin injection (P less than or equal to 0.001). Among 5264 patients in 24 STD clinics, the median rates of HTLV infection were much lower (range, 0.1 percent in Atlanta and Newark to 2.0 percent in Los Angeles). Again, this infection was more common among intravenous drug users (7.6 percent) than among non-drug users (0.7 percent). Eighty-four percent of the seropositive samples from drug-treatment centers and 69 percent of those from STD clinics were due to HTLV-II infection (P = 0.03).

CONCLUSIONS

HTLV infections are common among intravenous drug users and are primarily caused by HTLV-II. Among patients seen at STD clinics, HTLV is strongly associated with intravenous drug use, but the retrovirus is also prevalent among non-drug users.

A registry-based case-control study of mycosis fungoides

The etiology of mycosis fungoides is unknown. Two possible causes (an unknown retrovirus with increased prevalence among never-married men, and prior malignancies) were investigated to determine whether they are associated with the incidence of mycosis fungoides. During 1973 to 1986, 953 case patients with mycosis fungoides or Sézary syndrome were registered by the Surveillance, Epidemiology, and End Results program. Each was matched by 5-year age group, sex, ethnicity, and geographic area to four control subjects, one each with cancer of the pancreas, brain, and stomach, and non-Hodgkin's lymphoma. For never-versus ever-married men, none of the relative risks differed significantly from those for women (odd ratios, .8-1.0). For any prior malignancy, the relative risks (and 95% confidence intervals) were 1.3 (.9-2.0), 1.2 (.8-1.8), 1.0 (.7-1.5), and 1.1 (.7-1.6). These data reject the previous relative risk estimate of 3.3 with greater than 99% power, and are consistent with only a small risk, if any, attributable to prior malignancy.

Examination of HTLV-I ELISA-positive leukemia/lymphoma patients by western blotting gave mostly negative or indeterminate reaction

We used enzyme-linked immunosorbant assay (ELISA) and Western blotting, with "purified" human T-cell leukemia virus I (HTLV-I), to test for HTLV-I antibodies in 2583 plasma samples from 1053 leukemia/lymphoma patients treated at Roswell Park Memorial Institute, mostly between 1972 and 1984, and in 110 sera samples from normal healthy persons. The results demonstrate that ELISA and Western blot assay have limitations for HTLV-I antibody detection in an adult T-cell leukemia/lymphoma (ATL) nonendemic population. This conclusion is based on the many false reactives obtained by ELISA, and weak and indeterminate reaction (mostly p19 band) on Western blotting. All moderate to strongly HTLV-I ELISA-positive samples tested were negative for human immunodeficiency virus (HIV) antibodies. Although 6/27 mycosis fungoides (MF) patients tested gave mostly a weak reaction on HTLV-I ELISA, 3/6 MF patients gave multiple bands (p19, p31, p36, gp46) on Western blotting and three samples from one patient gave the same p31, p36, and gp46 bands. This may suggest involvement of some HTLV-I-related virus in MF. These results also indicate that prevalence of HTLV-I infection in leukemia/lymphoma patients was rare, if it exists at all, since, despite the reactivity of some sera with HTLV-I-suspected antigens, none of the samples satisfy the USPHS criteria for positivity which is based on the detection of antibodies to gag protein p24 and to an env gene product gp46 or gp61/68.

AIDS-related vacuolar myelopathy is not associated with coinfection by human T-lymphotropic virus type I

Assessment of antibodies against human T-lymphotropic virus type I (HTLV-I) by enzyme-linked immunoassay, immunofluorescence, and Western blot was undertaken in patients with pathologically or clinically diagnosed acquired immunodeficiency syndrome-related vacuolar myelopathy to determine whether this retrovirus could be etiologically implicated in this disorder. No serological evidence for HTLV-I was found in the patients with vacuolar myelopathy, though 1 patient with an atypical myelopathy did have antibodies against HTLV-I.

Exposure of patients to human immunodeficiency virus through the transfusion of blood components that test antibody-negative

The risk of transmission of the human immunodeficiency virus to recipients of blood transfusions exists chiefly during the period between the time a donor is infected and the time he or she has a positive blood test for HIV antibodies. Estimating the chance that blood will be donated during this period is an effective way to define the risk of HIV infection from transfusion. Using this approach, and employing data from over 17 million American Red Cross blood donations, we estimate that during 1987 the most likely number of units of blood infected with undetected HIV that were transfused was 131 (range, 67 to 227). For a patient, the odds of contracting HIV infection were 1:153,000 per unit transfused. A patient who received the average transfusion (5.4 units) had odds of 1:28,000. The risk has been decreasing by more than 30 percent a year. We estimate that donor-recruitment practices plus careful education and screening are eliminating 49 of every 50 donors likely to be HIV-positive and that testing is 92 to 97 percent effective, for a combined effectiveness of 99.9 percent. The risk of undetected infectious units can probably be further reduced by transfusing fewer units and units from fewer donors, recruiting more women and fewer men as new donors, and encouraging more frequent donations from donors who have been tested repeatedly.