Table 4.
Major scientific accomplishments of the REDS Human T-Lymphotropic Virus (HTLV) cohort study.
| HTLV Research Questions | Findings | References |
|---|---|---|
| HTLV associated myelopathy (HAM) | Novel finding that HAM is associated with HTLV-II infection in addition to HTLV-I, albeit with lower penetrance and somewhat milder presentation. | 88–90 |
| Broncho-pulmonary infection | Higher incidence of bronchitis and pneumonia among HTLV-II subjects, but pulmonary function is not impaired and both T-cell (delayed hypersensitivity skin testing) and B-cell (antibody production in response to pneumococcal vaccination) function is intact. | 91–96 |
| HTLV proviral load (PVL) | Mean proviral load was 1,905 copies/106 PBMCs for HTLV-I and 398 copies/106 PBMCs for HTLV-II, and varied by HTLV-II subtype, route of infection and sex. Both HTLV-I and –II proviral load vary widely between individuals, but are stable at the same “setpoint” in each individual over a median of 10.4 years of follow-up. | 97–99 |
| Sexual transmission | HTLV-I and –II incidence of 0.6 per 100 person- years (95% CI, 0.2–1.6) within serodiscordant heterosexual couples. Transmission associated with higher proviral loads in the infecting partner; no difference in transmission between HTLV-I and HTLV-II, nor between male-to-female versus female-to-male directions. | 100,101 |
| Hematology outcomes | HTLV-II infected subjects have chronic increases in adjusted lymphocyte counts (+7%), mean corpuscular volume and adjusted platelet counts. Sex, race, smoking, and alcohol consumption all had significant effects on blood counts. | 102–104 |
| APH-2 (antisense protein of HTLV-II) | APH-2 mRNA was detected in PBMC from 4 of 15 HTLV-II-infected blood donors, and could explain the lymphocytosis frequently observed in HTLV-II patients. | 105 |
| HTLV-II molecular epidemiology | HTLV-II subtype a0 was independently associated with age over 30 years and with Black race/ethnicity. HTLV-II RFLP subtypes b4 and b5 were significantly more common among American Indian and Other race/ethnicity and at the Oklahoma City blood center. | 106,107 |