Molecular Epidemiology of HTLV-II among United States Blood Donors and Intravenous Drug Users: An Age–Cohort Effect for HTLV-II RFLP Type a0

Abstract

Molecular subtyping was used to investigate the epidemiology of human T-lymphotropic virus type II (HTLV-II) in the United States. Nested polymerase chain reaction of the HTLV-II long terminal repeat region followed by restriction fragment length polymorphism (RFLP) analysis was performed on HTLV-II seropositive subjects including 97 U.S. blood donors without major risk factors for HTLV-II infection, 53 injection drug users (IDU), and 10 American Indian blood donors. Three new HTLV-II RFLP types were confirmed with DNA sequencing and phylogenetic analysis. HTLV-II RFLP type a0 (Switzer classification) was associated with older age [adjusted odds ratio (OR) 1.06 per year of age, 95% confidence interval (CI) 1.02–1.09] and with Black (OR 5.24, 95% CI 1.90–14.47) and White (OR 4.43, 95% CI 1.67–11.75) race/ ethnicity. These data are consistent with an age–cohort effect for HTLV-II RFLP type a0 among older White and Black IDU and blood donors. This finding could be explained by an epidemic of non-a0 HTLV-II RFLP types among younger persons of Hispanic and other race/ethnicity, superimposed upon endemic HTLV-II RFLP type a0 among older Black and White persons.