Delayed Progression To AIDS In HTLV-II/HIV-1 Coinfected Intravenous Drug Users

Background: Human T-cell lymphotropic virus type II (HTLV-II) has spread among intravenous drug users (IDUs), many of who are coinfected with HIV-1. We have screened 3574 Italian IDUs for HIV-1, HTLV-I and HTLV-II from 1986 to the present. Methods: For examination of AIDS progression, two distinct groups of IDUs, one of 437 HIV-1-monoinfected and another of 96 HTLV-II/HIV-1-coinfected subjects, matched by date of entry, CD4 counts and history of drug abuse, were monitored for an average period of 13 years. Results: The frequency of HTLV-II infection was 6.7% among 2371 HIV-1-positive and 1.1% among 1203 HIV-1-negative subjects (P < 0.0001). The data obtained at the end of 13 years monitoring period showed that HTLV-II /HIV-1-coinfection was associated with older age (P < 0.0001), higher CD4 (P < 0.0001) and CD8 (P < 0.001) counts, compared to HIV-1-monoinfected IDUs. The number of long-term nonprogressors for AIDS (LTNP) was significantly higher (P < 0.0001) among coinfected (13/96,13.5%) than HIV monoinfected patients (5/437, 1.1%). The distribution of HTLV-II proviral values for the coinfected patients showed that the LTNPs have a significantly lower number (P < 0.02) of undetectable values. Conclusions: Evidence presented in this study that a significant proportion of coinfected IDUs mantain elevated CD4 counts points to a protective role of HTLV-II infection against AIDS progression.