Background: Human T cell lymphotropic virus type 2 (HTLV-2) infection is not rare among injection drug users with human immunodeficiency virus (HIV) infection and may exert a protective role in the progression of HIV disease.

Methods: Immunological and virological parameters were compared in HIV-HTLV-2-coinfected patients and a control group of HIV-monoinfected subjects. All individuals were antiretroviral therapy naive. HIV-specific CD8+ T cell levels were measured using an interferon-gamma assay in response to 125 optimally defined HIV peptides divided into 5 pools. Immune activation was evaluated by measuring levels of CD38 in different CD4+ and CD8+ T cell subsets. In a subgroup of patients, the production of CCL4 in parallel with interferon-gamma was assessed in response to Gag peptides.

Results: Lower plasma HIV-RNA levels were found in HIV-HTLV-2-coinfected patients than in HIV-monoinfected patients, despite the 2 groups having similar CD4+ T cell counts. Coinfected patients also had significantly lower levels of CD38 expression in total CD8+ T cells and in its naive subset. CD8+ T cell levels specific for each pool of peptides were similar in both groups, but cells mainly contributing to HIV Gag-specific responses in coinfected patients were CCL4 positive and interferon-gamma negative, whereas for HIV-monoinfected subjects, the response was dominated by CCL4-positive and interferon-gamma-positive cells.

Conclusions: HTLV-2 coinfection may exert a protective role on HIV disease progression by lowering HIV replication and immune activation. A predominance of CCL4 single positive HIV-specific CD8+ T cells in HIV-HTLV-2-coinfected patients could explain this effect.