Helminthic infection down-regulates type 1 immune responses in human T cell lymphotropic virus type 1 (HTLV-1) carriers and is more prevalent in HTLV-1 carriers than in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis.

Human T cell lymphotropic virus type 1 (HTLV-1) infection is associated with an exacerbated type 1 immune response and secretion of high levels of proinflammatory cytokines. In contrast, helminthic infection induces a type 2 immune response. In the present study, the cytokine profile in HTLV-1 carriers coinfected with helminths (Strongyloides stercoralis and/or Schistosoma mansoni) was compared with that in HTLV-1 carriers not coinfected with helminths. Levels of interferon (IFN)- gamma were higher in HTLV-1 carriers not coinfected with helminths than in HTLV-1 carriers coinfected with helminths (P<.05). The overall frequency of IFN- gamma -expressing CD8+ and CD4+ cells was decreased in HTLV-1 carriers coinfected with helminths (P<.05). The percentage of interleukin (IL)-5- and IL-10-expressing T cells in HTLV-1 carriers coinfected with helminths was higher than that in HTLV-1 carriers not coinfected with helminths (P<.05). Moreover, we found that the prevalence of helminthic infection was 7-fold higher in HTLV-1 carriers than in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (P<.05). These data show that helminthic infection decreases activation of type 1 cells, which may influence the clinical outcome of HTLV-1 infection.