Albuquerque, A. S.Cortesão, C. S.Foxall, R. B.Victorino, R. M.Sousa, A. E.2015-06-172015-06-172007J Immunol 2007; 178:3252-32590022-1767http://www.jimmunol.org/content/178/5/3252.longhttp://dx.doi.org/10.4049/jimmunol.178.5.3252http://hdl.handle.net/10451/18296Copyright © 2007 by The American Association of Immunologists, Inc.IL-7 is a nonredundant cytokine for T cell homeostasis. Circulating IL-7 levels increase in lymphopenic clinical settings, including HIV-1 infection. HIV-2 infection is considered a “natural” model of attenuated HIV disease given its much slower rate of CD4 decline than HIV-1 and limited impact on the survival of the majority of infected adults. We compared untreated HIV-1- and HIV-2-infected patients and found that the HIV-2 cohort demonstrated a delayed increase in IL-7 levels during the progressive depletion of circulating CD4 T cells as well as a dissociation between the acquisition of markers of T cell effector differentiation and the loss of IL-7Rα expression. This comparison of two persistent infections associated with progressive CD4 depletion and immune activation demonstrates that a better prognosis is not necessarily associated with higher levels of IL-7. Moreover, the delayed increase in IL-7 coupled with sustained expression of IL-7Rα suggests a maximization of available resources in HIV-2. The observation that increased IL-7 levels early in HIV-1 infection were unable to reduce the rate of CD4 loss and the impaired expression of the IL-7Rα irrespective of the state of cell differentiation raises concerns regarding the use of IL-7 therapy in HIV-1 infection.engjournal article