A number of cytokines are secreted during HIV infection that enhances both innate and adaptive\nimmune responses. Interferon-//, IL-12, IL-15 and IL-18 have been found to contribute to the\ndevelopment, maturation, differentiation and function of NK and other immune cells. The levels of\nIFN-//, IL-12, IL-15 and IL-18 were compared in the plasma of 90 HIV-1 infected and 90 HIV-2\ninfected subjects by ELISA or Cytometric Beads Array assays. The HIV-infected subjects were\nstratified according to CD4+ T cell counts into three groups: >500, 200 - 500 and <200 cells/ul,\nwith 30 subjects in each group. Cytokine levels were also determined in the plasma of 50 HIV uninfected\nblood bank donors. Among the cytokines tested, IFN- was found to be significantly increased\nin HIV-2 infected compared to HIV-1 infected subjects at high CD4+ T cell counts (p =\n0.001). The levels of IFN- were seen to differ between the two infections in patients from the\ncategory of medium CD4+ T cell counts: this was significantly increased in HIV-2 infected patients\n(p < 0.001) as well as compared to uninfected controls (p = 0.001). The levels of IFN- were similar\nat all the CD4+ T cell categories except for an increase in HIV-2 infected patients at low CD4+ T cell\ncounts (p = 0.02). The levels of these cytokines were similar in all HIV-1 subjects. Also, the level of\nIL-12p70 was similar between the two infections but significantly higher in HIV-2 at low compared\nto medium CD4+ T cells categories (p = 0.047). Similar to IFN- and IL-12p70, the levels of both\nIL-18 and IL-15 were found to be significantly higher in HIV-2 infected patients compared to HIV-1\nat low CD4+ T cell counts (p < 0.05). These data show that there is variability in the levels of innate\ncytokines at different stages of HIV infection but the finding of increased IFN- in HIV-2 infected asymptomatic subjects is consistent with the high innate NK responses previously noted at this\nstage of infection.
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