Project description:IL-15 has been implicated as a key regulator of T and NK cell homeostasis in multiple systems; however, its specific role in maintaining peripheral T and NK cell populations relative to other γ-chain (γc) cytokines has not been fully defined in primates. In this article, we address this question by determining the effect of IL-15 inhibition with a rhesusized anti-IL-15 mAb on T and NK cell dynamics in rhesus macaques. Strikingly, anti-IL-15 treatment resulted in rapid depletion of NK cells and both CD4(+) and CD8(+) effector memory T cells (TEM) in blood and tissues, with little to no effect on naive or central memory T cells. Importantly, whereas depletion of NK cells was nearly complete and maintained as long as anti-IL-15 treatment was given, TEM depletion was countered by the onset of massive TEM proliferation, which almost completely restored circulating TEM numbers. Tissue TEM, however, remained significantly reduced, and most TEM maintained very high turnover throughout anti-IL-15 treatment. In the presence of IL-15 inhibition, TEM became increasingly more sensitive to IL-7 stimulation in vivo, and transcriptional analysis of TEM in IL-15-inhibited monkeys revealed engagement of the JAK/STAT signaling pathway, suggesting alternative γc cytokine signaling may support TEM homeostasis in the absence of IL-15. Thus, IL-15 plays a major role in peripheral maintenance of NK cells and TEM However, whereas most NK cell populations collapse in the absence of IL-15, TEM can be maintained in the face of IL-15 inhibition by the activity of other homeostatic regulators, most likely IL-7.
Project description:Analysis of the effect of anti-IL-15 monoclonal antibody treatment on T cell and NK cell homeostasis in rhesus macaques. The hypothesis tested in the present study was that repeated administrations of a rhesusized anti-IL-15 monoclonal antibody would block IL-15 activity in vivo and result in changes to T and/or NK cell population dynamics that would reflect physiologic IL-15 function. The results provide important information on the specific role IL-15 plays in effector memory T cell and NK cell homeostasis, noting that effector memory T cells but not NK cells can be maintained in the absence of IL-15 signaling by the activity of other cytokines. Sort-purified CD8+ and CD4+ TCM from PBMC, before and after treatment with IgG1 Ab and anti-IL15 Ab
Project description:Analysis of the effect of anti-IL-15 monoclonal antibody treatment on T cell and NK cell homeostasis in rhesus macaques. The hypothesis tested in the present study was that repeated administrations of a rhesusized anti-IL-15 monoclonal antibody would block IL-15 activity in vivo and result in changes to T and/or NK cell population dynamics that would reflect physiologic IL-15 function. The results provide important information on the specific role IL-15 plays in effector memory T cell and NK cell homeostasis, noting that effector memory T cells but not NK cells can be maintained in the absence of IL-15 signaling by the activity of other cytokines. Sort-purified CD8+ TEM from PBMC, before and after treatment with IgG1 Ab and anti-IL15 Ab
Project description:Analysis of the effect of anti-IL-15 monoclonal antibody treatment on T cell and NK cell homeostasis in rhesus macaques. The hypothesis tested in the present study was that repeated administrations of a rhesusized anti-IL-15 monoclonal antibody would block IL-15 activity in vivo and result in changes to T and/or NK cell population dynamics that would reflect physiologic IL-15 function. The results provide important information on the specific role IL-15 plays in effector memory T cell and NK cell homeostasis, noting that effector memory T cells but not NK cells can be maintained in the absence of IL-15 signaling by the activity of other cytokines.
Project description:Analysis of the effect of anti-IL-15 monoclonal antibody treatment on T cell and NK cell homeostasis in rhesus macaques. The hypothesis tested in the present study was that repeated administrations of a rhesusized anti-IL-15 monoclonal antibody would block IL-15 activity in vivo and result in changes to T and/or NK cell population dynamics that would reflect physiologic IL-15 function. The results provide important information on the specific role IL-15 plays in effector memory T cell and NK cell homeostasis, noting that effector memory T cells but not NK cells can be maintained in the absence of IL-15 signaling by the activity of other cytokines.
Project description:Aging is associated with gradual deterioration of adaptive immune function, a hallmark of which is the profound loss of naive T cells (TN) associated with decline in thymic output and export of new cells into the peripheral T cell pool. Because the lymphotropic cytokine IL-7 plays crucial roles in both development of TN in the thymus and TN homeostasis in the periphery, we sought to determine the extent to which therapeutic administration of IL-7 could reverse TN deficiency in aging rhesus macaques (RM), either by enhancement of the demonstrably reduced thymopoiesis or by peripheral TN expansion. Our results indicate that treatment of both adult (8-15 y) and old (>20 y) RM with recombinant simian IL-7 (rsIL-7) results in only transient increases in peripheral CD4(+) and CD8(+) TN numbers with no long-term benefit, even with repeated therapy. This transient effect was due to peripheral TN expansion and not enhanced thymic function, and appeared to be limited by induction of IL-7 nonresponsiveness. However, rsIL-7 therapy had a more promising effect on the central memory T cell (TCM) population (both CD4(+) and CD8(+)) in adult and old RM, doubling the numbers of these cells in circulation and maintaining this larger population long term. IL-7 therapy did not reduce TCR diversity of the memory T cell compartment, suggesting that rsIL-7-induced expansion was symmetrical. Thus, although rsIL-7 failed to counter age-associated TN loss, the ability of this therapy to expand clonotypically diverse CD4(+) and CD8(+) TCM populations might potentially improve adaptive immune responsiveness in the elderly.
Project description:Natural killer (NK) cells have traditionally been considered nonspecific components of innate immunity, but recent studies have shown features of antigen-specific memory in mouse NK cells. However, it has remained unclear whether this phenomenon also exists in primates. We found that splenic and hepatic NK cells from SHIV(SF162P3)-infected and SIV(mac251)-infected macaques specifically lysed Gag- and Env-pulsed dendritic cells in an NKG2-dependent fashion, in contrast to NK cells from uninfected macaques. Moreover, splenic and hepatic NK cells from Ad26-vaccinated macaques efficiently lysed antigen-matched but not antigen-mismatched targets 5 years after vaccination. These data demonstrate that robust, durable, antigen-specific NK cell memory can be induced in primates after both infection and vaccination, and this finding could be important for the development of vaccines against HIV-1 and other pathogens.
Project description:The common γ-chain cytokine interleukin-15 (IL-15) plays a significant role in regulating innate and adaptive lymphocyte homeostasis and can stimulate anti-tumor activity of leukocytes. We have previously shown that the circulating IL-15 in the plasma is the heterodimeric form (hetIL-15), produced upon co-expression of IL-15 and IL-15 Receptor alpha (IL-15Rα) polypeptides in the same cell, heterodimerization of the two chains and secretion. We investigated the pharmacokinetic and pharmacodynamic profile and toxicity of purified human hetIL-15 cytokine upon injection in rhesus macaques. We compared the effects of repeated hetIL-15 administration during a two-week dosing cycle, using different subcutaneous dosing schemata, i.e. fixed doses of 0.5, 5 and 50 µg/kg or a doubling step-dose scheme ranging from 2 to 64 µg/kg. Following a fixed-dose regimen, dose-dependent peak plasma IL-15 levels decreased significantly between the first and last injection. The trough plasma IL-15 levels measured at 48 h after injections were significantly higher after the first dose, compared to subsequent doses. In contrast, following the step-dose regimen, the systemic exposure increased by more than 1 log between the first injection given at 2 µg/kg and the last injection given at 64 µg/kg, and the trough levels were comparable after each injection. Blood lymphocyte cell count, proliferation, and plasma IL-18 levels peaked at day 8 when hetIL-15 was provided at fixed doses, and at the end of the cycle following a step-dose regimen, suggesting that sustained expansion of target cells requires increasing doses of cytokine. Macaques treated with a 50 µg/kg dose showed moderate and transient toxicity, including fever, signs of capillary leak syndrome and renal dysfunction. In contrast, these effects were mild or absent using the step-dose regimen. The results provide a new method of optimal administration of this homeostatic cytokine and may have applications for the delivery of other cytokines.