The AIO.3 monoclonal antibody reacts with mouse IL-15. IL-15 is a pro-inflammatory cytokine that is produced mainly by dendritic cells, epithelial cells, fibroblasts, and monocytes. IL-15 plays important roles in the immune response and shares many functions with IL-2. IL-15 has been shown to stimulate the proliferation of activated T cells, NK cells, and B cells, and induce antibody production by B cells stimulated with anti-IgM or CD40L. In addition, IL-15 promotes the development of dendritic cells and induces the production of proinflammatory cytokines from macrophages. IL-15 has also been shown to play a role in several inflammatory disorders, including rheumatoid arthritis, psoriasis and pulmonary inflammatory diseases. Emerging data suggest that there is a beneficial effect of IL-15 neutralization in models of psoriasis and diabetes. The AIO.3 antibody has been shown to neutralize the bioactivity of IL-15 in vitro and in vivo.

INVIVOMAB ANTI-MOUSE IL-15

Li, H. Y., et al. (2017). “The Tumor Microenvironment Regulates Sensitivity of Murine Lung Tumors to PD-1/PD-L1 Antibody Blockade.” Cancer Immunol Res 5(9): 767-777. PubMed

Immune checkpoint inhibitors targeting the interaction between programmed cell death-1 (PD-1) and its ligand PD-L1 induce tumor regression in a subset of non-small cell lung cancer patients. However, clinical response rates are less than 25%. Evaluation of combinations of immunotherapy with existing therapies requires appropriate preclinical animal models. In this study, murine lung cancer cells (CMT167 and LLC) were implanted either orthotopically in the lung or subcutaneously in syngeneic mice, and response to anti-PD-1/PD-L1 therapy was determined. Anti-PD-1/PD-L1 therapy inhibited CMT167 orthotopic lung tumors by 95%. The same treatments inhibited CMT167 subcutaneous tumors by only 30% and LLC orthotopic lung tumors by 35%. CMT167 subcutaneous tumors had more Foxp3(+) CD4(+) T cells and fewer PD-1(+) CD4(+) T cells compared with CMT167 orthotopic tumors. Flow cytometric analysis also demonstrated increased abundance of PD-L1(high) cells in the tumor microenvironment in CMT167 tumor-bearing lungs compared with CMT167 subcutaneous tumors or LLC tumor-bearing lungs. Silencing PD-L1 expression in CMT167 cells resulted in smaller orthotopic tumors that remained sensitive to anti-PD-L1 therapy, whereas implantation of CMT167 cells into PD-L1(-) mice blocked orthotopic tumor growth, indicating a role for PD-L1 in both the cancer cell and the microenvironment. These findings indicate that the response of cancer cells to immunotherapy will be determined by both intrinsic properties of the cancer cells and specific interactions with the microenvironment. Experimental models that accurately recapitulate the lung tumor microenvironment are useful for evaluation of immunotherapeutic agents. Cancer Immunol Res; 5(9); 767-77. (c)2017 AACR.

Gil-Cruz, C., et al. (2016). “Fibroblastic reticular cells regulate intestinal inflammation via IL-15-mediated control of group 1 ILCs.” Nat Immunol 17(12): 1388-1396. PubMed

Fibroblastic reticular cells (FRCs) of secondary lymphoid organs form distinct niches for interaction with hematopoietic cells. We found here that production of the cytokine IL-15 by FRCs was essential for the maintenance of group 1 innate lymphoid cells (ILCs) in Peyer’s patches and mesenteric lymph nodes. Moreover, FRC-specific ablation of the innate immunological sensing adaptor MyD88 unleashed IL-15 production by FRCs during infection with an enteropathogenic virus, which led to hyperactivation of group 1 ILCs and substantially altered the differentiation of helper T cells. Accelerated clearance of virus by group 1 ILCs precipitated severe intestinal inflammatory disease with commensal dysbiosis, loss of intestinal barrier function and diminished resistance to colonization. In sum, FRCs act as an ‘on-demand’ immunological ‘rheostat’ by restraining activation of group 1 ILCs and thereby preventing immunopathological damage in the intestine.

Iborra, S., et al. (2016). “Optimal Generation of Tissue-Resident but Not Circulating Memory T Cells during Viral Infection Requires Crosspriming by DNGR-1(+) Dendritic Cells.” Immunity 45(4): 847-860. PubMed

Despite the crucial role of tissue-resident memory T (Trm) cells in protective immunity, their priming remains poorly understood. Here, we have shown differential priming requirements for Trm versus circulating memory CD8(+) T cells. In vaccinia cutaneous-infected mice, DNGR-1-mediated crosspresentation was required for optimal Trm cell priming but not for their skin differentiation or for circulating memory T cell generation. DNGR-1(+) dendritic cells (DCs) promoted T-bet transcription-factor induction and retention of CD8(+) T cells in the lymph nodes (LNs). Inhibition of LN egress enhanced Trm cell generation, whereas genetic or antibody blockade of DNGR-1 or specific signals provided during priming by DNGR-1(+) DCs, such as interleukin-12 (IL-12), IL-15, or CD24, impaired Trm cell priming. DNGR-1 also regulated Trm cell generation during influenza infection. Moreover, protective immunity depended on optimal Trm cell induction by DNGR-1(+) DCs. Our results reveal specific priming requirements for CD8(+) Trm cells during viral infection and vaccination.

Hannani, D., et al. (2015). “Anticancer immunotherapy by CTLA-4 blockade: obligatory contribution of IL-2 receptors and negative prognostic impact of soluble CD25.” Cell Res 25(2): 208-224. PubMed

The cytotoxic T lymphocyte antigen-4 (CTLA-4)-blocking antibody ipilimumab induces immune-mediated long-term control of metastatic melanoma in a fraction of patients. Although ipilimumab undoubtedly exerts its therapeutic effects via immunostimulation, thus far clinically useful, immunologically relevant biomarkers that predict treatment efficiency have been elusive. Here, we show that neutralization of IL-2 or blocking the alpha and beta subunits of the IL-2 receptor (CD25 and CD122, respectively) abolished the antitumor effects and the accompanying improvement of the ratio of intratumoral T effector versus regulatory cells (Tregs), which were otherwise induced by CTLA-4 blockade in preclinical mouse models. CTLA-4 blockade led to the reduction of a suppressive CD4(+) T cell subset expressing Lag3, ICOS, IL-10 and Egr2 with a concomitant rise in IL-2-producing effector cells that lost FoxP3 expression and accumulated in regressing tumors. While recombinant IL-2 improved the therapeutic efficacy of CTLA-4 blockade, the decoy IL-2 receptor alpha (IL-2Ralpha, sCD25) inhibited the anticancer effects of CTLA-4 blockade. In 262 metastatic melanoma patients receiving ipilimumab, baseline serum concentrations of sCD25 represented an independent indicator of overall survival, with high levels predicting resistance to therapy. Altogether, these results unravel a role for IL-2 and IL-2 receptors in the anticancer activity of CTLA-4 blockade. Importantly, our study provides the first immunologically relevant biomarker, namely elevated serum sCD25, that predicts resistance to CTLA-4 blockade in patients with melanoma.

Wang, J., et al. (2014). “Respiratory influenza virus infection induces intestinal immune injury via microbiota-mediated Th17 cell-dependent inflammation.” J Exp Med 211(12): 2397-2410. PubMed

Influenza in humans is often accompanied by gastroenteritis-like symptoms such as diarrhea, but the underlying mechanism is not yet understood. We explored the occurrence of gastroenteritis-like symptoms using a mouse model of respiratory influenza infection. We found that respiratory influenza infection caused intestinal injury when lung injury occurred, which was not due to direct intestinal viral infection. Influenza infection altered the intestinal microbiota composition, which was mediated by IFN-gamma produced by lung-derived CCR9(+)CD4(+) T cells recruited into the small intestine. Th17 cells markedly increased in the small intestine after PR8 infection, and neutralizing IL-17A reduced intestinal injury. Moreover, antibiotic depletion of intestinal microbiota reduced IL-17A production and attenuated influenza-caused intestinal injury. Further study showed that the alteration of intestinal microbiota significantly stimulated IL-15 production from intestinal epithelial cells, which subsequently promoted Th17 cell polarization in the small intestine in situ. Thus, our findings provide new insights into an undescribed mechanism by which respiratory influenza infection causes intestinal disease.

Verbist, K. C., et al. (2012). “IL-15 participates in the respiratory innate immune response to influenza virus infection.” PLoS One 7(5): e37539. PubMed

Following influenza infection, natural killer (NK) cells function as interim effectors by suppressing viral replication until CD8 T cells are activated, proliferate, and are mobilized within the respiratory tract. Thus, NK cells are an important first line of defense against influenza virus. Here, in a murine model of influenza, we show that virally-induced IL-15 facilitates the trafficking of NK cells into the lung airways. Blocking IL-15 delays NK cell entry to the site of infection and results in a disregulated control of early viral replication. By the same principle, viral control by NK cells can be therapeutically enhanced via intranasal administration of exogenous IL-15 in the early days post influenza infection. In addition to controlling early viral replication, this IL-15-induced mobilization of NK cells to the lung airways has important downstream consequences on adaptive responses. Primarily, depletion of responding NK1.1+ NK cells is associated with reduced immigration of influenza-specific CD8 T cells to the site of infection. Together this work suggests that local deposits of IL-15 in the lung airways regulate the coordinated innate and adaptive immune responses to influenza infection and may represent an important point of immune intervention.