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Expression of Exogenous Cytokine in Patient-derived Xenografts via Injection with a Cytokine-transduced Stromal Cell Line
Published on: May 10, 2017
Implications for gene therapy-limiting expression of IL-2R gamma c delineate differences in signaling thresholds
Selinda J Orr1, Stephen Roessler, Laura Quigley
1Cancer and Inflammation Program, National Cancer Institute-Frederick, Frederick, MD 21702, USA.
Abstract:
X-linked SCID patients are deficient in functional IL-2Rgamma(c) leading to the loss of IL-2/IL-4/IL-7/IL-9/IL-15/IL-21 signaling and a lack of NK and mature T cells. Patients treated with IL-2Rgamma(c) gene therapy have T cells develop; however, their NK cell numbers remain low, suggesting antiviral responses may be compromised. Similarly, IL-2Rgamma(c)(-/-) mice reconstituted with IL-2Rgamma(c) developed few NK cells, and reconstituted T cells exhibited defective proliferative responses suggesting incomplete recovery of IL-2Rgamma(c) signaling. Given the shift toward self-inactivating long terminal repeats with weaker promoters to control the risk of leukemia, we assessed NK and T cell numbers and function in IL-2Rgamma(c)(-/-) mice reconstituted with limiting amounts of IL-2Rgamma(c). Reconstitution resulted in lower IL-2/-15-mediated STAT5 phosphorylation and proliferation in NK and T cells. However, TCR costimulation restored cytokine-driven T cell proliferation to wild-type levels. Vector modifications that improved IL-2Rgamma(c) levels increased cytokine-induced STAT5 phosphorylation in both populations and increased NK cell proliferation demonstrating that IL-2Rgamma(c) levels are limiting. In addition, although the half-lives of both NK and T cells expressing intermediate levels of IL-2Rgamma(c) are reduced compared with wild-type cells, the reduction in NK cell half-live is much more severe than in T cells. Collectively, these data indicate different IL-2Rgamma(c) signaling thresholds for lymphocyte development and proliferation making functional monitoring imperative during gene therapy. Further, our findings suggest that IL-2Rgamma(c) reconstituted T cells may persist more efficiently than NK cells due to compensation for suboptimal IL-2Rgamma(c) signaling by the TCR.
Insights
Gene therapy for X-linked SCID using IL-2Rgamma(c) gene transfer improves T cell recovery but NK cell numbers remain low. Different IL-2Rgamma(c) signaling thresholds impact lymphocyte function, necessitating monitoring during therapy.
Area of Science:
- Immunology
- Gene Therapy
- Cell Biology
Background:
- X-linked severe combined immunodeficiency (X-SCID) results from a deficiency in the common gamma chain (IL-2Rgamma(c)), crucial for multiple cytokine signaling pathways.
- This deficiency leads to a lack of functional Natural Killer (NK) and mature T cells, severely compromising immune responses.
- Current gene therapy approaches using IL-2Rgamma(c) gene transfer show partial success, with T cell development but persistently low NK cell numbers.
Purpose of the Study:
- To investigate the impact of limiting IL-2Rgamma(c) expression on NK and T cell development and function in a mouse model of X-SCID.
- To assess the role of vector design and IL-2Rgamma(c) levels in determining lymphocyte reconstitution and function post-gene therapy.
- To elucidate the differential signaling thresholds of IL-2Rgamma(c) for T and NK cell recovery and persistence.
Main Methods:
- Utilized IL-2Rgamma(c)(-/-) mice reconstituted with varying amounts of IL-2Rgamma(c) via gene therapy vectors.
- Assessed STAT5 phosphorylation and proliferation in NK and T cells in response to cytokines (IL-2, IL-15) and T cell receptor (TCR) costimulation.
- Quantified NK and T cell numbers and determined their half-lives to evaluate persistence.
Main Results:
- Reconstitution with limiting IL-2Rgamma(c) resulted in reduced STAT5 phosphorylation and proliferation in both NK and T cells.
- TCR costimulation rescued cytokine-driven T cell proliferation, while NK cell proliferation remained impaired.
- Vector modifications enhancing IL-2Rgamma(c) levels improved STAT5 phosphorylation and NK cell proliferation, indicating IL-2Rgamma(c) levels are limiting.
- NK cells exhibited a more severe reduction in half-life compared to T cells under intermediate IL-2Rgamma(c) expression.
Conclusions:
- Distinct IL-2Rgamma(c) signaling thresholds govern lymphocyte development and proliferation, highlighting the need for functional monitoring in gene therapy.
- T cells may persist better than NK cells due to TCR-mediated compensation for suboptimal IL-2Rgamma(c) signaling.
- Optimizing IL-2Rgamma(c) expression levels is critical for achieving comprehensive immune reconstitution, particularly for NK cell function.
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