Pi3 Kinase Inhibition Promotes Tolerogenic Cd8 T Cell Function In Lung Transplant Recipients

Purpose: Lung transplant (LTx) recipients with significant cigarette smoke (CS) exposure histories continue to have poorer long-term outcomes. We utilized a systems biology approach to analyze a novel murine model of allogeneic LTx into CS exposed recipients. Our model system mapped the clinical scenario and through in-silico modeling, we sought to identify therapeutic targets that could modulate post-Tx outcomes in the CS exposed patient population. Methods and Results: C57Bl/6 mice were either chronically exposed to CS, or room air (NS) prior to receiving a LTx from non-smoke exposed Balb/cage matched controls. Lungs were harvested at 7 days post-LTx upon which histological, nanostring mRNA immune profiling, and flow cytometry assays were performed. We demonstrate that acute rejection is exacerbated in CS recipients as compared to NS controls (Figure 1). Principle component analysis of nanostring data revealed significant differences IL17A, CTLA4, IL6, and IL4 pathways in CS vs NS. In-silico modeling predicted PI3K pathway inhibitor LY294002 (LY) could reverse this exacerbated rejection phenotype. LY294002 therapy restored the CS recipient to a rejection profile in keeping with that seen in NS recipients (Figure 1). The nanostring analysis suggested a significant role for CD8+ T cells in these responses. Given this, we then reconstituted untreated CD8+ cells into CD8 KO mice prior to LTx. This experiment replicated our observed rejection patterns, thus implicating the CD8+ population as a key regulator of CS-related alloimmunity (Figure 2). Flow cytometry further revealed significant alterations in splenic CD8 central memory (CM) versus effector memory (EM) ratios, with EM predominating in CS mice pre-LTx, as compared to NS. Treatment with LY restored the CM:EM ratio in CS samples, both in-vitro and in-vivo. We then expanded CS and NS CM CD8+ T cells in vitro and reconstituted CD8 KO mice prior to LTx with these CM CD8+ T cells. At 7 days post-LTx, rejection was ameliorated in the CS CM CD8+ group versus non-reconstituted controls and was similar to the NS CM CD8+ group (Figure 3). Conclusion: Pre-transplant CS exposure, particularly in COPD and IPF patients, pre-disposes to poorer post-Tx outcomes. Using a novel LTx system and in-silico modeling we have identified PI3K inhibition as a novel therapeutic approach predicted to be efficacious in CS exposed LTx recipients. The mechanism is at least in part mediated through a preferential skewing of CD8+ T cells towards a central memory phenotype, which appears to have a protective effect in LTx of CS-exposed recipients.