Sepsis leads to lasting changes in phenotype and function of memory CD8 T cells

The global health burden due to sepsis and the associated cytokine storm is substantial. While early intervention has improved survival during the cytokine storm, those that survive can enter a state of chronic immunoparalysis defined by transient lymphopenia and functional deficits of surviving cells. Memory CD8 T cells provide rapid cytolysis and cytokine production following re-encounter with their cognate antigen to promote long-term immunity, and CD8 T cell impairment due to sepsis can pre-dispose individuals to re-infection. While the acute influence of sepsis on memory CD8 T cells has been characterized, if and to what extent pre-existing memory CD8 T cells recover remains unknown. Here, we observed that central memory CD8 T cells (TCM) from septic patients proliferate more than those from healthy individuals. Utilizing LCMV immune mice and a CLP model to induce sepsis, we demonstrated that TCM proliferation is associated with numerical recovery of pathogen-specific memory CD8 T cells following sepsis-induced lymphopenia. This increased proliferation leads to changes in composition of memory CD8 T cell compartment and altered tissue localization. Further, memory CD8 T cells from sepsis survivors have an altered transcriptional profile and chromatin accessibility indicating long-lasting T cell intrinsic changes. The sepsis-induced changes in the composition of the memory CD8 T cell pool and transcriptional landscape culminated in altered T cell function and reduced capacity to control L. monocytogenes infection. Thus, sepsis leads to long-term alterations in memory CD8 T cell phenotype, protective function and localization potentially changing host capacity to respond to re-infection.

Abstract CT164: Pharmacological ascorbate enhances platinum-based chemotherapy responses in metastatic non-small cell lung cancer (NSCLC): A phase II clinical trial

PURPOSE: First line treatment with platinum-based chemotherapy with or without immunotherapy improves survival in metastatic non-small cell lung cancer (NSCLC). Preclinical studies suggest that pharmacological ascorbate (P-AscH-) enhances tumor response to platinum therapy. Hence, we conducted a single-arm phase II study to evaluate the efficacy of P-AscH- in combination with platinum-doublet chemotherapy in patients with advanced stage NSCLC (NCT02420314). METHODS: Chemotherapy naïve advanced stage NSCLC patients with an ECOG PS of 0-2 were enrolled to receive 4-cycles of carboplatin (AUC 6) and paclitaxel (200 mg/m2) every 3 weeks (wks). Ascorbate (75 g) infusions were given twice a wk for 12-wks. The primary endpoint was to assess tumor objective response per RECIST v1.1. The trial was conducted as an optimal Simon two-stage design. After initial therapy, patients could receive maintenance or consolidation treatment. Secondary endpoints were to evaluate tolerability, progression-free survival (PFS) and overall survival (OS). Serum cytokines and chemokines were measured at baseline, C2d1, and C4d21± 7d. RESULTS: Forty subjects were enrolled. The study met its primary endpoint with 38 efficacy evaluable subjects. The objective response rate was 34.2%. All were confirmed partial responses (cPR). Disease control rate was 84.2% (stable disease + cPR). Median duration of follow up was 11.7 months (mo), mPFS was 5.7 mo (95% CI:4.2-6.7), and mOS was 12.5 mo (95% CI:7.5-21.4). Treatment-related adverse events (TRAE) included one grade 5 (neutropenic fever) and five grade 4 (cytopenia) events. These events were not attributed to P-AscH-. Common (≥5%) grade 3 TRAE included transient hypertension (27.5%), lymphopenia (22.5%), fatigue (7.5%), anemia (7.5%) and hypokalemia (5%). Cytokine and chemokines data suggest that protocol regimen elicited an immune response with multiple distinct cytokine signatures. Immunophenotyping of peripheral blood mononuclear cells (n=7) demonstrated a mean fold increase in effector CD8 T cells of 4.9 in patients with PFS ≥ 6 mo compare to 1.6 in patients with PFS < 6 mo. Assessments of serum iron profile and somatic alterations in KRAS, KEAP1, NFE2L2 and STK11 genes are underway. CONCLUSIONS: This phase II trial met the primary objective of improving the tumor response rate in advanced stage NSCLC by adding P-AscH- to platinum-based chemotherapy. P-AscH- appears to alter the host immune response. These promising findings warrant further investigation.

Citation Format: Muhammad Furqan, Taher Abu-Hejleh, Kellie L. Bodeker, Laura M. Pietrok, Stacey M. Hartwig, Mikaela M. Tremblay, Micaela G. Fosdick, Jon Houtman, Steven Varga, Casey F. Pulliam, Michael Petronek, Melissa A. Fath, Sarah L. Mott, Aaron D. Bossler, Andrew M. Bellizzi, Jun Zhang, Hariharasudan Mani, Varun Monga, Brian J. Smith, Joseph Cullen, Brett A. Wagner, Garry R. Buettner, John M. Buatti, Douglas R. Spitz, Bryan G. Allen. Pharmacological ascorbate enhances platinum-based chemotherapy responses in metastatic non-small cell lung cancer (NSCLC): A phase II clinical trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT164.

Suppression of human T cell activation by derivatives of glycerol monolaurate

Glycerol monolaurate (GML), a naturally occurring monoglyceride, is widely used commercially for its antimicrobial properties. Interestingly, several studies have shown that GML not only has antimicrobial properties but is also an anti-inflammatory agent. GML inhibits peripheral blood mononuclear cell proliferation and inhibits T cell receptor (TCR)-induced signaling events. In this study, we perform an extensive structure activity relationship analysis to investigate the structural components of GML necessary for its suppression of human T cell activation. Human T cells were treated with analogs of GML, differing in acyl chain length, head group, linkage of acyl chain, and number of laurate groups. Treated cells were then tested for changes in membrane dynamics, LAT clustering, calcium signaling, and cytokine production. We found that an acyl chain with 12-14 carbons, a polar head group, an ester linkage, and a single laurate group at any position are all necessary for GML to inhibit protein clustering, calcium signaling, and cytokine production. Removing the glycerol head group or replacing the ester linkage with a nitrogen prevented derivative-mediated inhibition of protein cluster formation and calcium signaling, while still inhibiting TCR-induced cytokine production. These findings expand our current understanding of the mechanisms of action of GML and the of GML needed to function as a novel immunosuppressant.

Polymicrobial sepsis influences NK-cell-mediated immunity by diminishing NK-cell-intrinsic receptor-mediated effector responses to viral ligands or infections

The sepsis-induced cytokine storm leads to severe lymphopenia and reduced effector capacity of remaining/surviving cells. This results in a prolonged state of immunoparalysis, that contributes to enhanced morbidity/mortality of sepsis survivors upon secondary infection. The impact of sepsis on several lymphoid subsets has been characterized, yet its impact on NK-cells remains underappreciated–despite their critical role in controlling infection(s). Here, we observed numerical loss of NK-cells in multiple tissues after cecal-ligation-and-puncture (CLP)-induced sepsis. To elucidate the sepsis-induced lesions in surviving NK-cells, transcriptional profiles were evaluated and indicated changes consistent with impaired effector functionality. A corresponding deficit in NK-cell capacity to produce effector molecules following secondary infection and/or cytokine stimulation (IL-12,IL-18) further suggested a sepsis-induced NK-cell intrinsic impairment. To specifically probe NK-cell receptor-mediated function, the activating Ly49H receptor, that recognizes the murine cytomegalovirus (MCMV) m157 protein, served as a model receptor. Although relative expression of Ly49H receptor did not change, the number of Ly49H⁺ NK-cells in CLP hosts was reduced leading to impaired in vivo cytotoxicity and the capacity of NK-cells (on per-cell basis) to perform Ly49H-mediated degranulation, killing, and effector molecule production in vitro was also severely reduced. Mechanistically, Ly49H adaptor protein (DAP12) activation and clustering, assessed by TIRF microscopy, was compromised. This was further associated with diminished AKT phosphorylation and capacity to flux calcium following receptor stimulation. Importantly, DAP12 overexpression in NK-cells restored Ly49H/D receptors-mediated effector functions in CLP hosts. Finally, as a consequence of sepsis-dependent numerical and functional lesions in Ly49H⁺ NK-cells, host capacity to control MCMV infection was significantly impaired. Importantly, IL-2 complex (IL-2c) therapy after CLP improved numbers but not a function of NK-cells leading to enhanced immunity to MCMV challenge. Thus, the sepsis-induced immunoparalysis state includes numerical and NK-cell-intrinsic functional impairments, an instructive notion for future studies aimed in restoring NK-cell immunity in sepsis survivors.

Sepsis is an exaggerated host response to infection that can initially lead to significant morbidity/mortality and a long-lasting state of immunoparalysis in sepsis survivors. Sepsis-induced immunoparalysis functionally impairs numerous lymphocyte populations, including NK-cells. However, the scope and underlying mechanisms of NK-cell impairment and the consequences for NK-cell-mediated pathogen control remain underappreciated. NK-cells contribute to early host control of pathogens through a balance of activating and inhibitory receptors, and alterations in the number and capacity of NK-cells to exert receptor-mediated immunity can lead to dramatic impairment in host control of infection. The present study defines sepsis-induced numerical and cell-intrinsic functional impairments in NK-cell response to cytokine stimulation and receptor signaling that contribute to impaired host capacity to mount NK-cell-mediated effector responses and provide protection to bacterial and/or viral pathogens. Impairments in receptor signaling were due to reduced expression of adaptor protein DAP12. Importantly, the diminished ability of NK-cells from CLP hosts to provide anti-viral (MCMV) immunity is partially restored by IL-2 complex (IL-2c) therapy, which increased the number, but not function, of protective Ly49H⁺ NK-cells. Thus, these findings define sepsis-induced changes of the NK-cell compartment and provide insight into potential therapeutic interventions aimed at resolving sepsis-induced immunoparalysis in sepsis survivors.

Glycerol monolaurate induces filopodia formation by disrupting the association between LAT and SLP-76 microclusters

Glycerol monolaurate (GML) is a monoglyceride with potent antimicrobial properties that suppresses T cell receptor (TCR)-induced signaling and T cell effector function. Actin rearrangement is needed for the interaction of T cells with antigen-presenting cells and for migration to sites of infection. Because of the critical role actin rearrangement plays in T cell effector function, we analyzed the effect of GML on the rearrangement of the actin cytoskeleton after TCR activation. We found that GML-treated human T cells were less adherent than untreated T cells and did not form actin ring structures but instead developed numerous inappropriate actin-mediated filopodia. The formation of these filopodia was not due to disruption of TCR-proximal regulators of actin or microtubule polymerization. Instead, total internal reflection fluorescence microscopy demonstrated mislocalization of actin nucleation protein Arp2 microclusters, but not those containing the adaptor proteins SLP-76 and WASp, or the actin nucleation protein ARPC3, which are necessary for TCR-induced actin rearrangement. Additionally, SLP-76 microclusters colocalized with WASp and WAVE microclusters but not with LAT. Together, our data suggest that GML alters actin cytoskeletal rearrangements and identify diverse functions for GML as a T cell-suppressive agent.