Safety and preliminary efficacy of pembrolizumab following trans-arterial chemoembolization for hepatocellular carcinoma: the PETAL phase Ib study.

BACKGROUND: TACE may prime adaptive immunity and enhance immunotherapy efficacy. PETAL evaluated safety, preliminary activity of TACE plus pembrolizumab and explored mechanisms of efficacy. METHODS: Patients with liver-confined HCC were planned to receive up to 2 rounds of TACE followed by pembrolizumab 200 mg every 21 days commencing 30-days post-TACE until disease progression or unacceptable toxicity for up to 1 year. Primary endpoint was safety, 21-days dose-limiting toxicities (DLT) from pembrolizumab initiation. Secondary endpoints included progression-free survival (PFS) and evaluation of tumour and host determinants of response. RESULTS: Fifteen patients were included in the safety and efficacy population: 73% had non-viral cirrhosis, median age was 72 years. Child-Pugh (CP) class was A in 14 patients. Median tumour size was 4 cm. Ten patients (67%) received pembrolizumab after 1 TACE, 5 patients after 2 (33%). Pembrolizumab yielded no synergistic toxicity nor DLTs post-TACE. Treatment-related adverse events occurred in 93% of patients most commonly skin rash (40%), fatigue and diarrhoea (27%). After a median follow-up of 38.5 months, objective response rate (ORR) 12 weeks post-TACE was 53%. PFS rate at 12 weeks was 93% and median PFS was 8.95 months (95%CI 7.30-NA). Median duration of response was 7.3 months (95%CI: 6.3-8.3). Median OS was 33.5 months (95%CI: 11.6-NA). Dynamic changes in peripheral T-cell subsets, circulating tumour DNA, serum metabolites and in stool bacterial profiles highlight potential mechanisms of action of multi-modal therapy. CONCLUSIONS: TACE plus pembrolizumab was tolerable with no evidence of synergistic toxicity, encouraging further clinical development of immunotherapy alongside TACE.

Prostaglandin E2 controls the metabolic adaptation of T cells to the intestinal microenvironment.

Immune cells must adapt to different environments during the course of an immune response. Here we study the adaptation of CD8+ T cells to the intestinal microenvironment and how this process shapes the establishment of the CD8+ T cell pool. CD8+ T cells progressively remodel their transcriptome and surface phenotype as they enter the gut wall, and downregulate expression of mitochondrial genes. Human and mouse intestinal CD8+ T cells have reduced mitochondrial mass, but maintain a viable energy balance to sustain their function. We find that the intestinal microenvironment is rich in prostaglandin E2 (PGE2), which drives mitochondrial depolarization in CD8+ T cells. Consequently, these cells engage autophagy to clear depolarized mitochondria, and enhance glutathione synthesis to scavenge reactive oxygen species (ROS) that result from mitochondrial depolarization. Impairing PGE2 sensing promotes CD8+ T cell accumulation in the gut, while tampering with autophagy and glutathione negatively impacts the T cell pool. Thus, a PGE2-autophagy-glutathione axis defines the metabolic adaptation of CD8+ T cells to the intestinal microenvironment, to ultimately influence the T cell pool.

Efficient formation and maintenance of humoral and CD4 T-cell immunity targeting the viral capsid in acute-resolving hepatitis E infection.

BACKGROUND & AIMS: CD4 T cells shape the neutralizing antibody (nAb) response and facilitate viral clearance in various infections. Knowledge of their phenotype, specificity and dynamics in hepatitis E virus (HEV) infection is limited. HEV is enterically transmitted as a naked virus (nHEV) but acquires a host-derived quasi-envelope (eHEV) when budding from cells. While nHEV is composed of the open reading frame (ORF)-2-derived capsid, eHEV particles also contain ORF3-derived proteins. We aimed to longitudinally characterize the HEV-specific CD4 T cells targeting ORF1, 2 and 3 and antibodies against nHEV or eHEV in immunocompetent individuals with acute and resolved HEV infection. METHODS: HEV-specific CD4 T cells were analyzed by intracellular cytokine staining after stimulation with in silico-predicted ORF1- and ORF2-derived epitopes and overlapping peptides spanning the ORF3 region. Ex vivo multiparametric characterization of capsid-specific CD4 T cells was performed using customized MHC class II tetramers. Total and neutralizing antibodies targeting nHEV or eHEV particles were determined. RESULTS: HEV-specific CD4 T-cell frequencies and antibody titers are highest in individuals with acute infection and decline in a time-dependent process with an antigen hierarchy. HEV-specific CD4 T cells strongly target the ORF2-derived capsid and ORF3-specific CD4 T cells are hardly detectable. NAbs targeting nHEV are found in high titers while eHEV particles are less efficiently neutralized. Capsid-specific CD4 T cells undergo memory formation and stepwise contraction, accompanied by dynamic phenotypical and transcriptional changes over time. CONCLUSION: The viral capsid is the main target of HEV-specific CD4 T cells and antibodies in acute-resolving infection, correlating with efficient neutralization of nHEV. Capsid-specific immunity rapidly emerges followed by a stepwise contraction several years after infection. IMPACT AND IMPLICATIONS: The interplay of CD4 T cells and neutralizing antibody responses is critical in the host defense against viral infections, yet little is known about their characteristics in hepatitis E virus (HEV) infection. We conducted a longitudinal study of immunocompetent individuals with acute and resolved HEV infection to understand the characteristics of HEV-specific CD4 T cells and neutralizing antibodies targeting different viral proteins and particles. We found that HEV-specific CD4 T cells mainly target capsid-derived epitopes. This correlates with efficient neutralization of naked virions while quasi-enveloped particles are less susceptible to neutralization. As individuals with pre-existing liver disease and immunocompromised individuals are at risk for fulminant or chronic courses of HEV infection, these individuals might benefit from the development of vaccination strategies which require a detailed knowledge of the composition and longevity of HEV-specific CD4 T-cell and antibody immunity.

Baseline neutrophil-lymphocyte ratio and platelet-lymphocyte ratio appear predictive of immune treatment related toxicity in hepatocellular carcinoma.

BACKGROUND: A well-recognized class effect of immune checkpoint inhibitors (ICI) is immune-related adverse events (IrAEs) ranging from low grade toxicities to life-threatening end organ damage requiring permanent discontinuation of ICI. Deaths are reported in < 5% of patients treated with ICI. There are, however, no reliable markers to predict the onset and severity of IrAEs. We tested the association between neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) at baseline with development of clinically significant IrAEs (grade ≥ 2) in hepatocellular carcinoma (HCC) patients treated with ICI. AIM: To test the association between NLR and PLR at baseline with development of clinically significant IrAEs (grade ≥ 2) in HCC patients treated with ICI. METHODS: Data was extracted from an international database from a consortium of 11 tertiary-care referral centers. NLR = absolute neutrophil count/absolute lymphocyte count (ALC) and PLR = platelet count/ALC. Cutoff of 5 was used for NLR and 300 for PLR based on literature. We also tested the association between antibiotic and steroid exposure to IrAEs. RESULTS: Data was collected from 361 patients treated between 2016-2020 across the United States (67%), Asia (14%) and Europe (19%). Most patients received Nivolumab (n = 255, 71%). One hundred sixty-seven (46%) patients developed at least one IrAE, highest grade 1 in 80 (48%), grade ≥ 2 in 87 (52%) patients. In a univariable regression model PLR > 300 was significantly associated with a lower incidence of grade ≥ 2 IrAEs (OR = 0.40; P = 0.044). Similarly, a trend was observed between NLR > 5 and lower incidence of grade ≥ 2 IrAEs (OR = 0.58; P = 0.097). Multivariate analyses confirmed PLR > 300 as an independent predictive marker of grade ≥ 2 IrAEs (OR = 0.26; P = 0.011), in addition to treatment with programmed cell death ligand 1 (PD-1)/cytotoxic T lymphocyte-associated protein-4 (OR = 2.57; P = 0.037) and PD-1/tyrosine kinase inhibitor (OR = 3.39; P = 0.01) combinations. Antibiotic use was not associated with IrAE incidence (OR = 1.02; P = 0.954). Patients treated with steroids had a > 2-fold higher incidence of grade ≥ 2 IrAEs (OR = 2.74; P < 0.001), although 74% were prescribed steroids for the treatment of IrAEs. CONCLUSION: Given that high baseline NLR and PLR are associated with a decreased incidence of IrAEs, lower baseline NLR and PLR may be predictive biomarkers for the appearance of IrAEs in HCC treated with ICI. This finding is in keeping with several studies in solid tumors that have shown that baseline NLR and PLR appear predictive of IrAEs.

Harnessing CD3 diversity to optimize CAR T cells.

Current US Food and Drug Administration-approved chimeric antigen receptor (CAR) T cells harbor the T cell receptor (TCR)-derived ζ chain as an intracellular activation domain in addition to costimulatory domains. The functionality in a CAR format of the other chains of the TCR complex, namely CD3δ, CD3ε and CD3γ, instead of ζ, remains unknown. In the present study, we have systematically engineered new CD3 CARs, each containing only one of the CD3 intracellular domains. We found that CARs containing CD3δ, CD3ε or CD3γ cytoplasmic tails outperformed the conventional ζ CAR T cells in vivo. Transcriptomic and proteomic analysis revealed differences in activation potential, metabolism and stimulation-induced T cell dysfunctionality that mechanistically explain the enhanced anti-tumor performance. Furthermore, dimerization of the CARs improved their overall functionality. Using these CARs as minimalistic and synthetic surrogate TCRs, we have identified the phosphatase SHP-1 as a new interaction partner of CD3δ that binds the CD3δ-ITAM on phosphorylation of its C-terminal tyrosine. SHP-1 attenuates and restrains activation signals and might thus prevent exhaustion and dysfunction. These new insights into T cell activation could promote the rational redesign of synthetic antigen receptors to improve cancer immunotherapy.

Senolytic therapy alleviates physiological human brain aging and COVID-19 neuropathology.

Aging is a major risk factor for neurodegenerative diseases, and coronavirus disease 2019 (COVID-19) is linked to severe neurological manifestations. Senescent cells contribute to brain aging, but the impact of virus-induced senescence on neuropathologies is unknown. Here we show that senescent cells accumulate in aged human brain organoids and that senolytics reduce age-related inflammation and rejuvenate transcriptomic aging clocks. In postmortem brains of patients with severe COVID-19 we observed increased senescent cell accumulation compared with age-matched controls. Exposure of human brain organoids to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induced cellular senescence, and transcriptomic analysis revealed a unique SARS-CoV-2 inflammatory signature. Senolytic treatment of infected brain organoids blocked viral replication and prevented senescence in distinct neuronal populations. In human-ACE2-overexpressing mice, senolytics improved COVID-19 clinical outcomes, promoted dopaminergic neuron survival and alleviated viral and proinflammatory gene expression. Collectively our results demonstrate an important role for cellular senescence in driving brain aging and SARS-CoV-2-induced neuropathology, and a therapeutic benefit of senolytic treatments.

Efficacy and safety of atezolizumab/bevacizumab in patients with HCC after prior systemic therapy: A global, observational study.

BACKGROUND: Since the introduction of the combination treatment of anti-programmed death-ligand 1 antibody atezolizumab and anti-VEGF antibody bevacizumab (AB), median overall survival in HCC has drastically improved. However, evidence on the efficacy and safety of the novel treatment standard in patients with prior exposure to systemic treatment is scarce. The aim of this global, multicenter, observational study was to evaluate the efficacy and safety of AB in patients after previous systemic therapy. METHODS: We screened our global, multicenter, prospectively maintained registry database for patients who received any systemic therapy before AB. The primary end point was overall survival; secondary end points were time-to-progression, progression-free survival, objective response rate, and safety (rate and severity of adverse events). RESULTS: Among 493 patients who received AB for unresectable HCC, 61 patients received prior systemic therapy and were included in this analysis. The median age of the study population was 66 years, with 91.8% males. Predominant risk factors for HCC were viral hepatitis (59%) and alcohol (23%). Overall survival for AB was 16.2 (95% CI, 14.5-17.9) months, time-to-progression and progression-free survival were 4.1 (95% CI, 1.5-6.6) and 3.1 (95% CI, 1.1-5.1) months, respectively. The objective response rate was 38.2% (7.3% with complete and 30.9% with partial response). Overall survival was not influenced by treatment line (2nd vs. >2nd) or previous systemic treatment modality (tyrosine kinase inhibitors vs. immune checkpoint inhibitors). Treatment-related adverse events of all grades according to Common Terminology Criteria for Adverse Events were documented in 42.6% of patients, with only 13.1% of grade ≥3, including one death. CONCLUSION: In this observational study, AB emerges as a safe and efficacious treatment option in patients with HCC previously treated with other systemic therapy.

Enolase represents a metabolic checkpoint controlling the differential exhaustion programmes of hepatitis virus-specific CD8+ T cells.

OBJECTIVE: Exhausted T cells with limited effector function are enriched in chronic hepatitis B and C virus (HBV and HCV) infection. Metabolic regulation contributes to exhaustion, but it remains unclear how metabolism relates to different exhaustion states, is impacted by antiviral therapy, and if metabolic checkpoints regulate dysfunction. DESIGN: Metabolic state, exhaustion and transcriptome of virus-specific CD8+ T cells from chronic HBV-infected (n=31) and HCV-infected patients (n=52) were determined ex vivo and during direct-acting antiviral (DAA) therapy. Metabolic flux and metabolic checkpoints were tested in vitro. Intrahepatic virus-specific CD8+ T cells were analysed by scRNA-Seq in a HBV-replicating murine in vivo model of acute and chronic infection. RESULTS: HBV-specific (core18-27, polymerase455-463) and HCV-specific (NS31073-1081, NS31406-1415, NS5B2594-2602) CD8+ T cell responses exhibit heterogeneous metabolic profiles connected to their exhaustion states. The metabolic state was connected to the exhaustion profile rather than the aetiology of infection. Mitochondrial impairment despite intact glucose uptake was prominent in severely exhausted T cells linked to elevated liver inflammation in chronic HCV infection and in HBV polymerase455-463 -specific CD8+ T cell responses. In contrast, relative metabolic fitness was observed in HBeAg-negative HBV infection in HBV core18-27-specific responses. DAA therapy partially improved mitochondrial programmes in severely exhausted HCV-specific T cells and enriched metabolically fit precursors. We identified enolase as a metabolic checkpoint in exhausted T cells. Metabolic bypassing improved glycolysis and T cell effector function. Similarly, enolase deficiency was observed in intrahepatic HBV-specific CD8+ T cells in a murine model of chronic infection. CONCLUSION: Metabolism of HBV-specific and HCV-specific T cells is strongly connected to their exhaustion severity. Our results highlight enolase as metabolic regulator of severely exhausted T cells. They connect differential bioenergetic fitness with distinct exhaustion subtypes and varying liver disease, with implications for therapeutic strategies.

Of tenants and nomads: The faces of memory T cells.

Memory T cells comprise circulating and tissue-resident subsets. In this issue of Immunity, Evrard et al. generate an imputed high-dimensional, single-cell protein expression atlas of memory CD8+ T cells, providing insights into stable differentiation markers and organ-specific expression patterns.

Morphologic and molecular analysis of liver injury after SARS-CoV-2 vaccination reveals distinct characteristics.

BACKGROUND & AIMS: Liver injury after COVID-19 vaccination is very rare and shows clinical and histomorphological similarities with autoimmune hepatitis (AIH). Little is known about the pathophysiology of COVID-19 vaccine-induced liver injury (VILI) and its relationship to AIH. Therefore, we compared VILI with AIH. METHODS: Formalin-fixed and paraffin-embedded liver biopsy samples from patients with VILI (n = 6) and from patients with an initial diagnosis of AIH (n = 9) were included. Both cohorts were compared by histomorphological evaluation, whole-transcriptome and spatial transcriptome sequencing, multiplex immunofluorescence, and immune repertoire sequencing. RESULTS: Histomorphology was similar in both cohorts but showed more pronounced centrilobular necrosis in VILI. Gene expression profiling showed that mitochondrial metabolism and oxidative stress-related pathways were more and interferon response pathways were less enriched in VILI. Multiplex analysis revealed that inflammation in VILI was dominated by CD8+ effector T cells, similar to drug-induced autoimmune-like hepatitis. In contrast, AIH showed a dominance of CD4+ effector T cells and CD79a+ B and plasma cells. T-cell receptor (TCR) and B-cell receptor sequencing showed that T and B cell clones were more dominant in VILI than in AIH. In addition, many T cell clones detected in the liver were also found in the blood. Interestingly, analysis of TCR beta chain and Ig heavy chain variable-joining gene usage further showed that TRBV6-1, TRBV5-1, TRBV7-6, and IgHV1-24 genes are used differently in VILI than in AIH. CONCLUSIONS: Our analyses support that SARS-CoV-2 VILI is related to AIH but also shows distinct differences from AIH in histomorphology, pathway activation, cellular immune infiltrates, and TCR usage. Therefore, VILI may be a separate entity, which is distinct from AIH and more closely related to drug-induced autoimmune-like hepatitis. IMPACT AND IMPLICATIONS: Little is known about the pathophysiology of COVID-19 vaccine-induced liver injury (VILI). Our analysis shows that COVID-19 VILI shares some similarities with autoimmune hepatitis, but also has distinct differences such as increased activation of metabolic pathways, a more prominent CD8+ T cell infiltrate, and an oligoclonal T and B cell response. Our findings suggest that VILI is a distinct disease entity. Therefore, there is a good chance that many patients with COVID-19 VILI will recover completely and will not develop long-term autoimmune hepatitis.

Impact of body mass index in patients receiving atezolizumab plus bevacizumab for hepatocellular carcinoma.

BACKGROUND: Atezolizumab plus bevacizumab (Atezo/Bev) is first line-treatment for unresectable hepatocellular carcinoma (HCC). Body mass index (BMI) has demonstrated predictive value for response to immunotherapy in non-HCC cancer types. Our study investigated the effect of BMI on safety and efficacy of real-life use of Atezo/Bev for unresectable HCC. METHODS: 191 consecutive patients from seven centres receiving Atezo/Bev were included in the retrospective study. Overall survival (OS), progression-free survival (PFS), overall response rate (ORR) and disease control rate (DCR) defined by RECIST v1.1 were measured in overweight (BMI ≥ 25) and non-overweight (BMI < 25) patients. Treatment-related adverse events (trAEs) were evaluated. RESULTS: Patients in the overweight cohort (n = 94) had higher rates of non-alcoholic fatty liver disease (NAFLD) and lower rates of Hepatitis B compared to non-overweight cohort (n = 97). Baseline Child-Pugh class and Barcelona Clinic Liver Cancer stage were similar between cohorts, with lower rates of extrahepatic spread in the overweight group. Overweight patients had similar OS compared to non-overweight (median OS 15.1 vs. 14.9 months; p = 0.99). BMI did not influence median PFS (7.1 vs. 6.1 months; p = 0.42), ORR (27.2% vs. 22.0%; p = 0.44) and DCR (74.1% vs. 71.9%; p = 0.46). There were higher rates of atezolizumab-related fatigue (22.3% vs. 10.3%; p = 0.02) and bevacizumab-related thrombosis (8.5% vs. 2.1%; p = 0.045) in the overweight patients, but overall trAEs and treatment discontinuation were comparable between cohorts. CONCLUSION: Atezo/Bev has comparable efficacy in overweight HCC patients, with an increase in treatment-related fatigue and thrombosis. Combination therapy is safe and efficacious to use in overweight patients, including those with underlying NAFLD.

Evolutionary and immune microenvironment dynamics during neoadjuvant treatment of oesophagael adenocarcinoma.

Locally advanced oesophageal adenocarcinoma (EAC) remains difficult to treat because of common resistance to neoadjuvant therapy and high recurrence rates. The ecological and evolutionary dynamics responsible for treatment failure are incompletely understood. Here, we performed a comprehensive multi-omic analysis of samples collected from EAC patients in the MEMORI clinical trial, revealing major changes in gene expression profiles and immune microenvironment composition that did not appear to be driven by changes in clonal composition. Multi-region multi-timepoint whole exome (300x depth) and paired transcriptome sequencing was performed on 27 patients pre-, during and after neoadjuvant treatment. EAC showed major transcriptomic changes during treatment with upregulation of immune and stromal pathways and oncogenic pathways such as KRAS, Hedgehog and WNT. However, genetic data revealed that clonal sweeps were rare, suggesting that gene expression changes were not clonally driven. Additional longitudinal image mass cytometry was performed in a subset of 15 patients and T-cell receptor sequencing in 10 patients, revealing remodelling of the T-cell compartment during treatment and other shifts in microenvironment composition. The presence of immune escape mechanisms and a lack of clonal T-cell expansions were linked to poor clinical treatment response. This study identifies profound transcriptional changes during treatment with limited evidence that clonal replacement is the cause, suggesting phenotypic plasticity and immune dynamics as mechanisms for therapy resistance with pharmacological relevance.

Prostaglandin E 2 controls the metabolic adaptation of T cells to the intestinal microenvironment.

Immune cells must adapt to different environments during the course of an immune response. We studied the adaptation of CD8 + T cells to the intestinal microenvironment and how this process shapes their residency in the gut. CD8 + T cells progressively remodel their transcriptome and surface phenotype as they acquire gut residency, and downregulate expression of mitochondrial genes. Human and mouse gut-resident CD8 + T cells have reduced mitochondrial mass, but maintain a viable energy balance to sustain their function. We found that the intestinal microenvironment is rich in prostaglandin E 2 (PGE 2 ), which drives mitochondrial depolarization in CD8 + T cells. Consequently, these cells engage autophagy to clear depolarized mitochondria, and enhance glutathione synthesis to scavenge reactive oxygen species (ROS) that result from mitochondrial depolarization. Impairing PGE 2 sensing promotes CD8 + T cell accumulation in the gut, while tampering with autophagy and glutathione negatively impacts the T cell population. Thus, a PGE 2 -autophagy-glutathione axis defines the metabolic adaptation of CD8 + T cells to the intestinal microenvironment, to ultimately influence the T cell pool.

[Immunotherapy in Hepatogastroenterology - update 2022: efficacy and immune-related adverse events]. / Immuntherapie in der Hepatogastroenterologie: Wirkung und Nebenwirkung.

ESOPHAGEAL CARCINOMA: Immune-checkpoint-inhibitors (ICI) are used for adjuvant therapy of squamous cell carcinoma and adenocarcinoma of the esophagogastric junction after prior radiotherapy. The combination of ICI with chemotherapy (CTx) is approved for first-line therapy in a palliative setting (Nivolumab and Ipilimumab) and as second-line option (Nivolumab). Squamous cell carcinoma probably has a higher response rate to ICI and Nivolumab and Ipilimumab are approved as a single therapy for this entity. GASTRIC CANCER: ICI combined with CTx is approved for metastatic gastric cancer. MSI-H tumors respond well to ICI and can be treated with Pembrolizumab in second line. COLORECTAL CANCER (CRC): ICI are only approved for MSI-H/dMMR CRC. Pembrolizumab is a first-line option and Nivolumab combined with Ipilimumab a second-line therapy. HEPATOCELLULAR CARCINOMA (HCC): Atezolizumab with Bevacizumab is the new first-line therapy of advanced HCC, with additional ICI combinations with positive Phase III studies expected to be approved in the near future. BILIARY CANCER: Durvalumab and CTx achieved promising results in a recent Phase 3 study. Pembrolizumab is already EMA-approved as a second-line therapy of MSI-H/dMMR biliary cancer. PANCREATIC CANCER: ICI have not yet achieved a breakthrough in the therapy of pancreatic cancer. FDA-approval exists only for the small subgroup of MSI-H/dMMR tumors. IMMUNE-RELATED ADVERSE EVENTS (IRAE): The disinhibition of the immune response by ICI can cause irAE. IrAE most frequently affect the skin, gastrointestinal tract, liver, and endocrine organs. Starting with grade 2 irAE, ICI should be paused, differential diagnosis excluded and if necessary steroid therapy has to be started. Early high-dose use of steroids negatively affects patient outcome. New therapy strategies for irAE are currently tested, such as extracorporeal photopheresis, but larger prospective trials are lacking.

Boosting compromised SARS-CoV-2-specific immunity with mRNA vaccination in liver transplant recipients.

BACKGROUND & AIMS: Liver transplant recipients (LTRs) demonstrate a reduced response to COVID-19 mRNA vaccination; however, a detailed understanding of the interplay between humoral and cellular immunity, especially after a third (and fourth) vaccine dose, is lacking. METHODS: We longitudinally compared the humoral, as well as CD4+ and CD8+ T-cell, responses between LTRs (n = 24) and healthy controls (n = 19) after three (LTRs: n = 9 to 16; healthy controls: n = 9 to 14 per experiment) to four (LTRs: n = 4; healthy controls: n = 4) vaccine doses, including in-depth phenotypical and functional characterization. RESULTS: Compared to healthy controls, development of high antibody titers required a third vaccine dose in most LTRs, while spike-specific CD8+ T cells with robust recall capacity plateaued after the second vaccine dose, albeit with a reduced frequency and epitope repertoire compared to healthy controls. This overall attenuated vaccine response was linked to a reduced frequency of spike-reactive follicular T helper cells in LTRs. CONCLUSION: Three doses of a COVID-19 mRNA vaccine induce an overall robust humoral and cellular memory response in most LTRs. Decisions regarding additional booster doses may thus be based on individual vaccine responses as well as evolution of novel variants of concern. IMPACT AND IMPLICATIONS: Due to immunosuppressive medication, liver transplant recipients (LTR) display reduced antibody titers upon COVID-19 mRNA vaccination, but the impact on long-term immune memory is not clear. Herein, we demonstrate that after three vaccine doses, the majority of LTRs not only exhibit substantial antibody titers, but also a robust memory T-cell response. Additional booster vaccine doses may be of special benefit for a small subset of LTRs with inferior vaccine response and may provide superior protection against evolving novel viral variants. These findings will help physicians to guide LTRs regarding the benefit of booster vaccinations.

Phosphoinositide acyl chain saturation drives CD8+ effector T cell signaling and function.

How lipidome changes support CD8+ effector T (Teff) cell differentiation is not well understood. Here we show that, although naive T cells are rich in polyunsaturated phosphoinositides (PIPn with 3-4 double bonds), Teff cells have unique PIPn marked by saturated fatty acyl chains (0-2 double bonds). PIPn are precursors for second messengers. Polyunsaturated phosphatidylinositol bisphosphate (PIP2) exclusively supported signaling immediately upon T cell antigen receptor activation. In late Teff cells, activity of phospholipase C-γ1, the enzyme that cleaves PIP2 into downstream mediators, waned, and saturated PIPn became essential for sustained signaling. Saturated PIP was more rapidly converted to PIP2 with subsequent recruitment of phospholipase C-γ1, and loss of saturated PIPn impaired Teff cell fitness and function, even in cells with abundant polyunsaturated PIPn. Glucose was the substrate for de novo PIPn synthesis, and was rapidly utilized for saturated PIP2 generation. Thus, separate PIPn pools with distinct acyl chain compositions and metabolic dependencies drive important signaling events to initiate and then sustain effector function during CD8+ T cell differentiation.

Capillary electrophoresis mass spectrometry identifies new isomers of inositol pyrophosphates in mammalian tissues.

Technical challenges have to date prevented a complete profiling of the levels of myo-inositol phosphates (InsPs) and pyrophosphates (PP-InsPs) in mammalian tissues. Here, we have deployed capillary electrophoresis mass spectrometry to identify and record the levels of InsPs and PP-InsPs in several tissues obtained from wild type mice and a newly created PPIP5K2 knockout strain. We observe that the mouse colon harbours unusually high levels of InsPs and PP-InsPs. Additionally, the PP-InsP profile is considerably more complex than previously reported for animal cells: using chemically synthesized internal stable isotope references and high-resolution mass spectra, we characterize two new PP-InsP isomers as 4/6-PP-InsP5 and 2-PP-InsP5. The latter has not previously been described in nature. The analysis of feces and the commercial mouse diet suggests that the latter is one potential source of noncanonical isomers in the colon. However, we also identify both molecules in the heart, indicating unknown synthesis pathways in mammals. We also demonstrate that the CE-MS method is sensitive enough to measure PP-InsPs from patient samples such as colon biopsies and peripheral blood mononuclear cells (PBMCs). Strikingly, PBMCs also contain 4/6-PP-InsP5 and 2-PP-InsP5. In summary, our study substantially expands PP-InsP biology in mammals.

Tissue CD14+CD8+ T cells reprogrammed by myeloid cells and modulated by LPS.

The liver is bathed in bacterial products, including lipopolysaccharide transported from the intestinal portal vasculature, but maintains a state of tolerance that is exploited by persistent pathogens and tumours1-4. The cellular basis mediating this tolerance, yet allowing a switch to immunity or immunopathology, needs to be better understood for successful immunotherapy of liver diseases. Here we show that a variable proportion of CD8+ T cells compartmentalized in the human liver co-stain for CD14 and other prototypic myeloid membrane proteins and are enriched in close proximity to CD14high myeloid cells in hepatic zone 2. CD14+CD8+ T cells preferentially accumulate within the donor pool in liver allografts, among hepatic virus-specific and tumour-infiltrating responses, and in cirrhotic ascites. CD14+CD8+ T cells exhibit increased turnover, activation and constitutive immunomodulatory features with high homeostatic IL-10 and IL-2 production ex vivo, and enhanced antiviral/anti-tumour effector function after TCR engagement. This CD14+CD8+ T cell profile can be recapitulated by the acquisition of membrane proteins-including the lipopolysaccharide receptor complex-from mononuclear phagocytes, resulting in augmented tumour killing by TCR-redirected T cells in vitro. CD14+CD8+ T cells express integrins and chemokine receptors that favour interactions with the local stroma, which can promote their induction through CXCL12. Lipopolysaccharide can also increase the frequency of CD14+CD8+ T cells in vitro and in vivo, and skew their function towards the production of chemotactic and regenerative cytokines. Thus, bacterial products in the gut-liver axis and tissue stromal factors can tune liver immunity by driving myeloid instruction of CD8+ T cells with immunomodulatory ability.

Progression patterns and therapeutic sequencing following immune checkpoint inhibition for hepatocellular carcinoma: An international observational study.

BACKGROUND AND AIMS: Different approaches are available after the progression of disease (PD) to immune checkpoint inhibitors (ICIs) for hepatocellular carcinoma (HCC), including the continuation of ICI, treatment switching to tyrosine kinase inhibitors (TKIs) and cessation of anticancer therapy. We sought to characterise the relationship between radiological patterns of progression and survival post-ICI, also appraising treatment strategies. METHODS: We screened 604 HCC patients treated with ICIs, including only those who experienced PD by data cut-off. We evaluated post-progression survival (PPS) according to the treatment strategy at PD and verified its relationship with radiological patterns of progression: intrahepatic growth (IHG), new intrahepatic lesion (NIH), extrahepatic growth (EHG), new extrahepatic lesion (NEH) and new vascular invasion (nVI). RESULTS: Of 604 patients, 364 (60.3%) experienced PD during observation. Median PPS was 5.3 months (95% CI: 4.4-6.9; 271 events). At the data cut-off, 165 patients (45%) received no post-progression anticancer therapy; 64 patients (17.6%) continued ICI beyond PD. IHG (HR 1.64 [95% CI: 1.21-2.22]; p = .0013) and nVI (HR 2.15 [95% CI: 1.38-3.35]; p = .0007) were associated with shorter PPS. Multivariate models adjusted for progression patterns, treatment line and albumin-bilirubin grade and Eastern Cooperative Oncology Group performance status at PD confirmed receipt of ICI beyond PD with (HR 0.17, 95% CI: 0.09-0.32; p < .0001) or without subsequent TKI (HR 0.39, 95% CI: 0.26-0.58; p < .0001) as predictors of prolonged PPS versus no anticancer therapy. CONCLUSIONS: ICI-TKI sequencing is a consolidated option in advanced HCC. nVI and IHG predict a poorer prognosis. Despite lack of recommendation, the continuation of ICI beyond progression in HCC is adopted clinically: future efforts should appraise which patients benefit from this approach.

Friend or Foe - Tc17 cell generation and current evidence for their importance in human disease.

The term Tc17 cells refers to interleukin 17 (IL-17)-producing CD8+ T cells. While IL-17 is an important mediator of mucosal defense, it is also centrally involved in driving the inflammatory response in immune-mediated diseases, such as psoriasis, multiple sclerosis, and inflammatory bowel disease. In this review, we aim to gather the current knowledge on the phenotypic and transcriptional profile, the in vitro and in vivo generation of Tc17 cells, and the evidence pointing towards a relevant role of Tc17 cells in human diseases such as infectious diseases, cancer, and immune-mediated diseases.