Perforin Deficiency Research Articles

CD8 T cell-derived perforin regulates macrophage-mediated inflammation in a murine model of gout.

Gout is characterized by hyperuricemia and recurrent inflammatory episodes caused by intra-articular crystal deposition of monosodium urate (MSU). There is a clear relationship between gout and metabolic syndrome. Recent evidence indicates that perforin plays a role in regulating glucose homeostasis and provides protection in diet-induced non-alcoholic steatohepatitis models. However, the impact of perforin on immune inflammation in gout remains unclear. We induced acute gout models in both wild-type (WT) mice and Prf1null mice by administering intra-articular injections of MSU crystals. We compared the ankle joint swelling and the histological score between the two groups. Furthermore, we investigated underlying mechanisms through in vitro co-culture experiments involving CD8 T cells and macrophages. In this study, Prf1null mice showed significantly more pronounced ankle swelling with increased inflammatory cell infiltrations compared with WT mice 24h after local MSU injection. Moreover, MSU-induced Prf1null mice exhibited increased accumulation of CD8 T cells but not NK cells. Perforin-deficient CD8 T cells displayed reduced cytotoxicity towards bone marrow-derived M0 and M1 macrophages and promoted TNF-α secretion from macrophage. Perforin from CD8 T cells limits joint inflammation in mice with acute gout by downregulating macrophage-mediated inflammation. Key Points • Perforin deficiency increased swelling in the ankle joints of mice upon MSU injection. • Perforin deficiency is associated with increased immune cell recruitment and severe joint damage in gout. • Perforin regulated CD8 T cell accumulation in gout and promoted CD8 T cell cytotoxicity towards M0 and M1 macrophages. • CD8 T cell-derived perforin regulated pro-inflammatory cytokine secretion of macrophage.

Low Percentage of Perforin-Expressing NK Cells during Severe SARS-CoV-2 Infection: Consumption Rather than Primary Deficiency.

Genetic defects in the ability to deliver effective perforin have been reported in patients with hemophagocytic lymphohistiocytosis. We tested the hypothesis that a primary perforin deficiency might also be causal in severe SARS-CoV-2 infection. We recruited 54 volunteers confirmed as being SARS-CoV-2-infected by RT-PCR and admitted to intensive care units or non-intensive care units and age- and sex-matched healthy controls. Compared with healthy controls, the percentage of perforin-expressing CD3-CD56+ NK cells quantified by flow cytometry was low in COVID-19 patients (69.9 ± 17.7 versus 78.6 ± 14.6%, p = 0.026). There was no correlation between the proportions of perforin-positive NK cells and T8 lymphocytes. Moreover, the frequency of NK cells producing perforin was neither linked to disease severity nor predictive of death. Although IL-6 is known to downregulate perforin production in NK cells, we did not find any link between perforin expression and IL-6 plasma level. However, we unveiled a negative correlation between the degranulation marker CD107a and perforin expression in NK cells (r = -0.488, p = 10-4). PRF1 gene expression and the frequency of NK cells harboring perforin were normal in patients 1 y after acute SARS-CoV-2 infection. A primary perforin defect does not seem to be a driver of COVID-19 because NK perforin expression is 1) linked neither to T8 perforin expression nor to disease severity, 2) inversely correlated with NK degranulation, and 3) normalized at distance from acute infection. Thus, the cause of low frequency of perforin-positive NK cells appears, rather, to be consumption.

Complementary HLH susceptibility factors converge on CD8 T-cell hyperactivation

AbstractHemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening hyperinflammatory syndromes. Familial HLH is caused by genetic impairment of granule-mediated cytotoxicity (eg, perforin deficiency). MAS is linked to excess activity of the inflammasome-activated cytokine interleukin-18 (IL-18). Though individually tolerated, mice with dual susceptibility (Prf1⁻/⁻Il18tg; DS) succumb to spontaneous, lethal hyperinflammation. We hypothesized that understanding how these susceptibility factors synergize would uncover key pathomechanisms in the activation, function, and persistence of hyperactivated CD8 T cells. In IL-18 transgenic (Il18tg) mice, IL-18 effects on CD8 T cells drove MAS after a viral (lymphocytic choriomeningitis virus), but not innate (toll like receptor 9), trigger. In vitro, CD8 T cells also required T-cell receptor (TCR) stimulation to fully respond to IL-18. IL-18 induced but perforin deficiency impaired immunoregulatory restimulation-induced cell death (RICD). Paralleling hyperinflammation, DS mice displayed massive postthymic oligoclonal CD8 T-cell hyperactivation in their spleens, livers, and bone marrow as early as 3 weeks. These cells increased proliferation and interferon gamma production, which contrasted with increased expression of receptors and transcription factors associated with exhaustion. Broad-spectrum antibiotics and antiretrovirals failed to ameliorate the disease. Attempting to genetically “fix” TCR antigen-specificity instead demonstrated the persistence of spontaneous HLH and hyperactivation, chiefly on T cells that had evaded TCR fixation. Thus, drivers of HLH may preferentially act on CD8 T cells: IL-18 amplifies activation and demand for RICD, whereas perforin supplies critical immunoregulation. Together, these factors promote a terminal CD8 T-cell activation state, combining features of exhaustion and effector function. Therefore, susceptibility to hyperinflammation may converge on a unique, unrelenting, and antigen-dependent state of CD8 T-cell hyperactivation.

Granzyme-A deficiency attenuates experimental osteoarthritis in mice, but perforin deficiency does not.

This study aims to assess the development of osteoarthritis (OA) in granzyme A- (gzmA) and B- (gzmB) and perforin- (perf) knockout mice. A total of 75 male and female C57BL/6 (eight to nine-week-old) mice were allocated to: gzmA-deficient (gzmA-/-) (11 females, 8 males), gzmB-deficient (gzmB-/-) (9 females, 8 males), perf-deficient (perf-/-) (10 females, 9 males), and control group (10 females, 10 males). Osteoarthritis was induced in the right knee by instability of the meniscus medial ligament. Sham surgery was practiced in the left knee. Knee samples obtained eight weeks after surgery were stained (Safranin-O) and blindly scored in lateral and medial femur and tibia using the Osteoarthritis Research Society International scale (OARSI) (from Grade 0, cartilage intact to 6, deformation), (five stages from 0, no OA to 4, >50% surface involvement); OARSI score (Grade x Stage); and a semi-quantitative scale from Grade 0 (normal) to 6 (cartilage erosion >80%). Significantly higher values in all scales in the right knees compared to the left knees in male and female mice were observed (p<0.05). Males of all strains showed in the right knee higher values than females on all scales. Deficiency of perforin did not modify OA severity in any sex. The gzmA-/- females presented less degenerative changes than the other groups. Our study results show that sex plays an important role in the development of experimental OA in mice. Deficiency of gzmA can protect from the development of OA in female mice.

NK cell-derived extracellular granzyme B drives epithelial ulceration during HSV-2 genital infection

Genital herpes is characterized by recurrent episodes of epithelial blistering. The mechanisms causing this pathology are ill defined. Using a mouse model of vaginal herpes simplex virus 2 (HSV-2) infection, we show that interleukin-18 (IL-18) acts upon natural killer (NK) cells to promote accumulation of the serine protease granzyme B in the vagina, coinciding with vaginal epithelial ulceration. Genetic loss of granzyme B or therapeutic inhibition by a specific protease inhibitor reduces disease and restores epithelial integrity without altering viral control. Distinct effects of granzyme B and perforin deficiency on pathology indicates that granzyme B acts independent of its classic cytotoxic role. IL-18 and granzyme B are markedly elevated in human herpetic ulcers compared with non-herpetic ulcers, suggesting engagement of these pathways in HSV-infected patients. Our study reveals a role for granzyme B in destructing mucosal epithelium during HSV-2 infection, identifying a therapeutic target to augment treatment of genital herpes.

Hemophagocytic Lymphohistiocytosis.

Hemophagocytic Lymphohistiocytosis.

Treatment Dilemmas in Asymptomatic Children with Primary Haemophagocytic Lymphohistiocytosis

IntroductionPrimary haemophagocytic lymphohistiocytosis (HLH) is caused by mutations in genes which affect the exocytosis of apoptotic granules in T/NK cells, hampering their killing function. Once symptomatic, it requires induction treatment based on steroids and chemotherapy or immunotherapy followed by allogeneic stem cell transplantation (SCT). Difficulties in achieving a good remission prior to SCT and high treatment related toxicities have resulted in overall survival (OS) of only 50-60% at 5 years. Primary HLH has an autosomal recessive pattern of inheritance and studies have shown that only 1/3 of the relatives affected by the same genetic mutation as index cases (ICs) have comparable clinical presentations. It is therefore a challenging decision to offer SCT to a patient with a recognized genetic defect that predisposes to HLH but with no clinical symptoms. Our study investigated outcomes of pairs of ICs and asymptomatic family members with a known genetic defect predisposing to primary HLH. The study also analysed therapeutic attitudes towards the asymptomatic cases (ACs) at various international paediatric BMT centres.MethodsPatients <18 years were eligible for this study if they had a mutation in one of the known causative genes for primary HLH, if they were asymptomatic at the time of diagnosis, and if their diagnosis was made after an IC in the family. After appropriate IRB review, data was collected through a questionnaire distributed to centres through the Histiocyte Society.Results19 Centres in Europe and North America were contacted and they reported a total of 28 analysable pairs of ICs and asymptomatic cases (ACs). Of these, 11 had perforin deficiency, 6 Griscelli syndrome type II, 5 MUNC 18-2 deficiency, 3 MUNC 13-4 deficiency, 2 syntaxin deficiency, and 1 Chediak Higashi syndrome.All ICs had overt disease at the time of presentation at a median age of 1.5 years (range 0-11.5). 14/28 (50.0%) had CNS involvement and 6 (21.4%) were refractory to front line treatment. 18/28 (64.3%) underwent SCT. 13 (72.2%) are alive in complete remission (CR). 4 died due to transplant related mortality (TRM) and 1 from disease progression post SCT. 9 (32.1%) did not undergo SCT and received chemo-immuno therapy. Of these, 2 are alive in CR (both with MUNC 18-2 deficiency), 1 was lost to follow up and 6 have died due to disease progression (n=5) or treatment related toxicity (n=1). One child had an undocumented treatment and died from unknown causes. 15/28 (53.6%) of ICs are alive at a median follow up of 3 years from diagnosis (range 0.1-11).Median age of ACs at diagnosis was 0.7 years (range 0-15). Of these, 9/28 (32.1%) activated HLH whilst on observation/waiting for SCT and 2 (22.2%) required multiple lines of treatment to achieve remission. 8 patients underwent SCT; 5 are alive in CR and 3 died (2 from disease progression and 1 from TRM). The remaining patient was on treatment with HLH04 protocol when he was lost to follow up. Of the remaining 19 ACs, 6 have received no specific treatment and are being monitored. They are all alive in CR. 13 underwent SCT as a pre-emptive measure and 12 are alive in CR at a median follow up of 37 months, 1 died of SCT unrelated causes 12 months post SCT whilst in CR.Of 27 evaluable ACs, 23 (82.1%) are alive at a median follow up of 3 year from diagnosis (0.6 to 11). 17/21 patients who underwent SCT are alive (81.0%). 12/13 (92.3%) transplanted before the development of HLH are alive compared to 5/8 (62.5%) transplanted after HLH development (p=0.25)OS for ACs was significantly higher than for ICs irrespective of treatment (82.1% vs 53.6%, p=0.02). There was no survival difference according to the underlying genetic defect. Based on their clinical experience, 80% of the reporting centres would favour elective SCT in future ACs, 10% would adopt a careful ‘wait and watch’ policy and 10% would be guided by the severity of presentation in the index case.ConclusionIn our study ACs had a significant survival advantage especially if transplanted before the development of HLH, where survival was nearly 100%. Most transplant centres are adopting the approach of pre-emptive SCT. This information will be very valuable for physicians and families faced with this difficult decision. DisclosuresLucchini:Alexion: Membership on an entity's Board of Directors or advisory committees.

Human Visceral Adipose Tissue (VAT) Inflammation Is Not Associated With Perforin Deficiency in Type 2 Diabetes Mellitus (DM) Subjects as Compared to Health Controls

Abstract Introduction: Role of T cells in VAT inflammation is poorly characterised. Perforin deficiency is associated with autoimmune inflammatory diseases like Hemophagocytosis Lymphohistiocytosis,as also in context of type 1 DM pathogenesis. Data from animal models suggest that perforin deficiency leads to VAT inflammation1Objective: We hypothesized CD8+/perf+ and CD56+/perf+ cells to be decreased in type 2 DM as compared to healthy controls. The present study also explored the difference in activation of T/NK cells between two groups Methods: 2×2 cm omental tissue was obtained from subjects undergoing elective abdominal surgery. The sample was transported in RPMI solution and stored in -80 ℃. Processing involved thawing, incubation at 37.6 ℃ for 24 hours with type IV Collagenase (1 mg/ml, Sigma Aldrich) 1ml/g of tissue,centrifuge (32g for 10 min at 10℃). The resultant Stromal Vascular fraction (SVF) was suspended in phosphate buffer saline (PBS), passed through cell strainer to make single cell suspension. It was again centrifuged and tagged with CD markers of interest. Fc block was added and single cell solution with FACS fluid prepared. It was run in BD CANTO-2 flow cytometer as described2Results: Of seventeen samples analysed, twelve samples of type 2 diabetes subjects were compared with five healthy controls. All results are presented in median. The diabetics had higher HbA1c (8.1 % vs 6%), higher BMI (28 kg/m2 vs 24 kg/m2), hsCRP(2.1 mg/dl Vs 0.9 mg/dl) but there was no difference in HOMA-Ir (5 vs 5.2 mU/L/mg/dl). The percentage of CD4+ + CD8+ cells/g of VAT was similar in both cases and control (20 × 103 Vs 23× 103). CD8+/CD45+/perf+ and CD56+/CD45+/perf+ could not be identified in any of the samples. Although CD8+/CD45+/perf-- and CD56+/CD45+/perf-- cells were identified. Next, we analysed the same cells for cytotoxic activation by 107a. The percentage of 107a positivity was low in CD 8+ (7% and 4 % respectively in cases and control) and CD 56+ cells (10% and 9 % respectively in cases and control),Although clinically type 2 DM subjects were obese and had inflammation (i.e higher hsCRP), there was no difference in VAT activation of immune cells studied. Also, we could not delineate perforin in any of the samples. Conclusion: Taken together this work suggests VAT T cell immune milieu in human Type 2 DM is different from mouse model. It is neither characterised by perforin deficiency nor activation of T cell/NK cell. This study points towards the probability that, the role of T cell/NK cells in human VAT infiltration could be fundamentally different from mice models. Further studies should be focussed on functional characteristics of these cells and interaction with VAT macrophages.

Interleukin-18 and cytotoxic impairment are independent and synergistic causes of murine virus-induced hyperinflammation

AbstractHemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening hyperinflammatory syndromes typically associated with underlying hematologic and rheumatic diseases, respectively. Familial HLH is associated with genetic cytotoxic impairment and thereby to excessive antigen presentation. Extreme elevation of serum interleukin-18 (IL-18) has been observed specifically in patients with MAS, making it a promising therapeutic target, but how IL-18 promotes hyperinflammation remains unknown. In an adjuvant-induced MAS model, excess IL-18 promoted immunopathology, whereas perforin deficiency had no effect. To determine the effects of excess IL-18 on virus-induced immunopathology, we infected Il18-transgenic (Il18tg) mice with lymphocytic choriomeningitis virus (LCMV; strain Armstrong). LCMV infection is self-limited in wild-type mice, but Prf1−/− mice develop prolonged viremia and fatal HLH. LCMV-infected Il18-transgenic (Il18tg) mice developed cachexia and hyperinflammation comparable to Prf1−/− mice, albeit with minimal mortality. Like Prf1−/− mice, immunopathology was largely rescued by CD8 depletion or interferon-γ (IFNg) blockade. Unlike Prf1−/− mice, they showed normal target cell killing and normal clearance of viral RNA and antigens. Rather than impairing cytotoxicity, excess IL-18 acted on T lymphocytes to amplify their inflammatory responses. Surprisingly, combined perforin deficiency and transgenic IL-18 production caused spontaneous hyperinflammation specifically characterized by CD8 T-cell expansion and improved by IFNg blockade. Even Il18tg;Prf1-haplosufficient mice demonstrated hyperinflammatory features. Thus, excess IL-18 promotes hyperinflammation via an autoinflammatory mechanism distinct from, and synergistic with, cytotoxic impairment. These data establish IL-18 as a potent, independent, and modifiable driver of life-threatening innate and adaptive hyperinflammation and support the rationale for an IL-18–driven subclass of hyperinflammation.

O15 Recognition of subclinical macrophage activation syndrome in an adolescent systemic juvenile idiopathic arthritis patient receiving tocilizumab: a case report

O15 Recognition of subclinical macrophage activation syndrome in an adolescent systemic juvenile idiopathic arthritis patient receiving tocilizumab: a case report

Perforin-deficient CAR T cells recapitulate late-onset inflammatory toxicities observed in patients.

Late-onset inflammatory toxicities resembling hemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (MAS) occur after chimeric antigen receptor T cell (CAR T cell) infusion and represent a therapeutic challenge. Given the established link between perforin deficiency and primary HLH, we investigated the role of perforin in anti-CD19 CAR T cell efficacy and HLH-like toxicities in a syngeneic murine model. Perforin contributed to both CD8+ and CD4+ CAR T cell cytotoxicity but was not required for in vitro or in vivo leukemia clearance. Upon CAR-mediated in vitro activation, perforin-deficient CAR T cells produced higher amounts of proinflammatory cytokines compared with WT CAR T cells. Following in vivo clearance of leukemia, perforin-deficient CAR T cells reexpanded, resulting in splenomegaly with disruption of normal splenic architecture and the presence of hemophagocytes, which are findings reminiscent of HLH. Notably, a substantial fraction of patients who received anti-CD22 CAR T cells also experienced biphasic inflammation, with the second phase occurring after the resolution of cytokine release syndrome, resembling clinical manifestations of HLH. Elevated inflammatory cytokines such as IL-1β and IL-18 and concurrent late CAR T cell expansion characterized the HLH-like syndromes occurring in the murine model and in humans. Thus, a murine model of perforin-deficient CAR T cells recapitulated late-onset inflammatory toxicities occurring in human CAR T cell recipients, providing therapeutically relevant mechanistic insights.

Toxicity Induced by a Bispecific T Cell-Redirecting Protein Is Mediated by Both T Cells and Myeloid Cells in Immunocompetent Mice.

Bispecific T cell engagers have demonstrated clinical efficacy; however, their use can be accompanied by severe toxicity. Mechanistic understanding of these toxicities is limited by a lack of suitable immunocompetent preclinical models. In this study, we describe an immunocompetent mouse tumor model that exhibits bispecific T cell engager-induced toxicity and recapitulates key features similar to those in human cytokine release syndrome. In this study, toxicity occurred between the second and fourth injections of an NK Group 2D bispecific T cell engager protein. Symptoms were transient, peaking 3-4 h after treatment and resolving by 8 h. Mice developed weight loss, elevated plasma cytokines, a significant reduction in spleen white pulp, and lymphocyte infiltration in the liver. Systemic cellular immune changes also occurred; notably, an increase in CD8+ T cell activation, an increase in myeloid cells in the blood, and a population of Ly-6Cint monocytes (CD11b+Ly-6G-F4/80-) emerged in the liver and spleens of bispecific protein-treated mice. IFN-γ was primarily produced by CD8+ T cells in the spleen and was required for the observed changes in both T cell and myeloid populations. Rag deficiency, IFN-γ deficiency, or depletion of either CD4+ or CD8+ T cells prevented toxicity, whereas perforin deficiency, GM-CSF deficiency, or modulation of the myeloid population through clodronate-mediated depletion showed a partial abrogation of toxicity. Together, these findings reveal that T cell activation by a bispecific T cell engager leads to changes in the host myeloid cell population, both of which contribute to treatment induced toxicity in immunocompetent mice.

Alemtuzumab as First Line Treatment in Children with Familial Lymphohistiocytosis

Background Hemophagocytic lymphohistiocytosis (HLH) is an inflammatory condition caused by uncontrolled proliferation of activated lymphocytes and macrophages secreting an excess of inflammatory cytokines. When untreated, primary HLH is invariably fatal. Treatment requires the achievement of remission of HLH prior to allogeneic hematopoietic stem cell transplantation. Despite significant treatment progress, pre-HSCT mortality remains a challenge. In the Etoposide-based HLH-94 and HLH-2004 studies pre-HSCT mortality was 27% and 19%, respectively. A better understanding of the pathophysiology of primary HLH has opened new avenues for targeted immunotherapy. Based on our previous observation concerning the use of Antithymoglobulin in HLH, we propose a new therapeutic strategy with Alemtuzumab in association with steroids and cyclosporine A (CSA) as first line treatment in primary HLH. In contrast to ATG, Alemtuzumab does not activate T lymphocytes while killing them. Therefore, we expect a better tolerance and efficacy of Alemtuzumab. This may have a positive impact not only on survival until HSCT, but also on overall survival and quality of life, especially with regard to long-term neurological sequelae. Methods 24 consecutive treatment naïve patients with genetically confirmed primary HLH had received first line Alemtuzumab in association to steroids and CSA from 01/2009 to 06/2015 in the Unit for Pediatric Immunology in Necker Hospital Paris, as well as two additional patients in 10/2016 and 10/2018 respectively, who could not be included in the prospective trial. From 06/2015 to 06/2019, 29 patients have been enrolled in a multicenter, open, phase I/II, non-comparative, non randomized study (NCT02472054). Patients with lymphohistiocytic activation syndrome who had not received any specific treatment prior to enrollment except steroids and CSA were included. Treatment consisted in intravenous administration of Alemtuzumab in association to Methylprednisolone and CSA. The primary outcome measures is the number of surviving patients until HSCT, secondary outcome measures the number of complete remissions following treatment at Day (D)14, D21, D28. To assess the efficacy of the Alemtuzumab, the time of delay between the first administration of Alemtuzumab and complete remission will be determined. Alemtuzumab Pharmacokinetics will be done. All adverse events are reported. Results Retrospective analysis of 26 patients (pilot study): The median age of patients was 1.9 months (birth - 7 years), 6 patients were neonates. When Alemtuzumab was started, out of 26 patients 12 (46.1%) required intensive care, 8 (30.7%) mechanical ventilation, 13 (50%) had neurological involvement, 9 (34.6%) hepatocellular insufficiency. One 2-month-old Munc13-4 patient died at H+48 after two administrations of Alemtuzumab (total dose 1.5mg/kg) for hepatic failure and acute renal failure. A second patient with Perforin deficiency did not respond neither to three courses of Alemtuzumab (cumulative dose 6.5mg/kg) nor repeated Etoposid, 40mg/kg ATG, or Ruxulotinib. He died at D+65. The 24 remaining patients survived until HSCT (survival 92.3%). As shown in the figure, two patients required additional treatment. Overall 22 patients achieved CR, 2 PR at the time of HSCT. The prospective study enrolled 29 patients from 06/2015 to 06/2019. Median age at onset of HLH was 0.5 years (range 0.02 to 17.2 years), one patient withdrawed consent. 12 patients received one course, 13 two, 2 three and one patient 4 courses of Alemtuzumab. 24 patients with a genetic confirmed HLH predisposition reached the primary endpoint with 22 surviving until HSCT (91,6%). One patient is still awaiting HSCT. The three remaining patients are one CA-EBV patient and a newborn with secondary HLH due to fulminant HSV hepatitis, who both died, as well as a patient with predominant neurological HLH without genetic diagnosis who is in sustained remission without any specific treatment. Detailed results from the completed study will be presented. Conclusions This is the first report on Alemtuzumab as first line approach in the treatment of primary HLH. Our results in more than 50 pediatric patients treated in a pilot study and prospective trial indicate that Alemtuzumab allows controlling HLH activity with a favorable safety and tolerability profile in a very fragile population. 92.3% and 91.6% of patients respectively survived to HSCT. Figure Disclosures No relevant conflicts of interest to declare. Off Label Disclosure: Alemtuzumab (Campath) has been used in a prospective trial to evaluate its efficacy as first line treatment in Familial Lymphohistiocytosis.

The immunoregulatory effects of CD8 T-cell-derived perforin on diet-induced nonalcoholic steatohepatitis.

The liver is a central immunologic organ with a high density of myeloid and lymphoid immune cells that play important roles in the development and progression of nonalcoholic steatohepatitis (NASH). However, the immune-cell-mediated regulation of NASH and its underlying mechanisms remain obscure. In this study, Prf1null mice showed significantly higher plasma alanine transaminase levels, with increased liver fat accumulation, lobular inflammation, and focal necrosis compared with wild-type (WT) mice after 4 wk of feeding on a methionine- and choline-deficient diet (MCD) or 16 wk of feeding on a high-fat diet. Perforin deficiency promoted the M1 polarization of infiltrated monocytes. Moreover, MCD-fed Prf1null mice exhibited increased accumulation, survival, activation, and proinflammatory cytokine production of CD8 T cells but not NK cells or CD4 T cells. Adoptive transfer of CD8 T cells or NK cells from WT or Prf1null mice, together with non-CD8 cells or non-NK cells from WT mice, indicated that CD8 T-cell-derived perforin participates in the mechanism regulating liver inflammation and thus plays a protective role in the development of NASH. Perforin-deficient CD8 T cells exhibited decreased cytotoxicity toward bone marrow-derived M1 monocytes and macrophages. According to the RNA sequencing data, the perforin deficiency inhibited cell apoptosis and enhanced the activation, migration, and proinflammatory cytokine production of CD8 T cells in mice with NASH. Furthermore, we found higher plasma soluble perforin levels and hepatic perforin expression in NASH patients, suggesting clinical relevance of the findings. We have elucidated an important role for the cytotoxic immune effector molecule perforin from CD8 T cells in restricting hepatic inflammation in mice with NASH and suggest that therapies designed to maximize the function of endogenous perforin in CD8 T cells might have potential benefits as NASH treatments.-Wang, T., Sun, G., Wang, Y., Li, S., Zhao, X., Zhang, C., Jin, H., Tian, D., Liu, K., Shi, W., Tian, Y., Zhang, D. The immunoregulatory effects of CD8 T-cell-derived perforin on diet-induced nonalcoholic steatohepatitis.

Deficiency of perforin and hCNT1, a novel inborn error of pyrimidine metabolism, associated with a rapidly developing lethal phenotype due to multi-organ failure

Pyrimidine nucleotides are essential for a vast number of cellular processes and dysregulation of pyrimidine metabolism has been associated with a variety of clinical abnormalities. Inborn errors of pyrimidine metabolism affecting enzymes in the pyrimidine de novo and degradation pathway have been identified but no patients have been described with a deficiency in proteins affecting the cellular import of ribonucleosides. In this manuscript, we report the elucidation of the genetic basis of the observed uridine-cytidineuria in a patient presenting with fever, hepatosplenomegaly, persistent lactate acidosis, severely disturbed liver enzymes and ultimately multi-organ failure. Sequence analysis of genes encoding proteins directly involved in the metabolism of uridine and cytidine showed two variants c.1528C > T (p.R510C) and c.1682G > A (p.R561Q) in SLC28A1, encoding concentrative nucleotide transporter 1 (hCNT1). Functional analysis showed that these variants affected the three-dimensional structure of hCNT1, altered glycosylation and decreased the half-life of the mutant proteins which resulted in impaired transport activity. Co-transfection of both variants, mimicking the trans disposition of c.1528C > T (p.R510C) and c.1682G > A (p.R561Q) in the patient, significantly impaired hCNT1 biological function. Whole genome sequencing identified two pathogenic variants c.50delT; p.(Leu17Argfs*34) and c.853_855del; p.(Lys285del) in the PRF1 gene, indicating that our patient was also suffering from Familial Hemophagocytic Lymphohistiocytosis type 2. The identification of two co-existing monogenic defects might have resulted in a blended phenotype. Thus, the clinical presentation of isolated hCNT1 deficiency remains to be established.

Downregulation of CD5 and dysregulated CD8+ T-cell activation.

CD5 is a cell surface molecule that is expressed on most circulating T cells and a small population of B cells, and is involved in modulation of antigen-specific receptor-mediated activation. Downregulation of CD5 on CD8+ T cells is a poorly understood but increasingly recognized phenomenon that may be associated with dysregulated T-cell activation. An increased subpopulation of activated CD8+ T cells with downregulation of CD5 has recently been described in patients with Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (HLH) and familial HLH caused by perforin deficiency and Munc 13-4 deficiency. These cells were detectable only in the acute phase of HLH, in which patients exhibited hypercytokinemia, and declined progressively after successful treatment in parallel with improvement of systemic inflammation. It is unknown whether CD8+ T cells from HLH with other causes have similar profiles. Assessment of CD5 expression on T cells has the potential to assist in the understanding of the diagnosis and pathogenesis of human inflammatory diseases such as HLH.

Urothelial bladder cancer may suppress perforin expression in CD8+ T cells by an ICAM-1/TGFβ2 mediated pathway.

The immune system plays a significant role in urothelial bladder cancer (UBC) progression, with CD8+ T cells being capable to directly kill tumor cells using perforin and granzymes. However, tumors avoid immune recognition by escape mechanisms. In this study, we aim to demonstrate tumor immune escape mechanisms that suppress CD8+ T cells cytotoxicity. 42 patients diagnosed with UBC were recruited. CD8+ T cells from peripheral blood (PB), sentinel nodes (SN), and tumor were analyzed in steady state and in vitro-stimulated conditions by flow cytometry, RT-qPCR, and ELISA. Mass spectrometry (MS) was used for identification of proteins from UBC cell line culture supernatants. Perforin was surprisingly found to be low in CD8+ T cells from SN, marked by 1.8-fold decrease of PRF1 expression, with maintained expression of granzyme B. The majority of perforin-deficient CD8+ T cells are effector memory T (TEM) cells with exhausted Tc2 cell phenotype, judged by the presence of PD-1 and GATA-3. Consequently, perforin-deficient CD8+ T cells from SN are low in T-bet expression. Supernatant from muscle invasive UBC induces perforin deficiency, a mechanism identified by MS where ICAM-1 and TGFβ2 signaling were causatively validated to decrease perforin expression in vitro. Thus, we demonstrate a novel tumor escape suppressing perforin expression in CD8+ T cells mediated by ICAM-1 and TGFβ2, which can be targeted in combination for cancer immunotherapy.

Perforin proteostasis is regulated through its C2 domain: supra-physiological cell death mediated by T431D-perforin.

The pore forming, Ca2+-dependent protein, perforin, is essential for the function of cytotoxic lymphocytes, which are at the frontline of immune defence against pathogens and cancer. Perforin is a glycoprotein stored in the secretory granules prior to release into the immune synapse. Congenital perforin deficiency causes fatal immune dysregulation, and is associated with various haematological malignancies. At least 50% of pathological missense mutations in perforin result in protein misfolding and retention in the endoplasmic reticulum. However, the regulation of perforin proteostasis remains unexplored. Using a variety of biochemical assays that assess protein stability and acquisition of complex glycosylation, we demonstrated that the binding of Ca2+ to the C2 domain stabilises perforin and regulates its export from the endoplasmic reticulum to the secretory granules. As perforin is a thermo-labile protein, we hypothesised that by altering its C2 domain it may be possible to improve protein stability. On the basis of the X-ray crystal structure of the perforin C2 domain, we designed a mutation (T431D) in the Ca2+ binding loop. Mutant perforin displayed markedly enhanced thermal stability and lytic function, despite its trafficking from the endoplasmic reticulum remaining unchanged. Furthermore, by introducing the T431D mutation into A90V perforin, a pathogenic mutation, which results in protein misfolding, we corrected the A90V folding defect and completely restored perforin's cytotoxic function. These results revealed an unexpected role for the Ca2+-dependent C2 domain in maintaining perforin proteostasis and demonstrated the possibility of designing perforin with supra-physiological cytotoxic function through stabilisation of the C2 domain.

CD8 T Cell Memory Increases Immunopathology in the Perforin-Deficient Model of Hemophagocytic Lymphohistiocytosis Secondary to TNF-α.

Familial hemophagocytic lymphohistiocytosis 2 (FHL2) is a cytokine storm syndrome characterized by immune hyperactivation with viral infection due to a CD8 T cell cytotoxic killing defect secondary to a perforin deficiency. As most studies of FHL2 mice have used pathogen naïve animals, the effects of immune memory on FHL2 are understudied. We utilized an immunization model of the perforin-deficient mouse to study the effects of immune memory on FHL2. Prior CD8 T cell specific antigen exposure leads to enhanced HLH disease with increased morbidity and decreased time to mortality. Enhanced disease is associated with altered cytokine production and T cell proliferation. Response to IFNγ blockade is reduced and TNFα gains a pathogenic role, while blockade of the IL-33 receptor ST2 remains effective. These results suggest that pre-existing immune memory may worsen outcome and alter treatment response for FHL2 patients who may not be naïve to their immune triggers.

T-cell gene therapy for perforin deficiency corrects cytotoxicity defects and prevents hemophagocytic lymphohistiocytosis manifestations

BackgroundMutations in the perforin 1 (PRF1) gene account for up to 58% of familial hemophagocytic lymphohistiocytosis syndromes. The resulting defects in effector cell cytotoxicity lead to hypercytokinemia and hyperactivation with inflammation in various organs.ObjectiveWe sought to determine whether autologous gene-corrected T cells can restore cytotoxic function, reduce disease activity, and prevent hemophagocytic lymphohistiocytosis (HLH) symptoms in in vivo models.MethodsWe developed a gammaretroviral vector to transduce murine CD8 T cells in the Prf−/− mouse model. To verify functional correction of Prf−/− CD8 T cells in vivo, we used a lymphocytic choriomeningitis virus (LCMV) epitope–transfected murine lung carcinoma cell tumor model. Furthermore, we challenged gene-corrected and uncorrected mice with LCMV. One patient sample was transduced with a PRF1-encoding lentiviral vector to study restoration of cytotoxicity in human cells.ResultsWe demonstrated efficient engraftment and functional reconstitution of cytotoxicity after intravenous administration of gene-corrected Prf−/− CD8 T cells into Prf−/− mice. In the tumor model infusion of Prf−/− gene–corrected CD8 T cells eliminated the tumor as efficiently as transplantation of wild-type CD8 T cells. Similarly, mice reconstituted with gene-corrected Prf−/− CD8 T cells displayed complete protection from the HLH phenotype after infection with LCMV. Patients' cells showed correction of cytotoxicity in human CD8 T cells after transduction.ConclusionThese data demonstrate the potential application of T-cell gene therapy in reconstituting cytotoxic function and protection against HLH in the setting of perforin deficiency.