B-cell immune deficiency in twin sisters expands the phenotype of MOPDI.

Microcephalic osteodysplastic primordial dwarfism type I (MOPDI) is a very rare and severe autosomal recessive disorder characterized by marked intrauterine growth retardation, skeletal dysplasia, microcephaly and brain malformations. MOPDI is caused by biallelic mutations in RNU4ATAC, a non-coding gene involved in U12-type splicing of 1% of the introns in the genome, which are recognized by their specific splicing consensus sequences. Here, we describe a unique observation of immunodeficiency in twin sisters with mild MOPDI, who harbor a novel n.108_126del mutation, encompassing part of the U4atac snRNA 3' stem-loop and Sm protein binding site, and the previously reported n.111G>A mutation. Interestingly, both twin sisters show mild B-cell anomalies, including low naive B-cell counts and increased memory B-cell and plasmablasts counts, suggesting partial and transitory blockage of B-cell maturation and/or excessive activation of naive B-cells. Hence, the localization of a mutation in stem II of U4atac snRNA, as observed in another RNU4ATAC-opathy with immunodeficiency, that is, Roifman syndrome (RFMN), is not required for the occurrence of an immune deficiency. Finally, we emphasize the importance of considering immunodeficiency in MOPDI management to reduce the risk of serious infectious episodes.

Immune Profiling Panel Gene Set Identifies Critically Ill Patients With Low Monocyte Human Leukocyte Antigen-DR Expression: Preliminary Results From the REAnimation Low Immune Status Marker (REALISM) Study.

OBJECTIVES: There is a crucial unmet need for biomarker-guided diagnostic and prognostic enrichment in clinical trials evaluating immune modulating therapies in critically ill patients. Low monocyte expression of human leukocyte antigen-DR (mHLA-DR), considered as a reference surrogate to identify immunosuppressed patients, has been proposed for patient stratification in immunostimulation approaches. However, its widespread use in clinic has been somewhat hampered by technical constraints inherent to flow cytometry technology. The objective of the present study was to evaluate the ability of a prototype multiplex polymerase chain reaction tool (immune profiling panel [IPP]) to identify immunosuppressed ICU patients characterized by a low mHLA-DR expression. DESIGN: Retrospective observational cohort study. SETTING: Adult ICU in a University Hospital, Lyon, France. PATIENTS: Critically ill patients with various etiologies enrolled in the REAnimation Low Immune Status Marker study (NCT02638779). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: mHLA-DR and IPP data were obtained from 1,731 blood samples collected from critically ill patients with various etiologies and healthy volunteers. A partial least square regression model combining the expression levels of IPP markers was trained and used for the identification of samples from patients presenting with evidence of immunosuppression, defined here as mHLADR less than 8,000 antibodies bound per cell (AB/C). The IPP gene set had an area under the receiver operating characteristic curve (AUC) of 0.86 (95% CI 0.83-0.89) for the identification of immunosuppressed patients. In addition, when applied to the 123 patients still in the ICU at days 5-7 after admission, IPP similarly enriched the number of patients with ICU-acquired infections in the immunosuppressed group (26%), in comparison with low mHLA-DR (22%). CONCLUSIONS: This study reports on the potential of the IPP gene set to identify ICU patients presenting with mHLA-DR less than 8,000 AB/C. Upon further optimization and validation, this molecular tool may help in the stratification of patients that could benefit from immunostimulation in the context of personalized medicine.

APOB CRISPR-Cas9 Engineering in Hypobetalipoproteinemia: A Promising Tool for Functional Studies of Novel Variants.

Hypobetalipoproteinemia is characterized by LDL-cholesterol and apolipoprotein B (apoB) plasma levels below the fifth percentile for age and sex. Familial hypobetalipoproteinemia (FHBL) is mostly caused by premature termination codons in the APOB gene, a condition associated with fatty liver and steatohepatitis. Nevertheless, many families with a FHBL phenotype carry APOB missense variants of uncertain significance (VUS). We here aimed to develop a proof-of-principle experiment to assess the pathogenicity of VUS using the genome editing of human liver cells. We identified a novel heterozygous APOB-VUS (p.Leu351Arg), in a FHBL family. We generated APOB knock-out (KO) and APOB-p.Leu351Arg knock-in Huh7 cells using CRISPR-Cas9 technology and studied the APOB expression, synthesis and secretion by digital droplet PCR and ELISA quantification. The APOB expression was decreased by 70% in the heterozygous APOB-KO cells and almost abolished in the homozygous-KO cells, with a consistent decrease in apoB production and secretion. The APOB-p.Leu351Arg homozygous cells presented with a 40% decreased APOB expression and undetectable apoB levels in cellular extracts and supernatant. Thus, the p.Leu351Arg affected the apoB secretion, which led us to classify this new variant as likely pathogenic and to set up a hepatic follow-up in this family. Therefore, the functional assessment of APOB-missense variants, using gene-editing technologies, will lead to improvements in the molecular diagnosis of FHBL and the personalized follow-up of these patients.

Monocyte CD169 expression in COVID-19 patients upon intensive care unit admission.

During the second surge of COVID-19 in France (fall 2020), we assessed the expression of monocyte CD169 (i.e., Siglec-1, one of the numerous IFN-stimulated genes) upon admission to intensive care units of 45 patients with RT-PCR-confirmed SARS-CoV2 pulmonary infection. Overall, CD169 expression was strongly induced on circulating monocytes of COVID-19 patients compared with healthy donors and patients with bacterial sepsis. Beyond its contribution at the emergency department, CD169 testing may be also helpful for patients' triage at the ICU to rapidly reinforce suspicion of COVID-19 etiology in patients with acute respiratory failure awaiting for PCR results for definitive diagnosis.

Clinical significance of a single cerebrospinal fluid immunoglobulin band: A retrospective study.

BACKGROUND: To demonstrate an inflammatory process in the central nervous system, the presence of at least two immunoglobulin (Ig) bands in the cerebrospinal fluid (CSF) is required. So far, the presence of a single abnormal Ig band is considered as negative. OBJECTIVE: The objective was to assess retrospectively the significance of a single CSF Ig band in clinical practice. METHODS AND RESULTS: Out of 10,286 CSF analyses, we retained 214 results with single Ig. An inflammatory neurological disorder was diagnosed in 41% of patients. CONCLUSION: Despite a modest sensitivity, the presence of a single CSF Ig band may be a biomarker of an inflammatory mechanism and, as such, may prompt the clinician to repeat the analysis when the clinical context remains suggestive.

Monocyte HLA-DR Measurement by Flow Cytometry in COVID-19 Patients: An Interim Review.

Several months after the sudden emergence of SARS-CoV-2 and COVID-19, the understanding of the appropriate host immune response to a virus totally unknown of human immune surveillance is still of major importance. By international definition, COVID-19 falls in the scope of septic syndromes (organ dysfunction due to dysregulated host response to an infection) in which immunosuppression is a significant driver of mortality. Sepsis-induced immunosuppression is mostly defined and monitored by the measurement of decreased expression of HLA-DR molecules on circulating monocytes (mHLA-DR). In this interim review, we summarize the first mHLA-DR results in COVID-19 patients. In critically ill patients, results homogenously indicate a decreased mHLA-DR expression, which, along with profound lymphopenia and other functional alterations, is indicative of a status of immunosuppression. © 2020 International Society for Advancement of Cytometry.

Septic Shock Shapes B Cell Response toward an Exhausted-like/Immunoregulatory Profile in Patients.

Septic shock is accompanied by the development of immune dysfunctions whose intensity and duration are associated with increased risk of secondary infections and mortality. Although B lymphocytes play a pivotal role in the immune response to infections, no comprehensive exploration of circulating B cell status has been performed during the immunosuppressive phase of septic shock. Thus, our aim was to extensively characterize the phenotype and function of B cells in septic shock, including IL-10 production. Circulating B lymphocyte phenotype and function were evaluated by flow cytometry on fresh whole blood and after ex vivo stimulation in adult septic shock patients sampled at day 1, 3, and 6 after the onset of shock. The circulating B cell number was reduced in septic shock patients, whereas the B cell proportion among total lymphocytes was increased. The remaining circulating B lymphocytes presented with decreased MHC class II expression and increased CD21low CD95high exhausted-like phenotype but showed no change in maturation status. Circulating B cell functions were markedly altered after sepsis with reduced ex vivo activation and proliferation capacities. Finally, B cell response after septic shock was characterized by a clear plasmacytosis and an increased IL-10 production in remaining B cells from patients after ex vivo stimulation. During the sepsis-induced immunosuppression phase, B cell response is altered and is oriented toward an exhausted-like/immunoregulatory profile. Further studies are now needed to confirm the immunoregulatory properties of B lymphocytes and evaluate their role in sepsis-induced immunosuppression.

Monocytic HLA-DR expression kinetics in septic shock patients with different pathogens, sites of infection and adverse outcomes.

BACKGROUND: Decreased monocytic (m)HLA-DR expression is the most studied biomarker of sepsis-induced immunosuppression. To date, little is known about the relationship between sepsis characteristics, such as the site of infection, causative pathogen, or severity of disease, and mHLA-DR expression kinetics. METHODS: We evaluated mHLA-DR expression kinetics in 241 septic shock patients with different primary sites of infection and pathogens. Furthermore, we used unsupervised clustering analysis to identify mHLA-DR trajectories and evaluated their association with outcome parameters. RESULTS: No differences in mHLA-DR expression kinetics were found between groups of patients with different sites of infection (abdominal vs. respiratory, p = 0.13; abdominal vs. urinary tract, p = 0.53) and between pathogen categories (Gram-positive vs. Gram-negative, p = 0.54; Gram-positive vs. negative cultures, p = 0.84). The mHLA-DR expression kinetics differed between survivors and non-survivors (p < 0.001), with an increase over time in survivors only. Furthermore, we identified three mHLA-DR trajectories ('early improvers', 'delayed or non-improvers' and 'decliners'). The probability for adverse outcome (secondary infection or death) was higher in the delayed or non-improvers and decliners vs. the early improvers (delayed or non-improvers log-rank p = 0.03, adjusted hazard ratio 2.0 [95% CI 1.0-4.0], p = 0.057 and decliners log-rank p = 0.01, adjusted hazard ratio 2.8 [95% CI 1.1-7.1], p = 0.03). CONCLUSION: Sites of primary infection or causative pathogens are not associated with mHLA-DR expression kinetics in septic shock patients. However, patients showing delayed or no improvement in or a declining mHLA-DR expression have a higher risk for adverse outcome compared with patients exhibiting a swift increase in mHLA-DR expression. Our study signifies that changes in mHLA-DR expression over time, and not absolute values or static measurements, are of clinical importance in septic shock patients.

How Clinical Flow Cytometry Rebooted Sepsis Immunology.

On May 2017, the World Health Organization (WHO) recognized sepsis as a global health priority by adopting a resolution to improve the prevention, diagnosis, and management of this deadly disease. While it has long been known that sepsis deeply perturbs immune homeostasis by inducing a tremendous systemic inflammatory response, pivotal observations based on clinical flow cytometry indicate that sepsis indeed initiates a more complex immune response that varies over time, with the concomitant occurrence of both pro- and anti-inflammatory mechanisms. As a resultant, some septic patients enter a stage of protracted immunosuppression. This paved the way for immunostimulation approaches in sepsis. Clinical flow cytometry permitted this evolution by drawing a new picture of pathophysiology and reshaping immune trajectories in patients. Additional information from cytometry by time of flight mass cytometry and other high-dimensional flow cytometry platform should rapidly enrich our understanding of this complex disease. This review reports on landmarks of clinical flow cytometry in sepsis and how this single-cell analysis technique permitted to breach the wall of decades of unfruitful anti-inflammatory-based clinical trials in sepsis. © 2019 International Society for Advancement of Cytometry.

IL-7 and Its Beneficial Role in Sepsis-Induced T Lymphocyte Dysfunction.

Sepsis, defined as life-threatening organ dysfunction caused by dysregulated host response to infection, has recently been acknowledged as a worldwide health priority. Sepsis remains the leading cause of mortality in intensive care units and accounts for 6 million deaths every year. Few therapeutic options targeting host immune response in sepsis have demonstrated their efficacy so far. Increasing evidence suggests that a profound immune suppression develops following sepsis, affecting innate and adaptive immune response, of which intensity and duration is associated with increased risk of death and nosocomial infection. Immunostimulant treatments are thus now evaluated in sepsis, and recombinant human IL-7 (rhIL-7) represents a promising candidate. rhIL-7 has been evaluated in several clinical trials in patients with altered lymphocytic responses (HIV infection, hematopoietic stem cell transplantation, and cancer). Recent studies in animal models and in patients' samples ex vivo demonstrated its efficacy in improving sepsis-induced T cell alterations. Finally, the first clinical trial evaluating rhIL-7 in septic shock patients has just been published. This review will discuss the use of rhIL-7 to treat sepsis-induced T cell dysfunction by introducing the pathophysiology of sepsis and sepsis-related lymphocyte alterations before focusing on rhIL-7 and its potential use of as a therapeutic intervention in patients.

TCR activation mimics CD127lowPD-1high phenotype and functional alterations of T lymphocytes from septic shock patients.

BACKGROUND: Sepsis is the leading cause of mortality for critically ill patients worldwide. Patients develop T lymphocyte dysfunctions leading to T-cell exhaustion associated with increased risk of death. As interleukin-7 (IL-7) is currently tested in clinical trials to reverse these dysfunctions, it is important to evaluate the expression of its specific CD127 receptor on the T-cell surface of patients with septic shock. Moreover, the CD127lowPD-1high phenotype has been proposed as a T-cell exhaustion marker in chronic viral infections but has never been evaluated in sepsis. The objective of this study was first to evaluate CD127 and CD127lowPD-1high phenotype in septic shock in parallel with functional T-cell alterations. Second, we aimed to reproduce septic shock-induced T-cell alterations in an ex vivo model. METHODS: CD127 expression was followed at the protein and mRNA levels in patients with septic shock and healthy volunteers. CD127lowPD-1high phenotype was also evaluated in parallel with T-cell functional alterations after ex vivo activation. To reproduce T-cell alterations observed in patients, purified T cells from healthy volunteers were activated ex vivo and their phenotype and function were evaluated. RESULTS: In patients, neither CD127 expression nor its corresponding mRNA transcript level was modified compared with normal values. However, the percentage of CD127lowPD-1high T cells was increased while T cells also presented functional alterations. CD127lowPD-1high T cells co-expressed HLA-DR, an activation marker, suggesting a role for T-cell activation in the development of this phenotype. Indeed, T-cell receptor (TCR) activation of normal T lymphocytes ex vivo reproduced the increase of CD127lowPD-1high T cells and functional alterations following a second stimulation, as observed in patients. Finally, in this model, as observed in patients, IL-7 could improve T-cell proliferation. CONCLUSIONS: The proportion of CD127lowPD-1high T cells in patients was increased compared with healthy volunteers, although no global CD127 regulation was observed. Our results suggest that TCR activation participates in the occurrence of this T-cell population and in the development of T-cell alterations in septic shock. Furthermore, we provide an ex vivo model for the investigation of the pathophysiology of sepsis-induced T-cell immunosuppression and the testing of innovative immunostimulant treatments.

Decreased intra-lymphocyte cytokines measurement in septic shock patients: A proof of concept study in whole blood.

Functional testing protocols are thought to be the gold standard for the exploration of the immune system. However, in terms of routine analysis, they present numerous drawbacks and consequently their use is mainly limited to research applications. In the clinical context of septic shock, characterized by marked lymphocyte alterations, a new approach for lymphocyte intracellular cytokine measurement in whole blood upon was evaluated in a proof-of-concept study. Following lymphocyte activation, simultaneous intracellular labeling of Interferon-γ (IFN-γ), Tumor Necrosis Factor-α (TNF-α), and Interleukin-2 (IL-2) was performed in CD4+ and CD8+ T cells (identified by surface marking). The analysis was carried out by flow cytometry (6 colors). Results obtained in septic patients (n=22) were compared to those of healthy volunteers (n=8). Independently of lymphopenia, there were significant differences between groups. In particular there was significant decrease in the production of IL-2 and TNF-α in septic patients, while the production of IFN-γ was not significantly altered. Polyfunctional results showed that patients presented with increased percentages of triple negative lymphocytes. In contrast, volunteers had higher proportions of triple positive cells. The approach could be performed in a robust and consistent way, taking 4.5h to complete. Moreover, clear differences could be observed between clinical groups with this modified method. These characteristics illustrate the potential of this novel whole blood protocol for clinical applications. However, further research is required to determine the applicability compared to alternative test and to evaluate clinical performances in larger cohorts of patients.

Sepsis in PD-1 light.

Increasing evidence suggests that after the first pro-inflammatory hours, sepsis is characterized by the occurrence of severe immunosuppression. Several mechanisms have been reported to participate in sepsis-induced immune alterations affecting both innate and adaptive immunity. Of these, the concept of 'cell exhaustion' has gained a lot of interest because some parallels can be drawn with the cancer field in which immunostimulation approaches through blocking immune checkpoints currently obtain remarkable success. Herein, perspectives regarding co-inhibitory receptors' contribution to lymphocyte exhaustion in sepsis will be discussed in the context of a recently published study investigating the potential of PD-1 molecule expression (i.e. PD-1 on lymphocytes, PD-L1 on monocytes) to predict mortality in septic shock patients.

Monitoring monocyte HLA-DR expression and CD4 + T lymphocyte count in dexamethasone-treated severe COVID-19 patients.

BACKGROUND: A 10-day dexamethasone regimen has emerged as the internationally adopted standard-of-care for severe COVID-19 patients. However, the immune response triggered by SARS-CoV-2 infection remains a complex and dynamic phenomenon, leading to various immune profiles and trajectories. The immune status of severe COVID-19 patients following complete dexamethasone treatment has yet to be thoroughly documented. RESULTS: To analyze monocyte HLA-DR expression (mHLA-DR) and CD4 + T lymphocyte count (CD4) in critically ill COVID-19 patients after a dexamethasone course and evaluate their association with 28-day ICU mortality, adult COVID-19 patients (n = 176) with an ICU length of stay of at least 10 days and under dexamethasone treatment were included. Associations between each biomarker value (or in combination) measured at day 10 after ICU admission and 28-day mortality in ICU were evaluated. At day 10, the majority of patients presented decreased values of both parameters. A significant association between low mHLA-DR and 28-day mortality was observed. This association remained significant in a multivariate analysis including age, comorbidities or pre-existing immunosuppression (adjusted Hazard ratio (aHR) = 2.86 [1.30-6.32], p = 0.009). Similar results were obtained with decreased CD4 + T cell count (aHR = 2.10 [1.09-4.04], p = 0.027). When combining these biomarkers, patients with both decreased mHLA-DR and low CD4 presented with an independent and significant elevated risk of 28-day mortality (i.e., 60%, aHR = 4.83 (1.72-13.57), p = 0.001). CONCLUSIONS: By using standardized immunomonitoring tools available in clinical practice, it is possible to identify a subgroup of patients at high risk of mortality at the end of a 10-day dexamethasone treatment. This emphasizes the significance of integrating immune monitoring into the surveillance of intensive care patients in order to guide further immumodulation approaches.

Persistent NLRP3 inflammasome activation is associated with delayed immunosuppression in septic patients.

Sepsis triggers a complex response marked by the simultaneous presence of proinflammatory and immunosuppressive elements, disrupting the mechanisms intended to maintain homeostasis. While the NLRP3 inflammasome has been demonstrated to contribute to the inflammatory side, its connection with delayed sepsis-induced immunosuppression remains unexplored. The present objective was to concomitantly and prospectively assess NLRP3 activation (IL-1ß, IL-18, and soluble receptors) and features of immune failure (IL-10, mHLA-DR, myeloid-derived suppressor cells) in septic patients. To validate our findings, we conducted a transcriptomic analysis of mRNA of NLRP3-related genes (IL-18R1, IL-1R2) on an additional cohort of 107 patients. Two distinct endotypes were identified. One cluster displayed moderate inflammation rapidly returning to normal values, while the other exhibited a higher inflammatory response persisting until day 28, which was associated with persistent marked immunosuppression and higher 28-d mortality. Identifying endotypes with different pro/anti-inflammatory trajectories could hold important clinical implications for the management of sepsis.

Joint modeling of monocyte HLA-DR expression trajectories predicts 28-day mortality in severe SARS-CoV-2 patients.

The recent SarsCov2 pandemic has disrupted healthcare system notably impacting intensive care units (ICU). In severe cases, the immune system is dysregulated, associating signs of hyperinflammation and immunosuppression. In the present work, we investigated, using a joint modeling approach, whether the trajectories of cellular immunological parameters were associated with survival of COVID-19 ICU patients. This study is based on the REA-IMMUNO-COVID cohort including 538 COVID-19 patients admitted to ICU between March 2020 and May 2022. Measurements of monocyte HLA-DR expression (mHLA-DR), counts of neutrophils, of total lymphocytes, and of CD4+ and CD8+ subsets were performed five times during the first month after ICU admission. Univariate joint models combining survival at day 28 (D28), hospital discharge and longitudinal analysis of those biomarkers' kinetics with mixed-effects models were performed prior to the building of a multivariate joint model. We showed that a higher mHLA-DR value was associated with a lower risk of death. Predicted mHLA-DR nadir cutoff value that maximized the Youden index was 5414 Ab/C and led to an AUC = 0.70 confidence interval (95%CI) = [0.65; 0.75] regarding association with D28 mortality while dynamic predictions using mHLA-DR kinetics until D7, D12 and D20 showed AUCs of 0.82 [0.77; 0.87], 0.81 [0.75; 0.87] and 0.84 [0.75; 0.93]. Therefore, the final joint model provided adequate discrimination performances at D28 after collection of biomarker samples until D7, which improved as more samples were collected. After severe COVID-19, decreased mHLA-DR expression is associated with a greater risk of death at D28 independently of usual clinical confounders.