Persistent lymphopenia is a risk factor for ICU-acquired infections and for death in ICU patients with sustained hypotension at admission

ICU-acquired infections in immunocompromised patients

Immunocompromised patients account for an increasing proportion of the typical intensive care unit (ICU) case-mix. Because of the increased availability of new drugs for cancer and auto-immune diseases, and improvement in the care of the most severely immunocompromised ICU patients (including those with hematologic malignancies), critically ill immunocompromised patients form a highly heterogeneous patient population. Furthermore, a large number of ICU patients with no apparent immunosuppression also harbor underlying conditions altering their immune response, or develop ICU-acquired immune deficiencies as a result of sepsis, trauma or major surgery. While infections are associated with significant morbidity and mortality in immunocompromised critically ill patients, little specific data are available on the incidence, microbiology, management and outcomes of ICU-acquired infections in this population. As a result, immunocompromised patients are usually excluded from trials and guidelines on the management of ICU-acquired infections. The most common ICU-acquired infections in immunocompromised patients are ventilator-associated lower respiratory tract infections (which include ventilator-associated pneumonia and tracheobronchitis) and bloodstream infections. Recently, several large observational studies have shed light on some of the epidemiological specificities of these infections-as well as on the dynamics of colonization and infection with multidrug-resistant bacteria-in these patients, and these will be discussed in this review. Immunocompromised patients are also at higher risk than non-immunocompromised hosts of fungal and viral infections, and the diagnostic and therapeutic management of these infections will be covered. Finally, we will suggest some important areas of future investigation.

[The Immune System of the Critically Ill Patient]

Critically ill patients often experience a dysregulated immune response, leading to immune dysfunction. Sepsis, trauma, severe infections, and certain medical conditions can trigger a state of systemic inflammation, known as the cytokine storm. This hyperactive immune response can cause collateral damage to healthy tissues and organs, exacerbating the patient's condition. On the other hand, some critically ill patients may suffer from immune paralysis which can increase the risk of nosocomial infections.Fever is an evolutionary adaptation that evolved as an effective defense mechanism to fight invading pathogens. By raising body temperature, fever enhances the immune response, inhibits pathogen growth, promotes recovery, and aids in the formation of immune memory. Understanding the role of fever in the context of immune defense is crucial for optimizing medical interventions and supporting the body's natural ability to combat infections.Future Directions: Advancements in immunology research and technology hold promise for better understanding the immune system's complexities in critically ill patients. Personalized medicine approaches may be developed to tailor therapies to individual patients based on their immune profile, optimizing treatment outcomes. Based on recent studies prognostic parameters such as lymphocyte count, IL-10 concentration and mHLA-DR expression can be used to stratify the immunological response pattern in septic patients.Conclusion: The immune system's response in critically ill patients is a multifaceted process, involving intricate interactions between various immune cells, cytokines, and organs. Striking the delicate balance between immune activation and suppression remains a significant challenge in clinical practice. Continued research and therapeutic innovations are vital to improve patient outcomes and reduce the burden of critical illness on healthcare systems.

Characteristics and Clinical Prognosis of Septic Patients With Persistent Lymphopenia

Background: Septic patients with persistent lymphopenia may be in an immunosuppressed state. Therefore, we evaluated and compared the clinical characteristics and outcomes of septic patients with persistent lymphopenia (≥2d) and those with nonpersistent lymphopenia. Methods: A retrospective cohort study was designed. A total of 1306 patients with sepsis who were attended to the First Affiliated Hospital of Dalian Medical University from March 2016 to August 2022 were included. The primary clinical outcome was 90d mortality. The secondary clinical outcomes were the length of stay, hospital mortality, 28d mortality, the incidence of secondary infection, and differences in clinical characteristics. Results: Among 1306 patients with sepsis, 913 (69.9%) patients developed persistent lymphopenia. Compared with patients with nonpersistent lymphopenia, patients with persistent lymphocytopenia were admitted to intensive care unit (75.7% vs 52.7%, P < .05), treated with mechanical ventilation (67.6% vs 39.2%, P < .05), positive rate of microbial culture pathogens (86.7% vs 71.2%, P < .05), SOFA [8.0 (6.0-10.0) vs 6.0 (4.0-8.0), P < .05], length of stay [17.0d (12.0-27.0) vs 13.0d (10.0-21.0), P < .05], hospital mortality (37.7% vs 24.2%, P < .05), 28d mortality (38.0% vs 22.9%, P < .05), and 90d mortality (51.2% vs 31.3%, P < .05) were higher. As the duration of lymphocytopenia increased, so did the mortality rate in hospital. In addition, the onset time of persistent lymphopenia was not associated with SOFA. But we found that the frequency of persistent lymphopenia during hospitalization was positively associated with SOFA. Conclusion: Septic patients with persistent lymphopenia have higher mortality, worse conditions, increased risk of secondary infection, and poor prognosis regardless of shock.

Prediction of pulmonary aspergillosis in patients with ventilator-associated pneumonia

BACKGROUND

Predictors of ICU-acquired pulmonary aspergillosis (IPA) are not well-established in critically ill patients with ventilator-associated pneumonia (VAP), making IPA commonly misdiagnosed and anti-fungal therapy delayed. We aimed to develop a clinical score for prediction of IPA among patients with VAP.

METHODS

Mechanically ventilated patients who developed VAP in 4 ICUs in Bretagne, Western France, were included. The score was constructed in a learning cohort, based on predictors of IPA in logistic regression model, and validated in a validation cohort.

RESULTS

Among 1636 mechanically ventilated patients, 215 developed VAP but only 39 developed IPA (4 possible and 35 probable/putative) (18%). Most cases (31/39) were documented through a positive broncho-alveolar sample culture. Independent predictors of IPA were immunodepression (including onco-hematological disorder, immunomodulatory treatment, solid organ transplant, neutropenia < 0.5G/L and high-dose steroids ≥ 1 mg/kg/day of prednisolone equivalent) (p = 0.001; score = 1 point) and lymphocyte count at admission < 0.8 G/L (p = 0.019; score = 1 point). Operational values of the predictive score in the learning/validation cohort were 50%/52% sensitivity and 90%/87% specificity, respectively, for high PiPa score (score = 2) and 94%/91% sensitivity and 44%/46% specificity, respectively, for moderate PiPa score (score = 1). Finally, the AUC for the prediction of IPA was 0.783 in the learning cohort and 0.770 in the validation cohort.

CONCLUSIONS

We evaluated a clinical score with good predictive value which may help to predict IPA in patient with VAP. External validation will be needed to confirm our preliminary findings.

Low lymphocyte to high-density lipoprotein ratio predicts mortality in sepsis patients

Background

The lymphocyte-to-high-density lipoprotein (HDL) ratio (LHR) is associated with both inflammation and immunity, and may have the potential to predict the prognosis of sepsis. Our study aimed to evaluate the relationship between LHR and sepsis-related mortality.

Methods

We collected data from the Medical Information Mart for Intensive Care IV (MIMIC-IV, version 2.2) database by targeting patients who met the Sepsis-3 criteria and recorded the absolute values of lymphocytes and HDL after admission. We then used restricted cubic splines based on logistic regression to simulate the relationship between the LHR and 90-day mortality. Subsequently, the hazardous threshold was derived based on the mortality curve, and further evaluations were performed using different methods and data sources for hazardous threshold.

Results

We ultimately included 1027 eligible patients from the MIMIC-IV database and described the nonlinear relationship between LHR and 90-day mortality. Based on the curve, an LHR of ≤ 0.6 indicated harmful threshold, and the odds ratio for mortality was 1.74 (P=0.001). The outperforming hazard was particularly marked in patients with chronic lung disease and remained consistent after adjusting for baseline data and validating multiple data sources.

Conclusions

The LHR has prognostic value in patients with sepsis, and an LHR ≤ 0.6 is a deleterious load that increases mortality.

Identification of potential hub genes linked to immune and metabolic alterations in postoperative systemic inflammatory dysregulation

Background

Postoperative systemic inflammatory dysregulation (PSID) is characterised by strongly interlinked immune and metabolic abnormalities. However, the hub genes responsible for the interconnections between these two systemic alterations remain to be identified.

Methods

We analysed differentially expressed genes (DEGs) of individual peripheral blood nucleated cells in patients with PSID (n = 21, CRP > 250 mg/L) and control patients (n = 25, CRP < 75 mg/L) following major abdominal surgery, along with their biological functions. Correlation analyses were conducted to explore the interconnections of immune-related DEGs (irDEGs) and metabolism-related DEGs (mrDEGs). Two methods were used to screen hub genes for irDEGs and mrDEGs: we screened for hub genes among DEGs via 12 algorithms using CytoHubba in Cytoscape, and also screened for hub immune-related and metabolic-related genes using weighted gene co-expression network analysis. The hub genes selected were involved in the interaction between changes in immunity and metabolism in PSID. Finally, we validated our results in mice with PSID to confirm the findings.

Results

We identified 512 upregulated and 254 downregulated DEGs in patients with PSID compared with controls. Gene enrichment analysis revealed that DEGs were significantly associated with immune- and metabolism-related biological processes and pathways. Correlation analyses revealed a close association between irDEGs and mrDEGs. Fourteen unique hub genes were identified via 12 screening algorithms using CytoHubba in Cytoscape and via weighted gene co-expression network analysis. Among these, CD28, CD40LG, MAPK14, and S100A12 were identified as hub genes among both immune- and metabolism-related genes; these genes play a critical role in the interaction between alterations in immunity and metabolism in PSID. The experimental results also showed that the expression of these genes was significantly altered in PSID mice.

Conclusion

This study identified hub genes associated with immune and metabolic alterations in patients with PSID and hub genes that link these alterations. These findings provide novel insights into the mechanisms underlying immune and metabolic interactions and new targets for clinical treatment can be proposed on this basis.

The Association Between Absolute Lymphocyte Count and Long-Term Mortality in Critically Ill Medical Patients: Propensity Score-Based Analyses

Objective

Absolute lymphocyte count (ALC) has been implicated with short-term outcomes in a number of diseases, and we aimed to investigate the association between week-one ALC and long-term mortality in patients who were admitted to the medical intensive care units (ICUs).

Methods

We enrolled patients who were admitted to the medical ICUs at the Taichung Veterans General Hospital, a referral centre located in central Taiwan, between 2015 and 2020 to conduct this retrospective cohort study. The outcome of interest was long-term all-cause mortality, and hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated to determine the association. Furthermore, we employed propensity score-matching (PSM) and weighting techniques, consisting of inverse probability of treatment weighting (IPTW) and covariate balancing propensity score (CBPS), to confirm the association between ALC and mortality.

Results

A total of 5722 critically ill patients were enrolled, and the one-year mortality was 44.8%. The non-survivor group had a lower ALC (1549, 1027-2388 vs 1948, 1373-2743 counts/μL, p<0.01) compared with those in the survivor group. Cox regression showed that low ALC was independently associated with mortality (adjHR 1.091, 95% CI 1.050-1.134). Propensity score-based analyses demonstrated the robust association, with adjHRs in the original, PSM, IPTW, and CBPS populations of 1.327 (95% CI 1.224-1.438), 1.301 (95% CI 1.188-1.424), 1.292 (95% CI 1.186-1.407), and 1.297 (95% CI 1.191-1.412), respectively. Sensitivity analyses further showed that the association between low ALC and mortality existed in a dose-response manner.

Conclusion

We found that low ALC was associated with long-term mortality in critically ill patients; further studies are warranted to validate and translate these findings into clinical utility.

The association and prognostic value of systemic inflammatory response index with short and long-term mortality in patients with sepsis

This study evaluated the association and prognostic significance of the systemic inflammation response index (SIRI) with mortality in sepsis. In this cohort study, the sepsis patients were retrieved from the Medical Information Mart for Intensive Care III (MIMIC-III) and MIMIC-IV intensive care unit (ICU) databases. SIRI was calculated by using the neutrophil, monocyte, and lymphocyte counts. The outcomes were 28-day mortality, 1-year mortality, and 28 days to 1-year mortality. The Cox proportional hazards model with a hazard ratio (HR) and a 95% confidence interval (CI) was used to investigate the association and prognostic value of SIRI with mortality in sepsis. Subgroup analyses of the associations of SIRI with 28-day and 1-year mortality in sepsis were based on age, gender, Simplified Acute Physiology Score II (SAPSII), Sequential Organ Failure Assessment (SOFA), and presence or absence of septic shock. The receiver operating characteristic (ROC) curve was used to compare the predictive performances of SIRI, SOFA and SAPS II for mortality in sepsis. Of the 4239 patients included, 1339 patients suffered from 28-day mortality, 2085 patients suffering from 1-year mortality, and 746 (25.72%) suffered from 28 days to 1-year mortality. High SIRI levels exhibited higher risks of 28-day mortality (HR: 1.15, 95% CI: 1.03-1.29, P = .010), 1-year mortality (HR: 1.14, 95% CI: 1.04-1.24, P = .003), and 28 days to 1-year mortality (HR: 1.16, 95% CI: 1.01-1.35, P = .047) in sepsis. A higher SIRI was reported related to 28-day mortality and 1-year mortality in sepsis patients with female gender, with SOFA < 8, with SAPS II < 44, and in sepsis patients without sepsis shock. The AUC of SIRS, SOFA, and SAPS II in predicting 28-day mortality in sepsis were 0.726, 0.591, and 0.644, respectively. The AUC of SIRI in predicting 1-year mortality in sepsis was 0.761, higher than the AUC values of SOFA and SAPS II. A higher AUC value of SIRI compared with SOFA, and SAPS II in predicting 28 days to 1-year mortality was observed. Elevated SIRI was associated with an increased risk of mortality in sepsis. SIRI is an independent prognostic biomarker of mortality in sepsis.

Development and validation of prediction scores for the outcome associated with persistent inflammation, immunosuppression, and catabolism syndrome among patients with trauma

Background

Persistent inflammation, immunosuppression, and catabolism syndrome (PICS) has impacted on long-term prognosis of patients with trauma. We aimed to identify patients with trauma at risk of PICS-related complications early in the intensive care unit (ICU) course.

Methods

A single-center retrospective cohort study was conducted. All consecutive patients with trauma who had stayed in the ICU for >7 days were included in the study. We developed the prediction score for the incidence of PICS-related outcomes in the derivation cohort for the initial period and then evaluated in the validation cohort for the subsequent period. Other outcomes were also assessed using the score.

Results

In total, 170 and 133 patients were included in the derivation and validation cohorts, respectively. The prediction score comprised the variables indicating PICS presence, including a maximum value of C-reactive protein >15 mg/dL, minimum value of albumin <2.5 g/dL, and an episode of nosocomial infection for the first 7 days after admission. A score of 1 was assigned to each variable. The area under the receiver operating characteristic curve of the score to predict PICS incidence was 0.74 (95% CI 0.66 to 0.81) and 0.72 (95% CI 0.64 to 0.81) in the derivation and validation cohorts, respectively. The higher score was also significantly associated with a higher Sequential Organ Failure Assessment score at day 14, a longer duration of mechanical ventilation, a longer length of stay in ICU, and experienced multiple episodes of infection. Similar results were obtained in the validation cohort.

Conclusions

Our scoring system could predict the outcomes associated with PICS among patients with trauma. Because the score comprised the parameters measured for the first 7 days during the ICU course, it could contribute to identifying patients at a high risk of unfavorable outcome earlier.

Level of evidence

Multivariate prediction models; level IV.

GPX4 is a key ferroptosis biomarker and correlated with immune cell populations and immune checkpoints in childhood sepsis

Sepsis is the uncontrolled reaction of the body to infection-induced inflammation, which results in life-threatening multiple-organ dysfunction (MODS). Although the research on sepsis has advanced significantly in recent years, its pathophysiology remains entirely unknown. Ferroptosis is a new-fashioned type of programmed cell death that may have an impact on sepsis development. However, the precise mechanism still needs to be explored. In this paper, Four pediatric sepsis datasets [training datasets (GSE26378 and GSE26440) and validation datasets (GSE11755 and GSE11281)] were chosen through the GEO (Gene Expression Omnibus) database, and 63 differentially expressions of ferroptosis-relation-genes (DE-FRGs) were eventually discovered using bioinformatics investigation. Functional annotation was performed using GO and KEGG pathway enrichment analysis. Then, four Core-FRGs (FTH1, GPX4, ACSL1, and ACSL6) were extracted after the construction of the protein-protein interaction (PPI) network and the research of the MCODE module. Consequently, Hub-FRG (GPX4) was found using the validation datasets, and correlation exploration of immunity populations (neutrophils, r =  - 0.52; CD8 T-cells, r = 0.43) and immunity checkpoints (CD274, r =  - 0.42) was implemented. The usefulness of GPX4 as a marker in sepsis was assessed in a mouse model of sepsis. The findings demonstrate that GPX4 is a crucial biomarker and a new latent immunotherapy target for the prediction and therapy of pediatric sepsis.

Plasma protein biomarkers reflective of the host response in patients developing Intensive Care Unit-acquired pneumonia

BACKGROUND

Immune suppression has been implicated in the occurrence of pneumonia in critically ill patients. We tested the hypothesis that Intensive Care Unit (ICU)-acquired pneumonia is associated with broad host immune aberrations in the trajectory to pneumonia, encompassing inflammatory, endothelial and coagulation responses. We compared plasma protein biomarkers reflecting the systemic host response in critically ill patients who acquire a new pneumonia (cases) with those who do not (controls).

METHODS

We performed a nested case-control study in patients undergoing mechanical ventilation at ICU admission with an expected stay of at least 48 h enrolled in 30 hospitals in 11 European countries. Nineteen host response biomarkers reflective of key pathophysiological domains were measured in plasma obtained on study inclusion and day 7, and-in cases-on the day of pneumonia diagnosis.

RESULTS

Of 1997 patients, 316 developed pneumonia (15.8%) and 1681 did not (84.2%). Plasma protein biomarker analyses, performed in cases and a randomly selected subgroup of controls (1:2 ratio to cases, n = 632), demonstrated considerable variation across time points and patient groups. Yet, cases showed biomarker concentrations suggestive of enhanced inflammation and a more disturbed endothelial barrier function, both at study enrollment (median 2 days after ICU admission) and in the path to pneumonia diagnosis (median 5 days after ICU admission). Baseline host response biomarker aberrations were most profound in patients who developed pneumonia either shortly (< 5 days, n = 105) or late (> 10 days, n = 68) after ICU admission.

CONCLUSIONS

Critically ill patients who develop an ICU-acquired pneumonia, compared with those who do not, display alterations in plasma protein biomarker concentrations indicative of stronger proinflammatory, procoagulant and (injurious) endothelial cell responses.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02413242, posted April 9th, 2015.

Association between pretreatment lymphocyte count and efficacy of immune-enhancing therapy in acute necrotising pancreatitis: a post-hoc analysis of the multicentre, randomised, placebo-controlled TRACE trial

Background

Immune-enhancing thymosin alpha 1 (Tα1) therapy may reduce infected pancreatic necrosis (IPN) in acute necrotising pancreatitis (ANP). However, the efficacy might be impacted by lymphocyte count due to the pharmacological action of Tα1. In this post-hoc analysis, we tested the hypothesis that pre-treatment absolute lymphocyte count (ALC) determines whether patients with ANP benefit from Tα1 therapy.

Methods

A post-hoc analysis of data from a multicentre, double-blind, randomised, placebo-controlled trial testing the efficacy of Tα1 therapy in patients with predicted severe ANP was performed. Patients from 16 hospitals of China were randomised to receive a subcutaneous injection of Tα1 1.6 mg every 12 h for the frst 7 days and 1.6 mg once a day for the following 7 days or a matching placebo during the same period. Patients who discontinued the Tα1 regimen prematurely were excluded. Three subgroup analyses were conducted using the baseline ALC (at randomisation), and the group allocation was maintained as intention-to-treat. The primary outcome was the incidence of IPN 90 days after randomisation. The fitted logistic regression model was applied to identify the range of baseline ALC where Tα1 therapy could exert a maximum effect. The original trial is registered with ClinicalTrials.gov, NCT02473406.

Findings

Between March 18, 2017, and December 10, 2020, a total of 508 patients were randomised in the original trial, and 502 were involved in this analysis, with 248 in the Tα1 group and 254 in the placebo group. Across the three subgroups, there was a uniform trend toward more significant treatment effects in patients with higher baseline ALC. Within the subgroup of patients with baseline ALC≥0.8 × 10ˆ9/L (n = 290), the Tα1 therapy significantly reduced the risk of IPN (covariate adjusted risk difference, -0.12; 95% CI, -0.21,-0.02; p = 0.015). Patients with baseline ALC between 0.79 and 2.00 × 10ˆ9/L benefited most from the Tα1 therapy in reducing IPN (n = 263).

Interpretation

This post-hoc analysis found that the efficacy of immune-enhancing Tα1 therapy on the incidence of IPN may be associated with pretreatment lymphocyte count in patients with acute necrotising pancreatitis.

Funding

National Natural Science Foundation of China.

The double sides of NLRP3 inflammasome activation in sepsis

Sepsis is defined as a life-threatening organ dysfunction induced by a dysregulated host immune response to infection. Immune response induced by sepsis is complex and dynamic. It is schematically described as an early dysregulated systemic inflammatory response leading to organ failures and early deaths, followed by the development of persistent immune alterations affecting both the innate and adaptive immune responses associated with increased risk of secondary infections, viral reactivations, and late mortality. In this review, we will focus on the role of NACHT, leucin-rich repeat and pyrin-containing protein 3 (NLRP3) inflammasome in the pathophysiology of sepsis. NLRP3 inflammasome is a multiproteic intracellular complex activated by infectious pathogens through a two-step process resulting in the release of the pro-inflammatory cytokines IL-1β and IL-18 and the formation of membrane pores by gasdermin D, inducing a pro-inflammatory form of cell death called pyroptosis. The role of NLRP3 inflammasome in the pathophysiology of sepsis can be ambivalent. Indeed, although it might protect against sepsis when moderately activated after initial infection, excessive NLRP3 inflammasome activation can induce dysregulated inflammation leading to multiple organ failure and death during the acute phase of the disease. Moreover, this activation might become exhausted and contribute to post-septic immunosuppression, driving impaired functions of innate and adaptive immune cells. Targeting the NLRP3 inflammasome could thus be an attractive option in sepsis either through IL-1β and IL-18 antagonists or through inhibition of NLRP3 inflammasome pathway downstream components. Available treatments and results of first clinical trials will be discussed.

Blood count derangements after sepsis and association with post-hospital outcomes

Rationale

Predicting long-term outcomes in sepsis survivors remains a difficult task. Persistent inflammation post-sepsis is associated with increased risk for rehospitalization and death. As surrogate markers of inflammation, complete blood count parameters measured at hospital discharge may have prognostic value for sepsis survivors.

Objective

To determine the incremental value of complete blood count parameters over clinical characteristics for predicting 90-day outcomes in sepsis survivors.

Methods

Electronic health record data was used to identify sepsis hospitalizations at United States Veterans Affairs hospitals with live discharge and relevant laboratory data (2013 to 2018). We measured the association of eight complete blood count parameters with 90-day outcomes (mortality, rehospitalization, cause-specific rehospitalizations) using multivariable logistic regression models.

Measurements and main results

We identified 155,988 eligible hospitalizations for sepsis. Anemia (93.6%, N=142,162) and lymphopenia (28.1%, N=29,365) were the most common blood count abnormalities at discharge. In multivariable models, all parameters were associated with the primary outcome of 90-day mortality or rehospitalization and improved model discrimination above clinical characteristics alone (likelihood ratio test, p<0.02 for all). A model including all eight parameters significantly improved discrimination (AUROC, 0.6929 v. 0.6756) and reduced calibration error for the primary outcome. Hemoglobin had the greatest prognostic separation with a 1.5 fold increased incidence of the primary outcome in the lowest quintile (7.2-8.9 g/dL) versus highest quintile (12.70-15.80 g/dL). Hemoglobin and neutrophil lymphocyte ratio provided the most added value in predicting the primary outcome and 90-day mortality alone, respectively. Absolute lymphocyte count added little value in predicting 90-day outcomes.

Conclusions

The incorporation of discharge complete blood count parameters into prognostic scoring systems could improve prediction of 90-day outcomes. Hemoglobin had the greatest prognostic value for the primary composite outcome of 90-day rehospitalization or mortality. Absolute lymphocyte count provided little added value in multivariable model comparisons, including for infection- or sepsis-related rehospitalization.

Early mean absolute lymphocyte count in acute necrotizing pancreatitis is associated with infected pancreatic necrosis

OBJECTIVES

Peripheral absolute lymphocyte count (ALC) has the potential to predict infected pancreatic necrosis (IPN), but requires verification. This study aimed to assess whether early mean absolute lymphocyte count is associated with the development of IPN in ANP patients using pooled data from a multicenter, randomized controlled trial and a retrospective study.

METHODS

The study subjects are from the TRACE trial and a single-center cohort study. ALC during the first seven days was used to define early mean ALC. The entire cohort was then divided into quartiles of early mean ALC. Multivariable Cox proportional hazards regression (MCPHR) model was used to assess the association between early mean ALC and 90-day IPN.

RESULTS

A total of 660 patients (median age, 44 years; 63.8 % males) were included and 157 (23.8 %) developed IPN within a 90-day period. The median (interquartile range, IQR) of the early mean ALC is 1.07 (0.80-1.36). All the study subjects were evenly divided into 4 groups: quartile-1 (0.33-0.79*10^9/L), quartile-2 (0.80-1.06*10^9/L), quartile-3 (1.07-1.36*10^9/L) and quartile-4 (1.37-4.01*10^9/L). The incidence of 90-day IPN was 38.3 %, 25.7 %, 19.2 % and 12.2 % for each group, respectively. In the MCPHR model, the lowest early mean ALC (quartile-1) was found to be an independent risk factor of 90-day IPN with a hazard ratio (95 %CI) of 2.21 (1.28-3.81) compared to the highest mean ALC(quartile-4) group.

CONCLUSION

Among patients with ANP, early mean ALC was significantly associated with the development of IPN. Preventive strategies should be considered in patients with reduced ALC.

Expert consensus on the monitoring and treatment of sepsis-induced immunosuppression

Emerged evidence has indicated that immunosuppression is involved in the occurrence and development of sepsis. To provide clinical practice recommendations on the immune function in sepsis, an expert consensus focusing on the monitoring and treatment of sepsis-induced immunosuppression was developed. Literature related to the immune monitoring and treatment of sepsis were retrieved from PubMed, Web of Science, and Chinese National Knowledge Infrastructure to design items and expert opinions were collected through an online questionnaire. Then, the Delphi method was used to form consensus opinions, and RAND appropriateness method was developed to provide consistency evaluation and recommendation levels for consensus opinions. This consensus achieved satisfactory results through two rounds of questionnaire survey, with 2 statements rated as perfect consistency, 13 as very good consistency, and 9 as good consistency. After summarizing the results, a total of 14 strong recommended opinions, 8 weak recommended opinions and 2 non-recommended opinions were produced. Finally, a face-to-face discussion of the consensus opinions was performed through an online meeting, and all judges unanimously agreed on the content of this consensus. In summary, this expert consensus provides a preliminary guidance for the monitoring and treatment of immunosuppression in patients with sepsis.

Prevalence and outcome of lymphopenia in the Paediatric Intensive Care Unit: A prospective observational study

AIM

Leukopenia (lymphopenia or neutropenia) may be an important marker of altered immunity and risk in children with critical illness. We aimed to evaluate the prevalence, course, and outcome of leukopenia in children admitted to Paediatric Intensive Care Unit (PICU).

METHODS

All consecutive children (n = 200) admitted to PICU for any reason except malignancy or pre-existing immune deficiency were enrolled during June-August 2018.

RESULTS

Median (interquartile range) age was 2.2 (0.6-8.5) years. About 52% (n = 103) had undergone a surgical procedure; 34% (n = 68) being cardiac surgery. Among medical illnesses, respiratory disorders were the most common (n = 39, 20%). Laboratory confirmed infections were present in 63 (31.5%) children. Leukopenia was identified in 135 (67.5%) children in the first week; 117 (58.5%) had only lymphopenia, 16 (8%) had both lymphopenia and neutropenia, and 2 (1%) had only neutropenia. In 69 children who had follow-up blood counts, lymphopenia resolved in 33 (48%) within 48 h and in another 20 (29%) by 4 days, and in a further 10 (14%) by 7 days. Children with lymphopenia had higher frequency of cardiac surgery, longer cardiopulmonary bypass time, greater need for invasive ventilation and vasopressor/inotrope therapy, and a higher probability of organ failure on day 4 and longer hospital stay.

CONCLUSION

In critically ill children, lymphopenia is very common, often transient, but may be associated with unfavourable outcomes. Further studies with follow-up of blood counts in a larger sample are required to determine the course and outcomes of lymphopenia.

Developing a new sepsis screening tool based on lymphocyte count, international normalized ratio and procalcitonin (LIP score)

Exploring an effective sepsis screening tool that can be widely implemented is important for improving the prognosis of sepsis worldwide. This study aimed to develop a new simple screening tool for sepsis (LIP scoring system) that includes the peripheral blood lymphocyte count, international normalized ratio, and procalcitonin level. In a single-center, prospective, observational study, 444 acute sepsis inpatients and 444 nonsepsis inpatients were ultimately included based on the Sepsis-3 and exclusion criteria. The differences in the Lym, INR, PCT level and other clinical biomarkers were compared between the two groups. Univariable and multivariable logistic regression analyses and receiver operating characteristic analysis were used to establish a LIP screening tool for sepsis with a combination of biomarkers. The Kappa and McNemar tests were used to evaluate the differences between the LIP screening results (LIP score ≥ 3) and Sepsis-3 criteria (SOFA score ≥ 2). Logistic regression analysis showed that the lymphocyte count, INR, PCT level, platelets, neutrophil/lymphocyte ratio (NLR) and prothrombin time (PT) were independent risk factors for the development of sepsis. The ROC analysis showed that the lymphocyte count, INR, and PCT level had high area under the ROC curve values (AUROC (95% CI): Lym 0.84 (0.810-0.860), INR 0.921 (0.902-0.938), PCT level 0.928 (0.909-0.944)). The LIP tool had satisfactory screening efficacy for sepsis (sensitivity, 92.8%; specificity, 94.1%), and a LIP score equal to or greater than 3 points had good agreement with Sepsis-3 criteria in the diagnosis of sepsis (Kappa = 0862 in the Kappa test and P = 0.512 in the McNemar test). The LIP tool has satisfactory sensitivity and specificity for sepsis screening, and it can be used for rapid screening of patients with sepsis in outpatient and emergency departments or in economically underdeveloped areas with limited resources.

T cell dysregulation in inflammatory diseases in ICU

Severe inflammatory diseases, including sepsis, are characterized by an impaired host adaptive and innate immunity which results in immunosuppression, responsible for secondary infections and increased morbidity and mortality in critically ill patients. T cells are major actors of the immune system. During post-aggressive immunosuppression, lymphopenia, reduction of innate T cells, changes in T helper cell polarization and regulatory T cell increase are observed. The main mechanisms involved in T cell dysregulation are T cell apoptosis, autophagy deficiency, T cell anergy, T cell exhaustion and T cell metabolic reprogramming. In this review, we describe the alterations of T cell regulation, their mechanisms, and their association with clinical outcomes in severe inflammatory diseases, foremost of which is the sepsis.

This review focuses on the alterations of T cell regulation and their mechanisms in severe inflammatory ICU diseases. Lymphopenia, reduction of innate T cells, changes in T helper cell polarization and regulatory T cell increase contribute to secondary immunosuppression in ICU patients.

Lymphocyte trajectories are associated with prognosis in critically ill patients: A convenient way to monitor immune status

Background

Immunosuppression is a risk factor for poor prognosis of critically ill patients, but current monitoring of the immune status in clinical practice is still inadequate. Absolute lymphocyte count (ALC) is not only a convenient biomarker for immune status monitoring but is also suitable for clinical application. In this study, we aimed to explore different trajectories of ALC, and evaluate their relationship with prognosis in critically ill patients.

Methods

We retrospectively enrolled 10,619 critically ill patients admitted to a general intensive care unit (ICU) with 56 beds from February 2016 to May 2020. Dynamic ALC was defined as continuous ALC from before ICU admission to 5 days after ICU admission. Initial ALC was defined as the minimum ALC within 48 h after ICU admission. Group-based trajectory modeling (GBTM) was used to group critically ill patients according to dynamic ALC. Multivariate cox regression model was used to determine the independent association of trajectory endotypes with death and persistent inflammation, immunosuppression, catabolism syndrome (PICS).

Results

A total of 2022 critically ill patients were unsupervisedly divided into four endotypes based on dynamic ALC, including persistent lymphopenia endotype (n = 1,211; 58.5%), slowly rising endotype (n = 443; 22.6%), rapidly decreasing endotype (n = 281; 14.5%) and normal fluctuation endotype (n = 87; 4.4%). Among the four trajectory endotypes, the persistent lymphopenia endotype had the highest incidence of PICS (24.9%), hospital mortality (14.5%) and 28-day mortality (10.8%). In multivariate cox regression model, persistent lymphopenia was associated with increased risk of 28-day mortality (HR: 1.54; 95% CI: 1.06–2.23), hospital mortality (HR: 1.66; 95% CI: 1.20–2.29) and PICS (HR: 1.79; 95% CI: 1.09–2.94), respectively. Sensitivity analysis further confirmed that the ALC trajectory model of non-infected patients and non-elderly patients can accurately distinguished 91 and 90% of critically ill patients into the same endotypes as the original model, respectively.

Conclusion

The ALC trajectory model is helpful for grouping critically ill patients, and early persistent lymphopenia is associated with poor prognosis. Notably, persistent lymphopenia may be a robust signal of immunosuppression in critically ill patients.

Immune Modulation and Cytomegalovirus Reactivation in Sepsis-induced Immunosuppression: A Pilot Study

Introduction

Sepsis is a life-threatening condition caused due to dysregulated immune response to an infection and progressive immunosuppression. Reactivation of cytomegalovirus (CMV) occurs frequently in sepsis and is found associated with adverse outcomes. The study objective was to evaluate the association between incidence of CMV reactivation and immune alteration in sepsis-induced immunosuppression in patients with prolonged sepsis.

Patients and methods

Patients admitted to intensive care unit (ICU), with severe sepsis and CMV immunoglobulin G (IgG) seropositivity, were prospectively enrolled. Other manifest immune suppression causes were excluded. Samples were collected on enrolment and further once a week until day 21 or death/discharge. CMV viral load was quantified using qPCR. Lymphocyte subset analysis (CD3+, CD4+, CD8+, CD19+, CD16+/CD56+, and CD25+CD127− regulatory T cells), human leukocyte antigen-DR isotype (HLA-DR) expression on monocytes, programmed death-1 (PD-1) expression on T lymphocytes, and proinflammatory (interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ)), anti-inflammatory cytokines levels (IL-2, IL-4, and IL-10) were analyzed by flow cytometry as markers for immunosuppression.

Results

A total of 25 CMV IgG-positive patients and 11 healthy controls were included. CMV reactivation occurred in 20 patients. Patients with CMV reactivation had T-cell lymphopenia. PD-1 expression on CD4+ and CD8+ T cells was markedly elevated (p <0.02) in CMV-reactivated patients compared to nonreactivated patients. HLA-DR expression was significantly low on monocytes in all septic patients (p <0.01) compared to healthy controls. IL-6 levels showed elevation at day 7, whereas IL-10 was found to be significantly higher from day 0 in CMV-reactivated group.

Conclusion

Our study concluded that immune suppression markers and cytokine levels in patients with severe sepsis were found to be significantly associated with the incidence of CMV reactivation.

How to cite this article

Lambe G, Mansukhani D, Khodaiji S, Shetty A, Rodrigues C, Kapadia F. Immune Modulation and Cytomegalovirus Reactivation in Sepsis-induced Immunosuppression: A Pilot Study. Indian J Crit Care Med 2022;26(1):53–61.

Sestrin2 protects against lethal sepsis by suppressing the pyroptosis of dendritic cells

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sestrin2 (SESN2), a highly evolutionarily conserved protein, is critically involved in the cellular response to various stresses and has been confirmed to maintain the homeostasis of the internal environment. However, the potential effects of SESN2 in regulating dendritic cells (DCs) pyroptosis in the context of sepsis and the related mechanisms are poorly characterized. In this study, we found that SESN2 was capable of decreasing gasdermin D (GSDMD)-dependent pyroptosis of splenic DCs by inhibiting endoplasmic reticulum (ER) stress (ERS)-related nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)-mediated ASC pyroptosome formation and caspase-1 (CASP-1) activation. Furthermore, SESN2 deficiency induced NLRP3/ASC/CASP-1-dependent pyroptosis and the production of proinflammatory cytokines by exacerbating the PERK–ATF4–CHOP signaling pathway, resulting in an increase in the mortality of septic mice, which was reversed by inhibiting ERS. These findings suggest that SESN2 appears to be essential for inhibiting NLRP3 inflammasome hyperactivation, reducing CASP-1-dependent pyroptosis, and improving sepsis outcomes through stabilization of the ER. The present study might have important implications for exploration of novel potential therapeutic targets for the treatment of sepsis complications.

Trajectories of Lymphocyte Counts in the Early Phase of Acute Pancreatitis Are Associated With Infected Pancreatic Necrosis

INTRODUCTION

Infected pancreatic necrosis (IPN) is an important complication of acute pancreatitis (AP). Absolute lymphocyte count (ALC) was reported to be associated with immunosuppression and the development of IPN. The aim of this study was to describe the trajectory of ALC during the early phase of AP and assess its association with IPN.

METHODS

We retrospectively screened patients with AP admitted to our center between January 2016 and July 2019. The ALC levels for the first 7 days after admission were collected. Group-based trajectory modeling was performed to detect the trajectories. Cox proportional hazards regression model was adopted to identify potential risk factors of IPN.

RESULTS

Overall, 292 patients were enrolled for analysis. A triple-group trajectory model was developed, assigning 116 patients to the low-level ALC group, 133 to the medium-level ALC group, and 43 to the high-level ALC group. There was no overall significant difference regarding the incidence of IPN among the 3 groups (P = 0.066). In pairwise comparison, patients in the low-level ALC group had significantly higher incidence of IPN than those in the high-level ALC group (hazard ratio: 3.50; 95% confidence interval: 1.22-10.00, P = 0.020). Length of hospital stay and intensive care unit stay differed significantly among patients with different trajectories (P = 0.042 and 0.033, respectively).

DISCUSSION

Despite the fact that the trajectories of ALC is overall insignificant for the development of IPN, patients with persistent low ALC trajectories during the early phase of AP are more likely to develop IPN when compared with patients with high ALC trajectories.

Admission Lymphocytopenia is Associated with Urinary Tract Infection and Nosocomial Infections in Hemorrhagic Stroke

OBJECTIVE

Growing evidence suggests that lymphocytopenia on admission (LOA) is associated with infectious complications and poor outcomes in intracerebral hemorrhage (ICH). Whether LOA preferentially increases the risk for community acquired infections or nosocomial infections is unknown. This study investigates the relationship between LOA and nosocomial infections in a cohort of patients with ICH in a safety-net hospital.

MATERIAL AND METHODS

This is a single center, observational, retrospective study of 213 patients with non-traumatic ICH admitted to the neurocritical care unit between 2008 and 2014. Patients' clinical, demographic, lab and radiologic data were retrieved from institutional electronic medical records. Nosocomial infection was defined as clinical onset 48 h after admission.

RESULTS

Prevalence of LOA was 24.8%. Patients with LOA showed significant associations with mechanical ventilation (67.9% versus 49.4%; p= 0.019), higher median ICH score (2 versus 1; p=0.006), nosocomial infection (43.4% versus 28.0%; p=0.038), nosocomial UTI (24.5% versus 8.9%; p=0.003). Adjusting for baseline covariates in a multivariate logistic regression, we observed an association of LOA with nosocomial UTI (OR, 3.66 [95% CI, 1.36-9.88], p=0.010). From the Cox proportional model, patients with LOA had 1.76 times the hazard of developing of nosocomial infection, compared to those without LOA ([95% CI: 1.01, 3.07], p=0.046) and had 3.27 times the hazard of developing nosocomial UTI, compared to those without LOA ([95% CI: 1.39, 7.67], p=0.007).

CONCLUSIONS

This study is the first to show that LOA is associated with nosocomial urinary tract infections and significantly shorter times to develop nosocomial infections.

Alpinetin Attenuates Persistent Inflammation, Immune Suppression, and Catabolism Syndrome in a Septic Mouse Model

Patients who survive the acute phase of sepsis can progress to persistent inflammation, immunosuppression, and catabolism syndrome (PICS), which usually results in extended recovery periods and multiple complications. Alpinetin is a flavonoid isolated from Alpinia katsumadai Hayata that has been demonstrated to have anti-inflammatory, antibacterial, and antioxidant activities. The aim of this study was to investigate whether the administration of alpinetin could attenuate PICS in a septic mouse model. Mice were randomly divided into four groups: the (1) sham-operated group, (2) sham+alpinetin (1 mg/kg intravenously infused for once per day after sham operation), (3) cecal ligation and puncture (CLP), and (4) CLP+alpinetin (50 mg/kg intravenously infused for once per day after CLP). Eight days after sham operation or CLP surgery, mice were euthanized for subsequent examination. Alpinetin significantly improved the survival of septic mice. Also, it attenuated the CLP-induced persistent inflammation, immunosuppression, and catabolism syndrome. The level of plasma proinflammatory cytokines and apoptosis of T lymphocytes were obviously decreased by alpinetin as well. Moreover, oxidative stress in the organs was compelling lower in the alpinetin-treated CLP mice. In this clinically relevant model of sepsis, alpinetin ameliorates CLP-induced organ dysfunction and improves the likelihood of survival, possibly through suppressing the inflammatory response, oxidative stress, and apoptosis. These findings suggested that alpinetin could be a potential novel therapeutic approach to prevent sepsis-induced PICS.

Increased B-cell activity with consumption of activated monocytes in severe COVID-19 patients

The pathogenesis of autoimmune complications triggered by SARS-CoV2 has not been completely elucidated. Here, we performed an analysis of the cellular immune status, cell ratios, and monocyte populations of patients with COVID-19 treated in the intensive care unit (ICU) (cohort 1, N = 23) and normal care unit (NCU) (cohort 2, n = 10) compared with control groups: patients treated in ICU for noninfectious reasons (cohort 3, n = 30) and patients treated in NCU for infections other than COVID-19 (cohort 4, n = 21). Patients in cohort 1 presented significant differences in comparison with the other cohorts, including reduced frequencies of lymphocytes, reduced CD8+T-cell count, reduced percentage of activated and intermediate monocytes and an increased B/T8 cell ratio. Over time, patients in cohort 1 who died presented with lower counts of B, T, CD4+ T, CD8+ T-lymphocytes, NK cells, and activated monocytes. The B/T8 ratio was significantly lower in the group of survivors. In cohort 1, significantly higher levels of IgG1 and IgG3 were found, whereas cohort 3 presented higher levels of IgG3 compared to controls. Among many immune changes, an elevated B/T8-cell ratio and a reduced rate of activated monocytes were mainly observed in patients with severe COVID-19. Both parameters were associated with death in cohort 1.

Identification of Potential Early Diagnostic Biomarkers of Sepsis

Objective

The goal of this article was to identify potential biomarkers for early diagnosis of sepsis in order to improve their survival.

Methods

We analyzed differential gene expression between adult sepsis patients and controls in the GSE54514 dataset. Coexpression analysis was used to cluster coexpression modules, and enrichment analysis was performed on module genes. We also analyzed differential gene expression between neonatal sepsis patients and controls in the GSE25504 dataset, and we identified the subset of differentially expressed genes (DEGs) common to neonates and adults. All samples in the GSE54514 dataset were randomly divided into training and validation sets, and diagnostic signatures were constructed using least absolute shrink and selection operator (LASSO) regression. The key gene signature was screened for diagnostic value based on area under the receiver operating characteristic curve (AUC). STEM software identified dysregulated genes associated with sepsis-associated mortality. The ssGSEA method was used to quantify differences in immune cell infiltration between sepsis and control samples.

Results

A total of 6316 DEGs in GSE54514 were obtained spanning 10 modules. Module genes were mainly enriched in immune and metabolic responses. Screening 51 genes from among common genes based on AUC > 0.7 led to a LASSO model for the training set. We obtained a 25-gene signature, which we validated in the validation set and in the GSE25504 dataset. Among the signature genes, SLC2A6, C1ORF55, DUSP5 and RHOB were recognized as key genes (AUC > 0.75) in both the GSE54514 and GSE25504 datasets. SLC2A6 was identified by STEM as associated with sepsis-associated mortality and showed the strongest positive correlation with infiltration levels of Th1 cells.

Conclusion

In summary, our four key genes may have important implications for the early diagnosis of sepsis patients. In particular, SLC2A6 may be a critical biomarker for predicting survival in sepsis.

Correlation of Immunoglobulins and Lymphocytes Levels With the Clinical and Microbiological Response of Septic Patients With Gram-Negative Bacteremia

Background

Immunoglobulins (Igs) and cells of the innate and adaptive immune systems play a critical role in a host's response to sepsis. The aim of this study was to investigate the possible differences in the levels of Igs, white blood cells (WBCs), and T and B lymphocytes cells in relation to the microbiological and clinical responses of patients with sepsis or septic shock from carbapenem non-susceptible Gram-negative bacteria (CnS-GNB).

Methods

This pilot cohort study involved 24 hospitalized patients with sepsis or septic shock due to bacteremia from CnS-GNB. The microbiological and clinical responses of the patients were evaluated in relation to their blood levels of IgA, IgE, IgM and IgG, as well as WBCs and subpopulations of T and B cells upon sepsis diagnosis. A microbiological response was determined as clearance of bacteremia at 14 days of active antibiotic treatment for the isolated bacterial pathogen. Clinical response was defined as the resolution of all clinical and laboratory signs of infection and sepsis at 14 days of active antibiotic treatment for the isolated pathogen.

Results

From the 24 patients included in the study 18 (75%) and six patients (25%) presented and did not present microbiological response respectively, while 16 patients presented clinical response (64%) and eight patients (36%) did not have clinical response. The levels of the Igs did not show statistically significant differences between patients with sepsis from CnS-GNB bacteremia who exhibited microbiological or clinical response. There were also no statistically significant differences in the levels of WBCs and the subpopulations of T and B cells levels for these patients (P > 0.05). According to this pilot study, peripheral blood Igs and lymphocyte subpopulations levels do not affect the clinical and microbiological response of septic patients with bacteremia from CnS-GNB.

Conclusions

In patients with sepsis or septic shock from CnSGNB, there were no differences in the levels of Igs, circulating WBCs and T and B cells subpopulations between those with microbiological or clinical response and non-responders.

The Trajectory of Alterations in Immune-Cell Counts in Severe-Trauma Patients Is Related to the Later Occurrence of Sepsis and Mortality: Retrospective Study of 917 Cases

Background

Severe trauma is believed to disrupt the homeostasis of the immune system, and lead to dramatic changes in the circulating immune-cell count (ICC). The latter fluctuates widely over time. Knowledge about the relationship between these dramatic changes and dynamic fluctuations and the late prognosis of trauma patients is sparse. We investigated the relationship between the trajectory of alterations in the circulating ICC within 7 days in severe-trauma patients and subsequent sepsis and mortality.

Methods

A retrospective analysis of 917 patients with an Injury Severity Score ≥16 was undertaken. The absolute neutrophil, lymphocyte, and monocyte counts (ANC, ALC, and AMC, respectively) on days 1, 3, and 7 (D1, D3, and D7, respectively) after trauma, and whether sepsis or death occurred within 60 days, were recorded. As the disordered circulating ICCs fluctuated widely, their time-varying slopes (D3/D1 and D7/D3) were calculated. Patients were divided into “sepsis” and “non-sepsis” groups, as well as “alive” and “death” groups. Comparative studies were conducted between every two groups. Univariate and multivariate logistic regression analyses were used to identify variables related to the risk of sepsis and mortality. Receiver operating characteristic curves were plotted to assess the predictive value of various risk factors.

Results

More severe trauma caused more pronounced increases in the ANC and slower recovery of the ALC within 7 days. The ALC (D3), ANC (D7), ALC (D3/D1), and ANC (D7/D3) were independent risk factors for sepsis. The ALC (D3), ALC (D7), AMC (D7), and ALC (D3/D1) were independent risk factors for mortality. A combination of the ALC (D3) and ALC (D3/D1) exerted a good predictive value for sepsis and death.

Conclusions

The trajectory of alterations in the circulating ICC in the early stage after trauma is related to subsequent sepsis and mortality.

Persistent lymphopenia after diagnosis of COVID-19 predicts acute respiratory distress syndrome: A retrospective cohort study

Background

Lymphopenia is a marker of immunosuppression after severe coronavirus disease-2019 (COVID-19) which is characterized by acute respiratory distress syndrome (ARDS). This study aimed to evaluate the relationships between persistent lymphopenia and ARDS.

Methods

A retrospective cohort study of 125 patients with COVID-19 admitted to government-designated treatment center between 14 January 2020, and 20 March 2020 was conducted. We recorded all complete blood cell counts during the day 0th, 3rd, and 7th following the diagnosis of COVID-19. Patients were grouped based on the depression of the lymphocyte cell count, their return, or their failure to normal. The primary outcome was the occurrence of ARDS, and secondary outcomes included developing vital organ dysfunction and hospital lengths of stay.

Results

17.6% (22/125) patients developed ARDS. The lymphocyte counts with ARDS and non-ARDS were 0.94 × 109/L, 1.20 × 109/L at admission, respectively ( p = 0.02). On the 3rd and 7th day, the median of lymphocyte count in ARDS was significantly lower than that of non-ARDS. Multivariable logistic regression, which was adjusting for potentially confounding factors (including age, comorbidities, and APACHE II score), showed that persistent lymphopenia within the 7th day was independently associated with ARDS (OR, 3.94 [95% CI, 1.26–12.33, p = 0.018). Further, patients with persistent lymphopenia had longer hospital lengths of stay ( p < 0.001).

Conclusion

The results showed persistent lymphopenia predicted ARDS after COVID-19. Further studies are needed to investigate whether immunostimulation of lymphocytes within 1 week can reduce ARDS occurrence in patients with COVID-19.

Immune Alterations in a Patient with SARS-CoV-2-Related Acute Respiratory Distress Syndrome

We report a longitudinal analysis of the immune response associated with a fatal case of COVID-19 in Europe. This patient exhibited a rapid evolution towards multiorgan failure. SARS-CoV-2 was detected in multiple nasopharyngeal, blood, and pleural samples, despite antiviral and immunomodulator treatment. Clinical evolution in the blood was marked by an increase (2-3-fold) in differentiated effector T cells expressing exhaustion (PD-1) and senescence (CD57) markers, an expansion of antibody-secreting cells, a 15-fold increase in γδ T cell and proliferating NK-cell populations, and the total disappearance of monocytes, suggesting lung trafficking. In the serum, waves of a pro-inflammatory cytokine storm, Th1 and Th2 activation, and markers of T cell exhaustion, apoptosis, cell cytotoxicity, and endothelial activation were observed until the fatal outcome. This case underscores the need for well-designed studies to investigate complementary approaches to control viral replication, the source of the hyperinflammatory status, and immunomodulation to target the pathophysiological response. The investigation was conducted as part of an overall French clinical cohort assessing patients with COVID-19 and registered in clinicaltrials.gov under the following number: NCT04262921.

Best-practice IgM- and IgA-enriched immunoglobulin use in patients with sepsis

Background

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Despite treatment being in line with current guidelines, mortality remains high in those with septic shock. Intravenous immunoglobulins represent a promising therapy to modulate both the pro- and anti-inflammatory processes and can contribute to the elimination of pathogens. In this context, there is evidence of the benefits of immunoglobulin M (IgM)- and immunoglobulin A (IgA)-enriched immunoglobulin therapy for sepsis. This manuscript aims to summarize current relevant data to provide expert opinions on best practice for the use of an IgM- and IgA-enriched immunoglobulin (Pentaglobin) in adult patients with sepsis.

Main text

Sepsis patients with hyperinflammation and patients with immunosuppression may benefit most from treatment with IgM- and IgA-enriched immunoglobulin (Pentaglobin). Patients with hyperinflammation present with phenotypes that manifest throughout the body, whilst the clinical characteristics of immunosuppression are less clear. Potential biomarkers for hyperinflammation include elevated procalcitonin, interleukin-6, endotoxin activity and C-reactive protein, although thresholds for these are not well-defined. Convenient biomarkers for identifying patients in a stage of immune-paralysis are still matter of debate, though human leukocyte antigen–antigen D related expression on monocytes, lymphocyte count and viral reactivation have been proposed. The timing of treatment is potentially more critical for treatment efficacy in patients with hyperinflammation compared with patients who are in an immunosuppressed stage. Due to the lack of evidence, definitive dosage recommendations for either population cannot be made, though we suggest that patients with hyperinflammation should receive an initial bolus at a rate of up to 0.6 mL (30 mg)/kg/h for 6 h followed by a continuous maintenance rate of 0.2 mL (10 mg)/kg/hour for ≥ 72 h (total dose ≥ 0.9 g/kg). For immunosuppressed patients, dosage is more conservative (0.2 mL [10 mg]/kg/h) for ≥ 72 h, without an initial bolus (total dose ≥ 0.72 g/kg).

Conclusions

Two distinct populations that may benefit most from Pentaglobin therapy are described in this review. However, further clinical evidence is required to strengthen support for the recommendations given here regarding timing, duration and dosage of treatment.

Lymphocyte Immunosuppression and Dysfunction Contributing to Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS)

ABSTRACT

Persistent Inflammation, Immune Suppression, and Catabolism Syndrome (PICS) is a disease state affecting patients who have a prolonged recovery after the acute phase of a large inflammatory insult. Trauma and sepsis are two pathologies after which such an insult evolves. In this review, we will focus on the key clinical determinants of PICS: Immunosuppression and cellular dysfunction. Currently, relevant immunosuppressive functions have been attributed to both innate and adaptive immune cells. However, there are significant gaps in our knowledge, as for trauma and sepsis the immunosuppressive functions of these cells have mostly been described in acute phase of inflammation so far, and their clinical relevance for the development of prolonged immunosuppression is mostly unknown. It is suggested that the initial immune imbalance determines the development of PCIS. Additionally, it remains unclear what distinguishes the onset of immune dysfunction in trauma and sepsis and how this drives immunosuppression in these cells. In this review, we will discuss how regulatory T cells (Tregs), innate lymphoid cells, natural killer T cells (NKT cells), TCR-a CD4- CD8- double-negative T cells (DN T cells), and B cells can contribute to the development of post-traumatic and septic immunosuppression. Altogether, we seek to fill a gap in the understanding of the contribution of lymphocyte immunosuppression and dysfunction to the development of chronic immune disbalance. Further, we will provide an overview of promising diagnostic and therapeutic interventions, whose potential to overcome the detrimental immunosuppression after trauma and sepsis is currently being tested.

Novel non-cystic features of polycystic kidney disease: having new eyes or seeking new landscapes

For decades, researchers have been trying to decipher the complex pathophysiology of autosomal dominant polycystic kidney disease (ADPKD). So far these efforts have led to clinical trials with different candidate treatments, with tolvaptan being the only molecule that has gained approval for this indication. As end-stage kidney disease due to ADPKD has a substantial impact on health expenditures worldwide, it is likely that new drugs targeting kidney function will be developed. On the other hand, recent clinical observations and experimental data, including PKD knockout models in various cell types, have revealed unexpected involvement of many other organs and cell systems of variable severity. These novel non-cystic features, some of which, such as lymphopenia and an increased risk to develop infections, should be validated or further explored and might open new avenues for better risk stratification and a more tailored approach. New insights into the aberrant pathways involved with abnormal expression of PKD gene products polycystin-1 and -2 could, for instance, lead to a more directed approach towards early-onset endothelial dysfunction and subsequent cardiovascular disease. Furthermore, a better understanding of cellular pathways in PKD that can explain the propensity to develop certain types of cancer can guide post-transplant immunosuppressive and prophylactic strategies. In the following review article we will systematically discuss recently discovered non-cystic features of PKD and not well-established characteristics. Overall, this knowledge could enable us to improve the outcome of PKD patients apart from ongoing efforts to slow down cyst growth and attenuate kidney function decline.

Decreased Thymic Output Contributes to Immune Defects in Septic Patients

Background: Prolonged immunosuppression and hypoinflammation, termed compensatory anti-inflammatory response syndrome (CARS), contribute to high morbidity and mortality in the late phase of sepsis. Although apoptosis is a well-known cause of lymphopenia in sepsis, the contribution of thymic output to immune alterations in sepsis and potential compensatory mechanisms are largely unknown. Methods: We investigate the release of CD4+ T cells from the thymus and their peripheral proliferation by evaluating T-cell receptor excision circles (TREC) and the expression of CD31 as markers for recent thymic emigrants (RTE) and their proliferative offspring in septic patients with relevant lymphopenia in the CARS phase. Moreover, we determine the aging of T cells by measuring telomere characteristics. Results: In septic patients, we found decreased CD4+ T-helper cell numbers, while CD8+ T cell numbers were unchanged. As a possible cause, we detected increased apoptosis of CD4+ T-helper cells and decreased levels of IL-7, which promotes the maturation of T cells in the thymus. Accordingly, the relative number of mature CD4+ T cells, TREC-containing CD4+ T cells, and CD31+ RTEs (characteristic of thymic output) was decreased, while the relative number of CD31-T cells (peripherally expanded naïve T cells) was increased. Furthermore, the telomere length decreased, although telomerase activity and markers for the shelterin complex were increased specifically in CD4+ but not in CD8+ T cells. Conclusion: We thus conclude that, in addition to T-cell apoptosis, decreased thymic output and increased aging of CD4+ T cells may contribute to lymphopenia and immunosuppression in sepsis. Increased proliferation of peripheral T cells cannot compensate for these effects.

Types and outcomes of cytopenia in critically ill patients

Cytopenia is common complication in critically ill patients. Aim: Incidence and pattern of different types of cytopenia as well as its impact on mortality and length of stay in critically ill patients were evaluated. Methods: Critically ill patients with any kind of cytopenia for more than 2 days were evaluated. Results: Anemia was the most common type of cytopenia in the patients (99.14%), followed by lymphocytopenia (32.17%), thrombocytopenia (27.82%), and leukopenia (19.13%). Mortality rate was significantly higher in patients with anemia (p < 0.0001), thrombocytopenia (p < 0.0001), leukopenia (p < 0.0001), neutropenia (p = 0.004), lymphopenia (p = 0.002) and pancytopenia (p < 0.0001). Higher duration of anemia, lymphopenia and thrombocytopenia were associated with longer intensive care unit stay (p < 0.0001, p < 0.0001 and p < 0.001, respectively). Conclusion: Among all assessed variables, incidence of thrombocytopenia could independently predict the mortality.

Patients with COVID-19 in 19 ICUs in Wuhan, China: a cross-sectional study

BACKGROUND

A COVID-19 outbreak started in Wuhan, China, last December and now has become a global pandemic. The clinical information in caring of critically ill patients with COVID-19 needs to be shared timely, especially under the situations that there is still a largely ongoing spread of COVID-19 in many countries.

METHODS

A multicenter prospective observational study investigated all the COVID-19 patients received in 19 ICUs of 16 hospitals in Wuhan, China, over 24 h between 8 AM February 2h and 8 AM February 27, 2020. The demographic information, clinical characteristics, vital signs, complications, laboratory values, and clinical managements of the patients were studied.

RESULTS

A total of 226 patients were included. Their median (interquartile range, IQR) age was 64 (57-70) years, and 139 (61.5%) patients were male. The duration from the date of ICU admission to the study date was 11 (5-17) days, and the duration from onset of symptoms to the study date was 31 (24-36) days. Among all the patients, 155 (68.6%) had at least one coexisting disease, and their sequential organ failure assessment score was 4 (2-8). Organ function damages were found in most of the patients: ARDS in 161 (71.2%) patients, septic shock in 34 (15.0%) patients, acute kidney injury occurred in 57 (25.2%) patients, cardiac injury in 61 (27.0%) patients, and lymphocytopenia in 160 (70.8%) patients. Of all the studied patients, 85 (37.6%) received invasive mechanical ventilation, including 14 (6.2%) treated with extracorporeal membrane oxygenation (ECMO) at the same time, 20 (8.8%) received noninvasive mechanical ventilation, and 24 (10.6%) received continuous renal replacement therapy. By April 9, 2020, 87 (38.5%) patients were deceased and 15 (6.7%) were still in the hospital.

CONCLUSIONS

Critically ill patients with COVID-19 are associated with a higher risk of severe complications and need to receive an intensive level of treatments. COVID-19 poses a great strain on critical care resources in hospitals.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2000030164. Registered on February 24, 2020, http://www.chictr.org.cn/edit.aspx?pid=49983&htm=4.

Circulating Lymphocyte Subsets Induce Secondary Infection in Acute Pancreatitis

Acute pancreatitis (AP) is considered a cascade of immune responses triggered by acinar cell necrosis. AP involves two main processes of systemic inflammatory response syndrome and subsequent compensatory anti-inflammatory response syndrome. Although great efforts have been made regarding AP therapy, the mortality rate of AP remains high. Secondary infection acts a lethal factor in AP. Lymphocytes act as major immune mediators in immune responses in the course of this disease. However, the relationship between lymphocytes and secondary infection in AP is unclear. This review summarizes the variation of lymphocytes and infection in AP. Knowledge of the characterization of circulating lymphocyte abnormalities is relevant for understanding the pathophysiology of AP.

The Overlooked Immune State in Candidemia: A Risk Factor for Mortality

Lymphopenia has been related to increased mortality in septic patients. Nonetheless, the impact of lymphocyte count on candidemia mortality and prognosis has not been addressed. We conducted a retrospective study, including all admitted patients with candidemia from 2007 to 2016. We examined lymphocyte counts during the first 5 days following the diagnosis of candidemia. Multivariable logistic regression analysis was performed to determine the relationship between lymphocyte count and mortality. Classification and Regression Tree analysis was used to identify the best cut-off of lymphocyte count for mortality associated with candidemia. From 296 cases of candidemia, 115 died, (39.8% 30-day mortality). Low lymphocyte count was related to mortality and poor outcome (p < 0.001). Lymphocyte counts <0.703 × 10⁹ cells/L at diagnosis (area under the curve (AUC)-ROC, 0.783 ± 0.042; 95% confidence interval (CI), 0.700-0.867, p < 0.001), and lymphocyte count <1.272 × 10⁹ cells/L five days later (AUC-ROC, 0.791 ± 0.038; 95%CI, 0.716-0.866, p < 0.001) increased the odds of mortality five-fold (odds ratio (OR), 5.01; 95%CI, 2.39-10.93) at time of diagnosis, and three-fold (OR, 3.27; 95%CI, 1.24-8.62) by day 5, respectively. Low lymphocyte count is an independent predictor of mortality in patients with candidemia and might serve as a biomarker for predicting candidemia-associated mortality and poor outcome.

Lymphocyte Count Kinetics, Factors Associated with the End-of-Radiation-Therapy Lymphocyte Count, and Risk of Infection in Patients with Solid Malignant Tumors Treated with Curative-Intent Radiation Therapy

PURPOSE

Lymphopenia has been associated with poor outcomes in patients with cancer. We sought to describe the lymphocyte kinetics in patients who received radiation therapy; to identify factors associated with the end-of-radiation-therapy (EoRT) lymphocyte count; and to determine the association of radiation therapy-induced lymphopenia with subsequent infection.

METHODS AND MATERIALS

Patients with solid malignant tumors treated at the Department of Oncology at Rigshospitalet, University of Copenhagen, Denmark, were included if they had received their first external beam radiation therapy with curative intent from January 2005 to December 2016 and had pretreatment and EoRT lymphocyte counts measured. Factors associated with the EoRT lymphocyte count were identified using regression analyses. The risk of subsequent infection was estimated using Cox proportional hazards regression.

RESULTS

We included 3920 patients. More patients had lymphopenia (<1000 cells/μL) at EoRT than at pretreatment (67.1% vs 14.9%; P < .001). Patients who received schemes with higher intensities (equivalent dose in 2-Gy fractions [EQD2] >65 Gy) in shorter time (<25 days) had a higher predicted EoRT lymphocyte count than patients who received schemes delivering EQD2 of 50 to 65 Gy in 25 to 45 days (1439 cells/μL, 95% confidence interval [1293-1585] vs 784 [754-814]). Radiation to multiple sites and concomitant chemotherapy use, particularly platinum compounds versus none, were associated with a lower EoRT lymphocyte count (698 [655-742] vs 852 [833-870]; and 612 [565-659] vs 937 [909-964], respectively). Patients with EoRT lymphopenia grade ≥3 (<500 cells/μL) had a higher risk of infection in the 3 months after radiation therapy (hazard ratio, 2.15 [95% confidence interval, 1.53-3.02]; P < .001), compared with patients with an EoRT lymphocyte count >1000 cells/μL.

CONCLUSIONS

The lymphocyte count declined during radiation therapy. Short duration schemes (<25 days), despite high total radiation dose (EQD2 >65 Gy), were associated with a higher EoRT lymphocyte count, whereas radiation to multiple sites and concomitant chemotherapy were associated with a lower count. EoRT lymphopenia was associated with an increased risk of infection.

Nonviral infection-related lymphocytopenia for the prediction of adult sepsis and its persistence indicates a higher mortality

Sepsis is a life-threatening disease that affects 30 million people worldwide each year. Despite the rapid advances in medical technology and organ support systems, it is still difficult to reduce the mortality rate. Early and rapid diagnosis is crucial to improve the treatment outcome. The aim of this study was to investigate the prediction efficiency of lymphopenia and other clinical markers, such as white blood cell (WBC), neutrophil count (N#), procalcitonin (PCT), and arterial lactic acid (Lac) in the diagnosis and prognosis assessment for adult patients with nonviral infection-related sepsis.A total of 77 sepsis- and 23 non-sepsis adult patients were enrolled in this study from September 2016 to September 2018. Daily lymphocyte count (Lym) of the patients was calculated until discharge or death. The diagnostic performance of the Lym and other biomarkers were compared using the area under the receiver operating characteristic curve (ROC) value.The level of Lym was decreased significantly in the sepsis group. Lym had a high diagnostic performance for sepsis, with an area under the curve (AUC) value of 0.971 (95% CI = 0.916-0.994). The diagnostic efficacy of Lym was more significant than WBC, N#, and PCT (P < .001). The results showed that the 28-day mortality rate of patients with continuous Lym <0.76 × 10/L was 39.66%, which significantly higher than patients without persistent lymphocytopenia.Lym is a promising, low cost, fast, and easily available biomarker for the diagnosis of sepsis. When nonviral infection is suspected and lymphocytopenia level is lower than the optimal cut-off (0.76 × 10/L) value, high vigilance is required for sepsis. The persistence with the lymphocytopenia cut-off value (<0.76 × 10/L) >3 days indicates a higher 28-day mortality rate.

Circadian Rhythm Disruption and Sepsis in Severe Trauma Patients

BACKGROUND

Circadian rhythms are important regulators of immune functions. Admission to an intensive care unit may impact molecular clock activity and host response. Our objective was to assess and compare the immune circadian rhythms in trauma patients who develop and in those who do not develop sepsis.

METHODS

Blood samples were collected from severe trauma patients within 4 days after admission, with collections taking place every 4 h over a 24-h period. Cortisol and cytokines were measured with immunoassays. Whole-blood expression of 3 clock genes (Bmal1, Per2, and Per3) was studied by reverse transcription quantitative polymerase chain reaction. Neutrophils, monocytes, and lymphocytes were analyzed by flow cytometry. Patients with and without sepsis were compared with the cosinor mixed model to estimate mesors, amplitudes, and acrophases.

RESULTS

Thirty-eight patients were enrolled in the study, and 13 developed at least 1 septic episode. The septic patients had higher levels of cortisol than the nonseptic patients (mesor at 489 nmol/L vs. 405 nmol/L, P < 0.05) and delayed acrophases (22 h vs. 15 h, P < 0.05). They also had lower lymphocyte counts (mesor at 785 vs. 1,012 cells/μL, P < 0.05), higher neutrophil counts (mesor at 7,648 vs. 7,001 cells/μL, P < 0.05), and monocyte counts (mesor at 579 vs. 473 cells/μL, P < 0.05) than the nonseptic patients. Although no amplitude difference was identified, the acrophases were significantly different between the 2 groups for lymphocytes, interleukin 10 and tumor necrosis factor.

CONCLUSION

We demonstrated that all trauma patients had impaired circadian rhythms of cortisol, cytokines, leukocytes, and clock genes. Early circadian disruption was associated with the occurrence of sepsis and might be a marker of sepsis severity.

Impact of bronchial colonization with Candida spp. on the risk of bacterial ventilator-associated pneumonia in the ICU: the FUNGIBACT prospective cohort study

INTRODUCTION

Respiratory tract Candida spp. colonization is associated with more frequent bacterial ventilator-associated pneumonia (VAP). However, this colonization could be causally related to VAP or simply reflect the immune paralysis associated with multiple organ failure.

OBJECTIVE

To prospectively evaluate the relationship between Candida spp. colonization and bacterial VAP in mechanically ventilated patients with multiple organ failure.

INCLUSION

Patients receiving mechanical ventilation for > 4 days and presenting multiple organ failure were included. Tracheal colonization with Candida spp. was evaluated at inclusion (day 0, D0) and every 4 days until extubation. Quantitative proximal and tracheal cultures were performed at each VAP episode. Monocyte human leukocyte antigen-DR isotype (mHLA-DR) expression and the ratio of polymononuclear leukocytes to lymphocytes were used to evaluate immunoparalysis at D0 and D7. The relationship between fungal colonization and VAP was modelled using cause-specific models for repeated events with adjustment for time-dependent confounders and immune factors.

RESULTS

A total of 213 patients, with a median age of 64, simplified acute physiology score II (SAPS II) score 55 and sequential organ failure assessment (SOFA) score 10, mainly admitted for medical reasons (n = 197, 92%), were enrolled in 2012-2015. The median ICU stay was 24 days and the mortality rate was 32% (69 cases). Median mHLA-DR was 5916 Ab-bound/cell [3863-8934]; median lymphocyte count, 0.9Giga/L [0.6-1.3]; neutrophil-to-lymphocyte ratio, 10.9 [6.5-19.7]. Overall, 146 cases (68.5%) had tracheal colonization with Candida spp. An episode of VAP occurred (either for the first or only time) in 62 (29.1%) cases 5.5 days (median) after D0; a second episode occurred in 12 (5.6%) cases, 15.5 days (median) after D0. After adjustment, bronchial colonization with Candida was not associated with VAP [adjusted cause-specific hazard ratio = 0.98 (0.59-1.65), p = 0.95].

CONCLUSION

In patients with mechanical ventilation for more than 4 days and multiple organ failure, bronchial colonization with Candida spp. was not associated with VAP, even after adjustment for immune function.

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.

Early and dynamic alterations of Th2/Th1 in previously immunocompetent patients with community-acquired severe sepsis: a prospective observational study

BACKGROUND

T helper (Th) cells regulate sepsis processes, including primary pathogen clear and secondary pathogen defence. The objectives of this study were to determine the early and dynamic alterations of Th1 and Th2 populations to community-acquired severe sepsis upon onset among previously immunocompetent patients and whether it was related to clinical outcomes.

METHODS

This prospective observational cohort study was conducted at a general intensive care unit (ICU) of a tertiary teaching hospital in China. Immunocompetent patients with community-acquired severe sepsis within 24 h upon onset were included as septic group. Healthy volunteers and critically ill patients without severe sepsis were recruited as controls. Whole blood was collected on D0, 3rd day (D3) and 7th day (D7) for septic group and once upon enrollment for controls. Th1 and Th2 populations were measured by flow cytometry and assessed for associations with 28-day mortality using cox proportional hazard models. Associations of dynamic alterations of Th cell subpopulations with clinical outcomes were investigated.

RESULTS

This study demonstrated that community-acquired severe sepsis patients (n = 71) had increased Th2/Th1 and Th2 populations, compared to healthy controls (n = 7) and critically ill patients without severe sepsis (n = 7) at admission. Among the septic cohort, values of Th2/Th1 were significantly higher in non-survivors than survivors on D0 (p = 0.04), D3 (p < 0.001) and D7 (p < 0.001). Patients with persistently increasing Th2/Th1 demonstrated the highest mortality (47.1%) and incidence of ICU-acquired infections (64.7%).

CONCLUSIONS

Th2/Th1 was markedly up-regulated with Th2 dominance upon community-acquired severe sepsis onset among previously immunocompetent patients and its persistently dynamic increase was associated with ICU-acquired infections and 28-day death. Trial registration Institutional Ethics Committee of Zhongda Hospital, 2014ZDSYLL086, registered in June 2014-prospectively registered; ClinicalTrials.gov, NCT02883218, registered on 25 Aug 2016-retrospectively registered, https://www.clinicaltrials.gov/ct2/show/NCT02883218?cond=NCT02883218&rank=1.

Sepsis induces long-lasting impairments in CD4+ T-cell responses despite rapid numerical recovery of T-lymphocyte populations

Massive apoptosis of lymphocytes is a hallmark of sepsis. The resulting immunosuppression is associated with secondary infections, which are often lethal. Moreover, sepsis-survivors are burdened with increased morbidity and mortality for several years after the sepsis episode. The duration and clinical consequences of sepsis induced-immunosuppression are currently unknown. We have used the mouse model of peritoneal contamination and infection (PCI) to investigate the quantitative and qualitative recovery of T lymphocytes for 3.5 months after sepsis with or without IL-7 treatment. Thymic output and the numbers of naive and effector/memory CD4⁺ and CD8⁺ lymphocytes quickly recovered after sepsis. IL-7 treatment resulted in an accelerated recovery of CD8⁺ lymphocytes. Next generation sequencing revealed no significant narrowing of the T cell receptor repertoire 3.5 months after sepsis. In contrast, detailed functional analyses of T helper (Th)-cell responses towards a fungal antigen revealed a significant loss of Th cells. Whereas cytokine production was not impaired at the single cell level, the absolute number of Th cells specific for the fungal antigen was reduced. Our data indicate a clinically relevant loss of pathogen-specific T cell clones after sepsis. Given the small number of naive T lymphocytes specific for a given antigen, this decrement of T cell clones remains undetected even by sensitive methods such as deep sequencing. Taken together, our data are compatible with long lasting impairments in CD4⁺ T-cell responses after sepsis despite rapid recovery of T lymphocyte populations.

Lymphopenia and risk of infection and infection-related death in 98,344 individuals from a prospective Danish population-based study

BACKGROUND

Neutropenia increases the risk of infection, but it is unknown if this also applies to lymphopenia. We therefore tested the hypotheses that lymphopenia is associated with increased risk of infection and infection-related death in the general population.

METHODS AND FINDINGS

Of the invited 220,424 individuals, 99,191 attended examination. We analyzed 98,344 individuals from the Copenhagen General Population Study (Denmark), examined from November 25, 2003, to July 9, 2013, and with available blood lymphocyte count at date of examination. During a median of 6 years of follow-up, they developed 8,401 infections and experienced 1,045 infection-related deaths. Due to the completeness of the Danish civil and health registries, none of the 98,344 individuals were lost to follow-up, and those emigrating (n = 385) or dying (n = 5,636) had their follow-up truncated at the day of emigration or death. At date of examination, mean age was 58 years, and 44,181 (44.9%) were men. Individuals with lymphopenia (lymphocyte count < 1.1 × 109/l, n = 2,352) compared to those with lymphocytes in the reference range (1.1-3.7 × 109/l, n = 93,538) had multivariable-adjusted hazard ratios of 1.41 (95% CI 1.28-1.56) for any infection, 1.31 (1.14-1.52) for pneumonia, 1.44 (1.15-1.79) for skin infection, 1.26 (1.02-1.56) for urinary tract infection, 1.51 (1.21-1.89) for sepsis, 1.38 (1.01-1.88) for diarrheal disease, 2.15 (1.16-3.98) for endocarditis, and 2.26 (1.21-4.24) for other infections. The corresponding hazard ratio for infection-related death was 1.70 (95% CI 1.37-2.10). Analyses were adjusted for age, sex, smoking status, cumulative smoking, alcohol intake, body mass index, plasma C-reactive protein, blood neutrophil count, recent infection, Charlson comorbidity index, autoimmune diseases, medication use, and immunodeficiency/hematologic disease. The findings were robust in all stratified analyses and also when including only events later than 2 years after first examination. However, due to the observational design, the study cannot address questions of causality, and our analyses might theoretically have been affected by residual confounding and reverse causation. In principle, fluctuating lymphocyte counts over time might also have influenced analyses, but lymphocyte counts in 5,181 individuals measured 10 years after first examination showed a regression dilution ratio of 0.68.

CONCLUSIONS

Lymphopenia was associated with increased risk of hospitalization with infection and increased risk of infection-related death in the general population. Notably, causality cannot be deduced from our data.