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

Time-Dependent Variation in Immunoparalysis Biomarkers Among Patients with Sepsis and Critical Illness

Immunoparalysis is a significant concern in patients with sepsis and critical illness, potentially leading to increased risk of secondary infections. This study aimed to perform a longitudinal assessment of immune function over the initial two weeks following the onset of sepsis and critical illness. We compared ex vivo stimulated cytokine release to traditional markers of immunoparalysis, including monocyte Human Leukocyte Antigen (mHLA)-DR expression and absolute lymphocyte count (ALC). A total of 64 critically ill patients were recruited in a tertiary care academic medical setting, including 31 septic and 33 non-septic patients. Results showed that while mHLA-DR expression significantly increased over time, this was primarily driven by the non-septic subset of critically ill patients. ALC recovery was more prominent in septic patients. Ex vivo stimulation revealed significant increases in TNF and IL-6 production over time in septic patients. However, IFNγ production varied with the stimulant used and did not show significant recovery when normalized to cell count. No significant correlation was found between mHLA-DR expression and other immunoparalysis biomarkers. These findings suggest the need for more nuanced immune monitoring approaches beyond the traditional 'sepsis' versus 'non-sepsis' classifications in critically ill patients. It also provided further evidence of a potential window for targeted immunotherapeutic interventions in the first week of critical illness.

Use of Immune Profiling Panel to assess the immune response of septic patients for prediction of worsening as a composite endpoint

Sepsis induces intense, dynamic and heterogeneous host response modulations. Despite improvement of patient management, the risk of mortality and healthcare-associated infections remains high. Treatments to counterbalance immune response are under evaluation, but effective biomarkers are still lacking to perform patient stratification. The design of the present study was defined to alleviate the limitations of existing literature: we selected patients who survived the initial hyperinflammatory response and are still hospitalized at day 5-7 after ICU admission. Using the Immune Profiling Panel (IPP), a fully automated RT-qPCR multiplex prototype, we optimized a machine learning model combining the IPP gene expression levels for the identification of patients at high risk of worsening, a composite endpoint defined as death or secondary infection, within one week after sampling. This was done on 332 sepsis patients selected from two retrospective studies. The IPP model identified a high-risk group comprising 30% of patients, with a significant increased proportion of worsening events at day 28 compared to the low-risk group (49% vs. 28%, respectively). These preliminary results underline the potential clinical application of IPP for sepsis patient stratification in a personalized medicine perspective, that will be confirmed in a larger prospective multicenter study.

Severe Acute Respiratory Syndrome Coronavirus 2 Pneumonia in Critically Ill Patients: A Cluster Analysis According to Baseline Characteristics, Biological Features, and Chest CT Scan on Admission

BACKGROUND

Inconsistent results from COVID-19 studies raise the issue of patient heterogeneity.

OBJECTIVE

The objective of this study was to identify homogeneous subgroups of patients (clusters) using baseline characteristics including inflammatory biomarkers and the extent of lung parenchymal lesions on CT, and to compare their outcomes.

DESIGN

Retrospective single-center study.

SETTING

Medical ICU of the University Hospital of Clermont-Ferrand, France.

PATIENTS

All consecutive adult patients aged greater than or equal to 18 years, admitted between March 20, 2020, and August 31, 2021, for COVID-19 pneumonia.

INTERVENTIONS

Characteristics at baseline, during ICU stay, and outcomes at day 60 were recorded. On the chest CT performed at admission the extent of lung parenchyma lesions was established by artificial intelligence software.

MEASUREMENTS AND MAIN RESULTS

Clusters were determined by hierarchical clustering on principal components using principal component analysis of admission characteristics including plasma interleukin-6, human histocompatibility leukocyte antigen-DR expression rate on blood monocytes (HLA-DR) monocytic-expression rate (mHLA-DR), and the extent of lung parenchymal lesions. Factors associated with day 60 mortality were investigated by univariate survival analysis. Two hundred seventy patients were included. Four clusters were identified and three were fully described. Cluster 1 (obese patients, with moderate hypoxemia, moderate extent of lung parenchymal lesions, no inflammation, and no down-regulation of mHLA-DR) had a better prognosis at day 60 (hazard ratio [HR] = 0.27 [0.15-0.46], p < 0.01), whereas cluster 2 (older patients with comorbidities, moderate extent of lung parenchyma lesions but significant hypoxemia, inflammation, and down-regulation of mHLA-DR) and cluster 3 (patients with severe parenchymal disease, hypoxemia, inflammatory reaction, and down-regulation of mHLA-DR) had an increased risk of mortality (HR = 2.07 [1.37-3.13], p < 0.01 and HR = 1.52 [1-2.32], p = 0.05, respectively). In multivariate analysis, only clusters 1 and 2 were independently associated with day 60 death.

CONCLUSIONS

Three clusters with distinct characteristics and outcomes were identified. Such clusters could facilitate the identification of targeted populations for the next trials.

Bone morphogenetic protein 9 is a candidate prognostic biomarker and host-directed therapy target for sepsis

Defining next-generation immune therapeutics for the treatment of sepsis will involve biomarker-based therapeutic decision-making. Bone morphogenetic protein 9 (BMP9) is a cytokine in the transforming growth factor-β superfamily. Here, circulating BMP9 concentrations were quantified in two independent cohorts of patients with sepsis. Decreased concentrations of serum BMP9 were observed in the patients with sepsis at the time of admission as compared with healthy controls. Concentrations of BMP9 at the time of admission were also associated with 28-day mortality, because patients with sepsis at a higher risk of death had lower BMP9 concentrations. The mechanism driving the contribution of BMP9 to host immunity was further investigated using in vivo murine sepsis models and in vitro cell models. We found that BMP9 treatment improved outcome in mice with experimental sepsis. BMP9-treated mice exhibited increased macrophage influx into the peritoneal cavity and more efficient bacterial clearance than untreated mice. In vitro, BMP9 promoted macrophage recruitment, phagocytosis, and subsequent bacterial killing. We further found that deletion of the type 1 BMP receptor ALK1 in macrophages abolished BMP9-mediated protection against polymicrobial sepsis in vivo. Further experiments indicated that the regulation of macrophage activation by the BMP9-ALK1 axis was mainly mediated through the suppressor of mother against decapentaplegic 1/5 signaling pathway. Together, these results suggest that BMP9 can both serve as a biomarker for patient stratification with an independent prognostic value and be developed as a host-directed therapy for sepsis.