Sepsis is defined as life-threatening organ dysfunction resulting from a dysregulated host response to infection. Patients with prior abdominal solid organ transplantation (SOT) are highly susceptible to infection due to chronic immunosuppression, yet exhibit improved survival once sepsis occurs. The underlying mechanisms remain poorly understood. We conducted a post hoc analysis within a prospective multicenter cohort of septic patients (SepsisDataNet.NRW; n = 538). Clinical outcomes were assessed using Kaplan-Meier analysis and multivariable Cox regression. Immune profiling included serum cytokines, flow cytometric immunophenotyping, plasma proteomics, and intracellular signaling using proximity ligation assays (PLA) in peripheral blood mononuclear cells (PBMCs). To reduce clinical confounding, complementary exploratory analyses were performed in a non-septic kidney transplant cohort (e:KID). SOT patients demonstrated improved 30-day survival compared with non-SOT patients (84
Abstract Background Direct, cell-resolved quantification of NLRP3 inflammasome activation in clinical patients has not been feasible. Previous studies have relied on indirect surrogates such as downstream cytokines, which are influenced by inflammasome-independent pathways and systemic clearance kinetics, potentially explaining the inconsistent prognostic findings reported in the literature. We applied a proximity ligation assay (PLA) to directly visualise NLRP3-caspase-1 complex formation in peripheral blood mononuclear cells of septic patients, providing a cell-specific, in situ readout of inflammasome assembly at the single-cell level. Methods In this prospective, multicentre proof-of-concept pilot study, 78 patients fulfilling Sepsis-3 criteria were enrolled across three university hospitals. The PLA was validated in THP-1-derived macrophages against established readouts of canonical inflammasome activation prior to clinical application. Patients were stratified into low (n = 28), intermediate (n = 23), and high (n = 27) NLRP3 inflammasome activity groups. Results Median age was 64 years (IQR: 56-78), 63% were male, and median Sequential Organ Failure Assessment score was 8 (IQR: 4-12). Baseline characteristics, disease severity scores, and routine inflammatory biomarkers did not differ across activity groups. Kaplan-Meier analysis revealed a non-linear pattern of 30-day survival, with the most favourable outcomes in the intermediate activity group. Both low and high activity were associated with increased mortality (log-rank p = 0.003). In adjusted Cox regression, low inflammasome activity (HR 7.88, 95% CI 1.79-34.65; p = 0.006) and high inflammasome activity (HR 4.35, 95% CI 1.01-19.88; p = 0.048) remained associated with 30-day mortality. Modelling PLA activity as a continuous variable using restricted cubic splines confirmed a significant non-linear association with 30-day mortality, independent of the tertile-based categorisation (p for non-linearity = 0.015). Conclusions This proof-of-concept pilot study demonstrates that direct in situ quantification of NLRP3–caspase-1 complex assembly is feasible in septic patients and reveals a non-linear association with 30-day survival. These findings indicate that PLA-based profiling captures immune heterogeneity beyond routine inflammatory biomarkers. Larger independent cohorts are needed to validate these findings before clinical application or patient stratification can be considered.
Ventilator-associated pneumonia (VAP) is frequent after traumatic brain injury (TBI), but its biological meaning and outcome impact remain incompletely defined. Traditional models emphasise mechanical ventilation, aspiration, colonisation, endotracheal tube biofilm, and hospital pathogens. These mechanisms remain essential, but they do not fully explain the early clustering, heterogeneous susceptibility, changing bacteriology, and variable mortality effect observed after TBI. Severe brain injury creates an early vulnerable host state through impaired consciousness and airway protection, neuroimmune dysregulation, autonomic and endocrine activation, altered pulmonary immune surveillance, and, in many patients, extracranial trauma, shock, transfusion, or thoracic injury. These processes interact with ventilation, antibiotic pressure, and rapid respiratory microbiome disruption. Early VAP may reflect abrupt loss of control after injury and intubation, whereas late VAP may reflect persistent or secondary failure driven by biofilm maturation, antibiotic selection, multidrug-resistant pathogens, and intensive care unit (ICU)-acquired immune dysfunction. Clinically, VAP consistently prolongs ventilation, ICU stay, antibiotic exposure, and resource use, while its independent effect on mortality is phenotype- and context-dependent. This model proposes a timing-sensitive ecological framework in which established mechanisms may converge early and with particular clinical intensity after severe TBI, creating a vulnerable host-microbe state that may lower the threshold for clinically apparent infection. Future studies should distinguish isolated TBI from polytrauma, compare TBI with other acute brain injuries and non-neurological ventilated populations, and incorporate dynamic immune, microbial, and trajectory-based outcomes.
