Lung-innervating nociceptor sensory neurons promote pneumonic sepsis during carbapenem-resistant Klebsiella pneumoniae lung infection

Role of specialized sensory neuron subtypes in modulating peripheral immune responses

The immune and sensory nervous systems detect diverse threats, from tissue damage to infection, and coordinate protective responses to restore homeostasis. Like immune cells, sensory neurons exhibit remarkable heterogeneity, with advanced genetic models revealing that distinct subsets differentially regulate immune responses. Here, we review how various immune signals engage distinct subtypes of sensory neurons to mediate inflammatory pain, itch, relief, protective behavioral adaptations, and autonomic reflexes. We also highlight how specialized sensory neuron populations modulate immune function through the release of neuropeptides, neurokines, or glutamate. This functional specialization enables precise immunomodulation adapted to the kinetics and nature of immune responses, positioning sensory neurons as key regulators of host defense and tissue homeostasis.

CD47-amyloid-β-CD74 signaling triggers adaptive immunosuppression in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. However, how this dysregulation occurs remains to be elucidated. In this study, we use single-cell RNA sequencing (scRNA-seq) and conventional RNA-seq to analyze the immune landscape of sepsis and observe that adaptive immunity is acutely and strongly suppressed. This systemic immunosuppression occurs not only in the peripheral blood but also in all other immune compartments, including the spleen, lymph nodes, and bone marrow. Clinical data show that these adaptive immunity-related genes may have the potential to be used to distinguish patients with sepsis from those with common infections. CD47 is found to play a pivotal role in this immunosuppression by inducing the production of amyloid-β (Aβ), which interacts with CD74 on B cells, leading to B-cell suppression and subsequent adaptive immunosuppression. Blocking CD47-Aβ signaling significantly reduces organ injury and improves the survival rate of septic mice by restoring phagocytic cell functions and alleviating B-cell suppression and adaptive immunosuppression.

Sepsis: the evolution of molecular pathogenesis concepts and clinical management

The mortality rate of sepsis is approximately 22.5%, accounting for 19.7% of the total global mortality. Since Lewis Thomas proposed in 1972 that "it is our response that makes the disease (sepsis)" rather than the invading microorganisms, numerous drugs have been developed to suppress the "overwhelming" inflammatory response, but none of them has achieved the desired effect. Continued failure has led investigators to question whether deaths in septic patients are indeed caused by uncontrolled inflammation. Here, we review the history of clinical trials based on evolving concepts of sepsis pathogenesis over the past half century, summarize the factors that led to the failure of these historical drugs and the prerequisites for the success of future drugs, and propose the basic principles of preclinical research to ensure successful clinical translation. The strategy of targeting inflammatory factors are like attempting to eliminate invaders by suppressing the host's armed forces, which is logically untenable. Sepsis may not be that complex; rather, sepsis may be the result of a failure to fight microbes when the force of an invading pathogen overwhelms our defenses. Thus, strengthening the body's defense forces instead of suppressing them may be the correct strategy to overcome sepsis.

Clinical application value of simultaneous plasma and bronchoalveolar lavage fluid metagenomic next generation sequencing in patients with pneumonia-derived sepsis

BACKGROUND

Despite the increasing use of metagenomic next-generation sequencing (mNGS) in sepsis, identifying clinically relevant pathogens remains challenging. This study was aimed to evaluate the clinical utility of simultaneous plasma and bronchoalveolar lavage fluid (BALF) detection using mNGS.

METHODS

This retrospective study enrolled 95 patients with pneumonia-derived sepsis (PDS) admitted to the intensive care unit (ICU) between October 2021 and January 2023. Patients were divided into two groups: mNGS group (n = 60) and the non-mNGS group (n = 35), based on whether simultaneous plasma and BALF mNGS were conducted. All patients underwent conventional microbiological tests (CMT), including bacterial/fungal culture of peripheral blood and BALF, as well as sputum culture, detection of 1, 3-beta-D- glucan in BALF and RT-PCR testing. The clinical data of the enrolled patients were collected, and the detection performance and prognosis of plasma mNGS, BALF mNGS and CMT were compared.

RESULTS

The mNGS group exhibited a lower mortality rate than the non-mNGS group (35.0% vs. 57.1%, P = 0.034). Simultaneous detection in dual-sample resulted in a higher proportion of microorganisms identified as definite causes of sepsis alert compared to detection in either plasma or BALF alone (55.6% vs. 20.8% vs. 18.8%, P<0.001). Acinetobacter baumannii, Stenotrophomonas maltophilia, Candida albicans, and human mastadenovirus B were the primary strains responsible for infections in PDS patients. Patients with lower white blood cells and neutrophil indices had a greater consistency in dual-sample mNGS. Patients in the mNGS group had more antibiotic adjustments compared to the non-mNGS group (85.71% vs. 33.33%, P<0.001). The percentage of neutrophils was a risk factor for mortality in PDS patients (P = 0.002).

CONCLUSION

Dual sample mNGS has the advantage of detecting and determining the pathogenicity of more pathogens and has the potential to improve the prognosis of patients with PDS.