The Long Pentraxin PTX3 Controls Klebsiella Pneumoniae Severe Infection

Complement-pentraxins synergy: Navigating the immune battlefield and beyond

The complement is a crucial immune defense system that triggers rapid immune responses and offers efficient protection against foreign invaders and unwanted host elements, acting as a sentinel. Activation of the complement system occurs upon the recognition of pathogenic microorganisms or altered self-cells by pattern-recognition molecules (PRMs) such as C1q, collectins, ficolins, and pentraxins. Recent accumulating evidence shows that pentraxins establish a cooperative network with different classes of effector PRMs, resulting in synergistic effects in complement activation. This review describes the complex interaction of pentraxins with the complement system and the implications of this cooperative network for effective host defense during pathogen invasion.

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside

Sepsis is a life-threatening condition and a significant cause of preventable morbidity and mortality globally. Among the leading causative agents of sepsis are bacterial pathogens Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, along with fungal pathogens of the Candida species. Here, we focus on evidence from human studies but also include in vitro and in vivo cellular and molecular evidence, exploring how bacterial and fungal pathogens are associated with bloodstream infection and sepsis. This review presents a narrative update on pathogen epidemiology, virulence factors, host factors of susceptibility, mechanisms of immunomodulation, current therapies, antibiotic resistance, and opportunities for diagnosis, prognosis, and therapeutics, through the perspective of bloodstream infection and sepsis. A list of curated novel host and pathogen factors, diagnostic and prognostic markers, and potential therapeutical targets to tackle sepsis from the research laboratory is presented. Further, we discuss the complex nature of sepsis depending on the sepsis-inducing pathogen and host susceptibility, the more common strains associated with severe pathology and how these aspects may impact in the management of the clinical presentation of sepsis.

PTX3 alleviates hard metal-induced acute lung injury through potentiating efferocytosis

Prolonged exposure to hard metal dust results in hard metal lung disease (HMLD) characterized by respiratory symptoms. Understanding the pathogenesis and pathological process of HMLD would be helpful for its early diagnosis and treatment. In this study, we established a mouse model of hard metal-induced acute lung injury through one-time intratracheal instillation of WC-Co dust suspension. We found that WC-Co treatment damaged the lungs of mice, leading to increased production of IL-1β, TNF-α, IL-6 and IL-18, inflammatory cells infiltration and apoptosis. In vitro, WC-Co induced cytotoxicity, inflammatory response and apoptosis in macrophages (PMA-treated THP-1) and epithelial cells (A549) in a dose-dependent manner. Moreover, RNA-sequence and validation experiments verified that Pentraxin 3 (PTX3), an important mediator in the regulation of inflammation, was elevated both in vivo and in vitro induced by WC-Co. Functional experiments confirmed the PTX3, which was located on the membrane of apoptotic cells, promoted macrophage efferocytosis efficiently. This progress could help block the lung inflammation and contribute to the rapid recovery of WC-Co-induced acute lung injury. These observations provide a further understanding of the molecular mechanism of WC-Co-induced pulmonary injury and disclose PTX3 as a new potential therapeutic approach to relieve WC-Co-induced acute lung injury via efferocytosis.

The role of pentraxin3 in plasma and bronchoalveolar lavage fluid in COPD patients with invasive pulmonary aspergillosis

Background

The use of galactomannan (GM) testing in plasma and bronchoalveolar lavage fluid (BALF) has improved the diagnosis of invasive pulmonary aspergillosis (IPA) in patients with chronic obstructive pulmonary disease (COPD); however, the high false-positive rate leads to overdiagnosis. Pentraxin 3 (PTX3) as an indicator of inflammation plays an important role in resistance to Aspergillus infections. This study aimed to investigate the diagnostic value of PTX3 for diagnosing IPA with COPD.

Methods

We retrospectively collected data on patients with suspected COPD and IPA who had been hospitalized in the Third Affiliated Hospital of Soochow University between September 2017 and November 2020. PTX3 and GM were measured using enzyme-linked immunosorbent assays.

Results

A total of 165 patients were included in the study, of whom 35 had confirmed or probable IPA. The remaining 130 patients served as controls. The median plasma and BALF PTX3 levels were significantly higher in patients with IPA than in control patients (3.74 ng/mL vs. 1.29 ng/mL, P < 0.001; and 3.88 ng/mL vs. 1.58 ng/mL, P < 0.001 in plasma and BALF, respectively). The plasma GM, plasma PTX3, BALF GM, and BALF PTX3 assays had sensitivities of 60.0%, 77.1%, 78.6%, and 89.3%, respectively, and specificities of 73.8%, 69.2%, 80.7%, and 77.1%, respectively. The sensitivity of PTX3 in plasma and BALF was higher than that of GM. However, the specificity of PTX3 and GM did not differ significantly between the IPA group and the control group. The specificity of the assays for the diagnosis of IPA was > 90% in patients who were PTX3-positive and GM-positive in plasma and BALF.

Conclusions

BALF and plasma PTX3 levels were significantly higher in COPD patients with IPA. The sensitivity of PTX3 was superior to that of GM for diagnosing IPA in patients with COPD. The combination of GM and PTX3 is useful for the diagnosis of IPA in patients with COPD.

Emerging roles of the complement system in host-pathogen interactions

The complement system has historically been entertained as a fluid-phase, hepatically derived system which protects the intravascular space from encapsulated bacteria. However, there has been an increasing appreciation for its role in protection against non-encapsulated pathogens. Specifically, we have an improved understanding of how pathogens are recognized by specific complement proteins, as well as how they trigger and evade them. Additionally, we have an improved understanding of locally derived complement proteins, many of which promote host defense. Moreover, intracellular complement proteins have been identified that facilitate local protection and barrier function despite pathogen invasion. Our review aims to summarize these advances in the field as well as provide an insight into the pathophysiological changes occurring when the system is dysregulated in infection.