Protective effects of long pentraxin PTX3 on lung injury in a severe acute respiratory syndrome model in mice

Lipid-Laden Macrophages in Pulmonary Diseases

Pulmonary surfactants play a crucial role in managing lung lipid metabolism, and dysregulation of this process is evident in various lung diseases. Alternations in lipid metabolism lead to pulmonary surfactant damage, resulting in hyperlipidemia in response to lung injury. Lung macrophages are responsible for recycling damaged lipid droplets to maintain lipid homeostasis. The inflammatory response triggered by external stimuli such as cigarette smoke, bleomycin, and bacteria can interfere with this process, resulting in the formation of lipid-laden macrophages (LLMs), also known as foamy macrophages. Recent studies have highlighted the potential significance of LLM formation in a range of pulmonary diseases. Furthermore, growing evidence suggests that LLMs are present in patients suffering from various pulmonary conditions. In this review, we summarize the essential metabolic and signaling pathways driving the LLM formation in chronic obstructive pulmonary disease, pulmonary fibrosis, tuberculosis, and acute lung injury.

Therapeutic Effects of a Novel Aptamer on Coronaviral Infection-Induced Lung Injury and Systemic Inflammatory Responses

BACKGROUND

Coronaviral infection-induced acute lung injury has become a major threat to public health, especially through the ongoing pandemic of COVID-19. Apta-1 is a newly discovered Aptamer that has anti-inflammatory effects on systemic septic responses. The therapeutic effects of Apta-1 on coronaviral infection-induced acute lung injury and systemic responses were evaluated in the present study.

METHODS

Female A/J mice (at 12-14 weeks of age) were challenged with murine hepatitis virus 1 (MHV-1), a coronavirus, at 5000 PFU intranasally, followed by Apta-1 intravenously administered (100 mg/kg, twice) 1.5 h or 2 days after viral delivery. Animals were sacrificed at Day 2 or Day 4. Lung tissues were examined with H&E, immunohistochemistry staining, and western blotting. RT-qPCR was used for cytokine gene expression. Serum and plasma were collected for laboratory assessments.

RESULTS

Apta-1 treatment reduced viral titers, prevented MHV-1-induced reduction of circulating blood volume and hemolysis, reduced alveolar space hemorrhage, and protease-activated receptor 1 (PAR-1) cleavage. Apta-1 treatment also significantly reduced chemokine (MKC, MCP-1, and RANTES) levels, as well as AST, ALT, total bilirubin, and reduced unconjugated bilirubin levels in the serum.

CONCLUSION

Apta-1 showed therapeutic benefits in coronaviral infection-induced hemorrhage and PAR-1 cleavage in the lung. It also has anti-inflammatory effects systemically.

Serum Pentraxin 3 as Promising Biomarker for the Long-Lasting Inflammatory Response of COVID-19

Currently, biological markers for COVID-19 disease severity still constitute the main goal of enhancing an efficient treatment to reduce critical consequences such as an abnormal systemic inflammatory response. In this regard, the latest research has shown that Pentraxin 3 (PTX3), a highly conserved innate immunity protein, may serve as a valuable biochemical marker. Based on this evidence, we conducted a case-control study to compare the PTX3 serum levels and several immune-inflammatory mediators of 80 healthcare workers who were subdivided into subjects who were previously infected with SARS-CoV-2 (n = 40) and individuals who were never infected (n = 40). Using a commercially available Enzyme-Linked Immunosorbent Assay (ELISA), PTX3 and various immune-inflammatory protein levels were assessed in serum samples, while also considering possible variables (e.g., gender-related differences). We have shown elevated levels of PTX3 and other inflammatory proteins in previously infected COVID-19-positive subjects (p < 0.001). Moreover, the obtained data also indicate a degree of severity influenced by gender, as shown by the subgroup analysis, in which PTX3 expression was more pronounced in previously COVID-19-positive males (p < 0.001) than in females (p < 0.05) compared to the respective controls. In addition, our data further validate, through a direct comparison of previously COVID-19-positive subjects, greater pro-inflammatory levels in males than in females. Overall, our results may support the validity of PTX3 as a systemic biomarker in prolonged systemic inflammatory responses in the context of COVID-19. Thus, PTX3 modulation could constitute an effective therapeutic strategy for improving the recovery from COVID-19 and its systemic long-term consequences.

Association of polymorphisms in long pentraxin 3 and its plasma levels with COVID-19 severity

COVID-19 is an infectious respiratory disease caused by SARS-CoV-2. Pentraxin 3 (PTX3) is involved in the activation and regulation of the complement system, demonstrating an important role in the pathogenesis of COVID-19. The aim was to evaluate the association of single nucleotide polymorphisms in PTX3 and its plasma levels with the severity of COVID-19. This is a retrospective cohort study, carried out between August 2020 and July 2021, including patients with confirmed COVID-19 hospitalized in 2 hospitals in the Northeast Region of Brazil. Polymorphisms in PTX3 (rs1840680 and rs2305619) were determined by real-time PCR. PTX3 plasma levels were measured by ELISA. Serum levels of interleukin (IL)-6, IL-8, and IL-10 were determined by flow cytometry. A multivariate logistic regression model was used to identify parameters independently associated with COVID-19 severity. P values  < 0.05 were considered significant. The study included 496 patients, classified as moderate (n = 267) and severe (n = 229) cases. The PTX3 AA genotype (rs1840680) was independently associated with protection against severe COVID-19 (P = 0.037; odds ratio = 0.555). PTX3 plasma levels were significantly associated with COVID-19 severity and mortality (P < 0.05). PTX3 levels were significantly correlated with IL-6, IL-8, IL-10, C-reactive protein, total leukocytes, neutrophil-to-lymphocyte ratio, urea, creatinine, ferritin, length of hospital stay, and higher respiratory rate (P < 0.05). Our results revealed a protective effect of the PTX3 AA genotype (rs1840680) on the development of severe forms of COVID-19. Additionally, PTX3 plasma levels were associated with the severity of COVID-19. The results of this study provide evidence of an important role of PTX3 in the immunopathology of COVID-19.

RETRACTED: The pathogenicity of COVID-19 and the role of pentraxin-3: An updated review study

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. In investigating concerns regarding the contributions of the authors to this article, the editors reached out to the authors for an explanation. In addition to the concerns regarding the contribution of each author, the editors discovered suspicious changes in authorship between the original submission and the revised version of this paper. The names of the authors Ameer A Alameri and Zanko Hassan Jawhar were added to the revised version of the article without explanation and without the exceptional approval by the handling Editor, which is contrary to the journal policy on changes to authorship. The authors were unable to provide a reasonable explanation for either of the issues raised. The editor therefore feels that the findings of the manuscript cannot be relied upon and that the article needs to be retracted.

PTX3 structure determination using a hybrid cryoelectron microscopy and AlphaFold approach offers insights into ligand binding and complement activation

Pattern recognition molecules (PRMs) form an important part of innate immunity, where they facilitate the response to infections and damage by triggering processes such as inflammation. The pentraxin family of soluble PRMs comprises long and short pentraxins, with the former containing unique N-terminal regions unrelated to other proteins or each other. No complete high-resolution structural information exists about long pentraxins, unlike the short pentraxins, where there is an abundance of both X-ray and cryoelectron microscopy (cryo-EM)-derived structures. This study presents a high-resolution structure of the prototypical long pentraxin, PTX3. Cryo-EM yielded a 2.5-Å map of the C-terminal pentraxin domains that revealed a radically different quaternary structure compared to other pentraxins, comprising a glycosylated D4 symmetrical octameric complex stabilized by an extensive disulfide network. The cryo-EM map indicated α-helices that extended N terminal of the pentraxin domains that were not fully resolved. AlphaFold was used to predict the remaining N-terminal structure of the octameric PTX3 complex, revealing two long tetrameric coiled coils with two hinge regions, which was validated using classification of cryo-EM two-dimensional averages. The resulting hybrid cryo-EM/AlphaFold structure allowed mapping of ligand binding sites, such as C1q and fibroblast growth factor-2, as well as rationalization of previous biochemical data. Given the relevance of PTX3 in conditions ranging from COVID-19 prognosis, cancer progression, and female infertility, this structure could be used to inform the understanding and rational design of therapies for these disorders and processes.

Severity Biomarkers in Puumala Hantavirus Infection

Annually, over 10,000 cases of hemorrhagic fever with renal syndrome (HFRS) are diagnosed in Europe. Puumala hantavirus (PUUV) causes most of the European HFRS cases. PUUV causes usually a relatively mild disease, which is rarely fatal. However, the severity of the infection varies greatly, and factors affecting the severity are mostly unrevealed. Host genes are known to have an effect. The typical clinical features in PUUV infection include acute kidney injury, thrombocytopenia, and increased vascular permeability. The primary target of hantavirus is the endothelium of the vessels of different organs. Although PUUV does not cause direct cytopathology of the endothelial cells, remarkable changes in both the barrier function of the endothelium and the function of the infected endothelial cells occur. Host immune or inflammatory mechanisms are probably important in the development of the capillary leakage. Several immunoinflammatory biomarkers have been studied in the context of assessing the severity of HFRS caused by PUUV. Most of them are not used in clinical practice, but the increasing knowledge about the biomarkers has elucidated the pathogenesis of PUUV infection.

Suppression and Activation of Intracellular Immune Response in Initial Severe Acute Respiratory Syndrome Coronavirus 2 Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently the most important emerging pathogen worldwide, but its early transcriptional dynamics and host immune response remain unclear. Herein, the expression profiles of viral interactions with different types of hosts were comprehensively dissected to shed light on the early infection strategy of SARS-CoV-2 and the host immune response against infection. SARS-CoV-2 was found to exhibit a two-stage transcriptional strategy within the first 24 h of infection, comprising a lag phase that ends with the virus being paused and a log phase that starts when the viral load increases rapidly. Interestingly, the host innate immune response was found not to be activated (latent period) until the virus entered the log stage. Noteworthy, when intracellular immunity is suppressed, SARS-CoV-2 shows a correlation with dysregulation of metal ion homeostasis. Herein, the inhibitory activity of copper ions against SARS-CoV-2 was further validated in in vitro experiments. Coronavirus disease 2019-related genes (including CD38, PTX3, and TCN1) were also identified, which may serve as candidate host-restricted factors for interventional therapy. Collectively, these results confirm that the two-stage strategy of SARS-CoV-2 effectively aids its survival in early infection by regulating the host intracellular immunity, highlighting the key role of interferon in viral infection and potential therapeutic candidates for further investigations on antiviral strategies.

The Long Pentraxin PTX3 Controls Klebsiella Pneumoniae Severe Infection

Klebsiella pneumoniae is a common pathogen in human sepsis. The emergence of multidrug-resistant K. pneumoniae strains represents a major clinical challenge in nosocomial and community acquired infections. The long pentraxin PTX3, a key component of humoral innate immunity, is involved in resistance to selected pathogens by promoting opsonophagocytosis. We investigated the relevance of PTX3 in innate immunity against K. pneumoniae infections using Ptx3^-/- mice and mouse models of severe K. pneumoniae infections. Local and systemic PTX3 expression was induced following K. pneumoniae pulmonary infection, in association with the up-regulation of TNF-α and IL-1β. PTX3 deficiency in mice was associated with higher bacterial burden and mortality, release of pro-inflammatory cytokines as well as IL-10 in the lung and systemically. The analysis of the mechanisms responsible of PTX3-dependent control of K. pneumoniae infection revealed that PTX3 did not interact with K. pneumoniae, or promote opsonophagocytosis. The comparison of susceptibility of wild-type, Ptx3^-/-, C3^-/- and Ptx3^-/-/C3^-/- mice to the infection showed that PTX3 acted in a complement-independent manner. Lung histopathological analysis showed more severe lesions in Ptx3^-/- mice with fibrinosuppurative, necrotizing and haemorrhagic bronchopneumonia, associated with increased fibrin deposition in the lung and circulating fibrinogen consumption. These findings indicate that PTX3 contributes to the control of K. pneumoniae infection by modulating inflammatory responses and tissue damage. Thus, this study emphasizes the relevance of the role of PTX3 as regulator of inflammation and orchestrator of tissue repair in innate responses to infections.

Pentraxin 3 expression in lungs and neutrophils of calves

Bacterial lung disease caused by Mannheimia haemolytica inflict significant mortality and morbidity resulting in enormous economic losses to cattle industry. The use of antibiotics is becoming more challenging because of development of anti-microbial resistance. The innate immune system plays a critical role in the initiation of immune response in the lung. Pentraxin 3 (PTX3), a pattern-recognition receptor is produced at sites of inflammation by many cell types, recognizes and binds to many pathogens, activates the complement cascade, and has a role in the clearance of apoptotic and necrotic cells. Because there are very few data on the expression of PTX3 in the lungs, we examined PTX3 expression in lungs of normal and M. haemolytica-infected calves and normal and E. coli lipopolysaccharide-treated cattle neutrophils using light and electron microscopic immunochemistry and Western blots. Immunohistology showed the presence of PTX3 in airway epithelial cells, alveolar septa and macrophages in normal and inflamed lungs of calves and the blots showed a significant increase in the expression of PTX3 in lungs from infected calves. Immuno-gold electron microscopy showed PTX3 in the nuclei, cytoplasm, and vesicular organelles of alveolar macrophages, endothelial cells and pulmonary intravascular macrophages (PIMs). Immunohistochemical staining for PTX3 in peripheral blood neutrophils shows an altered staining pattern in neutrophils stimulated with lipopolysachharide (LPS). However, western blots no significant change in PTX3 amount in LPS-treated neutrophils compared to the controls. These are the first data on the expression of PTX3 in the lungs and the neutrophils of cattle which may add to our understanding of innate immunity in cattle lungs.

Pathogenetic profiling of COVID-19 and SARS-like viruses

The novel coronavirus (2019-nCoV) has recently emerged, causing COVID-19 outbreaks and significant societal/global disruption. Importantly, COVID-19 infection resembles SARS-like complications. However, the lack of knowledge about the underlying genetic mechanisms of COVID-19 warrants the development of prospective control measures. In this study, we employed whole-genome alignment and digital DNA-DNA hybridization analyses to assess genomic linkage between 2019-nCoV and other coronaviruses. To understand the pathogenetic behavior of 2019-nCoV, we compared gene expression datasets of viral infections closest to 2019-nCoV with four COVID-19 clinical presentations followed by functional enrichment of shared dysregulated genes. Potential chemical antagonists were also identified using protein-chemical interaction analysis. Based on phylogram analysis, the 2019-nCoV was found genetically closest to SARS-CoVs. In addition, we identified 562 upregulated and 738 downregulated genes (adj. P ≤ 0.05) with SARS-CoV infection. Among the dysregulated genes, SARS-CoV shared ≤19 upregulated and ≤22 downregulated genes with each of different COVID-19 complications. Notably, upregulation of BCL6 and PFKFB3 genes was common to SARS-CoV, pneumonia and severe acute respiratory syndrome, while they shared CRIP2, NSG1 and TNFRSF21 genes in downregulation. Besides, 14 genes were common to different SARS-CoV comorbidities that might influence COVID-19 disease. We also observed similarities in pathways that can lead to COVID-19 and SARS-CoV diseases. Finally, protein-chemical interactions suggest cyclosporine, resveratrol and quercetin as promising drug candidates against COVID-19 as well as other SARS-like viral infections. The pathogenetic analyses, along with identified biomarkers, signaling pathways and chemical antagonists, could prove useful for novel drug development in the fight against the current global 2019-nCoV pandemic.

Novel signaling pathways regulate SARS-CoV and SARS-CoV-2 infectious disease

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 induces severe infection, and it is responsible for a worldwide disease outbreak starting in late 2019. Currently, there are no effective medications against coronavirus. In the present study, we utilized a holistic bioinformatics approach to study gene signatures of SARS-CoV- and SARS-CoV-2-infected Calu-3 lung adenocarcinoma cells. Through the Gene Ontology platform, we determined that several cytokine genes were up-regulated after SARS-CoV-2 infection, including TNF, IL6, CSF2, IFNL1, IL-17C, CXCL10, and CXCL11. Differentially regulated pathways were detected by the Kyoto Encyclopedia of Genes and Genomes, gene ontology, and Hallmark platform, including chemokines, cytokines, cytokine receptors, cytokine metabolism, inflammation, immune responses, and cellular responses to the virus. A Venn diagram was utilized to illustrate common overlapping genes from SARS-CoV- and SARS-CoV-2-infected datasets. An Ingenuity pathway analysis discovered an enrichment of tumor necrosis factor- (TNF-) and interleukin (IL)-17-related signaling in a gene set enrichment analysis. Downstream networks were predicted by the Database for Annotation, Visualization, and Integrated Discovery platform also revealed that TNF and TNF receptor 2 signaling elicited leukocyte recruitment, activation, and survival of host cells after coronavirus infection. Our discovery provides essential evidence for transcript regulation and downstream signaling of SARS-CoV and SARS-CoV-2 infection.

Endogenous Long Pentraxin 3 Exerts a Protective Role in a Murine Model of Pulmonary Fibrosis

Pulmonary fibrosis is a progressive scarring disease of the lungs, characterized by inflammation, fibroblast activation, and deposition of extracellular matrix. The long pentraxin 3 (PTX3) is a member of the pentraxin family with non-redundant functions in innate immune responses, tissue repair, and haemostasis. The role played in the lungs by PTX3 during the fibrotic process has not been elucidated. In this study, the impact of PTX3 expression on lung fibrosis was assessed in an intratracheal bleomycin (BLM)-induced murine model of the disease applied to wild type animals, transgenic mice characterized by endothelial overexpression and stromal accumulation of PTX3 (Tie2-PTX3 mice), and genetically deficient Ptx3^−/− animals. Our data demonstrate that PTX3 is produced during BLM-induced fibrosis in wild type mice, and that PTX3 accumulation in the stroma compartment of Tie2-PTX3 mice limits the formation of fibrotic tissue in the lungs, with reduced fibroblast activation and collagen deposition, and a decrease in the recruitment of the immune infiltrate. Conversely, Ptx3-null mice showed an exacerbated fibrotic response and decreased survival in response to BLM treatment. These results underline the protective role of endogenous PTX3 during lung fibrosis and pave the way for the study of novel PTX3-derived therapeutic approaches to the disease.

Elevated Serum Pentraxin-3 Levels is Positively Correlated to Disease Severity and Coagulopathy in COVID-19 Patients

BACKGROUND

Coronavirus disease 2019 (COVID-19) is highly contagious and deadly and is associated with coagulopathy. Pentraxin-3(PTX3) participates in innate resistance to infections and plays a role in thrombogenesis.

PURPOSE

The present study aimed to investigate the role of PTX3 in coagulopathy in patients with COVID-19.

METHODS

A retrospective study, including thirty-nine COVID-19 patients, enrolled in Hunan, China, were performed. The patients were classified into the D-dimer_L (D-dimer <1mg/L) and D-dimer_H (D-dimer≥1mg/L) groups basing on the plasma D-dimer levels on admission. Serum PTX3 levels were detected by enzyme-linked immunosorbent assays and compared between those two groups, then receiver operating characteristic (ROC) curve analysis, correlation analysis, and linear regression models were performed to analyze the association between PTX3 and D-dimer.

RESULTS

Our results showed that serum PTX3 levels (median values, 10.21 vs. 3.36, P<0.001), computerized chest tomography (C.T.) scores (median values, 10.0 vs. 9.0, P<0.05), and length of stay (LOS) (mean values, 16.0 vs. 10.7, P=0.001) in the D-dimer_H group were significantly higher than that in D-dimer_L group. ROC curve analysis revealed that the AUC of white blood corpuscle counts, C-reaction protein, erythrocyte sedimentation rate, and PTX3 for COVID-19 were 0.685, 0.863, 0.846, and 0.985, respectively. Correlation analysis showed that there was a positive relationship between PTX3 and D-dimer (r=0.721, P<0.001), chest CT imaging score (r=0.418, P=0.008), and LOS (r=0.486, P=0.002). Multiple linear regression analysis showed that the coefficient of determination was 0.657 (P < 0.001).

CONCLUSION

Serum level of PTX3 was positively correlated with disease severity and coagulopathy. Detection of serum PTX3 level could help identify severer patients on admission and may be a potential therapeutic target for coagulopathy in patients with COVID-19.

Neutrophils in respiratory syncytial virus infection: From harmful effects to therapeutic opportunities

Respiratory syncytial virus (RSV) is an important infectious agent in infants and young children. In most cases, RSV infection only causes mild disease, but in some, it requires invasive ventilation. Although antiviral drugs are obvious candidates to treat viral illness, and some have shown antiviral effects in humans, antivirals such as GS-5806, ALX-0171 and ALS-8176 have not yet met their expectations. Since the inappropriate or dysregulated immune response against RSV leads to harmful immune pathology, a robust immune cascade is probably underway by the time patients reach the hospital. RSV infection is associated with a strong neutrophil influx into the airway. It not clear if these cells contribute to antiviral defence or to lung pathology. This article discusses the protective and harmful roles of neutrophils during RSV infection and provides an overview of mechanisms by which neutrophil function could be targeted to prevent tissue injury and preserve homeostasis.

Glucagon-like peptide-1 receptor mediates the beneficial effect of liraglutide in an acute lung injury mouse model involving the thioredoxin-interacting protein

Repurposing clinically used drugs is among the important strategies in drug discovery. Glucagon-like peptide-1 (GLP-1) and its diabetes-based drugs, such as liraglutide, possess a spectrum of extra-pancreatic functions, while GLP-1 receptor (GLP-1R) is most abundantly expressed in the lung. Recent studies have suggested that GLP-1-based drugs exert beneficial effects in chronic, as well as acute, lung injury rodent models. Here, we show that liraglutide pretreatment reduced LPS induced acute lung injury in mice. It significantly reduced lung injury score, wet/dry lung weight ratio, bronchoalveolar lavage fluid immune cell count and protein concentration, and cell apoptosis in the lung, and it was associated with reduced lung inflammatory cytokine and chemokine gene expression. Importantly, these effects were virtually absent in GLP-1R^-/- mice. A well-known function of GLP-1 and GLP-based drugs in pancreatic β-cells is the attenuation of high-glucose stimulated expression of thioredoxin-interacting protein (TxNIP), a key component of inflammasome. LPS-challenged lungs showed elevated TxNIP mRNA and protein expression, which was attenuated by liraglutide treatment in a GLP-1R-dependent manner. Hence, our observations suggest that GLP-1R is essential in mediating beneficial effects of liraglutide in acute lung injury, with the inflammasome component TxNIP as a potential target.

Of Mice and Men: The Coronavirus MHV and Mouse Models as a Translational Approach to Understand SARS-CoV-2

The fatal acute respiratory coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since COVID-19 was declared a pandemic by the World Health Organization in March 2020, infection and mortality rates have been rising steadily worldwide. The lack of a vaccine, as well as preventive and therapeutic strategies, emphasize the need to develop new strategies to mitigate SARS-CoV-2 transmission and pathogenesis. Since mouse hepatitis virus (MHV), severe acute respiratory syndrome coronavirus (SARS-CoV), and SARS-CoV-2 share a common genus, lessons learnt from MHV and SARS-CoV could offer mechanistic insights into SARS-CoV-2. This review provides a comprehensive review of MHV in mice and SARS-CoV-2 in humans, thereby highlighting further translational avenues in the development of innovative strategies in controlling the detrimental course of SARS-CoV-2. Specifically, we have focused on various aspects, including host species, organotropism, transmission, clinical disease, pathogenesis, control and therapy, MHV as a model for SARS-CoV and SARS-CoV-2 as well as mouse models for infection with SARS-CoV and SARS-CoV-2. While MHV in mice and SARS-CoV-2 in humans share various similarities, there are also differences that need to be addressed when studying murine models. Translational approaches, such as humanized mouse models are pivotal in studying the clinical course and pathology observed in COVID-19 patients. Lessons from prior murine studies on coronavirus, coupled with novel murine models could offer new promising avenues for treatment of COVID-19.

Pentraxin 3 (PTX-3) Levels in Bronchoalveolar Lavage Fluid as a Lung Cancer Biomarker

In this study, we investigated the utility of pentraxin 3 (PTX-3) in bronchoalveolar lavage fluid (BALF) as lung cancer (LCa) diagnostic. A total of 89 LCa patients and 84 non-LCa patients who received bronchoscopy in the First Affiliated Hospital of Xi'an Jiaotong University from December 2014 to February 2015 were enrolled. LCa was subdivided according to pathological type (scale, gland, and small cell lung cancer). BALF samples were obtained during bronchoscopy and PTX-3 levels assayed by ELISA. t-tests, Mann-Whitney, and Kruskal-Wallis tests were performed for the comparison of PTX-3 levels between the different groups. Correlation analysis and receiver operating characteristic (ROC) analysis were used to analyze clinical data. The levels of PTX-3 increased in the LCa groups. PTX-3 levels were higher in the small cell lung cancer (SCLC) compared to non-small-cell lung cancer (NSCLC) groups. In LCa patients, obstructive pneumonia could upregulate the expression of PTX-3 in BALF. The area under the ROC curve of PTX-3 in BALF during LCa diagnosis, SCLC, and LCa with obstructive pneumonia was 0.949 (p ≤ 0.001), 0.672 (p < 0.05), and 0.838 (p < 0.01), respectively. In conclusion, PTX-3 in BALF has a potential value as an LCa biomarker, particularly in cases of SCLC and LCa with obstructive pneumonia.

Acute phase protein response to viral infection and vaccination

Organisms respond in multiple ways to microbial infections. Pathogen invasion tipically triggers an inflammatory response where acute phase proteins (APP) have a key role. Pentraxins (PTX) are a family of highly conserved APP that play a part in the host defense against infection. The larger proteins of the family are simply named pentraxins, while c-reactive proteins (CRP) and serum amyloid proteins (SAA, SAP) are known as short pentraxins. Although high APP levels have been broadly associated with bacterial infections, there is a growing body of evidence revealing increased PTX, CRP and SAP expression upon viral infection. Furthermore, CRP, PTX and SAP have shown their potential as diagnostic markers and predictors of disease outcome. Likewise, the measurement of APP levels can be valuable to determine the efficacy of antiviral therapies and vaccines. From the practical point of view, the ability of APP to reduce viral infectivity has been observed in several virus-host models. This has prompted investigation efforts to assess the role of acute phase response proteins as immunoregulatory molecules and their potential as therapeutic reagents. This work aims to present an overview of the APP response to viral infections reviewing the current knowledge in the field.

The Long Pentraxin PTX3 as a Link Between Innate Immunity, Tissue Remodeling, and Cancer

The innate immune system comprises a cellular and a humoral arm. Humoral pattern recognition molecules include complement components, collectins, ficolins, and pentraxins. These molecules are involved in innate immune responses by recognizing microbial moieties and damaged tissues, activating complement, exerting opsonic activity and facilitating phagocytosis, and regulating inflammation. The long pentraxin PTX3 is a prototypic humoral pattern recognition molecule that, in addition to providing defense against infectious agents, plays several functions in tissue repair and regulation of cancer-related inflammation. Characterization of the PTX3 molecular structure and biochemical properties, and insights into its interactome and multiple roles in tissue damage and remodeling support the view that microbial and matrix recognition are evolutionarily conserved functions of humoral innate immunity molecules.

Role of a fluid-phase PRR in fighting an intracellular pathogen: PTX3 in Shigella infection

Shigella spp. are pathogenic bacteria that cause bacillary dysentery in humans by invading the colonic and rectal mucosa where they induce dramatic inflammation. Here, we have analyzed the role of the soluble PRR Pentraxin 3 (PTX3), a key component of the humoral arm of innate immunity. Mice that had been intranasally infected with S. flexneri were rescued from death by treatment with recombinant PTX3. In vitro PTX3 exerts the antibacterial activity against Shigella, impairing epithelial cell invasion and contributing to the bactericidal activity of serum.

PTX3 is produced upon LPS-TLR4 stimulation in accordance with the lipid A structure of Shigella. In the plasma of infected patients, the level of PTX3 amount only correlates strongly with symptom severity. These results signal PTX3 as a novel player in Shigella pathogenesis and its potential role in fighting shigellosis. Finally, we suggest that the plasma level of PTX3 in shigellosis patients could act as a biomarker for infection severity.

Soluble pattern recognition molecules, PRMs, are components of the humoral arm of innate immunity. The long pentraxin 3, PTX3, is a prototypic soluble PRM that is produced in response to primary inflammatory signals. Shigella spp. are human entero-pathogens which invade colonic and rectal mucosa where they cause deleterious inflammation. We show that PTX3 acts as an ante-antibody and contributes to the clearance of extracellular Shigella. As a countermeasure, Shigella uses invasiveness and low-inflammatory LPS to control PTX3 release in infected cells. This study highlights that the extracellular phase of the invasion process can be considered the “Achille heels” of Shigella pathogenesis.

PTX3, a Humoral Pattern Recognition Molecule, in Innate Immunity, Tissue Repair, and Cancer

Innate immunity includes a cellular and a humoral arm. PTX3 is a fluid-phase pattern recognition molecule conserved in evolution which acts as a key component of humoral innate immunity in infections of fungal, bacterial, and viral origin. PTX3 binds conserved microbial structures and self-components under conditions of inflammation and activates effector functions (complement, phagocytosis). Moreover, it has a complex regulatory role in inflammation, such as ischemia/reperfusion injury and cancer-related inflammation, as well as in extracellular matrix organization and remodeling, with profound implications in physiology and pathology. Finally, PTX3 acts as an extrinsic oncosuppressor gene by taming tumor-promoting inflammation in murine and selected human tumors. Thus evidence suggests that PTX3 is a key homeostatic component at the crossroad of innate immunity, inflammation, tissue repair, and cancer. Dissecting the complexity of PTX3 pathophysiology and human genetics paves the way to diagnostic and therapeutic exploitation.

XB130 deficiency enhances lipopolysaccharide-induced septic response and acute lung injury

XB130 is a novel oncoprotein that promotes cancer cell survival, proliferation and migration. Its physiological function in vivo is largely unknown. The objective of this study was to determine the role of XB130 in lipopolysaccharide (LPS)-induced septic responses and acute lung injury. LPS was intraperitoneally administrated to Xb130 knockout (KO) and wild type (WT) mice. There was a significant weight loss in KO mice at Day 2 and significantly higher disease scores during the 7 days of observation. The levels of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, interleukin-6 and interleukin-10 in the serum were significantly higher in KO mice at Day 2. In KO mice there were a significantly higher lung injury score, higher wet/dry lung weight ratio, more apoptotic cells and less proliferative cells in the lung. Macrophage infiltration was significantly elevated in the lung of KO mice. There was significantly increased number of p-GSK-3β positive cells in KO mice, which were mainly neutrophils and macrophages. XB130 is expressed in alveolar type I and type II cells in the lung. The expression in these cells was significantly reduced after LPS challenge. XB130 deficiency delayed the recovery from systemic septic responses, and the presence of XB130 in the alveolar epithelial cells may provide protective mechanisms by reducing cell death and promoting cell proliferation, and reducing pulmonary permeability.

Pentraxin 3 deficiency enhances features of chronic rejection in a mouse orthotopic lung transplantation model

Chronic lung allograft dysfunction (CLAD) is a serious complication after lung transplantation and thought to represent chronic rejection. Increased expression of Pentraxin 3 (PTX3), an acute phase protein, was associated with worse outcome in lung transplant patients. To determine the role of recipient PTX3 in development of chronic rejection, we used a minor alloantigen-mismatched murine orthotopic single lung transplant model. Male C57BL/10 mice were used as donors. Male PTX3 knockout (KO) mice and their wild type (WT) littermates on 129/SvEv/C57BL6/J background were used as recipients. In KO recipients, 7/13 grafted lungs were consolidated without volume recovery on CT scan, while only 2/9 WT mice showed similar graft consolidation. For grafts where lung volume could be reliably analyzed by CT scan, the lung volume recovery was significantly reduced in KO mice compared to WT. Interstitial inflammation, parenchymal fibrosis and bronchiolitis obliterans scores were significantly higher in KO mice. Presence of myofibroblasts and lymphoid aggregation was significantly enhanced in the grafts of PTX3 KO recipients. Recipient PTX3 deficiency enhanced chronic rejection-like lesions by promoting a fibrotic process in the airways and lung parenchyma. The underlying mechanisms and potential protective role of exogenous PTX3 as a therapy should be further explored.

Acute ethanol intoxication suppresses pentraxin 3 expression in a mouse sepsis model involving cecal ligation and puncture

Acute ethanol intoxication impairs immunological reactions and increases the risk of sepsis; however, the underlying mechanism remains unclear. Pentraxin (PTX) 3 is a humoral pattern recognition receptor whose levels rapidly increase in response to inflammation. PTX3 production is triggered by tumor necrosis factor (TNF)-α and is mediated by c-Jun N-terminal kinase (JNK). As PTX3 exerts protective effects against sepsis as well as acute lung injury, we investigated whether acute ethanol exposure exacerbates sepsis by altering PTX3 expression. Sepsis was induced in C57/BL6 mice by cecal ligation and puncture (CLP) after ethanol/saline administration. Survival rates were significantly lower in ethanol-treated than in saline-treated mice. Increased vascular permeability and attenuation of PTX3 expression were observed in the lungs of ethanol-treated mice 4 h after CLP. Concomitant with a delayed increase of plasma TNF-α in ethanol-treated mice, plasma PTX3 was also suppressed in the early phase of sepsis. Although TNF-α level in ethanol-treated mice exceeded that in saline-treated mice 16 h after CLP, PTX3 levels were still suppressed in the former group. JNK phosphorylation in lung tissue was suppressed in both groups 4 and 16 h after CLP. Furthermore, JNK phosphorylation in ethanol-treated human umbilical vein endothelial cells was suppressed even in the presence of exogenous TNF-α, resulting in inhibition of PTX3 mRNA and protein expression. Our results suggest that ethanol suppresses de novo PTX3 synthesis via two mechanisms - i.e., suppression of TNF-α production and inhibition of JNK phosphorylation. PTX3 suppression may therefore contribute to exacerbation of sepsis in acute ethanol intoxication.

Pentraxin-3 modulates lipopolysaccharide-induced inflammatory response and attenuates liver injury

Acute-on-chronic liver injury is characterized by an important inflammatory response frequently associated with endotoxemia. In this context, acute-phase proteins such as Pentraxin-3 (PTX3) are released; however, little is known about their role in chronic liver disease. The aim of this study was to elucidate the role of PTX3 in liver injury. The role of PTX3 was evaluated in cultured human cells, liver tissue slices, and mice with acute-on-chronic liver injury. PTX3 expression was assessed in tissue and serum samples from 54 patients with alcoholic hepatitis. PTX3 expression was up-regulated in animal models of liver injury and strongly induced by lipopolysaccharide (LPS). Liver cell fractionation showed that macrophages and activated hepatic stellate cells were the main cell types expressing PTX3 in liver injury. Ex vivo and in vivo studies showed that PTX3 treatment attenuated LPS-induced liver injury, inflammation, and cell recruitment. Mechanistically, PTX3 mediated the hepatic stellate cell wound-healing response. Moreover, PTX3 modulated LPS-induced inflammation in human primary liver macrophages and peripheral monocytes by enhancing a TIR domain-containing adapter-inducing interferon-dependent response and favoring a macrophage interleukin-10-like phenotype. Additionally, hepatic and plasma PTX3 levels were increased in patients with alcoholic hepatitis, a prototypic acute-on-chronic condition; and its expression correlated with disease severity scores, endotoxemia, infections, and short-term mortality, thus suggesting that expression of PTX3 found in patients could be a counterregulatory response to injury.

CONCLUSION

Experimental and human evidence suggests that, in addition to being a potential biomarker for alcoholic hepatitis, PTX3 participates in the wound-healing response and attenuates LPS-induced liver injury and inflammation; therefore, administration of PTX3 could be a promising therapeutic strategy in acute-on-chronic conditions, particularly those associated with endotoxemia. (Hepatology 2017;66:953-968).

Intraperitoneal adoptive transfer of mesenchymal stem cells enhances recovery from acid aspiration acute lung injury in mice

Background

Mesenchymal stem cells (MSCs) might act as fine-tuners of inflammation during acute lung injury. We assessed the effects of adoptive transfer of MSCs in acid aspiration acute lung injury and explored the role of long pentraxin PTX3.

Methods

We conducted a prospective experimental interventional study on wild-type (WT) and PTX3-deficient (PTX3^−/−) mice. Acute lung injury was induced in WT and PTX3^−/− mice by instillation of hydrochloric acid into the right bronchus. One hour later, animals received intraperitoneal sterile phosphate-buffered saline (PBS), WT-MSCs (1 × 10⁶) or PTX3^−/−-MSCs (1 × 10⁶). Twenty-four hours after injury, we measured the effects of treatments on arterial blood gases, wet/dry lung weight (W/D), CT scan analysis of lung collapse, neutrophils, TNFα and CXCL1 in bronchoalveolar lavage, and plasma PTX3. d-dimer was assayed in 1 week and OH-proline in 2 weeks to track the fibrotic evolution.

Results

In 24 h, in comparison to PBS, WT-MSCs improved oxygenation and reduced W/D and alveolar collapse. These effects were associated with decreased concentrations of alveolar neutrophils and cytokines. WT-MSCs increased d-dimer concentration and decreased OH-proline levels, too.

Treatment with PTX3^−/−-MSCs ameliorated oxygenation, W/D, and alveolar TNFα, though to a lesser extent than WT-MSCs. PTX3^−/−-MSCs did not improve lung collapse, neutrophil count, CXCL1, d-dimer, and OH-proline concentrations. The protective effects of WT-MSCs were dampened by lack of endogenous PTX3, too.

Conclusions

In acid aspiration acute lung injury, MSCs improve pulmonary function and limit fibrosis by fine-tuning inflammation. The role of PTX3 in determining MSCs’ effects might merit further scrutiny.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-017-0126-5) contains supplementary material, which is available to authorized users.

Interplay between Myeloid Cells and Humoral Innate Immunity

The innate immune system represents the first line of defense against pathogens and comprises both a cellular and a humoral arm. Fluid-phase pattern recognition molecules (PRMs), which include collectins, ficolins, and pentraxins, are key components of the humoral arm of innate immunity and are expressed by a variety of cells, including myeloid, epithelial, and endothelial cells, mainly in response to infectious and inflammatory conditions. Soluble PRMs share basic multifunctional properties including activation and regulation of the complement cascade, opsonization of pathogens and apoptotic cells, regulation of leukocyte extravasation, and fine-tuning of inflammation. Therefore, soluble PRMs are part of the immune response and retain antibody-like effector functions. Here, we will review the expression and general function of soluble PRMs, focusing our attention on the long pentraxin PTX3.

Innate immunity, hemostasis and matrix remodeling: PTX3 as a link

Innate immunity is evolutionarily connected with hemostasis. PTX3 is an essential fluid-phase pattern recognition molecule of the innate immune system that acts as a functional ancestor of antibodies. PTX3 by interacting with defense collagens and fibrinogens amplifies effector functions of the innate immune system. At wound sites, PTX3 regulates the injury-induced thrombotic response and promotes wound healing by favoring timely fibrinolysis. Therefore, PTX3 interacts with ancestral domains conserved in innate immunity, hemostasis and extracellular matrix and exerts functions related to both antimicrobial resistance and tissue repair. These findings strengthen the connection between innate immune system and hemostasis, and suggest that recognition of microbes and extracellular matrix are evolutionarily conserved and integrated functions of the innate immune system.

Humoral innate immunity at the crossroad between microbe and matrix recognition: The role of PTX3 in tissue damage

Innate immunity is involved in regulating inflammatory and tissue repair responses to injury. In particular, humoral innate immunity plays functions related to wound clearance from tissue debris, and regulation of macrophage and stromal cell activities. PTX3, a component of humoral innate immunity, orchestrates tissue repair by interacting with plasminogen and fibrin. Fluid-phase molecules of innate immunity interact with elements of the extracellular matrix, and some of the latter display opsonic activity against certain bacterial species.

Thus, recognition of extracellular matrix and microbial components is a recurrent theme in the humoral arm of the innate immune system.

The Dual Complexity of PTX3 in Health and Disease: A Balancing Act?

The humoral arm of innate immunity is complex and includes various molecules that serve as markers of inflammation with complementary characteristics, such as the short pentraxins C-reactive protein (CRP) and serum amyloid P (SAP) and the long pentraxin PTX3. There is a growing amount of evidence – including mouse and human genetics – that suggests that PTX3 is essential in conferring host resistance against selected pathogens and, moreover, that it plays a dual antagonistic role in the regulation of inflammation. Dissection of such a yin-and-yang role of pentraxins in immunity and inflammation is timely and significant as it may pave the way for better clinical exploitation against various diseases.

The long pentraxin PTX3 is an essential component of humoral innate immunity and plays a role in the regulation of inflammation.

PTX3 has complex effects on the vasculature, including an interaction with the angiogenic growth factor FGF2 and the regulation of vessel wall tone.

By modulating complement-driven inflammation, PTX3 acts as an oncosuppressor gene in mice and selected human tumors.

By interacting with provisional matrix components, PTX3 contributes to the orchestration of wound healing and tissue repair/remodeling.

PTX3 and the related pentraxins C-reactive protein (CRP) and serum amyloid P (SAP) can exert dual roles in inflammation and antimicrobial resistance, by either exerting a protective function or amplifying tissue damage.

Dissection of the yin–yang role of pentraxins in immunopathology may pave the way towards better exploitation of these molecules as envisaged disease markers and candidate therapeutic agents.

Neutrophils in respiratory syncytial virus infection: A target for asthma prevention

Lower respiratory tract infections by respiratory syncytial virus (RSV) are the foremost cause of infant hospitalization and are implicated in lasting pulmonary impairment and the development of asthma. Neutrophils infiltrate the airways of pediatric patients with RSV-induced bronchiolitis in vast numbers: approximately 80% of infiltrated cells are neutrophils. However, why neutrophils are recruited to the site of viral respiratory tract infection is not clear. In this review we discuss the beneficial and pathologic contributions of neutrophils to the immune response against RSV infection. Neutrophils can limit viral replication and spread, as well as stimulate an effective antiviral adaptive immune response. However, low specificity of neutrophil antimicrobial armaments allows for collateral tissue damage. Neutrophil-induced injury to the airways during the delicate period of infant lung development has lasting adverse consequences for pulmonary architecture and might promote the onset of asthma in susceptible subjects. We suggest that pharmacologic modulation of neutrophils should be explored as a viable future therapy for severe RSV-induced bronchiolitis and thereby prevent the inception of subsequent asthma. The antiviral functions of neutrophils suggest that targeting of neutrophils in patients with RSV-induced bronchiolitis is best performed under the umbrella of antiviral treatment.

IL-6 trans-signaling increases expression of airways disease genes in airway smooth muscle

Genetic data suggest that IL-6 trans-signaling may have a pathogenic role in the lung; however, the effects of IL-6 trans-signaling on lung effector cells have not been investigated. In this study, human airway smooth muscle (HASM) cells were treated with IL-6 (classical) or IL-6+sIL6R (trans-signaling) for 24 h and gene expression was measured by RNAseq. Intracellular signaling and transcription factor activation were assessed by Western blotting and luciferase assay, respectively. The functional effect of IL-6 trans-signaling was determined by proliferation assay. IL-6 trans-signaling had no effect on phosphoinositide-3 kinase and Erk MAP kinase pathways in HASM cells. Both classical and IL-6 trans-signaling in HASM involves activation of Stat3. However, the kinetics of Stat3 phosphorylation by IL-6 trans-signaling was different than classical IL-6 signaling. This was further reflected in the differential gene expression profile by IL-6 trans-signaling in HASM cells. Under IL-6 trans-signaling conditions 36 genes were upregulated, including PLA2G2A, IL13RA1, MUC1, and SOD2. Four genes, including CCL11, were downregulated at least twofold. The expression of 112 genes was divergent between IL-6 classical and trans-signaling, including the genes HILPDA, NNMT, DAB2, MUC1, WWC1, and VEGFA. Pathway analysis revealed that IL-6 trans-signaling induced expression of genes involved in regulation of airway remodeling, immune response, hypoxia, and glucose metabolism. Treatment of HASM cells with IL-6+sIL6R induced proliferation in a dose-dependent fashion, suggesting a role for IL-6 trans-signaling in asthma pathogenesis. These novel findings demonstrate differential effect of IL-6 trans-signaling on airway cells and identify IL-6 trans-signaling as a potential modifier of airway inflammation and remodeling.

Role of pentraxin 3 in shaping arthritogenic alphaviral disease: from enhanced viral replication to immunomodulation

The rising prevalence of arthritogenic alphavirus infections, including chikungunya virus (CHIKV) and Ross River virus (RRV), and the lack of antiviral treatments highlight the potential threat of a global alphavirus pandemic. The immune responses underlying alphavirus virulence remain enigmatic. We found that pentraxin 3 (PTX3) was highly expressed in CHIKV and RRV patients during acute disease. Overt expression of PTX3 in CHIKV patients was associated with increased viral load and disease severity. PTX3-deficient (PTX3(-/-)) mice acutely infected with RRV exhibited delayed disease progression and rapid recovery through diminished inflammatory responses and viral replication. Furthermore, binding of the N-terminal domain of PTX3 to RRV facilitated viral entry and replication. Thus, our study demonstrates the pivotal role of PTX3 in shaping alphavirus-triggered immunity and disease and provides new insights into alphavirus pathogenesis.

The yin-yang of long pentraxin PTX3 in inflammation and immunity

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CRP and PTX3 are prototypical short and long pentraxin respectively.

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They are both soluble pattern recognition molecule involved in the innate immune and inflammatory response.

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PTX3 but not CRP is conserved in mouse and men and gene-modified mice help in the understanding of the biological properties.

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Protective and detrimental roles are exerted by PTX3.

Pentraxins are a family of multimeric proteins characterized by the presence of a pentraxin signature in their C-terminus region. Based on the primary structure, pentraxins are divided into short and long pentraxin: C-reactive protein (CRP) is the prototype of the short pentraxin subfamily while pentraxin 3 (PTX3) is the prototypic long pentraxin. Despite these two molecules exert similar fundamental actions in the regulation of innate immune and inflammatory responses, several differences exist between CRP and PTX3, including gene organization, protein oligomerization and expression pattern. The pathophysiological roles of PTX3 have been investigated using genetically modified mice since PTX3 gene organization and regulation are well conserved between mouse and human. Such in vivo studies figured out that PTX3 mainly have host-protective effects, even if it could also exert negative effects under certain pathophysiologic conditions. Here we will review the general properties of CRP and PTX3, emphasizing the differences between the two molecules and the regulatory functions exerted by PTX3 in innate immunity and inflammation.

Constitutive expression of pentraxin 3 (PTX3) protein by human amniotic membrane cells leads to formation of the heavy chain (HC)-hyaluronan (HA)-PTX3 complex

Heavy chain (HC)-hyaluronan (HA), a complex formed by the covalent linkage between HC1 from the inter-α-trypsin inhibitor (IαI) and HA, purified from the human amniotic membrane (AM), is responsible for the anti-inflammatory, antiscarring, and antiangiogenic actions of the AM. This HC-HA complex is produced by constitutive expression of TNF-stimulated gene 6 and endogenous production of IαI by AM cells. Pentraxin 3 (PTX3), a prototypic long pentraxin that plays a non-redundant role in innate immunity against selected pathogens, also helps stabilize HC-HA to ensure female fertility. Here we noted strong positive PTX3 staining in the AM epithelium and compact stroma. PTX3 was constitutively expressed and secreted by cultured AM epithelial and stromal cells and, further, greatly up-regulated by TNF and IL-1β. Using an agarose overlay to trap the HA-containing matrix, the HC-HA-PTX3 complex was formed, as analyzed by Western blot analysis, by AM cells but not human skin fibroblasts, despite being cultured in the presence of serum and TNF. However, exogenous PTX3 helps human skin fibroblasts form the HC-HA-PTX3 complex with an agarose overlay. Furthermore, PTX3 can be coimmunoprecipitated with the HC-HA complex from agarose-overlaid AM cell extracts by an anti-human IαI antibody. Such a HC-HA-PTX3 complex can be reconstituted in vitro and exhibit similar effects as those reported for AM HC-HA-PTX3 on polarization of M2 macrophages. The tight binding between PTX3 and AM HC-HA withstands four runs of CsCl ultracentrifugation in the presence of 4 m GnHCl. These results indicate that PTX3 is constitutively expressed and secreted by AM cells as an integral component of the AM HC-HA-PTX3 complex and contributes to the biological function of AM HC-HA-PTX3.

A single amino acid substitution in the hemagglutinin of H3N2 subtype influenza A viruses is associated with resistance to the long pentraxin PTX3 and enhanced virulence in mice

The long pentraxin, pentraxin 3 (PTX3), can play beneficial or detrimental roles during infection and disease by modulating various aspects of the immune system. There is growing evidence to suggest that PTX3 can mediate antiviral activity in vitro and in vivo. Previous studies demonstrated that PTX3 and the short pentraxin serum amyloid P express sialic acids that are recognized by the hemagglutinin (HA) glycoprotein of certain influenza A viruses (IAV), resulting in virus neutralization and anti-IAV activity. In this study, we demonstrate that specificity of both HA and the viral neuraminidase for particular sialic acid linkages determines the susceptibility of H1N1, H3N2, and H7N9 strains to the antiviral activities of PTX3 and serum amyloid P. Selection of H3N2 virus mutants resistant to PTX3 allowed for identification of amino acid residues in the vicinity of the receptor-binding pocket of HA that are critical determinants of sensitivity to PTX3; this was supported by sequence analysis of a range of H3N2 strains that were sensitive or resistant to PTX3. In a mouse model of infection, the enhanced virulence of PTX3-resistant mutants was associated with increased virus replication and elevated levels of proinflammatory cytokines in the airways, leading to pulmonary inflammation and lung injury. Together, these studies identify determinants in the viral HA that can be associated with sensitivity to the antiviral activities of PTX3 and highlight its importance in the control of IAV infection.

The pathogenesis of nephropathia epidemica: new knowledge and unanswered questions

Puumala virus (PUUV) causes an acute hemorrhagic fever with renal syndrome (HFRS), a zoonosis also called nephropathia epidemica (NE). The reservoir host of PUUV is the bank vole (Myodes glareolus). Herein we review the main clinical manifestations of NE, acute kidney injury, increased vascular permeability, coagulation abnormalities as well as pulmonary, cardiac, central nervous system and ocular manifestations of the disease. Several biomarkers of disease severity have recently been discovered: interleukin-6, pentraxin-3, C-reactive protein, indoleamine 2,3-dioxygenase, cell-free DNA, soluble urokinase-type plasminogen activator, GATA-3 and Mac-2 binding protein. The role of cytokines, vascular endothelial growth hormone, complement, bradykinin, cellular immune response and other mechanisms in the pathogenesis of NE as well as host genetic factors will be discussed. Finally therapeutic aspects and directions for further research will be handled.

A network integration approach to predict conserved regulators related to pathogenicity of influenza and SARS-CoV respiratory viruses

Respiratory infections stemming from influenza viruses and the Severe Acute Respiratory Syndrome corona virus (SARS-CoV) represent a serious public health threat as emerging pandemics. Despite efforts to identify the critical interactions of these viruses with host machinery, the key regulatory events that lead to disease pathology remain poorly targeted with therapeutics. Here we implement an integrated network interrogation approach, in which proteome and transcriptome datasets from infection of both viruses in human lung epithelial cells are utilized to predict regulatory genes involved in the host response. We take advantage of a novel “crowd-based” approach to identify and combine ranking metrics that isolate genes/proteins likely related to the pathogenicity of SARS-CoV and influenza virus. Subsequently, a multivariate regression model is used to compare predicted lung epithelial regulatory influences with data derived from other respiratory virus infection models. We predicted a small set of regulatory factors with conserved behavior for consideration as important components of viral pathogenesis that might also serve as therapeutic targets for intervention. Our results demonstrate the utility of integrating diverse ‘omic datasets to predict and prioritize regulatory features conserved across multiple pathogen infection models.

Pentraxin 3: an immuno-regulator in the lungs

Pentraxin 3 (PTX3) is a soluble pattern recognition receptor that is a humoral component of the innate immune system. It interacts with pathogenic moieties, infected and dying host cells and facilitates their removal through activation of appropriate innate and adaptive mechanisms. PTX3 is secreted by a diverse variety of cells, ranging from immune cells to structural cells, in response to Toll like receptor (TLR) engagement, inflammatory stimuli, and physical and chemical stress. Further, PTX3 plays an essential role in female fertility as it facilitates the organization of extracellular matrix in the cumulus oophorus. Such activity is also implicated in post-inflammation tissue repair. PTX3 is a multifunctional protein and plays a non-redundant role in providing immunity against potential immunological dangers. Thus, we assessed its role in lung immunity, as lungs are at a constant risk of infections and tissue damage that is attributable to perpetual exposure to foreign agents.

The long pentraxin PTX3: a paradigm for humoral pattern recognition molecules

Pattern recognition molecules (PRMs) are components of the humoral arm of innate immunity; they recognize pathogen-associated molecular patterns (PAMP) and are functional ancestors of antibodies, promoting complement activation, opsonization, and agglutination. In addition, several PRMs have a regulatory function on inflammation. Pentraxins are a family of evolutionarily conserved PRMs characterized by a cyclic multimeric structure. On the basis of structure, pentraxins have been operationally divided into short and long families. C-reactive protein (CRP) and serum amyloid P component are prototypes of the short pentraxin family, while pentraxin 3 (PTX3) is a prototype of the long pentraxins. PTX3 is produced by somatic and immune cells in response to proinflammatory stimuli and Toll-like receptor engagement, and it interacts with several ligands and exerts multifunctional properties. Unlike CRP, PTX3 gene organization and regulation have been conserved in evolution, thus allowing its pathophysiological roles to be evaluated in genetically modified animals. Here we will briefly review the general properties of CRP and PTX3 as prototypes of short and long pentraxins, respectively, emphasizing in particular the functional role of PTX3 as a prototypic PRM with antibody-like properties.

The "sweet" side of a long pentraxin: how glycosylation affects PTX3 functions in innate immunity and inflammation

Innate immunity represents the first line of defense against pathogens and plays key roles in activation and orientation of the adaptive immune response. The innate immune system comprises both a cellular and a humoral arm. Components of the humoral arm include soluble pattern recognition molecules (PRMs) that recognize pathogen-associated molecular patterns and initiate the immune response in coordination with the cellular arm, therefore acting as functional ancestors of antibodies. The long pentraxin PTX3 is a prototypic soluble PRM that is produced at sites of infection and inflammation by both somatic and immune cells. Gene targeting of this evolutionarily conserved protein has revealed a non-redundant role in resistance to selected pathogens. Moreover, PTX3 exerts important functions at the crossroad between innate immunity, inflammation, and female fertility. The human PTX3 protein contains a single N-glycosylation site that is fully occupied by complex type oligosaccharides, mainly fucosylated and sialylated biantennary glycans. Glycosylation has been implicated in a number of PTX3 activities, including neutralization of influenza viruses, modulation of the complement system, and attenuation of leukocyte recruitment. Therefore, this post translational modification might act as a fine tuner of PTX3 functions in native immunity and inflammation. Here we review the studies on PTX3, with emphasis on the glycan-dependent mechanisms underlying pathogen recognition and crosstalk with other components of the innate immune system.

Host-protective effect of circulating pentraxin 3 (PTX3) and complex formation with neutrophil extracellular traps

Pentraxin 3 (PTX3) is a soluble pattern recognition receptor which is classified as a long-pentraxin in the pentraxin family. It is known to play an important role in innate immunity, inflammatory regulation, and female fertility. PTX3 is synthesized by specific cells, primarily in response to inflammatory signals. Among these various cells, neutrophils have a unique PTX3 production system. Neutrophils store PTX3 in neutrophil-specific granules and then the stored PTX3 is released and localizes in neutrophil extracellular traps (NETs). Although certain NET components have been identified, such as histones and anti-microbial proteins, the detailed mechanisms by which NETs localize, as well as capture and kill microbes, have not been fully elucidated. PTX3 is a candidate diagnostic marker of infection and vascular damage. In severe infectious diseases such as sepsis, the circulating PTX3 concentration increases greatly (up to 100 ng/mL, i.e., up to 100-fold of the normal level). Even though it is clearly implied that PTX3 plays a protective role in sepsis and certain other disorders, the detailed mechanisms by which it does so remain unclear. A proteomic study of PTX3 ligands in septic patients revealed that PTX3 forms a complex with certain NET component proteins. This suggests a role for PTX3 in which it facilitates the efficiency of anti-microbial protein pathogen clearance by interacting with both pathogens and anti-microbial proteins. We discuss the possible relationships between PTX3 and NET component proteins in the host protection afforded by the innate immune response. The PTX3 complex has the potential to be a highly useful diagnostic marker of sepsis and other inflammatory diseases.