Serum Amyloid P inhibits single stranded RNA-induced lung inflammation, lung damage, and cytokine storm in mice.

SARS-CoV-2 is a single stranded RNA (ssRNA) virus and contains GU-rich sequences distributed abundantly in the genome. In COVID-19, the infection and immune hyperactivation causes accumulation of inflammatory immune cells, blood clots, and protein aggregates in lung fluid, increased lung alveolar wall thickness, and upregulation of serum cytokine levels. A serum protein called serum amyloid P (SAP) has a calming effect on the innate immune system and shows efficacy as a therapeutic for fibrosis in animal models and clinical trials. Here we show that aspiration of the GU-rich ssRNA oligonucleotide ORN06 into mouse lungs induces all of the above COVID-19-like symptoms. Men tend to have more severe COVID-19 symptoms than women, and in the aspirated ORN06 model, male mice tended to have more severe symptoms than female mice. Intraperitoneal injections of SAP starting from day 1 post ORN06 aspiration attenuated the ORN06-induced increase in the number of inflammatory cells and formation of clot-like aggregates in the mouse lung fluid, reduced ORN06-increased alveolar wall thickness and accumulation of exudates in the alveolar airspace, and attenuated an ORN06-induced upregulation of the inflammatory cytokines IL-1ß, IL-6, IL-12p70, IL-23, and IL-27 in serum. SAP also reduced D-dimer levels in the lung fluid. In human peripheral blood mononuclear cells, SAP attenuated ORN06-induced extracellular accumulation of IL-6. Together, these results suggest that aspiration of ORN06 is a simple model for both COVID-19 as well as cytokine storm in general, and that SAP is a potential therapeutic for diseases with COVID-19-like symptoms and/or a cytokine storm.

Long-term treatment with recombinant human pentraxin 2 protein in patients with idiopathic pulmonary fibrosis: an open-label extension study.

BACKGROUND: Patients with idiopathic pulmonary fibrosis (IPF) treated with PRM-151, a recombinant human pentraxin 2 protein, in a phase 2 double-blind, randomised controlled trial had significantly reduced decline in percentage of predicted forced vital capacity (FVC) and stabilised 6-min walking distance compared with placebo over a 28-week period. Here we report the 76-week results of an open-label extension study. METHODS: Patients who completed the 28-week double-blind period of the PRM-151-202 trial were eligible to participate in the open-label extension study. Patients previously enrolled in the PRM-151 group continued this treatment and those previously in the placebo group crossed over to PRM-151. All patients received PRM-151 in 28-week cycles with loading doses of 10 mg/kg by 60 min intravenous infusions on days 1, 3, and 5 in the first week of each cycle followed by one infusion of 10 mg/kg every 4 weeks. The primary objective of the open-label extension study was to assess the long-term safety and tolerability of PRM-151, which were assessed by analysing adverse events (AEs) up to week 76 in all patients who received at least one dose of PRM-151 during the open-label extension study. Exploratory efficacy analyses were done by assessing changes from baseline in percentage of predicted FVC and 6-min walking distance, with descriptive statistics to week 76 and with random-intercept mixed models to week 52. This study is registered with ClinicalTrials.gov, number NCT02550873, and with EudraCT, number 2014-004782-24. FINDINGS: Of 116 patients who completed the double-blind treatment period, 111 entered the open-label extension study (74 from the PRM-151 group and 37 from the placebo group). 84 (76%) of 111 patients received concomitant IPF therapy (pirfenidone n=55 or nintedanib n=29). AEs were consistent with long-term IPF sequelae. 31 (28%) patients had serious AEs. Those occurring in two or more patients were pneumonia (six [5%] of 111), IPF exacerbation (four [4%]), IPF progression (four [4%]), and chest pain (two [2%]). 21 (19%) patients had severe AEs, of which IPF exacerbation and IPF progression each occurred in two (2%) patients. Two (2%) patients experienced life-threatening AEs (one had pneumonia and one had small-cell lung cancer extensive stage). A persistent treatment effect was observed for PRM-151 in patients who continued treatment, with a decline in percentage of predicted FVC of -3·6% per year and in 6-min walking distance of -10·5 m per year at week 52. In patients who started PRM-151 during the open-label extension study, compared with the slopes for placebo, decline reduced for percentage of predicted FVC (from -8·7% per year in weeks 0-28 to -0·9% per year in weeks 28-52, p<0·0001) and 6-min walking distance (from -54·9 m per year to -3·5 m per year, p=0·0224). INTERPRETATION: Long-term treatment with PRM-151 was well tolerated and the effects on percentage of predicted FVC and 6-min walking distance were persistent on continuation and positive in patients who crossed over from placebo. These findings support further study of PRM-151 in larger populations of patients with IPF. FUNDING: Promedior.

The Development of Serum Amyloid P as a Possible Therapeutic.

Pentraxins such as serum amyloid P (SAP; also known as PTX2) regulate several aspects of the innate immune system. SAP inhibits the differentiation of monocyte-derived fibroblast-like cells called fibrocytes, promotes the formation of immuno-regulatory macrophages, and inhibits neutrophil adhesion to extracellular matrix proteins. In this minireview, we describe how these effects of SAP have led to its possible use as a therapeutic, and how modulating SAP effects might be used for other therapeutics. Fibrosing diseases such as pulmonary fibrosis, cardiac fibrosis, liver fibrosis, and renal fibrosis are associated with 30-45% of deaths in the US. Fibrosis involves both fibrocyte differentiation and profibrotic macrophage differentiation, and possibly because SAP inhibits both of these processes, in 9 different animal models, SAP inhibited fibrosis. In Phase 1B and Phase 2 clinical trials, SAP injections reduced the decline in lung function in pulmonary fibrosis patients, and in a small Phase 2 trial SAP injections reduced fibrosis in myelofibrosis patients. Acute respiratory distress syndrome/ acute lung injury (ARDS/ALI) involves the accumulation of neutrophils in the lungs, and possibly because SAP inhibits neutrophil adhesion, SAP injections reduced the severity of ARDS in an animal model. Conversely, depleting SAP is a potential therapeutic for amyloidosis, topically removing SAP from wound fluid speeds wound healing in animal models, and blocking SAP binding to one of its receptors makes cultured macrophages more aggressive toward tuberculosis bacteria. These results suggest that modulating pentraxin signaling might be useful for a variety of diseases.

Effect of Recombinant Human Pentraxin 2 vs Placebo on Change in Forced Vital Capacity in Patients With Idiopathic Pulmonary Fibrosis: A Randomized Clinical Trial.

Importance: Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with poor prognosis. Approved therapies do not halt disease progression. Objective: To determine the effect of recombinant human pentraxin 2 vs placebo on change from baseline to week 28 in mean forced vital capacity (FVC) percentage of predicted value. Design, Setting, and Participants: Phase 2, randomized, double-blind, placebo-controlled trial conducted at 18 sites in 7 countries of eligible patients with IPF (N = 117; aged 40-80 years; FVC ≥50% and ≤90% predicted; ratio of forced expiratory volume in the first second/FVC >0.70; diffusing capacity for carbon monoxide [Dlco] ≥25% and ≤90% predicted; and distance of ≥150 m on the 6-minute walk test). Study period was August 2015-May 2017. Interventions: Patients were randomized to receive either recombinant human pentraxin 2 (10 mg/kg intravenous every 4 weeks, n = 77) or placebo (n = 39) for 24 weeks, and stratified by concurrent IPF treatment status. Main Outcomes and Measures: The primary end point was the least-squares mean change in FVC percentage of predicted value from baseline to week 28 (minimal clinically important difference, decline of 2%-6%). Secondary end points included mean change in lung volumes (total, normal, and interstitial lung abnormalities) on high-resolution computed tomography (HRCT) and 6-minute walk distance (minimal clinically important difference, 24-45 m). Results: Of 117 randomized patients, 116 received at least 1 dose of study drug (mean age, 68.6 years; 81.0% men; mean time since IPF diagnosis, 3.8 years), and 111 (95.7%) completed the study. The least-squares mean change in FVC percentage of predicted value from baseline to week 28 in patients treated with recombinant human pentraxin 2 was -2.5 vs -4.8 for those in the placebo group (difference, +2.3 [90% CI, 1.1 to 3.5]; P = .001). No significant treatment differences were observed in total lung volume (difference, 93.5 mL [90% CI, -27.7 to 214.7]), quantitative parenchymal features on HRCT (normal lung volume difference, -1.2% [90% CI, -4.4 to 1.9]; interstitial lung abnormalities difference, 1.1% [90% CI, -2.2 to 4.3]), or measurement of Dlco (difference, -0.4 [90% CI, -2.6 to 1.7]). The change in 6-minute walk distance was -0.5 m for patients treated with recombinant human pentraxin 2 vs -31.8 m for those in the placebo group (difference, +31.3 m [90% CI, 17.4 to 45.1]; P < .001). The most common adverse events in the recombinant human pentraxin 2 vs placebo group were cough (18% vs 5%), fatigue (17% vs 10%), and nasopharyngitis (16% vs 23%). Conclusions and Relevance: In this preliminary study, recombinant human pentraxin 2 vs placebo resulted in a slower decline in lung function over 28 weeks for patients with idiopathic pulmonary fibrosis. Further research should more fully assess efficacy and safety. Trial Registration: clinicaltrials.gov Identifier: NCT02550873.

Protective effect of human serum amyloid P on CCl4-induced acute liver injury in mice.

Human serum amyloid P (hSAP), a member of the pentraxin family, inhibits the activation of fibrocytes in culture and inhibits experimental renal, lung, skin and cardiac fibrosis. As hepatic inflammation is one of the causes of liver fibrosis, in the present study, we investigated the hepatoprotective effects of hSAP against carbon tetrachloride (CCl4)-induced liver injury. Our data indicated that hSAP attenuated hepatic histopathological abnormalities and significantly decreased inflammatory cell infiltration and pro-inflammatory factor expression. Moreover, CCl4-induced apoptosis in the mouse liver was inhibited by hSAP, as measured by terminal-deoxynucleotidyl transferase mediated nick-end labeling (TUNEL) assay and cleaved caspase-3 expression. hSAP significantly restored the expression of B cell lymphoma/leukemia (Bcl)-2 and suppressed the expression of Bcl-2-associated X protein (Bax) in vivo. The number of hepatocytes in early apoptosis stained with Annexin V was significantly reduced by 28-30% in the hSAP treatment group compared with the CCl4 group, and the expression of Bcl-2 was increased, whereas the expression of Bax and cleaved caspase-3 were significantly inhibited in the hSAP pre-treatment group compared with the CCl4 group. hSAP administration also inhibited the migration and activation of hepatic stellate cells (HSCs) in CCl4-injured liver and suppressed the activation of isolated primary HSCs induced by transforming growth factor (TGF)-ß1 in vitro. Collectively, these findings suggest that hSAP exerts a protective effect againts CCl4-induced hepatic injury by suppressing the inflammatory response and hepatocyte apoptosis, potentially by inhibiting HSC activation.

Pentraxins and Collectins: Friend or Foe during Pathogen Invasion?

Innate immunity serves as the frontline defence against invading pathogens. Despite decades of research, new insights are constantly challenging our understanding of host-elicited immunity during microbial infections. Recently, two families of humoral innate immune proteins, pentraxins and collectins, have become a major focus of research in the field of innate immunity. Pentraxins and collectins are key players in activating the humoral arm of innate immunity, taking centre stage in immunoregulation and disease modulation. However, increasing evidence suggests that pentraxins and collectins can also mediate pathogenic effects during some infections. Herein, we discuss the protective and pathogenic effects of pentraxins and collectins, as well as their therapeutic significance.

New Imaging Technology May Help Doctors Diagnose Amyloidosis: Due to stringent FDA rules, U.S. imaging of the disease has lagged behind Europe but a new synthetic molecule may change that.

One December day in 2013, Michael Rasmussen realized that just chewing his food made him tired. Short walks felt draining. At one point, he became so tired that he sat down and didn't get up for three days. Rasmussen had been a man in perfect health. For 30 years, he lived as an artist in the Aleutian Islands in Alaska and walked or biked everywhere. He even bicycled across the United States five times. But now he had slid into a horrible medical mystery.

Rationale for combination therapy in myelofibrosis.

Agents targeting the JAK-STAT pathway have dominated the investigational therapeutic portfolio over the last five years resulting in the first and only approved agent for the treatment of patients with myelofibrosis (MF). However, chromatin modifying agents, anti-fibrosing agents, and other signaling pathway inhibitors have also demonstrated activity and offer the potential to improve upon the clinical success of JAK2 inhibition. Due to the complex pathobiological mechanisms underlying MF, it is likely that a combination of biologically active therapies will be required to target the MF hematopoietic stem cell in order to achieve significant disease course modification. Ruxolitinib in partnership with panobinostat, decitabine, and LDE225 are being evaluated in current combination therapy trials based on pre-clinical studies that provide strong scientific rationale. The rationale of combination of danazol or lenalidomide with ruxolitinib is mainly based on mitigation of anti-JAK2-mediated myelosuppression. Combination trials of ruxolitinib and novel anti-fibrosing agents such as PRM-151 represent an attempt to address therapeutic limitations of JAK2 inhibitors such as reversal of bone marrow fibrosis. Ruxolitinib is also being incorporated in novel treatment strategies in the setting of hematopoietic stem cell transplantation for MF. As the pathogenetic mechanisms are better understood, potential drug combinations in MF will increase dramatically and demonstration of biologic activity in effective preclinical models will be required to efficiently evaluate the most active combinations with least toxicity in future trials. This manuscript will address the proposed goals of combination therapy approach and review the state of the art in combination experimental therapy for MF.

Pentraxin 3 inhibits acute renal injury-induced interstitial fibrosis through suppression of IL-6/Stat3 pathway.

Acute kidney injury-induced organ fibrosis is recognized as a major risk factor for the development of chronic kidney disease, which remains one of the leading causes of death in the developed world. However, knowledge on molecules that may suppress the fibrogenic response after injury is lacking. The long pentraxin 3 (PTX3), a novel acute renal injury marker, has been reported to be involved in chronic renal injury, but the mechanism is still unknown. In this experiment, the mice subjected to acute kidney injury showed a slow recovery of kidney function compared with PTX3-treated animals. Collagen expression was absent in sham-operated kidneys; however, their expression was significantly increased after reperfusion. And, these changes were reduced in PTX3-treated mouse kidney. Fibrosis was associated with increased expression of IL-6 and extensive activation of Stat3. Administration of IL-6 increased collagen I expression and Stat3 activation in vitro in renal epithelial cells subjected to hypoxia-reoxygenation, which was suppressed by PTX3. Furthermore, we found that the decreased serum creatinine level and the reduced expression of collagen and smooth muscle actin induced by PTX3 were abolished by additional administration of IL-6. The associated p-Stat3 expression which was reduced by PTX3 administration was also inverted by additional IL-6 treatment. Our data suggest that PTX3 inhibits acute renal injury-induced interstitial fibrosis through suppression of IL-6/Stat3 pathway.

Long pentraxin PTX3 attenuates ischemia reperfusion injury in a cardiac transplantation model.

UNLABELLED: Ischemia reperfusion (IR) injury is a major issue in cardiac transplantation, and inflammatory processes play a major role in myocardial IR injury. Long pentraxin-3 (PTX3) is a member of a phylogenetically conserved group of acute-phase reactants that are involved in inflammation and innate immunity. In our study, hearts of C57Bl/6 mice were flushed and stored in cold Bretschneider solution for 8 h and then transplanted into syngeneic recipient. We found that both mRNA and protein levels of PTX3 were increased following myocardial IR injury; neutralizing antibody against PTX3 aggravated cardiomyocyte apoptosis and recruitment of neutrophils and macrophages. Troponin T (TnT) production on 24 h after myocardial IR injury was reduced by exogenous PTX3 administration and increased by PTX3 neutralization in comparison with control. Cardiac output at 60 mmHg of afterload pressure was also increased in hearts with exogenous PTX3 administration and decreased with PTX3 neutralization (PTX3: 58.4 ± 7.4 ml/min; CONTROL: 24.5 ± 3.8 ml/min; Anti-PTX3: 11.6 ± 1.7 ml/min; P < 0.05). Furthermore, PTX3 restricted expansion of γδ T cell that was the major source of IL-17A and down-regulated expression of IL-23 and IL-17A. In conclusion, PTX3 played a protective role in cardiomyocyte IR injury. PTX3 ameliorated cardiomyocyte apoptosis and infiltration of neutrophil and macrophage and then improved hemodynamic performance. This was associated with restricted γδ T-cell expansion and decreased IL-23/IL-17A expression.

Response of CFTR-deficient mice to long-term chronic Pseudomonas aeruginosa infection and PTX3 therapy.

BACKGROUND: In cystic fibrosis (CF) patients, chronic lung infection and inflammation due to Pseudomonas aeruginosa contribute to the decline of lung function. The increased prevalence of multidrug resistance among bacteria and the adverse effects of antiinflammatory agents highlight the need for alternative therapeutic approaches that should be tested in a relevant animal model. METHODS: Gut-corrected CF and non-CF mice were chronically infected with a multidrug-resistant P. aeruginosa strain and treated with the long pentraxin PTX3. Body weight, bacterial count, inflammation, and lung pathology were evaluated after 12 days. PTX3 localization in CF sputum specimens was analyzed by immunofluorescence. RESULTS: Chronic P. aeruginosa infection developed similarly in CF and non-CF mice but differed in terms of the inflammatory response. Leukocyte recruitment in the airways, cytokine levels, and chemokine levels were significantly higher in CF mice, compared with non-CF mice. PTX3 treatment, which facilitates phagocytosis of pathogens, reduced P. aeruginosa colonization and restored airway inflammation in CF mice to levels observed in non-CF mice. The presence of PTX3 in CF sputum, in leukocytes, or bound to P. aeruginosa macrocolonies, as well as previous data on PTX3 polymorphisms in colonized CF patients, confirm the relevance of this molecule. CONCLUSIONS: These findings represent a step forward in demonstrating the therapeutic potential of PTX3 in CF.

Effect of PTX3 and voriconazole combination in a rat model of invasive pulmonary aspergillosis.

This study evaluated the pharmacological activity of PTX3, administered in combination with voriconazole, in a rat model of pulmonary aspergillosis. The data indicated additive therapeutic activities of these compounds, as demonstrated by the amelioration of respiratory function changes, reduction of lung fungal burden, and increased survival. Overall, we provide clear evidence that the combination of PTX3 with a suboptimal dose of voriconazole might represent a therapeutic option under those clinical conditions where the use of voriconazole alone is not warranted for efficacy and tolerability reasons.

SAP suppresses the development of experimental autoimmune encephalomyelitis in C57BL/6 mice.

Experimental autoimmune encephalomyelitis (EAE) is a CD4(+) T cell-mediated disease of the central nervous system. Serum amyloid P component (SAP) is a highly conserved plasma protein named for its universal presence in amyloid deposits. Here we report that SAP-transgenic mice had unexpectedly attenuated EAE due to impaired encephalitogenic responses. Following induction with myelin oligodendroglial glycoprotein (MOG) peptide 35-55 in complete Freund's adjuvant, SAP-transgenic mice showed reduced spinal cord inflammation with lower severity of EAE attacks as compared with control C57BL/6 mice. However, in SAP-Knockout mice, the severity of EAE is enhanced. Adoptive transfer of Ag-restimulated T cells from wild type to SAP-transgenic mice, or transfer of SAP-transgenic Ag-restimulated T cells to control mice, induced milder EAE. T cells from MOG-primed SAP-transgenic mice showed weak proliferative responses. Furthermore, in SAP-transgenic mice, there is little infiltration of CD45-positive cells in the spinal cord. In vitro, SAP suppressed the secretion of interleukin-2 stimulated by P-selectin and blocked P-selectin binding to T cells. Moreover, SAP could change the affinity between α4-integrin and T cells. These data suggested that SAP could antagonize the development of the acute phase of inflammation accompanying EAE by modulating the function of P-selectin.

Amelioration of lupus nephritis by serum amyloid P component gene therapy with distinct mechanisms varied from different stage of the disease.

BACKGROUND: Our previous study revealed that administration of syngeneic female BALB/c mice with excessive self activated lymphocyte-derived DNA (ALD-DNA) could induce systemic lupus erythematosus (SLE) disease, indicating that overload of self-DNA might exceed normal clearance ability and comprise the major source of autoantigens in lupus mice. Serum amyloid P component (SAP), an acute-phase serum protein with binding reactivity to DNA in mice, was proved to promote the clearance of free DNA and prevent mice against self-antigen induced autoimmune response. It is reasonable to hypothesize that SAP treatment might contribute to alleviation of SLE disease, whereas its role in ALD-DNA-induced lupus nephritis is not fully understood. METHODOLOGY/PRINCIPAL FINDINGS: The ratios of SAP to DNA significantly decreased and were negatively correlated with the titers of anti-dsDNA antibodies in ALD-DNA-induced lupus mice, indicating SAP was relatively insufficient in lupus mice. Herein a pcDNA3-SAP plasmid (pSAP) was genetically constructed and intramuscularly injected into BALB/c mice. It was found that SAP protein purified from the serum of pSAP-treated mice bound efficiently to ALD-DNA and inhibited ALD-DNA-mediated innate immune response in vitro. Treatment of ALD-DNA-induced lupus mice with pSAP in the early stage of SLE disease with the onset of proteinuria reversed lupus nephritis via decreasing anti-dsDNA autoantibody production and immune complex (IC) deposition. Further administration of pSAP in the late stage of SLE disease that had established lupus nephritis alleviated proteinuria and ameliorated lupus nephritis. This therapeutic effect of SAP was not only attributable to the decreased levels of anti-dsDNA autoantibodies, but also associated with the decreased infiltration of lymphocytes and the reduced production of inflammatory markers. CONCLUSION/SIGNIFICANCE: These results suggest that SAP administration could effectively alleviated lupus nephritis via modulating anti-dsDNA antibody production and the inflammation followed IC deposition, and SAP-based intervening strategy may provide new approaches for treating SLE disease.

Recent progress of Shiga toxin neutralizer for treatment of infections by Shiga toxin-producing Escherichia coli.

Infection with Shiga toxin (Stx)-producing Escherichia coli (STEC), including O157:H7, causes bloody diarrhea and hemorrhagic colitis in humans, occasionally resulting in fatal systemic complications, such as neurological damage and hemolytic-uremic syndrome. Because Stx is a major virulence factor of the infectious disease, a series of Shiga toxin neutralizers with various structural characteristics has been developed as promising therapeutic agents. Most of these agents function to bind to the toxin directly and inhibit the binding to its receptor present on the target cells. Other neutralizers do not inhibit receptor binding but induce aberrant intracellular transport of the toxin, resulting in effective detoxification. Such a novel type of Stx neutralizer provides a new therapeutic strategy against STEC infections. Here, recent progress of the development of Stx neutralizers is reviewed.

Early and transient release of leukocyte pentraxin 3 during acute myocardial infarction.

Pentraxin 3 (PTX3) plays cardioprotective and anti-atherogenic roles in murine models. PTX3 blood levels raise during early acute myocardial infarction (AMI). Neutrophils from healthy subjects physiologically contain PTX3 in secondary (also called specific) granules. In this study, we report that circulating neutrophils release preformed PTX3 in the early phase of AMI (within 6 h from the onset of clinical symptoms). Depletion of intracellular PTX3 correlates with increased plasma levels and with platelet-neutrophil heterotypic aggregates. Neutrophil PTX3 returns to normal values 48 h after the onset of symptoms; concentration does not vary in matched healthy controls or in patients with chronic stable angina. In vitro, recognition of activated P-selectin(+) platelets causes the formation of neutrophil-platelet heteroaggregates and the release of neutrophil PTX3. Purified or membrane-bound P-selectin triggers PTX3 release from resting neutrophils. Released PTX3 binds to activated platelets in vitro. Moreover, PTX3 binds to a substantial fraction of platelets from patients in the circulating blood. PTX3-bound activated platelets have a reduced ability to 1) form heterotypic aggregates with neutrophils and monocytes; 2) activate neutrophils, as evaluated assessing the upregulation of leukocyte ß(2) integrins; 3) aggregate with other platelets; and 4) bind to fibrinogen. Our results suggest that neutrophils early release prestored PTX3 in patients undergoing AMI. PTX3 binds to activated circulating platelets and dampens their proinflammatory and prothrombotic action, thus possibly contributing to its cardioprotective effects.

The therapeutic potential of the humoral pattern recognition molecule PTX3 in chronic lung infection caused by Pseudomonas aeruginosa.

Chronic lung infections by Pseudomonas aeruginosa strains are a major cause of morbidity and mortality in cystic fibrosis (CF) patients. Although there is no clear evidence for a primary defect in the immune system of CF patients, the host is generally unable to clear P. aeruginosa from the airways. PTX3 is a soluble pattern recognition receptor that plays nonredundant roles in the innate immune response to fungi, bacteria, and viruses. In particular, PTX3 deficiency is associated with increased susceptibility to P. aeruginosa lung infection. To address the potential therapeutic effect of PTX3 in P. aeruginosa lung infection, we established persistent and progressive infections in mice with the RP73 clinical strain RP73 isolated from a CF patient and treated them with recombinant human PTX3. The results indicated that PTX3 has a potential therapeutic effect in P. aeruginosa chronic lung infection by reducing lung colonization, proinflammatory cytokine levels (CXCL1, CXCL2, CCL2, and IL-1ß), and leukocyte recruitment in the airways. In models of acute infections and in in vitro assays, the prophagocytic effect of PTX3 was maintained in C1q-deficient mice and was lost in C3- and Fc common γ-chain-deficient mice, suggesting that facilitated recognition and phagocytosis of pathogens through the interplay between complement and FcγRs are involved in the therapeutic effect mediated by PTX3. These data suggested that PTX3 is a potential therapeutic tool in chronic P. aeruginosa lung infections, such as those seen in CF patients.