Human surfactant protein A inhibits SARS-CoV-2 infectivity and alleviates lung injury in a mouse infection model.

Introduction: SARS coronavirus 2 (SARS-CoV-2) infects human angiotensin-converting enzyme 2 (hACE2)-expressing lung epithelial cells through its spike (S) protein. The S protein is highly glycosylated and could be a target for lectins. Surfactant protein A (SP-A) is a collagen-containing C-type lectin, expressed by mucosal epithelial cells and mediates its antiviral activities by binding to viral glycoproteins. Objective: This study examined the mechanistic role of human SP-A in SARS-CoV-2 infectivity and lung injury in vitro and in vivo. Results: Human SP-A can bind both SARS-CoV-2 S protein and hACE2 in a dose-dependent manner (p<0.01). Pre-incubation of SARS-CoV-2 (Delta) with human SP-A inhibited virus binding and entry and reduced viral load in human lung epithelial cells, evidenced by the dose-dependent decrease in viral RNA, nucleocapsid protein (NP), and titer (p<0.01). We observed significant weight loss, increased viral burden, and mortality rate, and more severe lung injury in SARS-CoV-2 infected hACE2/SP-A KO mice (SP-A deficient mice with hACE2 transgene) compared to infected hACE2/mSP-A (K18) and hACE2/hSP-A1 (6A2) mice (with both hACE2 and human SP-A1 transgenes) 6 Days Post-infection (DPI). Furthermore, increased SP-A level was observed in the saliva of COVID-19 patients compared to healthy controls (p<0.05), but severe COVID-19 patients had relatively lower SP-A levels than moderate COVID-19 patients (p<0.05). Discussion: Collectively, human SP-A attenuates SARS-CoV-2-induced acute lung injury (ALI) by directly binding to the S protein and hACE2, and inhibiting its infectivity; and SP-A level in the saliva of COVID-19 patients might serve as a biomarker for COVID-19 severity.

Regulatory roles of SP-A and exosomes in pneumonia-induced acute lung and kidney injuries.

Introduction: Pneumonia-induced sepsis can cause multiple organ dysfunction including acute lung and kidney injury (ALI and AKI). Surfactant protein A (SP-A), a critical innate immune molecule, is expressed in the lung and kidney. Extracellular vesicles like exosomes are involved in the processes of pathophysiology. Here we tested one hypothesis that SP-A regulates pneumonia-induced AKI through the modulation of exosomes and cell death. Methods: Wild-type (WT), SP-A knockout (KO), and humanized SP-A transgenic (hTG, lung-specific SP-A expression) mice were used in this study. Results: After intratracheal infection with Pseudomonas aeruginosa, KO mice showed increased mortality, higher injury scores, more severe inflammation in the lung and kidney, and increased serum TNF-α, IL-1ß, and IL-6 levels compared to WT and hTG mice. Infected hTG mice exhibited similar lung injury but more severe kidney injury than infected WT mice. Increased renal tubular apoptosis and pyroptosis in the kidney of KO mice were found when compared with WT and hTG mice. We found that serum exosomes from septic mice cause ALI and AKI through mediating apoptosis and proptosis when mice were injected intravenously. Furthermore, primary proximal tubular epithelial cells isolated from KO mice showed more sensitivity than those from WT mice after exposure to septic serum exosomes. Discussion: Collectively, SP-A attenuates pneumonia-induced ALI and AKI by regulating inflammation, apoptosis and pyroptosis; serum exosomes are important mediators in the pathogenesis of AKI.

Human Surfactant Protein A Alleviates SARS-CoV-2 Infectivity in Human Lung Epithelial Cells.

SARS coronavirus 2 (SARS-CoV-2) infects human angiotensin-converting enzyme 2 (hACE2)-expressing lung epithelial cells through its spike (S) protein. The S protein is highly glycosylated and could be a target for lectins. Surfactant protein A (SP-A) is a collagen-containing C-type lectin, expressed by mucosal epithelial cells and mediates its antiviral activities by binding to viral glycoproteins. This study examined the mechanistic role of human SP-A in SARS-CoV-2 infectivity. The interactions between human SP-A and SARS-CoV-2 S protein and hACE2 receptor, and SP-A level in COVID-19 patients were assessed by ELISA. The effect of SP-A on SARS-CoV-2 infectivity was analyzed by infecting human lung epithelial cells (A549-ACE2) with pseudoviral particles and infectious SARS-CoV-2 (Delta variant) pre-incubated with SP-A. Virus binding, entry, and infectivity were assessed by RT-qPCR, immunoblotting, and plaque assay. The results showed that human SP-A can bind SARS-CoV-2 S protein/RBD and hACE2 in a dose-dependent manner (p<0.01). Human SP-A inhibited virus binding and entry, and reduce viral load in lung epithelial cells, evidenced by the dose-dependent decrease in viral RNA, nucleocapsid protein, and titer (p<0.01). Increased SP-A level was observed in the saliva of COVID-19 patients compared to healthy controls (p<0.05), but severe COVID-19 patients had relatively lower SP-A levels than moderate COVID-19 patients (p<0.05). Therefore, SP-A plays an important role in mucosal innate immunity against SARS-CoV-2 infectivity by directly binding to the S protein and inhibiting its infectivity in host cells. SP-A level in the saliva of COVID-19 patients might serve as a biomarker for COVID-19 severity.

The Enhancer-Binding Protein MifR, an Essential Regulator of α-Ketoglutarate Transport, Is Required for Full Virulence of Pseudomonas aeruginosa PAO1 in a Mouse Model of Pneumonia.

The opportunistic human pathogen Pseudomonas aeruginosa PAO1 has an extensive metabolism, enabling it to utilize a wide range of structurally diverse compounds to meet its nutritional and energy needs. Interestingly, the utilization of some of the more unusual compounds often associated with a eukaryotic-host environment is regulated via enhancer-binding proteins (EBPs) in P. aeruginosa. Whether the utilization of such compounds and the EBPs involved contribute to the pathogenesis of P. aeruginosa remains to be fully understood. To narrow this gap, we investigated the roles of the EBPs EatR (regulator of ethanolamine catabolism), DdaR (regulator of methylarginine catabolism), and MifR (regulator of α-ketoglutarate or α-KG transport) in the virulence of P. aeruginosa PAO1 in a pneumonia-induced septic mouse model. Deletion of genes encoding EatR and DdaR had no significant effect on the mortality of P. aeruginosa PAO1-infected mice compared to wide-type (WT) PAO1-infected mice. In contrast, infected mice with ΔmifR mutant exhibited a significant reduction (~50%) in the mortality rate compared with WT PAO1 (P < 0.05). Infected mice with ΔmifR PAO1 had lower lung injury scores, fewer inflammatory cells, decreased proinflammatory cytokines, and decreased apoptosis and cell death compared to mice infected with WT PAO1 (P < 0.05). Furthermore, molecular analysis revealed decreased NLRP3 inflammasome activation in infected mice with ΔmifR PAO1 compared to WT PAO1 (P < 0.05). These results suggested that the utilization of α-KG was a contributing factor in P. aeruginosa-mediated pneumonia and sepsis and that MifR-associated regulation may be a potential therapeutic target for P. aeruginosa infectious disease.

Low-Protein, Hypocaloric Nutrition with Glutamine versus Full-Feeding in the Acute Phase in ICU Patients with Severe Traumatic Brain Injury.

OBJECTIVE: To investigate the 28-day mortality, the length of ICU stay, days in the hospital, days of ventilator use, adverse events, and nosocomial infection events of low-protein, hypocaloric nutrition with glutamine in the first 7 days of the intensive care unit (ICU) patients with severe traumatic brain injury (STBI). PATIENTS AND METHODS: A total of 53 patients diagnosed with STBI enrolled from the third affiliated hospital of Nanchang University (Nanchang, China), from January 2019 to July 2020, were divided into two groups. We performed a randomized prospective controlled trial. The intervention group (n=27) was nutritional supported (intestinal or parenteral) with a caloric capacity of 20-40% of European Conference on Clinical Nutrition and Metabolism (ESPEN) recommendations; specifically, low-protein intake was 0.5-0.7g/kg per day (containing the amount of alanyl-glutamine), glutamine was 0.3 g/kg per day, and the intervention treatment lasted for 7 days. The control group (n=26) was nutritionally supported with a caloric capacity of 70-100% of ESPEN recommendations, and the protein intake was 1.2-1.7 g/kg per day. The primary endpoint was 28-day mortality. Secondary endpoints were the length of ICU stay, days in the hospital, days of ventilator use, adverse events and nosocomial infection events. RESULTS: There were no differences in baseline characteristics between groups. Survival curve analysis using the Kaplan-Meier method revealed no significant difference in 28-day mortality between the two groups (P=0.31) while adverse events (χ 2= 5.853, P=0.016), nosocomial infection rate (χ 2 = 4.316, P=0.038), the length of ICU stay (t=-2.617, P=0.012), hospitalization time (t=-2.169, P=0.036), and days of ventilator use (t=-2.144,P=0.037) of patients in the intervention group were significantly lower than those in the control group. CONCLUSION: Low-protein, hypocaloric nutrition with glutamine did not show different outcomes in 28-day mortality compared to full-feeding nutritional support in the ICU patients with STBI. However, low-protein, hypocaloric nutrition with glutamine could provide a lower need for ICU time, hospitalization time, and ventilator time in the ICU patients with STBI.

[A report of first fatal case of H10N8 avian influenza virus pneumonia in the world].

OBJECTIVE: To report the treatment process of the first case of human pneumonia resulted from H10N8 avian influenza virus infection in the world for providing the data for clinical diagnosis and treatment. METHODS: On November 30, 2013, the first case of human infection with H10N8 avian influenza virus was discovered in Nanchang City, Jiangxi Province. Its clinical symptoms and epidemiology were analyzed and compared with the characteristics of human infection with H7N9 avian influenza virus. RESULTS: A 73-year old female patient complaining of cough and chest tightness for 3 days and fever for 1 day was admitted to the Department of Respiratory Diseases of the Third Affiliated Hospital of Nanchang University on November 30, 2013. As the illness became worse, the patient was transferred into Intensive Care Unit (ICU) of the Department of Critical Care Medicine on December 2. The patient's condition deteriorated, manifesting multiple organ failure (MOF) on December 5. At 08:30 on December 6, cardiac arrest occurred, and the patient died after inefficient resuscitation. (1) Epidemiological investigation: the patient was an elderly woman, suffering from a variety of chronic diseases (hypertension, coronary heart disease, myasthenia gravis, etc) and impaired immune function (undergone thymectomy), all of them were predisposing factors for deterioration of her health. She had visited the live poultry market one week before admission, and developed symptoms of influenza. The transmission route was the respiratory tract, which was similar to H7N9 avian influenza. (2) CLINICAL MANIFESTATIONS: the patient had flu-like symptoms, such as cough and fever (39.1 centigrade), but no headache or myalgia. Two days later pneumonia accompanied with respiratory distress developed and a large amount of bloody sputum was sucked out through tracheostomy tube (2 000 mL/24 h). Acute kidney injury, acute respiratory distress syndrome (ARDS), septic shock, and unconsciousness occurred, all of which was consistent with the diagnosis of H7N9 avian influenza. (3) Auxiliary examination: with the exception of a decrease in lymphocyte ratio (0.070), aspartate aminotransferase (AST) was slightly increased (57 U/L), C- reactive protein (CRP) was elevated (>200 mg/L), but the platelet count, creatine kinase, lactate dehydrogenase, alanine aminotransferase and myoglobin were not increased, while leucocyte count was increased slightly (10.34×10(9)/L). The changes in above indexes did not match the characteristics of H7N9 avian influenza. However, the aggravated consolidation of the lung conformed to that of H7N9 avian influenza. (4) DIAGNOSIS AND TREATMENT: according to the clinical manifestations, aggravation of consolidation of the lung, and epidemiological evidence, the diagnosis of avian influenza was considered. Though therapeutic dose of oseltamivir was given as antiviral treatment for the early therapy, and other therapeutic measures such as energetic respiratory and circulatory support, and immunosuppressant therapy were given, the patient eventually died from respiratory failure and shock. (5) The Chinese disease prevention and control center (CDC) confirmed that, the patient was infected H10N8 avian influenza virus. No person with close contact with the patient was infected, as screened by Nanchang City and Chinese CDC. CONCLUSIONS: Human infection with H10N8 avian influenza was not exactly the same as that of H7N9. It was difficult to get true information from the conventional laboratory examinations, while the clinical characteristic and epidemiology were essential for the diagnosis. Referring to the treatment regime for human infection with H7N9 avian influenza virus, therapeutic dose of neuraminidase inhibitors could not reverse deterioration of pulmonary pathology. Chinese CDC found that the risk of human infection and transmission of H10N8 avian influenza virus through personal contact was low.