Neuraminidase is a host-directed approach to regulate neutrophil responses in sepsis and COVID-19.

BACKGROUND AND PURPOSE: Neutrophil overstimulation plays a crucial role in tissue damage during severe infections. Because pathogen-derived neuraminidase (NEU) stimulates neutrophils, we investigated whether host NEU can be targeted to regulate the neutrophil dysregulation observed in severe infections. EXPERIMENTAL APPROACH: The effects of NEU inhibitors on lipopolysaccharide (LPS)-stimulated neutrophils from healthy donors or COVID-19 patients were determined by evaluating the shedding of surface sialic acids, cell activation, and reactive oxygen species (ROS) production. Re-analysis of single-cell RNA sequencing of respiratory tract samples from COVID-19 patients also was carried out. The effects of oseltamivir on sepsis and betacoronavirus-induced acute lung injury were evaluated in murine models. KEY RESULTS: Oseltamivir and zanamivir constrained host NEU activity, surface sialic acid release, cell activation, and ROS production by LPS-activated human neutrophils. Mechanistically, LPS increased the interaction of NEU1 with matrix metalloproteinase 9 (MMP-9). Inhibition of MMP-9 prevented LPS-induced NEU activity and neutrophil response. In vivo, treatment with oseltamivir fine-tuned neutrophil migration and improved infection control as well as host survival in peritonitis and pneumonia sepsis. NEU1 also is highly expressed in neutrophils from COVID-19 patients, and treatment of whole-blood samples from these patients with either oseltamivir or zanamivir reduced neutrophil overactivation. Oseltamivir treatment of intranasally infected mice with the mouse hepatitis coronavirus 3 (MHV-3) decreased lung neutrophil infiltration, viral load, and tissue damage. CONCLUSION AND IMPLICATIONS: These findings suggest that interplay of NEU1-MMP-9 induces neutrophil overactivation. In vivo, NEU may serve as a host-directed target to dampen neutrophil dysfunction during severe infections.

Neuraminidase inhibitors rewire neutrophil function in vivo in murine sepsis and ex vivo in COVID-19.

Neutrophil overstimulation plays a crucial role in tissue damage during severe infections. Neuraminidase (NEU)-mediated cleavage of surface sialic acid has been demonstrated to regulate leukocyte responses. Here, we report that antiviral NEU inhibitors constrain host NEU activity, surface sialic acid release, ROS production, and NETs released by microbial-activated human neutrophils. In vivo, treatment with Oseltamivir results in infection control and host survival in peritonitis and pneumonia models of sepsis. Single-cell RNA sequencing re-analysis of publicly data sets of respiratory tract samples from critical COVID-19 patients revealed an overexpression of NEU1 in infiltrated neutrophils. Moreover, Oseltamivir or Zanamivir treatment of whole blood cells from severe COVID-19 patients reduces host NEU-mediated shedding of cell surface sialic acid and neutrophil overactivation. These findings suggest that neuraminidase inhibitors can serve as host-directed interventions to dampen neutrophil dysfunction in severe infections.

Methionine supplementation for multi-organ dysfunction in MetRS-related pulmonary alveolar proteinosis.

INTRODUCTION: Pulmonary alveolar proteinosis related to mutations in the methionine tRNA synthetase (MARS1) gene is a severe, early-onset disease that results in death before the age of 2 years in one-third of patients. It is associated with a liver disease, growth failure and systemic inflammation. As methionine supplementation in yeast models restored normal enzymatic activity of the synthetase, we studied the tolerance, safety and efficacy of daily oral methionine supplementation in patients with severe and early disease. METHODS: Four patients received methionine supplementation and were followed for respiratory, hepatic, growth and inflammation-related outcomes. Their course was compared to those of historical controls. Reactive oxygen species production by patient monocytes before and after methionine supplementation was also studied. RESULTS: Methionine supplementation was associated with respiratory improvement, clearance of the extracellular lipoproteinaceous material and discontinuation of whole-lung lavage in all patients. The three patients who required oxygen or noninvasive ventilation could be weaned off within 60 days. In addition, liver dysfunction, inflammation and growth delay improved or resolved. At a cellular level, methionine supplementation normalised the production of reactive oxygen species by peripheral monocytes. CONCLUSION: Methionine supplementation was associated with important improvements in children with pulmonary alveolar proteinosis related to mutations in the MARS1 gene. This study paves the way for similar strategies for other tRNA synthetase deficiencies.

Lower-back pain and weight loss in a 75-year-old man / Douleurs lombaires et perte de poids chez un homme de 75 ans

A 75-year-old men is adressed in rheumatology for lower back pain, asthenia, and recent weight loss. Myeloma is suspected. Anemia, hyperproteinemia as well as a monoclonal IgG kappa with serum protein immunofixation are discovered. The diagnosis is confirmed by the myelogram with 14% of medullar plasmocytes. Osteolytic lesions are also found on the scanner.

Un homme de 75 ans a consulté en rhumatologie pour des douleurs lombaires, une asthénie et une perte de poids d'apparition récente. Un myélome est suspecté. Une anémie, une hyperprotidémie ainsi qu'une IgG kappa monoclonale à l'immunofixation des protéines sériques sont retrouvés. Le diagnostic est confirmé par le myélogramme qui décompte 14 % de plasmocytes. Des lésions ostéolytiques sont également mises en évidence au scanner.