ABSTRACT
The development of safe and effective vaccines in a record time after the emergence of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a remarkable achievement, partly based on the experience gained from multiple viral outbreaks in the past decades. However, the Coronavirus Disease 2019 (COVID-19) crisis also revealed weaknesses in the global pandemic response and large gaps that remain in our knowledge of the biology of coronaviruses (CoVs) and influenza viruses, the 2 major respiratory viruses with pandemic potential. Here, we review current knowns and unknowns of influenza viruses and CoVs, and we highlight common research challenges they pose in 3 areas: the mechanisms of viral emergence and adaptation to humans, the physiological and molecular determinants of disease severity, and the development of control strategies. We outline multidisciplinary approaches and technological innovations that need to be harnessed in order to improve preparedeness to the next pandemic.
Subject(s)
COVID-19/virology , Influenza, Human/virology , Orthomyxoviridae/physiology , SARS-CoV-2/physiology , Animals , Antiviral Agents , COVID-19/therapy , COVID-19/transmission , Drug Development , Evolution, Molecular , Humans , Influenza, Human/therapy , Influenza, Human/transmission , Orthomyxoviridae/immunology , SARS-CoV-2/immunology , Selection, Genetic , Viral Load , Viral VaccinesABSTRACT
PURPOSE: Severe pneumonia and acute respiratory distress syndrome (ARDS) have been described in patients with severe coronavirus disease 2019 (COVID-19). Recently, early clinical data reported the feasibility of low doses of radiation therapy (RT) in the treatment of ARDS in patients with severe COVID-19. However, the involved mechanisms remained unknown. METHODS AND MATERIALS: Here, we used airways-instilled lipopolysaccharide (LPS) and influenza virus (H1N1) as murine models of pneumonia, and toll-like receptor (TLR)-3 stimulation in human lung macrophages. RESULTS: Low doses of RT (0.5-1 Gray) decreased LPS-induced pneumonia, and increased the percentage of nerve- and airway-associated macrophages producing interleukin (IL) 10. During H1N1 viral infection, we observed decreased lung tissue damage and immune cell infiltration in irradiated animals. Low doses of RT increased IL-10 production by infiltrating immune cells into the lung. Irradiation of TLR-3 ligand-stimulated human lung macrophages ex vivo increased IL-10 secretion and decreased interferon γ production in the culture supernatant. The percentage of human lung macrophages producing IL-6 was also decreased. CONCLUSIONS: Our data highlight a mechanism by which low doses of RT regulate lung inflammation and skew lung macrophages toward an anti-inflammatory profile. These data provide a preclinical mechanistic support to clinical trials evaluating low doses of RT, such as COVID-19-induced ARDS.
Subject(s)
Epithelial Cells/radiation effects , Influenza A Virus, H1N1 Subtype , Interleukin-10/biosynthesis , Macrophages/radiation effects , Pneumonia, Viral/radiotherapy , Respiratory Distress Syndrome/radiotherapy , Animals , Anti-Inflammatory Agents/pharmacology , COVID-19/complications , Dexamethasone/pharmacology , Disease Models, Animal , Epithelial Cells/drug effects , Epithelial Cells/immunology , Epithelial Cells/metabolism , Female , Flow Cytometry , Humans , Influenza A Virus, H1N1 Subtype/radiation effects , Interferon-gamma/biosynthesis , Interleukin-6/biosynthesis , Lipopolysaccharides , Lung/cytology , Lung/pathology , Lung/radiation effects , Macrophages/drug effects , Macrophages/immunology , Macrophages/metabolism , Mice , Mice, Inbred C57BL , Pneumonia, Viral/etiology , Pneumonia, Viral/prevention & control , Poly I-C , Radiotherapy Dosage , Respiratory Distress Syndrome/etiology , Toll-Like Receptor 3 , Viral Load/radiation effectsABSTRACT
Anosmia is one of the most prevalent symptoms of SARS-CoV-2 infection during the COVID-19 pandemic. However, the cellular mechanism behind the sudden loss of smell has not yet been investigated. The initial step of odour detection takes place in the pseudostratified olfactory epithelium (OE) mainly composed of olfactory sensory neurons surrounded by supporting cells known as sustentacular cells. The olfactory neurons project their axons to the olfactory bulb in the central nervous system offering a potential pathway for pathogens to enter the central nervous system by bypassing the blood brain barrier. In the present study, we explored the impact of SARS-CoV-2 infection on the olfactory system in golden Syrian hamsters. We observed massive damage of the OE as early as 2 days post nasal instillation of SARS-CoV-2, resulting in a major loss of cilia necessary for odour detection. These damages were associated with infection of a large proportion of sustentacular cells but not of olfactory neurons, and we did not detect any presence of the virus in the olfactory bulbs. We observed massive infiltration of immune cells in the OE and lamina propria of infected animals, which may contribute to the desquamation of the OE. The OE was partially restored 14 days post infection. Anosmia observed in COVID-19 patient is therefore likely to be linked to a massive and fast desquamation of the OE following sustentacular cells infection with SARS-CoV-2 and subsequent recruitment of immune cells in the OE and lamina propria.