Surfactant Protein B Reduces Respiratory Viral Infectivity in Human Lungs

Purpose of Study: COVID pneumonia caused by SARS-CoV-2 can result in a depletion of surfactant & lung injury, which resembles neonatal respiratory distress syndrome. Exogenous surfactant has shown promise as a therapeutic option in intubated hospitalized patients. Our preliminary data in human lung organoids (LOs) with a deficiency of surfactant protein B (SP-B) showed an increased viral load compared to normal LOs. Single cell RNA sequencing (scRNAseq) revealed that SP-B-deficient cells showed increased viral entry genes (ACE2 receptor) & dysregulated inflammatory markers emanating from the lung cells themselves. Our objective was to determine: (1) cell-specific transcriptional differences between normal & SP-B deficient human lung cells after infection with SARS-CoV-2 and (2) a therapeutic role of SP-B protein & surfactant in COVID-19 pneumonia. Methods Used: We used normal and SP-B mutant (homozygous, frameshift, loss of function mutation p.Pro133GlnfsTer95, previously known as 121ins2) human induced pluripotent stem cells (hiPSC) and differentiated them into 3D proximal lung organoids. The organoids were infected with the delta variant of SARS-CoV-2 for 24 hours at an MOI of 1. Infected and uninfected organoids were fixed in trizol in triplicate and underwent processing for bulk RNA sequencing. We tested for differentially expressed genes using the program DEseq. We also plated normal iPSC derived lung organoids as a monolayer and pre-treated them with 1mg/ml of Poractant alfa or 5 uM of recombinant SP-B protein. The delta strain of SARS-CoV-2 was added to the 96 wells at an MOI of 0.1 for one hour with shaking, then an overlay with DMEM/CMC/FBS was added and left on for 23 hours. The plate was fixed and stained for nucleocapsid (NC) protein. Summary of Results: Bioinformatic analysis of the bulk RNA sequencing data showed an increase in the multiple cytokines and chemokines in the SP-B mutant LOs compared to control. We also saw differential gene expression patterns in the SP-B mutant LOs including a reduction in SFTPC, FOXA2, and NKX2-1 and an increase in IL1A, VEGFA, PPARG and SMAD3. In the exogenous surfactant experiments, there was a decrease in total expression of viral NC in the Poractant alfa & rSP-B-treated cells compared to SARS-CoV-2 infection alone (p<0.001). Conclusion(s): Surfactant modulates the viral load of SARS-CoV-2 infection in the human lung. Deficiency in SP-B results in the dysregulation of the lung epithelial inflammatory signaling pathways resulting in worsening infections.

Molecular genetic markers associated with course of severe COVID-19 pneumonia. Different pathways study

Introduction: It is known that the development of COVID-19 in the human body consists of complex system of biological mechanisms underlying the complex interplay between infectious agents and the human host. This raised the question about hosts' genetic variants as predictors of clinical phenotype. The aim of our study was to analyze the effect of the NOS3 gene (VNTR intron 4 a/b), NR3C1 gene (C647G, rs41423247) and the SFTPB gene (C1580T, rs11130866) variants on the course of severe COVID-19 pneumonia in patients. Material(s) and Method(s): The study group included 20 patients (13 men and 7 women) with diagnosis "viral COVID19 pneumonia" treated at the intensive care unit. Investigation of the NOS3, NR3C1 and SFTPB genes variants was carried out by a molecular method using PCR-RFLP and allele-specific PCR, respectively. Result(s): The correlation analysis showed a significant association of the NOS3 gene variants and level of SpO2 (rS=-0.488, p=0.029;SpO2=93.1+/-2.4% for b/b and SpO2=82.0+/-1.1% for a/a genotypes). Also a significant positive correlation was between NR3C1 gene variants and duration of nasal intermittent positive pressure ventilation (nIPP) therapy (rS=0.454, p=0.044;for 647CC - 1.5+/-1.0 days and for 674GG - 3.9+/-2.5 days), presence of fever (need for antipyretics) (rS=0.525, p=0.017;647C vs 647G alleles - chi2=5.8, p=0.016). No significant correlations were found for the variants of SFTPB gene. The obtained results support a hypothesis about the combined influence of different pathways genes variants (NOS3 and NR3C1) on severity of COVID-19. However, in order to draw definite conclusions, further multifaceted research in this area are need.

Generation Of Macro-scale And Mature Lung Organoids Through Engineering Cell Microenvironment

Purpose/Objectives: <Most used lower respiratory tract models consist of cell monolayers which lack of tissue and organ level response and of in-vivo phenotype. Ex-vivo lung tissues have short viability and limited availability. Lung organoids, which recapitulates better the 3D cellular complex structures, architecture, and in-vivo function, fail to reach maturity even after 85 -185 days of culture. Therefore, these models have a limited use to study fetal lung diseases. Other lung models, consist of only one structure of the lower track, such as bronchial tubes or alveoli, but fail to recapitulate the whole organ structure. In this work, cell microenvironment was used to promote the self-organization of epithelial and mesenchymal cells into macro-structures, aiming to mimic the whole and adult lower respiratory tract model> Methodology: <Different parts of the microenvironment were considered to create a compliant matrix. Alginate-Gelatin hydrogels were used for 3D encapsulation of mesenchymal origin cells. This hydrogel provided a stiffness like the one on the lung. Base membrane zone proteins were used to induce the attachment and guidance of epithelial cells into 3D structures. The interactions between both cell types, further guided them into lung fate. The morphology of resulting organoids was analyzed using immunostaining and confocal microscopy, LSM710, with the purpose of evaluate polarization, protein markers, and different cell populations. Quantitative PCR was performed to evaluate and compare the expression of lung fate genes with traditional cell monocultures.> Results: <The engineered microenvironment and protocol development done in this work resulted in macro-scale structures, in which branching morphogenesis occurred at day 21. Different structures were identified in the organoid including bronchial tube, bronchioles, and alveoli. Polarization of the organoids was confirmed by visualization of E-cadherin, and ZO-1. Expression of Surfactant Protein B and C into the organoids confirmed the presence of alveolar type II cells, which are only present in the later development stage. Surfactant Protein B, Transmembrane protease, serine 2, TMPRSS-2, and Angiotensin-converting enzyme 2, ACE2 were found to be significantly higher expressed into the organoids in comparison with traditional epithelial cells monolayers.> Conclusion/Significance: <Growth factors are normally used to induce the fate of stem cells into lung organoids;however, these fail to reach maturity. Here, we developed a new methodology to induce the formation of the organoids based on the cell microenvironment. The resulting organoids require less time for development. The initial stage of adult cells can be modulated through culture conditions induce a 3D structure like the adult lung. As such, these organoids have the potential to be used for modeling adult diseases and to develop specific models from patient cells, which is one step forward to personalized medicine. SFTPB is one of the main proteins which facilitates the breathing process. Its high expression into our model may indicate that breathing occurs into our lung organoids. The higher expression of TMPRSS-2 and ACE2 into the organoids has a major significance in the field of virology since both proteins are the mainly entrance of SARS-CoV-2, and influenza H1N1.>.

Elucidating the enhanced binding affinity of a double mutant SP-D with trimannose on the influenza A virus using molecular dynamics.

Surfactant protein D (SP-D) is an essential component of the human pulmonary surfactant system, which is crucial in the innate immune response against glycan-containing pathogens, including Influenza A viruses (IAV) and SARS-CoV-2. Previous studies have shown that wild-type (WT) SP-D can bind IAV but exhibits poor antiviral activities. However, a double mutant (DM) SP-D consisting of two point mutations (Asp325Ala and Arg343Val) inhibits IAV more potently. Presently, the structural mechanisms behind the point mutations' effects on SP-D's binding affinity with viral surface glycans are not fully understood. Here we use microsecond-scale, full-atomistic molecular dynamics (MD) simulations to understand the molecular mechanism of mutation-induced SP-D's higher antiviral activity. We find that the Asp325Ala mutation promotes a trimannose conformational change to a more stable state. Arg343Val increases the binding with trimannose by increasing the hydrogen bonding interaction with Glu333. Free energy perturbation (FEP) binding free energy calculations indicate that the Arg343Val mutation contributes more to the increase of SP-D's binding affinity with trimannose than Asp325Ala. This study provides a molecular-level exploration of how the two mutations increase SP-D binding affinity with trimannose, which is vital for further developing preventative strategies for related diseases.

Plasma and Airway Levels of Surfactant Protein D Degradation Reflect Progression of ARDS in Ventilated Patients with SARS-CoV-2

Background: Patients with COVID-19 present severe respiratory symptoms progressing to acute respiratory distress syndrome (ARDS). Upon infection, SARS-CoV-2 destroys cells expressing the ACE2 receptor including alveolar type II cells (AT2). These cells are found in the alveolar-capillary barrier which normally secrete pulmonary surfactant, a complex of lipid and surfactant proteins (SPA, SP-B, SP-C, SP-D). Exogenous surfactant therapy (mainly composed of phospholipids, SP-B, and SP-C) has been successful in treating neonatal respiratory distress syndrome (nRDS) caused by surfactant deficiency in preterm babies.Plasma SP-D has been proposed as a marker of lung injury in COVID-19 but so far, no reports have evaluated sequential SP-D levels in both airway and plasma. As part of a clinical trial repurposing surfactant therapy to treat adult ventilated COVID-19 patients, we hypothesized that plasma SP-D levels may reflect decreased lung integrity and that SP-D degradation in plasma and airway samples from COVID-19 patients may reflect disease progression and severity. Methods: Enzyme-linked immunosorbent assay (ELISA) was used to quantify SP-D concentration in patient plasma and tracheal aspirate samples. Western Blotting was used to identify any protein degradation. Sequential daily plasma and airway samples were analysed. Results: SP-D concentration in serum was 10-20 times higher in patients ventilated for COVID-19 than in healthy volunteers. Additionally, the concentration of SP-D in plasma has shown to be 10-100-fold higher than in tracheal aspirates. Furthermore, degraded fragments of SP-D were detected at a higher ratio than intact SP-D in plasma of ventilated patients. This ratio decreased with administration of surfactant therapy (containing phospholipids and SP-B and SP-C but no SPA or SP-D). Conclusions: Increased serum SP-D and decreased tracheal aspirate SP-D from ventilated COVID-19 patients suggested leakage of pulmonary surfactant into the bloodstream caused by damage to the alveolar-capillary barrier in diseased lungs. The ratio of degraded vs. intact SP-D found in the plasma was compared before and after therapeutic surfactant administration. The results indicated that levels of SP-D in plasma and tracheal aspirates together with the ratio of degraded and intact SP-D in the plasma may be useful indicators of the severity of COVID-19 lung disease progression.