The role of angiopoietin-2 and surfactant protein-D levels in SARS-CoV-2-related lung injury: A prospective, observational, cohort study

Unraveling the enigma: The emerging significance of pulmonary surfactant proteins in predicting, diagnosing, and managing COVID-19

BACKGROUND

Severe cases of COVID-19 often lead to the development of acute respiratory syndrome, a critical condition believed to be caused by the harmful effects of SARS-CoV-2 on type II alveolar cells. These cells play a crucial role in producing pulmonary surfactants, which are essential for proper lung function. Specifically focusing on surfactant proteins, including Surfactant protein A (SP-A), Surfactant protein B, Surfactant protein C, and Surfactant protein D (SP-D), changes in the levels of pulmonary surfactants may be a significant factor in the pathological changes seen in COVID-19 infection.

OBJECTIVE

This study aims to gain insights into surfactants, particularly their impacts and changes during COVID-19 infection, through a comprehensive review of current literature. The study focuses on the function of surfactants as prognostic markers, diagnostic factors, and essential components in the management and treatment of COVID-19.

FINDING

In general, pulmonary surfactants serve to reduce the surface tension at the gas-liquid interface, thereby significantly contributing to the regulation of respiratory mechanics. Additionally, these surfactants play a crucial role in the innate immune system within the pulmonary microenvironment. Within the spectrum of COVID-19 infections, a compelling association is observed, characterized by elevated levels of SP-D and SP-A across a range of manifestations from mild to severe pneumonia. The sudden decline in respiratory function observed in COVID-19 patients may be attributed to the decreased synthesis of surfactants by type II alveolar cells.

CONCLUSION

Collectin proteins such as SP-A and SP-D show promise as biomarkers, offering potential avenues for predicting and monitoring pulmonary alveolar injury in the context of COVID-19. This clarification enhances our understanding of the molecular complexities contributing to respiratory complications in severe COVID-19 cases, providing a foundation for targeted therapeutic approaches using surfactants and refined clinical management strategies.

Angiopoietins as Predictor Indexes in COVID-19 Patients in Delta and Omicron Waves

This study aimed to explore the correlation between Angiopoietin-1 (Ang-1) and Angiopoietin-2 (Ang-2) concentrations and the Angiopoietin-2/Angiopoietin-1 ratio (Ang-2/Ang-1) with clinical outcomes, potentially serving as disease severity and survival biomarkers. A study at AHEPA University Hospital involved 90 Coronavirus Disease 2019 (COVID-19) adult patients, 30 hospitalized intensive care units (ICU), 30 inward units (non-ICU), and 30 asymptomatic non-hospitalized individuals as controls. Estimated endothelial dysfunction markers related to angiogenesis were measured. There was a statistically significant difference only between outpatient and hospitalized patients (non-ICU-ICU groups) for the Ang-1 and Ang-2 indices. The Ang-2/Ang-1 ratio has differed significantly among the individual patient groups. An ROC analysis was conducted to find an optimal threshold for distinguishing between (outpatients-non-ICU) and (non-ICU-ICU) groups. It was based on Youden's index of 0.1122 and 0.3825, respectively. The Ang-1, Ang-2 levels, and Ang-2/Ang-1 ratio were analyzed as severity indicators in COVID-19 patients. The Ang-2/Ang-1 ratio demonstrated better prognostic and diagnostic utility than individual biomarker levels. Monitoring the Ang-2/Ang-1 ratio can identify COVID-19 patients at risk and assist clinicians in tailoring treatment strategies to improve outcomes.

Prognostic significance of the chemerin level in coronavirus disease 2019 patients

Increased serum chemerin levels have been reported in several inflammatory diseases. Few studies have investigated the relationship between chemerin and clinical features of COVID-19. Thus, chemerin may modulate the development and progression of COVID-19. We compared the serum chemerin concentration between patients with and without SARS-CoV-2 infection and its association with the severity and prognosis of COVID-19 pneumonia. This is a prospective, single-center, cross-sectional study. We enrolled COVID-19 patients who presented to our tertiary hospital and healthy controls. The COVID-19 patients were conducted and the dates of symptom onset were recorded. After admission to the hospital and stabilization, blood samples were obtained for routine hemogram, biochemistry, and chemerin. The chemerin level was 37.93 ± 17.3 ng/mL in patients followed in the ICU, 29.41 ± 12.79 ng/mL in inpatients, 30.48 ± 10.86 ng/mL in outpatients, and 25.12 ± 9.82 ng/mL in healthy controls. The difference between patients treated in the ICU and healthy controls was significant (P < .001). The high-sensitivity C-reactive protein (hs-CRP), ferritin, procalcitonin (PCT), and D-dimer levels were significantly higher in the intensive care unit (ICU) group (P < .001). Moreover, the chemerin level of patients who died was significantly higher than that of those who survived (P < .001). The chemerin level was increased in COVID-19 patients and also increased with increasing disease severity. The chemerin level was higher in the COVID-19 patients than healthy controls and was significantly higher in patients who died compared to those who did not.

EVALUATION OF CYFRA 21-1, ANGIOPOETIN-2, PENTRAXIN-3, SRAGE, IL-6, AND IL-10 IN POLYTRAUMATIZED PATIENTS WITH CONCOMITANT THORACIC TRAUMA-HELPFUL MARKERS TO PREDICT PNEUMONIA?

ABSTRACT

Background: Pneumonia is a frequent complication after polytrauma. This study aims to evaluate the ability of different serum markers to identify patients at risk of developing pneumonia after polytrauma. Methods: A retrospective analysis of prospectively collected data in polytraumatized patients with concomitant thoracic trauma (Injury Severity Score ≥16, Abbreviated Injury Scale Thorax ≥ 3) was performed. The study cohort was divided into patients with and without pneumonia during the clinical course. Serum levels of lung epithelial (CYFRA 21-1), endothelial (Ang-2), and inflammatory (PTX-3, sRAGE, IL-6, IL-10) markers were measured upon arrival in the trauma room and on days 2 and 5. Results: A total of 73 patients and 16 healthy controls were included in this study. Of these, 20 patients (27.4%) developed pneumonia. Polytraumatized patients showed significantly increased CYFRA 21-1 levels with a distinct peak after admission compared with healthy controls. Serum PTX-3 significantly increased on day 2 in polytraumatized patients compared with healthy controls. Injury Severity Score and demographic parameters were comparable between both groups (pneumonia vs. no pneumonia). No statistically significant difference could be observed for serum levels of CYFRA 21-1, Ang-2, PTX-3, sRAGE, IL-6, and IL-10 between the groups (pneumonia vs. no pneumonia) on all days. Logistic regression revealed a combination of IL-6, IL-10, sRAGE, and PTX-3 to be eventually helpful to identify patients at risk of developing pneumonia and our newly developed score was significantly higher on day 0 in patients developing pneumonia ( P < 0.05). Conclusion: The investigated serum markers alone are not helpful to identify polytraumatized patients at risk of developing pneumonia, while a combination of IL-6, IL-10, PTX-3, and sRAGE might be.

Endotheliopathy in Acute COVID-19 and Long COVID

The pulmonary endothelium is a highly regulated organ that performs a wide range of functions under physiological and pathological conditions. Since endothelial dysfunction has been demonstrated to play a direct role in sepsis and acute respiratory distress syndrome, its role in COVID-19 has also been extensively investigated. Indeed, apart from the COVID-19-associated coagulopathy biomarkers, new biomarkers were recognised early during the pandemic, including markers of endothelial cell activation or injury. We systematically searched the literature up to 10 March 2023 for studies examining the association between acute and long COVID-19 severity and outcomes and endothelial biomarkers.

Discovery and systematic assessment of early biomarkers that predict progression to severe COVID-19 disease

BACKGROUND

The clinical course of COVID-19 patients ranges from asymptomatic infection, via mild and moderate illness, to severe disease and even fatal outcome. Biomarkers which enable an early prediction of the severity of COVID-19 progression, would be enormously beneficial to guide patient care and early intervention prior to hospitalization.

METHODS

Here we describe the identification of plasma protein biomarkers using an antibody microarray-based approach in order to predict a severe cause of a COVID-19 disease already in an early phase of SARS-CoV-2 infection. To this end, plasma samples from two independent cohorts were analyzed by antibody microarrays targeting up to 998 different proteins.

RESULTS

In total, we identified 11 promising protein biomarker candidates to predict disease severity during an early phase of COVID-19 infection coherently in both analyzed cohorts. A set of four (S100A8/A9, TSP1, FINC, IFNL1), and two sets of three proteins (S100A8/A9, TSP1, ERBB2 and S100A8/A9, TSP1, IFNL1) were selected using machine learning as multimarker panels with sufficient accuracy for the implementation in a prognostic test.

CONCLUSIONS

Using these biomarkers, patients at high risk of developing a severe or critical disease may be selected for treatment with specialized therapeutic options such as neutralizing antibodies or antivirals. Early therapy through early stratification may not only have a positive impact on the outcome of individual COVID-19 patients but could additionally prevent hospitals from being overwhelmed in potential future pandemic situations.

Biomarkers of endothelial dysfunction are associated with poor outcome in COVID-19 patients: A systematic review and meta-analysis

Numerous studies have linked coronavirus disease 2019 (COVID-19) with endothelial dysfunction and reported elevated levels of endothelial biomarkers in this disease. We conducted a systematic review and meta-analysis of the published evidence in this respect. A systematic literature search of PubMed and Scopus databases was performed to find studies investigating biomarkers of endothelial dysfunction in COVID-19 patients. Pooled standardized mean differences and their 95% confidence intervals were calculated for each biomarker using random effect model. 74 studies with 7668 patients were included. In comparison to patients with good outcome, those with poor outcome had higher levels of von Willebrand factor (vWF) (SMD: 0.83, 95% CI: 0.59-1.07, p < 0.00001), vWF:ADAMTS13 (1.23, (0.77-1.7), p < 0.00001), angiopoietin-2 (Ang-2) (1.06 (0.6-1.51), p < 0.0001), E-selectin (1.09 (0.55-1.63), p < 0.0001), P-selectin (0.59 (0.24-0.94), p = 0.001), syndecan-1 (0.99 (0.6-1.37), p < 0.00001), mid-regional pro-adrenomedullin (MR-proADM) (1.52 (1.35-1.68), p < 0.00001), vascular endothelial growth factor (0.27 (0.02-0.53), p = 0.03), soluble fms-like tyrosine kinase-1 (sFLT-1) (1.93 (0.65-3.21), p = 0.03) and lower levels of ADAMTS13 antigen (-0.69 (-0.9 to -0.47) p < 0.00001) and activity (-0.84 (-1.06 to -0.61) p < 0.0000). Plasminogen activator inhibitor-1 and tissue plasminogen activator levels were not different between the two groups (p < 0.05). There were elevated levels of endothelial dysfunction biomarkers in COVID-19 patients with poor outcome, indicating their possible role in disease severity and prognosis. In particular, MR-proADM, vWF, syndecan-1 and sFLT-1 showed a significant association with poor outcome in these patients.

COVID-19 and Pulmonary Angiogenesis: The Possible Role of Hypoxia and Hyperinflammation in the Overexpression of Proteins Involved in Alveolar Vascular Dysfunction

COVID-19 has been considered a vascular disease, and inflammation, intravascular coagulation, and consequent thrombosis may be associated with endothelial dysfunction. These changes, in addition to hypoxia, may be responsible for pathological angiogenesis. This research investigated the impact of COVID-19 on vascular function by analyzing post-mortem lung samples from 24 COVID-19 patients, 10 H1N1pdm09 patients, and 11 controls. We evaluated, through the immunohistochemistry technique, the tissue immunoexpressions of biomarkers involved in endothelial dysfunction, microthrombosis, and angiogenesis (ICAM-1, ANGPT-2, and IL-6, IL-1β, vWF, PAI-1, CTNNB-1, GJA-1, VEGF, VEGFR-1, NF-kB, TNF-α and HIF-1α), along with the histopathological presence of microthrombosis, endothelial activation, and vascular layer hypertrophy. Clinical data from patients were also observed. The results showed that COVID-19 was associated with increased immunoexpression of biomarkers involved in endothelial dysfunction, microthrombosis, and angiogenesis compared to the H1N1 and CONTROL groups. Microthrombosis and vascular layer hypertrophy were found to be more prevalent in COVID-19 patients. This study concluded that immunothrombosis and angiogenesis might play a key role in COVID-19 progression and outcome, particularly in patients who die from the disease.

Multi-omics of NET formation and correlations with CNDP1, PSPB, and L-cystine levels in severe and mild COVID-19 infections

The detailed mechanisms of COVID-19 infection pathology remain poorly understood. To improve our understanding of SARS-CoV-2 pathology, we performed a multi-omics and correlative analysis of an immunologically naïve SARS-CoV-2 clinical cohort from blood plasma of uninfected controls, mild, and severe infections. Consistent with previous observations, severe patient populations showed an elevation of pulmonary surfactant levels. Intriguingly, mild patients showed a statistically significant elevation in the carnosine dipeptidase modifying enzyme (CNDP1). Mild and severe patient populations showed a strong elevation in the metabolite L-cystine (oxidized form of the amino acid cysteine) and enzymes with roles in glutathione metabolism. Neutrophil extracellular traps (NETs) were observed in both mild and severe populations, and NET formation was higher in severe vs. mild samples. Our correlative analysis suggests a potential protective role for CNDP1 in suppressing PSPB release from the pulmonary space whereas NET formation correlates with increased PSPB levels and disease severity. In our discussion we put forward a possible model where NET formation drives pulmonary occlusions and CNDP1 promotes antioxidation, pleiotropic immune responses, and vasodilation by accelerating histamine synthesis.

Treatment of Acute Respiratory Distress Syndrome Caused by COVID-19 with Human Umbilical Cord Mesenchymal Stem Cells

This study aimed to identify the impact of mesenchymal stem cell transplantation on the safety and clinical outcomes of patients with severe COVID-19. This research focused on how lung functional status, miRNA, and cytokine levels changed following mesenchymal stem cell transplantation in patients with severe COVID-19 pneumonia and their correlation with fibrotic changes in the lung. This study involved 15 patients following conventional anti-viral treatment (Control group) and 13 patients after three consecutive doses of combined treatment with MSC transplantation (MCS group). ELISA was used to measure cytokine levels, real-time qPCR for miRNA expression, and lung computed tomography (CT) imaging to grade fibrosis. Data were collected on the day of patient admission (day 0) and on the 7th, 14th, and 28th days of follow-up. A lung CT assay was performed on weeks 2, 8, 24, and 48 after the beginning of hospitalization. The relationship between levels of biomarkers in peripheral blood and lung function parameters was investigated using correlation analysis. We confirmed that triple MSC transplantation in individuals with severe COVID-19 was safe and did not cause severe adverse reactions. The total score of lung CT between patients from the Control and MSC groups did not differ significantly on weeks 2, 8, and 24 after the beginning of hospitalization. However, on week 48, the CT total score was 12 times lower in patients in the MSC group (p ≤ 0.05) compared to the Control group. In the MSC group, this parameter gradually decreased from week 2 to week 48 of observation, whereas in the Control group, a significant drop was observed up to week 24 and remained unchanged afterward. In our study, MSC therapy improved lymphocyte recovery. The percentage of banded neutrophils in the MSC group was significantly lower in comparison with control patients on day 14. Inflammatory markers such as ESR and CRP decreased more rapidly in the MSC group in comparison to the Control group. The plasma levels of surfactant D, a marker of alveocyte type II damage, decreased after MSC transplantation for four weeks in contrast to patients in the Control group, in whom slight elevations were observed. We first showed that MSC transplantation in severe COVID-19 patients led to the elevation of the plasma levels of IP-10, MIP-1α, G-CSF, and IL-10. However, the plasma levels of inflammatory markers such as IL-6, MCP-1, and RAGE did not differ between groups. MSC transplantation had no impact on the relative expression levels of miR-146a, miR-27a, miR-126, miR-221, miR-21, miR-133, miR-92a-3p, miR-124, and miR-424. In vitro, UC-MSC exhibited an immunomodulatory impact on PBMC, increasing neutrophil activation, phagocytosis, and leukocyte movement, activating early T cell markers, and decreasing effector and senescent effector T cell maturation.

Surfactant protein D (SP-D) as a biomarker of SARS-CoV-2 infection

Background

Surfactant protein-D (SP-D) is a lung-resident protein that has emerged as a potential biomarker for COVID-19. Previous investigations on acute respiratory distress syndrome patients demonstrated a significant increment of SP-D serum levels in pathological conditions. Since SP-D is not physiologically permeable to alveoli-capillary membrane and poorly expressed by other tissues, this enhancement is likely due to an impairment of the pulmonary barrier caused by prolonged inflammation.

Methods

A retrospective study on a relatively large cohort of patients of Hospital Pio XI of Desio was conducted to assess differences of the hematic SP-D concentrations among COVID-19 patients and healthy donors and if SP-D levels resulted a risk factor for disease severity and mortality.

Results

The first analysis, using an ANOVA-model, showed a significant difference in the mean of log SP-D levels between COVID-19 patients and healthy donors. Significant variations were also found between dead vs survived patients. Results confirm that SP-D concentrations were significantly higher for both hospitalized COVID-19 and dead patients, with threshold values of 150 and 250 ng/mL, respectively. Further analysis conducted with Logistic Mixed models, highlighted that higher SP-D levels at admission and increasing differences among follow-up and admission values resulted the strongest significant risk factors of mortality (model predictive accuracy, AUC = 0.844).

Conclusions

The results indicate that SP-D can be a predictive marker of COVID-19 disease and its outcome. Considering its prognostic value in terms of mortality, the early detection of SP-D levels and its follow-up in hospitalized patients should be considered to direct the therapeutic intervention.

All Microbiological Aspects of SARS-CoV-2 Virus

The COVID-19 disease, caused by SARS-CoV-2 virus, which was first seen in Wuhan (China) on December 31, 2019, rapidly spread to cities, countries, and continents and was noted in history as the first pandemic caused by coronaviruses. According to the World Health Organization reports, more than 645 million confirmed SARS-CoV-2-positive cases and more than 6.5 million confirmed deaths were noted all over the world during the pandemic (between December 2020 and December 2022). Although SARS-CoV-2 is a virus belonging to the coronavirus family, our knowledge of the pathogenesis and immune response of SARS-CoV-2 is still limited. Approximately 10 years (2012) after the Middle East Respiratory Syndrome (MERS-CoV) (nearly 2200 confirmed cases and 791 confirmed deaths) and 20 years (2002-2004) after the SARS-CoV epidemic (29 different countries, nearly 8000 confirmed cases, and 774 confirmed deaths), the current COVID-19 pandemic is a reminder of how new pathogens can emerge and spread rapidly, eventually causing serious public health problems. Further research is needed to establish animal models for SARSCoV-2 to investigate replication, transmission dynamics, and pathogenesis in humans in order to develop effective antiviral treatments and vaccines.

SP-A binding to the SARS-CoV-2 spike protein using hybrid quantum and classical in silico modeling and molecular pruning by Quantum Approximate Optimization Algorithm (QAOA) Based MaxCut with ZDOCK

The pulmonary surfactant protein A (SP-A) is a constitutively expressed immune-protective collagenous lectin (collectin) in the lung. It binds to the cell membrane of immune cells and opsonizes infectious agents such as bacteria, fungi, and viruses through glycoprotein binding. SARS-CoV-2 enters airway epithelial cells by ligating the Angiotensin Converting Enzyme 2 (ACE2) receptor on the cell surface using its Spike glycoprotein (S protein). We hypothesized that SP-A binds to the SARS-CoV-2 S protein and this binding interferes with ACE2 ligation. To study this hypothesis, we used a hybrid quantum and classical in silico modeling technique that utilized protein graph pruning. This graph pruning technique determines the best binding sites between amino acid chains by utilizing the Quantum Approximate Optimization Algorithm (QAOA)-based MaxCut (QAOA-MaxCut) program on a Near Intermediate Scale Quantum (NISQ) device. In this, the angles between every neighboring three atoms were Fourier-transformed into microwave frequencies and sent to a quantum chip that identified the chemically irrelevant atoms to eliminate based on their chemical topology. We confirmed that the remaining residues contained all the potential binding sites in the molecules by the Universal Protein Resource (UniProt) database. QAOA-MaxCut was compared with GROMACS with T-REMD using AMBER, OPLS, and CHARMM force fields to determine the differences in preparing a protein structure docking, as well as with Goemans-Williamson, the best classical algorithm for MaxCut. The relative binding affinity of potential interactions between the pruned protein chain residues of SP-A and SARS-CoV-2 S proteins was assessed by the ZDOCK program. Our data indicate that SP-A could ligate the S protein with a similar affinity to the ACE2-Spike binding. Interestingly, however, the results suggest that the most tightly-bound SP-A binding site is localized to the S2 chain, in the fusion region of the SARS-CoV-2 S protein, that is responsible for cell entry Based on these findings we speculate that SP-A may not directly compete with ACE2 for the binding site on the S protein, but interferes with viral entry to the cell by hindering necessary conformational changes or the fusion process.

Serum stratifin and presepsin as candidate biomarkers for early detection of COVID-19 disease progression

The prognosis of patients with severe cases of COVID-19 is poor; thus, biomarkers for earlier prediction of COVID-19 progression are vital. We measured levels of five lung injury-related biomarkers, SP-D, KL-6, presepsin, kallistatin and stratifin, in serum samples collected serially during hospitalization from 31 patients with mild/moderate or severe/critical COVID-19 pneumonia, and their predictive performances were compared. Like the previously reported presepsin, a new biomarker candidate, stratifin, was significantly elevated with the onset of severe or critical symptoms in COVID-19 patients and decreased with symptom improvement. Notably, changes in stratifin and presepsin levels were distinctly earlier than those in SP-D, KL-6 and even SpO₂/FiO₂ values. Furthermore, serum levels of these biomarkers were significantly higher at the pre-severe stage (before the start of oxygen support) of patients who eventually advanced to severe/critical stages than in the patients who remained at the mild/moderate stage. These results were confirmed in an independent cohort, including 71 mild/moderate and 14 severe/critical patients, for whom the performance of stratifin and presepsin in discriminating between mild/moderate and pre-severe conditions of COVID-19 patients was superior to that of the SpO₂/FiO₂ ratio. Therefore, we concluded that stratifin and presepsin could be used as prognostic biomarkers for severe COVID-19 progression.

Clinical Utility of Circulating Pneumoproteins as Diagnostic and Prognostic Biomarkers in COVID-19: A Systematic Review and Meta-analysis

INTRODUCTION

This study explored circulating pneumoproteins in the diagnosis, severity, and prognosis of COVID-19 by meta-analysis.

METHODS

We searched five databases and other sources until December 16, 2021. Standardized mean difference (SMD) and 95% confidence interval (CI) were the overall outcomes. RevMan 5.3, Stata 16, and Meta-DiSc 1.4 were utilized for pooled analysis.

RESULTS

A total of 2432 subjects from 26 studies were included. Patients with COVID-19 had higher circulating KL-6, SP-D, and SP-A levels (SMD 1.34, 95% CI [0.60, 2.08]; SMD 1.74, 95% CI [0.64, 2.84]; SMD 3.42, 95% CI [1.31, 5.53], respectively) than healthy individuals. Circulating SP-D levels were not significantly different in survivors and non-survivors (SMD - 0.19, 95% CI [- 0.78, 0.40]). Circulating KL-6, SP-D, and RAGE levels in patients with mild to moderate COVID-19 were significantly lower (SMD - 0.93, 95% CI [- 1.22, - 0.65]; SMD - 1.32, 95% CI [- 2.34, - 0.29]; SMD - 1.17, 95% CI [- 2.06, - 0.28], respectively) than in patients with severe COVID-19. Subgroup analysis suggested that country and total number may be related to the heterogeneity when analyzing SP-D in patients with mild to moderate vs. severe COVID-19. The meta-analysis of diagnostic accuracy including KL-6 for severity, KL-6 for mortality, and SP-D for severity demonstrated that they all had limited diagnostic value.

CONCLUSION

Therefore, circulating pneumoproteins (KL-6, SP-D, and RAGEs) reflect the diagnosis, severity, and prognosis of COVID-19, and follow-up studies are still needed.

Role of Neuropilin 1 in COVID-19 Patients with Acute Ischemic Stroke

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infection can trigger the adaptive and innate immune responses, leading to uncontrolled inflammatory reactions and associated local and systematic tissue damage, along with thromboembolic disorders that may increase the risk of acute ischemic stroke (AIS) in COVID-19 patients. The neuropilin (NRP-1) which is a co-receptor for the vascular endothelial growth factor (VEGF), integrins, and plexins, is involved in the pathogenesis of AIS. NRP-1 is also regarded as a co-receptor for the entry of SARS-CoV-2 and facilitates its entry into the brain through the olfactory epithelium. NRP-1 is regarded as a cofactor for binding of SARS-CoV-2 with angiotensin-converting enzyme 2 (ACE2), since the absence of ACE2 reduces SARS-CoV-2 infectivity even in presence of NRP-1. Therefore, the aim of the present study was to clarify the potential role of NRP-1 in COVID-19 patients with AIS. SARS-CoV-2 may transmit to the brain through NRP-1 in the olfactory epithelium of the nasal cavity, leading to different neurological disorders, and therefore about 45% of COVID-19 patients had neurological manifestations. NRP-1 has the potential capability to attenuate neuroinflammation, blood–brain barrier (BBB) permeability, cerebral endothelial dysfunction (ED), and neuronal dysfunction that are uncommon in COVID-19 with neurological involvement, including AIS. Similarly, high NRP-1 serum level is linked with ED, oxidative stress, and the risk of pulmonary thrombosis in patients with severe COVID-19, suggesting a compensatory mechanism to overcome immuno-inflammatory disorders. In conclusion, NRP-1 has an important role in the pathogenesis of COVID-19 and AIS, and could be the potential biomarker linking the development of AIS in COVID-19. The present findings cannot provide a final conclusion, and thus in silico, experimental, in vitro, in vivo, preclinical, and clinical studies are recommended to confirm the potential role of NRP-1 in COVID-19, and to elucidate the pharmacological role of NRP-1 receptor agonists and antagonists in COVID-19.

CAN PULMONARY SURFACTANT PROTEINS BE RELIABLE INDICATORS OF COVID-19-ASSOCIATED PULMONARY INJURY?

The COVID-19 pandemic is still raging all over the world. New variants of the coronavirus emerge and infect recovered from previous infections, vaccinated, and unvaccinated subjects. One aspect remains unchanged that is the lungs are the main targets of the pandemic coronavirus. This challenging situation requires the search for reliable predictive markers of severe and complicated course of the disease. Serum surfactant proteins are known to correlate with pulmonary injury severity in numerous diseases. Measurement of such protein levels may help timely predict the risk. Surfactant proteins can also be helpful diagnostic purposes in COVID-19.

Laboratory Biomarkers for Diagnosis and Prognosis in COVID-19

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) causes a wide spectrum of clinical manifestations, with progression to multiorgan failure in the most severe cases. Several biomarkers can be altered in coronavirus disease 2019 (COVID-19), and they can be associated with diagnosis, prognosis, and outcomes. The most used biomarkers in COVID-19 include several proinflammatory cytokines, neuron-specific enolase (NSE), lactate dehydrogenase (LDH), aspartate transaminase (AST), neutrophil count, neutrophils-to-lymphocytes ratio, troponins, creatine kinase (MB), myoglobin, D-dimer, brain natriuretic peptide (BNP), and its N-terminal pro-hormone (NT-proBNP). Some of these biomarkers can be readily used to predict disease severity, hospitalization, intensive care unit (ICU) admission, and mortality, while others, such as metabolomic and proteomic analysis, have not yet translated to clinical practice. This narrative review aims to identify laboratory biomarkers that have shown significant diagnostic and prognostic value for risk stratification in COVID-19 and discuss the possible clinical application of novel analytic strategies, like metabolomics and proteomics. Future research should focus on identifying a limited but essential number of laboratory biomarkers to easily predict prognosis and outcome in severe COVID-19.

Surfactant protein D: A useful biomarker for distinguishing COVID‐19 pneumonia from COVID‐19 pneumonia‐like diseases

Introduction

Computed tomography is useful for the diagnosis of coronavirus disease (COVID‐19) pneumonia. However, many types of interstitial lung diseases and even bacterial pneumonia can show abnormal chest shadows that are indistinguishable from those observed in COVID‐19 pneumonia. Thus, it is necessary to identify useful biomarkers that can efficiently distinguish COVID‐19 pneumonia from COVID‐19 pneumonia‐like diseases. Herein, we investigated the usefulness of serum Krebs von den Lungen 6 (KL‐6) and surfactant protein D (SP‐D) for identifying patients with COVID‐19 pneumonia among patients with abnormal chest shadows consistent with COVID‐19 pneumonia.

Method

This was a retrospective cohort study of consecutive patients who underwent evaluation of serum KL‐6 and SP‐D at a single center from February 2019 to December 2020. A total of 54 patients with COVID‐19 pneumonia and 65 patients with COVID‐19 pneumonia‐like diseases were enrolled in this study from the source population. Serum KL‐6 and SP‐D levels in both groups were analyzed.

Result

The serum levels of KL‐6 and SP‐D in patients with COVID‐19 pneumonia were significantly lower than those in patients with COVID‐19 pneumonia‐like disease (median [interquartile range]: 208.5 [157.5–368.5] U/ml vs. 430 [284.5–768.5] U/ml, p < 0.0001 and 24.7 [8.6–51.0] ng/ml vs. 141 [63.7–243.5] ng/ml, p < 0.0001, respectively). According to receiver operating characteristic (ROC) analysis, the areas under the ROC curves (95% confidence intervals) of serum KL‐6 and SP‐D levels for distinguishing COVID‐19 pneumonia from COVID‐19 pneumonia‐like diseases were 0.761 (0.675–0.847) and 0.874 (0.812–0.936), respectively. The area under the ROC curve of serum SP‐D was significantly larger than that of serum KL‐6 (p = 0.0213), suggesting that serum SP‐D can more efficiently distinguish COVID‐19 pneumonia from COVID‐19 pneumonia‐like diseases.

Conclusion

Serum SP‐D is a promising biomarker for distinguishing COVID‐19 pneumonia from COVID‐19 pneumonia‐like diseases. Serum SP‐D can be useful for the management of patients with abnormal chest shadow mimicking COVID‐19 pneumonia.

Serum levels of laminin and von Willebrand factor in COVID-19 survivors 6 months after discharge

OBJECTIVES

The aim of this study was to evaluate the clinical characteristics, pulmonary diffusion function, chest computed tomography (CT), and serum lung cell damage indicators of coronavirus disease 2019 (COVID-19) survivors 6 months after discharge.

METHODS

Data of COVID-19 survivors discharged from hospital between January 21, 2020 and January 11, 2021 and healthy controls were collected. Serum levels of surfactant protein D (SP-D)¹, the receptor for advanced glycation end products (RAGE)², laminin, and von Willebrand factor (vWF) were measured in the healthy controls and COVID-19 survivors 6 months after discharge. The relationships between serum lung cell damage indicator levels and various parameters were explored.

RESULTS

Fifty-two COVID-19 survivors (31 with non-severe disease and 21 with severe disease) and 30 controls were included. Serum levels of laminin in COVID-19 survivors 6 months after discharge were significantly higher than those in the controls. The increase was more significant in elderly and female patients. Serum levels of RAGE and vWF were not statistically different from those of the controls. However, 6 months after discharge, COVID-19 survivors with abnormal chest CT and those in the severe group had higher vWF levels.

CONCLUSIONS

COVID-19 patients had abnormal lung injury indicators 6 months after discharge. The recovery time after infection is currently unknown, and long-term observation is required.

COVID-19: The Impact on Cardiovascular System

SARS-CoV-2 has been circulating in population worldwide for the past year and a half, and thus a vast amount of scientific literature has been produced in order to study the biology of the virus and the pathophysiology of COVID-19, as well as to determine the best way to prevent infection, treat the patients and eliminate the virus. SARS-CoV-2 binding to the ACE2 receptor is the key initiator of COVID-19. The ability of SARS-CoV-2 to infect various types of cells requires special attention to be given to the cardiovascular system, as it is commonly affected. Thorough diagnostics and patient monitoring are beneficial in reducing the risk of cardiovascular morbidity and to ensure the most favorable outcomes for the infected patients, even after they are cured of the acute disease. The multidisciplinary nature of the fight against the COVID-19 pandemic requires careful consideration from the attending clinicians, in order to provide fast and reliable treatment to their patients in accordance with evidence-based medicine principles. In this narrative review, we reviewed the available literature on cardiovascular implications of COVID-19; both the acute and the chronic.

Pattern Recognition Proteins: First Line of Defense Against Coronaviruses

The rapid outbreak of COVID-19 caused by the novel coronavirus SARS-CoV-2 in Wuhan, China, has become a worldwide pandemic affecting almost 204 million people and causing more than 4.3 million deaths as of August 11 2021. This pandemic has placed a substantial burden on the global healthcare system and the global economy. Availability of novel prophylactic and therapeutic approaches are crucially needed to prevent development of severe disease leading to major complications both acutely and chronically. The success in fighting this virus results from three main achievements: (a) Direct killing of the SARS-CoV-2 virus; (b) Development of a specific vaccine, and (c) Enhancement of the host's immune system. A fundamental necessity to win the battle against the virus involves a better understanding of the host's innate and adaptive immune response to the virus. Although the role of the adaptive immune response is directly involved in the generation of a vaccine, the role of innate immunity on RNA viruses in general, and coronaviruses in particular, is mostly unknown. In this review, we will consider the structure of RNA viruses, mainly coronaviruses, and their capacity to affect the lungs and the cardiovascular system. We will also consider the effects of the pattern recognition protein (PRP) trident composed by (a) Surfactant proteins A and D, mannose-binding lectin (MBL) and complement component 1q (C1q), (b) C-reactive protein, and (c) Innate and adaptive IgM antibodies, upon clearance of viral particles and apoptotic cells in lungs and atherosclerotic lesions. We emphasize on the role of pattern recognition protein immune therapies as a combination treatment to prevent development of severe respiratory syndrome and to reduce pulmonary and cardiovascular complications in patients with SARS-CoV-2 and summarize the need of a combined therapeutic approach that takes into account all aspects of immunity against SARS-CoV-2 virus and COVID-19 disease to allow mankind to beat this pandemic killer.