Exogenous Klotho Extends Survival in COVID-19 Model Mice

A striking feature of COVID-19 disease is the broad spectrum of risk factors associated with case severity, as well as the diversity of clinical manifestations. While no central agent has been able to explain the pathogenesis of SARS-CoV-2 infection, the factors that most robustly correlate with severity are risk factors linked to aging. Low serum levels of Klotho, an anti-aging protein, strongly correlate with the pathogenesis of the same risk factors and manifestations of conditions similar to those expressed in severe COVID-19 cases. The current manuscript presents original research on the effects of the exogenous application of Klotho, an anti-aging protein, in COVID-19 model mice. Klotho supplementation resulted in a statistically significant survival benefit in parametric and non-parametric models. Further research is required to elucidate the mechanistic role Klotho plays in COVID-19 pathogenesis as well as the possible modulation SARS-CoV-2 may have on the biological aging process.

Extrafollicular IgD-CD27-CXCR5-CD11c- DN3 B cells infiltrate inflamed tissues in autoimmune fibrosis and in severe COVID-19

Although therapeutic B cell depletion dramatically resolves inflammation in many diseases in which antibodies appear not to play a central role, distinct extrafollicular pathogenic B cell subsets that accumulate in disease lesions have hitherto not been identified. The circulating immunoglobulin D (IgD)-CD27-CXCR5-CD11c+ DN2 B cell subset has been previously studied in some autoimmune diseases. A distinct IgD-CD27-CXCR5-CD11c- DN3 B cell subset accumulates in the blood both in IgG4-related disease, an autoimmune disease in which inflammation and fibrosis can be reversed by B cell depletion, and in severe COVID-19. These DN3 B cells prominently accumulate in the end organs of IgG4-related disease and in lung lesions in COVID-19, and double-negative B cells prominently cluster with CD4+ T cells in these lesions. Extrafollicular DN3 B cells may participate in tissue inflammation and fibrosis in autoimmune fibrotic diseases, as well as in COVID-19.

SARS-CoV-2 infection of phagocytic immune cells and COVID-19 pathology: Antibody-dependent as well as independent cell entry

Our review summarizes the evidence that COVID-19 can be complicated by SARS-CoV-2 infection of immune cells. This evidence is widespread and accumulating at an increasing rate. Research teams from around the world, studying primary and established cell cultures, animal models, and analyzing autopsy material from COVID-19 deceased patients, are seeing the same thing, namely that some immune cells are infected or capable of being infected with the virus. Human cells most vulnerable to infection include both professional phagocytes, such as monocytes, macrophages, and dendritic cells, as well as nonprofessional phagocytes, such as B-cells. Convincing evidence has accumulated to suggest that the virus can infect monocytes and macrophages, while data on infection of dendritic cells and B-cells are still scarce. Viral infection of immune cells can occur directly through cell receptors, but it can also be mediated or enhanced by antibodies through the Fc gamma receptors of phagocytic cells. Antibody-dependent enhancement (ADE) most likely occurs during the primary encounter with the pathogen through the first COVID-19 infection rather than during the second encounter, which is characteristic of ADE caused by other viruses. Highly fucosylated antibodies of vaccinees seems to be incapable of causing ADE, whereas afucosylated antibodies of persons with acute primary infection or convalescents are capable. SARS-CoV-2 entry into immune cells can lead to an abortive infection followed by host cell pyroptosis, and a massive inflammatory cascade. This scenario has the most experimental evidence. Other scenarios are also possible, for which the evidence base is not yet as extensive, namely productive infection of immune cells or trans-infection of other non-immune permissive cells. The chance of a latent infection cannot be ruled out either.

In silico Analysis of SARS-CoV-2 ORF8-Binding Proteins Reveals the Involvement of ORF8 in Acquired-Immune and Innate-Immune Systems

SARS-CoV-2 is the causative agent of a new type of coronavirus infection, COVID-19, which has rapidly spread worldwide. The overall genome sequence homology between SARS-CoV-2 and SARS-CoV is 79%. However, the homology of the ORF8 protein between these two coronaviruses is low, at ~26%. Previously, it has been suggested that infection by the ORF8-deleted variant of SARS-CoV-2 results in less severe symptoms than in the case of wild-type SARS-CoV-2. Although we found that ORF8 is involved in the proteasome autoimmunity system, the precise role of ORF8 in infection and pathology has not been fully clarified. In this study, we determined a new network of ORF8-interacting proteins by performing in silico analysis of the binding proteins against the previously described 47 ORF8-binding proteins. We used as a dataset 431 human protein candidates from Uniprot that physically interacted with 47 ORF8-binding proteins, as identified using STRING. Homology and phylogenetic profile analyses of the protein dataset were performed on 446 eukaryotic species whose genome sequences were available in KEGG OC. Based on the phylogenetic profile results, clustering analysis was performed using Ward's method. Our phylogenetic profiling showed that the interactors of the ORF8-interacting proteins were clustered into three classes that were conserved across chordates (Class 1: 152 proteins), metazoans (Class 2: 163 proteins), and eukaryotes (Class 3: 114 proteins). Following the KEGG pathway analysis, classification of cellular localization, tissue-specific expression analysis, and a literature study on each class of the phylogenetic profiling cluster tree, we predicted that the following: protein members in Class 1 could contribute to COVID-19 pathogenesis via complement and coagulation cascades and could promote sarcoidosis; the members of Class 1 and 2, together, may contribute to the downregulation of Interferon-β; and Class 3 proteins are associated with endoplasmic reticulum stress and the degradation of human leukocyte antigen.

Hypoxia may be a determinative factor in COVID-19 progression

The disease which develops following SARS-CoV-2 virus infection, known as COVID-19, in most affected countries displays mortality from 1.5% to 9.8%. When leukocytosis due to granulocytosis, thrombocytopenia, and increased level of D-dimers are detected early during the disease course, they are accurate predictors of mortality. Based on the published observations that each of the aforementioned disturbances by itself may appear as a consequence of hypoxia, a hypothesis is presented that early hypoxia consequential to sleep apnea and/or blunted respiratory response to chemical stimuli is an early determinant of COVID-19 progression to the severe and critical stage. Further, it is noted that host-directed therapies which may counteract hypoxia and its early downstream effects are initiated only upon hospitalization of COVID-19 patients, which is too late to be fully effective. An example is anticoagulation treatment with low molecular weight heparin. Repurposing drugs which could counteract some early posthypoxic events, such as fluvoxamine, amantadine and N-acetylcysteine, for post-exposure prophylaxis of SARS-CoV-2 infection and early prehospital treatment of COVID-19, is indicated.

Decrypting the role of predicted SARS-CoV-2 miRNAs in COVID-19 pathogenesis: A bioinformatics approach

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is a highly transmissible virus causing the ongoing global pandemic, COVID-19. Evidence suggests that viral and host microRNAs play pivotal roles in progression of such infections. The decisive impact of viral miRNAs and their putative targets in modulating the transcriptomic profile of its host, however remains unexplored. We hypothesized that the SARS-CoV-2 derived miRNAs can potentially play a contributory role in its pathogenicity and aid in its survival. A series of computational tools predicted 34 SARS-CoV-2 encoded miRNAs and their putative targets in the host. Immune and apoptotic pathways were identified as most enriched pathways. Further investigation using a dataset of SARS-CoV-2 infected cells (available from public repository- GSE150392) revealed that 46 genes related to immune and apoptosis-related functions were deregulated. Of these 46 genes, 42 genes were identified to be significantly up-regulated and 4 genes were down-regulated. In silico analysis revealed all of the these significantly down-regulated genes to be putative targets of 9 out of 34 of our predicted viral miRNAs. Overall, 123 out of 324 genes that are differentially regulated in SARS-CoV2 infected cells, and also identified as putative targets of viral miRNAs, were found to be significantly down-regulated. KEGG pathway analysis using these genes revealed p53 signaling as the most enriched pathway – a pathway that is known to influence immune responses. This study thus provides the theoretical foundation for the underlying molecular mechanisms involved in progression of viral pathogenesis.

Free SARS-CoV-2 Spike Protein S1 Particles May Play a Role in the Pathogenesis of COVID-19 Infection

The imbalance of the renin-angiotensin system is currently considered as a potentially important factor of the pathogenesis of COVID-19 disease. It has been shown previously in the murine model, that the expression of angiotensin-converting enzyme 2 (ACE2) on the cell surface is downregulated in response to the infection by SARS-CoV virus or recombinant spike protein (S protein) alone. In the case of natural infection, circulation of the S protein in a soluble form is unlikely. However, in SARS-CoV-2, a large fraction of S protein trimers is pre-processed during virion morphogenesis due to the presence of furin protease cleavage site between the S1 and S2 subunits. Therefore, S protein transition into the fusion conformation may be accompanied by the separation of the S1 subunits carrying the receptor-binding domains from the membrane-bound S2 subunits. The fate of the S1 particles shed due to the spontaneous "firing" of some S protein trimers exposed on the virions and on the surface of infected cells has been never investigated. We hypothesize that the soluble S1 subunits of the SARS-CoV-2 S protein shed from the infected cells and from the virions in vivo may bind to the ACE2 and downregulate cell surface expression of this protein. The decrease in the ACE2 activity on the background of constant or increased ACE activity in the lungs may lead to the prevalence of angiotensin II effects over those of angiotensin (1-7), thus promoting thrombosis, inflammation, and pulmonary damage. This hypothesis also suggests the association between less pronounced shedding of the S1 particles reported for the S protein carrying the D614G mutation (vs. the wild type D614 protein), and lack of increased severity of the COVID-19 infection caused by the mutant (D614G) SARS-CoV-2 strain, despite its higher infectivity and higher in vivo viral load.

Temporal dynamics of the host molecular responses underlying severe COVID-19 progression and disease resolution

BACKGROUND

The coronavirus disease-19 (COVID-19) pandemic has cost lives and economic hardships globally. Various studies have found a number of different factors, such as hyperinflammation and exhausted/suppressed T cell responses to the etiological SARS coronavirus-2 (SARS-CoV-2), being associated with severe COVID-19. However, sieving the causative from associative factors of respiratory dysfunction has remained rudimentary.

METHODS

We postulated that the host responses causative of respiratory dysfunction would track most closely with disease progression and resolution and thus be differentiated from other factors that are statistically associated with but not causative of severe COVID-19. To track the temporal dynamics of the host responses involved, we examined the changes in gene expression in whole blood of 6 severe and 4 non-severe COVID-19 patients across 15 different timepoints spanning the nadir of respiratory function.

FINDINGS

We found that neutrophil activation but not type I interferon signaling transcripts tracked most closely with disease progression and resolution. Moreover, transcripts encoding for protein phosphorylation, particularly the serine-threonine kinases, many of which have known T cell proliferation and activation functions, were increased after and may thus contribute to the upswing of respiratory function. Notably, these associative genes were targeted by dexamethasone, but not methylprednisolone, which is consistent with efficacy outcomes in clinical trials.

INTERPRETATION

Our findings suggest neutrophil activation as a critical factor of respiratory dysfunction in COVID-19. Drugs that target this pathway could be potentially repurposed for the treatment of severe COVID-19.

FUNDING

This study was sponsored in part by a generous gift from The Hour Glass. EEO and JGL are funded by the National Medical Research Council of Singapore, through the Clinician Scientist Awards awarded by the National Research Foundation of Singapore.

Isolation of SARS-CoV-2 strains carrying a nucleotide mutation, leading to a stop codon in the ORF 6 protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was isolated from the oro/pharyngeal swabs of two Italian COVID-19 patients, physicians in a COVID-19 division hospital, with different courses of the disease. The complete genome sequences show that the two isolates belong to the B1.1 lineage, but contain a nucleotide mutation in the ORF6, leading to a stop codon and to the deletion of 6 amino acids in the C terminus. This deletion was unique, compared to the currently available sequences deposited in the GISAID and GenBank database. It did not affect the in vitro viral replication, neither the neutralizing activities of the patients' antibodies. Based on homology analysis with other Coronaviruses, the two isolated lacked the ORF6 aminoacidic portion responsible for the inhibition of the antiviral Interferon (IFN)-based host response. IFN seems to have a dual role of in SARS-CoV-2 infected patients: not only antiviral activity, but also a detrimental role in case of excessive production. A deletion in the SARS-CoV-2 ORF6 protein might have a specific, still unknown role in the viral pathogenesis.

Alveolar epithelial cell type II as main target of SARS-CoV-2 virus and COVID-19 development via NF-Kb pathway deregulation: A physio-pathological theory

The Corona Virus Disease (COVID-19) pandemic caused by Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) requires a rapid solution and global collaborative efforts in order to define preventive and treatment strategies. One of the major challenges of this disease is the high number of patients needing advanced respiratory support due to the Acute Respiratory Distress Syndrome (ARDS) as the lung is the major - although not exclusive - target of the virus. The molecular mechanisms, pathogenic drivers and the target cell type(s) in SARS-CoV-2 infection are still poorly understood, but the development of a "hyperactive" immune response is proposed to play a role in the evolution of the disease and it is envisioned as a major cause of morbidity and mortality. Here we propose a theory by which the main targets for SARS-CoV-2 are the Type II Alveolar Epithelial Cells and the clinical manifestations of the syndrome are a direct consequence of their involvement. We propose the existence of a vicious cycle by which once alveolar damage starts in AEC II cells, the inflammatory state is supported by macrophage pro-inflammatory polarization (M1), cytokines release and by the activation of the NF-κB pathway. If this theory is confirmed, future therapeutic efforts can be directed to target Type 2 alveolar cells and the molecular pathogenic drivers associated with their dysfunction with currently available therapeutic strategies.

The role of host genetics in susceptibility to severe viral infections in humans and insights into host genetics of severe COVID-19: A systematic review

BACKGROUND

Susceptibility to severe viral infections was reported to be associated with genetic variants in immune response genes using case reports and GWAS studies. SARS-CoV-2 is an emergent viral disease that caused millions of COVID-19 cases all over the world. Around 15 % of cases are severe and some of them are accompanied by dysregulated immune system and cytokine storm. There is increasing evidence that severe manifestations of COVID-19 might be attributed to human genetic variants in genes related to immune deficiency and or inflammasome activation (cytokine storm).

OBJECTIVE

Identify the candidate genes that are likely to aid in explaining severe COVID-19 and provide insights to understand the pathogenesis of severe COVID-19.

METHODS

In this article, we systematically reviewed genes related to viral susceptibility that were reported in human genetic studies (Case-reports and GWAS) to understand the role of host viral interactions and to provide insights into the pathogenesis of severe COVID-19.

RESULTS

We found 40 genes associated with viral susceptibility and 21 of them were associated with severe SARS-CoV disease and severe COVID-19. Some of those genes were implicated in TLR pathways, others in C-lectin pathways, and others were related to inflammasome activation (cytokine storm).

CONCLUSION

This compilation represents a list of candidate genes that are likely to aid in explaining severe COVID-19 which are worthy of inclusion in gene panels and during meta-analysis of different variants in host genetics studies of COVID-19. In addition, we provide several hypotheses for severe COVID-19 and possible therapeutic targets.

Novel therapeutic approaches toward Hantaan virus and its clinical features' similarity with COVID-19

Zoonotic virus spill over in human community has been an intensive area of viral pathogenesis and the outbreak of Hantaan virus and severe acute respiratory syndrome coronavirus 2 (SARS CoV2) after late December 2019 caused a global threat. Hantaan virus is second to the COVID-19 outbreak in China with seven cases positive and one death. Both RNA viruses have opposite sense as in (-) for Hantaan virus and (+) for SARS CoV2 but have similarity in the pathogenesis and relevant clinical features including dry cough, high fever, shortness of breath, and SARS associated with pneumonia and certain reported cases with multiple organ failure. Although COVID-19 has global impact with high death toll, Hantaan virus has varyingly high mortality rate between 1% and 40%. Hence, there is a need to explore novel therapeutic targets in Hantaan virus due to its rapid evolution rate in its genetic makeup which governs virulence and target host cells. This review emphasizes the importance of structural and nonstructural proteins of Hantaan virus with relevant insight from SARS CoV2. The envelope glycoproteins such as Gn, Gc, and nucleocapsid protein (N) direct the viral assembly and replication in host cells. Therapeutic treatment has similarity in using ribavirin and extracorporeal membrane oxygenation but lack of efficacious treatment in both cases of SARAS CoV2 and Hantaan virus. Therefore, potential features regarding therapeutic targets for drug discovery for Hantaan viruses are discussed herewith. The conclusive description highlights that N protein is substantially involved in evoking immune response and induces symptoms and could be precursive target for drug discovery studies.

COVID-19: Unanswered questions on immune response and pathogenesis

The novel coronavirus disease 2019 has rapidly increased in pandemic scale since it first appeared in Wuhan, China, in December 2019. In these troubled days the scientific community is asking for rapid replies to prevent and combat the emergency. It is generally accepted that only achieving a better understanding of the interactions between the virus and the host immune response and of the pathogenesis of infection is crucial to identify valid therapeutic tools to control virus entry, replication, and spread as well as to impair its lethal effects. On the basis of recent research progress of severe acute respiratory syndrome coronavirus 2 and the results on previous coronaviruses, in this contribution we underscore some of the main unsolved problems, mostly focusing on pathogenetic aspects and host immunity to the virus. On this basis, we also touch important aspects regarding the immune response in asymptomatic subjects, the immune evasion of severe acute respiratory syndrome coronavirus 2 in severe patients, and differences in disease severity by age and sex.