Gene silencing of endothelial von Willebrand factor reduces the susceptibility of human endothelial cells to SARS-CoV-2 infection.

Mechanisms underlying vascular endothelial susceptibility to infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not fully understood. Emerging evidence indicates that patients lacking von Willebrand factor (vWF), an endothelial hallmark, are less severely affected by SARS-CoV-2 infection, yet the precise role of endothelial vWF in modulating coronavirus entry into endothelial cells is unknown. In the present study, we demonstrated that effective gene silencing by short interfering RNA (siRNA) for vWF expression in resting human umbilical vein endothelial cells (HUVECs) significantly reduced by 56% the cellular levels of SARS-CoV-2 genomic RNA. Similar reduction in intracellular SARS-CoV-2 genomic RNA levels was observed in non-activated HUVECs treated with siRNA targeting angiotensin-converting enzyme 2 (ACE2), the cellular gateway to coronavirus. By integrating quantitative information from real-time PCR and high-resolution confocal imaging, we demonstrated that ACE2 gene expression and its plasma membrane localization in HUVECs were both markedly reduced after treatment with siRNA anti-vWF or anti-ACE2. Conversely, siRNA anti-ACE2 did not reduce endothelial vWF gene expression and protein levels. Finally, SARS-CoV-2 infection of viable HUVECs was enhanced by overexpression of vWF, which increased ACE2 levels. Of note, we found a similar increase in interferon-ß mRNA levels following transfection with untargeted, anti-vWF or anti-ACE2 siRNA and pcDNA3.1-WT-VWF. We envision that siRNA targeting endothelial vWF will protect against productive endothelial infection by SARS-CoV-2 through downregulation of ACE2 expression and might serve as a novel tool to induce disease resistance by modulating the regulatory role of vWF on ACE2 expression.

Palmitoylethanolamide (PEA) Inhibits SARS-CoV-2 Entry by Interacting with S Protein and ACE-2 Receptor.

Lipids play a crucial role in the entry and egress of viruses, regardless of whether they are naked or enveloped. Recent evidence shows that lipid involvement in viral infection goes much further. During replication, many viruses rearrange internal lipid membranes to create niches where they replicate and assemble. Because of the close connection between lipids and inflammation, the derangement of lipid metabolism also results in the production of inflammatory stimuli. Due to its pivotal function in the viral life cycle, lipid metabolism has become an area of intense research to understand how viruses seize lipids and to design antiviral drugs targeting lipid pathways. Palmitoylethanolamide (PEA) is a lipid-derived peroxisome proliferator-activated receptor-α (PPAR-α) agonist that also counteracts SARS-CoV-2 entry and its replication. Our work highlights for the first time the antiviral potency of PEA against SARS-CoV-2, exerting its activity by two different mechanisms. First, its binding to the SARS-CoV-2 S protein causes a drop in viral infection of ~70%. We show that this activity is specific for SARS-CoV-2, as it does not prevent infection by VSV or HSV-2, other enveloped viruses that use different glycoproteins and entry receptors to mediate their entry. Second, we show that in infected Huh-7 cells, treatment with PEA dismantles lipid droplets, preventing the usage of these vesicular bodies by SARS-CoV-2 as a source of energy and protection against innate cellular defenses. This is not surprising since PEA activates PPAR-α, a transcription factor that, once activated, generates a cascade of events that leads to the disruption of fatty acid droplets, thereby bringing about lipid droplet degradation through ß-oxidation. In conclusion, the present work demonstrates a novel mechanism of action for PEA as a direct and indirect antiviral agent against SARS-CoV-2. This evidence reinforces the notion that treatment with this compound might significantly impact the course of COVID-19. Indeed, considering that the protective effects of PEA in COVID-19 are the current objectives of two clinical trials (NCT04619706 and NCT04568876) and given the relative lack of toxicity of PEA in humans, further preclinical and clinical tests will be needed to fully consider PEA as a promising adjuvant therapy in the current COVID-19 pandemic or against emerging RNA viruses that share the same route of replication as coronaviruses.

A spatial multi-scale fluorescence microscopy toolbox discloses entry checkpoints of SARS-CoV-2 variants in Vero E6 cells.

We exploited a multi-scale microscopy imaging toolbox to address some major issues related to SARS-CoV-2 interactions with host cells. Our approach harnesses both conventional and super-resolution fluorescence microscopy and easily matches the spatial scale of single-virus/cell checkpoints. After its validation through the characterization of infected cells and virus morphology, we leveraged this toolbox to reveal subtle issues related to the entry phase of SARS-CoV-2 variants in Vero E6 cells. Our results show that in Vero E6 cells the B.1.1.7 strain (aka Alpha Variant of Concern) is associated with much faster kinetics of endocytic uptake compared to its ancestor B.1.177. Given the cell-entry scenario dominated by the endosomal "late pathway", the faster internalization of B.1.1.7 could be directly related to the N501Y mutation in the S protein, which is known to strengthen the binding of Spike receptor binding domain with ACE2. Remarkably, we also directly observed the central role of clathrin as a mediator of endocytosis in the late pathway of entry. In keeping with the clathrin-mediated endocytosis, we highlighted the non-raft membrane localization of ACE2. Overall, we believe that our fluorescence microscopy-based approach represents a fertile strategy to investigate the molecular features of SARS-CoV-2 interactions with cells.

Patterns of neutralizing humoral response to SARS-CoV-2 infection among hematologic malignancy patients reveal a robust immune response in anti-cancer therapy-naive patients.

Understanding antibody-based SARS-CoV-2 immunity in hematologic malignancy (HM) patients following infection is crucial to inform vaccination strategies for this highly vulnerable population. This cross-sectional study documents the anti-SARS-CoV-2 humoral response and serum neutralizing activity in 189 HM patients recovering from a PCR-confirmed infection. The overall seroconversion rate was 85.7%, with the lowest values in patients with lymphoid malignancies or undergoing chemotherapy. Therapy-naive patients in the "watch and wait" status were more likely to seroconvert and display increased anti-s IgG titers. Enhanced serum neutralizing activity was observed in the following SARS-CoV-2-infected HM patient groups: (i) males; (ii) severe COVID-19; and (iii) "watch and wait" or "complete/partial response". The geometric mean (GeoMean) ID50 neutralization titers in patients analyzed before or after 6 months post-infection were 299.1 and 306.3, respectively, indicating that >50% of the patients in either group had a neutralization titer sufficient to provide 50% protection from symptomatic COVID-19. Altogether, our findings suggest that therapy-naive HM patients mount a far more robust immune response to SARS-CoV-2 infection vs. patients receiving anti-cancer treatment, raising the important question as to whether HM patients should be vaccinated before therapy and/or receive vaccine formats capable of better recapitulating the natural infection.

Assessment of automated high-throughput serological assays for prediction of high-titer SARS-CoV-2 neutralizing antibody.

COVID19 convalescent patient plasma units with high titer neutralizing antibody can be used to treat patients with severe disease. Therefore, in order to select suitable donors, neutralizing antibody titer against SARS CoV-2 needs to be determined. Because the neutralization assay is highly demanding from several points of view, a pre-selection of sera would be desirable to minimize the number of sera to be tested. In this study, a total of 140 serum samples that had been titrated for SARS-CoV-2 neutralizing antibody by microneutralization assay were also tested for the presence of anti-SARS-CoV2 antibody using 5 different tests: Architect® immunoassay (Abbott Diagnostics), detecting IgG against the nucleocapsid protein, LIAISON XL® (Diasorin) detecting IgG against a recombinant form of the S1/S2 subunits of the spike protein, VITROS® (Ortho Clinical Diagnostics), detecting IgG against a recombinant form of the spike protein, and ELISA (Euroimmun AG), detecting IgA or IgG against a recombinant form of the S1 subunit. To determine which immunoassay had the highest chance to detect sera with neutralizing antibodies above a certain threshold, we compared the results obtained from the five immunoassays with the titers obtained by microneutralization assay by linear regression analysis and by using receiver operating characteristic curve and Youden's index. Our results indicate that the most suitable method to predict sera with high Nab titer is Euroimmun® IgG, followed closely by Ortho VITROS® Anti-SARS-CoV-2 IgG.

Nicotine upregulates ACE2 expression and increases competence for SARS-CoV-2 in human pneumocytes.

The coronavirus disease 2019 (COVID-19) pandemic has a variable degree of severity according to underlying comorbidities and life-style. Several research groups have reported an association between cigarette smoking and increased severity of COVID-19. The exact mechanism of action is largely unclear. We exposed low angiotensin-converting enzyme 2 (ACE2)-expressing human pulmonary adenocarcinoma A549 epithelial cells to nicotine and assessed ACE2 expression at different times. We further used the nicotine-exposed cells in a virus neutralisation assay. Nicotine exposure induces rapid and long-lasting increases in gene and protein expression of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor ACE2, which in turn translates into increased competence for SARS-CoV-2 replication and cytopathic effect. These findings show that nicotine worsens SARS-CoV-2 pulmonary infection and have implications for public health policies.