SARS-CoV-2 omicron sub-lineages differentially modulate interferon response in human lung epithelial cells.

Although most of the attention was focused on the characterization of changes in the Spike protein among variants of SARS-CoV-2 virus, mutations outside the Spike region are likely to contribute to virus pathogenesis, virus adaptation and escape to the immune system. Phylogenetic analysis of SARS-CoV-2 Omicron strains reveals that several virus sub-lineages could be distinguished, from BA.1 up to BA.5. Regarding BA.1, BA.2 and BA.5, several mutations concern viral proteins with antagonistic activity to the innate immune system, such as NSP1 (S135R), which is involved in mRNAs translation, exhibiting a general shutdown in cellular protein synthesis. Additionally, mutations and/or deletions in the ORF6 protein (D61L) and in the nucleoprotein N (P13L, D31-33ERS, P151S, R203K, G204R and S413R) have been reported, although the impact of such mutations on protein function has not been further studied. The aim of this study was to better investigate the innate immunity modulation by different Omicron sub-lineages, in the attempt to identify viral proteins that may affect virus fitness and pathogenicity. Our data demonstrated that, in agreement with a reduced Omicron replication in Calu-3 human lung epithelial cells compared to the Wuhan-1 strain, a lower secretion of interferon beta (IFN-ß) from cells was observed in all sub-lineages, except for BA.2. This evidence might be correlated with the presence of a mutation within the ORF6 protein (D61L), which is strikingly associated to the antagonistic function of the viral protein, since additional mutations in viral proteins acting as interferon antagonist were not detected or did not show significant influence. Indeed, the recombinant mutated ORF6 protein failed to inhibit IFN-ß production in vitro. Furthermore, we found an induction of IFN-ß transcription in BA.1 infected cells, that was not correlated with the cytokine release at 72 h post-infection, suggesting that post-transcriptional events can be involved in controlling the innate immunity.

Rapid Decrease in Fluoroquinolones Consumption following Implementation of a Simple Antimicrobial Stewardship Bundled Intervention in a University Hospital during the COVID-19 Pandemic.

Fluoroquinolones (FQs) represent an class of antibiotics of medical importance, but their use has been restricted due to their ecologic impact and associated side effects. The reduction of FQs use is an important goal of antimicrobial stewardship programs (ASP). This work describes an ASP focused on overall antibiotics and FQs consumption reduction. From January 2021, an ASP was implemented in a 700-bed teaching hospital. The ASP was based on: (i) antibiotics consumption monitoring system (DDD/100 bed days); (ii) mandatory antibiotic prescription-motivation (using a dedicated informatic format) with the goal of >75% of motivated prescriptions; and (iii) data feedback and training on FQs use indications. We evaluated the impact of the intervention on overall systemic antibiotics and FQs consumption according to the objectives posed by Italian PNCAR (National Action Plan on Antimicrobial Resistance). A decrease of 6.6% in antibiotic use was observed (2019 vs. 2021). Notably, the FQs consumption fell by 48.3% from 7.1 DDD/100 bd in 2019 to 3.7 DDD/100 bd in 2021 (p < 0.001). After six months of mandatory antibiotic prescription-indication, all units achieved the target set. The study suggests that a simple, bundled ASP intervention can be rapidly effective obtaining the objectives of PNCAR on the reduction of overall antibiotics and FQs consumption.

Rational Use of Monoclonal Antibodies as Therapeutic Treatment in an Oncologic Patient with Long COVID.

We present the case of a 76-year-old male patient persistently infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the setting of a stage IIIC cutaneous melanoma and non-Hodgkin's lymphoma (NHL). Due to the persistent coronavirus disease 19 (COVID-19), all cancer treatments were discontinued. Because of the worsening of his clinical state and the persistence of SARS-CoV-2 positivity for more than six months, the patient was treated with sotrovimab, which was ineffective due to resistance mutations acquired during that time. In order to resume cancer treatment and make the patient free from SARS-CoV-2, an in vitro screening of Evusheld monoclonal antibodies (tixagevumab-cilgavimab) against the viral strains isolated from the subject was performed. The promising results obtained during in vitro testing led to the authorization of the off-label use of Evusheld, which made the patient negative for SARS-CoV-2, thus, allowing him to resume his cancer treatment. This study highlights the Evusheld monoclonal antibodies' efficacy, not only in prevention but also in successful therapy against prolonged COVID-19. Therefore, testing neutralizing monoclonal antibodies in vitro against SARS-CoV-2 mutants directly isolated from patients could provide useful information for the treatment of people affected by long COVID.

PD-1/PD-L1 immune-checkpoint blockade induces immune effector cell modulation in metastatic non-small cell lung cancer patients: A single-cell flow cytometry approach.

Peripheral immune-checkpoint blockade with mAbs to programmed cell death receptor-1 (PD-1) (either nivolumab or pembrolizumab) or PD-Ligand-1 (PD-L1) (atezolizumab, durvalumab, or avelumab) alone or in combination with doublet chemotherapy represents an expanding treatment strategy for metastatic non-small cell lung cancer (mNSCLC) patients. This strategy lays on the capability of these mAbs to rescue tumor-specific cytotoxic T lymphocytes (CTLs) inactivated throughout PD-1 binding to PD-L1/2 in the tumor sites. This inhibitory interactive pathway is a physiological mechanism of prevention against dangerous overreactions and autoimmunity in case of prolonged and/or repeated CTL response to the same antigen peptides. Therefore, we have carried out a retrospective bioinformatics analysis by single-cell flow cytometry to evaluate if PD-1/PD-L1-blocking mAbs modulate the expression of specific peripheral immune cell subsets, potentially correlated with autoimmunity triggering in 28 mNSCLC patients. We recorded a treatment-related decline in CD4+ T-cell and B-cell subsets and in the neutrophil-to-lymphocyte ratio coupled with an increase in natural killer T (NKT), CD8+PD1+ T cells, and eosinophils. Treatment-related increase in autoantibodies [mainly antinuclear antibodies (ANAs) and extractable nuclear antigen (ENA) antibodies] as well as the frequency of immune-related adverse events were associated with the deregulation of specific immune subpopulations (e.g., NKT cells). Correlative biological/clinical studies with deep immune monitoring are badly needed for a better characterization of the effects produced by PD-1/PD-L1 immune-checkpoint blockade.

Antibody Response against Circulating Omicron Variants 8 Months after the Third Dose of mRNA Vaccine.

The COVID-19 wave is being recently propelled by BA.2 and, particularly, BA.5 lineages, showing clear transmission advantages over the previously circulating strains. In this study, neutralizing antibody responses against SARS-CoV-2 Wild-Type, BA.2 and BA.5 Omicron sublineages were evaluated among vaccinees, uninfected or infected with Omicron BA.1 strain, 8 months after the third dose of SARS-CoV-2 vaccine. The aim of this study was to compare the cross-protective humoral response to the currently circulating variant strains induced by vaccination, followed by Omicron infection in some subjects. Results showed a low antibody titer against all three variants in uninfected vaccinated subjects. On the other hand, vaccinated subjects, infected with BA.1 variant after receiving the third dose (about 40 days later), showed a strong response against both BA.2 and BA.5 strains, albeit with lower titers. This reinforces the concept that vaccination is fundamental to induce an adequate and protective immune response against SARS-CoV-2, but needs to be updated, in order to also widen the range of action towards emerging variants, phylogenetically distant from the Wuhan strain, against which the current formulation is targeted.

Cytomegalovirus Infection Is Associated with Development of Chronic Lung Allograft Dysfunction.

BACKGROUND: Cytomegalovirus (CMV) is the major and most common opportunistic infection complicating lung transplant (LTX). The aim of this study was to analyse the epidemiological aspects of CMV infection in lung transplant patients subject to a pre-emptive anti-CMV approach and to study the impact of this infection on lung transplant outcome, in terms of onset of chronic lung allograft dysfunction (CLAD). METHODS: This single-centre retrospective study enrolled 87 LTX patients (median age 55.81 years; 41 females, 23 single LTX, 64 bilateral LTX). All patients were managed with a pre-emptive anti-CMV approach. The incidences of the first episode of CMV infection, 1, 3, 6 and 12 months after LTX, were 12.64%, 44.26%, 50.77% and 56.14%. A median interval of 41 days elapsed between LTX and the first episode of CMV infection. The median blood load of CMV-DNA at diagnosis was 20,385 cp/ml; in 67.64% of cases, it was also the peak value. Patients who had at least one episode had shorter CLAD-free survival. Patients who had three or more episodes of CMV infection had the worst outcome. RESULTS: CMV infection was confirmed to be a common event in lung transplant patients, particularly in the first three months after transplant. It had a negative impact on transplant outcome, being a major risk factor for CLAD. The hypothesis that lower viral replication thresholds may increase the risk of CLAD is interesting and deserves further investigation.

Long-term SARS-CoV-2 Asymptomatic Carriage in an Immunocompromised Host: Clinical, Immunological, and Virological Implications.

PURPOSE: SARS-CoV-2 infection in immunocompromised hosts is challenging, and prolonged viral shedding can be a common complication in these patients. We describe the clinical, immunological, and virological course of a patient with eosinophilic granulomatosis with polyangiitis, who developed the status of long-term asymptomatic SARS-CoV-2 carrier for more than 7 months. METHODS: Over the study period, the patient underwent 20 RT-PCR tests for SARS-CoV-2 detection on nasopharyngeal swabs. In addition, viral cultures and genetic investigation of SARS-CoV-2 were performed. As for immunological assessment, serological and specific T-cell testing was provided at different time points. RESULTS: Despite the patient showing a deep drug-induced B and T adaptive immunity impairment, he did not experience COVID-19 progression to severe complications, and the infection remained asymptomatic during the follow-up period, but he was not able to achieve viral clearance for more than 7 months. The infection was finally cleared by SARS-CoV-2-specific monoclonal antibody treatment, after that remdesivir and convalescent plasma failed in this scope. The genetic investigations evidenced that the infection was sustained by multiple viral subpopulations that had apparently evolved intra-host during the infection. CONCLUSION: Our case suggests that people with highly impaired B- and T-cell adaptive immunity can prevent COVID-19 progression to severe complications, but they may not be able to clear SARS-CoV-2 infection. Immunocompromised hosts with a long-term infection may play a role in the emergence of viral variants.

Nucleopore Traffic Is Hindered by SARS-CoV-2 ORF6 Protein to Efficiently Suppress IFN-ß and IL-6 Secretion.

A weak production of INF-ß along with an exacerbated release of pro-inflammatory cytokines have been reported during infection by the novel SARS-CoV-2 virus. SARS-CoV-2 encodes several proteins that are able to counteract the host immune system, which is believed to be one of the most important features contributing to the viral pathogenesis and development of a severe clinical outcomes. Previous reports demonstrated that the SARS-CoV-2 ORF6 protein strongly suppresses INF-ß production by hindering the RIG-I, MDA-5, and MAVS signaling cascade. In the present study, we better characterized the mechanism by which the SARS-CoV-2 ORF6 counteracts IFN-ß and interleukin-6 (IL-6), which plays a crucial role in the inflammation process associated with the viral infection. In the present study, we demonstrated that the SARS-CoV-2 ORF6 protein has evolved an alternative mechanism to guarantee host IFN-ß and IL-6 suppression, in addition to the transcriptional control exerted on the genes. Indeed, a block in movement through the nucleopore of newly synthetized messenger RNA encoding the immune-modulatory cytokines IFN-ß and IL-6 are reported here. The ORF6 accessory protein of SARS-CoV-2 displays a multifunctional activity and may represent one of the most important virulence factors. Where conventional antagonistic strategies of immune evasion-such as the suppression of specific transcription factors (e.g., IRF-3, STAT-1/2)-would not be sufficient, the SARS-CoV-2 ORF6 protein is the trump card for the virus, also blocking the movement of IFN-ß and IL-6 mRNAs from nucleus to cytoplasm. Conversely, we showed that nuclear translocation of the NF-κB transcription factor is not affected by the ORF6 protein, although inhibition of its cytoplasmic activation occurred. Therefore, the ORF6 protein exerts a 360-degree inhibition of the antiviral response by blocking as many critical points as possible.

Omicron Infection Evokes Cross-Protection against SARS-CoV-2 Variants in Vaccinees.

Due to the rapid global spread of the Omicron (B.1.1.529) variant, efforts to scale up COVID-19 booster vaccination have been improved, especially in light of the increasing evidence of reduced neutralizing antibody (NT Ab) over time in vaccinated subjects. In this study, neutralizing antibody responses against the Wild-Type, Delta, and Omicron strains were evaluated among vaccinees, both infected with Omicron or uninfected, and non-vaccinated subjects infected with Omicron. The aim of the study was to compare the cross-protective humoral response to the variant strains induced by vaccination and/or Omicron infection. The results showed a significant difference in the neutralizing antibody response between the vaccinees and the Omicron-infected vaccinated subjects against the three tested strains (p < 0.001), confirming the booster effect of the Omicron infection in the vaccinees. By contrast, Omicron infection only did not enhance the antibody response to the other variants, indicating a lack of cross-protection. These results suggest the importance of updating the current formulation of the SARS-CoV-2 vaccine to protect people against the Omicron subvariants. A specific Omicron vaccine, administered as a booster for the previously adopted mRNA vaccines, may protect against a wider range of SARS-CoV-2 variants. However, it is unlikely that the Omicron vaccine alone would be able to protect non-vaccinated subjects against other circulating variants.

Infectious Toscana Virus in Seminal Fluid of Young Man Returning from Elba Island, Italy.

We report detecting infectious Toscana virus in the seminal fluid of a 25-year-old man from Italy returning from Elba Island. The presence of infectious virus in human semen adds Toscana virus to the long list of viruses detected in this genital fluid and indicates a potential for sexual transmission.

Human Polymorphonuclear Cells Support Zika Virus to Cross Endothelial Monolayer and Access Bloodstream.

The rapid spread of new outbreaks of human infection caused by Zika virus (ZIKV) has raised many global concerns since 2016. Despite the increasing knowledge of this virus, data on the pathogenesis of ZIKV are still missing. In particular, it is still unknown how the virus crosses the endothelial monolayer and gets access to the bloodstream. In the present work, we used human umbilical vein endothelial cells (HUVECs) as a model to study ZIKV infection in vitro. We demonstrated that HUVECs are an optimal reservoir for viral replication, as they were able to sustain ZIKV infection up to two weeks, without showing a cytopathic effect. In order to evaluate the integrity of endothelial monolayer, immunofluorescence was performed on mock-infected or ZIKV-infected cells ± peripheral blood mononuclear cells (PBMCs) or polymorphonuclear cells (PMN), 48 h p.i., by using an anti-VE-Cadherin antibody, a major adherence protein that maintains the integrity of intercellular junctions. In addition to infection, we noted that the presence of some components of the immune system, such as PMNs, played an important role in altering the endothelial monolayer in cell junctions, suggesting that presence at the site of infection probably promotes the spread of ZIKV in vivo in the bloodstream.

Validation of Two Commercial Multiplex Real-Time PCR Assays for Detection of SARS-CoV-2 in Stool Donors for Fecal Microbiota Transplantation.

Recurrent infection by Clostridioides difficile has recently been treated by fecal microbiota transplantation (FMT). As viable SARS-CoV-2 was recovered from stool of asymptomatic individuals, the FMT procedure could be a potential risk of SARS-CoV-2 transmission, thus underlying the need to reliably detect SARS-CoV-2 in stool. Here, we performed a multicentric study to explore performances of two commercially available assays for detection of SARS-CoV-2 RNA in stool of potential FMT donors. In three hospitals, 180 stool samples were spiked with serial 10-fold dilutions of a SARS-CoV-2 inactivated lysate to evaluate the Seegene Allplex™ SARS-CoV-2 (SC2) and SARS-CoV-2/FluA/FluB/RSV (SC2FABR) Assays for the detection of viral RNA in stool of FMT donors. The results revealed that both assays detected down to 2 TCID50/mL with comparable limit of detection values, SC2 showing more consistent target positivity rate than SC2FABR. Beyond high amplification efficiency, correlation between CT values and log concentrations of inactivated viral lysates showed R2 values ranging from 0.88 to 0.90 and from 0.87 to 0.91 for the SC2 and SC2FABR assay, respectively. The present results demonstrate that both methods are highly reproducible, sensitive, and accurate for SARS-CoV-2 RNA detection in stool, suggesting a potential use in FMT-donor screening.

Overview of Anti-SARS-CoV-2 Immune Response Six Months after BNT162b2 mRNA Vaccine.

BACKGROUND: We have designed a prospective study aiming to monitor the immune response in 178 health care workers six months after BNT162b2 mRNA vaccination. METHODS: The humoral immune response of all subjects was evaluated by chemiluminescence (CMIA); in 60 serum samples, a live virus-based neutralization assay was also tested. Moreover, 6 months after vaccination, B- and T-cell subsets from 20 subjects were observed by FACS analysis after restimulation with the trimeric SARS-CoV-2 Spike protein as an antigen, thus mimicking reinfection in vitro. RESULTS: A significant decrease of circulating IgG levels and neutralizing antibodies over time were observed. Moreover, six months after vaccination, a variable T-cell immune response after in vitro antigen stimulation of PBMC was observed. On the contrary, the analysis of B-cell response showed a shift from unswitched to switched memory B-cells and an increase of Th17 cells. CONCLUSIONS: Although the variability of the CD4+ and CD8+ immune response and an antibody decline was observed among vaccinated subjects, the increase of switched memory B-cells and Th17 cells, correlating with the presence of neutralizing antibodies, opened the debate on the correct timing of vaccination.

Efficient Inactivation of SARS-CoV-2 and Other RNA or DNA Viruses with Blue LED Light.

Blue LED light has proven to have a powerful bacteria-killing ability; however, little is known about its mechanism of virucidal activity. Therefore, we analyzed the effect of blue light on different respiratory viruses, such as adenovirus, respiratory syncytial virus and SARS-CoV-2. The exposure of samples to a blue LED light with a wavelength of 420 nm (i.e., in the visible range) at 20 mW/cm2 of irradiance for 15 min appeared optimal and resulted in the complete inactivation of the viral load. These results were similar for all the three viruses, demonstrating that both enveloped and naked viruses could be efficiently inactivated with blue LED light, regardless of the presence of envelope and of the viral genome nature (DNA or RNA). Moreover, we provided some explanations to the mechanisms by which the blue LED light could exert its antiviral activity. The development of such safe and low-cost light-based devices appears to be of fundamental utility for limiting viral spread and for sanitizing small environments, objects and surfaces, especially in the pandemic era.

Anatomy of an extensively drug-resistant Klebsiella pneumoniae outbreak in Tuscany, Italy.

A protracted outbreak of New Delhi metallo-ß-lactamase (NDM)-producing carbapenem-resistant Klebsiella pneumoniae started in Tuscany, Italy, in November 2018 and continued in 2020 and through 2021. To understand the regional emergence and transmission dynamics over time, we collected and sequenced the genomes of 117 extensively drug-resistant, NDM-producing K. pneumoniae isolates cultured over a 20-mo period from 76 patients at several healthcare facilities in southeast Tuscany. All isolates belonged to high-risk clone ST-147 and were typically nonsusceptible to all first-line antibiotics. Albeit sporadic, resistances to colistin, tigecycline, and fosfomycin were also observed as a result of repeated, independent mutations. Genomic analysis revealed that ST-147 isolates circulating in Tuscany were monophyletic and highly genetically related (including a network of 42 patients from the same hospital and sharing nearly identical isolates), and shared a recent ancestor with clinical isolates from the Middle East. While the blaNDM-1 gene was carried by an IncFIB-type plasmid, our investigations revealed that the ST-147 lineage from Italy also acquired a hybrid IncFIB/IncHIB-type plasmid carrying the 16S methyltransferase armA gene as well as key virulence biomarkers often found in hypervirulent isolates. This plasmid shared extensive homologies with mosaic plasmids circulating globally including from ST-11 and ST-307 convergent lineages. Phenotypically, the carriage of this hybrid plasmid resulted in increased siderophore production but did not confer virulence to the level of an archetypical, hypervirulent K. pneumoniae in a subcutaneous model of infection with immunocompetent CD1 mice. Our findings highlight the importance of performing genomic surveillance to identify emerging threats.

Comparative Performance of a New SARS-CoV-2 Rapid Detection System.

The extraordinary global demand for reagents and diagnostic instruments needed for timely detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has rapidly affected their availability. In order to meet diagnostic needs, it has been necessary to develop new diagnostic procedures. To date, molecular diagnostic tools have represented the gold standard for diagnosis of SARS-CoV-2 infection, and thus an alternative and real-time PCR system was required. To this aim, a molecular rapid test which works with direct real-time RT-PCR may be a relevant aid. In the present work, the accuracy, sensitivity, and specificity of the bKIT Virus Finder COVID-19 rapid molecular test by Hyris Ltd. was evaluated. Moreover, the influence of a different swab storage medium composition was examined relative to that of a routinely used comparator assay. The Hyris Ltd. assay showed an overall agreement of 100% with the comparator based on a panel consisting of 74 retrospective positive nasopharyngeal swabs (NPSs), collected either in universal transport medium (UTM) or using ESwab. No false-positive result was achieved on samples that previously tested negative. Cross-reactivity screening on microorganisms that commonly colonize the human upper respiratory tract was not detected, excluding the risk of false-positive results. Simultaneously, drugs frequently administered to cure respiratory diseases did not interfere with the analytical performance of the assay. Our results showed that the Hyris Ltd. bKIT Virus Finder COVID-19 is a reliable assay for rapid qualitative detection of SARS-CoV-2, providing the advantage of less complex and unambiguous interpretation of results. Indeed, skilled technicians are not required, and thus the Hyris system is suitable as a rapid and easy system for SARS-CoV-2 diagnosis. IMPORTANCE In order to overcome the increased demand for diagnostic tools for the timely detection of SARS-CoV-2 infection, we tested the bKIT Virus Finder COVID-19 molecular rapid test by Hyris Ltd. The new system was confirmed as a reliable assay for rapid SARS-CoV-2 detection, since sensitivity and specificity parameters were fully satisfied. Moreover, the bKIT Virus Finder COVID-19 provides the advantage of easy results interpretation, since skilled technicians are not required, and thus the Hyris system is a valuable SARS-CoV-2 rapid diagnosis system.

Identification of a Neutralizing Epitope on TOSV Gn Glycoprotein.

Emerging and re-emerging viral infections have been an important public health problem in recent years. We focused our attention on Toscana virus (TOSV), an emergent neurotropic negative-strand RNA virus of the Phenuiviridae family. The mechanisms of protection against phlebovirus natural infection are not known; however, it is supposed that a virus-neutralizing antibody response against viral glycoproteins would be useful to block the first stages of infection. By using an improved memory B cell immortalization method, we obtained a panel of human mAbs which reacted with TOSV antigens. We identified three epitopes of TOSV Gn glycoproteins by neutralizing mAbs using synthetic peptide arrays on membrane support (SPOT synthesis). These epitopes, separated in primary structure, might be exposed near one another as a conformational epitope in their native structure. In vivo studies were conducted to evaluate the humoral response elicited in mice immunized with the identified peptides. The results underlined the hypothesis that the first two peptides located in the NH2 terminus could form a conformational epitope, while the third, located near the transmembrane sequence in the carboxyl terminus, was necessary to strengthen neutralizing activity. Our results emphasize the importance of identifying neutralizing epitopes shared among the various phleboviruses, which could be exploited for the development of a potential epitope-based diagnostic assay or a polyvalent protective vaccine against different phleboviruses.

SARS-CoV-2 N Protein Targets TRIM25-Mediated RIG-I Activation to Suppress Innate Immunity.

A weak production of INF-ß along with an exacerbated release of pro-inflammatory cytokines have been reported during infection by the novel SARS-CoV-2 virus. SARS-CoV-2 encodes several proteins able to counteract the host immune system, which is believed to be one of the most important features contributing to the viral pathogenesis and development of a severe clinical picture. Previous reports have demonstrated that SARS-CoV-2 N protein, along with some non-structural and accessory proteins, efficiently suppresses INF-ß production by interacting with RIG-I, an important pattern recognition receptor (PRR) involved in the recognition of pathogen-derived molecules. In the present study, we better characterized the mechanism by which the SARS-CoV-2 N counteracts INF-ß secretion and affects RIG-I signaling pathways. In detail, when the N protein was ectopically expressed, we noted a marked decrease in TRIM25-mediated RIG-I activation. The capability of the N protein to bind to, and probably mask, TRIM25 could be the consequence of its antagonistic activity. Furthermore, this interaction occurred at the SPRY domain of TRIM25, harboring the RNA-binding activity necessary for TRIM25 self-activation. Here, we describe new findings regarding the interplay between SARS-CoV-2 and the IFN system, filling some gaps for a better understanding of the molecular mechanisms affecting the innate immune response in COVID-19.