Dysregulation of intracellular redox homeostasis by the SARS-CoV-2 ORF6 protein.

SARS-CoV-2 has evolved several strategies to overcome host cell defenses by inducing cell injury to favour its replication. Many viruses have been reported to modulate the intracellular redox balance, affecting the Nuclear factor erythroid 2-Related Factor 2 (NRF2) signaling pathway. Although antioxidant modulation by SARS-CoV-2 infection has already been described, the viral factors involved in modulating the NRF2 pathway are still elusive. Given the antagonistic activity of ORF6 on several cellular pathways, we investigated the role of the viral protein towards NRF2-mediated antioxidant response. The ectopic expression of the wt-ORF6 protein negatively impacts redox cell homeostasis, leading to an increase in ROS production, along with a decrease in NRF2 protein and its downstream controlled genes. Moreover, when investigating the Δ61 mutant, previously described as an inactive nucleopore proteins binding mutant, we prove that the oxidative stress induced by ORF6 is substantially related to its C-terminal domain, speculating that ORF6 mechanism of action is associated with the inhibition of nuclear mRNA export processes. In addition, activation by phosphorylation of the serine residue at position 40 of NRF2 is increased in the cytoplasm of wt-ORF6-expressing cells, supporting the presence of an altered redox state, although NRF2 nuclear translocation is hindered by the viral protein to fully antagonize the cell response. Furthermore, wt-ORF6 leads to phosphorylation of a stress-activated serine/threonine protein kinase, p38 MAPK, suggesting a role of the viral protein in regulating p38 activation. These findings strengthen the important role of oxidative stress in the pathogenesis of SARS-CoV-2 and identify ORF6 as an important viral accessory protein hypothetically involved in modulating the antioxidant response during viral infection.

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.

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.

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.

SARS-CoV-2 infection in cancer patients on active therapy after the booster dose of mRNA vaccines.

INTRODUCTION: The protective role against SARS-CoV-2 infection by the third booster dose of mRNA vaccines in cancer patients with solid malignancies is presently unknown. We prospectively investigated the occurrence of COVID-19 in cancer patients on active therapy after the booster vaccine dose. METHODS: Cancer patients on treatment at the Center for Immuno-Oncology (CIO) of the University Hospital of Siena, Italy, and health care workers at CIO who had received a booster third dose of mRNA vaccine entered a systematic follow-up monitoring period to prospectively assess their potential risk of SARS-CoV-2 infection. Serological and microneutralization assay were utilized to assess levels of anti-spike IgG, and of neutralizing antibodies to the SARS-CoV-2 Wild Type, Delta and Omicron variants, respectively, after the booster dose and after negativization of the nasopharyngeal swab for those who had developed COVID-19. RESULTS: Ninety cancer patients with solid tumors on active treatment (Cohort 1) and 30 health care workers (Cohort 2) underwent a booster third dose of mRNA vaccine. After the booster dose, the median value of anti-spike IgG was higher (p = 0.009) in patients than in healthy subjects. Remarkably, 11/90 (12%) patients and 11/30 (37%) healthy subjects tested positive to SARS-CoV-2 infection during the monitoring period. Similar levels of anti-spike IgG and of neutralizing antibodies against all the investigated variants, with geometric mean titers of neutralizing antibodies against the Omicron being the lowest were detected after the booster dose and after COVID-19 in both Cohorts. CONCLUSIONS: The occurrence of SARS-CoV-2 infection we observed in a sizable proportion of booster-dosed cancer patients and in healthy subjects during the Omicron outbreak indicates that highly specific vaccines against SARS-CoV-2 variants are urgently required.

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.

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.

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.

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.

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.

Hyperimmune plasma in three immuno-deficient patients affected by non-severe, prolonged COVID-19: a single-center experience.

BACKGROUND: Convalescent plasma (CP) and hyperimmune plasma (HP) are passive immunotherapies consisting in the infusion of plasma from recovered people into infected patients. Following pre-existing evidence in many other viral diseases, such as SARS, MERS and Ebola, CP and HP have also been proposed for the treatment of COVID-19. Nevertheless, due to the lack of large, well-designed, clinical trials, no clear-cut guidelines exist about what subtype of patient CP and HP should be administered to. CASE PRESENTATION: We have reported the cases of 3 patients, all immunosuppressed and affected by non-severe, prolonged COVID-19. They were treated with HP, whose neutralizing titer was higher than 1/80. The first patient was a 55-year-old male, who had undergone lung transplant. He was under therapy with Tacrolimus and developed non-neutralizing antibodies against SARS-CoV2. The second patient was a 77-year-old female, affected by follicular lymphoma. She had tested positive for SARS-CoV2 after 6 months. The third was a 60-year-old patient, affected by chronic leukemia. He did not develop antibodies after 2-month disease. All 3 patients received HP and had tested negative for SARS-CoV2 within 2 weeks. CONCLUSION: Despite encouraging initial data, no strong evidence exist in support of CP and HP to treat COVID-19. In our experience, although limited due to the reduced number of patients, we found a good safety and efficacy of HP in 3 immuno-deficient subjects. Further data are needed in order to assess whether this subtype of patients may particularly benefit from passive immunization.

Neutralizing Antibody Response of Vaccinees to SARS-CoV-2 Variants.

Due to their increased transmissibility, three variants of high concern have emerged in the United Kingdom (also known as B.1.1.7 lineage or VOC-202012/01), South Africa (B.1.351 lineage), and Brazil (P1 lineage) with multiple substitutions in the spike protein. Since neutralizing antibodies elicited by vaccination are likely considered as correlates of protection for SARS-CoV-2 infection, it is important to analyze whether vaccinees with mRNA BNT162b2 are equally protected against these emerging SARS-CoV-2 variants. To this aim, we enrolled healthy subjects one month after complete vaccination with Comirnaty and evaluated the neutralizing response against the native Wuhan strain and the emerging B.1.1.7, B.1.351 and P1 lineages, by using the microneutralization assay, currently considered the gold standard test for the evaluation and detection of functional neutralizing antibodies. The most remarkable finding of this study was the significantly lower neutralizing antibody titer against B.1.351 lineage, compared to the wild-type virus. No significant differences were observed with the other two lineages. These findings provide evidence that vaccinated subjects may not be equally protected against all SARS-CoV-2 lineages.

How long can SARS-CoV-2 persist in human corpses?

We report the finding of the SARS-CoV-2 genome in the corpse of an exhumed infected person, one month after her death. The viral gene targets were still present in her lungs and heart, however, the virus was no longer alive. Infectious risks from human corpses should be considered.

Antibody response to SARS-CoV-2 in infected patients with different clinical outcome.

Data regarding antibody responses to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in patients infected with COVID-19 are not yet available. In this study, we aimed to evaluate serum antibody responses in patients regardless of the outcome. We measured the circulating immunoglobulin G (IgG) antibody levels in 60 subjects with a certified history of SARS-CoV-2 infection by using immunoenzymatic, chemiluminescent, and Neutralization assays. Half patients had a severe infection, the other half were pauci-symptomatic. We analyzed their antibody response to see the trend of the humoral response. Our results showed a significant difference in circulating IgG level among the two groups. The neutralizing antibody response against SARS-CoV-2 was significantly higher among those who had severe disease. Furthermore, ten subjects from each group were screened twice, and a declining antibody trend was observed in pauci-symptomatic individuals. These findings provide evidence that humoral immunity against SARS-CoV-2 in pauci-symptomatic people is weak and may not be long-lasting. This may have implications for immunity strategy and prevention, since it is still not clear whether a time-dependent decrease of both circulating and neutralizing antibodies to nonprotective levels could occur in a longer time span and whether potential vaccines are able to induce a herd immunity and a durable response.

Residual SARS-CoV-2 RNA in nasal swabs of convalescent COVID-19 patients: Is prolonged quarantine always justified?

Real-time reverse transcription PCR is currently the most sensitive method to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Defining whether a patient could be contagious or not contagious in the presence of residual SARS-CoV-2 RNA is of extreme importance in the context of public health. In this prospective multicenter study, virus isolation was prospectively attempted in 387 nasal swabs from clinically recovered patients showing low viral load (quantification cycle, Cq, value greater than 30). The median Cq value was 36.8 (range 30.0-39.4). Overall, a cytopathic effect was detected in nine samples, corresponding to a culture positivity rate of 2.3% (9/387). The results of this study help to dissect true virus replication and residual viral RNA detection in recovered patients.