Valproate-coenzyme A conjugate blocks opening of receptor binding domains in the spike trimer of SARS-CoV-2 through an allosteric mechanism.

The receptor-binding domains (RBDs) of the SARS-CoV-2 spike trimer exhibit "up" and "down" conformations often targeted by neutralizing antibodies. Only in the "up" configuration can RBDs bind to the ACE2 receptor of the host cell and initiate the process of viral multiplication. Here, we identify a lead compound (3-oxo-valproate-coenzyme A conjugate or Val-CoA) that stabilizes the spike trimer with RBDs in the down conformation. Val-CoA interacts with three R408 residues, one from each RBD, which significantly reduces the inter-subunit R408-R408 distance by ∼ 13 Å and closes the central pore formed by the three RBDs. Experimental evidence is presented that R408 is part of a triggering mechanism that controls the prefusion to postfusion state transition of the spike trimer. By stabilizing the RBDs in the down configuration, this and other related compounds can likely attenuate viral transmission. The reported findings for binding of Val-CoA to the spike trimer suggest a new approach for the design of allosteric antiviral drugs that do not have to compete for specific virus-receptor interactions but instead hinder the conformational motion of viral membrane proteins essential for interaction with the host cell. Here, we introduce an approach to target the spike protein by identifying lead compounds that stabilize the RBDs in the trimeric "down" configuration. When these compounds trimerize monomeric RBD immunogens as co-immunogens, they could also induce new types of non-ACE2 blocking antibodies that prevent local cell-to-cell transmission of the virus, providing a novel approach for inhibition of SARS-CoV-2.

Predictors of professional burnout and fulfilment in a longitudinal analysis on nurses and healthcare workers in the COVID-19 pandemic.

AIMS AND OBJECTIVES: (1) To investigate the vulnerability of nurses to experiencing professional burnout and low fulfilment across 5 months of the COVID-19 pandemic. (2) To identify modifiable variables in hospital leadership and individual vulnerabilities that may mitigate these effects. BACKGROUND: Nurses were at increased risk for burnout and low fulfilment prior to the COVID-19 pandemic. Hospital leadership factors such as organisational structure and open communication and consideration of employee opinions are known to have positive impacts on work attitudes. Personal risk factors for burnout include symptoms of depression and anxiety. METHODS: Healthcare workers (n = 406 at baseline, n = 234 longitudinal), including doctors (n = 102), nurses (n = 94), technicians (n = 90) and non-clinical administrative staff (n = 120), completed 5 online questionnaires, once per month, for 5 months. Participants completed self-report questionnaires on professional fulfilment and burnout, perceptions of healthcare leadership, and symptoms of anxiety and depression. Participants were recruited from various healthcare settings in the southeastern United States. The STROBE checklist was used to report the present study. RESULTS: Both at baseline and across the 5 months, nurses working during the COVID-19 pandemic reported increased burnout and decreased fulfilment relative to doctors. For all participants, burnout remained largely steady and fulfilment decreased slightly. The strongest predictors of both burnout and fulfilment were organisational structure and depressive symptoms. Leadership consideration and anxiety symptoms had smaller, yet significant, relationships to burnout and fulfilment in longitudinal analyses. CONCLUSIONS: Burnout and reduced fulfilment remain a problem for healthcare workers, especially nurses. Leadership styles and employee symptoms of depression and anxiety are appropriate targets for intervention. RELEVANCE TO CLINICAL PRACTICE: Leadership wishing to reduce burnout and increase fulfilment among employees should increase levels of organisational support and consideration and expand supports to employees seeking treatment for depression and anxiety.

Insights into Binding of Single-Stranded Viral RNA Template to the Replication-Transcription Complex of SARS-CoV-2 for the Priming Reaction from Molecular Dynamics Simulations.

A minimal replication-transcription complex (RTC) of SARS-CoV-2 for synthesis of viral RNAs includes the nsp12 RNA-dependent RNA polymerase and two nsp8 RNA primase subunits for de novo primer synthesis, one nsp8 in complex with its accessory nsp7 subunit and the other without it. The RTC is responsible for faithfully copying the entire (+) sense viral genome from its first 5'-end to the last 3'-end nucleotides through a replication-intermediate (RI) template. The single-stranded (ss) RNA template for the RI is its 33-nucleotide 3'-poly(A) tail adjacent to a well-characterized secondary structure. The ssRNA template for viral transcription is a 5'-UUUAU-3' next to stem-loop (SL) 1'. We analyze the electrostatic potential distribution of the nsp8 subunit within the RTC around the template strand of the primer/template (P/T) RNA duplex in recently published cryo-EM structures to address the priming reaction using the viral poly(A) template. We carried out molecular dynamics (MD) simulations with a P/T RNA duplex, the viral poly(A) template, or a generic ssRNA template. We find evidence that the viral poly(A) template binds similarly to the template strand of the P/T RNA duplex within the RTC, mainly through electrostatic interactions, providing new insights into the priming reaction by the nsp8 subunit within the RTC, which differs significantly from the existing proposal of the nsp7/nsp8 oligomer formed outside the RTC. High-order oligomerization of nsp8 and nsp7 for SARS-CoV observed outside the RTC of SARS-CoV-2 is not found in the RTC and not likely to be relevant to the priming reaction.

Morally Distressing Experiences, Moral Injury, and Burnout in Florida Healthcare Providers during the COVID-19 Pandemic.

Because healthcare providers may be experiencing moral injury (MI), we inquired about their healthcare morally distressing experiences (HMDEs), MI perpetrated by self (Self MI) or others (Others MI), and burnout during the COVID-19 pandemic. Participants were 265 healthcare providers in North Central Florida (81.9% female, Mage = 37.62) recruited via flyers and emailed brochures that completed online surveys monthly for four months. Logistic regression analyses investigated whether MI was associated with specific HMDEs, risk factors (demographic characteristics, prior mental/medical health adversity, COVID-19 protection concern, health worry, and work impact), protective factors (personal resilience and leadership support), and psychiatric symptomatology (depression, anxiety, and PTSD). Linear regression analyses explored how Self/Others MI, psychiatric symptomatology, and the risk/protective factors related to burnout. We found consistently high rates of MI and burnout, and that both Self and Others MI were associated with specific HMDEs, COVID-19 work impact, COVID-19 protection concern, and leadership support. Others MI was also related to prior adversity, nurse role, COVID-19 health worry, and COVID-19 diagnosis. Predictors of burnout included Self MI, depression symptoms, COVID-19 work impact, and leadership support. Hospital administrators/supervisors should recognize the importance of supporting the HCPs they supervise, particularly those at greatest risk of MI and burnout.

Computational insights into the membrane fusion mechanism of SARS-CoV-2 at the cellular level.

The membrane fusion mechanism of SARS-CoV-2 offers an attractive target for the development of small molecule antiviral inhibitors. Fusion involves an initial binding of the crown-like trimeric spike glycoproteins of SARS-CoV-2 to the receptor angiotensin II-converting enzyme 2 (ACE2) on the permissive host cellular membrane and a prefusion to post-fusion conversion of the spike trimer. During this conversion, the fusion peptides of the spike trimer are inserted into the host membrane to bring together the host and viral membranes for membrane fusion in highly choreographic events. However, geometric constraints due to interactions with the membranes remain poorly understood. In this study, we build structural models of super-complexes of spike trimer/ACE2 dimers based on the molecular structures of the ACE2/neutral amino acid transporter B(0)AT heterodimer. We determine the conformational constraints due to the membrane geometry on the enzymatic activity of ACE2 and on the viral fusion process. Furthermore, we find that binding three ACE2 dimers per spike trimer is essential to open the central pore as necessary for triggering productive membrane fusion through an elongation of the central stalk. The reported findings thus provide valuable insights for targeting the membrane fusion mechanism for drug design at the molecular level.