Pharmacological inhibition of bromodomain and extra-terminal proteins induces NRF-2-mediated inhibition of SARS-CoV-2 replication and is subject to viral antagonism (preprint)

Inhibitors of bromodomain and extra-terminal proteins (iBETs), including JQ-1, have been suggested as potential therapeutics against SARS-CoV-2 infection. However, molecular mechanisms underlying JQ-1-induced antiviral activity and its susceptibility to viral antagonism remain incompletely understood. iBET treatment transiently inhibited infection by SARS-CoV-2 variants and SARS-CoV, but not MERS-CoV. Our functional assays confirmed JQ-1-mediated downregulation of ACE2 expression and multi-omics analysis uncovered induction of an antiviral NRF-2-mediated cytoprotective response as an additional antiviral component of JQ-1 treatment. Serial passaging of SARS-CoV-2 in the presence of JQ-1 resulted in predominance of ORF6-deficient variants. JQ-1 antiviral activity was transient in human bronchial airway epithelial cells (hBAECs) treated prior to infection and absent when administered therapeutically. We propose that JQ-1 exerts pleiotropic effects that collectively induce a transient antiviral state that is ultimately nullified by an established SARS-CoV-2 infection, raising questions on their clinical suitability in the context of COVID-19.

Post-entry, spike-dependent replication advantage of B.1.1.7 and B.1.617.2 over B.1 SARS-CoV-2 in an ACE2-deficient human lung cell line (preprint)

Epidemiological data demonstrate that B.1.1.7, and even more, B.1.617.2 SARS-CoV-2 are more transmissible and infections are associated with a higher mortality than B.1 virus infection. Intrinsic properties underlying their enhanced spread in the human population remain unknown. B.1.1.7 virus isolates displayed inferior or equivalent spread in most cell lines and primary cells compared to B.1 SARS-CoV-2, and were outcompeted by the latter. Lower infectivity and delayed entry kinetics of B.1.1.7 viruses were accompanied by inefficient proteolytic processing of spike. B.1.1.7 viruses failed to escape from neutralizing antibodies, but slightly dampened induction of innate immunity. The lung cell line NCI-H1299 supported 24- and 595-fold increased growth of B.1.1.7 and B.1.617.2 viruses, respectively, in the absence of detectable ACE2 expression and in a spike-determined fashion. Superior spread in ACE2-deficient NCI-H1299 cells suggests that variants of concern employ a distinct set of cellular cofactors that may be unavailable in standard cell culture lines.

IFITM proteins promote SARS-CoV-2 infection in human lung cells (preprint)

Interferon-induced transmembrane proteins (IFITMs 1, 2 and 3) restrict numerous viral pathogens and are thought to prevent infection by severe acute respiratory syndrome coronaviruses (SARS-CoVs). However, most evidence comes from single-round pseudoparticle infection of cells artificially overexpressing IFITMs. Here, we confirmed that overexpression of IFITMs blocks pseudoparticle infections mediated by the Spike proteins of {beta}-coronaviruses including pandemic SARS-CoV-2. In striking contrast, however, endogenous IFITM expression promoted genuine SARS-CoV-2 infection in human lung cells both in the presence and absence of interferon. IFITM2 was most critical for efficient entry of SARS-CoV-2 and enhanced virus production from Calu-3 cells by several orders of magnitude. IFITMs are expressed and further induced by interferons in the lung representing the primary site of SARS-CoV-2 infection as well as in other relevant tissues. Our finding that IFITMs enhance SARS-CoV-2 infection under conditions approximating the in vivo situation shows that they may promote viral invasion during COVID-19. HIGHLIGHTSO_LIOverexpression of IFITM1, 2 and 3 restricts SARS-CoV-2 infection C_LIO_LIEndogenous IFITM1, 2 and 3 boost SARS-CoV-2 infection of human lung cells C_LIO_LIIFITM2 is critical for efficient entry of SARS-CoV-2 in Calu-3 cells C_LI

Seeding of outbreaks of COVID-19 by contaminated fresh and frozen food (preprint)

An explanation is required for the re-emergence of COVID-19 outbreaks in regions with apparent local eradication. Recent outbreaks have emerged in Vietnam, New Zealand and parts of China where there had been no cases for some months. Importation of contaminated food and food packaging is a feasible source for such outbreaks and a source of clusters within existing outbreaks. Such events can be prevented if the risk is better appreciated.

SARS-CoV-2 Infection and Transmission Depends on Heparan Sulfates and Is Blocked by Low Molecular Weight Heparins (preprint)

The current pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and new outbreaks worldwide highlight the need for preventive treatments. Although angiotensin converting enzyme 2 (ACE2) is the primary receptor for SARS-CoV-2, we identified heparan sulfate proteoglycans expressed by epithelial cells, alveolar macrophages and dendritic cells as co-receptors for SARS-CoV-2. Low molecular weight heparins (LMWH) blocked SARS-CoV-2 infection of epithelial cells and alveolar macrophages, and virus dissemination by dendritic cells. Notably, potent neutralizing antibodies from COVID-19 patients interfered with SARS-CoV-2 binding to heparan sulfate proteoglycans, underscoring the importance of heparan sulfate proteoglycans as receptors and uncover that SARS-CoV-2 binding to heparan sulfates is an important mechanism for neutralization. These results have imperative implications for our understanding of SARS-CoV-2 host cell entry and reveal an important target for novel prophylactic intervention.