The dysregulation of host signaling pathways plays a critical role in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and viral pathogenesis. While a number of viral proteins that can block type I IFN signaling have been identified, a comprehensive analysis of SARS-CoV-2 proteins in the regulation of other signaling pathways that can be critical for viral infection and its pathophysiology is still lacking. Here, we screened the effect of 21 SARS-CoV-2 proteins on 10 different host signaling pathways, namely, Wnt, p53, TGFβ, c-Myc, Hypoxia, Hippo, AP-1, Notch, Oct4/Sox2, and NF-κB, using a luciferase reporter assay. As a result, we identified several SARS-CoV-2 proteins that could act as activators or inhibitors for distinct signaling pathways in the context of overexpression in HEK293T cells. We also provided evidence for p53 being an intrinsic host restriction factor of SARS-CoV-2. We found that the overexpression of p53 is capable of reducing virus production, while the main viral protease nsp5 can repress the transcriptional activity of p53, which depends on the protease function of nsp5. Taken together, our results provide a foundation for future studies, which can explore how the dysregulation of specific signaling pathways by SARS-CoV-2 proteins can control viral infection and pathogenesis.

Bacteria are able to adapt and survive in harsh and changing environments through many mechanisms, with one of them being horizontal gene transfer (HGT). This process is one of the leading culprits in the spread of antimicrobial resistance (AMR) within bacterial communities and could pose a significant health threat to astronauts if they fell ill, especially on long-duration space missions. In order to better understand the degree of HGT activity that could occur in space, biosafety level-2, donor and recipient bacteria were co-cultured under simulated microgravity (SMG) on Earth with concomitant 1G controls. Two AMR genes, blaOXA-500 and ISAba1, from the donor Acinetobacter pittii, were tracked in four recipient strains of Staphylococcus aureus (which did not harbor those genes) using polymerase chain reaction. All four S. aureus strains that were co-cultured with A. pittii under SMG had a significantly higher number of isolates that were now blaOXA-500- and ISAba1-positive compared to growth at 1G. The acquisition of these genes by the recipient induced a phenotypic change, as these isolates were now resistant to oxacillin, which they were previously susceptible to. This is a novel study, presenting, for the first time, increased HGT activity under SMG and the potential impact of the space environment in promoting increased gene dissemination within bacterial communities.

Suppressors of Cytokine Signaling (SOCS) are intracellular proteins that negatively regulate the induction of cytokines. Amongst these, SOCS1 and SOCS3 are particularly involved in inhibition of various interferons. Several viruses have hijacked this regulatory pathway: by inducing SOCS1and 3 early in infection, they suppress the host immune response. Within the cell, SOCS1/3 binds and inhibits tyrosine kinases, such as JAK2 and TYK2. We have developed a cell penetrating peptide from the activation loop of the tyrosine kinase, JAK2 (residues 1001-1013), denoted as pJAK2 that acts as a decoy and suppresses SOCS1 and 3 activity. This peptide thereby protects against several viruses in cell culture and mouse models. Herein, we show that treatment with pJAK2 inhibited the replication and release of the beta coronavirus HuCoV-OC43 and reduced production of the viral RNA, as measured by RT-qPCR, Western blot and by immunohistochemistry. We confirmed induction of SOCS1 and 3 in rhabdomyosarcoma (RD) cells, and this induction was suppressed by pJAK2 peptide. A peptide derived from the C-terminus of IFNα (IFNα-C) also inhibited replication of OC43. Furthermore, IFNα-C plus pJAK2 provided more potent inhibition than either peptide alone. To extend this study to a pandemic beta-coronavirus, we determined that treatment of cells with pJAK2 inhibited replication and release of SARS-CoV-2 in Calu-3 cells. We propose that these peptides offer a new approach to therapy against the rapidly evolving strains of beta-coronaviruses.

Herpes simplex virus 1 (HSV-1) establishes a lifelong latent infection in peripheral nerve ganglia. Periodically, the virus reactivates from this latent reservoir and is transported to the original site of infection. Strains of HSV-1 have been noted to vary greatly in their virulence and reactivation efficiencies in animal models. While HSV-1 strain 17syn+ can be readily reactivated, strain KOS(M) shows little to no reactivation in the mouse and rabbit models of induced reactivation. Additionally, 17syn+ is markedly more virulent in vivo than KOS. This has raised questions regarding potential strain-specific differences in neuroinvasion and neurovirulence and their contribution to differences in the establishment of latency (or ability to spread back to the periphery) and to the reactivation phenotype. To determine if any difference in the ability to reactivate between strains 17syn+ and KOS(M) is manifest at the level of neurons, we utilized a recently characterized human neuronal cell line model of HSV latency and reactivation (LUHMES). We found that KOS(M) established latency with a higher number of viral genomes than strain 17syn+. Strikingly, we show that the KOS(M) viral genomes have a higher burden of heterochromatin marks than strain 17syn+. The increased heterochromatin profile for KOS(M) correlates with the reduced expression of viral lytic transcripts during latency and impaired induced reactivation compared to that of 17syn+. These results suggest that genomes entering neurons from HSV-1 infections with strain KOS(M) are more prone to rapid heterochromatinization than those of 17syn+ and that this results in a reduced ability to reactivate from latency. IMPORTANCE Herpes simplex virus 1 (HSV-1) establishes a lifelong infection in neuronal cells. The virus periodically reactivates and causes recurrent disease. Strains of HSV-1 vary greatly in their virulence and potential to reactivate in animal models. Although these differences are phenotypically well defined, factors contributing to the strains’ abilities to reactivate are largely unknown. We utilized a human neuronal cell line model of HSV latency and reactivation (LUHMES) to characterize the latent infection of two HSV-1 wild-type strains. We find that strain-specific differences in reactivation are recapitulated in LUHMES. Additionally, these differences correlate with the degree of heterochromatinization of the latent genomes. Our data suggest that the epigenetic state of the viral genome is an important determinant of reactivation that varies in a strain-specific manner. This work also shows the first evidence of strain-specific differences in reactivation outside the context of the whole animal at a human neuronal cell level.