Tissue protective role of Ganetespib in SARS-CoV-2-infected Syrian golden hamsters (preprint)

The emergence of new SARS-CoV-2 variants, capable of escaping the humoral immunity acquired by the available vaccines, together with waning immunity and vaccine hesitancy, challenges the efficacy of the vaccination strategy in fighting COVID-19. Improved therapeutic strategies are therefore urgently needed to better intervene particularly in severe cases of the disease. They should aim at controlling the hyper-inflammatory state generated upon infection, at reducing lung tissue pathology and endothelial damages, along with viral replication. Previous research has pointed a possible role for the chaperone HSP90 in SARS-CoV-2 replication and COVID-19 pathogenesis. Pharmacological intervention through HSP90 inhibitors was shown to be beneficial in the treatment of inflammatory diseases, infections and reducing replication of diverse viruses. In this study, we analyzed the effects of the potent HSP90 inhibitor Ganetespib in vitro on alveolar epithelial cells and alveolar macrophages to characterize its effects on cell activation and viral replication. Additionally, to evaluate its efficacy in controlling systemic inflammation and the viral burden after infection in vivo, a Syrian hamster model was used. In vitro, Ganetespib reduced viral replication on AECs in a dose-dependent manner and lowered significantly the expression of pro-inflammatory genes, in both AECs and alveolar macrophages. In vivo, administration of Ganetespib led to an overall improvement of the clinical condition of infected animals, with decreased systemic inflammation, reduced edema formation and lung tissue pathology. Altogether, we show that Ganetespib could be a potential medicine to treat moderate and severe cases of COVID-19.

Single cell RNA-seq uncovers the nuclear decoy lincRNA PIRAT as a regulator of systemic monocyte immunity during COVID-19 (preprint)

The systemic immune response to viral infection is shaped by master transcription factors such as NF{kappa}B or PU.1. Although long non-coding RNAs (lncRNAs) have been suggested as important regulators of transcription factor activity, their contributions to the systemic immunopathologies observed during SARS-CoV-2 infection have remained unknown. Here, we employed a targeted single-cell RNA-seq approach to reveal lncRNAs differentially expressed in blood leukocytes during severe COVID-19. Our results uncover the lncRNA PIRAT as a major PU.1 feedback-regulator in monocytes, governing the production of the alarmins S100A8/A9 - key drivers of COVID-19 pathogenesis. Knockout and transgene expression, combined with chromatin-occupancy profiling characterized PIRAT as a nuclear decoy RNA, diverting the PU.1 transcription factor from alarmin promoters to dead-end pseudogenes in naive monocytes. NF{kappa}B-dependent PIRAT down-regulation during COVID-19 consequently releases a transcriptional brake, fueling alarmin production. Our results suggest a major role of nuclear noncoding RNA circuits in systemic antiviral responses to SARS-CoV-2 in humans.

Human Lungs Show Limited Permissiveness for SARS-CoV-2 Due to Scarce ACE2 Levels But Strong Virus-Induced Immune Activation in Alveolar Macrophages (preprint)

SARS-CoV-2 utilizes the ACE2 transmembrane peptidase as essential cellular entry receptor. Several studies have suggested abundant ACE2 expression in the human lung, inferring strong permissiveness to SARS-CoV-2 infection with resultant alveolar damage and lung injury. Against this expectation, we provide evidence that ACE2 expression must be considered scarce, thereby limiting SARS-CoV-2 propagation in the human alveolus. Instead, spectral imaging of ex vivo infected human lungs and COVID-19 autopsy samples depicted that alveolar macrophages were frequently positive for SARS-CoV-2, indicating viral phagocytosis. Single-cell transcriptomics of SARS-CoV-2 infected human lung tissue further revealed strong inflammatory and anti-viral activation responses in macrophages and monocytes, comparable to those induced by MERS-CoV, but with virus-specific gene expression profiles. Collectively, our findings indicate that severe lung injury in COVID-19 likely results from an overwhelming immune activation rather than direct viral damage of the alveolar compartment.Funding: ACH, LES, SH were supported by Berlin University Alliance GC2 Global Health (Corona Virus Pre-Exploration Project). ACH, SH, TW and CD were supported by BMBF (RAPID) and ACH, SH by BMBF (alvBarriereCOVID-19). KH, LB, SL, SH, CD, TW, ACH were funded by BMBF (NFN-COVID 19, Organo-Strat). KH, NS, LES, MW, SH, ADG, CD, TW and ACH were supported by DFG (SFB-TR 84). ACH was supported by BIH, Charite 3R, and Charité-Zeiss MultiDim. KH was supported by BMBF (Camo-COVID-19). MW, NS and SH was supported by BMBF (PROVID). MW and NS was supported by BIH and BMBF (SYMPATH, CAPSyS, NAPKON). BO and DB were funded through the BIH Clinical Single Cell Bioinformatics Pipeline. LB was supported by the BMBF (CoIMMUNE), the DFG (KFO 342) and the IZKF of the Medical Faculty of the WWU. Conflict of Interest: The authors declare no competing interests.Ethical Approval: The study was approved by the ethics committee at the Charité clinic (projects EA2/079/13) and Ärztekammer Westfalen-Lippe and of the Westfälischen Wilhelms-Universität (AZ: 2016-265-f-S). Written informed consent was obtained from all patients.