The DNA glycosylase NEIL2 plays a vital role in combating SARS-CoV-2 infection (preprint)

Compromised DNA repair capacity of individuals could play a critical role in the severity of SARS-CoV-2 infection-induced COVID-19. We therefore analyzed the expression of DNA repair genes in publicly available transcriptomic datasets of COVID-19 patients and found that the level of NEIL2, an oxidized base specific mammalian DNA glycosylase, is particularly low in the lungs of COVID-19 patients displaying severe symptoms. Downregulation of pulmonary NEIL2 in CoV-2-permissive animals and postmortem COVID-19 patients validated these results. To investigate the potential roles of NEIL2 in CoV-2 pathogenesis, we infected Neil2-null (Neil2−/−) mice with a mouse-adapted CoV-2 strain and found that Neil2−/− mice suffered more severe viral infection concomitant with increased expression of proinflammatory genes, which resulted in an enhanced mortality rate of 80%, up from 20% for the age matched Neil2+/+ cohorts. We also found that infected animals accumulated a significant amount of damage in their lung DNA. Surprisingly, recombinant NEIL2 delivered into permissive A549-ACE2 cells significantly decreased viral replication. Toward better understanding the mechanistic basis of how NEIL2 plays such a protective role against CoV-2 infection, we determined that NEIL2 specifically binds to the 5’-UTR of SARS-CoV-2 genomic RNA and blocks protein synthesis. Together, our data suggest that NEIL2 plays a previously unidentified role in regulating CoV-2-induced pathogenesis, via inhibiting viral replication and preventing exacerbated proinflammatory responses, and also via its well-established role of repairing host genome damage.

COVID-19 lung disease shares driver AT2 cytopathic features with Idiopathic pulmonary fibrosis (preprint)

Background: In the aftermath of Covid-19, a long-haul form of mysterious and progressive fibrotic lung disease has emerged, i.e., post-COVID-19 lung disease (PCLD), for which we currently lack insights into pathogenesis, disease models, or treatment options. Method: Using an AI-guided approach, we analyzed > 1000 human lung transcriptomic datasets associated with various lung conditions using two viral pandemic (ViP and sViP) and one covid lung gene signatures. Upon identifying similarities between COVID-19 and idiopathic pulmonary fibrosis (IPF), we subsequently dissected the basis for such similarity from molecular, cytopathic, and immunologic perspectives using a panel of IPF-specific gene signatures, alongside signatures of alveolar type II (AT2) cytopathies and of prognostic monocyte-driven processes that are known drivers of IPF. To pinpoint the AT2 processes that are shared points of convergence between COVID-19 and IPF, transcriptome-derived findings were used to construct protein-protein interaction (PPI) network. Key findings were validated in hamster and human adult lung organoid (ALO) pre-clinical models of COVID-19 using immunohistochemistry and qPCR. Findings: We found that COVID-19 resembles IPF at a fundamental level; it recapitulates the gene expression patterns (ViP and IPF signatures), cytokine storm (IL15-centric) and the AT2 cytopathic changes, e.g., injury, DNA damage, arrest in a transient, damage-induced progenitor state, and senescence-associated secretory phenotype (SASP). These immunocytopathic features were induced in pre-clinical COVID models (ALO and hamster) and reversed with effective anti-CoV-2 therapeutics in hamsters. PPI-network analyses pinpointed ER stress as one of the shared early triggers of both diseases, and IHC studies validated the same in the lungs of deceased subjects with COVID-19 and SARS-CoV-2-challenged hamster lungs. Lungs from tg-mice, in which ER stress is induced specifically in the AT2 cells, faithfully recapitulate the host immune response and alveolar cytopathic changes that are induced by SARS-CoV-2. Interpretation: Like IPF, COVID-19 may be driven by injury-induced ER stress that culminates into progenitor state arrest and SASP in AT2 cells. The ViP signatures in monocytes may be key determinants of prognosis. The insights, signatures, disease models identified here are likely to spur the development of therapies for patients with IPF and other fibrotic interstitial lung disease.

An AI-guided invariant signature places MIS-C with Kawasaki disease in a continuum of host immune responses (preprint)

A significant surge in cases of multisystem inflammatory syndrome in children (MIS-C, also called Pediatric Inflammatory Multisystem Syndrome - PIMS) has been observed amidst the COVID-19 pandemic. MIS-C shares many clinical features with Kawasaki disease (KD), although clinical course and outcomes are divergent. We analyzed whole blood RNA sequences, serum cytokines, and formalin fixed heart tissues from these patients using a computational toolbox of two gene signatures, i.e., the 166-gene viral pandemic (ViP) signature, and its 20-gene severe (s)ViP subset that were developed in the context of SARS-CoV-2 infection and a 13-transcript signature previously demonstrated to be diagnostic for KD. Our analyses revealed that KD and MIS-C are on the same continuum of the host immune response as COVID-19 but diverge with two different cardiac phenotypes. The ViP signatures helped unravel the nature of the host immune response (IL15-centric) in MIS-C and KD, reveal unique targetable cytokine pathways in MIS-C, place MIS-C farther along in the spectrum in severity compared to KD and pinpoint key clinical (reduced cardiac function) and laboratory (thrombocytopenia and eosinopenia) parameters that can be useful to monitor severity.

Adult Stem Cell-derived Complete Lung Organoid Models Emulate Lung Disease in COVID-19 (preprint)

SARS-CoV-2, the virus responsible for COVID-19, causes widespread damage in the lungs in the setting of an overzealous immune response whose origin remains unclear. We present a scalable, propagable, personalized, cost-effective adult stem cell-derived human lung organoid model that is complete with both proximal and distal airway epithelia. Monolayers derived from adult lung organoids (ALOs), primary airway cells, or hiPSC-derived alveolar type-II (AT2) pneumocytes were infected with SARS-CoV-2 to create in vitro lung models of COVID-19. Infected ALO-monolayers best recapitulated the transcriptomic signatures in diverse cohorts of COVID-19 patient-derived respiratory samples. The airway (proximal) cells were critical for sustained viral infection whereas distal alveolar differentiation (AT2[->]AT1) was critical for mounting the overzealous host immune response in fatal disease; ALO monolayers with well-mixed proximodistal airway components recapitulated both. Findings validate a human lung model of COVID-19 which can be immediately utilized to investigate COVID-19 pathogenesis, and vet new therapies and vaccines.

Molecular mechanism of SARS-CoV-2 inactivation by temperature (preprint)

Recent studies have shown that SARS-CoV-2 virus can be inactivated by effect of heat, even though, little is known about the molecular changes induced by the temperature. Here, we unravel the basics of such inactivation mechanism over the SARS-CoV-2 spike glycoprotein by executing atomistic molecular dynamics simulations. Both the closed down and open up states, which determine the accessibility to the receptor binding domain, were considered. Results suggest that the spike undergoes drastic changes in the topology of the hydrogen bond network while salt bridges are mainly preserved. Reorganization in the hydrogen bonds structure produces conformational variations in the receptor binding subunit and explain the thermal inactivation of the virus. Conversely, the macrostructure of the spike is preserved at high temperature because of the retained salt bridges. The proposed mechanism has important implications for engineering new approaches to inactivate the SARS-CoV-2 virus.

AI-guided discovery of the invariant host response to viral pandemics (preprint)

We sought to define the host immune response, a.k.a, the cytokine storm that has been implicated in fatal COVID-19 using an AI-based approach. Over 45,000 transcriptomic datasets of viral pandemics were analyzed to extract a 166-gene signature using ACE2 as a seed gene; ACE2 was rationalized because it encodes the receptor that facilitates the entry of SARS-CoV-2 (the virus that causes COVID-19) into host cells. Surprisingly, this 166-gene signature was conserved in all viral pandemics, including COVID-19, and a subset of 20-genes classified disease severity, inspiring the nomenclatures ViPand severe-ViPsignatures, respectively. The ViPsignatures pinpointed a paradoxical phenomenon wherein lung epithelial and myeloid cells mount an IL15 cytokine storm, and epithelial and NK cell senescence and apoptosis determines severity/fatality. Precise therapeutic goals were formulated and subsequently validated in high-dose SARS-CoV-2-challenged hamsters using neutralizing antibodies that abrogate SARS-CoV-2/ACE2 engagement. IL15/IL15RA were elevated in the lungs of patients with fatal disease, and plasma levels of the cytokine tracked with disease severity. Thus, the ViP signatures provide a quantitative and qualitative framework for titrating the immune response in viral pandemics and may serve as a powerful unbiased tool to rapidly assess disease severity and vet candidate drugs.