Antiviral innate immune memory in alveolar macrophages following SARS-CoV-2 infection ameliorates secondary influenza A virus disease.

Pathogen encounter can result in epigenetic remodeling that shapes disease caused by heterologous pathogens. Here, we examined innate immune memory in the context of commonly circulating respiratory viruses. Single-cell analyses of airway-resident immune cells in a disease-relevant murine model of SARS-CoV-2 recovery revealed epigenetic reprogramming in alveolar macrophages following infection. Post-COVID-19 human monocytes exhibited similar epigenetic signatures. In airway-resident macrophages, past SARS-CoV-2 infection increased activity of type I interferon (IFN-I)-related transcription factors and epigenetic poising of antiviral genes. Viral pattern recognition and canonical IFN-I signaling were required for the establishment of this innate immune memory and augmented secondary antiviral responses. Antiviral innate immune memory mounted by airway-resident macrophages post-SARS-CoV-2 was necessary and sufficient to ameliorate secondary disease caused by influenza A virus and curtailed hyperinflammatory dysregulation and mortality. Our findings provide insights into antiviral innate immune memory in the airway that may facilitate the development of broadly effective therapeutic strategies.

A genome-wide arrayed CRISPR screen identifies PLSCR1 as an intrinsic barrier to SARS-CoV-2 entry that recent virus variants have evolved to resist.

Interferons (IFNs) play a crucial role in the regulation and evolution of host-virus interactions. Here, we conducted a genome-wide arrayed CRISPR knockout screen in the presence and absence of IFN to identify human genes that influence Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection. We then performed an integrated analysis of genes interacting with SARS-CoV-2, drawing from a selection of 67 large-scale studies, including our own. We identified 28 genes of high relevance in both human genetic studies of Coronavirus Disease 2019 (COVID-19) patients and functional genetic screens in cell culture, with many related to the IFN pathway. Among these was the IFN-stimulated gene PLSCR1. PLSCR1 did not require IFN induction to restrict SARS-CoV-2 and did not contribute to IFN signaling. Instead, PLSCR1 specifically restricted spike-mediated SARS-CoV-2 entry. The PLSCR1-mediated restriction was alleviated by TMPRSS2 overexpression, suggesting that PLSCR1 primarily restricts the endocytic entry route. In addition, recent SARS-CoV-2 variants have adapted to circumvent the PLSCR1 barrier via currently undetermined mechanisms. Finally, we investigate the functional effects of PLSCR1 variants present in humans and discuss an association between PLSCR1 and severe COVID-19 reported recently.

BiP: Master Regulator of the Unfolded Protein Response and Crucial Factor in Flavivirus Biology
.

Flaviviruses have an intimate relationship with their host cells, utilizing host proteins during replication. Much of viral genome replication and virion assembly occurs on and within the endoplasmic reticulum (ER). As a cellular protein folding hub, the ER provides an ideal environment for flaviviruses to replicate. Flaviviruses can interact with several ER processes, including the unfolded protein response (UPR), a cellular stress mechanism responsible for managing unfolded protein accumulation and ER stress. The UPR can alter the ER environment in several ways, including increasing ER volume and quantity of available chaperones, both of which can favor viral replication. BiP, a chaperone and master regulator of the UPR, has been demonstrated to play a key role in several flavivirus infections. Here we describe what is known in regard to BiP, its implicated role with flavivirus infection, and what remains to be discovered.

Spatial omics technologies at multimodal and single cell/subcellular level.

Spatial omics technologies enable a deeper understanding of cellular organizations and interactions within a tissue of interest. These assays can identify specific compartments or regions in a tissue with differential transcript or protein abundance, delineate their interactions, and complement other methods in defining cellular phenotypes. A variety of spatial methodologies are being developed and commercialized; however, these techniques differ in spatial resolution, multiplexing capability, scale/throughput, and coverage. Here, we review the current and prospective landscape of single cell to subcellular resolution spatial omics technologies and analysis tools to provide a comprehensive picture for both research and clinical applications.

PERK-Mediated Unfolded Protein Response Signaling Restricts Replication of the Tick-Borne Flavivirus Langat Virus.

The unfolded protein response (UPR) maintains protein-folding homeostasis in the endoplasmic reticulum (ER) and has been implicated as both beneficial and detrimental to flavivirus infection. Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), a sensor of the UPR, is commonly associated with antiviral effects during mosquito-borne flavivirus (MBFV) infection, but its relation to tick-borne flavivirus (TBFV) infection remains largely unexplored. In this study, we identified changes in UPR and autophagic activity during Langat virus (LGTV) infection. LGTV robustly activated UPR and altered autophagic flux. Knockdown of endogenous PERK in human cells resulted in increased LGTV replication, but not that of closely related Powassan virus (POWV). Finally, on examining changes in protein levels of components associated with UPR and autophagy in the absence of PERK, we could show that LGTV-infected cells induced UPR but did not lead to expression of C/EBP homologous protein (CHOP), an important downstream transcription factor of multiple stress pathways. From these data, we hypothesize that LGTV can antagonize other kinases that target eukaryotic initiation factor 2α (eIF2α), but not PERK, implicating PERK as a potential mediator of intrinsic immunity. This effect was not apparent for POWV, a more pathogenic TBFV, suggesting it may be better equipped to mitigate the antiviral effects of PERK.

Oral Microbiome in HIV-Infected Women: Shifts in the Abundance of Pathogenic and Beneficial Bacteria Are Associated with Aging, HIV Load, CD4 Count, and Antiretroviral Therapy.

Human immunodeficiency virus (HIV)-associated nonacquired immunodeficiency syndrome (AIDS) conditions, such as cardiovascular disease, diabetes, osteoporosis, and dementia are more prevalent in older than in young adult HIV-infected subjects. Although the oral microbiome has been studied as a window into pathogenesis in aging populations, its relationship to HIV disease progression, opportunistic infections, and HIV-associated non-AIDS conditions is not well understood. We utilized 16S rDNA-based pyrosequencing to compare the salivary microbiome in three groups: (1) Chronically HIV-infected women >50 years of age (aging); (2) HIV-infected women <35 years of age (young adult); and (3) HIV-uninfected age-matched women. We also examined correlations between salivary dysbiosis, plasma HIV RNA, CD4+ T cell depletion, and opportunistic oral infections. In both aging and young adult women, HIV infection was associated with salivary dysbiosis characterized by increased abundance of Prevotella melaninogenica and Rothia mucilaginosa. Aging was associated with increased bacterial diversity in both uninfected and HIV-infected women. In HIV-infected women with oral coinfections, aging was also associated with reduced abundance of the common commensal Veillonella parvula. Patients taking antiretroviral therapy showed increased numbers of Neisseria and Haemophilus. High plasma HIV RNA levels correlated positively with the presence of Prevotella and Veillonella, and negatively with the abundance of potentially beneficial Streptococcus and Lactobacillus. Circulating CD4+ T cell numbers correlated positively with the abundance of Streptococcus and Lactobacillus. Our findings extend previous studies of the role of the microbiome in HIV pathogenesis, providing new evidence that HIV infection is associated with a shift toward an increased pathogenic footprint of the salivary microbiome. Taken together, the data suggest a complex relationship, worthy of additional study, between chronic dysbiosis in the oral cavity, aging, viral burden, CD4+ T cell depletion, and long-term antiretroviral therapy.