bims-mevinf 2023-07-23 papers

Front Microbiol. 2023 ;14 1178005

Cholesterol 25-hydroxylase suppresses avian reovirus replication by its enzymatic product 25-hydroxycholesterol.

Yuyang Wang, Wei Zuo, Yangyang Zhang, Zongyi Bo, Chengcheng Zhang, Xiaorong Zhang, Yantao Wu.

Avian reovirus (ARV) causing viral arthritis/tenosynovitis and viral enteritis in domestic fowl has significantly threatened on the poultry industry worldwide. ARV is a non-enveloped fusogenic virus that belongs to the Reoviridae family. Previous research revealed that cellular cholesterol in lipid rafts is essential for ARV replication. It has been reported that cholesterol 25-hydroxylase (CH25H) and its product 25-hydroxycholesterol (25HC) have antiviral activities against enveloped viruses. However, few studies characterized the association of non-enveloped viruses with CH25H and the role of CH25H in the regulation of ARV replication. In this study, the expression of chicken CH25H (chCH25H) was found to be upregulated in ARV-infected cells at the early stage of infection. The results of overexpression and knockdown assays revealed that chCH25H has a significant antiviral effect against ARV infection. Furthermore, a 25HC treatment significantly inhibited ARV replication in a dose-dependent manner at both the entry and post-entry stages, and a chCH25H mutant lacking hydroxylase activity failed to inhibit ARV infection. These results indicate that CH25H, depending on its enzyme activity, exerts the antiviral effect against ARV via the synthesis of 25HC. In addition, we revealed that 25HC produced by CH25H inhibits viral entry by delaying the kinetics of ARV uncoating, and CH25H blocks cell-cell membrane fusion induced by the p10 protein of ARV. Altogether, our findings showed that CH25H, as a natural host restriction factor, possessed antiviral activity against ARV targeting viral entry and syncytium formation, through an enzyme activity-dependent way. This study may provide new insights into the development of broad-spectrum antiviral therapies.

Keywords: 25-hydroxycholesterol; avian reovirus; cholesterol 25-hydroxylase; interferon stimulated genes (ISG); virus replication

DOI: https://doi.org/10.3389/fmicb.2023.1178005

Front Immunol. 2023 ;14 1158455

SARS-CoV-2 infection dysregulates NAD metabolism.

Amin Izadpanah, Joseph C Mudd, Joe G N Garcia, Sudesh Srivastav, Mohamed Abdel-Mohsen, Clovis Palmer, Aaron R Goldman, Jay K Kolls, Xuebin Qin, Jay Rappaport.

Introduction: Severe COVID-19 results initially in pulmonary infection and inflammation. Symptoms can persist beyond the period of acute infection, and patients with Post-Acute Sequelae of COVID (PASC) often exhibit a variety of symptoms weeks or months following acute phase resolution including continued pulmonary dysfunction, fatigue, and neurocognitive abnormalities. We hypothesized that dysregulated NAD metabolism contributes to these abnormalities.
Methods: RNAsequencing of lungs from transgenic mice expressing human ACE2 (K18-hACE2) challenged with SARS-CoV-2 revealed upregulation of NAD biosynthetic enzymes, including NAPRT1, NMNAT1, NAMPT, and IDO1 6 days post-infection.
Results: Our data also demonstrate increased gene expression of NAD consuming enzymes: PARP 9,10,14 and CD38. At the same time, SIRT1, a protein deacetylase (requiring NAD as a cofactor and involved in control of inflammation) is downregulated. We confirmed our findings by mining sequencing data from lungs of patients that died from SARS-CoV-2 infection. Our validated findings demonstrating increased NAD turnover in SARS-CoV-2 infection suggested that modulating NAD pathways may alter disease progression and may offer therapeutic benefits. Specifically, we hypothesized that treating K18-hACE2 mice with nicotinamide riboside (NR), a potent NAD precursor, may mitigate lethality and improve recovery from SARS-CoV-2 infection. We also tested the therapeutic potential of an anti- monomeric NAMPT antibody using the same infection model. Treatment with high dose anti-NAMPT antibody resulted in significantly decreased body weight compared to control, which was mitigated by combining HD anti-NAMPT antibody with NR. We observed a significant increase in lipid metabolites, including eicosadienoic acid, oleic acid, and palmitoyl carnitine in the low dose antibody + NR group. We also observed significantly increased nicotinamide related metabolites in NR treated animals.
Discussion: Our data suggest that infection perturbs NAD pathways, identify novel mechanisms that may explain some pathophysiology of CoVID-19 and suggest novel strategies for both treatment and prevention.

Keywords: COVID-19; NAD; NAMPT; PASC; metabolism; sirtuins

DOI: https://doi.org/10.3389/fimmu.2023.1158455

Trends Microbiol. 2023 Jul 13. pii: S0966-842X(23)00195-6. [Epub ahead of print]

Plant reoviruses hijack autophagy in insect vectors.

Wenwen Liu, Taiyun Wei, Xifeng Wang.

Plant reoviruses, transmitted only by insect vectors, seriously threaten global cereal production. Understanding how insect vectors efficiently transmit the viruses is key to controlling the viral diseases. Autophagy commonly plays important roles in plant host defense against virus infection, but recent studies have shown that plant reoviruses can hijack the autophagy pathway in insect cells to enable their persistence in the insect and continued transmission to plants. Here, we summarize and discuss new insights on viral activation, evasion, regulation, and manipulation of autophagy within the insect vectors and the role of autophagy in virus survival in insect vectors. Deeper knowledge of the functions of autophagy in vectors may lead to novel strategies for blocking transmission of insect-borne plant viruses.

Keywords: autophagic pathway; insect transmission; manipulation; mitophagy; plant reoviruses

DOI: https://doi.org/10.1016/j.tim.2023.06.008

bioRxiv. 2023 Jul 07. pii: 2023.07.06.547955. [Epub ahead of print]

Single cell susceptibility to SARS-CoV-2 infection is driven by variable cell states.

Sam Reffsin, Jesse Miller, Kasirajan Ayyanathan, Margaret C Dunagin, Naveen Jain, David C Schultz, Sara Cherry, Arjun Raj.

The ability of a virus to infect a cell type is at least in part determined by the presence of host factors required for the viral life cycle. However, even within cell types that express known factors needed for infection, not every cell is equally susceptible, suggesting that our knowledge of the full spectrum of factors that promote infection is incomplete. Profiling the most susceptible subsets of cells within a population may reveal additional factors that promote infection. However, because viral infection dramatically alters the state of the cell, new approaches are needed to reveal the state of these cells prior to infection with virus. Here, we used single-cell clone tracing to retrospectively identify and characterize lung epithelial cells that are highly susceptible to infection with SARS-CoV-2. The transcriptional state of these highly susceptible cells includes markers of retinoic acid signaling and epithelial differentiation. Loss of candidate factors identified by our approach revealed that many of these factors play roles in viral entry. Moreover, a subset of these factors exert control over the infectable cell state itself, regulating the expression of key factors associated with viral infection and entry. Analysis of patient samples revealed the heterogeneous expression of these factors across both cells and patients in vivo . Further, the expression of these factors is upregulated in particular inflammatory pathologies. Altogether, our results show that the variable expression of intrinsic cell states is a major determinant of whether a cell can be infected by SARS-CoV-2.

DOI: https://doi.org/10.1101/2023.07.06.547955

Autophagy. 2023 Jul 20.

Noncanonical autophagy is a new strategy to inhibit HSV-1 through STING1 activation.

Zhihua Zheng, Man Zhao, Hao Shan, Dongmei Fang, Zuyi Jin, Jiuge Tang, Zhiping Liu, Liang Hong, Peiqing Liu, Min Li.

STING1 (stimulator of interferon response cGAMP interactor 1) plays an essential role in immune responses for virus inhibition via inducing the production of type I interferon, inflammatory factors and macroautophagy/autophagy. In this study, we found that STING1 activation could induce not only canonical autophagy but also non-canonical autophagy (NCA) which is independent of the ULK1 or BECN1 complexes to form MAP1LC3/LC3-positive structures. Whether STING1-induced NCA has similar characters and physiological functions to canonical autophagy is totally unknown. Different from canonical autophagy, NCA could increase single-membrane structures and failed to degrade long-lived proteins, and could be strongly suppressed by interrupting vacuolar-type H+-translocating ATPase (V-ATPase) activity. Importantly, STING1-induced NCA could effectively inhibit DNA virus HSV-1 in cell model. Moreover, STING1[1-340], a STING1 mutant lacking immunity and inflammatory response due to deletion of the tail end of STING1, could degrade virus through NCA alone, suggesting that the antiviral effect of activated STING1 could be separately mediated by inherent immunity, canonical autophagy, and NCA. In addition, the translocation and dimerization of STING1 do not rely on its immunity function and autophagy pathway. Similar to canonical autophagy, LC3-positive structures of NCA induced by STING1 could finally fuse with lysosomes, and the degradation of HSV-1 could be reverted by inhibition of lysosome function, suggesting that the elimination of DNA virus via NCA still requires the lysosome pathway. Collectively, we proved that besides its classical immunity function and canonical autophagy pathway, STING1-induced NCA is also an efficient antiviral pathway for the host cell.

Keywords: HSV-1; STING1; autophagy; inherent immunity; lysosome degradation; noncanonical autophagy

DOI: https://doi.org/10.1080/15548627.2023.2237794

bioRxiv. 2023 Jul 05. pii: 2023.07.05.547824. [Epub ahead of print]

Alphavirus-induced transcriptional and translational shutoffs play major roles in blocking the formation of stress granules.

Oksana Palchevska, Francisco Dominguez, Elena I Frolova, Ilya Frolov.

Alphavirus infections cause multiple alterations in the intracellular environment that can have both positive and negative effects on viral replication. The Old World alphaviruses, such as Sindbis (SINV), chikungunya (CHIKV), and Semliki Forest viruses, hinder the ability of vertebrate cells to form stress granules (SGs). Previously, this inhibitory function was attributed to the hypervariable domain (HVD) of nsP3, which sequesters the key components of SGs, G3BP1 and G3BP2, and to the nsP3 macro domain. The macro domain possesses ADP-ribosylhydrolase activity, which can diminish the ADP-ribosylation of G3BP1 during viral replication. However, our recent findings do not support the prevailing notions. We demonstrate that the interactions between SINV- or CHIKV-specific nsP3s and G3BPs, and the ADP-ribosylhydrolase activity are not major contributors to the inhibitory process, at least when nsP3 is expressed at biologically relevant levels. Instead, the primary factors responsible for suppressing SG formation are virus-induced transcriptional and translational shutoffs that rapidly develop within the first few hours post infection. Poorly replicating SINV variants carrying mutated nsP3 HVD still inhibit SG development even in the presence of NaAs. Conversely, SINV mutants lacking transcription and/or translation inhibitory functions lose their ability to inhibit SGs, despite expressing high levels of wt nsP3. Moreover, we found that stable cell lines expressing GFP-nsP3 fusions retain the capacity to form SGs when exposed to sodium arsenite. However, our results do not rule out a possibility that additional virus-induced changes in cell biology may contribute to the suppression of SG formation.
Importance: Our study highlights the mechanisms behind the cell's resistance to SG formation after infection with Old World alphaviruses. Shortly after infection, the replication of these viruses hinders the cell's ability to form SGs, even when exposed to chemical inducers such as sodium arsenite. This resistance is primarily attributed to virus-induced transcriptional and translational shutoffs, rather than interactions between the viral nsP3 and the key components of SGs, G3BP1/2, or the ADP-ribosylhydrolase activity of nsP3 macro domain. While interactions between G3BP and nsP3 are essential for the formation of viral replication complexes, their role in regulating SG development appears to be minimal, if any. Cells harboring replicating virus-specific RNA with modified abilities to inhibit transcription and/or translation, but encoding wt nsP3, retain the capacity for SG development. Understanding these mechanisms of regulation of SG development contributes to our knowledge of viral replication and the intricate relationships between alphaviruses and host cells.

DOI: https://doi.org/10.1101/2023.07.05.547824

Elife. 2023 07 20. pii: RP87696. [Epub ahead of print]12

Rubella virus tropism and single-cell responses in human primary tissue and microglia-containing organoids.

Galina Popova, Hanna Retallack, Chang N Kim, Albert Wang, David Shin, Joseph L DeRisi, Tomasz Nowakowski.

Rubella virus is an important human pathogen that can cause neurological deficits in a developing fetus when contracted during pregnancy. Despite successful vaccination programs in the Americas and many developed countries, rubella remains endemic in many regions worldwide and outbreaks occur wherever population immunity is insufficient. Intense interest since rubella virus was first isolated in 1962 has advanced our understanding of clinical outcomes after infection disrupts key processes of fetal neurodevelopment. Yet it is still largely unknown which cell types in the developing brain are targeted. We show that in human brain slices, rubella virus predominantly infects microglia. This infection occurs in a heterogeneous population but not in a highly microglia-enriched monoculture in the absence of other cell types. By using an organoid-microglia model, we further demonstrate that rubella virus infection leads to a profound interferon response in non-microglial cells, including neurons and neural progenitor cells, and this response is attenuated by the presence of microglia.

Keywords: brain organoid; development; human; neuroscience; regenerative medicine; stem cells

DOI: https://doi.org/10.7554/eLife.87696