Endogenous Retrovirus Elements Are Co-Expressed with IFN Stimulation Genes in the JAK-STAT Pathway

RNA sensing induced by chromosome missegregation augments anti-tumor immunity

Viral mimicry driven by endogenous double-stranded RNA (dsRNA) stimulates innate and adaptive immune responses. However, the mechanisms that regulate dsRNA-forming transcripts during cancer therapy remain unclear. Here, we demonstrate that dsRNA is significantly accumulated in cancer cells following pharmacologic induction of micronuclei, stimulating mitochondrial antiviral signaling (MAVS)-mediated dsRNA sensing in conjunction with the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway. Activation of cytosolic dsRNA sensing cooperates with double-stranded DNA (dsDNA) sensing to upregulate immune cell migration and antigen-presenting machinery. Tracing of dsRNA-sequences reveals that dsRNA-forming transcripts are predominantly generated from non-exonic regions, particularly in locations proximal to genes exhibiting high chromatin accessibility. Activation of this pathway by pulsed monopolar spindle 1 (MPS1) inhibitor treatment, which potently induces micronuclei formation, upregulates cytoplasmic dsRNA sensing and thus promotes anti-tumor immunity mediated by cytotoxic lymphocyte activation in vivo. Collectively, our findings uncover a mechanism in which dsRNA sensing cooperates with dsDNA sensing to boost immune responses, offering an approach to enhance the efficacy of cancer therapies targeting genomic instability.

Endogenous retroviruses modulate the susceptibility of mice to Staphylococcus aureus-induced mastitis by activating cGAS-STING signaling

Recently studies showed that cow mastitis seriously affected the economic benefit of dairy industry and pathogen infection including S. aureus is the main cause of mastitis. However, there is still a lack of safe and effective treatment for S. aureus-induced mastitis due to its complex pathogenesis. Endogenous retroviruses (ERVs) have long been symbiotic with mammals, and most ERVs still have the ability to produces complementary DNA (cDNA) by reverse transcription, whose induction by commensal or pathogens can regulate host immunity and inflammatory responses through the cGAS-STING pathway. However, whether and how ERVs participate in the pathogenesis of S. aureus-induced mastitis still unclear. In this study, we found that S. aureus treatment increased the levels of ERVs and IFN-β. Inhibition the transcription of ERVs by emtricitabine alleviated S. aureus-induced mammary injury, reduced mammary bacterial burden, and inhibited the production of mammary proinflammatory factors including TNF-α, IL-1β and MPO activity. Moreover, inhibition of ERVs restored the function of blood-milk barrier caused by S. aureus. Next, we showed that S. aureus infection activated mammary cGAS-STING signaling pathway, which was mediated by ERVs, as evidenced by emtricitabine inhibited S. aureus-induced activation of the cGAS-STING pathway. Interestingly, inhibition of cGAS-STING by Ru.521 and H151 respectively, significantly alleviated S. aureus-induced mammary injury and inflammatory responses, which was associated with the inhibition of NF-κB and NLRP3 signaling pathways. In conclusion, our study revealed that ERVs regulate the development of S. aureus-induced mastitis in mice through NF-κB- and NLRP3-mediated inflammatory responses via the activation of cGAS-STING pathway, suggesting that targeting ERVs-cGAS-STING axis may be a potential approach for the treatment of S. aureus-induced mastitis.

Promiscuous Janus kinase binding to cytokine receptors modulates signaling efficiencies and contributes to cytokine pleiotropy

Janus kinases (JAKs) bind to class I and II cytokine receptors, activating signaling and regulating gene transcription through signal transducer and activator of transcription (STAT) proteins. Type I interferons (IFNs) require the JAK members TYK2 and JAK1, which bind to the receptor subunits IFNAR1 and IFNAR2, respectively. We investigated the role of JAKs in regulating IFNAR signaling activity. Synthetic IFNARs in which the extracellular domains of IFNAR1 and IFNAR2 are replaced with nanobodies had near-native type I IFN signaling, whereas the homomeric variant of IFNAR2 initiated much weaker signaling, despite harboring docking sites for JAKs and STATs. Cells with JAK1 and TYK2 knockout (KO) showed residual signaling, suggesting partial complementation by the remaining JAKs, particularly when they were overexpressed. Live-cell micropatterning experiments confirmed the promiscuous binding of JAK1, JAK2, and TYK2 to IFNAR1 and IFNAR2, and their recruitment correlated with their relative cellular abundances. However, each JAK had a different efficacy in inducing cross-phosphorylation and downstream signaling. JAK binding was also promiscuous for other cytokine receptors, including IFN-L1, IL-10Rβ, TPOR, and GHR, but not for EPOR, which activated different downstream signaling pathways. These findings suggest that competitive binding of JAKs to cytokine receptors together with the varying absolute and relative abundances of the JAKs in different cell types can account for the cell type-dependent signaling pleiotropy of cytokine receptors.

Apoptotic Caspases Suppress Expression of Endogenous Retroviruses in HPV31+ Cells That Are Associated with Activation of an Innate Immune Response

Avoidance of an immune response is critical to completion of the human papillomavirus (HPV) life cycle, which occurs in the stratified epithelium and is linked to epithelial differentiation. We previously demonstrated that high-risk HPVs use apoptotic caspases to suppress an antiviral innate immune response during the productive phase of the life cycle. We found that caspase-8 and caspase-3 suppress a type I IFN-β and type III IFN-λ response by disabling the MDA5/MAVS double-stranded RNA (dsRNA) sensing pathway, indicating that immunogenic RNAs increase upon differentiation in HPV+ cells. In this study, we demonstrate that caspase inhibition results in aberrant transcription of a subset of endogenous retroviruses (ERVs) that have been shown to activate an IFN response through dsRNA-sensing pathways. We show that the increase in ERV transcription is accompanied by an enrichment in dsRNA formation. Additionally, we demonstrate that the robust increase in ERV expression requires activation of the JAK/STAT-signaling pathway, indicating that this subset of ERVs is IFN-inducible. Overall, these results suggest a model by which caspase activity blocks the reactivation of ERVs through the JAK/STAT pathway, protecting HPV+ cells from an increase in immunogenic dsRNAs that otherwise would trigger an IFN response that inhibits productive viral replication.

Pharmacological activation of TLR7 exerts inhibition on the replication of EV-D68 in respiratory cells

The globally reemerging respiratory pathogen enterovirus D68 (EV-D68) is implicated in outbreaks of severe respiratory illness and associated with acute flaccid myelitis. However, there remains a lack of effective treatments for EV-D68 infection. In this work, we found that the host Toll-like receptor 7 (TLR7) proteins, which function as powerful innate immune sensors, were selectively elevated in expression in response to EV-D68 infection. Subsequently, we investigated the impact of Vesatolimod (GS-9620), a Toll-like receptor 7 agonist, on EV-D68 replication. Our findings revealed that EV-D68 infection resulted in increased mRNA levels of TLR7. Treatment with Vesatolimod significantly inhibited EV-D68 replication [half maximal effective concentration (EC50) = 0.1427 µM] without inducing significant cytotoxicity at virucidal concentrations. Although Vesatolimod exhibited limited impact on EV-D68 attachment, it suppressed RNA replication and viral protein synthesis after virus entry. Vesatolimod broadly inhibited the replication of circulating isolated strains of EV-D68. Furthermore, our findings demonstrated that treatment with Vesatolimod conferred resistance to both respiratory and neural cells against EV-D68 infection. Overall, these results present a promising strategy for drug development by pharmacologically activating TLR7 to initiate an antiviral state in EV-D68-infected cells selectively.IMPORTANCEConventional strategies for antiviral drug development primarily focus on directly targeting viral proteases or key components, as well as host proteins involved in viral replication. In this study, based on our intriguing discovery that enterovirus D68 (EV-D68) infection specifically upregulates the expression of immune sensor Toll-like receptor 7 (TLR7) protein, which is either absent or expressed at low levels in respiratory cells, we propose a potential antiviral approach utilizing TLR7 agonists to activate EV-D68-infected cells into an anti-viral defense state. Notably, our findings demonstrate that pharmacological activation of TLR7 effectively suppresses EV-D68 replication in respiratory tract cells through a TLR7/MyD88-dependent mechanism. This study not only presents a promising drug candidate and target against EV-D68 dissemination but also highlights the potential to exploit unique alterations in cellular innate immune responses induced by viral infections, selectively inducing a defensive state in infected cells while safeguarding uninfected normal cells from potential adverse effects associated with therapeutic interventions.

Roles of interferon induced protein with tetratricopeptide repeats (IFIT) family in autoimmune disease

Interferon-induced tetrapeptide repeat (IFIT) family proteins are an important component of the antiviral immune response. There are four known members of the human IFIT family, namely IFIT1, IFIT2, IFIT3 and IFIT5. More and more evidence shows that IFIT family members are involved in a variety of pathophysiological processes in vivo, regulate the homeostasis and differentiation of a variety of cells including immune cells, and are closely related to a variety of autoimmune diseases, which is expected to become a new therapeutic target. This review reviews the biological roles of different IFIT proteins in various autoimmune diseases, and highlights the potential use of these molecules as biomarkers and prognostic factors in autoimmune diseases, with a view to providing ideas for exploring the diagnosis and treatment of autoimmune diseases.

COVID-19. Biology, pathophysiology, and immunology: a pathologist view

Even if the SARS-CoV-2 pandemic has been declared over, several risks and clinical problems remain to be faced, including long-COVID sequelae and possible outbreaks of pathogenic variants. Intense research on COVID-19 has provided in these few years a striking amount of data covering different fields and disciplines, which can help to provide a knowledge shield against new potential infective spreads, and may also potentially be applied to other fields of medicine, including oncology and neurology. Nevertheless, areas of uncertainty still remain regarding the pathogenic mechanisms that subtend the multifaceted manifestations of the disease. To better clarify the pathogenesis of the disease, a systematic multidisciplinary evaluation of the many mechanisms involved in COVID-19 is mandatory, including clinical, physiological, radiological, immunological and pathological studies. In COVID-19 syndrome the pathological studies have been mainly performed on autopsy cases, and only a few studies are available on biopsies. Nevertheless, these studies have provided relevant information that can substantially contribute to decipher the complex scenario characterizing the different forms of COVID-19 and long-COVID-19. In this review the data provided by pathological investigations are recapitulated and discussed, in the light of different hypothesis and data provided by clinical, physiological and immunological data.