Longitudinal analyses of the innate immune system, including the earliest time points, are essential to understand the immunopathogenesis and clinical course of coronavirus disease (COVID-19). Here, ...we performed a detailed characterization of natural killer (NK) cells in 205 patients (403 samples; days 2 to 41 after symptom onset) from four independent cohorts using single-cell transcriptomics and proteomics together with functional studies. We found elevated interferon (IFN)-α plasma levels in early severe COVD-19 alongside increased NK cell expression of IFN-stimulated genes (ISGs) and genes involved in IFN-α signaling, while upregulation of tumor necrosis factor (TNF)-induced genes was observed in moderate diseases. NK cells exert anti-SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) activity but are functionally impaired in severe COVID-19. Further, NK cell dysfunction may be relevant for the development of fibrotic lung disease in severe COVID-19, as NK cells exhibited impaired anti-fibrotic activity. Our study indicates preferential IFN-α and TNF responses in severe and moderate COVID-19, respectively, and associates a prolonged IFN-α-induced NK cell response with poorer disease outcome.
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•Elevated IFN-α plasma levels characteristic for early severe COVID-19 (sCOVID-19)•Differential IFN-α vs. TNF signaling discriminates severe vs. moderate COVID-19•NK cells exert anti-SARS-CoV-2 activity but are functionally impaired in sCOVID-19•Persistent NK cell dysfunction may promote fibrotic lung disease in sCOVID-19
The importance of NK cells in the innate response to viral infection provides rationale for deeper understanding of their role in COVID-19. Here, Krämer et al. utilize longitudinal analysis of NK cells to show early TNF and IFN-α signatures associated with moderate and severe COVID-19, respectively, and NK cell functional impairment in severe disease.
Treatment of tumors with ionizing radiation stimulates an antitumor immune response partly dependent on induction of IFNs. These IFNs directly enhance dendritic cell and CD8+ T cell activity. Here we ...show that resistance to an effective antitumor immune response is also a result of IFN signaling in a different cellular compartment of the tumor, the cancer cells themselves. We abolished type I IFN signaling in cancer cells by genetic elimination of its receptor, IFNAR1. Pronounced immune responses were provoked after ionizing radiation of tumors from 4 mouse cancer cell lines with Ifnar1 knockout. This enhanced response depended on CD8+ T cells and was mediated by enhanced susceptibility to T cell-mediated killing. Induction of Serpinb9 proved to be the mechanism underlying control of susceptibility to T cell killing after radiation. Ifnar1-deficient tumors had an augmented response to anti-PD-L1 immunotherapy with or without radiation. We conclude that type I IFN can protect cancer cells from T cell-mediated cytotoxicity through regulation of Serpinb9. This result helps explain why radiation of tumors can stimulate antitumor immunity yet also result in resistance. It further suggests potential targets for intervention to improve therapy and to predict responses.
Neutrophil extracellular trap (NET) formation promotes vascular damage, thrombosis, and activation of interferon-α-producing plasmacytoid dendritic cells in diseased arteries. Peptidylarginine ...deiminase inhibition is a strategy that can decrease in vivo NET formation.
To test whether peptidylarginine deiminase inhibition, a novel approach to targeting arterial disease, can reduce vascular damage and inhibit innate immune responses in murine models of atherosclerosis.
Apolipoprotein-E (Apoe)(-/-) mice demonstrated enhanced NET formation, developed autoantibodies to NETs, and expressed high levels of interferon-α in diseased arteries. Apoe(-/-) mice were treated for 11 weeks with daily injections of Cl-amidine, a peptidylarginine deiminase inhibitor. Peptidylarginine deiminase inhibition blocked NET formation, reduced atherosclerotic lesion area, and delayed time to carotid artery thrombosis in a photochemical injury model. Decreases in atherosclerosis burden were accompanied by reduced recruitment of netting neutrophils and macrophages to arteries, as well as by reduced arterial interferon-α expression.
Pharmacological interventions that block NET formation can reduce atherosclerosis burden and arterial thrombosis in murine systems. These results support a role for aberrant NET formation in the pathogenesis of atherosclerosis through modulation of innate immune responses.
Type I interferon (IFN) is crucial in host antiviral defense. Previous studies have described the pleiotropic role of type I IFNs on innate and adaptive immune cells during viral infection. Here, we ...demonstrate that natural killer (NK) cells from mice lacking the type I IFN-α receptor (Ifnar(-/-)) or STAT1 (which signals downstream of IFNAR) are defective in expansion and memory cell formation after mouse cytomegalovirus (MCMV) infection. Despite comparable proliferation, Ifnar(-/-) NK cells showed diminished protection against MCMV infection and exhibited more apoptosis compared with wild-type NK cells. Furthermore, we show that Ifnar(-/-) NK cells express increased levels of NK group 2 member D (NKG2D) ligands during viral infection and are susceptible to NK cell-mediated fratricide in a perforin- and NKG2D-dependent manner. Adoptive transfer of Ifnar(-/-) NK cells into NK cell-deficient mice reverses the defect in survival and expansion. Our study reveals a novel type I IFN-dependent mechanism by which NK cells evade mechanisms of cell death after viral infection.
Tissue factor (TF), which is a member of the cytokine receptor family, promotes coagulation and coagulation-dependent inflammation. TF also exerts protective effects through unknown mechanisms. Here, ...we showed that TF bound to interferon-α receptor 1 (IFNAR1) and antagonized its signaling, preventing spontaneous sterile inflammation and maintaining immune homeostasis. Structural modeling and direct binding studies revealed binding of the TF C-terminal fibronectin III domain to IFNAR1, which restricted the expression of interferon-stimulated genes (ISGs). Podocyte-specific loss of TF in mice (Pod
) resulted in sterile renal inflammation, characterized by JAK/STAT signaling, proinflammatory cytokine expression, disrupted immune homeostasis, and glomerulopathy. Inhibiting IFNAR1 signaling or loss of Ifnar1 expression in podocytes attenuated these effects in Pod
mice. As a heteromer, TF and IFNAR1 were both inactive, while dissociation of the TF-IFNAR1 heteromer promoted TF activity and IFNAR1 signaling. These data suggest that the TF-IFNAR1 heteromer is a molecular switch that controls thrombo-inflammation.
Chronic infection with hepatitis C virus (HCV) affects 170 million people worldwide and is the leading cause of cirrhosis in North America. Although the recommended treatment for chronic infection ...involves a 48-week course of peginterferon- -2b (PegIFN- -2b) or - -2a (PegIFN- -2a) combined with ribavirin (RBV), it is well known that many patients will not be cured by treatment, and that patients of European ancestry have a significantly higher probability of being cured than patients of African ancestry. In addition to limited efficacy, treatment is often poorly tolerated because of side effects that prevent some patients from completing therapy. For these reasons, identification of the determinants of response to treatment is a high priority. Here we report that a genetic polymorphism near the IL28B gene, encoding interferon- -3 (IFN- -3), is associated with an approximately twofold change in response to treatment, both among patients of European ancestry (P = 1.06 × 10-25) and African-Americans (P = 2.06 × 10-3). Because the genotype leading to better response is in substantially greater frequency in European than African populations, this genetic polymorphism also explains approximately half of the difference in response rates between African-Americans and patients of European ancestry.
Interferon-α (IFN-α) is essential for antiviral immunity, but in the absence of matrix metalloproteinase-12 (MMP-12) or IκBα (encoded by NFKBIA) we show that IFN-α is retained in the cytosol of ...virus-infected cells and is not secreted. Our findings suggest that activated IκBα mediates the export of IFN-α from virus-infected cells and that the inability of cells in Mmp12(-/-) but not wild-type mice to express IκBα and thus export IFN-α makes coxsackievirus type B3 infection lethal and renders respiratory syncytial virus more pathogenic. We show here that after macrophage secretion, MMP-12 is transported into virus-infected cells. In HeLa cells MMP-12 is also translocated to the nucleus, where it binds to the NFKBIA promoter, driving transcription. We also identified dual-regulated substrates that are repressed both by MMP-12 binding to the substrate's gene exons and by MMP-12-mediated cleavage of the substrate protein itself. Whereas intracellular MMP-12 mediates NFKBIA transcription, leading to IFN-α secretion and host protection, extracellular MMP-12 cleaves off the IFN-α receptor 2 binding site of systemic IFN-α, preventing an unchecked immune response. Consistent with an unexpected role for MMP-12 in clearing systemic IFN-α, treatment of coxsackievirus type B3-infected wild-type mice with a membrane-impermeable MMP-12 inhibitor elevates systemic IFN-α levels and reduces viral replication in pancreas while sparing intracellular MMP-12. These findings suggest that inhibiting extracellular MMP-12 could be a new avenue for the development of antiviral treatments.
Abstract Conjugating poly(ethylene glycol) (PEG), PEGylation, to therapeutic proteins is widely used as a means to improve their pharmacokinetics and therapeutic potential. One prime example is ...PEGylated interferon-alpha (PEGASYS). However, PEGylation usually leads to a heterogeneous mixture of positional isomers with reduced bioactivity and low yield. Herein, we report site-specific in situ growth (SIG) of a PEG-like polymer, poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), from the C-terminus of interferon-alpha to form a site-specific (C-terminal) and stoichiometric (1:1) POEGMA conjugate of interferon-alpha in high yield. The POEGMA conjugate showed significantly improved pharmacokinetics, tumor accumulation and anticancer efficacy as compared to interferon-alpha. Notably, the POEGMA conjugate possessed a 7.2-fold higher in vitro antiproliferative bioactivity than PEGASYS. More importantly, in a murine cancer model, the POEGMA conjugate completely inhibited tumor growth and eradicated tumors of 75% mice without appreciable systemic toxicity, whereas at the same dose, no mice treated with PEGASYS survived for over 58 days. The outperformance of a site-specific POEGMA conjugate prepared by SIG over PEGASYS that is the current gold standard for interferon-alpha delivery suggests that SIG is of interest for the development of next-generation protein therapeutics.
Background and Aims
Interferon (IFN)‐α, composed of numerous subtypes, plays a crucial role in immune defense. As the most studied subtype, IFN‐α2 has been used for treating chronic hepatitis B virus ...(HBV) infection, with advantages of finite treatment duration and sustained virologic response, but its efficacy remains relatively low. This study aimed to screen for IFN‐α subtypes with the highest anti‐HBV potency and to characterize mechanisms of IFN‐α–mediated HBV restriction.
Approach and Results
Using cell culture–based HBV infection systems and a human‐liver chimeric mouse model, IFN‐α subtype–mediated antiviral response and signaling activation were comprehensively analyzed. IFN‐α14 was identified as the most effective subtype in suppression of HBV covalently closed circular DNA transcription and HBV e antigen/HBV surface antigen production, with median inhibitory concentration values approximately 100‐fold lower than those of the conventional IFN‐α2. IFN‐α14 alone elicited IFN‐α and IFN‐γ signaling crosstalk in a manner similar to the combined use of IFN‐α2 and IFN‐γ, inducing multiple potent antiviral effectors, which synergistically restricted HBV replication. Guanylate binding protein 5, one of the most differentially expressed genes between IFN‐α14–treated and IFN‐α2–treated liver cells, was identified as an HBV restriction factor. A strong IFN‐α–IFN‐α receptor subunit 1 interaction determines the anti‐HBV activity of IFN‐α. The in vivo anti‐HBV activity of IFN‐α14 and treatment‐related transcriptional patterns were further confirmed, and few adverse effects were observed.
Conclusions
A concerted IFN‐α and IFN‐γ response in liver, which could be efficiently elicited by IFN‐α subtype 14, is associated with potent HBV suppression. These data deepen the understanding of the divergent activities of IFN‐α subtypes and the mechanism underlying the synergism between IFN‐α and IFN‐γ signaling, with implications for improved IFN therapy and HBV curative strategies.
Despite the efficient suppression of HIV-1 replication that can be achieved with combined antiretroviral therapy (cART), low levels of type I interferon (IFN-I) signaling persist in some individuals. ...This sustained signaling may impede immune recovery and foster viral persistence. Here we report studies using a monoclonal antibody to block IFN-α/β receptor (IFNAR) signaling in humanized mice (hu-mice) that were persistently infected with HIV-1. We discovered that effective cART restored the number of human immune cells in HIV-1-infected hu-mice but did not rescue their immune hyperactivation and dysfunction. IFNAR blockade fully reversed HIV-1-induced immune hyperactivation and rescued anti-HIV-1 immune responses in T cells from HIV-1-infected hu-mice. Finally, we found that IFNAR blockade in the presence of cART reduced the size of HIV-1 reservoirs in lymphoid tissues and delayed HIV-1 rebound after cART cessation in the HIV-1-infected hu-mice. We conclude that low levels of IFN-I signaling contribute to HIV-1-associated immune dysfunction and foster HIV-1 persistence in cART-treated hosts. Our results suggest that blocking IFNAR may provide a potential strategy to enhance immune recovery and reduce HIV-1 reservoirs in individuals with sustained elevations in IFN-I signaling during suppressive cART.
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