Crosstalk between Autophagy and Type I Interferon Responses in Innate Antiviral Immunity

From defense to offense: Modulating toll-like receptors to combat arbovirus infections

Arboviruses are a significant threat to global public health, with outbreaks occurring worldwide. Toll-like receptors (TLRs) play a crucial role in the innate immune response against these viruses by recognizing pathogen-associated molecular patterns and initiating an inflammatory response. Significantly, TLRs commonly implicated in the immune response against viral infections include TLR2, TLR4, TLR6, TLR3, TLR7, and TLR8; limiting or allowing them to replicate and spread within the host. Modulating TLRs has emerged as a promising approach to combat arbovirus infections. This review summarizes recent advances in TLR modulation as a therapeutic target in arbovirus infections. Studies have shown that the activation of TLRs can enhance the immune response against arbovirus infections, leading to increased viral clearance and protection against disease. Conversely, inhibition of TLRs can reduce the excessive inflammation and tissue damage associated with arbovirus infection. Modulating TLRs represents a potential therapeutic strategy to combat arbovirus infections.

Types of cell death and their relations to host immunological pathways

Various immune pathways have been identified in the host, including TH1, TH2, TH3, TH9, TH17, TH22, TH1-like, and THαβ immune reactions. While TH2 and TH9 responses primarily target multicellular parasites, host immune pathways directed against viruses, intracellular microorganisms (such as bacteria, protozoa, and fungi), and extracellular microorganisms can employ programmed cell death mechanisms to initiate immune responses or execute effective strategies for pathogen elimination. The types of programmed cell death involved include apoptosis, autophagy, pyroptosis, ferroptosis, necroptosis, and NETosis. Specifically, apoptosis is associated with host anti-virus eradicable THαβ immunity, autophagy with host anti-virus tolerable TH3 immunity, pyroptosis with host anti-intracellular microorganism eradicable TH1 immunity, ferroptosis with host anti-intracellular microorganism tolerable TH1-like immunity, necroptosis with host anti-extracellular microorganism eradicable TH22 immunity, and NETosis with host anti-extracellular microorganism tolerable TH17 immunity.

Colchicine-mediated selective autophagic degradation of HBV core proteins inhibits HBV replication and HBV-related hepatocellular carcinoma progression

The HBV core protein (HBc) is an important viral protein of HBV that plays an indispensable role in the lifecycle of HBV, including capsid assembly and transport, reverse transcription and virus release. In recent years, evidence has shown that HBc may be involved in the malignant progression of HCC. Thus, HBc is an attractive target for antiviral agents and provides a new strategy for the treatment of HBV-related HCC. Here, we identified a novel anti-HBc compound-colchicine, an alkaloid compound-that promoted selective autophagic degradation of HBc through the AMPK/mTOR/ULK1 signalling pathway. We further confirmed that colchicine promoted the selective autophagy of HBc by enhancing the binding of HBc to the autophagy receptor p62. Finally, we evaluated the effects of colchicine on HBV replication and HBc-mediated HCC metastasis in vitro and in vivo. Our research indicated that the inhibitory effects of colchicine on HBV and HBV-related HCC depend on the selective autophagic degradation of HBc. Thus, colchicine is not only a promising therapeutic strategy for chronic hepatitis B but also a new treatment for HBV-related HCC.

Bunyavirus SFTSV NSs utilizes autophagy to escape the antiviral innate immune response

Severe fever with thrombocytopenia syndrome virus (SFTSV) nonstructural protein (NSs) is an important viral virulence factor that sequesters multiple antiviral proteins into inclusion bodies to escape the antiviral innate immune response. However, the mechanism of the NSs restricting host innate immunity remains largely elusive. Here, we found that the NSs induced complete macroautophagy/autophagy by interacting with the CCD domain of BECN1, thereby promoting the formation of a BECN1-dependent autophagy initiation complex. Importantly, our data showed that the NSs sequestered antiviral proteins such as TBK1 into autophagic vesicles, and therefore promoted the degradation of TBK1 and other antiviral proteins. In addition, the 8A mutant of NSs reduced the induction of BECN1-dependent autophagy flux and degradation of antiviral immune proteins. In conclusion, our results indicated that SFTSV NSs sequesters antiviral proteins into autophagic vesicles for degradation and to escape antiviral immune responses.

Burning down the house: Pyroptosis in the tumor microenvironment of hepatocellular carcinoma

A high mortality rate makes hepatocellular carcinoma (HCC) a difficult cancer to treat. When surgery is not possible, liver cancer patients are treated with chemotherapy. However, HCC management and treatment are difficult. Sorafenib, which is a first-line treatment for hepatocellular carcinoma, initially slows disease progression. However, sorafenib resistance limits patient survival. Recent studies have linked HCC to programmed cell death, which has increased researcher interest in therapies targeting cell death. Pyroptosis, which is an inflammatory mode of programmed cell death, may be targeted to treat HCC. Pyroptosis pathways, executors, and effects are examined in this paper. This review summarizes how pyroptosis affects the tumor microenvironment (TME) in HCC, including the role of cytokines such as IL-1β and IL-18 in regulating immune responses. The use of chemotherapies and their ability to induce cancer cell pyroptosis as alternative treatments and combining them with other drugs to reduce side effects is also discussed. In conclusion, we highlight the potential of inducing pyroptosis to treat HCC and suggest ways to improve patient outcomes. Studies on cancer cell pyroptosis may lead to new HCC treatments.

Deciphering the Role of Epstein-Barr Virus Latent Membrane Protein 1 in Immune Modulation: A Multifaced Signalling Perspective

The disruption of antiviral sensors and the evasion of immune defences by various tactics are hallmarks of EBV infection. One of the EBV latent gene products, LMP1, was shown to induce the activation of signalling pathways, such as NF-κB, MAPK (JNK, ERK1/2, p38), JAK/STAT and PI3K/Akt, via three subdomains of its C-terminal domain, regulating the expression of several cytokines responsible for modulation of the immune response and therefore promoting viral persistence. The aim of this review is to summarise the current knowledge on the EBV-mediated induction of immunomodulatory molecules by the activation of signal transduction pathways with a particular focus on LMP1-mediated mechanisms. A more detailed understanding of the cytokine biology molecular landscape in EBV infections could contribute to the more complete understanding of diseases associated with this virus.

The ZIKV NS5 Protein Aberrantly Alters the Tubulin Cytoskeleton, Induces the Accumulation of Autophagic p62 and Affects IFN Production: HDAC6 Has Emerged as an Anti-NS5/ZIKV Factor

Zika virus (ZIKV) infection and pathogenesis are linked to the disruption of neurogenesis, congenital Zika syndrome and microcephaly by affecting neural progenitor cells. Nonstructural protein 5 (NS5) is the largest product encoded by ZIKV-RNA and is important for replication and immune evasion. Here, we studied the potential effects of NS5 on microtubules (MTs) and autophagy flux, together with the interplay of NS5 with histone deacetylase 6 (HDAC6). Fluorescence microscopy, biochemical cell-fractionation combined with the use of HDAC6 mutants, chemical inhibitors and RNA interference indicated that NS5 accumulates in nuclear structures and strongly promotes the acetylation of MTs that aberrantly reorganize in nested structures. Similarly, NS5 accumulates the p62 protein, an autophagic-flux marker. Therefore, NS5 alters events that are under the control of the autophagic tubulin-deacetylase HDAC6. HDAC6 appears to degrade NS5 by autophagy in a deacetylase- and BUZ domain-dependent manner and to control the cytoplasmic expression of NS5. Moreover, NS5 inhibits RNA-mediated RIG-I interferon (IFN) production, resulting in greater activity when autophagy is inhibited (i.e., effect correlated with NS5 stability). Therefore, it is conceivable that NS5 contributes to cell toxicity and pathogenesis, evading the IFN-immune response by overcoming HDAC6 functions. HDAC6 has emerged as an anti-ZIKV factor by targeting NS5.

The relationship between autophagy and respiratory viruses

Respiratory viruses have caused severe global health problems and posed essential challenges to the medical community. In recent years, the role of autophagy as a critical process in cells in viral respiratory diseases has been noticed. One of the vital catabolic biological processes in the body is autophagy. Autophagy contributes to energy recovery by targeting and selectively directing foreign microorganisms, organelles, and senescent intracellular proteins to the lysosome for degradation and phagocytosis. Activation or suppression of autophagy is often initiated when foreign pathogenic organisms such as viruses infect cells. Because of its antiviral properties, several viruses may escape or resist this process by encoding viral proteins. Viruses can also use autophagy to enhance their replication or prolong the persistence of latent infections. Here, we provide an overview of autophagy and respiratory viruses such as coronavirus, rhinovirus, parainfluenza, influenza, adenovirus, and respiratory syncytial virus, and examine the interactions between them and the role of autophagy in the virus-host interaction process and the resulting virus replication strategy.

An LIR motif in the Rift Valley fever virus NSs protein is critical for the interaction with LC3 family members and inhibition of autophagy

Rift Valley fever virus (RVFV) is a viral zoonosis that causes severe disease in ruminants and humans. The nonstructural small (NSs) protein is the primary virulence factor of RVFV that suppresses the host's antiviral innate immune response. Bioinformatic analysis and AlphaFold structural modeling identified four putative LC3-interacting regions (LIR) motifs (NSs 1-4) in the RVFV NSs protein, which suggest that NSs interacts with the host LC3-family proteins. Using, isothermal titration calorimetry, X-ray crystallography, co-immunoprecipitation, and co-localization experiments, the C-terminal LIR motif (NSs4) was confirmed to interact with all six human LC3 proteins. Phenylalanine at position 261 (F261) within NSs4 was found to be critical for the interaction of NSs with LC3, retention of LC3 in the nucleus, as well as the inhibition of autophagy in RVFV infected cells. These results provide mechanistic insights into the ability of RVFV to overcome antiviral autophagy through the interaction of NSs with LC3 proteins.

HCV-induced autophagy and innate immunity

The interplay between autophagy and host innate immunity has been of great interest. Hepatitis C virus (HCV) impedes signaling pathways initiated by pattern-recognition receptors (PRRs) that recognize pathogens-associated molecular patterns (PAMPs). Autophagy, a cellular catabolic process, delivers damaged organelles and protein aggregates to lysosomes for degradation and recycling. Autophagy is also an innate immune response of cells to trap pathogens in membrane vesicles for removal. However, HCV controls the autophagic pathway and uses autophagic membranes to enhance its replication. Mitophagy, a selective autophagy targeting mitochondria, alters the dynamics and metabolism of mitochondria, which play important roles in host antiviral responses. HCV also alters mitochondrial dynamics and promotes mitophagy to prevent premature cell death and attenuate the interferon (IFN) response. In addition, the dysregulation of the inflammasomal response by HCV leads to IFN resistance and immune tolerance. These immune evasion properties of HCV allow HCV to successfully replicate and persist in its host cells. In this article, we discuss HCV-induced autophagy/mitophagy and its associated immunological responses and provide a review of our current understanding of how these processes are regulated in HCV-infected cells.

Protein Quality Control Systems and ER Stress as Key Players in SARS-CoV-2-Induced Neurodegeneration

The COVID-19 pandemic has brought to the forefront the intricate relationship between SARS-CoV-2 and its impact on neurological complications, including potential links to neurodegenerative processes, characterized by a dysfunction of the protein quality control systems and ER stress. This review article explores the role of protein quality control systems, such as the Unfolded Protein Response (UPR), the Endoplasmic Reticulum-Associated Degradation (ERAD), the Ubiquitin-Proteasome System (UPS), autophagy and the molecular chaperones, in SARS-CoV-2 infection. Our hypothesis suggests that SARS-CoV-2 produces ER stress and exploits the protein quality control systems, leading to a disruption in proteostasis that cannot be solved by the host cell. This disruption culminates in cell death and may represent a link between SARS-CoV-2 and neurodegeneration.

All-Cause and Cause-Specific Mortality among Patients with Vitiligo: A Nationwide Population-Based Study in Korea

Vitiligo is a common autoimmune skin disorder; however, there is limited information about risks of mortality among patients with vitiligo. Therefore, we aimed to investigate the mortality in patients with vitiligo. A population-based cohort study was conducted using the data linkage of the National Health Insurance Service database and the National Death Registry. Patients with incident vitiligo were matched with sociodemographic factors-matched controls without vitiligo in a 1:5 ratio. All-cause and cause-specific mortalities were compared between patients with vitiligo and controls. In total, 107,424 patients with incident vitiligo and 537,120 matched controls were included. The mortality rates were 34.8 and 45.3 per 10,000 person-years in patients and controls, respectively. Patients with vitiligo showed a significantly lower risk of mortality (adjusted hazard ratio = 0.75, 95% confidence interval = 0.72-0.78). The cause-specific mortality from infectious diseases, oncologic diseases, hematologic diseases, endocrine diseases, neurologic diseases, cardiovascular diseases, respiratory diseases, and renal/urogenital disease was significantly lower in patients with vitiligo. Patients with vitiligo were associated with a lower risk of mortality, suggesting that vitiligo-associated autoimmunity might contribute to reduced morbidity and mortality.

The dichotomic role of single cytokines: Fine-tuning immune responses

Cytokines are known for their pleiotropic effects. They can be classified by their function as pro-inflammatory, such as tumor necrosis factor (TNF), interleukin (IL) 1 and IL-12, or anti-inflammatory, like IL-10, IL-35 and transforming growth factor β (TGF-β). Though this type of classification is an important simplification for the understanding of the general cytokine's role, it can be misleading. Here, we discuss recent studies that show a dichotomic role of the so-called pro and anti-inflammatory cytokines, highlighting that their function can be dependent on the microenvironment and their concentrations. Furthermore, we discuss how the back-and-forth interplay between cytokines and immunometabolism can influence the dichotomic role of inflammatory responses as an important target to complement cytokine-based therapies.

Apolipoproteins L1 and L3 control mitochondrial membrane dynamics

Apolipoproteins L1 and L3 (APOLs) are associated at the Golgi with the membrane fission factors phosphatidylinositol 4-kinase-IIIB (PI4KB) and non-muscular myosin 2A. Either APOL1 C-terminal truncation (APOL1Δ) or APOL3 deletion (APOL3-KO [knockout]) reduces PI4KB activity and triggers actomyosin reorganization. We report that APOL3, but not APOL1, controls PI4KB activity through interaction with PI4KB and neuronal calcium sensor-1 or calneuron-1. Both APOLs are present in Golgi-derived autophagy-related protein 9A vesicles, which are involved in PI4KB trafficking. Like APOL3-KO, APOL1Δ induces PI4KB dissociation from APOL3, linked to reduction of mitophagy flux and production of mitochondrial reactive oxygen species. APOL1 and APOL3, respectively, can interact with the mitophagy receptor prohibitin-2 and the mitophagosome membrane fusion factor vesicle-associated membrane protein-8 (VAMP8). While APOL1 conditions PI4KB and APOL3 involvement in mitochondrion fission and mitophagy, APOL3-VAMP8 interaction promotes fusion between mitophagosomal and endolysosomal membranes. We propose that APOL3 controls mitochondrial membrane dynamics through interactions with the fission factor PI4KB and the fusion factor VAMP8.

DLG1 promotes the antiviral innate immune response by inhibiting p62-mediated autophagic degradation of IKKε

IMPORTANCE

The type-I interferon (IFN-I) signaling pathway is the first line of antiviral innate immunity. It must be precisely regulated against virus-induced damage. The tightly regulated mechanisms of action of host genes in the antiviral innate immune signaling pathway are still worth studying. Here, we report a novel role of DLG1 in positively regulating the IκB kinase epsilon (IKKε)-mediated IFN-I signaling response against negative-stranded RNA virus replication, whereas the RNA virus inhibits the expression of DLG1 for immune escape. Importantly, the E3 ligase March2 interacts with and promotes K27-linked polyubiquitination of IKKε, and p62 is a cargo receptor that recognizes ubiquitinated IKKε for eventual autophagic degradation. Together, the current findings elucidate the role of DLG1 in the antiviral IFN-I signaling pathway and viral infection repression.

ATG4B antagonizes antiviral immunity by GABARAP-directed autophagic degradation of TBK1

ABBREVIATIONS

Baf A1: bafilomycin A1; GABARAP: GABA type A receptor-associated protein; GFP: green fluorescent protein; IFN: interferon; IKBKE/IKKi: inhibitor of nuclear factor kappa B kinase subunit epsilon; IRF3: interferon regulatory factor 3; ISG: interferon-stimulated gene; ISRE: IFN-stimulated response element; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAVS: mitochondrial antiviral signaling protein; MOI: multiplicity of infection; PAMPs: pathogen-associated molecule patterns; RIGI/DDX58: RNA sensor RIG-I; SeV: Sendai virus; siRNA: small interfering RNA; TBK1: TANK binding kinase 1; WT: wild-type; VSV: vesicular stomatitis virus.

miRNA Expression Signatures Induced by Chicken Astrovirus Infection in Chickens

miRNAs represent ubiquitous regulators of gene expression and play an important and pivotal regulatory role in viral disease pathogenesis and virus-host interactions. Although previous studies have provided basic data for understanding the role of miRNAs in the molecular mechanisms of viral infection in birds, the role of miRNAs in the regulation of host responses to chicken astrovirus (CAstV) infection in chickens is not yet understood. In our study, we applied next-generation sequencing to profile miRNA expression in CAstV-infected chickens and to decipher miRNA-targeted specific signaling pathways engaged in potentially vital virus-infection biological processes. Among the 1354 detected miRNAs, we identified 58 mature miRNAs that were significantly differentially expressed in infected birds. Target prediction resulted in 4741 target genes. GO and KEGG pathway enrichment analyses showed that the target genes were mainly involved in the regulation of cellular processes and immune responses.

Astrocytes Are a Key Target for Neurotropic Viral Infection

Astrocytes are increasingly recognized as important viral host cells in the central nervous system. These cells can produce relatively high quantities of new virions. In part, this can be attributed to the characteristics of astrocyte metabolism and its abundant and dynamic cytoskeleton network. Astrocytes are anatomically localized adjacent to interfaces between blood capillaries and brain parenchyma and between blood capillaries and brain ventricles. Moreover, astrocytes exhibit a larger membrane interface with the extracellular space than neurons. These properties, together with the expression of various and numerous viral entry receptors, a relatively high rate of endocytosis, and morphological plasticity of intracellular organelles, render astrocytes important target cells in neurotropic infections. In this review, we describe factors that mediate the high susceptibility of astrocytes to viral infection and replication, including the anatomic localization of astrocytes, morphology, expression of viral entry receptors, and various forms of autophagy.

Long-chain polyphosphates inhibit type I interferon signaling and augment LPS-induced cytokine secretion in human leukocytes

Inorganic polyphosphates are evolutionarily conserved bioactive phosphate polymers found as various chain lengths in all living organisms. In mammals, polyphosphates play a vital role in the regulation of cellular metabolism, coagulation, and inflammation. Long-chain polyphosphates are found along with endotoxins in pathogenic gram-negative bacteria and can participate in bacterial virulence. We aimed to investigate whether exogenously administered polyphosphates modulate human leukocyte function in vitro by treating the cells with 3 different chain lengths of polyphosphates (P14, P100, and P700). The long-chain polyphosphates, P700, had a remarkable capacity to downregulate type I interferon signaling dose dependently in THP1-Dual cells while only a slight elevation could be observed in the NF-κB pathway with the highest dose of P700. P700 treatment decreased lipopolysaccharide-induced IFNβ transcription and secretion, reduced STAT1 phosphorylation, and downregulated subsequent interferon-stimulated gene expression in primary human peripheral blood mononuclear cells. P700 also augmented lipopolysaccharide-induced secretion of IL-1α, IL-1β, IL-4, IL-5, IL-10, and IFNγ. Furthermore, P700 has previously been reported to increase the phosphorylation of several intracellular signaling mediators, such as AKT, mTOR, ERK, p38, GSK3α/β, HSP27, and JNK pathway components, which was supported by our findings. Taken together, these observations demonstrate the extensive modulatory effects P700 has on cytokine signaling and the inhibitory effects specifically targeted to type I interferon signaling in human leukocytes.

The β6 Integrin Negatively Regulates TLR7-Mediated Epithelial Immunity via Autophagy During Influenza A Virus Infection

Integrins are essential surface receptors that sense extracellular changes to initiate various intracellular signaling cascades. The rapid activation of the epithelial-intrinsic β6 integrin during influenza A virus (IAV) infection has been linked to innate immune impairments. Yet, how β6 regulates epithelial immunity remains undefined. Here, we identify the role of β6 in mediating the Toll-like receptor 7 (TLR7) through the regulation of intracellular trafficking. We demonstrate that deletion of the β6 integrin in lung epithelial cells significantly enhances the TLR7-mediated activation of the type I interferon (IFN) response during homeostasis and respiratory infection. IAV-induced β6 facilitates TLR7 trafficking to lysosome-associated membrane protein (LAMP2a) components, leading to a reduction in endosomal compartments and associated TLR7 signaling. Our findings reveal an unappreciated role of β6-induced autophagy in influencing epithelial immune responses during influenza virus infection.

The effects of vitamin D on all-cause mortality in different diseases: an evidence-map and umbrella review of 116 randomized controlled trials

Purpose

To conduct a solid evidence by synthesizing meta-analyses and updated RCTs about the effects of vitamin D on all-cause mortality in different health conditions.

Methods

Data sources: Pubmed, Embase, Web of Science, the Cochrane Library, Google Scholar from inception until 25th April, 2022. Study selection: English-language, meta-analyses and updated RCTs assessing the relationships between vitamin D and all-cause mortality. Data synthesis: Information of study characteristics, mortality, supplementation were extracted, estimating with fixed-effects model. A Measurement Tool to Assess Systematic Reviews, Grading of Recommendations Assessment, Development and Evaluation, and funnel plot was used to assess risk of bias. Main outcomes: All-cause mortality, cancer mortality, cardiovascular disease mortality.

Results

In total of 27 meta-analyses and 19 updated RCTs were selected, with a total of 116 RCTs and 149, 865 participants. Evidence confirms that vitamin D reduces respiratory cancer mortality (RR, 0.56 [95%CI, 0.33 to 0.96]). All-cause mortality is decreased in patients with COVID-19 (RR, 0.54[95%CI, 0.33 to 0.88]) and liver diseases (RR, 0.64 [95%CI, 0.50 to 0.81]), especially in liver cirrhosis (RR, 0.63 [95%CI, 0.50 to 0.81]). As for other health conditions, such as the general health, chronic kidney disease, critical illness, cardiovascular diseases, musculoskeletal diseases, sepsis, type 2 diabetes, no significant association was found between vitamin D and all-cause mortality.

Conclusions

Vitamin D may reduce respiratory cancer mortality in respiratory cancer patients and all-cause mortality in COVID-19 and liver disorders' patients. No benefits showed in all-cause mortality after vitamin D intervention among other health conditions. The hypothesis of reduced mortality with vitamin D still requires exploration.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=252921, identifier: CRD42021252921.

USP1-Associated Factor 1 Modulates Japanese Encephalitis Virus Replication by Governing Autophagy and Interferon-Stimulated Genes

Japanese encephalitis virus (JEV) is a typical mosquito-borne flavivirus that can cause central nervous system diseases in humans and animals. Host factors attempt to limit virus replication when the viruses invade the host by using various strategies for replication. It is essential to clarify the host factors that affect the life cycle of JEV and explore its underlying mechanism. Here, we found that USP1-associated factor 1 (UAF1; also known as WD repeat-containing protein 48) modulated JEV replication. We found that JEV propagation significantly increased in UAF1-depleted Huh7 cells. Moreover, we found that knockdown of UAF1 activated cell autophagic flux in further functional analysis. Subsequently, we demonstrated that autophagy can be induced by JEV, which promotes viral replication by inhibiting interferon-stimulated gene (ISG) expression in Huh7 cells. The knockdown of UAF1 reduced ISG expression during JEV infection. To explore the possible roles of autophagy in UAF1-mediated inhibition of JEV propagation, we knocked out ATG7 to generate autophagy-deficient cells and found that depletion of UAF1 failed to promote JEV replication in ATG7 knockout cells. Moreover, in ATG7-deficient Huh7 cells, interference with UAF1 expression did not lead to the induction of autophagy. Taken together, these findings indicate that UAF1 is a critical regulator of autophagy and reveal a mechanism by which UAF1 knockdown activates autophagy to promote JEV replication. IMPORTANCE Host factors play an essential role in virus replication and pathogenesis. Although UAF1 is well known to form complexes with ubiquitin-specific proteases, little is known about the function of the UAF1 protein itself. In this study, we confirmed that UAF1 is involved in JEV replication. Notably, we discovered a novel function for UAF1 in regulating autophagy. Furthermore, we demonstrated that UAF1 modulated JEV replication through its autophagy regulation. This study is the first description of the novel function of UAF1 in regulating autophagy, and it clarifies the underlying mechanism of the antiviral effect of UAF1 against JEV. These results provide a new mechanistic insight into the functional annotation of UAF1 and provide a potential target for increasing virus production during vaccine production.

The Many Ways to Deal with STING

The stimulator of interferon genes (STING) is an adaptor protein involved in the activation of IFN-β and many other genes associated with the immune response activation in vertebrates. STING induction has gained attention from different angles such as the potential to trigger an early immune response against different signs of infection and cell damage, or to be used as an adjuvant in cancer immune treatments. Pharmacological control of aberrant STING activation can be used to mitigate the pathology of some autoimmune diseases. The STING structure has a well-defined ligand binding site that can harbor natural ligands such as specific purine cyclic di-nucleotides (CDN). In addition to a canonical stimulation by CDNs, other non-canonical stimuli have also been described, whose exact mechanism has not been well defined. Understanding the molecular insights underlying the activation of STING is important to realize the different angles that need to be considered when designing new STING-binding molecules as therapeutic drugs since STING acts as a versatile platform for immune modulators. This review analyzes the different determinants of STING regulation from the structural, molecular, and cell biology points of view.

Autophagy Receptor p62 Regulates SARS-CoV-2-Induced Inflammation in COVID-19

As autophagy can promote or inhibit inflammation, we examined autophagy-inflammation interplay in COVID-19. Autophagy markers in the blood of 19 control subjects and 26 COVID-19 patients at hospital admission and one week later were measured by ELISA, while cytokine levels were examined by flow cytometric bead immunoassay. The antiviral IFN-α and proinflammatory TNF, IL-6, IL-8, IL-17, IL-33, and IFN-γ were elevated in COVID-19 patients at both time points, while IL-10 and IL-1β were increased at admission and one week later, respectively. Autophagy markers LC3 and ATG5 were unaltered in COVID-19. In contrast, the concentration of autophagic cargo receptor p62 was significantly lower and positively correlated with TNF, IL-10, IL-17, and IL-33 at hospital admission, returning to normal levels after one week. The expression of SARS-CoV-2 proteins NSP5 or ORF3a in THP-1 monocytes caused an autophagy-independent decrease or autophagy-inhibition-dependent increase, respectively, of intracellular/secreted p62, as confirmed by immunoblot/ELISA. This was associated with an NSP5-mediated decrease in TNF/IL-10 mRNA and an ORF3a-mediated increase in TNF/IL-1β/IL-6/IL-10/IL-33 mRNA levels. A genetic knockdown of p62 mimicked the immunosuppressive effect of NSP5, and a p62 increase in autophagy-deficient cells mirrored the immunostimulatory action of ORF3a. In conclusion, the proinflammatory autophagy receptor p62 is reduced inacute COVID-19, and the balance between autophagy-independent decrease and autophagy blockade-dependent increase of p62 levels could affect SARS-CoV-induced inflammation.

Autophagy and SARS-CoV-2-Old Players in New Games

At present it is well-defined that autophagy is a fundamental process essential for cell life but its pro-viral and anti-viral role has been stated out with the COVID pandemic. However, viruses in turn have evolved diverse adaptive strategies to cope with autophagy driven host defense, either by blocking or hijacking the autophagy machinery for their own benefit. The mechanisms underlying autophagy modulation are presented in the current review which summarizes the accumulated knowledge on the crosstalk between autophagy and viral infections, with a particular emphasizes on SARS-CoV-2. The different types of autophagy related to infections and their molecular mechanisms are focused in the context of inflammation. In particular, SARS-CoV-2 entry, replication and disease pathogenesis are discussed. Models to study autophagy and to formulate novel treatment approaches and pharmacological modulation to fight COVID-19 are debated. The SARS-CoV-2-autophagy interplay is presented, revealing the complex dynamics and the molecular machinery of autophagy. The new molecular targets and strategies to treat COVID-19 effectively are envisaged. In conclusion, our finding underline the importance of development new treatment strategies and pharmacological modulation of autophagy to fight COVID-19.

Potential roles of IFI44 genes in high resistance to Vibrio in hybrids of Argopecten scallops

Vibrio bacteria are often fatal to aquatic organisms and selection of Vibrio-resistant strains is warranted for aquaculture animals. In this study, we found that hybrids between bay scallops and Peruvian scallops exhibited significantly higher resistance to Vibrio challenge, but little is available on its mechanism. Interferon induced protein 44 (IFI44), a member of the type I interferon (IFN) family, plays an important role in the IFN immune response in invertebrates, which may also participate in the resistance to Vibrio in scallops. To explore the roles of IFI44 genes in the resistance to Vibrio, they were identified and characterized in the bay scallop (designated as AiIFI44), the Peruvian scallop (designated as ApIFI44), and their reciprocal hybrids (designated as AipIFI44 and ApiIFI44, respectively). Their open reading frame (ORF) sequences were all 1434 bp, encoding 477 amino acids, but with large variations among the four genes. The AipIFI44 and ApiIFI44 exhibited higher similarity with ApIFI44 than with AiIFI44. All four genes have a TLDc structural domain with significant variations in sequences among them. Predicted differences in conformation and posttranslational modifications may lead to altered protein activity. We further demonstrated that the AiIFI44, AipIFI44 and ApiIFI44 expressed in all the tested tissues, with the highest expression in the gills and hepatopancreas. In response to Vibrio anguillarum challenge, the profile of mRNA expression of IFI44 gene differed among the bay scallops and the two hybrids. In the bay scallops, it increased at 6 h but dramatically decreased after 12-48 h. However, the mRNA expression of both AipIFI44 and ApiIFI44 decreased at 6 h but continuously increased thereafter and reached the highest value at 48 h. The results in the present study suggest the immune responds of IFI44 in scallops and it may be related to the higher resistance to Vibrio bacterial in hybrids.

Chicken CH25H inhibits ALV-J replication by promoting cellular autophagy

Autophagy plays an important role in host antiviral defense. The avian leukosis virus subgroup J (ALV-J) has been shown to inhibit autophagy while promoting viral replication. The underlying autophagic mechanisms, however, are unknown. Cholesterol 25-hydroxylase (CH25H) is a conserved interferon-stimulated gene, which converts cholesterol to a soluble antiviral factor, 25-hydroxycholesterol (25HC). In this study, we further investigated the autophagic mechanism of CH25H resistance to ALV-J in chicken embryonic fibroblast cell lines (DF1). Our results found that overexpression of CH25H and treatment with 25HC promoted the autophagic markers microtubule-associated protein 1 light chain 3 II (LC3II) and autophagy-related gene 5(ATG5), while decreased autophagy substrate p62/SQSTM1 (p62) expression in ALV-J infection DF-1 cells. Induction of cellular autophagy also reduces the levels of ALV-J gp85 and p27. ALV-J infection, on the other hand, suppresses autophagic marker protein LC3II expression. These findings suggest that CH25H-induced autophagy is a host defense mechanism that aids in ALV-J replication inhibition. In particular, CH25H interacts with CHMP4B and inhibits ALV-J infection in DF-1 cells by promoting autophagy, revealing a novel mechanism by which CH25H inhibits ALV-J infection. Although the underlying mechanisms are not completely understood, CH25H and 25HC are the first to show inhibiting ALV-J infection via autophagy.

Inborn Errors of Immunity Predisposing to Herpes Simplex Virus Infections of the Central Nervous System

Herpesvirus infections can lead to a number of severe clinical manifestations, particularly when involving the central nervous system (CNS), causing encephalitis and meningitis. However, understanding of the host factors conferring increased susceptibility to these diseases and their complications remains incomplete. Previous studies have uncovered defects in the innate Toll-like receptor 3 pathway and production of type I interferon (IFN-I) in children and adults that predispose them to herpes simplex encephalitis. More recently, there is accumulating evidence for an important role of IFN-independent cell-autonomous intrinsic mechanisms, including small nucleolar RNAs, RNA lariat metabolism, and autophagy, in restricting herpesvirus replication and conferring protection against CNS infection. The present review first describes clinical manifestations of HSV infection with a focus on neurological complications and then summarizes the host-pathogen interactions and innate immune pathways responsible for sensing herpesviruses and triggering antiviral responses and immunity. Next, we review the current landscape of inborn errors of immunity and the underlying genetic defects and disturbances of cellular immune pathways that confer increased susceptibility to HSV infection in CNS. Ultimately, we discuss some of the present outstanding unanswered questions relating to inborn errors of immunity and HSV CNS infection together with some perspectives and future directions for research in the pathogenesis of these severe diseases in humans.

Ubiquitin-specific protease 24 promotes EV71 infection by restricting K63-linked polyubiquitination of TBK1

TANK-binding kinase 1 (TBK1) is an essential protein kinase for activation of interferon regulatory factor 3 (IRF3) and induction of the type I interferons (IFN-I). Although the biochemical regulation of TBK1 activation has been studied, little is known about how enterovirus 71 (EV71) employs the deubiquitinases (DUBs) to regulate TBK1 activation for viral immune evasion. Here, we found that EV71 infection upregulated the expression of ubiquitin-specific protease 24 (USP24). Further studies revealed that USP24 physically interacted with TBK1, and can reduce K63-linked polyubiquitination of TBK1. Knockdown of USP24 upregulated TBK1 K63-linked polyubiquitination, promoted the phosphorylation and nuclear translocation of IRF3, and in turn improved IFN-I production during EV71 infection. As a consequence, USP24 knockdown dramatically inhibited EV71 infection. This study revealed USP24 as a novel regulator of TBK1 activation, which promotes the understanding of immune evasion mechanisms of EV71 and could provide a potential strategy for treatment of EV71 infection.

Autophagy inducer rapamycin treatment reduces IFN-I-mediated Inflammation and improves anti-HIV-1 T cell response in vivo

A hallmark of HIV-1 infection is chronic inflammation, even in patients treated with antiretroviral therapy (ART). Chronic inflammation drives HIV-1 pathogenesis, leading to loss of CD4+ T cells and exhaustion of antiviral immunity. Therefore, strategies to safely reduce systematic inflammation are needed to halt disease progression and restore defective immune responses. Autophagy is a cellular mechanism for disposal of damaged organelles and elimination of intracellular pathogens. Autophagy is pivotal for energy homeostasis and plays critical roles in regulating immunity. However, how it regulates inflammation and antiviral T cell responses during HIV infection is unclear. Here, we demonstrate that autophagy is directly linked to IFN-I signaling, which is a key driver of immune activation and T cell exhaustion during chronic HIV infection. Impairment of autophagy leads to spontaneous IFN-I signaling, and autophagy induction reduces IFN-I signaling in monocytic cells. Importantly, in HIV-1-infected humanized mice, autophagy inducer rapamycin treatment significantly reduced persistent IFN-I-mediated inflammation and improved antiviral T cell responses. Cotreatment of rapamycin with ART led to significantly reduced viral rebound after ART withdrawal. Taken together, our data suggest that therapeutically targeting autophagy is a promising approach to treat persistent inflammation and improve immune control of HIV replication.

Foot-and-Mouth Disease Virus: Molecular Interplays with IFN Response and the Importance of the Model

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals with a significant socioeconomic impact. One of the issues related to this disease is the ability of its etiological agent, foot-and-mouth disease virus (FMDV), to persist in the organism of its hosts via underlying mechanisms that remain to be elucidated. The establishment of a virus–host equilibrium via protein–protein interactions could contribute to explaining these phenomena. FMDV has indeed developed numerous strategies to evade the immune response, especially the type I interferon response. Viral proteins target this innate antiviral response at different levels, ranging from blocking the detection of viral RNAs to inhibiting the expression of ISGs. The large diversity of impacts of these interactions must be considered in the light of the in vitro models that have been used to demonstrate them, some being sometimes far from biological systems. In this review, we have therefore listed the interactions between FMDV and the interferon response as exhaustively as possible, focusing on both their biological effect and the study models used.

Autophagy-Associated Immunogenic Modulation and Its Applications in Cancer Therapy

Autophagy, a lysosome-mediated cellular degradation pathway, recycles intracellular components to maintain metabolic balance and survival. Autophagy plays an important role in tumor immunotherapy as a “double-edged sword” that can both promote and inhibit tumor progression. Autophagy acts on innate and adaptive immunity and interacts with immune cells to modulate tumor immunotherapy. The discovery of autophagy inducers and autophagy inhibitors also provides new insights for clinical anti-tumor therapy. However, there are also difficulties in the application of autophagy-related regulators, such as low bioavailability and the lack of efficient selectivity. This review focuses on autophagy-related immunogenic regulation and its application in cancer therapy.

Autophagy Modulators in Coronavirus Diseases: A Double Strike in Viral Burden and Inflammation

Coronaviruses are the etiologic agents of several diseases. Coronaviruses of critical medical importance are characterized by highly inflammatory pathophysiology, involving severe pulmonary impairment and infection of multiple cell types within the body. Here, we discuss the interplay between coronaviruses and autophagy regarding virus life cycle, cell resistance, and inflammation, highlighting distinct mechanisms by which autophagy restrains inflammatory responses, especially those involved in coronavirus pathogenesis. We also address different autophagy modulators available and the rationale for drug repurposing as an attractive adjunctive therapy. We focused on pharmaceuticals being tested in clinical trials with distinct mechanisms but with autophagy as a common target. These autophagy modulators act in cell resistance to virus infection and immunomodulation, providing a double-strike to prevent or treat severe disease development and death from coronaviruses diseases.

Combined Effects of Fludarabine and Interferon Alpha on Autophagy Regulation Define the Phase of Cell Survival and Promotes Responses in LLC-MK2 and K562 Cells

Autophagy is a known mechanism of cells under internal stress that regulates cellular function via internal protein recycling and the cleaning up of debris, leading to healthy live cells. However, the stimulation of autophagy by external factors such as chemical compounds or viral infection mostly tends to induce apoptosis/cell death. This study hypothesizes that manipulation of the autophagy mechanism to the pro-cell survival and/or decreased pro-viral niche can be a strategy for effective antiviral and anticancer treatment. Cells susceptible to viral infection, namely LLC-MK2, normal monkey epithelium, and K562, human immune-related lymphocyte, which is also a cancer cell line, were treated with fludarabine nucleoside analog (Fdb), interferon alpha (IFN-α), and a combination of Fdb and IFN-α, and then were evaluated for signs of adaptive autophagy and STAT1 antiviral signaling by Western blotting and immunolabeling assays. The results showed that the low concentration of Fdb was able to activate an autophagy response in both cell types, as demonstrated by the intense immunostaining of LC3B foci in the autophagosomes of living cells. Treatment with IFN-α (10 U/mL) showed no alteration in the initiator of mTOR autophagy but dramatically increased the intracellular STAT1 signaling molecules in both cell types. Although in the combined Fdb and IFN-α treatment, both LLC-MK2 and K562 cells showed only slight changes in the autophagy-responsive proteins p-mTOR and LC3B, an adaptive autophagy event was clearly shown in the autophagosome of the LLC-MK2 cell, suggesting the survival phase of the normal cell. The combined effect of Fdb and IFN-α treatment on the antiviral response was identified by the level of activation of the STAT1 antiviral marker. Significantly, the adaptive autophagy mediated by Fdb was able to suppress the IFN-α-mediated pSTAT1 signaling in both cell types to a level that is appropriate for cellular function. It is concluded that the administration of an appropriate dose of Fdb and IFN-α in combination is beneficial for the treatment of some types of cancer and viral infection.

Dying by fire: noncanonical functions of autophagy proteins in neuroinflammation and neurodegeneration

Neuroinflammation and neurodegeneration are key components in the establishment and progression of neurodegenerative diseases including Alzheimer's Disease (AD). Over the past decade increasing evidence is emerging for the use of components of the canonical autophagy machinery in pathways that are characterized by LC3 lipidation yet are distinct from traditional macro-autophagy. One such pathway that utilizes components of the autophagy machinery to target LC3 to endosomes, a process termed LC3-associated endocytosis (LANDO), has recently been identified and regulates neuroinflammation. Abrogation of LANDO in microglia cells results in a propensity for elevated neuroinflammatory cytokine production. Using the well-established 5xFAD model of AD to interrogate neuroinflammatory regulation, impairment of LANDO through deletion of a key upstream regulator Rubicon or other downstream autophagy components, exacerbated disease onset and severity, while deletion of microglial autophagy alone had no measurable effect. Mice presented with robust deposition of the neurotoxic AD protein β-amyloid (Aβ), microglial activation and inflammatory cytokine production, tau phosphorylation, and aggressive neurodegeneration culminating in severe memory impairment. LANDO-deficiency impaired recycling of receptors that recognize Aβ, including TLR4 and TREM2. LANDO-deficiency alone through deletion of the WD-domain of the autophagy protein ATG16L, revealed a role for LANDO in the spontaneous establishment of age-associated AD. LANDO-deficient mice aged to 2 years presented with advanced AD-like disease and pathology correlative to that observed in human AD patients. Together, these studies illustrate an important role for microglial LANDO in regulating CNS immune activation and protection against neurodegeneration. New evidence is emerging that demonstrates a putative linkage between pathways such as LANDO and cell death regulation via apoptosis and possibly necroptosis. Herein, we provide a review of the use of the autophagy machinery in non-canonical mechanisms that alter immune regulation and could have significant impact in furthering our understanding of not only CNS diseases like AD, but likely beyond.

Hepatitis C virus and intracellular antiviral response

To establish successful infection in cells, it is essential for hepatitis C virus (HCV) to overcome intracellular antiviral responses. The host cell mechanism that fights against the virus culminates in the production of interferons (IFNs), IFN-stimulated genes (ISGs) and pro-inflammatory cytokines as well as the induction of autophagy and apoptosis. HCV has developed multiple means to disrupt the host signaling pathways that lead to these antiviral responses. HCV impedes signaling pathways initiated by pattern-recognition receptors (PRRs), usurps and uses the antiviral autophagic response to enhance its replication, alters mitochondrial dynamics and metabolism to prevent cell death and attenuate IFN response, and dysregulates inflammasomal response to cause IFN resistance and immune tolerance. These effects of HCV allow HCV to successful replicate and persist in its host cells.

Trichoderma stromaticum spores induce autophagy and downregulate inflammatory mediators in human peripheral blood-derived macrophages

•

T. stromaticum biocontrol agent induces autophagy, up-regulating autophagy-related genes

•

T. stromaticum modulates expression of micro RNAs that control imune response

•

T. stromaticum dow-nregulates expression of TLR2, TLR4, CLEC7A, NLRP3, IL-10, IL1β and IL18

•

T. stromaticum modulates ROS production

Trichoderma spp. are usually considered safe and normally used as biocontrol and biofertilization. Safety for human health is evaluated by several tests that detect various effects such as allergenicity, toxicity, infectivity, and pathogenicity. However, they do not evaluate the effects of the agent upon the immune system. The aim of this study was to investigate the interaction between T. stromaticum spores and mammalian cells to assess the immunomodulatory potential of the spores of this fungus. First, mouse macrophage cell line J774 and human macrophages were exposed to fungal spores and analyzed for structural features, through scanning and transmission electron microscopy. Then, various analysis were performed in human macrophages as to their effect in some functional and molecular aspects of the immune system through immunocytochemistry, flow cytometry and gene expression assays. We demonstrated that T. stromaticum spores induces autophagy and autophagy-related genes (ATGs) and downmodulate inflammatory mediators, including ROS, NLRP3, the cytokines IL-1β, IL-18, IL-12 and IL-10, as well as TLR2, TLR4, miR-146b and miR-155, which may lead to an augmented susceptibility to pathogens. Our study shows the extension of damages the biofungicide Tricovab® can cause in the innate immune response. Further studies are necessary to elucidate other innate and adaptive immune responses and, consequently, the safety of this fungus when in contact with humans.

Selective autophagy controls the stability of TBK1 via NEDD4 to balance host defense

As a core kinase of antiviral immunity, the activity and stability of TANK-binding kinase 1 (TBK1) is tightly controlled by multiple post-translational modifications. Although it has been demonstrated that TBK1 stability can be regulated by ubiquitin-dependent proteasome pathway, it is unclear whether another important protein degradation pathway, autophagosome pathway, can specifically affect TBK1 degradation by cargo receptors. Here we report that E3 ubiquitin ligase NEDD4 functions as a negative regulator of type I interferon (IFN) signaling by targeting TBK1 for degradation at the late stage of viral infection, to prevent the host from excessive immune response. Mechanically NEDD4 catalyzes the K27-linked poly-ubiquitination of TBK1 at K344, which serves as a recognition signal for cargo receptor NDP52-mediated selective autophagic degradation. Taken together, our study reveals the regulatory role of NEDD4 in balancing TBK1-centered type I IFN activation and provides insights into the crosstalk between selective autophagy and antiviral signaling.

RNA-dependent protein kinase is required for interferon-γ-induced autophagy in MG63 osteosarcoma cells

Osteosarcoma is a bone tumor that mainly affects children and adolescents. Interferons (IFNs) have been shown to exert antitumor effects in osteosarcoma cells, although the molecular mechanisms have not been fully realized. We investigated IFN-γ actions on osteosarcoma cells. Our results show that IFN-γ induces the accumulation of autophagosomes in osteosarcoma cells. IFN-γ treatment leads to the conversion of autophagy marker light chain 3 (LC3)-I to LC3-II in osteosarcoma cells, and this conversion is accompanied by puncta formation. Also, IFN-γ-mediated induction of autophagosome formation and autophagic flux require RNA-dependent protein kinase (PKR) activity. In addition, our findings show that IFN-γ-mediated osteosarcoma cell death is not dependent on PKR. Our study suggests that IFN-γ has differential effects that lead to induction of cell death and autophagy in osteosarcoma cells. Further evaluation of the IFN-γ-mediated molecular mechanism could lead to improved understanding of and targeted treatment strategies for osteosarcoma.

Putative Role of Vitamin D for COVID-19 Vaccination

Severe acute respiratory syndrome coronavirus 2 is a new, highly pathogenic virus that has recently elicited a global pandemic called the 2019 coronavirus disease (COVID-19). COVID-19 is characterized by significant immune dysfunction, which is caused by strong but unregulated innate immunity with depressed adaptive immunity. Reduced and delayed responses to interferons (IFN-I/IFN-III) can increase the synthesis of proinflammatory cytokines and extensive immune cell infiltration into the airways, leading to pulmonary disease. The development of effective treatments for severe COVID-19 patients relies on our knowledge of the pathophysiological components of this imbalanced innate immune response. Strategies to address innate response factors will be essential. Significant efforts are currently underway to develop vaccines against SARS-CoV-2. COVID-19 vaccines, such as inactivated DNA, mRNA, and protein subunit vaccines, have already been applied in clinical use. Various vaccines display different levels of effectiveness, and it is important to continue to optimize and update their composition in order to increase their effectiveness. However, due to the continuous emergence of variant viruses, improving the immunity of the general public may also increase the effectiveness of the vaccines. Many observational studies have demonstrated that serum levels of vitamin D are inversely correlated with the incidence or severity of COVID-19. Extensive evidence has shown that vitamin D supplementation could be vital in mitigating the progression of COVID-19 to reduce its severity. Vitamin D defends against SARS-CoV-2 through a complex mechanism through interactions between the modulation of innate and adaptive immune reactions, ACE2 expression, and inhibition of the renin-angiotensin system (RAS). However, it remains unclear whether Vit-D also plays an important role in the effectiveness of different COVID-19 vaccines. Based on analysis of the molecular mechanism involved, we speculated that vit-D, via various immune signaling pathways, plays a complementary role in the development of vaccine efficacy.

Autophagy impairment by African swine fever virus

African swine fever is a devastating disease of domestic swine and wild boar caused by a large double-stranded DNA virus that encodes for more than 150 open reading frames. There is no licensed vaccine for the disease and the most promising current candidates are modified live viruses that have been attenuated by deletion of virulence factors. Like many viruses African swine fever virus significantly alters the host cell machinery to benefit its replication and viral genes that modify host pathways represent promising targets for development of gene deleted vaccines. Autophagy is an important cellular pathway that is involved in cellular homeostasis, innate and adaptive immunity and therefore is manipulated by a number of different viruses. Autophagy is regulated by a complex protein cascade and here we show that African swine fever virus can block formation of autophagosomes, a critical functional step of the autophagy pathway through at least two different mechanisms. Interestingly this does not require the A179L gene that has been shown to interact with Beclin-1, an important autophagy regulator.

Inhibition of herpes simplex virus 1 by cepharanthine via promoting cellular autophagy through up-regulation of STING/TBK1/P62 pathway

Cepharanthine (CEP), a naturally occurring isoquinoline alkaloid extracted from the genus CEP of the Tetrandrine family, was reported to possess many biological activities such as anti-inflammatory, antitumor, antiviral, and immune-enhancing effects. Nevertheless, the underlying mechanisms of CEP against herpes simplex virus type 1 (HSV-1) are still elusive. In this study, we explored the anti-HSV effects and mechanisms of CEP in vitro. The results showed that CEP possessed a strong inhibitory effect against HSV-1 infection with the TC50 of 5.4 μg/mL, the IC50 of 0.835 μg/mL, and the TI of 6.47. Most importantly, CEP could promote the phosphorylation of STING, TBK1, and P62 and the expression of LC3II without induction of interferon by directly targeting the STING/TBK1/P62 signaling pathways. Electron microscopy showed that autophagy induced by CEP could degrade viral particles and cellular components. RT-PCR results revealed that a sharp reduction of large numbers of virus gene transcription in 16 h after CEP treatment. Furthermore, CEP also reduced the HSV-1 gB and gC transcription. In conclusion, one of the effects of CEP was to promote interferon-independent autophagy through STING mediated signaling.

Antiviral Activity of Chrysin against Influenza Virus Replication via Inhibition of Autophagy

Influenza viruses cause respiratory infections in humans and animals, which have high morbidity and mortality rates. Although several drugs that inhibit viral neuraminidase are used to treat influenza infections, the emergence of resistant viruses necessitates the urgent development of new antiviral drugs. Chrysin (5,7-dihydroxyflavone) is a natural flavonoid that exhibits antiviral activity against enterovirus 71 (EV71) by inhibiting viral 3C protease activity. In this study, we evaluated the antiviral activity of chrysin against influenza A/Puerto Rico/8/34 (A/PR/8). Chrysin significantly inhibited A/PR/8-mediated cell death and the replication of A/PR/8 at concentrations up to 2 μM. Viral hemagglutinin expression was also markedly decreased by the chrysin treatment in A/PR/8-infected cells. Through the time course experiment and time-of-addition assay, we found that chrysin inhibited viral infection at the early stages of the replication cycle. Additionally, the nucleoprotein expression of A/PR/8 in A549 cells was reduced upon treatment with chrysin. Regarding the mechanism of action, we found that chrysin inhibited autophagy activation by increasing the phosphorylation of mammalian target of rapamycin (mTOR). We also confirmed a decrease in LC3B expression and LC3-positive puncta levels in A/PR/8-infected cells. These results suggest that chrysin exhibits antiviral activity by activating mTOR and inhibiting autophagy to inhibit the replication of A/PR/8 in the early stages of infection.

CVB3-Mediated Mitophagy Plays an Important Role in Viral Replication via Abrogation of Interferon Pathways

Coxsackievirus B3 (CVB3) is a common enterovirus that causes systemic inflammatory diseases, such as myocarditis, meningitis, and encephalitis. CVB3 has been demonstrated to subvert host cellular responses via autophagy to support viral replication in neural stem cells. Mitophagy, a specialized form of autophagy, contributes to mitochondrial quality control via degrading damaged mitochondria. Here, we show that CVB3 infection induces mitophagy in human neural progenitor cells, HeLa and H9C2 cardiomyocytes. In particular, CVB3 infection triggers mitochondrial fragmentation, loss of mitochondrial membrane potential, and Parkin/LC3 translocation to the mitochondria. Rapamycin or carbonyl cyanide m-chlorophenyl hydrazone (CCCP) treatment led to increased CVB3 RNA copy number in a dose-dependent manner, suggesting enhanced viral replication via autophagy/mitophagy activation, whereas knockdown of PTEN-induced putative kinase protein 1(PINK1) led to impaired mitophagy and subsequent reduction in viral replication. Furthermore, CCCP treatment inhibits the interaction between mitochondrial antiviral signaling protein (MAVS) and TANK-binding kinase 1(TBK1), thus contributing to the abrogation of type I and III interferon (IFN) production, suggesting that mitophagy is essential for the inhibition of interferon signaling. Our findings suggest that CVB3-mediated mitophagy suppresses IFN pathways by promoting fragmentation and subsequent sequestration of mitochondria by autophagosomes.

PGE2 displays immunosuppressive effects during human active tuberculosis

Prostaglandin E2 (PGE2), an active lipid compound derived from arachidonic acid, regulates different stages of the immune response of the host during several pathologies such as chronic infections or cancer. In fact, manipulation of PGE2 levels was proposed as an approach for countering the Type I IFN signature of tuberculosis (TB). However, very limited information regarding the PGE2 pathway in patients with active TB is currently available. In the present work, we demonstrated that PGE2 exerts a potent immunosuppressive action during the immune response of the human host against Mycobacterium tuberculosis (Mtb) infection. Actually, we showed that PGE2 significantly reduced the surface expression of several immunological receptors, the lymphoproliferation and the production of proinflammatory cytokines. In addition, PGE2 promoted autophagy in monocytes and neutrophils cultured with Mtb antigens. These results suggest that PGE2 might be attenuating the excessive inflammatory immune response caused by Mtb, emerging as an attractive therapeutic target. Taken together, our findings contribute to the knowledge of the role of PGE2 in the human host resistance to Mtb and highlight the potential of this lipid mediator as a tool to improve anti-TB treatment.

Immunological Aspects of SARS-CoV-2 Infection and the Putative Beneficial Role of Vitamin-D

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is still an ongoing global health crisis. Immediately after the inhalation of SARS-CoV-2 viral particles, alveolar type II epithelial cells harbor and initiate local innate immunity. These particles can infect circulating macrophages, which then present the coronavirus antigens to T cells. Subsequently, the activation and differentiation of various types of T cells, as well as uncontrollable cytokine release (also known as cytokine storms), result in tissue destruction and amplification of the immune response. Vitamin D enhances the innate immunity required for combating COVID-19 by activating toll-like receptor 2. It also enhances antimicrobial peptide synthesis, such as through the promotion of the expression and secretion of cathelicidin and β-defensin; promotes autophagy through autophagosome formation; and increases the synthesis of lysosomal degradation enzymes within macrophages. Regarding adaptive immunity, vitamin D enhances CD4+ T cells, suppresses T helper 17 cells, and promotes the production of virus-specific antibodies by activating T cell-dependent B cells. Moreover, vitamin D attenuates the release of pro-inflammatory cytokines by CD4+ T cells through nuclear factor κB signaling, thereby inhibiting the development of a cytokine storm. SARS-CoV-2 enters cells after its spike proteins are bound to angiotensin-converting enzyme 2 (ACE2) receptors. Vitamin D increases the bioavailability and expression of ACE2, which may be responsible for trapping and inactivating the virus. Activation of the renin-angiotensin-aldosterone system (RAS) is responsible for tissue destruction, inflammation, and organ failure related to SARS-CoV-2. Vitamin D inhibits renin expression and serves as a negative RAS regulator. In conclusion, vitamin D defends the body against SARS-CoV-2 through a novel complex mechanism that operates through interactions between the activation of both innate and adaptive immunity, ACE2 expression, and inhibition of the RAS system. Multiple observation studies have shown that serum concentrations of 25 hydroxyvitamin D are inversely correlated with the incidence or severity of COVID-19. The evidence gathered thus far, generally meets Hill's causality criteria in a biological system, although experimental verification is not sufficient. We speculated that adequate vitamin D supplementation may be essential for mitigating the progression and severity of COVID-19. Future studies are warranted to determine the dosage and effectiveness of vitamin D supplementation among different populations of individuals with COVID-19.

MiR-139 Induces an Interferon-β Response in Prostate Cancer Cells by Binding to RIG-1

BACKGROUND

We previously identified a panel of five miRNAs associated with prostate cancer recurrence and metastasis. Expression of one of the down-regulated miRNAs, miR-139-5p, was significantly associated with a lower incidence of biochemical recurrence and metastasis. Transcriptome profiling of miR-139-expressing prostate cancer cells revealed up-regulation of genes involved in interferon (IFN) stimulation. The association between miR-139 and IFN-β was further explored in this study.

MATERIALS AND METHODS

We examined miR-139 transfected PC3, Du145 and LNCaP cells and the associated IFN response by transcriptome sequencing, immunoblotting and pulldown assays.

RESULTS

Treatment of prostate cancer cells by miR-139 resulted in the up-regulation of IFN-related genes. Specifically, miR-139 induced expression of the IFN-β protein. The ability of miR-139 to induce IFN-β was due to its binding to RIG-1 and the induction of IFN-related genes was found to be dependent on RIG-1 expression.

CONCLUSION

miR-139 acts as an immune agonist of RIG-1 to enhance IFN-β response in prostate cancer cells.

ATG16L1 functions in cell homeostasis beyond autophagy

Atg16-like (ATG16L) proteins were identified in higher eukaryotes for their resemblance to Atg16, a yeast protein previously characterized as a subunit of the Atg12-Atg5/Atg16 complex. In yeast, this complex catalyzes the lipidation of Atg8 on pre-autophagosomal structures and is therefore required for the formation of autophagosomes. In higher eukaryotes, ATG16L1 is also almost exclusively present as part of an ATG12-ATG5/ATG16L1 complex and has the same essential function in autophagy. However, ATG16L1 is three times bigger than Atg16. It displays, in particular, a carboxy-terminal extension, including a WD40 domain, which provides a platform for interaction with a variety of proteins, and allows for the recruitment of the ATG12-ATG5/ATG16L1 complex to membranes under different contexts. Furthermore, detailed analyses at the cellular level have revealed that some of the ATG16L1-driven activities are independent of the lipidation reaction catalyzed by the ATG12-ATG5/ATG16L1 complex. At the organ level, the use of mice that are hypomorphic for Atg16l1, or with cell-specific ablation of its expression, revealed a large panel of consequences of ATG16L1 dysfunctions. In this review, we recapitulate the current knowledge on ATG16L1 expression and functions. We emphasize, in particular, how it broadly acts as a brake on inflammation, thereby contributing to maintaining cell homeostasis. We also report on independent studies that converge to show that ATG16L1 is an important player in the regulation of intracellular traffic. Overall, autophagy-independent functions of ATG16L1 probably account for more of the phenotypes associated with ATG16L1 deficiencies than currently appreciated.

Autophagy in Viral Development and Progression of Cancer

Autophagy is a complex degradative process by which eukaryotic cells capture cytoplasmic components for subsequent degradation through lysosomal hydrolases. Although this catabolic process can be triggered by a great variety of stimuli, action in cells varies according to cellular context. Autophagy has been previously linked to disease development modulation, including cancer. Autophagy helps suppress cancer cell advancement in tumor transformation early stages, while promoting proliferation and metastasis in advanced settings. Oncoviruses are a particular type of virus that directly contribute to cell transformation and tumor development. Extensive molecular studies have revealed complex ways in which autophagy can suppress or improve oncovirus fitness while still regulating viral replication and determining host cell fate. This review includes recent advances in autophagic cellular function and emphasizes its antagonistic role in cancer cells.