Pseudorabies virus gM and its homologous proteins in herpesviruses induce mitochondria-related apoptosis involved in viral pathogenicity.

Apoptosis is a critical host antiviral defense mechanism. But many viruses have evolved multiple strategies to manipulate apoptosis and escape host antiviral immune responses. Herpesvirus infection regulated apoptosis; however, the underlying molecular mechanisms have not yet been fully elucidated. Hence, the present study aimed to study the relationship between herpesvirus infection and apoptosis in vitro and in vivo using the pseudorabies virus (PRV) as the model virus. We found that mitochondria-dependent apoptosis was induced by PRV gM, a late protein encoded by PRV UL10, a virulence-related gene involved in enhancing PRV pathogenicity. Mechanistically, gM competitively combines with BCL-XL to disrupt the BCL-XL-BAK complex, resulting in BCL-2-antagonistic killer (BAK) oligomerization and BCL-2-associated X (BAX) activation, which destroys the mitochondrial membrane potential and activates caspase-3/7 to trigger apoptosis. Interestingly, similar apoptotic mechanisms were observed in other herpesviruses (Herpes Simplex Virus-1 [HSV-1], human cytomegalovirus [HCMV], Equine herpesvirus-1 [EHV-1], and varicella-zoster virus [VZV]) driven by PRV gM homologs. Compared with their parental viruses, the pathogenicity of PRV-ΔUL10 or HSV-1-ΔUL10 in mice was reduced with lower apoptosis and viral replication, illustrating that UL10 is a key virulence-related gene in PRV and HSV-1. Consistently, caspase-3 deletion also diminished the replication and pathogenicity of PRV and HSV-1 in vitro and in mice, suggesting that caspase-3-mediated apoptosis is closely related to the replication and pathogenicity of PRV and HSV-1. Overall, our findings firstly reveal the mechanism by which PRV gM and its homologs in several herpesviruses regulate apoptosis to enhance the viral replication and pathogenicity, and the relationship between gM-mediated apoptosis and herpesvirus pathogenicity suggests a promising approach for developing attenuated live vaccines and therapy for herpesvirus-related diseases.

The emerging roles of MARCH8 in viral infections: A double-edged Sword.

The host cell membrane-associated RING-CH 8 protein (MARCH8), a member of the E3 ubiquitin ligase family, regulates intracellular turnover of many transmembrane proteins and shows potent antiviral activities. Generally, 2 antiviral modes are performed by MARCH8. On the one hand, MARCH8 catalyzes viral envelope glycoproteins (VEGs) ubiquitination and thus leads to their intracellular degradation, which is the cytoplasmic tail (CT)-dependent (CTD) mode. On the other hand, MARCH8 traps VEGs at some intracellular compartments (such as the trans-Golgi network, TGN) but without inducing their degradation, which is the cytoplasmic tail-independent (CTI) mode, by which MARCH8 hijacks furin, a cellular proprotein convertase, to block VEGs cleavage. In addition, the MARCH8 C-terminal tyrosine-based motif (TBM) 222YxxL225 also plays a key role in its CTI antiviral effects. In contrast to its antiviral potency, MARCH8 is occasionally hijacked by some viruses and bacteria to enhance their invasion, indicating a duplex role of MARCH8 in host pathogenic infections. This review summarizes MARCH8's antiviral roles and how viruses evade its restriction, shedding light on novel antiviral therapeutic avenues.

When DNA-damage responses meet innate and adaptive immunity.

When cells proliferate, stress on DNA replication or exposure to endogenous or external insults frequently results in DNA damage. DNA-Damage Response (DDR) networks are complex signaling pathways used by multicellular organisms to prevent DNA damage. Depending on the type of broken DNA, the various pathways, Base-Excision Repair (BER), Nucleotide Excision Repair (NER), Mismatch Repair (MMR), Homologous Recombination (HR), Non-Homologous End-Joining (NHEJ), Interstrand Crosslink (ICL) repair, and other direct repair pathways, can be activated separately or in combination to repair DNA damage. To preserve homeostasis, innate and adaptive immune responses are effective defenses against endogenous mutation or invasion by external pathogens. It is interesting to note that new research keeps showing how closely DDR components and the immune system are related. DDR and immunological response are linked by immune effectors such as the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway. These effectors act as sensors of DNA damage-caused immune response. Furthermore, DDR components themselves function in immune responses to trigger the generation of inflammatory cytokines in a cascade or even trigger programmed cell death. Defective DDR components are known to disrupt genomic stability and compromise immunological responses, aggravating immune imbalance and leading to serious diseases such as cancer and autoimmune disorders. This study examines the most recent developments in the interaction between DDR elements and immunological responses. The DDR network's immune modulators' dual roles may offer new perspectives on treating infectious disorders linked to DNA damage, including cancer, and on the development of target immunotherapy.

When DNA damage responses meet tumor immunity: From mechanism to therapeutic opportunity.

DNA damage is a prevalent phenomenon in the context of cancer progression. Evidence suggests that DNA damage responses (DDR) are pivotal in overcoming tumor immune evasion. Alternatively, traditional radiotherapy and chemotherapy operate by inducing DNA damage, consequently stimulating the immune system to target tumors. The intricate interplay between signaling pathways involved in DDR and immune activation underscores the significance of considering both factors in developing improved immunotherapies. By delving deeper into the mechanisms underlying immune activation brought on by DNA damage, it becomes possible to identify novel treatment approaches that boost the anticancer immune response while minimizing undesirable side effects. This review explores the mechanisms behind DNA damage-induced antitumor immune responses, the importance of DNA damage in antitumor immunity, and potential therapeutic approaches for cancer immunotherapy targeting DDR. Additionally, we discuss the challenges of combination therapy and strategies for integrating DNA damage-targeting therapies with current cancer immunotherapy. In summary, this review highlights the critical role of DNA damage in tumor immunology, underscoring the potential of DDR inhibitors as promising therapeutic modalities for cancer treatment.

Human MARCH1, 2, and 8 block Ebola virus envelope glycoprotein cleavage via targeting furin P domain.

Membrane-associated RING-CH (MARCH) family proteins were recently reported to inhibit viral replication through multiple modes. Previous work showed that human MARCH8 blocked Ebola virus (EBOV) glycoprotein (GP) maturation. Our study here demonstrates that human MARCH1 and MARCH2 share a similar pattern to MARCH8 in restricting EBOV GP-pseudotyped viral infection. Human MARCH1 and MARCH2 retain EBOV GP at the trans-Golgi network, reduce its cell surface display, and impair EBOV GP-pseudotyped virions infectivity. Furthermore, we uncover that the host proprotein convertase furin could interact with human MARCH1/2 and EBOV GP intracellularly. Importantly, the furin P domain is verified to be recognized by MARCH1/2/8, which is critical for their blocking activities. Besides, bovine MARCH2 and murine MARCH1 also impair EBOV GP proteolytic processing. Altogether, our findings confirm that MARCH1/2 proteins of different mammalian origins showed a relatively conserved feature in blocking EBOV GP cleavage, which could provide clues for subsequent MARCHs antiviral studies and may facilitate the development of novel strategies to antagonize enveloped virus infection.

SARS-CoV-2 and dengue virus co-infection: Epidemiology, pathogenesis, diagnosis, treatment, and management.

SARS-CoV-2 and dengue virus co-infection cases have been on the rise in dengue-endemic regions as coronavirus disease 2019 (COVID-19) spreads over the world, posing a threat of a co-epidemic. The risk of comorbidity in co-infection cases is greater than that of a single viral infection, which is a cause of concern. Although the pathophysiologies of the two infections are different, the viruses have comparable effects within the body, resulting in identical clinical symptoms in the case of co-infection, which adds to the complexity. Overlapping symptoms and laboratory features make proper differentiation of the infections important. However, specific biomarkers provide precise results that can be utilised to diagnose and treat a co-infection, whether it is simply COVID-19, dengue, or a co-infection. Though their treatment is distinguished, it becomes more complicated in circumstances of co-infection. As a result, regardless of whatever infection the first symptom points to, confirmation diagnosis of both COVID-19 and dengue should be mandatory, particularly in dengue-endemic regions, to prevent health deterioration in individuals treated for a single infection. There is still a scarcity of concise literature on the epidemiology, pathophysiology, diagnosis, therapy, and management of SARS-CoV-2 and dengue virus co-infection. The epidemiology of SARS-CoV-2 and dengue virus co-infection, the mechanism of pathogenesis, and the potential impact on patients are summarised in this review. The possible diagnosis with biomarkers, treatment, and management of the SARS-CoV-2 and dengue viruses are also discussed. This review will shed light on the appropriate diagnosis, treatment, and management of the patients suffering from SARS-CoV-2 and dengue virus co-infection.

When Poly(A) Binding Proteins Meet Viral Infections, Including SARS-CoV-2.

Viruses have evolved diverse strategies to hijack the cellular gene expression system for their replication. The poly(A) binding proteins (PABPs), a family of critical gene expression factors, are viruses' common targets. PABPs act not only as a translation factor but also as a key factor of mRNA metabolism. During viral infections, the activities of PABPs are manipulated by various viruses, subverting the host translation machinery or evading the cellular antiviral defense mechanism. Viruses harness PABPs by modifying their stability, complex formation with other translation initiation factors, or subcellular localization to promote viral mRNAs translation while shutting off or competing with host protein synthesis. For the past decade, many studies have demonstrated the PABPs' roles during viral infection. This review summarizes a comprehensive perspective of PABPs' roles during viral infection and how viruses evade host antiviral defense through the manipulations of PABPs.

NLRC4 promotes the cGAS-STING signaling pathway by facilitating CBL-mediated K63-linked polyubiquitination of TBK1.

TANK-binding kinase 1 (TBK1) is crucial in producing type Ⅰ interferons (IFN-Ⅰ) that play critical functions in antiviral innate immunity. The tight regulation of TBK1, especially its activation, is very important. Here we identify NLRC4 as a positive regulator of TBK1. Ectopic expression of NLRC4 facilitates the activation of the IFN-ß promoter, the mRNA levels of IFN-ß, ISG54, and ISG56, and the nuclear translocation of interferon regulatory factor 3 induced by cGAS and STING. Consistently, under herpes simplex virus-1 (HSV-1) infection, knockdown or knockout of NLRC4 in BJ cells and primary peritoneal macrophages from Nlrc4-deficient (Nlrc4-/- ) mice show attenuated Ifn-ß, Isg54, and Isg56 mRNA transcription, TBK1 phosphorylation, and augmented viral replications. Moreover, Nlrc4-/- mice show higher mortality upon HSV-1 infection. Mechanistically, NLRC4 facilitates the interaction between TBK1 and the E3 ubiquitin ligase CBL to enhance the K63-linked polyubiquitination of TBK1. Our study elucidates a previously uncharacterized function for NLRC4 in upregulating the cGAS-STING signaling pathway and antiviral innate immunity.

Analysis of long noncoding RNAs and messenger RNAs expression profiles in the hearts of mice with acute viral myocarditis.

Acute viral myocarditis (AVMC) is a common acute myocardial inflammation caused by viral infections, which can lead to severe cardiac dysfunction. Several long noncoding RNAs (lncRNAs) with aberrant expression have been identified in the pathogenesis of AVMC. However, the expression profiles and functions of lncRNAs in AVMC have not been fully elucidated. In the present study, we constructed AVMC mouse models by intraperitoneal injection of coxsackievirus B3 (CVB3) and performed RNA sequencing (RNA-seq) on heart tissues to investigate the differences in lncRNAs and messenger RNAs (mRNAs) expression profiles. Based on the cutoff criteria of adjusted p-values (padj) <0.05 and |log2FoldChange| >1, a total of 1122 differentially expressed lncRNAs (DElncRNAs) and 3186 differentially expressed mRNAs (DEmRNAs) were screened, including 734 upregulated and 388 downregulated lncRNAs, 1821 upregulated and 1365 downregulated mRNAs. RT-qPCR analysis validated that the expression patterns of 12 randomly selected genes (6 DElncRNAs and 6 DEmRNAs) were highly consistent with those in RNA-seq, proving the reliability of the RNA-seq data. Then, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that differentially expressed genes were mainly involved in metabolic and immune-related processes. Furthermore, co-expression networks between DElncRNAs and DEmRNAs in cytokine-cytokine receptor interaction, MAPK signaling pathway, and PI3K-Akt signaling pathway were constructed to study the molecular interactions of these molecules. Our study, for the first time, reveals the expression profiles of lncRNAs and mRNAs associated with AVMC, which may shed light on the roles of lncRNAs in disease pathogenesis and aid in discovering new therapeutic targets.

SARS-CoV-2 ORF7a blocked autophagy flux by intervening in the fusion between autophagosome and lysosome to promote viral infection and pathogenesis.

The coronavirus disease 2019 (COVID-19) continues to pose a major threat to public health worldwide. Although many studies have clarified the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection process, the underlying mechanisms of viral invasion and immune evasion were still unclear. This study focused on SARS-CoV-2 ORF7a (open reading frame-7a), one of the essential open reading frames (ORFs) in infection and pathogenesis. First, by analyzing its physical and chemical characteristics, SARS-CoV-2 ORF7a is an unstable hydrophobic transmembrane protein. Then, the ORF7a transmembrane domain three-dimensional crystal structure model was predicted and verified. SARS-CoV-2 ORF7a localized in the endoplasmic reticulum and participated in the autophagy-lysosome pathway via interacting with p62. In addition, we elucidated the underlying molecular mechanisms by which ORF7a intercepted autophagic flux, promoted double membrane vesicle formation, and evaded host autophagy-lysosome degradation and antiviral innate immunity. This study demonstrated that ORF7a could be a therapeutic target, and Glecaprevir may be a potential drug against SARS-CoV-2 by targeting ORF7a. A comprehensive understanding of ORF7a's functions may contribute to developing novel therapies and clinical drugs against COVID-19.

The short and long-term impact of nonpharmaceutical interventions on the prevalence of varicella in Xi'an during the COVID-19 pandemic.

Varicella is a highly prevalent infectious disease with a similar transmission pathway to coronavirus disease 2019 (COVID-19). In the context of the COVID-19 pandemic, anti-COVID-19 nonpharmaceutical interventions (NPIs) have been implemented to prevent the spread of the infection. This study aims to analyze varicella's epidemiological characteristics and further investigate the effect of anti-COVID-19 NPIs on varicella in Xi'an, northwestern China. Based on the varicella surveillance data, search engine indices, meteorological factors from 2011 to 2021 in Xi'an, and different levels of emergency response to COVID-19 during the pandemic, we applied Bayesian Structural Time Series models and interrupted time series analysis to predict the counterfactual incidence of varicella and quantify the impact of varying NPIs intensities on varicella. From 2011 to 2021, varicella incidence increased, especially in 2019, with a high incidence of 111.69/100 000. However, there was a sharp decrease of 43.18% in 2020 compared with 2019, and the peak of varicella incidence in 2020 was lower than in previous years from the 21st to the 25th week. In 2021, the seasonality of varicella incidence gradually returned to a seasonal pattern in 2011-2019. The results suggest that anti-COVID-19 NPIs effectively reduce the incidence of varicella, and the reduction has spatiotemporal heterogeneity.

Azvudine therapy of common COVID-19 in hemodialysis patients.

There is no antiviral study on hemodialysis patients infected with coronavirus disease 2019 (COVID-19), especially on the application of 2'-deoxy-2'-ß -fluoro-4'-azidocytidine (Azvudine, FNC) antiviral therapy. We conducted a multicenter observational study involving 1008 hemodialysis patients. After matching for age, sex, and other factors, 182 patients in the basic treatment group and 182 in the FNC group were included. The negative nucleic acid conversion rate of the FNC group was significantly higher than that of the basic treatment group, and viral loads, interleukin-6, and C-reactive protein were significantly lower than those of the basic treatment group (p < 0.05). There were no significant differences in liver function, renal function, or the number of adverse events between the two groups (p > 0.05). In conclusion, our study has provided novel evidence suggesting that the FNC scheme may be safe and effective compared to the basic treatment of hemodialysis patients with common COVID-19.

The binding profile of SARS-CoV-2 with human leukocyte antigen polymorphisms reveals critical alleles involved in immune evasion.

The COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), astonished the world and led to millions of deaths. Due to viral new mutations and immune evasion, SARS-CoV-2 ranked first in transmission and influence. The binding affinity of human leukocyte antigen (HLA) polymorphisms to SARS-CoV-2 might be related to immune escape, but the mechanisms remained unclear. In this study, we obtained the binding affinity of SARS-CoV-2 strains with different HLA proteins and identified 31 risk alleles. Subsequent structural predictions identified 10 active binding sites in these HLA proteins that may promote immune evasion. Particularly, we also found that the weak binding ability with HLA class I polymorphisms could contribute to the immune evasion of Omicron. These findings suggest important implications for preventing the immune evasion of SARS-CoV-2 and providing new insights for the vaccine design.

Decreased frequency of a novel T-lymphocyte subset, CD3+ CD4- CD7+ CD57- T cells, in hepatitis B virus-related end-stage liver disease might contribute to disease progression.

CD7 and CD57 are related to the differentiation and functional stages of CD8+ T cells. However, the role of their combined presence in CD8+ T cells in patients with chronic hepatitis B virus (HBV) infection, especially those with end-stage liver disease, remains unclear. Blood samples from healthy volunteers and patients with chronic hepatitis B were analyzed via Luminex assay and ELISA to measure plasma cytokine levels. Further, recombinant IL-22 was used to stimulate peripheral blood mononuclear cells from healthy volunteers, and the frequency of CD3+ CD4- CD7+ CD57- T cells and apoptosis rates were investigated via flow cytometry. Patients with end-stage liver disease, particularly those with acute to chronic liver failure, showed decreased CD3+ CD4- CD7+ CD57- T cell frequency. Furthermore, the prevalence of CD3+ CD4- CD7+ CD57- T cells was negatively correlated with disease severity, prognosis, and complications (ascites). We also observed that IL-22 promoted apoptosis and brought about a decrease in the number of CD3+ CD4- CD7+ CD57- T cells in a dose-dependent manner. CD3+ CD4- CD7+ CD57- T cells displayed a B and T lymphocyte attenuator (BTLA)high CD25high CD127high immunosuppressive phenotype and showed low interferon-γ, tumor necrosis factor-α, granzyme A, and perforin expression levels. The present findings will elucidate the pathogenesis of HBV-related end-stage liver disease and aid the identification of novel drug targets.

The emerging roles of the CDK/cyclin complexes in antiviral innate immunity.

More than 20 members of the human cyclin-dependent kinases (CDKs) family share the feature of being activated by cyclins. CDKs have been involved in diverse biological processes, such as cell cycle, transcription, DNA damage response, and apoptosis. If CDKs are not properly regulated, they can cause diseases like cancer. CDKs are Ser/Thr kinases that work with cyclins to control cell cycle progression. Various CDK-cyclin complexes phosphorylate particular target proteins and drive different cell cycle stages. Accumulating evidence demonstrated that CDKs play an essential role in the cell cycle; however, their roles in antiviral innate immunity are just emerging. This minireview summarizes how CDKs play their roles in antiviral innate immunity. Our goal is to draw attention to the involvement of CDKs in antiviral innate immunity, whether as separate entities or as components of CDK/cyclin complexes that have gotten less attention in the past.

When RING finger family proteins meet SARS-CoV-2.

The pandemic coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is currently the most formidable challenge to humankind. Understanding the complicated virus-host interplay is crucial for fighting against viral infection. A growing number of studies point to the critical roles of RING (really interesting new gene) finger (RNF) proteins during SARS-CoV-2 infection. RNF proteins exert direct antiviral activity by targeting genome and envelope glycoproteins of SARS-CoV-2. Additionally, some RNF members serve as potent regulators for antiviral innate immunity and antibody-dependent neutralization of SARS-CoV-2. Notably, SARS-CoV-2 also hijacks the RNF proteins-mediated ubiquitination process to evade host antiviral innate immunity and enhance viral replication. In this mini-review, we discuss the diverse antiviral mechanisms of RNF proteins and viral immune evasion in an RNF proteins-dependent manner. Understanding the crosstalk between RNF proteins and SARS-CoV-2 infection would help design potential novel targets for COVID-19 treatment.

When cyclin-dependent kinases meet viral infections, including SARS-CoV-2.

Cyclin-dependent kinases (CDKs) are protein kinases that play a key role in cell division and transcriptional regulation. Recent studies have demonstrated the critical roles of CDKs in various viral infections. However, the molecular processes underpinning CDKs' roles in viral infection and host antiviral defense are unknown. This minireview briefly overviews CDKs' functions and highlights the most recent discoveries of CDKs' emerging roles during viral infections, thereby providing a scientific and theoretical foundation for antiviral regulation and shedding light on developing novel drug targets and therapeutic strategies against viral infection.

UNC93B1 attenuates the cGAS-STING signaling pathway by targeting STING for autophagy-lysosome degradation.

Stimulator of interferon genes (STING) is a pivotal innate immune adaptor, and its functions during DNA virus infections have been extensively documented. However, its homeostatic regulation is not well understood. Our study demonstrates that Unc-93 homolog B1 (UNC93B1) is a crucial checker for STING to prevent hyperactivation. Ectopic expression of UNC93B1 attenuates IFN-ß promoter activity and the transcriptions of IFN-ß, ISG54, and ISG56 genes. Moreover, UNC93B1 also blocks the IRF3 nuclear translocation induced by ectopic expression of both cyclic GMP-AMP synthase (cGAS) and STING and reduces the stability of STING by facilitating its autophagy-lysosome degradation, which can be reversed by lysosome inhibitors. Mechanistically, UNC93B1 interacts with STING and suppresses STING-activated downstream signaling by delivering STING to the lysosomes for degradation, depending on its trafficking capability. UNC93B1 knockout in human embryonic kidney 293T cells facilitates IFN-ß promoter activity, IFN-ß, ISG54, and ISG56 transcriptions, and IRF3 nuclear translocation induced by ectopic expression of cGAS and STING. Infected with herpes simplex virus-1 (HSV-1), UNC93B1 knockdown BJ cells or primary peritoneal macrophages from Unc93b1-deficient (Unc93b1-/- ) mice show enhanced IFN-ß, ISG54, and ISG56 transcriptions, TBK1 phosphorylation, and reduced STING degradation and viral replication. In addition, Unc93b1-/-  mice exhibit higher IFN-ß, ISG54, and ISG56 transcriptions and lower mortality upon HSV-1 infection in vivo. Collectively, these findings demonstrate that UNC93B1 attenuates the cGAS-STING signaling pathway by targeting STING for autophagy-lysosome degradation and provide novel insights into the function of UNC93B1 in antiviral innate immunity.

The Deltacron conundrum: Its origin and potential health risks.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), since its outbreak in December 2019, has been capable of continuing the pandemic by mutating itself into different variants. Mass vaccinations, antibiotic treatment therapy, herd immunity, and preventive measures have reduced the disease's severity from the emerging variants. However, the virus is undergoing recombination among the current two variants: Delta and Omicron, resulting in a new variant, informally known as "Deltacron," which was controversial as it might be a product of lab contamination between Omicron and Delta samples. However, the proclamation was proved wrong, and the experts are putting more effort into better understanding the variant's epidemiological characteristics to control potential outbreaks. This review has discussed the potential mutations in the novel variant and prospective risk factors and therapeutic options in the context of this new variant. This study could be used as a guide for implementing appropriate controls in a sudden outbreak of this new variant.

Roles of the polybasic furin cleavage site of spike protein in SARS-CoV-2 replication, pathogenesis, and host immune responses and vaccination.

The polybasic furin cleavage site insertion with four amino acid motifs (PRRA) in spike protein's S1/S2 junction site is important in determining viral infectivity, transmission, and host range. However, there is no review so far explaining the effect of the furin cleavage site of the spike protein on SARS-CoV-2 replication and pathogenesis in the host and immune responses and vaccination. Therefore, here we specifically focused on genomic evolution and properties of the cleavage site of spike protein in the context of SARS-CoV-2 followed by its effect on viral entry, replication, and pathogenesis. We also explored whether the spike protein furin cleavage site affected the host immune responses and SARS-CoV-2 vaccination. This review will help to provide novel insights into the effects of polybasic furin cleavage site on the current COVID-19 pandemic.