Virus-infected Cells Research Articles

Recent Advances in Our Understanding of Human Inflammatory Dendritic Cells in Human Immunodeficiency Virus Infection

Anogenital inflammation is a critical risk factor for HIV acquisition. The primary preventative HIV intervention, pre-exposure prophylaxis (PrEP), is ineffective in blocking transmission in anogenital inflammation. Pre-existing sexually transmitted diseases (STIs) and anogenital microbiota dysbiosis are the leading causes of inflammation, where inflammation is extensive and often asymptomatic and undiagnosed. Dendritic cells (DCs), as potent antigen-presenting cells, are among the first to capture HIV upon its entry into the mucosa, and they subsequently transport the virus to CD4 T cells, the primary HIV target cells. This increased HIV susceptibility in inflamed tissue likely stems from a disrupted epithelial barrier integrity, phenotypic changes in resident DCs and an influx of inflammatory HIV target cells, including DCs and CD4 T cells. Gaining insight into how HIV interacts with specific inflammatory DC subsets could inform the development of new therapeutic strategies to block HIV transmission. However, little is known about the early stages of HIV capture and transmission in inflammatory environments. Here, we review the currently characterised inflammatory-tissue DCs and their interactions with HIV.

Iron improves the antiviral activity of NK cells

Natural killer (NK) cells are innate immune cells that play a crucial role as a first line of defense against viral infections and tumor development. Iron is an essential nutrient for immune cells, but it can also pose biochemical risks such as the production of reactive oxygen species. The importance of iron for the NK cell function has gained increasing recognition. We have previously shown that NK cells require iron to efficiently eliminate virus-infected target cells; however, the impact of nutritional iron deficiency on NK cell function and the therapeutic benefits of iron supplementation remain unclear. Here, we demonstrate that diet-related low iron levels lead to increased retroviral loads due to functional NK cell impairment, while iron supplementation enhances NK cell proliferation, as well as their cytotoxic efficacy. Notably, iron-treated NK cells exhibited significant metabolic changes, including mitochondrial reorganization. Interestingly, although iron supplementation decreased the NK cell’s cytokine production, it significantly improved NK cell degranulation and the expression of cytotoxicity-associated proteins. These findings highlight the critical role of iron in maintaining NK cell immunity and suggest that iron supplementation may hold therapeutic potential for supporting the treatment of viral infections and immunodeficiency disorders.

Sensing of SARS-CoV-2-infected cells by plasmacytoid dendritic cells is modulated via an interplay between CD54/ICAM-1 and CD11a/LFA-1 αL integrin.

Type I interferons (IFN-I) represent an important component of the host's innate defense against initial SARS-CoV-2 infections. Plasmacytoid dendritic cells (pDCs) produce large quantities of IFN-I upon recognition of viral particles or infected cells. This study shows that pDCs sense infected cells more efficiently than viral particles, leading to a higher production of IFN-I. Physical contact between a pDC and an infected cell is critical to this process; the interaction is mediated via CD11a and ICAM-1 complex and potentially is bidirectional. SARS-CoV-2 variants of concern (VOCs) have evolved to limit the IFN response through different mechanisms. For the Alpha variant, reduced level of CD11a on infected cells is linked to less contact with pDCs and decreased IFN-I release. Overall, our study characterizes some of the early steps involved in pDC-mediated response against SARS-CoV-2 infection and shows that these processes are targeted by VOCs to likely limit IFN-I response and enhance viral spread.

Effect of eicosapentaenoic acid on innate immune responses in Atlantic salmon cells infected with infectious salmon anemia virus

Aquaculture is one of the world's fastest-growing sectors in food production but with multiple challenges related to animal handling and infections. The disease caused by infectious salmon anemia virus (ISAV) leads to outbreaks of local epidemics, reducing animal welfare, and causing significant economic losses. The composition of feed has shifted from marine ingredients such as fish oil and fish meal towards a more plant-based diet causing reduced levels of eicosapentaenoic acid (EPA). The aim of this study was to investigate whether low or high levels of EPA affect the expression of genes related to the innate immune response 48 h after infection with ISAV. The study includes seven experimental groups: ± ISAV and various levels of EPA up to 200 µM. Analysis of RNA sequencing data showed that more than 3000 genes were affected by ISAV alone (without additional EPA). In cells with increasing levels of EPA, more than 2500 additional genes were differentially expressed. This indicates that high levels of EPA concentration have an independent effect on gene expression in virus-infected cells, not observed at lower levels of EPA. Analyses of enriched biological processes and molecular functions (GO and KEGG analysis) revealed that EPA had a limited impact on the innate immune system alone, but that many processes were affected by EPA when cells were virus infected. Several biological pathways were affected, including protein synthesis (ribosomal transcripts), peroxisome proliferator activated receptor (PPAR) signaling, and ferroptosis. Cells exposed to both increasing concentrations of EPA and virus displayed gene expression patterns indicating increased formation of oxygen radicals and that cell death via ferroptosis was activated. This gene expression pattern was not observed during infection at low EPA levels or when Atlantic salmon kidney (ASK) cells were exposed to the highest EPA level (200 μM) without virus infection. Cell death via ferroptosis may therefore be a mechanism for controlled cell death and thus reduction of virus replication when there are enough polyunsaturated fatty acids (PUFAs) in the membrane.

Acidic pH can attenuate immune killing through inactivation of perforin.

Cytotoxic lymphocytes are crucial to our immune system, primarily eliminating virus-infected or cancerous cells via perforin/granzyme killing. Perforin forms transmembrane pores in the plasma membrane, allowing granzymes to enter the target cell cytosol and trigger apoptosis. The prowess of cytotoxic lymphocytes to efficiently eradicate target cells has been widely harnessed in immunotherapies against haematological cancers. Despite efforts to achieve a similar outcome against solid tumours, the immunosuppressive and acidic tumour microenvironment poses a persistent obstacle. Using different types of effector cells, including therapeutically relevant anti-CD19 CAR T cells, we demonstrate that the acidic pH typically found in solid tumours hinders the efficacy of immune therapies by impeding perforin pore formation within the immunological synapse. A nanometre-scale study of purified recombinant perforin undergoing oligomerization reveals that pore formation is inhibited specifically by preventing the formation of a transmembrane β-barrel. The absence of perforin pore formation directly prevents target cell death. This finding uncovers a novel layer of immune effector inhibition that must be considered in the development of effective immunotherapies for solid tumours.

Phenazine biosynthesis-like domain-containing protein (PBLD) and Cedrelone promote antiviral immune response by activating NF-ĸB

Phenazine biosynthesis-like domain-containing protein (PBLD) and Cedrelone have been identified as tumor suppressors. However, their roles in virus infection remain unclear. Here, we demonstrate that PBLD upregulates the type I interferon (IFN-I) response through activating NF-kappaB (NF-κB) signaling pathway to resist viral infection in cells and mice. Mechanistically, PBLD activates NF-κB signaling pathway during viral infection via blocking tripartite motif containing 21 (TRIM21)-mediated phosphorylated inhibitory kappa B kinase beta (IKKβ) degradation. Furthermore, we show Cedrelone inhibits viral replication by increasing the PBLD protein expression and subsequently activating NF-κB-mediated IFN-I response. Furthermore, the therapeutic potential of Cedrelone lies in its ability to enhance antiviral immunity in primary macrophages and to promote survival and reduce lung tissue damage in HSV-1-infected mice in a PBLD-dependent manner. Consequently, our findings provide a potential combination model that targets PBLD for Cedrelone antiviral drug therapy, potentially paving the way for the development of broad-spectrum antiviral agents.

Haemolymphatic tissues of captive boa constrictor (Boa constrictor): Morphological features in healthy individuals and with boid inclusion body disease.

Knowledge on the structure and composition of the haematopoietic tissue (HT) is essential to understand the basic immune functions of the immune system in any species. For reptiles, it is extremely limited, hence we undertook an in-depth in situ investigation of the HT (bone marrow, thymus, spleen, lymphatic tissue of the alimentary tract) in the common boa (Boa constrictor). We also assessed age- and disease-related changes, with a special focus on Boid Inclusion Body Disease, a highly relevant reptarenavirus-associated disease in boid snakes. The HT was subjected to gross, histological and ultrastructural examination, including special stains to highlight collagen and reticulin fibers and iron, immunohistochemistry, in situ hybridization and morphometric analyses. In general, the HT was dominated by T cells and lacked a clear structural organization, such as follicle formation. BIBD was associated with significantly higher cellularity and a granulomatous response in the spleen, and the presence of virus-infected haematopoietic cells in the bone marrow, suggesting the latter as a persistent source of viremia.

In Vitro Evaluation of Bunyavirus T Cell Immunity.

Characterization and quantitation of T cell responses following infection and/or vaccination can provide insight into mechanisms of host cell immunity that provide resolution of acute infection or protection from future infection or disease. While these types of studies are very advanced for viruses such as HIV, influenza, and SARS-CoV-2, they are less well developed for most of the Bunyaviruses. Cytotoxic CD8T cells are especially relevant in the context of viral infections since they recognize virus-infected cells via interaction of the T cell receptor with virally derived peptides presented in the context of MHCI. CD4T follicular cells are especially important for augmenting the antiviral antibody response. This chapter provides methods for characterizing T cell responses post infection/vaccination in both mice and humans as well as several methods for quantifying virus-specific T cells with the goal of arming bunyavirus researchers with the tools needed to move the field forward.

The Role of Bone Marrow Stromal Cell Antigen 2 (BST2) in the Migration of Dendritic Cells to Lymph Nodes

Bone marrow stromal antigen 2 (BST2) is a host-restriction factor that plays multiple roles in the antiviral defense of innate immune responses, including the inhibition of viral particle release from virus-infected cells. BST2 may also be involved in the endothelial adhesion and migration of monocytes, but its importance in the immune system is still unclear. Immune cell adhesion and migration are closely related to the initiation of immune responses. In this study, we found that the expressions of the lymph node homing marker chemokine receptor 7 (CCR7) and an adhesion molecule intercellular adhesion molecule 1 (ICAM-1) in conventional dendritic cells (cDCs) were associated with BST2 expression. Interestingly, Bst2−/− cDCs showed lower chemotactic ability, including velocity and accumulative distance toward chemokine ligand 19 (CCL19) gradient in vitro, compared to wild-type cDCs. Bst2−/− cDCs also showed reduced migration and reduced retention capacity in draining lymph nodes in vivo. As a result, Bst2−/− cDCs as antigen-presenting cells induced lower antigen-specific B cell and T cell responses compared to Bst2+/+ cDCs. Notably, mice administered the influenza vaccine via Bst2−/− cDCs exhibited substantially inefficient virus clearance compared to mice administered the Bst2+/+ cDCs vaccine. Therefore, we propose that BST2, which plays a critical role in the effective migration and retention of cDCs, is involved in the development of optimal immunological effects in draining lymph nodes.

Genome editing of PSIP1 gene encoding LEDGF/p75 protects TZM_bl GFP cells from HIV-1 infection

Gene therapy is a good way to cure HIV permanently. Human immunodeficiency virus (HIV-1) infected cells depend on host-cell factors. LEDGF/p75 is a co-factor encoded by the PSIP1 gene and it interacts with HIV integrase to help the virus bind to host cells genome. If the PSIP1 gene is knocked out in the TZM-bI GFP cell line using CRISPR/Cas technology, the amount of HIV DNA integrated into the cell will be reduced due to the inability of HIV integrase to efficiently bind and integrate into the transcriptionally active regions of the host cell chromatin. The change in infectivity was observed by fluorescence microscopy and flow cytometry. The results show that KO PSIP1 may inhibit HIV infectivity. More experiments are needed to prove the reliability of this result.

MARCH8 Restricts RSV Replication by Promoting Cellular Apoptosis Through Ubiquitin-Mediated Proteolysis of Viral SH Protein.

Numerous host factors function as intrinsic antiviral effectors to attenuate viral replication. MARCH8 is an E3 ubiquitin ligase that has been identified as a host restriction factor that inhibits the replication of various viruses. This study elucidated the mechanism by which MARCH8 restricts respiratory syncytial virus (RSV) replication through selective degradation of the viral small hydrophobic (SH) protein. We demonstrated that MARCH8 directly interacts with RSV-SH and catalyzes its ubiquitination at lysine 13, leading to SH degradation via the ubiquitin-lysosomal pathway. Functionally, MARCH8 expression enhances RSV-induced apoptosis through SH degradation, ultimately reducing viral titers. Conversely, an RSV strain harboring the SH-K13R mutation exhibited prolonged SH protein stability and attenuated apoptosis in infected cells, even in the presence of MARCH8. Targeted depletion of MARCH8 enhances cellular survival and potentially increases viral persistence. These findings demonstrate that MARCH8 promotes the early elimination of virus-infected cells by abrogating the anti-apoptotic function of SH, thereby reducing viral transmission. Our study provides novel insights into the interplay between host restriction factors and viral evasion strategies, potentially providing new therapeutic approaches for RSV infections.

Fructose-1,6-diphosphate inhibits viral replication by promoting the lysosomal degradation of HMGB1 and blocking the binding of HMGB1 to the viral genome.

Fructose-1,6-diphosphate (FBP), a key glycolytic metabolite, is recognized for its cytoprotective effects during stress. However, the role of FBP in viral infections is unknown. Here, we demonstrate that virus-infected cells exhibit elevated FBP levels. Exogenous FBP inhibits both RNA and DNA virus infections in vitro and in vivo. Modulating intracellular FBP levels by regulating the expression of the metabolic enzymes FBP1 and PFK1 significantly impacts viral infections. Mechanistically, the inhibitory effects of FBP are not a result of altered viral adhesion or entry and are largely independent of type I interferon-mediated immune responses; rather, they occur through modulation of HMGB1. During viral infections, FBP predominantly reduces the protein levels of HMGB1 by facilitating its lysosomal degradation. Furthermore, FBP interacts with HMGB1 and disrupts the binding of HMGB1 to viral genomes, thereby further inhibiting viral replication. Our findings underscore the potential of FBP as a therapeutic target for controlling viral infections.

Nutrient-driven histone code determines exhausted CD8+ T cell fates.

Exhausted T cells (TEX) in cancer and chronic viral infections undergo metabolic and epigenetic remodeling, impairing their protective capabilities. However, the impact of nutrient metabolism on epigenetic modifications that control TEX differentiation remains unclear. We showed that TEX cells shifted from acetate to citrate metabolism by downregulating acetyl-CoA synthetase 2 (ACSS2) while maintaining ATP-citrate lyase (ACLY) activity. This metabolic switch increased citrate-dependent histone acetylation, mediated by histone acetyltransferase KAT2A-ACLY interactions, at TEX signature-genes while reducing acetate-dependent histone acetylation, dependent on p300-ACSS2 complexes, at effector and memory T cell genes. Nuclear ACSS2 overexpression or ACLY inhibition prevented TEX differentiation and enhanced tumor-specific T cell responses. These findings unveiled a nutrient-instructed histone code governing CD8+ T cell differentiation, with implications for metabolic- and epigenetic-based T cell therapies.

High mortality associated with avian reoviral hepatitis in young quail (Colinus virginianus).

High mortality in bobwhite quail chicks (Colinus virginianus) (35%-85%) was reported from a grower flock in Iowa during July and August of 2022. Two diagnostic submissions of dead, 3-day-old quail chicks were received. Postmortem examination revealed multifocal, pinpoint, pale tan foci in the liver of all birds. Histologic examination revealed moderate to severe, acute, multifocal, random necrotizing hepatitis with multinucleated cells and dystrophic mineralization. Metagenomic sequencing of liver detected orthoreovirus. A high level of avian reovirus (ARV) RNA was identified by real-time reverse transcriptase-PCR. ARV was successfully isolated from liver and lung on the Leghorn male hepatoma cell line. In addition, electron microscopy revealed orthoreovirus viral particles and virus factories in the formalin-fixed livers and viral-infected cell culture. This case highlights ARV as a potential cause of hepatitis in quail chicks and should be considered in the differential diagnosis.

Golden Therapeutic Approach to Combat Viral Diseases Using Gold Nanomaterials.

Gold nanoparticles (AuNPs), due to their unique properties and surface modification abilities, have become a promising carrier for a range of biomedical applications. AuNPs have intrinsic antiviral characteristics because of their capacity to enhance drug distribution by making antiviral medications more stable and soluble, which assures that higher quantities reach the intended site. Through surface changes, AuNPs can bind directly to viral particles or infected cells, increasing therapeutic efficiency and reducing side effects. AuNPs efficiently damage cell membranes and hinder viral reproduction within a host cell. Furthermore, because of their large surface area-to-volume ratio, which enables many functional groups to connect, improving interaction with virus particles and ceasing their multiplication. By altering dimensions and morphology or conjugating it with additional antiviral drugs, AuNPs can array their synergistic antiviral activity. Thus, the development of AuNP conjugated therapy presents a promising avenue to address the demand for novel anti-viral therapeutics against infections resistant to several drugs.

Ring finger protein 5 mediates STING degradation through ubiquitinating K135 and K155 in a teleost fish.

Stimulator of interferon genes (STING) is a key connector protein in interferon (IFN) signaling, crucial for IFN induction during the activation of antiviral innate immunity. In mammals, ring finger protein 5 (RNF5) functions as an E3 ubiquitin ligase, mediating STING regulation through K150 ubiquitylation to prevent excessive IFN production. However, the mechanisms underlying RNF5's regulation of STING in teleost fish remain unknown. This study investigated the regulatory role of the mandarin fish (Siniperca chuatsi) RNF5 (scRNF5) in the STING-mediated antiviral immune response and identified the specific regulatory sites on scSTING. Furthermore, an examination of scRNF5 expression patterns in virus-infected cells revealed its responsiveness to mandarin fish ranavirus (MRV) infection. The ectopic expression of scRNF5 suppressed scSTING-mediated IFN signaling and facilitated MRV replication. Co-immunoprecipitation experiments indicated an interaction between scRNF5 and scSTING. The further experiments demonstrated that scRNF5 exerted its inhibitory effect by promoting the degradation of scSTING, which was observed to be blocked by MG132 treatment. Ubiquitination assays with various scSTING mutants showed that scRNF5 catalyzed the ubiquitination of scSTING at K135 and K155 residues. Furthermore, we provided evidence that scRNF5 significantly attenuated scSTING-dependent antiviral immunity by targeting negative regulators within the scSTING signaling cascade. This study underscored that RNF5 negatively regulated the STING-mediated IFN signaling pathway in mandarin fish, attenuated STING's antiviral activity, and facilitated STING degradation via the ubiquitin-proteasome pathway at two novel lysine sites (K135 and K155). Our work offered valuable insights into the regulatory mechanisms of STING-mediated signaling in teleost fish, paving the way for further research.

Relationship between the risk of intestinal mucosal Epstein-Barr virus and/or cytomegalovirus infection and peripheral blood NK cells numbers in patients with ulcerative colitis: a cross-sectional study in Chinese population.

This study aimed to analyze the relationship between the risk of common opportunistic pathogens Epstein-Barr virus (EBV) and cytomegalovirus (CMV) infection in intestinal mucosal tissues of Ulcerative Colitis (UC) patients and the number of peripheral blood NK cells. UC patients admitted to a third-grade class-A hospital from January 2018 to December 2023 were selected as research population. Clinical data of the patients were collected from the electronic medical record system. Additionally, samples of intestinal mucosal tissues were obtained for real-time fluorescence quantitative PCR to detect and analyze the viral load of CMV and EBV. Blood samples were collected for lymphocyte subsets analysis. Multivariable logistic regression models analyses was used to determine the odds ratio (OR) and 95% confidence interval (95% CI) for the independent association between NK cells and EBV/CMV infections in UC. We further applied the restricted cubic spline analysis and smooth curve fitting to examine the non-linear relationship between them. 378 UC patients were enrolled. Of these patients, there were 194 patients (51.32%) with EBV /CMV infection. In multivariable logistic regression analyses NK cells was independently associated with EBV and/or CMV infection after adjusted potential confounders (OR 8.24, 95% CI 3.75-18.13, p < 0.001). A nonlinear relationship was found between NK cells and EBV/CMV infections, which had a threshold around 10.169. The effect sizes and CIs below and above the threshold were 0.535 (0.413-0.692), p < 0.001 and 1.034 (0.904-1.183), p > 0.05, respectively. There was a non-linear relationship between NK cells and EBV/CMV infections. The risk for EBV/CMV infections was not increased with increasing NK cells in individuals with NK cells ≥ 10.169%, whereas the risk for EBV and/or CMV infection was increased with an decreasing NK cells in those with NK cells < 10.169%. The risk of EBV/CMV infections increases when NK cells were below a certain level.

Glutamine metabolism Is essential for coronavirus replication in host cells and in mice.

Understanding the fundamental biochemical and metabolic requirements for the replication of coronaviruses within infected cells is of notable interest for the development of broad-based therapeutic strategies, given the likelihood of emergence of new pandemic-potential virus species, as well as future variants of SARS-CoV-2. Here we demonstrate members of the glutaminase family of enzymes (GLS and GLS2), which catalyze the hydrolysis of glutamine to glutamate (i.e., the first step in glutamine metabolism), play key roles in coronavirus replication in host cells. Using a range of human seasonal and zoonotic coronaviruses, we show three examples where GLS expression increases during coronavirus infection of host cells, and another where GLS2 is upregulated. The viruses hijack the metabolic machinery responsible for glutamine metabolism to generate the building blocks for biosynthetic processes and satisfy the bioenergetic requirements demanded by the 'glutamine addiction' of virus-infected cells. We demonstrate that genetic silencing of glutaminase enzymes reduces coronavirus infection and that newer members of two classes of allosteric inhibitors targeting these enzymes, designated as SU1, a pan-GLS/GLS2 inhibitor, and UP4, a specific GLS inhibitor, block viral replication in epithelial cells. Moreover, treatment of SARS-CoV-2 infected K18-human ACE2 transgenic mice with SU1 resulted in their complete survival compared to untreated control animals, which succumbed within 10 days post-infection. Overall, these findings highlight the importance of glutamine metabolism for coronavirus replication in human cells and mice and show that glutaminase inhibitors can block coronavirus infection and thereby may represent a novel class of broad-based anti-viral drug candidates.

Oncolytic vaccinia virus armed with anti-CD47 nanobody elicit potent antitumor effects on multiple tumor models via enhancing innate and adoptive immunity

ObjectiveTargeting CD47 for cancer immunotherapy has been studied in many clinical trials for the treatment of patients with advanced tumors. However, this therapeutic approach is often hampered by on-target side...

Advances in Induced Pluripotent Stem Cell-Derived Natural Killer Cell Therapy.

Natural killer (NK) cells are cytotoxic lymphocytes of the innate immune system capable of killing virus-infected cells and/or cancer cells. The commonly used NK cells for therapeutic applications include primary NK cells and immortalized NK cell lines. However, primary NK cell therapy faces limitations due to its restricted proliferation capacity and challenges in stable storage. Meanwhile, the immortalized NK-92 cell line requires irradiation prior to infusion, which reduces its cytotoxic activity, providing a ready-made alternative and overcoming these bottlenecks. Recent improvements in differentiation protocols for iPSC-derived NK cells have facilitated the clinical production of iPSC-NK cells. Moreover, iPSC-NK cells can be genetically modified to enhance tumor targeting and improve the expansion and persistence of iPSC-NK cells, thereby achieving more robust antitumor efficacy. This paper focuses on the differentiation-protocols efforts of iPSC-derived NK cells and the latest progress in iPSC-NK cell therapy. Additionally, we discuss the current challenges faced by iPSC-NK cells and provide an outlook on future applications and developments.