IL-26 inhibits hepatitis C virus replication in hepatocytes

STING exerts antiviral innate immune response by activating pentose phosphate pathway

BACKGROUND

The innate immune system serves as the host's first line of defense against invading pathogens. Stimulator of interferon genes (STING) is a key component of this system, yet its relationship with glucose metabolism, particularly in antiviral immunity, remains underexplored.

METHODS

Metabolomics analysis was used for detecting metabolic alterations in spleens from STING knockout (KO) and wild-type (WT) mice. Co-immunoprecipitation was employed for determining ubiquitination of TKT. Mass spectrometry was used for detecting interaction proteins of STING. Enzyme activity kits were used for detecting the activities of TKT and G6PD.

RESULTS

In this study, we demonstrate that herpes simplex virus (HSV) infection activates the pentose phosphate pathway (PPP) in host cells, thereby initiating an antiviral immune response. Using STING-manipulated cells and systemic knockout mice, we show that STING positively regulates PPP, which, in turn, limits HSV infection. Inhibition of the PPP significantly reduced the production of antiviral immune factors and dampened STING-induced innate immune responses. Mechanistically, we discovered that STING interacts with transketolase (TKT), a key enzyme in the non-oxidative branch of the PPP, and reduces its ubiquitination via the E3 ubiquitin ligase UBE3A, stabilizing TKT. Silencing TKT or inhibiting its activity with oxythiamine diminished antiviral immune factor production.

CONCLUSION

Our findings reveal that the PPP plays a synergistic role in generating antiviral immune factors during viral infection and suggest that PPP activation could serve as an adjunct strategy for antiviral therapy.

Systemic increase in IL-26 is associated with severe COVID-19 and comorbid obstructive lung disease

Background

IL-26 is a key mediator of pulmonary host defense given its abundant expression in human airways and its established antibacterial properties. Moreover, recent studies indicate that IL-26 can also inhibit viral replication. Along these lines, we have previously reported an increase in the plasma concentration of IL-26 among patients with acute COVID-19 that is linked to harmful hyperinflammation. Nevertheless, it is still unclear whether this systemic increase in IL-26 relates to disease severity, sex, comorbidities, viral load, or the innate immune response in acute COVID-19.

Methods

IL-26 was quantified using ELISA in plasma samples from a large cohort of well-characterized patients with acute COVID-19 (n=178) and healthy controls (n=30). The plasma concentrations of SARS-CoV-2 nucleocapsid and spike protein, as well as those of IFN-α2a, IFN-β, and IFN-γ, were determined using electrochemiluminescence immunoassay. The concentration of double-stranded DNA was determined using fluorometry.

Results

The plasma concentration of IL-26 was increased in patients with severe/critical COVID-19, particularly among males and patients with comorbid obstructive lung disease. Moreover, the concentration of IL-26 displayed positive correlations with length of hospital stay, as well as with systemic markers of viral load, antiviral immunity, and extracellular DNA.

Conclusions

Systemic IL-26 is involved in severe COVID-19, especially in males and patients with comorbid obstructive lung disease. These findings argue that systemic IL-26 has pathogenic and antiviral relevance, as well as biomarker potential.

Interleukin-26 in channel catfish (Ictalurus punctatus): Molecular characterization and immune functional activity

IL-26 is a crucial inflammatory cytokine that participates in defending host cells against infections. We initially cloned and identified the cDNA sequences of interleukin (IL)-26 in channel catfish (Ictalurus punctatus). The open reading frame (ORF) of IpIL-26 was 537 bp in length, encoding 178 amino acids (aa). Constitutive expression of IpIL-26 was observed in tested tissues, with the highest level found in the gill and spleen. To explore the function of IpIL-26 in channel catfish, different stimuli were used to act on both channel catfish and channel catfish kidney cells (CCK). The expression of IpIL-26 could be up-regulated by bacteria and viruses in multiple tissues. In vitro, recombinant IpIL-26 (rIpIL-26) could induce the expression levels of inflammatory cytokines such as TNF-α, IL-1β, IL-6, IL-20, and IL-22 playing vital roles in defending the host against infections. Our results demonstrated that IpIL-26 might be an essential cytokine, significantly affecting the immune defense of channel catfish against pathogen infections.

Anti-infective immune functions of type IV interferon in grass carp ( Ctenopharyngodon idella): A novel antibacterial and antiviral interferon in lower vertebrates

Type IV interferon (IFN-υ) is a recently discovered cytokine crucial for host defense against viral infections. However, the role and mechanisms of IFN-υ in bacterial infections remain unexplored. This study investigated the antibacterial and antiviral functions and mechanisms of grass carp ( Ctenopharyngodon idella) IFN-υ (CiIFN-υ) both in vivo and in vitro. The CiIFN-υ gene was first identified and characterized in grass carp. Subsequently, the immune expression of CiIFN-υ significantly increased following bacterial challenge, indicating its response to bacterial infections. The eukaryotic recombinant expression plasmid of CiIFN-υ was then constructed and transfected into fathead minnow (FHM) cells. Supernatants were collected and incubated with four bacterial strains, followed by plate spreading and colony counting. Results indicated that CiIFN-υ exhibited more potent antibacterial activity against gram-negative bacteria compared to gram-positive bacteria and aggregated gram-negative bacteria but not gram-positive bacteria. In vivo experiments further confirmed the antibacterial function, showing high survival rates, low tissue edema and damage, reduced tissue bacterial load, and elevated proinflammatory response at the early stages of bacterial infection. In addition, the antiviral function of CiIFN-υ was confirmed through in vitro and in vivo experiments, including crystal violet staining, survival rates, tissue viral burden, and RT-qPCR. This study highlights the antibacterial function and preliminary mechanism of IFN-υ, demonstrating that IFN-υ possesses dual functions against bacterial and viral infections.

A Comprehensive Network Map of Interleukin-26 Signaling Pathway

Interleukin-26 (IL-26) is a cytokine that belongs to the IL-20 subfamily and is primarily expressed in T helper 1 cells and Th17 memory CD4+ cells. Its receptor complex, consisting of IL-20R1 and IL-10R2, activates a signaling pathway involving several proteins such as Janus kinase 1 and tyrosine-protein kinase, signal transducer and activator of transcription (STAT) 1, and STAT3. This leads to the initiation of downstream signaling cascades that play a crucial role in various biological processes, including inflammation, immune response regulation, atopic dermatitis, macrophage differentiation, osteoclastogenesis, antibacterial host defense, anti-apoptosis, and tumor growth. In this study, we curated literature data pertaining to IL-26 signaling. The curated map includes a total of seven activation/inhibition events, 16 catalysis events, 33 gene regulation events, 25 protein expression types, two transport events, and three molecular associations.

Immunobiology of IL-26

T helper 17 (Th17) cells produce a set of cytokines that include IL-17 family members, IL-21, IL-22, and IL-26. These cytokines all contribute to the classic function of Th17 cells in combatting extracellular infection and promoting inflammation in autoimmune diseases. However, of the Th17 cytokines, only IL-26 has direct antimicrobial activity against microbes and can activate a broad range of immune cells through its ability to bind DNA and trigger pattern recognition receptors. It is noteworthy that IL-26 is produced by mammalian cells, including human Th17 cells, but is absent in rodents. As such, IL-26 is a potential therapeutic target to augment host immune responses against microbial pathogens but also to prevent inflammation and tissue damage in a variety of autoimmune diseases.

The role of interleukin-20 in liver disease: Functions, mechanisms and clinical applications

Liver disease is a severe public health concern worldwide. There is a close relationship between the liver and cytokines, and liver inflammation from a variety of causes leads to the release and activation of cytokines. The functions of cytokines are complex and variable, and are closely related to their cellular origin, target molecules and mode of action. Interleukin (IL)-20 has been studied as a pro-inflammatory cytokine that is expressed and regulated in some diseases. Furthermore, accumulating evidences has shown that IL-20 is highly expressed in clinical samples from patients with liver disease, promoting the production of pro-inflammatory molecules involved in liver disease progression, and antagonists of IL-20 can effectively inhibit liver injury and produce protective effects. This review highlights the potential of targeting IL-20 in liver diseases, elucidates the potential mechanisms of IL-20 inducing liver injury, and suggests multiple viable strategies to mitigate the pro-inflammatory response to IL-20. Genomic CRISPR/Cas9-based screens may be a feasible way to further explore the signaling pathways and regulation of IL-20 in liver diseases. Nanovector systems targeting IL-20 offer new possibilities for the treatment and prevention of liver diseases.

Pseudotyped Virus for Flaviviridae

Members of Flaviviridae are enveloped single positive-stranded RNA viruses including hepacivirus, pestivirus, pegivirus, and mosquito-transmitted flavivirus, which are important pathogens of infectious diseases and pose serious threats to human health. Pseudotyped virus is an artificially constructed virus-like particle, which could infect host cells similar to a live virus but cannot produce infectious progeny virus. Therefore, pseudotyped virus has the advantages of a wide host range, high transfection efficiency, low biosafety risk, and accurate and objective quantification. It has been widely used in biological characteristics, drug screening, detection methods, and vaccine evaluation of Flaviviridae viruses like hepatitis C virus, Japanese encephalitis virus, dengue virus, and Zika virus.

Increased IL-26 associates with markers of hyperinflammation and tissue damage in patients with acute COVID-19

Interleukin-26 (IL-26) is released by several immune and structural cells following stimulation of toll-like receptors (TLRs), whereupon it can directly inhibit viral replication and enhance neutrophil chemotaxis. Given these unique properties, IL-26 has emerged as an intriguing mediator of host defense in the lungs. However, the role of IL-26 in COVID-19 has not been thoroughly investigated. Here, we characterized the involvement of IL-26 in the hyperinflammation and tissue damage that occurs in patients with acute COVID-19. We found that IL-26 is markedly increased in blood samples from these patients, and that the concentration of IL-26 correlates with those of the neutrophil-mobilizing cytokines IL-8 and TNFα, respectively. Moreover, the increase in blood IL-26 correlates with enhanced surface expression of the “don’t eat me” signal CD47 on blood neutrophils isolated from patients with acute COVID-19. Finally, we found that the blood concentration of IL-26 correlates with that of increased lactate dehydrogenase, an established marker of tissue damage, and decreased mean corpuscular hemoglobin (MCH), a previously verified hematological aberration in COVID-19, both of which are associated with severe disease. Thus, our findings indicate that increased systemic IL-26 associates with markers of hyperinflammation and tissue damage in patients with acute COVID-19, thereby forwarding the kinocidin IL-26 as a potential target for diagnosis, monitoring, and therapy in this deadly disease.

Serum Interleukin-26 is a Potential Biomarker for the Differential Diagnosis of Neurosyphilis and Syphilis at Other Stages

Background

Interleukin-26 (IL-26) is an atypical proinflammatory cytokine due to its binding to circulating double-stranded DNA and direct antibacterial activity. Although IL-26 has been confirmed to be involved in the pathophysiology of cancer, chronic inflammatory diseases and infections, the diagnostic and prognostic values of IL-26 levels in syphilis patients are not clear. This study aimed to investigate IL-26 levels in different stages of syphilis progression.

Methods

A total of 30 healthy controls and 166 patients with syphilis at different stages of disease progression were enrolled. Serum IL-26 levels were quantified in accordance with the protocols of RayBio^® Human Interleukin-26 Enzyme Linked Immunosorbent Assay (ELISA) kits. Clinical laboratory diagnostic parameters and blood analysis data were detected and collected according to clinical medical laboratory standards.

Results

The levels of serum IL-26 were significantly higher in neurosyphilis patients than in healthy subjects (6.87 (4.36, 12.14) and 1.67 (0.09, 4.89) pg/μL, respectively; ****p < 0.0001), latent syphilis (1.48 (0.40, 2.05) pg/μL, ****p < 0.0001), seroresistant syphilis (0.81 (0.20, 2.91) pg/μL, ****p < 0.0001) and secondary syphilis (1.66 (0.41, 4.25) pg/μL, ****p < 0.0001) with data presented as the median with interquartile range. The concentration of serum IL-26 was most sensitive to serum low-density lipoprotein concentration (r = -0.438, **p = 0.004) in latent syphilis, urine epithelial cells (r = 0.459, **p = 0.003) in seroresistant syphilis, and serum creatinine levels (r = 0.463, **p = 0.004) and urea creatinine ratio levels (r = 0.500, **p = 0.008) in secondary syphilis patients. There was no significant correlation with the concentration of IL-26 and toluidine red unheated serum test (TRUST) titers in each type of syphilis patient.

Conclusion

Circulating IL-26 in serum displays diagnostic potential in the progression of neurosyphilis and warrants further evaluation in clinical trials.