Activation of the cGAS-STING pathway by viral dsDNA leading to M1 polarization of macrophages mediates antiviral activity against hepatitis B virus.

BACKGROUND AND AIMS: Activation of the cGAS-STING pathway induces the production of type I interferons, initiating the antiviral immune response, which contributes to the clearance of pathogens. Previous studies have shown that STING agonists promote hepatitis B virus (HBV) clearance; however, few studies have investigated the effect of activating the cGAS-STING pathway in macrophages on HBV. METHODS: The polarization status of HBV particle-stimulated RAW264.7 macrophages was analyzed. After stimulation with HBV particles, the analysis focused on determining whether the DNA sensors in RAW264.7 macrophages recognized the viral double-stranded DNA (dsDNA) and evaluating the activation of the cGAS-STING pathway. Coculture of mouse macrophages and hepatocytes harboring HBV was used to study the antiviral activity of HBV-stimulated RAW264.7 macrophages. RESULTS: After stimulation with HBV particles, HBV relaxed circular DNA (rcDNA) was detected in RAW264.7 macrophages, and the protein expression of phospho-STING, phospho-TBK1, and phospho-IRF3 in the STING pathway was increased, as shown by Western blot analysis, which revealed that M1 polarization of macrophages was caused by increased expression of CD86. RT-PCR analyses revealed elevated expression of M1 macrophage polarization-associated cytokines such as TNFα, IL-1ß, iNOS, and IFNα/ß. In the coculture experiment, both HBsAg and HBeAg expression levels were significantly decreased in AML12-HBV1.3 cells cocultured with the supernatants of HBV-stimulated RAW264.7 macrophages. CONCLUSION: The results suggest that macrophages can endocytose HBV particles. Additionally, viral dsDNA can be recognized by DNA pattern recognition receptors, which in turn activate the cGAS-STING pathway, promoting the M1 polarization of macrophages, while no significant M2 polarization is observed. Macrophages stimulated with HBV particles exhibit enhanced antiviral activity against HBV.

Interferon-induced polarization of M1 macrophages mediates antiviral activity against the hepatitis B virus via the hepcidin-ferroportin axis.

BACKGROUNDS & AIMS: Given its ability to inhibit HBV replication, Interferon alpha (IFN-α) treatment has been confirmed to be effective in managing Chronic Hepatitis B (CHB). However, its underlying mechanisms are incompletely understood. METHODS: Herein, we investigated the antiviral properties of IFN-α by introducing IFN-α expression plasmids into a well-established HBV Hydrodynamic Injection (HDI) mouse model and examined the impact of IFN-α or hepcidin treatment on macrophages derived from THP-1 cells. The cytokine profiles were analyzed using the cytometry microsphere microarray technology, and flow cytometry was used to analyze the polarization of macrophages. Additionally, the IL-6/JAK2/STAT3 signaling pathway and the hepcidin-ferroportin axis were analyzed to better understand the macrophage polarization mechanism. RESULTS: As evidenced by the suppression of HBV replication, injection of an IFN-α expression plasmid and supernatants of IFN-α-treated macrophages exerted anti-HBV effects. The IFN-α treatment up-regulated IL-6 in mice with HBV replication, as well as in IFN-α-treated HepG2 cells and macrophages. Furthermore, JAK2/STAT3 signaling and hepcidin expression was promoted, inducing iron accumulation via the hepcidin-ferroportin axis, which caused the polarization of M1 macrophages. Furthermore, under the effect of IFN-α, IL-6 silencing or blockade downregulated the JAK2/STAT3 signaling pathway and hepcidin, implying that increased hepcidin expression under IFN-α treatment was dependent on the IL-6/JAK2/STAT3 pathway. CONCLUSION: The IL-6/JAK2/STAT3 signaling pathway is activated by IFN-α which induces hepcidin expression. The resulting iron accumulation then induces the polarization of M1 macrophages via the hepcidin-ferroportin axis, yielding an immune response which exerts antiviral effects against HBV replication.

Characteristics of immunological events in Epstein-Barr virus infection in children with infectious mononucleosis.

Backgrounds & aims: Epstein-Barr virus (EBV) infection occurs commonly in children and may cause acute infectious mononucleosis (AIM) and various malignant diseases. Host immune responses are key players in the resistance to EBV infection. We here assessed the immunological events and laboratory indicators of EBV infection, as well as determined the clinical usefulness of evaluating the severity and efficacy of antiviral therapy in AIM patients. Methods: We enrolled 88 children with EBV infection. The immune environment was defined by immunological events such as frequencies of lymphocyte subsets, phenotypes of T cells, and their ability to secrete cytokines, and so on. This environment was analyzed in EBV-infected children with different viral loads and in children in different phases of infectious mononucleosis (IM) from disease onset to convalescence. Results: Children with AIM had higher frequencies of CD3+ T and CD8+ T cells, but lower frequencies of CD4+ T cells and CD19+ B cells. In these children, the expression of CD62L was lower and that of CTLA-4 and PD-1 was higher on T cells. EBV exposure induced granzyme B expression, but reduced IFN-γ secretion, by CD8+ T cells, whereas NK cells exhibited reduced granzyme B expression and increased IFN-γ secretion. The frequency of CD8+ T cells was positively correlated with the EBV DNA load, whereas the frequencies of CD4+ T cells and B cells were negatively correlated. During the convalescent phase of IM, CD8+ T cell frequency and CD62L expression on T cells were restored. Moreover, patient serum levels of IL-4, IL-6, IL-10, and IFN-γ were considerably lower throughout the convalescent phase than throughout the acute phase. Conclusion: Robust expansion of CD8+ T cells, accompanied by CD62L downregulation, PD-1 and CTLA-4 upregulation on T cells, enhanced granzyme B production, and impaired IFN-γ secretion, is a typical characteristic of immunological events in children with AIM. Noncytolytic and cytolytic effector functions of CD8+ T cells are regulated in an oscillatory manner. Furthermore, the AST level, number of CD8+ T cells, and CD62L expression on T cells may act as markers related to IM severity and the effectiveness of antiviral treatment.