The cGas-Sting Signaling Pathway Is Required for the Innate Immune Response Against Ectromelia Virus.

Activation of the DNA-dependent innate immune pathway plays a pivotal role in the host defense against poxvirus. Cyclic GMP-AMP synthase (cGAS) is a key cytosolic DNA sensor that produces the cyclic dinucleotide cGMP-AMP (cGAMP) upon activation, which triggers stimulator of interferon genes (STING), leading to type I Interferons (IFNs) production and an antiviral response. Ectromelia virus (ECTV) has emerged as a valuable model for investigating the host-Orthopoxvirus relationship. However, the role of cGas-Sting pathway in response to ECTV is not clearly understood. Here, we showed that murine cells (L929 and RAW264.7) mount type I IFN responses to ECTV that are dependent upon cGas, Sting, TANK binding kinase 1 (Tbk1), and interferon regulatory factor 3 (Irf3) signaling. Disruption of cGas or Sting expression in mouse macrophages blocked the type I IFN production and facilitated ECTV replication. Consistently, mice deficient in cGas or Sting exhibited lower type I IFN levels and higher viral loads, and are more susceptible to mousepox. Collectively, our study indicates that the cGas-Sting pathway is critical for sensing of ECTV infection, inducing the type I IFN production, and controlling ECTV replication.

Comparison of Host Gene Expression Profiles in Spleen Tissues of Genetically Susceptible and Resistant Mice during ECTV Infection.

Ectromelia virus (ECTV), the causative agent of mousepox, has emerged as a valuable model for investigating the host-Orthopoxvirus relationship as it relates to pathogenesis and the immune response. ECTV is a mouse-specific virus and causes high mortality in susceptible mice strains, including BALB/c and C3H, whereas C57BL/6 and 129 strains are resistant to the disease. To understand the host genetic factors in different mouse strains during the ECTV infection, we carried out a microarray analysis of spleen tissues derived from BALB/c and C57BL/6 mice, respectively, at 3 and 10 days after ECTV infection. Differential Expression of Genes (DEGs) analyses revealed distinct differences in the gene profiles of susceptible and resistant mice. The susceptible BALB/c mice generated more DEGs than the resistant C57BL/6 mice. Additionally, gene ontology and KEGG pathway analysis showed the DEGs of susceptible mice were involved in innate immunity, apoptosis, metabolism, and cancer-related pathways, while the DEGs of resistant mice were largely involved in MAPK signaling and leukocyte transendothelial migration. Furthermore, the BALB/c mice showed a strong induction of interferon-induced genes, which, however, were weaker in the C57BL/6 mice. Collectively, the differential transcriptome profiles of susceptible and resistant mouse strains with ECTV infection will be crucial for further uncovering the molecular mechanisms of the host-Orthopoxvirus interaction.

Analysis of the CDR3 length repertoire and the diversity of T cell receptor α and ß chains in swine CD4+ and CD8+ T lymphocytes.

The T cell receptor (TCR) is a complex heterodimer that recognizes fragments of antigens as peptides and binds to major histocompatibility complex molecules. The TCR α and ß chains possess three hypervariable regions termed complementarity determining regions (CDR1, 2 and 3). CDR3 is responsible for recognizing processed antigen peptides. Immunoscope spectratyping is a simple technique for analyzing CDR3 polymorphisms and sequence length diversity, in order to investigate T cell function and the pattern of TCR utilization. The present study employed this technique to analyze CDR3 polymorphisms and the sequence length diversity of TCR α and ß chains in porcine CD4+ and CD8+ T cells. Polymerase chain reaction products of 19 TCR α variable regions (AV) and 20 TCR ß variable regions (BV) gene families obtained from the CD4+ and CD8+ T cells revealed a clear band following separation by 1.5% agarose gel electrophoresis, and each family exhibited >8 bands following separation by 6% sequencing gel electrophoresis. CDR3 spectratyping of all identified TCR AV and BV gene families in the sorted CD4+ and CD8+ T cells by GeneScan, demonstrated a standard Gaussian distribution with >8 peaks. CDR3 in CD4+ and CD8+ T cells demonstrated different expression patterns. The majority of CDR3 recombined in frame and the results revealed that there were 10 and 14 amino acid discrepancies between the longest and shortest CDR3 lengths in specific TCR AV and TCR BV gene families, respectively. The results demonstrated that CDR3 polymorphism and length diversity demonstrated different expression and utilization patterns in CD4+ and CD8+ T cells. These results may facilitate future research investigating the porcine TCR CDR3 gene repertoire as well as the functional complexity and specificity of the TCR molecule.

[Progress on host range factors and their mechanisms of poxvirus].

Poxvirus is one of the most serious zoonosis pathogens, which has largest genome and broadest host spectrum. With the development of molecular biology, functional genomics, and immunology-related technology, the interactions between pathogen and the host, particularly a large array of host range factors and their functions have been increasingly discovered. These findings provide references for the molecular basis of poxvirus tissue tropism and host specificity. This review focus on the introduction of host range factors in major members of Chordopoxvirinae to highlight the understanding of the mechanisms of molecular genetic evolution, the host tropism, and cross-species infection of poxviruses.

Infection of mouse bone marrow-derived immature dendritic cells with classical swine fever virus C-strain promotes cells maturation and lymphocyte proliferation.

In this study, the interactions of classical swine fever virus (CSFV) C-strain and the virulent GSLZ strain with mouse bone marrow-derived immature dendritic cells (BM-imDCs) were investigated for the first time. Both the C-strain and the virulent GSLZ strain could effectively infect and replicate in mouse BM-imDCs. C-strain-infected BM-imDCs showed a greatly enhanced degree of maturation, and could effectively promote the expansion and proliferation of allogeneic naive T cells. The C-strain induced a stronger Th1 response. Infection with the virulent GSLZ strain had no obvious influence on cell maturation or lymphocyte proliferation, and failed to induce any obvious immune response. The results of this study provided initial information for research of the immunologic mechanisms of CSFV using mouse DCs as the model cells.

[Modulation of the host toll-like receptor signaling pathways by virus infection].

Toll-like receptors (TLRs) are germline-encoded pattern recognition receptors (PRRs) that play a central role in host cell recognition and responses to virus infection, leading to the production of interferons (IFNs) and proinflammatory cytokines. In parallel, in order to establish an infection, viruses have to develop exclusively strategies to interfere with TLRs signaling, particularly some important adaptors activation such as MyD88, NF-kappaB, TRIF and IRFs, and suppress or escape host's antiviral immune response. In this paper, we review the latest findings on the various strategies used by viruses to modulate TLRs-mediated innate immune response, with special emphasis on immune evasion mechanism of VACV, HCV and HIV. By highlighting recent progress in these areas, we hope to convey a greater understanding of how viruses hamper TLRs signaling and how to overcome viral infection.