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Humans have a close phylogenetic relationship with nonhuman primates (NHPs) and share many physiological parallels, such as highly similar immune systems, with them. Importantly, NHPs can be infected with many human or related simian viruses. In many cases, viruses replicate in the same cell types as in humans, and infections are often associated with the same pathologies. In addition, many reagents that are used to study the human immune response cross-react with NHP molecules. As such, NHPs are often used as models to study viral vaccine efficacy and antiviral therapeutic safety and efficacy and to understand aspects of viral pathogenesis. With several emerging viral infections becoming epidemic, NHPs are proving to be a very beneficial benchmark for investigating human viral infections.

The AIM2 inflammasome induces maturation of the proinflammatory cytokines IL-1β and IL-18. Using AIM2-deficient mice, Fitzgerald and colleagues and Alnemri and colleagues show that the AIM2 inflammasome is essential for host defense against cytosolic bacteria and DNA viruses. Inflammasomes regulate the activity of caspase-1 and the maturation of interleukin 1β (IL-1β) and IL-18. AIM2 has been shown to bind DNA and engage the caspase-1-activating adaptor protein ASC to form a caspase-1-activating inflammasome. Using Aim2 -deficient mice, we identify a central role for AIM2 in regulating caspase-1-dependent maturation of IL-1β and IL-18, as well as pyroptosis, in response to synthetic double-stranded DNA. AIM2 was essential for inflammasome activation in response to Francisella tularensis , vaccinia virus and mouse cytomegalovirus and had a partial role in the sensing of Listeria monocytogenes . Moreover, production of IL-18 and natural killer cell–dependent production of interferon-γ, events critical in the early control of virus replication, were dependent on AIM2 during mouse cytomegalovirus infection in vivo . Collectively, our observations demonstrate the importance of AIM2 in the sensing of both bacterial and viral pathogens and in triggering innate immunity.

The DNA sensor cGMP-AMP synthase (cGAS) senses cytosolic microbial or self DNA to initiate a MITA/STING-dependent innate immune response. cGAS is regulated by various posttranslational modifications at its C-terminal catalytic domain. Whether and how its N-terminal unstructured domain is regulated by posttranslational modifications remain unknown. We identified the acetyltransferase KAT5 as a positive regulator of cGAS-mediated innate immune signaling. Overexpression of KAT5 potentiated viral-DNA–triggered transcription of downstream antiviral genes, whereas a KAT5 deficiency had the opposite effects. Mice with inactivated Kat5 exhibited lower levels of serum cytokines in response to DNA virus infection, higher viral titers in the brains, and more susceptibility to DNA-virus–induced death. Mechanistically, KAT5 catalyzed acetylation of cGAS at multiple lysine residues in its N-terminal domain, which promoted its DNA-binding ability. Our findings suggest that KAT5-mediated cGAS acetylation at its N terminus is important for efficient innate immune response to DNA virus.

Drosophila melanogaster has played a key role in our understanding of invertebrate immunity. However, both functional and evolutionary studies of host-virus interaction in Drosophila have been limited by a dearth of native virus isolates. In particular, despite a long history of virus research, DNA viruses of D. melanogaster have only recently been described, and none have been available for experimental study. Here we report the isolation and comprehensive characterisation of Kallithea virus, a large double-stranded DNA virus, and the first DNA virus to have been reported from wild populations of D. melanogaster. We find that Kallithea virus infection is costly for adult flies, reaching high titres in both sexes and disproportionately reducing survival in males, and movement and late fecundity in females. Using the Drosophila Genetic Reference Panel, we quantify host genetic variance for virus-induced mortality and viral titre and identify candidate host genes that may underlie this variation, including Cdc42-interacting protein 4. Using full transcriptome sequencing of infected males and females, we examine the transcriptional response of flies to Kallithea virus infection and describe differential regulation of virus-responsive genes. This work establishes Kallithea virus as a new tractable model to study the natural interaction between D. melanogaster and DNA viruses, and we hope it will serve as a basis for future studies of immune responses to DNA viruses in insects.

Polyinosinic:polycytidylic acid (poly(I:C)) is a ligand of toll-like receptor (TLR) 3 that has been used as an immunostimulant in humans and mice against viral diseases based on its ability to enhance innate and adapt immunity. Antiviral effect of poly(I:C) has also been observed in teleost, however, the underling mechanism is not clear. In this study, we investigated the potential and signaling mechanism of poly(I:C) as an antiviral agent in a model of Japanese flounder (Paralichthys olivaceus) infected with megalocytivirus. We found that poly(I:C) exhibited strong antiviral activity and enhanced activation of head kidney macrophages and peripheral blood leukocytes. In vivo studies showed that (i) TLR3 as well as MDA5 knockdown reduced poly(I:C)-mediated immune response and antiviral activity to significant extents; (ii) when Myd88 was overexpressed in flounder, poly(I:C)-mediated antiviral activity was significantly decreased; (iii) when Myd88 was inactivated, the antiviral effect of poly(I:C) was significantly increased. Cellular study showed that (i) the NF-κB activity induced by poly(I:C) was upregulated in Myd88-overexpressing cells and unaffected in Myd88-inactivated cells; (ii) Myd88 overexpression inhibited and upregulated the expression of poly(I:C)-induced antiviral genes and inflammatory genes respectively; (iii) Myd88 inactivation enhanced the expression of the antiviral genes induced by poly(I:C). Taken together, these results indicate that poly(I:C) is an immunostimulant with antiviral potential, and that the immune response of poly(I:C) requires TLR3 and MDA5 and is negatively regulated by Myd88 in a manner not involving NK-κB. These results provide insights to the working mechanism of poly(I:C), TLR3, and Myd88 in fish.

Type I interferons (IFNs) are the first frontline of the host innate immune response against invading pathogens. Herein, we characterized an unknown protein encoded by phospholipase A2 inhibitor and LY6/PLAUR domain-containing (PINLYP) gene that interacted with TBK1 and induced type I IFN in a TBK1- and IRF3-dependent manner. Loss of PINLYP impaired the activation of IRF3 and production of IFN-β induced by DNA virus, RNA virus, and various Toll-like receptor ligands in multiple cell types. Because PINLYP deficiency in mice engendered an early embryonic lethality in mice, we generated a conditional mouse in which PINLYP was depleted in dendritic cells. Mice lacking PINLYP in dendritic cells were defective in type I IFN induction and more susceptible to lethal virus infection. Thus, PINLYP is a positive regulator of type I IFN innate immunity and important for effective host defense against viral infection.

Ranaviruses are capable of infecting both wild and farmed fish, amphibians, and reptiles, leading to significant economic losses and ecological risks. Currently, ranaviruses have been found in at least 175 species spanning six continents. Except for Singapore grouper iridovirus (SGIV), ranavirus genomes are generally regarded as highly methylated. Nevertheless, our comprehension of the methylation characteristics within ranaviruses remains limited. Despite the numerous genomes currently included in the GenBank database, a complete phylogenetic tree for ranaviruses has not yet been determined, and interspecific evolutionary relationships among ranaviruses have not been thoroughly investigated. In this study, the whole-genome methylation profile of mandarin fish ranavirus (MRV; a ranavirus) was investigated, revealing a methylation level of 16.04%, and hypomethylation of the MRV genome was detrimental to viral replication, speculating the genome methylation may play an important role in MRV replication. Furthermore, by combining with whole-genome DNA sequence phylogenetic analyses, we propose the possibility of an interspecies evolutionary relationship among ranaviruses, with the presence of four distinct evolutionary lineages within ranavirus evolution: \"SGIV, SCRAV(MRV/LMBV), EHNV/ENARV/ATV, and CMTV/FV3\", which might be also supported by the genomic collinearity, natural host range and host habitats. Furthermore, ranavirus genomic methylation levels may provide additional evidence for this hypothesis, but further proof is needed. Our work enhances the understanding of the role of genome methylation in ranaviruses and is beneficial for the prevention and control of ranavirus diseases; simultaneously, the proposed evolutionary hypothesis of ranavirus provides novel insights and ideas for exploring the evolutionary trajectory of viruses.

The disease caused by Largemouth bass ranavirus (LMBV) is one of the most severe viral diseases in largemouth bass (Micropterus salmoides). It is crucial to evaluate the genetic resistance of largemouth bass to LMBV and develop markers for disease-resistance breeding. In this study, 100 individuals (45 resistant and 55 susceptible) were sequenced and evaluated for resistance to LMBV and a total of 2,579,770 variant sites (SNPs-single-nucleotide polymorphisms (SNPs) and insertions–deletions (InDels)) were identified. A total of 2348 SNPs-InDels and 1018 putative candidate genes associated with LMBV resistance were identified by genome-wide association analyses (GWAS). Furthermore, GO and KEGG analyses revealed that the 10 candidate genes (MHC II, p38 MAPK, AMPK, SGK1, FOXO3, FOXO6, S1PR1, IL7R, RBL2, and GADD45) were related to intestinal immune network for IgA production pathway and FoxO signaling pathway. The acquisition of candidate genes related to resistance will help to explore the molecular mechanism of resistance to LMBV in largemouth bass. The potential polymorphic markers identified in this study are important molecular markers for disease resistance breeding in largemouth bass.

Background Temperature is a crucial environmental determinant for the vitality and development of teleost fish, yet the underlying mechanisms by which they sense temperature fluctuations remain largely unexplored. Transient receptor potential (TRP) proteins, renowned for their involvement in temperature sensing, have not been characterized in teleost fish, especially regarding their temperature-sensing capabilities. Results In this study, a genome-wide analysis was conducted, identifying a total of 28 TRP genes in the mandarin fish Siniperca chuatsi . These genes were categorized into the families of TRPA, TRPC, TRPP, TRPM, TRPML, and TRPV. Despite notable variations in conserved motifs across different subfamilies, TRP family members shared common structural features, including ankyrin repeats and the TRP domain. Tissue expression analysis showed that each of these TRP genes exhibited a unique expression pattern. Furthermore, examination of the tissue expression patterns of ten selected TRP genes following exposure to both high and low temperature stress indicated the expression of TRP genes were responsive to temperatures changes. Moreover, the expression profiles of TRP genes in response to mandarin fish virus infections showed significant upregulation for most genes after Siniperca chuatsi rhabdovirus, mandarin fish iridovirus and infectious spleen and kidney necrosis virus infection. Conclusions This study characterized the TRP family genes in mandarin fish genome-wide, and explored their expression patterns in response to temperature stress and virus infections. Our work will enhance the overall understanding of fish TRP channels and their possible functions.

The mitogen-activated protein kinase (MAPK) pathway is a conserved signaling system that responds to extracellular signals and translates them into appropriate cellular responses. While multiple MAPK kinase kinases (MAP3Ks) play a crucial role in the step wise transmission of MAPK signals in response to the pathogen infection, little is known about the function of MAP3K15 (also known as apoptosis signal-regulated kinase 3, ASK3) in viral infection. Here, we provide evidence that shrimp MAP3K15 undergoes phosphorylation and activation during a DNA virus, white spot syndrome virus (WSSV) infection, the activated MAP3K15 interacted with the NF-кB homolog, Dorsal, to promote its nuclear translocation for expression of the coiled-coil-containing C-type lectin (CC-CL) and the viral immediate early ( ie ) genes. CC-CL then activates the JAK/STAT pathway as the ligand to its membrane receptor Domeless, driving the expression of more ie genes. In addition, the JNK/P38 signaling pathway is also activated to promote viral ie genes expression. Importantly, the viral amplification in a wide range of crustaceans were inhibited and the survival rates of host were improved effectively by suppressing MAP3K15 expression or utilizing SDK1, an inhibitor targeting the active form of MAP3K15, suggesting that the MAP3K15 has a critical and conserved function in viral infection. Taken together, this study elucidates a pivotal role and mechanism of MAP3K15 in DNA virus infection, providing novel insights and potential strategies for the control of WSSV infection in crustaceans aquaculture practice.