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Viruses usually exhibit strict species-specificity as a result of co-evolution with the host. Thus, in mouse models, a great barrier exists for analysis of infections with human-tropic viruses. Mouse models are unlikely to faithfully reproduce the human immune response to viruses or viral compounds and it is difficult to evaluate human therapeutic efficacy with antiviral reagents in mouse models. Humans and mice essentially have different immune systems, which makes it difficult to extrapolate mouse results to humans. In addition, apart from immunological reasons, viruses causing human diseases do not always infect mice because of species tropism. One way to determine tropism would be a virus receptor that is expressed on affected cells. The development of gene-disrupted mice and Tg mice, which express human receptor genes, enables us to analyze several viral infections in mice. Mice are, indeed, susceptible to human viruses when artificially infected in receptor-supplemented mice. Although the mouse cells less efficiently permit viral replication than do human cells, the models for analysis of human viruses have been established in vivo as well as in vitro, and explain viral pathogenesis in the mouse systems. In most systems, however, nucleic acid sensors and type I interferon suppress viral propagation to block the appearance of infectious manifestation. We herein review recent insight into in vivo antiviral responses induced in mouse infection models for typical human viruses.

Eye spray influenza vaccines for chickens are increasingly available; however, how to enhance cellular and antibody responses to them remains undetermined. Here, eye-drops containing the immune-enhancing adjuvants Pam2CSK4 or polyI:C were assessed in chickens. Application of these TLR agonists to chicken conjunctiva resulted in up-regulation of IL-1β, but not other cytokines, including IFN and IL-6, in the spleen, lung and Harderian gland. Thus, responses to adjuvant applied to the conjunctival mucosa of chickens differ from those expected from the responses to intra-nasal adjuvants in mammals. Identifying an appropriate delivery route for adjuvants is crucial for evoking immune responses in chickens.

Viral RNA represents a pattern molecule that can be recognized by RNA sensors in innate immunity. Humans and mice possess cytoplasmic DNA/RNA sensors for detecting viral replication. There are a number of DEAD (Asp-Glu-Ala-Asp; DExD/H) box-type helicases in mammals, among which retinoic acid-inducible gene 1 (RIG-I) and melanoma differentiation-associated protein 5 (MDA50) are indispensable for RNA sensing; however, they are functionally supported by a number of sensors that directly bind viral RNA or replicative RNA intermediates to convey signals to RIG-I and MDA5. Some DEAD box helicase members recognize DNA irrespective of the origin. These sensors transmit IFN-inducing signals through adaptors, including mitochondrial antiviral signaling. Viral double-stranded RNAs are reportedly sensed by the helicases DDX1, DDX21, DHX36, DHX9, DDX3, DDX41, LGP2 and DDX60, in addition to RIG-I and MDA5, and induce type I IFNs, thereby blocking viral replication. Humans and mice have all nucleic acid sensors listed here. In the RNA sensing system in chicken, it was found in the present study that most DEAD box helicases are conserved; however, DHX9 is genetically deficient in addition to reported RIG-I. Based on the current genome databases, similar DHX9 deficiency was observed in ducks and several other bird species. Because chicken, but not duck, was found to be deficient in RIG-I, the RNA-sensing system of chicken lacks RIG-I and DHX9 and is thus more fragile than that of duck or mammal. DHX9 may generally compensate for the function of RIG-I and deficiency of DHX9 possibly participates in exacerbations of viral infection such as influenza in chickens.

Although adenovirus 5 E1A-binding protein (BS69) is a nuclear protein acting as a transcriptional repressor, we found by an yeast two-hybrid and human cell immunoprecipitation another cytoplasmic function for this protein. BS69 bound Toll-interleukin 1 receptor domain (TIR)-containing adaptor molecule-1 (TICAM-1) (also named TRIF), an adaptor protein that couples with TLR3 around the endosome. BS69 translocated from the nucleus to the cytoplasm when cells were stimulated with dsRNA or transfected with TICAM-1. Confocal analysis of cells with over-expressed TICAM-1 or those stimulated with dsRNA revealed the characteristic “TICAM-1 speckle”, which reflects signalosome formation necessary for the activation of NF-κB and IFN-regulatory factor (IRF)-3. BS69 was involved in the TICAM-1 complex, and the activation of NF-κB/IRF-3 followed by cytokine production was augmented in the presence of BS69 overexpression. Knockdown of endogenous BS69 resulted in a decrease of IFN-β induction, suggesting that BS69 is a positive regulator for the TLR3-TICAM-1 pathway. These results, together with a recent report showing the negative regulatory properties of BS69 in NF-κB activation by EBV-derived latent membrane protein 1, suggest that BS69 harbors dual modes of cytoplasmic NF-κB regulation, positively in the TICAM-1 pathway and negatively in the latent membrane protein 1 pathway.

Caveolin-1 (Cav-1) has been suggested to function as a negative regulator of mitogen-stimulated proliferation and the Ras-p42/44 ERK (MAP kinase) pathway in a variety of cell types. However, the molecular basis of this suppression has not been clarified. Spred/Sprouty family proteins are also negative regulators of the ERK pathway by interacting with Raf-1. The Spred/Sprouty family proteins contain a cysteine-rich (CR) domain at the C-terminus, which is thought to be palmitoylated like Cav-1 and necessary for membrane anchoring. In this study, we demonstrated that Spred-1 localized in cholesterol-rich membrane raft/caveola fractions and interacted with Cav-1. To clarify the biological effect of Cav-1/Spred-1 interaction, we used hematopoietic cells that lacked expression of caveolins but expressed Spred-1. Forced expression of Cav-1 suppressed SCF- and IL-3-induced proliferation and ERK activation. Furthermore, forced expression of exogenous Spred-1 in Cav-1-expressing cells further suppressed proliferation and ERK activation. These data suggest that Spred-1 inhibits ERK activation in collaboration with Cav-1.

Basal forebrain cholinergic neurons (BFCNs) are involved in cognitive functions such as learning and memory, and are affected in several neurodegenerative diseases (e.g. Alzheimer's disease). Despite their importance, the molecular mechanisms of their development are not fully elucidated. A recent report demonstrated that some BFCNs in adult rat are positive for L3/Lhx8, a LIM homeobox transcription factor. To examine the function of L3/Lhx8 in the development of BFCNs, we generated L3/Lhx8 gene-disrupted mice. In these mice, cells expressing cholinergic neuron markers, such as choline acetyltransferase, vesicular acetylcholine transporter and p75 low-affinity NGF receptor, were markedly reduced in the basal forebrain, whereas other cholinergic neurons including brain stem and spinal motor neurons expressed the markers. Neurotransmitter phenotypes other than cholinergic in the basal forebrain appeared intact. From these results, we suggested that L3/Lhx8 has a pivotal and specific role in the development and/or maintenance of BFCNs.

Structured Abstract Authors– Zhang Y, Mori T, Takaki H, Takeuchi M, Iseki K, Hagino S, Murakawa M, Yokoya S, Wanaka A. Objectives– To compare and contrast the gene expression of two LIM-homeobox type transcription factors, Lhx6 and L3/Lhx8, in secondary palate formation. Methods– In situ hybridization histochemistry with digoxygenin (DIG) labelled cRNA probes specific for Lhx6 and L3/Lhx8. Materials– Serial cryo-sections of embryonic day (E)13.5, 14.5, and 15.5 mice (C57BL/6). Outcome Measure– Comparison of the signal intensities of NBT/BCIP precipitate by alkaline phosphatase conjugated anti-DIG antibody. Results– From E13.5 to E15.5, Lhx6 and L3/Lhx8 signals are detected in palatal mesenchyme, but the L3/Lhx8 signal is much more intense than the Lhx6 signal. In palatal epithelium, covering the mesenchyme, Lhx6 mRNA is transiently expressed at E14.5, while L3/Lhx8 mRNA expression is never detected throughout the development. Conclusion– Lhx6 and L3/Lhx8 functions may be partially redundant in the mesenchyme of the secondary palate, but not in the palatal epithelium.