Enterovirus 71 (EV71) is a positive single-stranded RNA (ssRNA) virus from the enterovirus genus of Picornaviridae family and causes diseases ranged from the mild disease of hand, foot and mouth disease (HFMD) to the severe disease of neurological involvement in young children. TLR7 is an intracellular pattern recognition receptor (PRR) recognizing viral ssRNA. In this study, we investigated the role of TLR7 in EV71 infection in mouse pups (10-12 days old) and found that wild-type (WT) and TLR7 knock-out (TLR7KO) mice infected with EV71 showed similar limb paralysis at the onset and peak of the disease, comparable loss of motor neurons, and similar levels of antiviral molecules in the spinal cord. These results suggest that TLR7 is not the absolute PRR for EV71 in the spinal cord. Interestingly, TLR7KO mice infected with EV71 exhibited significantly delayed recovery from limb paralysis compared with WT mice. TLR7KO mice infected with EV71 showed significantly decreased levels of IgM and IgG2, important antibodies for antiviral humoral immunity. Furthermore, TLR7KO mice infected with EV71 showed a decrease of germinal center B cells in the spleen compared with WT mice. Altogether, our study suggests that TLR7 plays a critical role in anti-viral humoral immunity rather than in being a PRR in the spinal cord during EV71 infection in young mice.
Enterovirus 71 (EV71) is a positive single-stranded RNA virus from the enterovirus genus of the Picornaviridae family. Most young children infected with EV71 develop mild symptoms of hand, foot and mouth disease, but some develop severe symptoms with neurological involvement. Limb paralysis from EV71 infection is presumed to arise mainly from dysfunction of motor neurons in the spinal cord. However, EV71 also targets and damages skeletal muscle, which may also contribute to the debilitating symptoms. In this study, we have delineated the impacts of EV71 infection on skeletal muscle using a mouse model. Mouse pups infected with EV71 developed limb paralysis, starting at day 3 post-infection and peaking at day 5-7 post-infection. At later times, mice recovered gradually but not completely. Notably, severe disease was associated with high levels of myositis accompanied by muscle calcification and persistent motor end plate abnormalities. Interestingly, macrophages exhibited a dynamic change in phenotype, with inflammatory macrophages (CD45+CD11b+Ly6Chi) appearing in the early stage of infection and anti-inflammatory/restorative macrophages (CD45+CD11b+Ly6Clow/-) appearing in the late stage. The presence of inflammatory macrophages was associated with severe inflammation, while the restorative macrophages were associated with recovery. Altogether, we have demonstrated that EV71 infection causes myositis, muscle calcification and structural defects in motor end plates. Subsequent muscle regeneration is associated with a dynamic change in macrophage phenotype.
MDA5, a member of the RIG-I like receptor family, has been shown to sense HBV DNA and trigger the production of anti-viral molecules to clear the virus. However, the mechanism underlying the suppression of HBV replication mediated by MDA5 signaling remains to be investigated. Our transcriptome analysis using RNA-seq revealed that IFN-λ1, a member of type III interferons, was the most upregulated molecule in Huh7 cells co-transfected with HBV DNA and MDA5 expression plasmid compared to with HBV DNA and RIG-I expression plasmid. Here we aim to investigate the IFN-λ1 expression in MDA5-mediated suppression of HBV replication. Huh7 cells co-transfected with HBV DNA and MDA5 expression plasmid led to increased IFN-λ1 expression associated with decreased HBsAg and HBV RNA. On the other hand, knockdown of MDA5 dramatically impaired IFN-λ1 expression. We next investigated the transcription factors involved in regulating IFN-λ1 expression. IRF1, but not IRF3 and IRF7, was upregulated in Huh7 cells co-transfected with HBV DNA and MDA5 expression plasmid. Knockdown of IRF1 led to reduced IFN-λ1 expression along with reduced inhibitory effect on HBV replication. The promoter region of IFN-λ1 contains ISREs, potential sites for IRF binding. However, ChIP and luciferase reporter assays showed no evidence of direct binding of IRF1 to the ISRE sites of IFN-λ1 promoter. Therefore, it is likely that IRF1 regulates MDA5-mediated IFN-λ1 expression through other mechanism. Mechanism(s) on IRF1 regulating IFN-λ1 expression in MDA5-mediated suppression of HBV replication is currently under investigation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.