Inhibitory effects of baicalein against herpes simplex virus type 1

Herpes simplex virus type 1(HSV-1)is a ubiquitous and widespread human pathogen,which gives rise to a range of diseases,including cold sores,corneal blindness,and encephalitis.Currently,the use of nucleoside analogs,such as acyclovir and penciclovir,in treating HSV-1 infection often presents limitation due to their side effects and low efficacy for drug-resistance strains.Therefore,new anti-herpetic drugs and strategies should be urgently developed.Here,we reported that baicalein,a naturally derived compound widely used in Asian countries,strongly inhibited HSV-1 replication in several models.Baicalein was effective against the replication of both HSV-1/F and HSV-1/Blue(an acyclovir-resistant strain)in vitro.In the ocular inoculation mice model,baicalein markedly reduced in vivo HSV-1/F replication,receded inflammatory storm and attenuated histological changes in the cornea.Consistently,baicalein was found to reduce the mortality of mice,viral loads both in nose and trigeminal ganglia in HSV-1 intranasal infection model.Moreover,an ex vivo HSV-1-EGFP infection model established in isolated murine epidermal sheets confirmed that baicalein suppressed HSV-1 replication.Further investigations unraveled that dual mechanisms,inactivating viral particles and inhibiting IκB kinase beta(IKK-β)phosphorylation,were involved in the anti-HSV-1 effect of baicalein.Collectively,our findings identified baicalein as a promising therapy candidate against the infection of HSV-1,especially acyclovir-resistant strain.

Novel insights into stress-induced susceptibility to influenza:corticosterone impacts interferon-βresponses by Mfn2-mediated ubiquitin degradation of MAVS

Although stress has been known to increase the susceptibility of pathogen infection,the underlying mechanism remains elusive.In this study,we reported that restraint stress dramatically enhanced the morbidity and mortality of mice infected with the influenza virus(H1N1)and obviously aggravated lung inflammation.Corticosterone(CORT),a main type of glucocorticoids in rodents,was secreted in the plasma of stressed mice.We further found that this stress hormone significantly boosted virus replication by restricting mitochondrial antiviral signaling(MAVS)protein-transduced IFN-βproduction without affecting its mRNA level,while the deficiency of MAVS abrogated stress/CORT-induced viral susceptibility in mice.Mechanistically,the effect of CORT was mediated by proteasome-dependent degradation of MAVS,thereby resulting in the impediment of MAVS-transduced IFN-βgeneration in vivo and in vitro.Furthermore,RNA-seq assay results indicated the involvement of Mitofusin 2(Mfn2)in this process.Gain-and loss-offunction experiments indicated that Mfn2 interacted with MAVS and recruited E3 ligase SYVN1 to promote the polyubiquitination of MAVS.Co-immunoprecipitation experiments clarified an interaction between any two regions of Mfn2(HR1),MAVS(C-terminal/TM)and SYVN1(TM).Collectively,our findings define the Mfn2-SYVN1 axis as a new signaling cascade for proteasome-dependent degradation of MAVS and a‘fine tuning’of antiviral innate immunity in response to influenza infection under stress.