Function Of Varicella-Zoster Virus ORF7 And Novel Anterograde Neuronal Circuits Tracers Derived From Herpes Simplex Virus

The prevalence of neurotropic human alpha-herpesviruses has caused serious neuropathy and economic burdens on society.In this study,two projects based on human alpha-herpesviruses have been conducted as interpreted below.One was dedicated to decoding the function of a neurotropic factor of varicella-zoster virus(VZV);another was developing useful neuronal circuits viral tracers based on herpes simplex virus type 1(HSV-1).Although a VZV vaccine has been used for many years,the neuropathy caused by VZV infection is still a major health concern.ORF7 of VZV has been recognized as a neurotropic gene in vivo,but its neurovirulent role remains unclear.In the present study,we investigated the effect of ORF7 deletion on VZV replication cycle at virus entry,genome replication,expression of genes expression,capsid assembly and cytoplasmic envelopment,and transcellular transmission in differentiated neural progenitor cells(d NPCs)and neuroblastoma SH-SY5Y(dSY5Y)cells.Our results demonstrated that ORF7 protein is a component of the tegument layer of VZV virions.Deleting ORF7 did not affect viral entry,viral genome replication or expression of typical viral genes,but clearly impacted cytoplasmic envelopment of VZV capsids,resulting in a dramatic increase of envelop-defective particles and a decrease in intact virions.The defect was more severe in differentiated neuronal cells of dNPCs and dSY5 Y.ORF7 deletion also impaired transmission of ORF7-deficient virus among the neuronal cells.These results indicate that ORF7 is required for cytoplasmic envelopment of VZV capsids,virus transmission among neuronal cells and probably the neuropathy induced by VZV infection.In addition,we have created the anterograde multi-and mono-synaptic tracers derived from HSV-1 H129 strain.H129-G4 is a multi-synapticsynaptic tracer with labeling intensity strong enough to label the details of neuron morphology.H129-?TK-tdT represents a new bona fide potential novel anterograde mono-synapticsynaptic tracer,which provides a useful tool formay contribute in revealing the direct projectome connectivity.These tracers complement the current neuronal circuit tracer tool box.