Herpesviridae

• Has a nucleocapsid structure of an icosahedral with dsDNA, a linear genome and is enveloped
• Is a large virus 125-250kb encoding for 84 genes
• herpes simplex virus has Ul and Us and repeated sequenses
• There is Ul ( long) and Us (short) sections of the genome flanked with direct repeats An and A, and inverted repeats of B, B', C' and C
• Viral genes are sequentially expressed during replication cycle by host DNA dependent RNA polymerase II
• There is intermediate early genes (IE)- expressed within the first hour and needed for early gene expression + modulating the host defenses
• Early genes (b) are expressed 4-8 hours post infection, needed for DNA replication
• Late genes (g1 and g2)- is after onset of DNA replication and is needed for virion assembly+tegument proteins
• Surface proteins are gH/gL fusion regulators, gD fusion trigger
• the two methods of entry: fustion at the plasma membrane ot endocytosis. the virion can escape the endosome in any ph enviroment, then nucleocapsid is brought to nucelar pore complex where linear geneome is fed through the pore to the nucleus
• one linear genome is in the nucleus it becomes a circle and host nuclease and transcription allow for viral gene replication
• Tehument proteins are encoded in late genes but are packaged in the virion meaning it could play a part with the early genes
• VhS protein-Viral protein for Host Shut off : RNase like enzyme to mediate degradation of cellular mRNAs
• Vp16 protein will form complexes with Tf, Oct-1, and HCF-1. the complex then binds to response elements up stream of promoter to activate expression
• what IE genes disarm the host defences?

  ICP47- bind TAP blocking antigen presentation

  ICP34.5 will reverse PKR effect on the translation by phosphorylation of EIF2a

  ICP0 induces histone acetylation= activating transcription

  ICP27 will block the splicing of pre-mRNA inpeeding RNA synthesis.
• Bidirectional replication: DNA replicates in both directions, from 5' to 3'

  using Ul9, Ul29, Ul5,8,25, Ul30, Ul42
• Rolling circle:

  will create concatemers _> long continuous DNA that contains multiple copies of same sequence, proteins on the nucleocapsid will recognize AAAAA and cleave to allow for packaging
• Latent infection: few/no viral genes are expressed and no virions are produces but virus still present and replicating