HHV Infected Cell Polypeptide 0 (ICP0)
HHV Infected Cell Polypeptide ICP0 (sometimes Infected Cell Protein 0) is a protein found in Herpes viruses. The gene from which ICP0 is produced is known as HHV α0. ICP0 is expressed and functions at the earliest stage of infection. This stage is known as the immediate-early or α ("alpha") phase of HHV gene expression.
- ICP0 is partially similar to the human protein CoREST. CoREST combines with other cellular proteins REST and histone deacetylases (HDAC); in turn this complex may silence viral gene expressions. ICP0 interferes with the HDAC/CoRest/Rest complex by dissociating HDAC1 from CoRest/Rest. 
- ICP0 blocks the Interferon pathway of cellular host antiviral response which otherwise would lead to production of RNase L and lead to host cell apoptosis. 
During latent infection a viral RNA transcript inhibits expression of the gene encoding ICP0 via an antisense RNA mechanism. The RNA transcript accumulates in host cells during latent infection and is known as Latency Associated Transcript.