Death by deamination: a novel host restriction system for HIV-1.

A human gene with potent antiretroviral activity has recently been found to encode a new member of the family of cytidine deaminases, previously known to be involved in mRNA editing, immunoglobulin gene class switching, and immunoglobulin gene hypermutation. The enzyme attacks viral DNA as it is synthesized in infected cells and prevents the formation of functional proviruses. The Vif gene of HIV-1 blocks this host restriction and so allows virus replication.