With APOBEC3 is called an abbreviation of APOBEC3 proteins in which there are elements of the immune system to defend against retroviral infections. The name comes from the English and is an acronym for apolipoprotein B mRNA editing enzyme catalytic polypeptide 3 In the genome of humans and other primates at least five APOBEC3 proteins are coded: APOBEC3A, C, B, F and G. In other mammals, on the other hand only one APOBEC3 found. APOBEC3 is specifically packaged by the host cell into retroviral virions and acts via a deamination of dC residues to dU residues in the retroviral genome, resulting in G → A hypermutation and destabilization of the genetic material. By damaging the genetic material of the virus is no longer able to proliferate. The APOBEC3 protein family, together with the potent restriction factor tetherin and TRIM5α an important component of innate antiviral immunity.

The viral structures that recognizes APOBEC3 the virus particles are still unknown.

In the course of evolution, retroviruses mechanisms have evolved to escape the APOBEC3 - effects, be it either by changing the peptide sequences that are recognized by APOBEC3, or in complex retroviruses encoding accessory proteins, which are specifically directed against certain APOBEC3 proteins such as Vif in HIV or probably bet on foamy viruses. In human HIV infection play in this context, particularly APOBEC3G and 3F crucial roles, as they preferred to be found in the affected CD4 helper cells and, accordingly, also, Vif specifically acts against this, by binding to APOBEC3G and 3F and thus its incorporation into prevents the virion and it also supplies the cellular degradation machinery.