Wikipedia
Vpr is a Human immunodeficieny viral gene and protein product.
Vpr stands for "Viral Protein R". Vpr, a 96 amino acid 14-kDa protein, plays an important role in regulating nuclear import of the HIV-1 pre-integration complex, and is required for virus replication in non-dividing cells such as macrophages. Vpr also induces G2 cell cycle arrest and apoptosis in proliferating cells, which can result in immune dysfunction.
Vpr is also immunosuppressive due to its ability to sequester a proinflammatory transcriptional activator in the cytoplasm. HIV-2 contains both a Vpr protein and a related (by sequence homology) Vpx protein (Viral Protein X). Two functions of Vpr in HIV-1 are split between Vpr and Vpx in HIV-2, with the HIV-2 Vpr protein inducing cell cycle arrest and the Vpx protein required for nuclear import.