The bovine lentivirus also known as the bovine immunodeficiency-like virus (BIV) has conserved and hypervariable regions in the surface envelope gene [1]. This family corresponds to the SU surface protein.

1: Size variation within the second hypervariable region of the surface envelope gene of the bovine lentivirus BIV in experimentally and naturally infected cattle. Suarez DL, Whetstone CA; J Virol 1997;71:2482-2486. PMID:9032387