Tetherin is an alpha interferon-inducible cellular factor that impairs the release of many enveloped viruses, including human immunodeficiency virus type 1 (HIV-1), HIV-2, other retroviruses, Lassa virus-like particles (VLPs), Marburg and Ebola VLPs. Tetherin may also act as an innate immune sensor of viral infections that activates NF-kappaB to induce an inflammatory response.
Several viruses manage to circumvent the antiviral activity of tetherin. The Vpu protein form HIV-1 bridges tetherin to BTRC, a substrate recognition subunit of the Skp1/Cullin/F-box protein E3 ubiquitin ligase, inducing its ubiquitination and subsequent proteasomal degradation. HIV-2 instead downregulates cell surface expression of tetherin, restricting it to the trans-Golgi network via direct interaction with the viral glycoprotein.