Tetherin/BST-2 Is Essential for the Formation of the Intracellular Virus-Containing Compartment in HIV-Infected Macrophages

Abstract

SUMMARY HIV-1 assembly and release occurs at the plasma membrane in T lymphocytes, while intracellular sites of virus assembly or accumulation are apparent in macrophages. The host protein tetherin (BST-2) inhibits HIV release from the plasma membrane by retaining viral particles at the cell surface, but the role of tetherin at intracellular HIV assembly sites is unclear. We determined that tetherin is significantly upregulated upon macrophage infection and localizes to an intracellular virus-containing compartment (VCC). Tetherin localized at the virus-VCC membrane interface, suggesting that tetherin physically tethers virions in VCCs. Tetherin knockdown diminished and redistributed VCCs within macrophages and promoted HIV release and cell-cell transmission. The HIV Vpu protein, which downregulates tetherin from the plasma membrane, did not fully overcome tetherin-mediated restriction of particle release in macrophages. Thus, tetherin is essential for VCC formation, and may account for morphologic differences in the apparent HIV assembly sites in macrophages versus T cells.

Three-Dimensional Structural Characterization of HIV-1 Tethered to Human Cells

“…8A and B). We did not observe tethers greater than 37 nm in length, as seen in selected images of chemically fixed samples imaged by conventional TEM (32,36,37). The distance between tethered virions was the same for mature (17.8 Ϯ 7.24 nm) and immature virions (17.9 Ϯ 6.31 nm), which suggests that HIV-1 maturation does not influence the length of the tether.…”

“…Immunoelectron microscopy studies have shown tetherin staining on viral membranes and on the host cell plasma membrane near sites of HIV-1 budding (23,32,37,38). Electron-dense fibrous material linking HIV-1 to the host cell membrane (37) and to virus-containing compartments in macrophages was observed (36). However, the length of these tethers (between 50 and 100 nm), which was inferred from TEM two-dimensional (2D) projection images and not 3D volumes, exceeded the length predicted by either tetherin model by an order of 3-to 6-fold.…”

“…Ultrastructural analysis of HIV-1 tethered to human cells has been limited chiefly to examinations of chemically fixed and heavy-metal-stained samples by either thin-section transmission electron microscopy (TEM) (1,9,23,32,(35)(36)(37)(38) or scanning electron microscopy (SEM) (2,23,39). In previous studies, clusters of HIV-1 virions retained on the surface of infected or transfected cells expressing tetherin were consistently observed.…”

Comparative Analysis of the Capacity of Elite Suppressor CD4 + and CD8 + T Cells To Inhibit HIV-1 Replication in Monocyte-Derived Macrophages

“…ϩ T cells, in part due to differences in the level of expression of retroviral restriction factors, such as tetherin, SAMHD1, and APOBEC3 (20)(21)(22). SAMHD1 specifically contributes to the lower concentration of deoxynucleoside triphosphates already found in macrophages, greatly inhibiting reverse transcription (23,24).…”

The role of BST‐2/Tetherin in host protection and disease manifestation

“…BST‐2 may enhance cell‐to‐cell viral spread by the formation of viral clusters 50. However, inhibition of cell‐to‐cell viral spread by BST‐2 could occur by initiation of virological synapses, by trapping viruses in intracellular compartments 51, 52, 53, or by eliciting antibody‐dependent cellular cytotoxicity (ADCC) 54, 55, 56 (Fig.…”