Dual role of the chromatin-binding factor PHF13 in the pre- and post-integration phases of HIV-1 replication.

Viruses interact with multiple host cell factors. Some of these are required to promote viral propagation, others have roles in inhibiting infection. Here, we delineate the function of the cellular factor PHF13 (or SPOC1), a putative HIV-1 restriction factor.

T cells with low CD2 levels express reduced restriction factors and are preferentially infected in therapy naïve chronic HIV-1 patients.

Introduction: Restriction factors (RFs) suppress HIV-1 in cell lines and primary cell models. Hence, RFs might be attractive targets for novel antiviral strategies, but their importance for virus control is controversial.

Methods: We profiled the expression of RFs in primary blood-derived mononuclear cells (PBMC) from therapy-naïve HIV-1 patients and quantified infection.

Ion Channel Activity of Vpu Proteins Is Conserved throughout Evolution of HIV-1 and SIV.

The human immunodeficiency virus type 1 (HIV-1) protein Vpu is encoded exclusively by HIV-1 and related simian immunodeficiency viruses (SIVs). The transmembrane domain of the protein has dual functions: it counteracts the human restriction factor tetherin and forms a cation channel. Since these two functions are causally unrelated it remains unclear whether the channel activity has any relevance for viral release and replication.

Virion encapsidated HIV-1 Vpr induces NFAT to prime non-activated T cells for productive infection.

The majority of T cells encountered by HIV-1 are non-activated and do not readily allow productive infection. HIV-1 Vpr is highly abundant in progeny virions, and induces signalling and HIV-1 LTR transcription. We hence hypothesized that Vpr might be a determinant of non-activated T-cell infection.

HIV-1 Nef and Vpu Interfere with L-Selectin (CD62L) Cell Surface Expression To Inhibit Adhesion and Signaling in Infected CD4+ T Lymphocytes.

Unlabelled: Leukocyte recirculation between blood and lymphoid tissues is required for the generation and maintenance of immune responses against pathogens and is crucially controlled by the L-selectin (CD62L) leukocyte homing receptor. CD62L has adhesion and signaling functions and initiates the capture and rolling on the vascular endothelium of cells entering peripheral lymph nodes. This study reveals that CD62L is strongly downregulated on primary CD4(+) T lymphocytes upon infection with human immunodeficiency virus type 1 (HIV-1).

HIV-1 Vpu mediated downregulation of CD155 requires alanine residues 10, 14 and 18 of the transmembrane domain.

HIV-1 NL4-3 Vpu induces downregulation of cell surface CD155, a ligand for the DNAM-1 activating receptor of NK and CD8(+) T cells, to evade NK cell mediated immune response. Here we show that the conserved alanine residues at positions 10, 14 and 18 in the TM domain of Vpu are required for the efficient downregulation of cell surface CD155. In contrast, the CK-2 phosphorylation sites and the second α-helix in the cytoplasmic Vpu domain have no influence on the surface expression of CD155.

Analysis of determinants in filovirus glycoproteins required for tetherin antagonism.

The host cell protein tetherin can restrict the release of enveloped viruses from infected cells. The HIV-1 protein Vpu counteracts tetherin by removing it from the site of viral budding, the plasma membrane, and this process depends on specific interactions between the transmembrane domains of Vpu and tetherin. In contrast, the glycoproteins (GPs) of two filoviruses, Ebola and Marburg virus, antagonize tetherin without reducing surface expression, and the domains in GP required for tetherin counteraction are unknown.

HIV-1 Vpu affects the anterograde transport and the glycosylation pattern of NTB-A.

HIV-1 Vpu induces downregulation of cell surface NTB-A to evade lysis of HIV-1 infected cells by NK cells. Here we show that Vpu affects the anterograde transport and the glycosylation pattern of NTB-A by a mechanism that is distinct from the Vpu induced downregulation of CD4 and tetherin. In the presence of Vpu, only the high mannose form of NTB-A was detectable, suggesting that Vpu prevented the formation of the mature form of NTB-A.

Ion channel activity of HIV-1 Vpu is dispensable for counteraction of CD317.

While the C-terminal domain of HIV-1 Vpu is critical for CD4 degradation, the transmembrane domain (TM) mediates ion channel activity, enhances virus release and is essential for counteracting CD317/Bst-2/Tetherin. Here we analyzed whether the ion channel activity of Vpu is required to antagonize CD317-mediated restriction of virion release. We examined TM-mutants of three conserved residues: the S23A mutation, which was previously shown to abrogate ion channel function, did not affect Vpu mediated augmentation of virus release.