Deletion of the vpu Sequences prior to the env in a Simian–Human Immunodeficiency Virus Results in Enhanced Env Precursor Synthesis but Is Less Pathogenic for Pig-Tailed Macaques

The interferon-inducible antiviral factor BST-2 prevents several enveloped viruses, including HIV, from escaping infected cells. The HIV protein Vpu antagonizes this host defense. Little is known about the expression of BST-2 during HIV infection in vivo and whether it can be modulated to the host's advantage. We studied the expression of BST-2 on blood cells from HIV-infected patients during the acute and chronic phases of disease as well as after antiretroviral treatment (ART). The expression of BST-2 was increased on mononuclear leukocytes, including CD4-positive T lymphocytes from HIV-positive patients, compared to that on cells of uninfected controls. The expression of BST-2 was highest during acute infection and decreased to levels similar to those of uninfected individuals after ART. Treatment of primary blood mononuclear cells in vitro with alpha interferon or with Toll-like receptor (TLR) agonists increased the expression of BST-2 to levels similar to those found during infection in vivo. The interferon-induced levels were sufficient to overcome the Vpu protein in vitro, reducing the release of wild-type HIV. These data show that BST-2 is upregulated during HIV infection, consistent with its role as an interferon-stimulated gene. The data further suggest that this upregulation is sufficient to saturate the activity of Vpu and inhibit wild-type HIV.

mentioning

confidence: 99%

Upregulation of BST-2/Tetherin by HIV Infection In Vivo

Homann

Smith

Richman

2011

“…Vpu deletion is reported to enhance Env expression at the cell surface (55)(56)(57)(58)(59), which could account for the increase in virion infectivity observed for mutant strains. To investigate this, CEM-GXR reporter cells were infected with VSV-G-pseudotyped HIV-1 NL4.3 , HIV-1 VpuW22*/EnvN136Y , HIV-1 VpuI17R , or HIV-1 ⌬Vpu at an MOI of 0.3 in the absence or presence of SM111.…”

Section: Sm111mentioning

confidence: 99%

Novel Acylguanidine-Based Inhibitor of HIV-1

Moons

Tietjen

Miller

et al. 2016

The emergence of transmissible HIV-1 strains with resistance to antiretroviral drugs highlights a continual need for new therapies. Here we describe a novel acylguanidine-containing compound, 1-(2-(azepan-1-yl)nicotinoyl)guanidine (or SM111), that inhibits in vitro replication of HIV-1, including strains resistant to licensed protease, reverse transcriptase, and integrase inhibitors, without major cellular toxicity. At inhibitory concentrations, intracellular p24Gag production was unaffected, but virion release (measured as extracellular p24Gag ) was reduced and virion infectivity was substantially impaired, suggesting that SM111 acts at a late stage of viral replication. SM111-mediated inhibition of HIV-1 was partially overcome by a Vpu I17R mutation alone or a Vpu W22* truncation in combination with Env N136Y. These mutations enhanced virion infectivity and Env expression on the surface of infected cells in the absence and presence of SM111 but also impaired Vpu's ability to downregulate CD4 and BST2/tetherin. Taken together, our results support acylguanidines as a class of HIV-1 inhibitors with a distinct mechanism of action compared to that of licensed antiretrovirals. Further research on SM111 and similar compounds may help to elucidate knowledge gaps related to Vpu's role in promoting viral egress and infectivity. T he development and scale-up of effective combination antiretroviral therapies have significantly reduced human immunodeficiency virus type 1 (HIV-1)-related morbidity and mortality globally (1); however, selection and transmission of drug-resistant HIV-1 strains remain a concern (2, 3). Thus, new antivirals that overcome drug resistance or act via novel mechanisms are needed. Acylguanidines are a broad class of antiviral compounds that target ion channels and other host and viral factors (4-8). Their anti-HIV-1 activity is exemplified by 5-(N,N-hexamethylene) amiloride (HMA; Fig. 1A) (5, 6), as well as N-(5-(1-methyl-1H-pyrazol-4-yl)naphthalene-2-carbonyl)guanidine (BIT-225; Fig. 1B) (7). HMA and BIT-225 inhibit HIV-1 replication in monocyte-derived macrophages at low micromolar concentrations (6, 7). Moreover, treatment of infected cells with these compounds results in reduced budding and release of viral particles without affecting intracellular viral protein production, suggesting that blockade occurs at a late stage of viral replication (5, 7). IMPORTANCE New inhibitors of HIV-1 replication may be useful as therapeutics to counteract drug resistance and as reagents to perform more detailed studies of viral pathogenesis. SM111 is a small molecule that blocks the replication of wild-type and drug-resistant HIV-1 strains by impairing viral release and substantially reducing virion infectivity, most likely through its ability to preventHMA and BIT-225 are both reported to target the HIV-1 accessory protein Vpu, an ϳ81-amino-acid transmembrane protein that is found in HIV-1 and some simian immunodeficiency virus (SIV) lineages and enhances viral replication through multiple mechanisms (...

“…The Vpu protein and gene have both been extensively studied in the expectation that they might shed light on the unique pathogenesis of HIV-1. For example, although the Vpu protein is not essential for viral replication, removal of the vpu gene leads to a decrease in pathogenicity (44). The origin of vpu is unclear, but it may have arisen to enhance viral release as a result of increased affinity of the Env protein for the CD4 receptor (45).…”

mentioning

confidence: 99%

Characterization of a Novel Simian Immunodeficiency Virus (SIVmonNG1) Genome Sequence from a Mona Monkey (Cercopithecus mona)

Barlow

Ajao²,

Clewley

2003

A novel simian immunodeficiency virus (SIV) sequence has been recovered from RNA extracted from the serum of a mona monkey (Cercopithecus mona) wild born in Nigeria. The sequence was obtained by using novel generic (degenerate) PCR primers and spans from two-thirds into the gag gene to the 3 poly(A) tail of the SIVmonNG1 RNA genome. Analysis of the open reading frames revealed that the SIVmonNG1 genome codes for a Vpu protein, in addition to Gag, Pol, Vif, Vpr, Tat, Rev, Env, and Nef proteins. Previously, only lentiviruses infecting humans (human immunodeficiency virus type 1 [HIV-1]) and chimpanzees (SIVcpz) were known to have a vpu gene; more recently, this has also been found in SIVgsn from Cercopithecus nictitans. Overall, SIVmonNG1 most closely resembles SIVgsn: the env gene sequence groups with HIV-1/SIVcpz env sequences, whereas the pol gene sequence clusters closely with the pol sequence of SIVsyk from Cercopithecus albogaris. By bootscanning and similarity plotting, the first half of pol resembles SIVsyk, whereas the latter part is closer to SIVcol from Colobus guereza. The similarities between the complex mosaic genomes of SIVmonNG1 and SIVgsn are consistent with a shared or common lineage. These data further highlight the intricate nature of the relationships between the SIVs from different primate species and will be helpful for unraveling these associations.