scholarly journals Envelope Glycoprotein Internalization Protects Human and Simian Immunodeficiency Virus-Infected Cells from Antibody-Dependent Cell-Mediated Cytotoxicity

2015 ◽  
Vol 89 (20) ◽  
pp. 10648-10655 ◽  
Author(s):  
Benjamin von Bredow ◽  
Juan F. Arias ◽  
Lisa N. Heyer ◽  
Matthew R. Gardner ◽  
Michael Farzan ◽  
...  

ABSTRACTThe cytoplasmic tails of human and simian immunodeficiency virus (HIV and SIV, respectively) envelope glycoproteins contain a highly conserved, membrane-proximal endocytosis motif that prevents the accumulation of Env on the surface of infected cells prior to virus assembly. Using an assay designed to measure the killing of virus-infected cells by antibody-dependent cell-mediated cytotoxicity (ADCC), we show that substitutions in this motif increase the susceptibility of HIV-1- and SIV-infected cells to ADCC in a manner that directly correlates with elevated Env levels on the surface of virus-infected cells. In the case of HIV-1, this effect is additive with a deletion invpurecently shown to enhance the susceptibility of HIV-1-infected cells to ADCC as a result of tetherin-mediated retention of budding virions on the cell surface. These results reveal a previously unappreciated role for the membrane-proximal endocytosis motif of gp41 in protecting HIV-1- and SIV-infected cells from antibody responses by regulating the amount of Env present on the cell surface.IMPORTANCEThis study reveals an unappreciated role for the membrane-proximal endocytosis motif of gp41 in protecting HIV-1- and SIV-infected cells from elimination by Env-specific antibodies. Thus, strategies designed to interfere with this mechanism of Env internalization may improve the efficacy of antibody-based vaccines and antiretroviral therapies designed to enhance the immunological control of HIV-1 replication in chronically infected individuals.

2016 ◽  
Vol 90 (13) ◽  
pp. 6127-6139 ◽  
Author(s):  
Benjamin von Bredow ◽  
Juan F. Arias ◽  
Lisa N. Heyer ◽  
Brian Moldt ◽  
Khoa Le ◽  
...  

ABSTRACTAlthough antibodies to the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein have been studied extensively for their ability to block viral infectivity, little data are currently available on nonneutralizing functions of these antibodies, such as their ability to eliminate virus-infected cells by antibody-dependent cell-mediated cytotoxicity (ADCC). HIV-1 Env-specific antibodies of diverse specificities, including potent broadly neutralizing and nonneutralizing antibodies, were therefore tested for ADCC against cells infected with a lab-adapted HIV-1 isolate (HIV-1NL4-3), a primary HIV-1 isolate (HIV-1JR-FL), and a simian-human immunodeficiency virus (SHIV) adapted for pathogenic infection of rhesus macaques (SHIVAD8-EO). In accordance with the sensitivity of these viruses to neutralization, HIV-1NL4-3-infected cells were considerably more sensitive to ADCC, both in terms of the number of antibodies and magnitude of responses, than cells infected with HIV-1JR-FLor SHIVAD8-EO. ADCC activity generally correlated with antibody binding to Env on the surfaces of virus-infected cells and with viral neutralization; however, neutralization was not always predictive of ADCC, as instances of ADCC in the absence of detectable neutralization, and vice versa, were observed. These results reveal incomplete overlap in the specificities of antibodies that mediate these antiviral activities and provide insights into the relationship between ADCC and neutralization important for the development of antibody-based vaccines and therapies for combating HIV-1 infection.IMPORTANCEThis study provides fundamental insights into the relationship between antibody-dependent cell-mediated cytotoxicity (ADCC) and virus neutralization that may help to guide the development of antibody-based vaccines and immunotherapies for the prevention and treatment of HIV-1 infection.


2005 ◽  
Vol 79 (13) ◽  
pp. 8560-8571 ◽  
Author(s):  
Marie-Christine Dazza ◽  
Michel Ekwalanga ◽  
Monique Nende ◽  
Karhemere Bin Shamamba ◽  
Pitchou Bitshi ◽  
...  

ABSTRACT We report the identification of a new simian immunodeficiency virus (SIV), designated SIVden, in a naturally infected Dent's Mona monkey (Cercopithecus mona denti), which was kept as pet in Kinshasa, capital of the Democratic Republic of Congo. SIVden is genetically distinct from the previously characterized primate lentiviruses. Analysis of the full-length genomic sequence revealed the presence of a vpu open reading frame. This gene is also found in the virus lineage of human immunodeficiency virus type 1 (HIV-1) and chimpanzee immunodeficiency virus (SIVcpz) and was recently described in viruses isolated from Cercopithecus nictitans, Cercopithecus mona, and Cercopithecus cephus. The SIVden vpu coding region is shorter than the HIV-1/SIVcpz and the SIVgsn, SIVmon, and SIVmus counterparts. Unlike Pan troglodytes schweinfurthii viruses (SIVcpzPts) and Cercopithecus monkey viruses (SIVgsn, SIVmon, and SIVmus), the SIVden Vpu contains the characteristic DSGXES motif which was shown to be involved in Vpu-mediated CD4 and IκBα proteolysis in HIV-1 infected cells. Although it harbors a vpu gene, SIVden is phylogenetically closer to SIVdeb isolated from De Brazza's monkeys (Cercopithecus neglectus), which lacks a vpu gene, than to Cercopithecus monkey viruses, which harbor a vpu sequence.


2002 ◽  
Vol 76 (8) ◽  
pp. 4125-4130 ◽  
Author(s):  
Enrique Argañaraz ◽  
María José Cortés ◽  
Sydney Leibel ◽  
Juan Lama

ABSTRACT The CD4 receptor is required for the entry of human immunodeficiency virus (HIV) into target cells. It has long been known that Nef, Env, and Vpu participate in the removal of the viral receptor from the cell surface. Recently, it has been proposed that the HIV type 1 (HIV-1) Vpr protein may also play a role in the downmodulation of CD4 from the surfaces of infected cells (L. Conti, B. Varano, M. C. Gauzzi, P. Matarrese, M. Federico, W. Malorani, F. Belardelli, and S. Gessani, J. Virol. 74:10207-10211, 2000). To investigate the possible role of Vpr in the downregulation of the viral receptor Vpr alleles from HIV-1 and simian immunodeficiency virus were transiently expressed in transformed T cells and in 293T fibroblasts, and their ability to modulate surface CD4 was evaluated. All Vpr alleles efficiently arrested cells in the G2 stage of the cell cycle. However, none of the tested Vpr proteins altered the expression of CD4 on the cell surface. In comparison, HIV-1 Nef efficiently downmodulated surface CD4 in all the experimental settings. Transformed T cells and primary lymphocytes were challenged with wild-type, Nef-defective, and Vpr-defective viruses. A significant reduction in the HIV-induced downmodulation of surface CD4 was observed in viruses lacking Nef. However, Vpr-deletion-containing viruses showed no defect in their ability to remove CD4 from the surfaces of infected cells. Our results indicate that Vpr does not play a role in the HIV-induced downmodulation of the CD4 receptor.


2017 ◽  
Vol 91 (18) ◽  
Author(s):  
Christoph H. Fellinger ◽  
Matthew R. Gardner ◽  
Charles C. Bailey ◽  
Michael Farzan

ABSTRACT Rhesus macaques are used to model human immunodeficiency virus type 1 (HIV-1) infections, but they are not natural hosts of HIV-1 or any simian immunodeficiency virus (SIV). Rather, they became infected with SIV through cross-species transfer from sooty mangabeys in captivity. It has been shown that HIV-1 utilizes rhesus CD4 less efficiently than human CD4. However, the relative ability of SIV envelope glycoproteins to bind or utilize these CD4 orthologs has not been reported. Here we show that several SIV isolates, including SIVmac239, are more efficiently neutralized by human CD4-Ig (huCD4-Ig) than by the same molecule bearing rhesus CD4 domains 1 and 2 (rhCD4-Ig). An I39N mutation in CD4 domain 1, present in human and sooty mangabey CD4 orthologs, largely restored rhCD4-Ig neutralization of SIVmac239 and other SIV isolates. We further observed that SIVmac316, a derivative of SIVmac239, bound to and was neutralized by huCD4-Ig and rhCD4-Ig with nearly identical efficiencies. Introduction of two SIVmac316 CD4-binding site residues (G382R and H442Y) into the SIVmac239 envelope glycoprotein (Env) markedly increased its neutralization sensitivity to rhesus CD4-Ig without altering neutralization by human CD4-Ig, SIV neutralizing antibodies, or sera from SIV-infected macaques. These changes also allowed SIVmac239 Env to bind rhCD4-Ig more efficiently than huCD4-Ig. The variant with G382R and H442Y (G382R/H442Y variant) also infected cells expressing rhesus CD4 with markedly greater efficiency than did unaltered SIVmac239 Env. We propose that infections of rhesus macaques with SIVmac239 G382R/H442Y might better model some aspects of human infections. IMPORTANCE Rhesus macaque infection with simian immunodeficiency virus (SIV) has served as an important model of human HIV-1 infection. However, differences between this model and the human case have complicated the development of vaccines and therapies. Here we report the surprising observation that SIVmac239, a commonly used model virus, more efficiently utilizes human CD4 than the CD4 of rhesus macaques, whereas the closely related virus SIVmac316 uses both CD4 orthologs equally well. We used this insight to generate a form of SIVmac239 envelope glycoprotein (Env) that utilized rhesus CD4 more efficiently, while retaining its resistance to antibodies and sera from infected macaques. This Env can be used to make the rhesus model more similar in some ways to human infection, for example by facilitating infection of cells with low levels of CD4. This property may be especially important to efforts to eradicate latently infected cells.


2003 ◽  
Vol 162 (3) ◽  
pp. 443-455 ◽  
Author(s):  
Annegret Pelchen-Matthews ◽  
Beatrice Kramer ◽  
Mark Marsh

Although human immunodeficiency virus type 1 (HIV-1) is generally thought to assemble at the plasma membrane of infected cells, virions have been observed in intracellular compartments in macrophages. Here, we investigated virus assembly in HIV-1–infected primary human monocyte-derived macrophages (MDM). Electron microscopy of cryosections showed virus particles, identified by their morphology and positive labeling with antibodies to the viral p17, p24, and envelope proteins, in intracellular vacuoles. Immunolabeling demonstrated that these compartments contained the late endosomal marker CD63, which was enriched on vesicles within these structures and incorporated into the envelope of budding virions. The virus-containing vacuoles were also labeled with antibodies against LAMP-1, CD81, and CD82, which were also incorporated into the viral envelope. To assess the cellular source of infectious viruses derived from MDM, virus-containing media from infected cells were precipitated with specific antibodies. Only antibodies against antigens found in late endosomes precipitated infectious virus, whereas antibodies against proteins located primarily on the cell surface did not. Our data indicate that most of the infectious HIV produced by primary macrophages is assembled on late endocytic membranes and acquires antigens characteristic of this compartment. This notion has significant implications for understanding the biology of HIV and its cell–cell transmission.


1996 ◽  
Vol 132 (5) ◽  
pp. 795-811 ◽  
Author(s):  
M M Sauter ◽  
A Pelchen-Matthews ◽  
R Bron ◽  
M Marsh ◽  
C C LaBranche ◽  
...  

A Tyr to Cys mutation at amino acid position 723 in the cytoplasmic domain of the simian immunodeficiency virus (SIV) transmembrane (TM) molecule has been shown to increase expression of envelope glycoproteins on the surface of infected cells. Here we show that Tyr-723 contributes to a sorting signal that directs the rapid endocytosis of viral glycoproteins from the plasma membrane via coated pits. On cells infected by SIVs with a Tyr at position 723, envelope glycoproteins were transiently expressed on the cell surface and then rapidly endocytosed. Similar findings were noted for envelope molecules expressed in the absence of other viral proteins. Immunoelectron microscopy demonstrated that these molecules were localized in patches on the cell surface and were frequently associated with coated pits. In contrast, envelope glycoproteins containing a Y723C mutation were diffusely distributed over the entire plasma membrane. To determine if an internalization signal was present in the SIV TM, chimeric molecules were constructed that contained the CD4 external and membrane spanning domains and a SIV TM cytoplasmic tail with a Tyr or other amino acids at SIV position 723. In Hela cells stably expressing these molecules, chimeras with a Tyr-723 were rapidly endocytosed, while chimeras containing other amino acids at position 723, including a Phe, were internalized at rates only slightly faster than a CD4 molecule that lacked a cytoplasmic domain. In addition, the biological effects of the internalization signal were evaluated in infectious viruses. A mutation that disrupted the signal and as a result, increased the level of viral envelope glycoprotein on infected cells, was associated with accelerated infection kinetics and increased cell fusion during viral replication. These results demonstrate that a Tyr-dependent motif in the SIV TM cytoplasmic domain can function as an internalization signal that can modulate expression of the viral envelope molecules on the cell surface and affect the biological properties of infectious viruses. The conservation of an analogous Tyr in all human and simian immunodeficiency viruses suggests that this signal may be present in other primate lentiviruses and could be important in the pathogenesis of these viruses in vivo.


1999 ◽  
Vol 73 (1) ◽  
pp. 855-860 ◽  
Author(s):  
Linqi Zhang ◽  
Peter J. Dailey ◽  
Tian He ◽  
Agegnehu Gettie ◽  
Sebastian Bonhoeffer ◽  
...  

ABSTRACT Perturbation of the equilibrium between human immunodeficiency virus type 1 (HIV-1) and the infected host by administering antiretroviral agents has revealed the rapid turnover of both viral particles and productively infected cells. In this study, we used the infusion of simian immunodeficiency virus (SIV) particles into rhesus macaques to obtain a more accurate estimate of viral clearance in vivo. Consistently, exogenously infused virions were cleared from plasma with an extremely short half-life, on the order of minutes (a mean of 3.3 min). This new estimate is ∼100-fold lower than the upper bound of 6 h previously reported for HIV-1 in infected humans. In select animals, multiple tissues were collected at the completion of each experiment to track the potential sites of virion clearance. Detectable levels of SIV RNA were found in lymph nodes, spleen, lungs, and liver, but not in other tissues examined. However, only ∼1 to 10% or less of the infused virions were accounted for by the thorough tissue sampling, indicating that the vast majority of the infused particles must have been degraded over a short period of time. Should the rapid clearance of virions described here be applicable to infected patients, then HIV-1 production and thus the number of productively infected CD4+ T lymphocytes or the viral burst size must be proportionally higher than previous minimal estimates.


2017 ◽  
Vol 91 (11) ◽  
Author(s):  
Jonathan Richard ◽  
Jérémie Prévost ◽  
Benjamin von Bredow ◽  
Shilei Ding ◽  
Nathalie Brassard ◽  
...  

ABSTRACT Antibodies recognizing conserved CD4-induced (CD4i) epitopes on human immunodeficiency virus type 1 (HIV-1) Env and able to mediate antibody-dependent cellular cytotoxicity (ADCC) have been shown to be present in sera from most HIV-1-infected individuals. These antibodies preferentially recognize Env in its CD4-bound conformation. CD4 downregulation by Nef and Vpu dramatically reduces exposure of CD4i HIV-1 Env epitopes and therefore reduce the susceptibility of HIV-1-infected cells to ADCC mediated by HIV-positive (HIV+) sera. Importantly, this mechanism of immune evasion can be circumvented with small-molecule CD4 mimetics (CD4mc) that are able to transition Env into the CD4-bound conformation and sensitize HIV-1-infected cells to ADCC mediated by HIV+ sera. However, HIV-1 developed additional mechanisms to avoid ADCC, including Vpu-mediated BST-2 antagonism, which decreases the overall amount of Env present at the cell surface. Accordingly, BST-2 upregulation in response to alpha interferon (IFN-α) was shown to increase the susceptibility of HIV-1-infected cells to ADCC despite the activity of Vpu. Here we show that BST-2 upregulation by IFN-β and interleukin-27 (IL-27) also increases the surface expression of Env and thus boosts the ability of CD4mc to sensitize HIV-1-infected cells to ADCC by sera from HIV-1-infected individuals. IMPORTANCE HIV-1 evolved sophisticated strategies to conceal Env epitopes from ADCC-mediating antibodies present in HIV+ sera. Vpu-mediated BST-2 downregulation was shown to decrease ADCC responses by limiting the amount of Env present at the cell surface. This effect of Vpu was shown to be attenuated by IFN-α treatment. Here we show that in addition to IFN-α, IFN-β and IL-27 also affect Vpu-mediated BST-2 downregulation and greatly enhance ADCC responses against HIV-1-infected cells in the presence of CD4mc. These findings may inform strategies aimed at HIV prevention and eradication.


2020 ◽  
Author(s):  
Shijian Zhang ◽  
Hanh T. Nguyen ◽  
Haitao Ding ◽  
Jia Wang ◽  
Shitao Zou ◽  
...  

The human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer is transported through the secretory pathway to the infected cell surface and onto virion particles. In the Golgi, the gp160 Env precursor is modified by complex sugars and proteolytically cleaved to produce the mature functional Env trimer, which resists antibody neutralization. We observed mostly uncleaved gp160 and smaller amounts of cleaved gp120 and gp41 Envs on the surface of HIV-1-infected or Env-expressing cells; however, cleaved Envs were relatively enriched in virions and virus-like particles (VLPs). This relative enrichment of cleaved Env in VLPs was observed for wild-type Envs, for Envs lacking the cytoplasmic tail and for CD4-independent, conformationally flexible Envs. On the cell surface, we identified three distinct populations of Envs: 1) the cleaved Env was transported through the Golgi, was modified by complex glycans, formed trimers that crosslinked efficiently, and was recognized by broadly neutralizing antibodies; 2) a small fraction of Env modified by complex carbohydrates escaped cleavage in the Golgi; and 3) the larger population of uncleaved Env lacked complex carbohydrates, crosslinked into diverse oligomeric forms, and was recognized by poorly neutralizing antibodies. This last group of more "open" Env oligomers reached the cell surface in the presence of Brefeldin A, apparently bypassing the Golgi apparatus. Relative to Envs transported through the Golgi, these uncleaved Envs were counterselected for virion incorporation. By employing two pathways for Env transport to the surface of infected cells, HIV-1 can misdirect host antibody responses towards conformationally flexible, uncleaved Env without compromising virus infectivity. IMPORTANCE The envelope glycoprotein (Env) trimers on the surface of human immunodeficiency virus (HIV-1) mediate the entry of the virus into host cells and serve as targets for neutralizing antibodies. The cleaved, functional Env is incorporated into virus particles from the surface of the infected cell. We found that an uncleaved form of Env is transported to the cell surface by an unconventional route, but this non-functional Env is mostly excluded from the virus. Thus, only one of the pathways by which Env is transported to the surface of infected cells results in efficient incorporation into virus particles, potentially allowing the uncleaved Env to act as a decoy to the host immune system without compromising virus infectivity.


1996 ◽  
Vol 183 (1) ◽  
pp. 215-225 ◽  
Author(s):  
A I Spira ◽  
P A Marx ◽  
B K Patterson ◽  
J Mahoney ◽  
R A Koup ◽  
...  

We used the simian immunodeficiency virus (SIV)/rhesus macaque model to study events that underlie sexual transmission of human immunodeficiency virus type 1 (HIV-1). Four female rhesus macaques were inoculated intravaginally with SIVmac251, and then killed 2, 5, 7, and 9 d later. A technique that detected polymerase chain reaction-amplified SIV in situ showed that the first cellular targets for SIV were in the lamina propria of the cervicovaginal mucosa, immediately subjacent to the epithelium. Phenotypic and localization studies demonstrated that many of the infected cells were likely to be dendritic cells. Within 2 d of inoculation, infected cells were identified in the paracortex and subcapsular sinus of the draining internal iliac lymph nodes. Subsequently, systemic dissemination of SIV was rapid, since culturable virus was detectable in the blood by day 5. From these results, we present a model for mucosal transmission of SIV and HIV-1.


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