In Vitro Resistance to the Human Immunodeficiency Virus Type 1 Maturation Inhibitor PA-457 (Bevirimat)

ABSTRACT 3-O-(3′,3′-dimethylsuccinyl)betulinic acid (PA-457 or bevirimat) potently inhibits human immunodeficiency virus type 1 (HIV-1) maturation by blocking a late step in the Gag processing pathway, specifically the cleavage of SP1 from the C terminus of capsid (CA). To gain insights into the mechanism(s) by which HIV-1 could evolve resistance to PA-457 and to evaluate the likelihood of such resistance arising in PA-457-treated patients, we sought to identify and characterize a broad spectrum of HIV-1 variants capable of conferring resistance to this compound. Numerous independent rounds of selection repeatedly identified six single-amino-acid substitutions that independently confer PA-457 resistance: three at or near the C terminus of CA (CA-H226Y, -L231F, and -L231M) and three at the first and third residues of SP1 (SP1-A1V, -A3T, and -A3V). We determined that mutations CA-H226Y, CA-L231F, CA-L231M, and SP1-A1V do not impose a significant replication defect on HIV-1 in culture. In contrast, mutations SP1-A3V and -A3T severely impaired virus replication and inhibited virion core condensation. The replication defect imposed by SP1-A3V was reversed by a second-site compensatory mutation in CA (CA-G225S). Intriguingly, high concentrations of PA-457 enhanced the maturation of SP1 residue 3 mutants. The different phenotypes associated with mutations that confer PA-457 resistance suggest the existence of multiple mechanisms by which HIV-1 can evolve resistance to this maturation inhibitor. These findings have implications for the ongoing development of PA-457 to treat HIV-1 infection in vivo.

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Mutation of Dileucine-Like Motifs in the Human Immunodeficiency Virus Type 1 Capsid Disrupts Virus Assembly, Gag-Gag Interactions, Gag-Membrane Binding, and Virion Maturation

Journal of Virology ◽

10.1128/jvi.00355-06 ◽

2006 ◽

Vol 80 (16) ◽

pp. 7939-7951 ◽

Cited By ~ 47

Author(s):

Anjali Joshi ◽

Kunio Nagashima ◽

Eric O. Freed

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Particle Production ◽

Virus Assembly ◽

Membrane Binding ◽

Single Amino Acid ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Gag precursor protein Pr55Gag drives the assembly and release of virus-like particles in the infected cell. The capsid (CA) domain of Gag plays an important role in these processes by promoting Gag-Gag interactions during assembly. The C-terminal domain (CTD) of CA contains two dileucine-like motifs (L189/L190 and I201/L202) implicated in regulating the localization of Gag to multivesicular bodies (MVBs). These dileucine-like motifs are located in the vicinity of the CTD dimer interface, a region of CA critical for Gag-Gag interactions during virus assembly and CA-CA interactions during core formation. To study the importance of the CA dileucine-like motifs in various aspects of HIV-1 replication, we introduced a series of mutations into these motifs in the context of a full-length, infectious HIV-1 molecular clone. CA mutants LL189,190AA and IL201,202AA were both severely impaired in virus particle production because of a variety of defects in the binding of Gag to membrane, Gag multimerization, and CA folding. In contrast to the model suggesting that the CA dileucine-like motifs regulate MVB targeting, the IL201,202AA mutation did not alter Gag localization to the MVB in either HeLa cells or macrophages. Revertants of single-amino-acid substitution mutants were obtained that no longer contained dileucine-like motifs but were nevertheless fully replication competent. The varied phenotypes of the mutants reported here provide novel insights into the interplay among Gag multimerization, membrane binding, virus assembly, CA dimerization, particle maturation, and virion infectivity.

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Determinants of Syncytium Formation in Microglia by Human Immunodeficiency Virus Type 1: Role of the V1/V2 Domains

Journal of Virology ◽

10.1128/jvi.74.2.693-701.2000 ◽

2000 ◽

Vol 74 (2) ◽

pp. 693-701 ◽

Cited By ~ 35

Author(s):

Joseph T. C. Shieh ◽

Julio Martín ◽

Gordon Baltuch ◽

Michael H. Malim ◽

Francisco González-Scarano

Keyword(s):

Human Immunodeficiency Virus ◽

Amino Acid ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Syncytium Formation ◽

Single Amino Acid ◽

Single Amino Acid Change ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT Microglia are the main reservoir for human immunodeficiency virus type 1 (HIV-1) in the central nervous system (CNS), and multinucleated giant cells, the result of fusion of HIV-1-infected microglia and brain macrophages, are the neuropathologic hallmark of HIV dementia. One potential explanation for the formation of syncytia is viral adaptation for these CD4+ CNS cells. HIV-1BORI-15, a virus adapted to growth in microglia by sequential passage in vitro, mediates high levels of fusion and replicates more efficiently in microglia and monocyte-derived-macrophages than its unpassaged parent (J. M. Strizki, A. V. Albright, H. Sheng, M. O'Connor, L. Perrin, and F. Gonzalez-Scarano, J. Virol. 70:7654–7662, 1996). Since the interaction between the viral envelope glycoprotein and CD4 and the chemokine receptor mediates fusion and plays a key role in tropism, we have analyzed the HIV-1BORI-15 env as a fusogen and in recombinant and pseudotyped viruses. Its syncytium-forming phenotype is not the result of a switch in coreceptor use but rather of the HIV-1BORI-15envelope-mediated fusion of CD4+CCR5+ cells with greater efficiency than that of its parental strain, either by itself or in the context of a recombinant virus. Genetic analysis indicated that the syncytium-forming phenotype was due to four discrete amino acid differences in V1/V2, with a single-amino-acid change between the parent and the adapted virus (E153G) responsible for the majority of the effect. Additionally, HIV-1BORI-15 env-pseudotyped viruses were less sensitive to decreases in the levels of CD4 on transfected 293T cells, leading to the hypothesis that the differences in V1/V2 alter the interaction between this envelope and CD4 or CCR5, or both. In sum, the characterization of the envelope of HIV-1BORI-15, a highly fusogenic glycoprotein with genetic determinants in V1/V2, may lead to a better understanding of the relationship between HIV replication and syncytium formation in the CNS and of the importance of this region of gp120 in the interaction with CD4 and CCR5.

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The Conserved Carboxy Terminus of the Capsid Domain of Human Immunodeficiency Virus Type 1 Gag Protein Is Important for Virion Assembly and Release

Journal of Virology ◽

10.1128/jvi.78.18.9675-9688.2004 ◽

2004 ◽

Vol 78 (18) ◽

pp. 9675-9688 ◽

Cited By ~ 47

Author(s):

Daniel Melamed ◽

Michal Mark-Danieli ◽

Michal Kenan-Eichler ◽

Osnat Kraus ◽

Asher Castiel ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Hinge Region ◽

Virion Assembly ◽

C Terminus ◽

Immunodeficiency Virus ◽

Hiv 1 ◽

Ca Protein

ABSTRACT The retroviral Gag precursor plays an important role in the assembly of virion particles. The capsid (CA) protein of the Gag molecule makes a major contribution to this process. In the crystal structure of the free CA protein of the human immunodeficiency virus type 1 (HIV-1), 11 residues of the C terminus were found to be unstructured, and to date no information exists on the structure of these residues in the context of the Gag precursor molecule. We performed phylogenetic analysis and demonstrated a high degree of conservation of these 11 amino acids. Deletion of this cluster or introduction of various point mutations into these residues resulted in significant impairment of particle infectivity. In this cluster, two putative structural regions were identified, residues that form a hinge region (353-VGGP-356) and those that contribute to an α-helix (357-GHKARVL-363). Overall, mutations in these regions resulted in inhibition of virion production, but mutations in the hinge region demonstrated the most significant reduction. Although all the Gag mutants appeared to have normal Gag-Gag and Gag-RNA interactions, the hinge mutants were characterized by abnormal formation of cytoplasmic Gag complexes. Gag proteins with mutations in the hinge region demonstrated normal membrane association but aberrant rod-like membrane structures. More detailed analysis of these structures in one of the mutants demonstrated abnormal trapped Gag assemblies. These data suggest that the conserved CA C terminus is important for HIV-1 virion assembly and release and define a putative target for drug design geared to inhibit the HIV-1 assembly process.

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Chimeric Human Immunodeficiency Virus Type 1 (HIV-1) Virions Containing HIV-2 or Simian Immunodeficiency Virus Nef Are Resistant to Cyclosporine Treatment

Journal of Virology ◽

10.1128/jvi.78.4.1843-1850.2004 ◽

2004 ◽

Vol 78 (4) ◽

pp. 1843-1850 ◽

Cited By ~ 3

Author(s):

Mahfuz Khan ◽

Lingling Jin ◽

Ming Bo Huang ◽

Lesa Miles ◽

Vincent C. Bond ◽

...

Keyword(s):

Amino Acids ◽

Human Immunodeficiency Virus ◽

Simian Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Cyclophilin A ◽

C Terminus ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT The viral protein Nef and the cellular factor cyclophilin A are both required for full infectivity of human immunodeficiency virus type 1 (HIV-1) virions. In contrast, HIV-2 and simian immunodeficiency virus (SIV) do not incorporate cyclophilin A into virions or need it for full infectivity. Since Nef and cyclophilin A appear to act in similar ways on postentry events, we determined whether chimeric HIV-1 virions that contained either HIV-2 or SIV Nef would have a direct effect on cyclophilin A dependence. Our results show that chimeric HIV-1 virions containing either HIV-2 or SIV Nef are resistant to treatment by cyclosporine and enhance the infectivity of virions with mutations in the cyclophilin A binding loop of Gag. Amino acids at the C terminus of HIV-2 and SIV are necessary for inducing cyclosporine resistance. However, transferring these amino acids to the C terminus of HIV-1 Nef is insufficient to induce cyclosporine resistance in HIV-1. These results suggest that HIV-2 and SIV Nef are able to compensate for the need for cyclophilin A for full infectivity and that amino acids present at the C termini of these proteins are important for this function.

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Particle Size Determinants in the Human Immunodeficiency Virus Type 1 Gag Protein

Journal of Virology ◽

10.1128/jvi.72.6.4667-4677.1998 ◽

1998 ◽

Vol 72 (6) ◽

pp. 4667-4677 ◽

Cited By ~ 38

Author(s):

Laurence Garnier ◽

Lee Ratner ◽

Benjamin Rovinski ◽

Shi-Xian Cao ◽

John W. Wills

Keyword(s):

Human Immunodeficiency Virus ◽

Particle Size ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Gag Protein ◽

Important Region ◽

C Terminus ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT The retroviral Gag protein plays the central role in the assembly process and can form membrane-enclosed, virus-like particles in the absence of any other viral products. These particles are similar to authentic virions in density and size. Three small domains of the human immunodeficiency virus type 1 (HIV-1) Gag protein have been previously identified as being important for budding. Regions that lie outside these domains can be deleted without any effect on particle release or density. However, the regions of Gag that control the size of HIV-1 particles are less well understood. In the case of Rous sarcoma virus (RSV), the size determinant maps to the CA (capsid) and adjacent spacer sequences within Gag, but systematic mapping of the HIV Gag protein has not been reported. To locate the size determinants of HIV-1, we analyzed a large collection of Gag mutants. To our surprise, all mutants with defects in the MA (matrix), CA, and the N-terminal part of NC (nucleocapsid) sequences produced dense particles of normal size, suggesting that oncoviruses (RSV) and lentiviruses (HIV-1) have different size-controlling elements. The most important region found to be critical for determining HIV-1 particle size is the p6 sequence. Particles lacking all or small parts of p6 were uniform in size distribution but very large as measured by rate zonal gradients. Further evidence for this novel function of p6 was obtained by placing this sequence at the C terminus of RSV CA mutants that produce heterogeneously sized particles. We found that the RSV-p6 chimeras produced normally sized particles. Thus, we present evidence that the entire p6 sequence plays a role in determining the size of a retroviral particle.

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A Phase IIa Study Evaluating Safety, Pharmacokinetics, and Antiviral Activity of GSK2838232, a Novel, Second-generation Maturation Inhibitor, in Participants With Human Immunodeficiency Virus Type 1 Infection

Clinical Infectious Diseases ◽

10.1093/cid/ciz938 ◽

2019 ◽

Vol 71 (5) ◽

pp. 1255-1262 ◽

Cited By ~ 3

Author(s):

Edwin DeJesus ◽

Sara Harward ◽

Roxanne C Jewell ◽

Mark Johnson ◽

Etienne Dumont ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Second Generation ◽

Proof Of Concept ◽

Once Daily ◽

Immunodeficiency Virus ◽

Maturation Inhibitor ◽

Hiv 1

Abstract Background GSK2838232 is a second-generation, potent, small-molecule, oral human immunodeficiency virus type 1 (HIV-1) maturation inhibitor for once-daily administration boosted with a pharmacoenhancer. Methods The phase 2a, proof-of-concept study was an open-label, adaptive dose-ranging design. Safety, pharmacokinetics, and efficacy of GSK2838232 boosted by cobicistat were evaluated in individuals with HIV-1 infection. The study participants (N = 33) received GSK2838232 once daily across a range of doses (20–200 mg) with cobicistat 150 mg for 10 days. Results GSK2838232 was safe and well tolerated with no clinically meaningful changes in safety parameters or adverse events. Exposure (maximum concentration and area under the concentration-time curve from time zero to the concentration at 24 hours postdose) increased 2- to 3-fold with repeated dosing in an approximately dose-proportional manner, reaching steady-state by day 8 with a half-life (t½) from 16.3 to 19.2 hours. Clearance and t½ values were not dependent on dose. Viral load declined from baseline with all GSK2838232 doses. Mean maximum declines from baseline to day 11 in HIV-1 RNA log10 copies/mL with the 20-mg, 50-mg, 100-mg, and 200-mg cohorts were −0.67, −1.56, −1.32, and −1.70, respectively. CD4+ cell counts increased at doses ≥50 mg. Conclusions GSK2838232 with cobicistat was well tolerated and exhibited efficacy as a short-term monotherapy in participants with HIV-1. This positive proof-of-concept study supports the continued development of GSK2838232 for the treatment of HIV as part of combination antiretroviral therapy. Clinical Trials Registration NCT03045861.

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New Small-Molecule Inhibitor Class Targeting Human Immunodeficiency Virus Type 1 Virion Maturation

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00759-09 ◽

2009 ◽

Vol 53 (12) ◽

pp. 5080-5087 ◽

Cited By ~ 36

Author(s):

Wade S. Blair ◽

Joan Cao ◽

Juin Fok-Seang ◽

Paul Griffin ◽

Jason Isaacson ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Small Molecule ◽

Betulinic Acid ◽

Molecule Inhibitor ◽

Immunodeficiency Virus ◽

Maturation Inhibitor ◽

Hiv 1

ABSTRACTA new small-molecule inhibitor class that targets virion maturation was identified from a human immunodeficiency virus type 1 (HIV-1) antiviral screen. PF-46396, a representative molecule, exhibits antiviral activity against HIV-1 laboratory strains and clinical isolates in T-cell lines and peripheral blood mononuclear cells (PBMCs). PF-46396 specifically inhibits the processing of capsid (CA)/spacer peptide 1 (SP1) (p25), resulting in the accumulation of CA/SP1 (p25) precursor proteins and blocked maturation of the viral core particle. Viral variants resistant to PF-46396 contain a single amino acid substitution in HIV-1 CA sequences (CAI201V), distal to the CA/SP1 cleavage site in the primary structure, which we demonstrate is sufficient to confer significant resistance to PF-46396 and 3-O-(3′,3′-dimethylsuccinyl) betulinic acid (DSB), a previously described maturation inhibitor. Conversely, a single amino substitution in SP1 (SP1A1V), which was previously associated with DSB in vitro resistance, was sufficient to confer resistance to DSB and PF-46396. Further, the CAI201V substitution restored CA/SP1 processing in HIV-1-infected cells treated with PF-46396 or DSB. Our results demonstrate that PF-46396 acts through a mechanism that is similar to DSB to inhibit the maturation of HIV-1 virions. To our knowledge, PF-46396 represents the first small-molecule HIV-1 maturation inhibitor that is distinct in chemical class from betulinic acid-derived maturation inhibitors (e.g., DSB), demonstrating that molecules of diverse chemical classes can inhibit this mechanism.

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Blockade of Human Immunodeficiency Virus Type 1 Expression by Caveolin-1

Journal of Virology ◽

10.1128/jvi.76.18.9152-9164.2002 ◽

2002 ◽

Vol 76 (18) ◽

pp. 9152-9164 ◽

Cited By ~ 19

Author(s):

Manuel Llano ◽

Tara Kelly ◽

Maria Vanegas ◽

Mary Peretz ◽

Timothy E. Peterson ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Amino Acid ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Single Amino Acid ◽

Hydrophobic Membrane ◽

Caveolin 1 ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT Caveolin-1 (Cav-1) is a major protein constituent of caveolae, a type of plasma membrane raft. We observed that coexpression of human Cav-1 with human immunodeficiency virus type 1 (HIV-1) blocked virion production from cells that are ordinarily highly permissive. Further investigation showed that this effect is specific, occurs at low ratios of Cav-1 to HIV-1 DNA, depends on expression of Cav-1 protein, and involves severely impaired expression of HIV-1 proteins. Cav-1 also blocked HIV-2 expression. In contrast, Cav-1 did not inhibit protein expression by a paramyxovirus and did not induce apoptosis or affect cellular morphology, cell viability, or cell cycle progression. Although only small amounts of HIV-1 virions were released from Cav-1-transfected cells, these were fully infectious. Deletion mutagenesis showed that the C-terminal 78 residues were as active as the full-length (178-amino-acid) protein in producing the block. In contrast, the 100 most N-terminal amino acids of Cav-1, which include the previously identified oligomerization and scaffolding domains, were shown to be dispensable. Study of single-amino-acid-exchange mutants of Cav-1 established that palmitoylation was not required. Additional deletion mutants then identified the hydrophobic, membrane-associated domain (residues 101 to 135) as the main determinant. Cellular distribution of wild-type and mutant proteins correlated with ability to block HIV-1 expression. Finally, Cav-2 also blocked HIV-1 expression. These data show that coexpression of caveolins can markedly inhibit expression of HIV proviral DNA and establish that the inhibition is mediated by the hydrophobic, membrane-associated domain.

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Genetic Evidence for an Interaction between Human Immunodeficiency Virus Type 1 Matrix and α-Helix 2 of the gp41 Cytoplasmic Tail

Journal of Virology ◽

10.1128/jvi.74.8.3548-3554.2000 ◽

2000 ◽

Vol 74 (8) ◽

pp. 3548-3554 ◽

Cited By ~ 164

Author(s):

Tsutomu Murakami ◽

Eric O. Freed

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Cytoplasmic Tail ◽

Genetic Evidence ◽

Single Amino Acid ◽

Immunodeficiency Virus ◽

Α Helix ◽

Hiv 1

ABSTRACT The incorporation of envelope (Env) glycoproteins into virions is an essential step in the retroviral replication cycle. Lentiviruses, including human immunodeficiency virus type 1 (HIV-1), encode Env glycoproteins with unusually long cytoplasmic tails, the functions of which have not been fully elucidated. In this study, we examine the effects on virus replication of a number of mutations in a helical motif (α-helix 2) located near the center of the HIV-1 gp41 cytoplasmic tail. We find that, in T-cell lines, small deletions in this domain disrupt the incorporation of Env glycoproteins into virions and markedly impair virus infectivity. Through the analysis of viral revertants, we demonstrate that a single amino acid change (34VI) in the matrix domain of Gag reverses the Env incorporation and infectivity defect imposed by a small deletion near the C terminus of α-helix 2. These results provide genetic evidence, in the context of infected T cells, for an interaction between HIV-1 matrix and the gp41 cytoplasmic tail and identify domains of both proteins involved in this putative interaction.

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Hypersusceptibility to Substrate Analogs Conferred by Mutations in Human Immunodeficiency Virus Type 1 Reverse Transcriptase

Journal of Virology ◽

10.1128/jvi.00322-06 ◽

2006 ◽

Vol 80 (14) ◽

pp. 7169-7178 ◽

Cited By ~ 14

Author(s):

Robert A. Smith ◽

Donovan J. Anderson ◽

Bradley D. Preston

Keyword(s):

Human Immunodeficiency Virus ◽

Amino Acid ◽

Reverse Transcriptase ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Single Amino Acid ◽

Substrate Analog ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) contains four structural motifs (A, B, C, and D) that are conserved in polymerases from diverse organisms. Motif B interacts with the incoming nucleotide, the template strand, and key active-site residues from other motifs, suggesting that motif B is an important determinant of substrate specificity. To examine the functional role of this region, we performed “random scanning mutagenesis” of 11 motif B residues and screened replication-competent mutants for altered substrate analog sensitivity in culture. Single amino acid replacements throughout the targeted region conferred resistance to lamivudine and/or hypersusceptibility to zidovudine (AZT). Substitutions at residue Q151 increased the sensitivity of HIV-1 to multiple nucleoside analogs, and a subset of these Q151 variants was also hypersusceptible to the pyrophosphate analog phosphonoformic acid (PFA). Other AZT-hypersusceptible mutants were resistant to PFA and are therefore phenotypically similar to PFA-resistant variants selected in vitro and in infected patients. Collectively, these data show that specific amino acid replacements in motif B confer broad-spectrum hypersusceptibility to substrate analog inhibitors. Our results suggest that motif B influences RT-deoxynucleoside triphosphate interactions at multiple steps in the catalytic cycle of polymerization.

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