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Bray M, Di Mascio M, de Kok-Mercado F, Mollura DJ, Jagoda E. Radiolabeled antiviral drugs and antibodies as virus-specific imaging probes. Antiviral Res 2010; 88:129-142. [PMID: 20709111 PMCID: PMC7125728 DOI: 10.1016/j.antiviral.2010.08.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Accepted: 08/09/2010] [Indexed: 12/04/2022]
Abstract
A number of small-molecule drugs inhibit viral replication by binding directly to virion structural proteins or to the active site of a viral enzyme, or are chemically modified by a viral enzyme before inhibiting a downstream process. Similarly, antibodies used to prevent or treat viral infections attach to epitopes on virions or on viral proteins expressed on the surface of infected cells. Such drugs and antibodies can therefore be thought of as probes for the detection of viral infections, suggesting that they might be used as radiolabeled tracers to visualize sites of viral replication by single-photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging. A current example of this approach is the PET imaging of herpes simplex virus infections, in which the viral thymidine kinase phosphorylates radiolabeled thymidine analogues, trapping them within infected cells. One of many possible future applications might be the use of a radiolabeled hepatitis C protease inhibitor to image infection in animals or humans and provide a quantitative measure of viral burden. This article reviews the basic features of radionuclide imaging and the characteristics of ideal tracer molecules, and discusses how antiviral drugs and antibodies could be evaluated for their suitability as virus-specific imaging probes. The use of labeled drugs as low-dose tracers would provide an alternative application for compounds that have failed to advance to clinical use because of insufficient in vivo potency, an unsuitable pharmacokinetic profile or hepato- or nephrotoxicity.
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Affiliation(s)
- Mike Bray
- Integrated Research Facility, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, MD 21702, United States
| | - Michele Di Mascio
- Division of Clinical Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, United States
| | - Fabian de Kok-Mercado
- Integrated Research Facility, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, MD 21702, United States
| | - Daniel J Mollura
- Center for Infectious Disease Imaging, Department of Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD 20892, United States
| | - Elaine Jagoda
- Molecular Imaging Program, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States
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Das AT, Zhou X, Vink M, Klaver B, Berkhout B. Conditional live virus as a novel approach towards a safe live attenuated HIV vaccine. Expert Rev Vaccines 2002; 1:293-301. [PMID: 12901570 DOI: 10.1586/14760584.1.3.293] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To control the worldwide spread of HIV, a safe and effective prophylactic vaccine is urgently needed. Studies with the simian immunodeficiency virus demonstrated that a live attenuated virus can be effective as a vaccine, but serious concerns about the safety of such a vaccine virus have arisen. We propose a conditional live virus, of which the replication can be switched on and off at will, as a novel approach for an HIV vaccine.
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Affiliation(s)
- Atze T Das
- Department of Human Retrovirology, Academic Medical Center, University of Amsterdam, The Netherlands.
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Abstract
Development of a prophylactic human immunodeficiency virus type 1 (HIV-1) vaccine is a leading priority in biomedical research. Much of this work has been done with the nonhuman primate model of AIDS. In a historical context, vaccine studies, which use this model, are summarized and discussed.
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Affiliation(s)
- Stephen M Smith
- Saint Michael's Medical Center and The New Jersey Medical School - UMDNJ, Newark, NJ, USA.
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Smith SM, Khoroshev M, Marx PA, Orenstein J, Jeang KT. Constitutively dead, conditionally live HIV-1 genomes. Ex vivo implications for a live virus vaccine. J Biol Chem 2001; 276:32184-90. [PMID: 11397795 DOI: 10.1074/jbc.m101604200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An effective vaccine against AIDS is unlikely to be available for many years. As we approach two decades since the first identification of human immunodeficiency virus, type 1 (HIV-1), currently, only one subunit vaccine candidate has reached phase 3 of clinical trials. The subunit approach has been criticized for its inability to elicit effectively cytotoxic T-lymphocyte (CTL) response, which is felt by many to be needed for protection against HIV-1 infection. In subhuman primates, a live attenuated simian immunodeficiency virus (SIV) vaccine candidate, capable of inducing CTL, has been found to confer prophylactic immunity sufficient to prevent simian AIDS. Because replication competent (live) attenuated viruses could over time revert to virulence, such a live attenuated approach has largely been dismissed for HIV-1. Here, we describe the creation of constitutively dead conditionally live (CDCL) HIV-1 genomes. These genomes are constitutively defective for the Tat/TAR axis and are conditionally dependent on tetracycline for attenuated replication with robust expression of viral antigens. Our results suggest that CDCL genomes merit consideration as safer "live" attenuated HIV-1 vaccine candidates.
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Affiliation(s)
- S M Smith
- Saint Michael's Medical Center and the New Jersey Medical School-University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07102, USA
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Smith JM, Leung NJ, Torres JV. Preparation and induction of immune responses by a DNA AIDS vaccine. Viral Immunol 2001; 13:343-51. [PMID: 11016598 DOI: 10.1089/08828240050144662] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In an effort to evaluate the feasibility of developing a safe DNA vaccine for acquired immunodeficiency syndrome (AIDS), we have prepared a plasmid-based immunogen modeled after a naturally occurring noninfectious mutant of the simian immunodeficiency virus (SIV). The mutant SIV genome produces defective virus particles that are noninfectious in vitro and nonpathogenic in vivo in rhesus macaques. Analysis of the mutant genome revealed a 1.6 kb deletion that is in frame and spans integrase, vif, vpx, and most of vpr and results in a pol/vpr gene fusion. This deletion was introduced into the parental pathogenic molecular clone and the U3 region of the 5' LTR was replaced with a cytomegalovirus promoter to produce a candidate DNA vaccine, pIV. After transfection with this plasmid, SIV gag and envelope proteins are expressed and properly processed in vitro. When injected into rabbits, pIV elicited an antibody response to SIV gp130 envelope glycoprotein with titers reaching 1:2048, and a strong lymphoproliferative response to SIV gp130 and whole SIV. The potential to produce defective virus particles in vivo without integrating into the host genome should result in both a strong humoral and cellular immune response in rhesus macaques. In addition, this approach offers a safe alternative to live attenuated vaccines and DNA vaccines that are capable of integration.
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Affiliation(s)
- J M Smith
- Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis 95616, USA
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Tanuri A, Jesus da Costa L, Brindeiro R, Ramos CA, Pau CP, Rayfield MA. Construction of a selectable nef-defective live-attenuated human immunodeficiency virus expressing Escherichia coli gpt gene. Virology 2000; 268:79-86. [PMID: 10683329 DOI: 10.1006/viro.1999.0145] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have developed a replication-competent human immunodeficiency virus (HIV) carrying a selective marker that can be used in vivo. This recombinant virus (Z6 Delta nef gpt) was generated by replacing the 5' half of the HIV nef gene with the Escherichia coli guanine phosphoribosyl transferase gene (gpt). This new vector can express the gpt product on infection and works as a positive selective marker for mycophenolic acid (MPA) resistance, a potent immunosuppressive drug used in organ rejection therapy. Conversely, gpt expression also served as a negative selectable marker, since its intracellular expression induces host-cell susceptibility to 6-thioxantine (6-TX), a nucleotide analog that is toxic to the infected cell under these conditions. In this manner, we could suppress the recombinant virus replication through 6-TX selection in both transformed cells and primary human peripheral blood mononuclear cells (PBMCs), suggesting the vector's potential as a model for a new live-attenuated vaccine approach against HIV.
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Affiliation(s)
- A Tanuri
- Division of AIDS, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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Cheng H, Hoxie JP, Parks WP. The conserved core of human immunodeficiency virus type 1 Nef is essential for association with Lck and for enhanced viral replication in T-lymphocytes. Virology 1999; 264:5-15. [PMID: 10544125 DOI: 10.1006/viro.1999.9937] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Nef protein of the primate lentiviruses, including human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV), is a myristylated protein associated with increased viral replication and enhanced pathogenicity. Both the potentiation of T-lymphocyte activation and the enhanced serine-phosphorylation of HIV-1 capsid by Nef correlate with increased viral replication. We report the functional interactions of the Nef proteins with Src kinases. The Nef proteins from HIV-1 and SIV bind to Lck as well as Hck, Lyn, and Fyn. The SH3 and SH2 domains of Lck are sufficient for coprecipitation with non-tyrosine-phosphorylated Nef proteins. The conserved core region of HIV-1 Nef is essential for the interaction with Lck and is also important for enhanced HIV-1 replication in T-lymphocytes. In addition, we show that SIV and HIV-1 Nef proteins are differentially tyrosine-phosphorylated. The kinase-active Lck tyrosine-phosphorylates SIVmac239 Nef but does not phosphorylate HIV-1 Nef. These data suggest that the association of Nef and Lck is central to the enhanced viral replication of HIV-1 and SIV in T-lymphocytes.
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Affiliation(s)
- H Cheng
- Department of Microbiology and Pediatrics, New York University School of Medicine, New York, New York 10016, USA
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Abstract
Live attenuated viruses can provide vaccine protection against various viral illnesses. A number of live attenuated strains of the simian immunodeficiency virus (SIV) or related lentiviruses have been evaluated in primate models as vaccine candidates against AIDS. Impressive efficacy was observed for some viruses, most notably SIV strains with deletions in the nef-gene. Sterilizing immunity was seen against homologous and heterologous virus challenge, against cell-free and cell-associated challenge, against intravenous and mucosal challenge, and against challenge as early as 3 weeks and as late as 2.25 years after just one immunization. However, these promising efficacy results are overshadowed by safety problems, such as reversion of the vaccine strain to a pathogenic virus encoding full-length nef or residual virulence of multiply deleted vaccine strains. Strategies aimed at decreasing the replicative capacity of nef-deleted vaccine strains to increase the safety profile have significantly curtailed vaccine efficacy. Nevertheless, studies of live attenuated vaccine strains should proceed and should focus on determining the correlates of vaccine protection and the molecular determinants for virulence and attenuation.
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Affiliation(s)
- R M Ruprecht
- Dana-Farber Cancer Institute, Boston MA 02115-6084, USA.
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Affiliation(s)
- J S Oxford
- Academic Virology, Royal London School of Medicine and Dentistry, UK
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Maitra RK, Silverman RH. Regulation of human immunodeficiency virus replication by 2',5'-oligoadenylate-dependent RNase L. J Virol 1998; 72:1146-52. [PMID: 9445011 PMCID: PMC124589 DOI: 10.1128/jvi.72.2.1146-1152.1998] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Activation of RNase L by 2',5'-linked oligoadenylates (2-5A) is one of the antiviral pathways of interferon action. To determine the involvement of the 2-5A system in the control of human immunodeficiency virus type 1 (HIV-1) replication, a segment of the HIV-1 nef gene was replaced with human RNase L cDNA. HIV-1 provirus containing sense orientation RNase L cDNA caused increased expression of RNase L and 500- to 1,000-fold inhibition of virus replication in Jurkat cells for a period of about 2 weeks. Subsequently, a partial deletion of the RNase L cDNA which coincided with increases in virus production occurred. The anti-HIV activity of RNase L correlated with decreases in HIV-1 RNA and with an acceleration in cell death accompanied by DNA fragmentation. Replication of HIV-1 encoding RNase L was also transiently suppressed in peripheral blood lymphocytes (PBL). In contrast, recombinant HIV containing reverse orientation RNase L cDNA caused decreased levels of RNase L, increases in HIV yields, and reductions in the anti-HIV effect of alpha interferon in PBL and in Jurkat cells. To obtain constitutive and continuous expression of RNase L cDNA, Jurkat cells were cotransfected with HIV-1 proviral DNA and with plasmid containing a cytomegalovirus promoter driving expression of RNase L cDNA. The RNase L plasmid suppressed HIV-1 replication by eightfold, while an antisense RNase L construct enhanced virus production by twofold. These findings demonstrate that RNase L can severely impair HIV replication and suggest involvement of the 2-5A system in the anti-HIV effect of alpha interferon.
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Affiliation(s)
- R K Maitra
- Virus Core Facility, The Lerner Research Institute, The Cleveland Clinic Foundation, Ohio 44195, USA
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Salkowitz J, Chakrabarti B, Yen-Lieberman B, Starkey C, Bendele T, Kestler H. The nef Gene of SIVmac239 Is Necessary for Efficient Growth in H9 Cells. J Biomed Sci 1996; 3:422-434. [PMID: 11725123 DOI: 10.1007/bf02258046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
AIDS viruses require an intact functional nef gene in order to induce disease. The nonpathogenic molecular cloned virus SIVmac239nef-deletion encodes a truncated nef gene. This attenuated reading frame is expressed both in vitro and in a virus-infected animal in vivo. Encoding the first 58 amino acids of Nef, the reading frame retained its ability to down-modulate CD4 from the surface of T cells. CD4-down-modulated stable cell lines expressing full-length and truncated nef genes were significantly less infected by SIV. SIVmac239nef-open and SIVmacnef-deletion encoding a truncated nef clearly differed in replication kinetics in H9 cells and H9-derived cell lines. SIVmac239nef-deletion replication was delayed in H9. Copyright 1996 S. Karger AG, Basel
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Affiliation(s)
- J.R. Salkowitz
- Department of Molecular Biology, Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
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