Jonathan Silver, M.D.

Chief, Biophysical Virology Section

Dr. Silver received his undergraduate and medical degrees from Harvard University and a master's degree in physics from Stanford University. After postdoctoral fellowships at Harvard and the Imperial Cancer Research Fund in London, he came to NIH in 1980, where he worked with Dr. Wallace Rowe before transferring to the Laboratory of Molecular Microbiology in 1985.

Description of Research Program

The Biophysical Virology Section uses standard molecular biological methods and biophysical techniques to study retroviruses. We developed methods to detect integrated retroviral DNA (inverse PCR), reverse transcriptase activity (via PCR of reverse transcribed cDNA), and methods for performing PCR on arrays of microdroplets.

The section has a long-term interest in interactions involving viral envelope. We studied envelope effects on retroviral pathogenesis, resistance to retroviruses due to inherited envelope genes in mice, cell-to-cell transmission of RNA via vesicles bearing envelope or receptor genes, and lipid requirements for envelope-mediated fusion. We are currently focusing on the mechanism of envelope-mediated membrane fusion, using murine leukemia virus and HIV as model systems. We are particularly interested in developing better methods to study membrane fusion processes.

Recent Data

We recently developed a fusion assay using cells engineered to express viral envelope plus a tetracycline transcriptional transactivator (tTA), and cells expressing virus receptor plus an indicator gene (gfp or luciferase) under the control of a tTA-responsive promoter. The assay provides a sensitive and quantitative measure of cell fusion mediated by murine leukemia viruses, HIV, vesicular stomatitis virus, and, potentially, many other viruses. We are using this assay to study the effect of mutations in envelope and receptor genes, the ability of peptides from MLV and HIV proteins to inhibit fusion or complement envelope mutations, and the effect of polyanions and lipid composition on fusion. Our goal is to understand the mechanism of protein-mediated bilayer fusion and find ways to inhibit this process in the case of pathogenic viruses.

Figure 1. The N-terminus of the receptor for ecotropic murine leukemia virus (MLV) encodes a mitochondrial targeting signal. BHK cells transfected with (A) gfp, which localizes to cytosol, (B) the amino-terminal 36 amino acids of the MLV receptor fused to gfp, which redirects gfp to mitochondria, (C) same as B plus a mitochondrially targeted form of dsRed, showing co-localization, (D) same as B stained with a red mitochondrial dye, (E) same as B stained with an antibody to mitochondrial cytochrome oxidase, labeled in red.

Research Group Members

Wu Ou, M.D., Research Fellow, 301-496-3653, wou@niaid.nih.gov.

Selected Publications

(View list in PubMed.)

Ou W, Xiong Y, Silver J. Quantification of virus envelope-mediated cell fusion using a tetracycline transcriptional transactivator: fusion does not correlate with syncytium formation. Virology. 2004. 324: 263-272.

Ahn K-S, Ou W, Silver J. Inhibition of certain strains of HIV-1 by cell surface polyanions in the form of cholesterol-labeled oligonucleotides. Virology. 2004. 330: 50-61.

Ou W, Silver J. Inhibition of MLV envelope protein (env) processing by intracellular expression of the env N-terminal heptad repeat region. J Virol. 2005. 79: 4782-4792.

Silver J, Ou W. Photo-activation of quantum dot fluorescence following endocytosis. Nano Letters. 2005. 5: 1445-1449.

Ou W, Silver J. Efficient trapping of HIV-1 envelope protein by hetero-oligomerization with an N-helix chimera. Retrovirology. 2005. 2: 51.

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