Joseph Tang

DISCOVERY OF ANTIRHINOVIRAL LEADS BY SCREENING A COMBINATORIAL LIBRARY OF UREAS PREPARED USING COVALENT SCAVENGERS

Abstract Solution phase parallel synthesis of equimolar mixtures of ureas was accomplished using a solid-supported “covalent scavenger” (aminomethylpolystyrene) to remove isocyanate impurities. Screening of these purified mixtures for antirhinoviral activity in a whole cell assay and subsequent deconvolution of hit mixtures afforded novel antirhinoviral agents with low cytotoxicities.

Inhibition of duck hepatitis B virus replication by hypericin

Hypericin was found to be active against a member of the hepatitis B virus family, duck hepatitis B virus (DHBV). After a single 1 h incubation with hypericin, cells stably-transfected with a clone of DHBV stopped producing infectious virus for several days, though virus-like particles continued to be released into the culture medium. Characterization of these virions revealed a buoyant density characteristic of infectious virus preparations and lower than that of virus cores, suggesting that the particles were enveloped. Western blot analysis suggested, however, that the viral preS protein in surface antigen particles and, by inference, in virions, was present in covalently cross-linked aggregates. Evidence of a similar level of aggregation of the core subunit of virion nucleocapsids was not found, nor was there evidence of a similar high level of aggregation of cell-associated core and preS proteins. Hypericin was only slightly virucidal against DHBV and culture medium from treated cultures did not block initiation of infection when added to DHBV susceptible cultures prior to a challenge with infectious DHBV. Thus, the primary antiviral activity of hypericin against DHBV replication appears to be exerted at a late step in viral morphogenesis.

Small peptidic aldehyde inhibitors of human rhinovirus 3C protease

Abstract Small peptide aldehydes were designed to mimic the preferred substrate requirements for the human rhinovirus 3C protease. Di- and tripeptide aldehydes containing a methionine sulfone as a P 1 surrogate for glutamine show low micromolar enzyme inhibitory and antiviral tissue culture activity. LY338387, obtained in a short and efficient synthesis, appears to validate the protease as a therapeutic target.

Identification of functional subpopulations of murine natural killer cells based on their cell surface asialo GM1 phenotype

HSV-1 infection renders a mouse fibroblast cell line (MCN) sensitive to murine splenic NK killing which is independent of interferon (IFN) induction during the assay. This NK (HSV-1) activity is distinctive from conventional NK (YAC-1) in that they cannot be aborted by anti-asialo GM1 (anti-ASGM1) antibody plus complement treatment as NK (YAC-1) does. Further characterization of these two subpopulations was carried out by fluorescence-activated cell sorting (FACS) technique based on their cell surface asialo GM1 (ASGM1) phenotype. While almost all NK (YAC-1) activity resides within FACS-positive population, both ASGM1 positive and negative cell populations can kill the virally infected MCN equally well. One interesting observation is that only the ASGM1 positive cells respond significantly to IL-2 NK boosting. Five different mouse strains (CD-1, C57BL/6J, C57BL/6J-BG, SM/J, and SJL) were compared on their FACS profile with anti-ASGM1 antibody as well as their NK function. The differences observed are discussed.

Murine Thymocytes Mediate a Natural Killer‐Like Activity against Herpes Virus‐Infected Target Cells but Not YAC‐1 Target Cells

In this report, we demonstrated a natural killer (NK)‐like activity against HSV‐1 infected ceils mediated by CD‐1 mouse thymocytes. This cytolytic activity is specific for HSV‐1‐infected MCN cells, since both uninfected MCN and Y AC‐1 target cells are not susceptible to thymocyte lysis. Antibody plus complement depletion experiments indicate that a portion of the activity is associated with the Lyt 2 /L3T4− thymocyte subpopulation. This NK‐like activity cannot be enhanced by addition of interleukin 2 in vitro.

Antiviral activity, and biological properties of vinylacetylene analogs of enviroxime

A series of vinylacetylene analogs of Enviroxime (1) was synthesized. The new compounds are potent inhibitors of poliovirus in tissue culture. Cross-sensitivity with Enviroxime-derived mutants shows that the new compounds have the same mechanism of action as Enviroxime, which involves the viral 3A protein. In studies with Rhesus monkeys, the p-fluoro derivative 12 was found to be unique in providing oral bioavailability. Metabolism studies using hepatic microsomes suggest that this procedure would be a useful in vitro method for selecting the appropriate animal model for testing oral absorption. Compound 12 was found to be efficacious by oral administration in treating a Coxsackie A21 infection in CD-1 mice.