Differential alteration of the anti-HIV-1 effect of phosphorothioate oligonucleotide S-dC28 by AZT, interferon-alpha, and dextran sulfate

Antisense Nucleic Acids — Prospects for Antiviral Intervention

Antisense oligodeoxynucleotides are a promising new class of antiviral agent. Because they bind in a sequence-specific manner to complementary regions of mRNA, oligos can inhibit gene expression in a sequence-specific manner. The ‘antisense’ approach has been used successfully to block cellular expression and replication of several viruses including Human Immunodeficiency Virus-1 (HIV-1), and Herpes Simplex Virus (HSV). However, the antiviral effect of oligodeoxynucleotides is not limited to sequence-specific inhibition of gene expression. Non sequence-specific effects are frequently observed, presumably as a result of their properties as polyanions. Occasionally (e.g. for HIV-1) these non sequence-specific effects are also therapeutic. The prospects for antisense oligodeoxynucleotide therapy for viral disease are discussed.

Theoretical basis, experimental design, and computerized simulation of synergism and antagonism in drug combination studies

The median-effect equation derived from the mass-action law principle at equilibrium-steady state via mathematical induction and deduction for different reaction sequences and mechanisms and different types of inhibition has been shown to be the unified theory for the Michaelis-Menten equation, Hill equation, Henderson-Hasselbalch equation, and Scatchard equation. It is shown that dose and effect are interchangeable via defined parameters. This general equation for the single drug effect has been extended to the multiple drug effect equation for n drugs. These equations provide the theoretical basis for the combination index (CI)-isobologram equation that allows quantitative determination of drug interactions, where CI < 1, = 1, and > 1 indicate synergism, additive effect, and antagonism, respectively. Based on these algorithms, computer software has been developed to allow automated simulation of synergism and antagonism at all dose or effect levels. It displays the dose-effect curve, median-effect plot, combination index plot, isobologram, dose-reduction index plot, and polygonogram for in vitro or in vivo studies. This theoretical development, experimental design, and computerized data analysis have facilitated dose-effect analysis for single drug evaluation or carcinogen and radiation risk assessment, as well as for drug or other entity combinations in a vast field of disciplines of biomedical sciences. In this review, selected examples of applications are given, and step-by-step examples of experimental designs and real data analysis are also illustrated. The merging of the mass-action law principle with mathematical induction-deduction has been proven to be a unique and effective scientific method for general theory development. The median-effect principle and its mass-action law based computer software are gaining increased applications in biomedical sciences, from how to effectively evaluate a single compound or entity to how to beneficially use multiple drugs or modalities in combination therapies.

Synergistic inhibition of HIV-1 by an antisense oligonucleotide and nucleoside analog reverse transcriptase inhibitors

We have studied the effects of the gag antisense phosphorothioate oligonucleotide GEM 91 and mismatch antisense controls on the antiviral activities of ddC and other nucleoside analogs in HIV-infected MT-4 cells using a cytoprotection based assay. Under standard assay conditions, i.e. simultaneous incubation of drugs, HIV-1 IIIB and MT-4 cells, both GEM 91 and mismatch controls interacted synergistically with ddC resulting in an approximate 40-fold decrease in the IC50 value of ddC; this suggests a potent but sequence non-specific effect of GEM 91. Under post-adsorption assay conditions, i.e. pre-incubation of virus and cells and removal of excess HIV before drug addition, GEM 91 exhibited synergism with ddC, with an approximate 5-fold decrease in ddC IC50 value. This favorable interaction was not seen with any of the mismatch oligonucleotides, suggesting the involvement of a sequence-specific mechanism of action. Similar results were seen with the thymidine analogs AZT and d4T in combination with GEM 91. These data suggest a potential role for GEM 91 and future sequence-specific antisense drugs in combination with nucleoside analogs for the treatment of HIV infection. It is essential that potential interactions between new and existing classes of anti-HIV drugs are studied extensively as antiretroviral drug combinations become increasingly more complex.

Inhibition of Rev activity and human immunodeficiency virus type 1 replication by antisense oligodeoxynucleotide phosphorothioate analogs directed against the Rev-responsive element

The interaction between the Rev protein of human immunodeficiency virus type 1 and its highly structured and conserved RNA target, the Rev-responsive element, is required for virus replication. We demonstrate that antisense oligodeoxynucleotide phosphorothioate analogs directed against the Rev-responsive element effectively inhibit Rev activity, as well as human immunodeficiency virus type 1 replication, and are candidates for antiviral therapy.