A common mode of antiviral action for ammonium ions and various amines

Polymers in the Medical Antiviral Front-Line

Antiviral polymers are part of a major campaign led by the scientific community in recent years. Facing this most demanding of campaigns, two main approaches have been undertaken by scientists. First, the classic approach involves the development of relatively small molecules having antiviral properties to serve as drugs. The other approach involves searching for polymers with antiviral properties to be used as prescription medications or viral spread prevention measures. This second approach took two distinct directions. The first, using polymers as antiviral drug-delivery systems, taking advantage of their biodegradable properties. The second, using polymers with antiviral properties for on-contact virus elimination, which will be the focus of this review. Anti-viral polymers are obtained by either the addition of small antiviral molecules (such as metal ions) to obtain ion-containing polymers with antiviral properties or the use of polymers composed of an organic backbone and electrically charged moieties like polyanions, such as carboxylate containing polymers, or polycations such as quaternary ammonium containing polymers. Other approaches include moieties hybridized by sulphates, carboxylic acids, or amines and/or combining repeating units with a similar chemical structure to common antiviral drugs. Furthermore, elevated temperatures appear to increase the anti-viral effect of ions and other functional moieties.

Radioprotective and Antitumor Activity Evaluation of Newly Synthesized Adamantyl Tenocyclidines

Several adamantyl derivatives of thienyl phencyclidine (tenocyclidine; TCP) were newly sythesized and characterized: adamantyl derivatives containing piperidine (TAPIP), pyrrolidine (TAPYR), and morpholine (TAMORPH) groups. Their biological activity was evaluated by in vitro testing of their effect on the proliferative and reproductive ability (cytotoxicity) of a human tumor cell strain and nonmalignant mouse fibroblasts in culture. We also tested them for their radioprotective effect after ionizing irradiation, and as anticancer agents on the same human tumor cell strain. Compared with TCP, adamantyl derivatives are less toxic and have outstanding radioprotective properties. These derivatives (especially TAMORPH) increase apoptotic death of human malignant cells. The radiation-modifying effect studied on C3Hf mice in vivo showed that the adamantyl derivatives of TCP have a more enhanced radioprotective effect and that they are less toxic than TCP itself. The present data are discussed and compared with those previously reported for structurally related phencyclidine derivatives.

Adamantane as a brain-directed drug carrier for poorly absorbed drug. 2. AZT derivatives conjugated with the 1-adamantane moiety

Five AZT (azidothymidine) prodrugs conjugated with the 1-adamantane moiety via an ester bond were synthesized to improve the transport of AZT into the central nervous system (CNS). In in vitro degradation studies with rat and human plasma, it was demonstrated that the prodrugs were degraded enzymatically and converted quantitatively to their parent drug. AZT. As assessed by octanol-buffer partitioning, the prodrugs were much more lipophilic than AZT and were expected to penetrate the blood-brain barrier (BBB) readily. In in vivo studies, in which the prodrugs were administered intravenously to rat, the prodrugs in brain tissue were detected at 7-18 times higher concentrations than AZT in spite of the negligible amount of the prodrug in the cerebrospinal fluid. These results indicate that the introduction to AZT of the 1-adamantane moiety results in the enhancement of the BBB penetration. This pharmaceutical approach would be beneficial for the efficient treatment of the CNS infection by human immunodeficiency virus.

Picornavirus inhibitors

Picornaviruses are among the best understood animal viruses in molecular terms. A number of important human and animal pathogens are members of the Picornaviridae family. The genome organization, the different steps of picornavirus growth and numerous compounds that have been reported as inhibitors of picornavirus functions are reviewed. The picornavirus particles and several agents that interact with them have been solved at atomic resolution, leading to computer-assisted drug design. Picornavirus inhibitors are useful in aiding a better understanding of picornavirus biology. In addition, some of them are promising therapeutic agents. Clinical efficacy of agents that bind to picornavirus particles has already been demonstrated.

Infectious entry pathway of influenza virus in a canine kidney cell line

The entry of fowl plague virus, and avian influenza A virus, into Madin-Darby canine kidney (MDCK) cells was examined both biochemically and morphologically. At low multiplicity and 0 degrees C, viruses bound to the cell surface but were not internalized. Binding was not greatly dependent on the pH of the medium and reached an equilibrium level in 60-90 min. Over 90% of the bound viruses were removed by neuraminidase but not by proteases. When cells with prebound virus were warmed to 37 degrees C, part of the virus became resistant to removal b neuraminidase, with a half-time of 10-15 min. After a brief lag period, degraded viral material was released into the medium. The neuraminidase-resistant virus was capable of infecting the cells and probably did so by an intracellular route, since ammonium chloride, a lysosomotropic agent, blocked both the infection and the degradation of viral protein. When the entry process was observed by electron microscopy, viruses were seen bound primarily to microvilli on the cell surface at 0 degrees C and, after warming at 37 degrees C, were endocytosed in coated pits, coated vesicles, and large smooth-surfaced vacuoles. Viruses were also present in smooth-surfaced invaginations and small smooth-surfaced vesicles at both temperatures. At physiological pH, no fusion of the virus with the plasma membrane was observed. When prebound virus was incubated at a pH of 5.5 or below for 1 min at 37 degrees C, fusion was, however, detected by ferritin immunolabeling. t low multiplicity, 90% of the prebound virus became neuraminidase-resistant and was presumably fused after only 30 s at low pH. These experiments suggest that fowl plague virus enters MDCK cells by endocytosis in coated pits and coated vesicles and is transported to the lysosome where the low pH initiates a fusion reaction ultimately resulting in the transfer of the genome into the cytoplasm. The entry pathway of fowl plague virus thus resembles tht earlier described for Semliki Forest virus.

On the entry of Semliki forest virus into BHK-21 cells

The pathway by which semliki forest virus (SFV), a membrane-containing animal virus, enters BHK-21 cells was studied morphologically and biochemically. After attaching to the cell surface, the majority of viruses was rapidly trapped into coated pits, internalized by endocytosis in coated vesicles, and sequestered into intracellular vacuoles and lysosomes. Direct penetration of viruses through the plasma membrane was never observed. To assess the possible involvement of lysosomes in the release of the genome into the cytoplasm, the effect of five lysosomotropic agents, known to increase the lysosomal pH, was tested. All of these agents inhibited SFV infectivity and one, chloroquine (the agent studied in most detail), inhibited a very early step in the infection but had no effect on binding, endocytosis, or intracellular distribution of SFV. Thus, the inhibitory effect was concluded to be either on penetration of the nucelocapsid into the cytoplasm or on uncoating of the viral RNA. Possible mechanisms for the penetration of the genome into the cytoplasm were studied in vitro, using phospholipids-cholesterol liposomes and isolated SFV. When the pH was 6.0 or lower, efficient fusion of the viral membranes and the liposomal membranes occurred, resulting in the transfer of the nucleocapsid into the liposomes. Infection of cells could also be induced by brief low pH treatment of cells with bound SFV under conditions where the normal infection route was blocked. The results suggest that the penetration of the viral genome into the cytosol takes place intracellularly through fusion between the limiting membrane of intracellular vacuoles and the membrane of viruses contained within them. The low pH required for fusion together with the inhibitory effect of lysosomotropic agents implicate lysosomes, or other intracellular vacuoles with sufficiently low pH, as the main sites of penetration.

Early events in cell-animal virus interactions

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The nature of the toxic reaction of influenza virus towards lung tissue

The inoculation of large doses of unadapted influenza virus intranasally into mice results in the production of severe lung lesions. This toxic effect is a result of the entry of virus particles into the lung cells followed by uncoating of the virus ribonucleic acid.The toxic property of the virus is destroyed by procedures which destroy or modify the nucleic acid such as exposure to monochromatic UV light of wavelength 2537 A, or treatment with hydroxylamine or Bayer A139. Reagents acting on amino groups are particularly effective as they react with the nucleic acid and probably also interfere with penetration of virus into the cell.Toxicity is also destroyed by mercurials which probably prevent uncoating of the nucleic acid by union with disulphide bonds, and by oxidizing agents such as iodine, permanganate, osmic acid and hydrogen peroxide under condition which suggest possible action on some constituent of the virus containing methionine.The toxic effect produced by the inoculation of large doses of unadapted virus intranasally in mice is associated with the occurrence of an incomplete growth cycle in which there is full production of RNP antigen but no production of haemagglutinin or infective virus.