Conformational change in the floor of the human rhinovirus canyon blocks adsorption to HeLa cell receptors.

A series of eight antiviral compounds complexed with human rhinovirus 14 (HRV-14) were previously shown to displace segments of polypeptide chains in the floor of the "canyon" by as much as 0.45 nm in C-alpha positions from the native conformation (J. Badger, I. Minor, M. J. Kremer, M. A. Oliveira, T. J. Smith, J. P. Griffith, D. M. A. Guerin, S. Krishnaswamy, M. Luo, M. G. Rossman, M. A. McKinlay, G. D. Diana, F. J. Dutko, M. Fancher, R. R. Rueckert, and B. A. Heinz, Proc. Natl. Acad. Sci. USA 85:3304-3308, 1988). Because the canyon is thought to serve as the viral receptor-binding site (M. G. Rossmann, E. Arnold, J. W. Erickson, E. A. Frankenberger, J. P. Griffith, H. J. Hecht, J. E. Johnson, G. Kamer, M. Luo, A. G. Mosser, R. R. Rueckert, B. Sherry, and G. Vriend, Nature [London] 317:145-153, 1985; M. G. Rossmann and R. R. Rueckert, Microbiol. Sci. 4:206-214, 1987), these compounds were assessed for their ability to block adsorption of HRV-14 to HeLa cell membrane receptors. In parallel experiments, the compounds were assessed directly for antiviral activity in an in vitro plaque reduction assay in intact HeLa cells. All eight compounds blocked the adsorption of 50% of HRV-14 at approximately the same concentration required to reduce the number of visible plaques by 50% (MIC). A structurally related compound which was inactive in the plaque reduction assay had no effect on HRV-14 binding. A drug-resistant mutant of HRV-14 (Leu-1188), which was less sensitive to the eight compounds in plaque reduction assays was similarly less sensitive in the adsorption assay. We propose that the conformational changes in the floor of the HRV-14 canyon induced by these compounds substantially decrease adsorption of the virion to its receptor. These results provide further evidence for the role of the HRV canyon in receptor binding.

In vitro activity of WIN 51711, a new broad-spectrum antipicornavirus drug.

WIN 51711 (5-[7-[4-(4,5-dihydro-2-oxazolyl)phenoxy]heptyl]-3-methylisoxazole), a new antipicornavirus drug, is a potent inhibitor of human entero- and rhinoviruses at concentrations not inhibitory to HeLa cell growth. In plaque reduction assays, WIN 51711 reduced plaque formation by 9 enteroviruses and 33 rhinoviruses, with MICs of 0.004 to 0.17 and 0.004 to 6.2 micrograms/ml, respectively. Addition of WIN 51711 to infected cells at concentrations of 0.02 to 5.0 micrograms/ml reduced the yield of picornaviruses by 90%. Other RNA viruses (nonpicornaviruses) and DNA viruses were unaffected by the compound.

Virucidal activity of glutaric acid and evidence for dual mechanism of action.

Rhinoviruses as a group are notably sensitive to inactivation in solutions with a pH of less than 5.3. Glutaric acid appears to possess virucidal activity in addition to the aciduant effect against rhinoviruses. A model system in which rhinovirus type 14 was incubated in the presence of glutaric acid (GA) (pH 4.0) at 0 degrees C was devised to separate intrinsic virucidal activity from the aciduant effect. Under these conditions, virucidal activity against rhinovirus type 14 was directly related to the concentration of GA present and the proportion of the acid in the diprotonated form. The virucidal activities of GA and several other compounds, including GA analogs and other mono- and dicarboxylic acids, were tested under the conditions described. In general, as the alkane bridge separating two carboxylic acid functions was lengthened, virucidal activity decreased. When 26 additional strains of rhinoviruses were tested in the model system, 19 were inactivated slowly enough to be compared. Of these, 63% were more susceptible to GA than to sodium acetate buffer and 26% were more susceptible to sodium acetate buffer. Eleven percent were resistant to both GA and sodium acetate buffer. The virucidal activity of GA for a majority of strains tested appeared to be due to combination of low pH and another mechanism of action presumably unrelated to pH.

Preliminary studies of the mode of action of arildone, a novel antiviral agent.

Arildone (also known as Win 38020), a novel aryl diketone, inhibited replication of herpes simplex virus type 2 in tissue culture by interfering with an event that occurs prior to 6 h postinfection. The inhibition could be partially reversed by washing. Although the exact mechanism of action is unknown, neither viral deoxyribonucleic acid nor viral proteins were synthesized in the presence of arildone.