Effects of ribavirin on respiratory syncytial virus in vitro

Abstract

Ribavirin was demonstrated to have an antiviral effect on respiratory syncytial virus in vitro. A 50% reduction in plaque number was observed at concentrations of 3 to 10 Ag of ribavirin per ml. This effect was observed when the drug was added as late as 12 h postinfection. At concentrations of greater than 10 ,ug of ribavirin per ml, the size of the syncytial plaque also noticeably decreased. Ribavirin similarly decreased the number of infectious units released into the culture supernatant. The antiviral effect was observed to be inversely related to the size of the viral inoculum, although all concentrations above 3.2 jig of ribavirin per ml visibly lessened the cytopathic effect regardless of the inoculum. Cloning of respiratory synctial virus in inhibitory concentrations of ribavirin failed to show increased resistance to the drug.Ribavirin (1-f8-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a synthetic nucleQside that has antiviral properties against a large number of both ribonucleic acid and deoxyribonucleic acid viruses in vitro (5,14,20). In experimental influenza infections in mice, ribavirin has reduced mortality and increased survival time when administered by the oral (4, 6), intraperitoneal (6, 17, 18), and aerosol routes (17). In one study of experimental influenza infections in humans, ribavirin was shown to ameliorate symptoms and fever (8), although other investigators reported that lower doses had only marginal effectiveness against influenza (2, 19).The purpose of this study was to assess the in vitro susceptibility of respiratory syncytial virus (RSV) to ribavirin. Respiratory syncytial virus is a major cause of pneumomia, bronchiolitis, and other respiratory diseases in infants, young children, and even adults (6,16). An inactivated RSV vaccine failed to decrease the incidence of infection and was associated with the paradoxical development of more severe disease when natural infection occurred (7 Eagle minimum essential medium with 10% fetal calf serum (heat inactivated) containing 0.1 mM glutamine, penicillin (100 U/ml), gentamicin (50 j,g/ml), and amphotericin (2.5 ,ug/ml). After 16 to 18 h, the supernatant was aspirated and 0.2 ml of virus was added for 1 h. The wells were overlaid with 5 ml of minimum essential plaque medium containing 5% fetal calf serum, 0.3 mM glutamine, 0.6% agarose, penicillin, gentamicin, and amphotericin. The cultures were fed every 5 days by overlaying them with additional minimum essential plaque medium. Typically, an assay was incubated for 4 to 7 days before the syncytia were judged to be easily countable. The cells were then fixed for 1 h by the addition of 1 ml of 10% Formalin to each well, and the agarose was gently removed. Cells were stained with 0.1% methylene blue to facilitate counting of syncytial plaques.

Ribavirin Treatment Up-Regulates Antiviral Gene Expression via the Interferon-Stimulated Response Element in Respiratory Syncytial Virus-Infected Epithelial Cells

“…Others have shown that continuous exposure of airway cells to ribavirin for up to 1 week produces no detectable toxicity as measured by cell growth or release of lactate dehydrogenase into the culture medium (21,35). Our microarray data are consistent with these findings in that ribavirin treatment alone has only minor effects on epithelial gene expression, influencing the expression of only 31 genes (by twofold or less, ca.…”

“…In RSV-infected epithelial cells, ribavirin reduces plaque formation, the release of infectious virions, and F glycoprotein expression in a dose-dependent manner over the range of 10 to 100 g/ml without cellular toxicity in culture for up to 7 days (21,35). To determine the optimal concentration and timing of ribavirin treatment for the inhibition of viral transcription for our studies, A549 monolayers pretreated (2 h) or posttreated (1 h) with increasing concentrations of ribavirin were exposed to pRSV.…”

Inhibitory effects of antiviral compounds on respiratory syncytial virus replication in vitro

“…Hruska et al (17) reported an ED50 of 3 to 10 ,ug/ml for the inhibition of RSV plaque formation by ribavirin. In our assays, ribavirin exhibited an ED50 of 2.8 ,.ug/ml for the Long strain of RSV and an average ED50 of 5.8 ,ug/ml for eight different strains of RSV.…”

Ameliorating Effect of Dietary Xylitol on Human Respiratory Syncytial Virus (hRSV) Infection

“…Clinical trials of ribavirin in infants had marginal effects in reducing the need for mechanical ventilator support and the duration of hospitalization following hRSV infection, whereas its anti-hRSV effect has been clearly established in vitro and in a rodent model. [8][9][10] Thus, continuing efforts are needed to discover new agents that can prevent or treat hRSV infection. Xylitol is a well-known sugar substitute with the formula (CHOH) 3 (CH2OH) 2 .…”