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

Abstract

We examined the inhibitory effect of 20 antiviral compounds, including ribavirin, on the replication of respiratory syncytial virus in HeLa and HEp-2 cell cultures. Of the compounds studied, pyrazofurin and 3-deazaguanine emerged as more potent inhibitors of respiratory syncytial virus than ribavirin. Based on their inhibitory effect on the cytopathogenicity of respiratory syncytial virus in HeLa cells, the average 50% effective dose of pyrazofurin and 3-deazaguanine for eight strains was 0.07 and 1.65 ,ug/ml, respectively; that of ribavirin was 5.82 p.g/ml. The cytotoxicity of these compounds for HeLa cells was examined by monitoring the incorporation of radiolabeled uridine into cellular RNA. The selectivity indexes of pyrazofurin and 3-deazaguanine exceeded that of ribavirin by 70-and 11-fold, respectively. Pyrazofurin, 3-deazaguanine, and ribavirin inhibited both viral antigen expression and syncytium formation in HeLa cell cultures, as assessed by an indirect immunofluorescence assay. In these assays, pyrazofurin and 3-deazaguanine again proved more potent than ribavirin. 2,5-Diamidinoindole and carbodine were less potent than ribavirin. Various other compounds, i.e., 3-adenin-9-yl-2-hydroxypropanoic acid isobutyl ester, 3-deazauridine, 3'-C-methyluridine, 5'-deoxy-5-fluorouridine, 5-cyanoimidazole-4-carboxamide, and its ribofuranosyl derivative, did not inhibit the cytopathic effect of the Long strain of respiratory syncytial virus at concentrations -125 pLg/ml. Tubercidin, 5-chlorotubercidin, xylotubercidin, neplanocin A, thiosemicarbazone R, and 3-methylquercetine were too toxic to HeLa cells for their inhibitory effects on respiratory syncytial virus to be examined.Respiratory syncytial virus (RSV) causes lower respiratory tract infections such as bronchiolitis and pneumonia in infancy and early childhood. Most clinicians consider RSV one of the most important agents of acute respiratory disease in children, and almost 50% of infants are expected to suffer from RSV infection during their first winter (15,16,20,32,35). Inactivated RSV vaccine does not protect against natural infection and leads to an unusual immune response and even lung inflammation during the course of a subsequent natural infection (21). Recent research efforts have therefore focused on the development of either potent live RSV vaccines or effective antiviral compounds.Following reports that ribavirin may reduce the severity of illness and amount of virus shed in acute respiratory infections due to RSV or influenza B virus (13,14,23,37), the drug has been approved in aerosol form for the chemotherapy of RSV infections. This has prompted the search for antiviral compounds that may be as effective, if not more effective, against RSV than ribavirin. We have now investigated the inhibitory effects of 20 antiviral compounds, including ribavirin, on the replication of RSV in vitro.MATERIALS AND METHODS Viruses. The Long, S-2, and S-8 strains of RSV were kindly provided by Y. Numazaki, National Sendai Hospital, Sendai, Japan. The 58-8, 58-7,...

Antiviral activities of ribavirin, 5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide, and 6'-(R)-6'-C-methylneplanocin A against several ortho- and paramyxoviruses

“…The origins of the viruses and preparations of the virus stocks have been reported previously (8,9,15). Subtypes, strains, abbreviations, and passage histories of the viruses were as follows.…”

In vitro Activity of a Novel Series of Polyoxosilicotungstates against Human Myxo-, Herpes- and Retroviruses

“…For the other viruses, confluent (MOCK, HeLa, Vero or E 6SM) cell cultures in 96-well microtitre trays were inoculated with virus at 100 CCID so (or with 100 plaque forming units of HCMV) per well in the presence of various concentrations of the test compounds. The cell cultures were further incubated at 35°C (for influenza A or B virus, RSV or parainfluenza type 3) or 37°C (for HSV-1, HSV-1 TK-, HSV-2 or HCMV), and virus-induced cytopathicity was monitored microscopically, as described previously (De Clercq et el., 1980;De Clercq, 1985;Kawana et al, 1987;Shigeta et al, 1988;Neyts et al, 1990). The concentration required to reduce virus-induced cytopathicity by 50% was estimated as the 50% inhibitory concentration (IC so ).…”

“…The virus stocks were prepared as described previously : influenza A virus (strain Ishikawa/7/82(H 3N2 »and influenza B virus (strain Singapore/222/79) (Shigeta et aI., 1988); RSV (strain Long) (Kawana et al, 1987); parainfluenza virus type 3 (strain VR-93) (De Clercq, 1985); HSV-1 (strain KOS), HSV-2 (strain G) and HSV-1 TK-(strain Field C/37/101) (De Clercq et al, 1980); HCMV (strain Davis) (Snoeck et al, 1988); HIV-1 (strain HTLV-lIls1LAI) and HIV-2 (strain LAV-2 ROD) (Pauwels et al, 1988). HIV-1 and HIV-2 were prepared from the culture supernatants of HIV-1-or HIV-2-infected cell lines (HUT-78/HTLV-IIIB and MT4/LAV-2 ROD, respectively).…”

Discovery of Novel Ribonucleoside Analogs with Activity against Human Immunodeficiency Virus Type 1

“…Our study, to the best of our knowledge, is the first to demonstrate the antiretroviral activity of formycin A. Many previous studies identified the activity of 3-deazauridine against riboviruses (20)(21)(22)(23)(24)(25)(26) and retroviruses (23,27). Interestingly, 3-deazauridine was previously observed to potentiate the anti-HIV-1 activity of 3TC and dideoxycytosine (28).…”