Combined effect of selected antiviral substances of natural and synthetic origin. II. Anti-influenza activity of a combination of a polyphenolic complex isolated from Geranium sanguineum L. and rimantadine in vivo.

The synergistic effect shown by the combination of a natural product, polyphenolic complex (PC) isolated from Geranium sanguineum L., and rimantadine (R) in vitro and in ovo [7], encouraged us to continue these studies by in vivo testing. A marked protective effect in experimental influenza virus A (H3N2) infection in mice was found when PC was applied nasally (i.n.) (1.0 mg/kg) only once 6 h before infection in combination with R applied orally in concentration 10.5 and 2.5 mg/kg 2h before and 2.24 and 48 h after viral inoculation (PI = 72.55%, 55% and 57.8% respectively).

Effects of streptovirudin on influenza viruses type A and B: inhibition of the lipid-linked oligosaccharide synthesis of fowl plague virus.

Antibiotics of the streptovirudin complex (SV) inhibited the growth of influenza A and B viruses such as influenza A/fowl plague virus (FPV), strain Weybridge (Hav1 Neq1), influenza A/England 42/72 (H3N2), influenza A/Port Chalmers 1/73 (H3N2), influenza B/Leningrad 235/74, influenza B/Tokyo 7/66, and influenza B/Jamagata in chick embryo cell (CEC) cultures, in permanent canine kidney cells (MDCK), and in suspended fragments of chick embryo chorioallantoic membranes (CAM). As revealed by spectrophotometric turbidity measurements, SV completely inhibited the FPV-induced cytopathic effect (CPE). A 99.99% reduction of infectious virus yield was obtained in one-step growth cycle experiments and in the plaque reduction test. The haemagglutination inhibition titres of influenza viruses in suspended CAM fragment cultures in the presence of SV drugs were also substantially reduced. The incorporation assays indicated that SV exhibited no effect on virus-induced RNA synthesis, but influenced virus maturation by inhibition of lipid-linked oligosaccharide synthesis. A partial protection from infection was found in influenza virus A/England infected mice.

Antiviral action of dipyridamole and its derivatives against influenza virus A.

Dipyridamole proved to be active against influenza viruses A/England 42/72, A/Bangkok 1/79 and A/fowl plague (FPV). The antiviral activities assayed by various methods varied from 90-99 per cent. No inhibition was found against influenza virus B/Leningrad 235/74 in vitro. Three dipyridamole derivatives were significantly active in tissue cultures against influenza virus A/England 42/72 and A/FPV. In white mice infected with influenza virus A/England 42/72 dipyridamole administered orally showed a protection rate of 62.5 per cent.

Antiviral activity of hetarylhydrazones.

Some hetarylhydrazones showed antiviral activity against Mengo virus in vitro. The replication of influenza A and B viruses was affected neither in vitro (chick chorioallantoic membranes) nor in vivo (mice). Based on dose response curves of the active hetarylhydrazones the compound Z 98/69 appeared most effective in vitro. This compound neither inactivated the extracellular virus nor inhibited its adsorption and penetration; it reduced virus replication when added 1-3 hr after Mengo virus inoculation. As shown by plaque reduction test vaccinia virus was also inhibited. A partial inhibition of rhinovirus 1B multiplication was observed whereas other picornaviruses were not affected.

Dipyridamole, an inhibitor of mengovirus replication in FL and L cells.

Dipyridamole showed an antiviral activity aganinst mengovirus in FL cells using the agar diffusion plaque inhibition test, plaque reduction test, tube titration test, and virus yield test after one replication cycle. With the last two tests mentioned above the inhibitory action was also confirmed in L cells. In consequence of the known transport inhibition of uridine into the cell in presence of dipyridamole only a very small incorporation of 3H-uridine into acid-insoluble material could be demonstrated. Applying the method of prelabelling of FL cells at 16 degrees C for 1 h with subsequent addition of dipyridamole the drug failed to show an effect on cellular RNA synthesis per se in uninfected cells whereas the viral RNA synthesis in mengo-virus-infected L cells was completely depressed.