In vitro inhibitory effects of dual combinations of picornavirus replication inhibitors.

To assess the possible interactions among picornavirus replication inhibitors, inhibitory effects of dual combinations of enviroxime, disoxaril, arildone, S-7, guanidine, PTU-23, and HBB on poliovirus type 1 (Mahoney) replication in FL cells were tested. Beforehand, the 50% inhibitory concentration (IC50) in the plaque inhibition test was been determined for each individual compound, i.e. enviroxime-0.2 micromol/l, disoxaril-0.3 micromol/l, arildone-2.7 micromol/l, (S-7)-100 micromol/l, guanidine-200 micromol/l, (PTU-23)-200 micromol/l, and HBB-300 micromol/l. Each of the dual combinations, in which enviroxime or HBB was one of the partners, showed synergistic or additive effects. Combining disoxaril with enviroxime, HBB or PTU-23 resulted in synergism, while combining it with guanidine, S-7 or arildone led to antagonism. Arildone showed additive or synergistic effects when combined with enviroxime, HBB and PTU-23, and antagonistic ones when combined with disoxaril, S-7 or guanidine. All dual combinations of PTU-23 were synergistic with the exception of the pair of PTU-23 + guanidine that was antagonistic. Guanidine had additive to synergistic interactions with HBB or enviroxime but antagonistic ones with disoxaril, arildone and PTU-23. Guanidine or PTU-23 when combined with S-7 showed an unusual effect - synergistic one with an antagonistic zone. The combinations of S-7 with enviroxime or HBB were synergistic but those with disoxaril or arildone were antagonistic. Research on interactions of picornavirus replication inhibitors could possibly contribute to the development of efficient chemotherapy of infectious diseases caused by picornaviruses as well as to the better understanding of the mode of action of those inhibitors.