Application of the Agar-Diffusion Plaque-Inhibition Method for Testing Combination Antiviral Effects: PTU-23 and Guanidine Hydrochloride Interactions and Combined Effects on the Replication of Poliovirus 1

Original modifications of the agar-diffusion plaque inhibition method were used for testing the combination effect of anti-enteroviral substances. It was established that the anti-picornavirus compounds PTU- 23 and guanidine.HCl are antagonists when applied in combination against the replication of poliovirus 1 in cell cultures. Some significant differences in their activity were found: (i) guanidine antagonists did not influence the anti-poliovirus effect of PTU-23; (ii) Cu++ and Zn++ ions significantly increased the activity of PTU-23 towards poliovirus 1, whereas Zn++ ions had no effect on the antiviral activity of guanidine.HCl, and Cu++ ions manifested a marked antagonistic effect on the guanidine activity. Evidently, the anti-enterovirus activity of these compounds is directed to different targets in the virus replication cycle.