**3.1. Abitylguanide**

N′N′-anhydro-bis(β-hydroxy-ethyl)biguanide-HCl (abitylguanide) suppressed markedly the replication of a large spectrum of human AdVs, both standard laboratory strains and strains isolated from epidemic keratoconjunctivitis patients. The magnitude of inhibitory effect varied from 1.5 to 3.8 logs. A marked correlation was established between the value of inhibitory effect and belonging of tested AdVs to various subgroups, the strongest activity being found toward viruses of subgroup C (Rosen's subgroup III). The compound susceptible period of AdV 5 replication included the total growth cycle, but is especially pronounced during the exponential phase. This was established through timing-of-addition study in primary cell cultures of human embryo kidney cells. Electron microscopy study of AdV5 morphogenesis contributed substantially to the clearing-up of the mechanism of anti-AdV action of abitylguanide. It was registered that: (1) the compound decreased about 10-fold the percentage of cells in which mature or empty virions with the characteristic nuclear localization were observed; (2) a complete absence of paracrystals; (3) the number of cells with virus particles arranged in crystals in the nucleoplasm was strongly decreased [38].

The absence of crystalline inclusions established electron microscopically in our study correlated with the established pronounced decrease of infectivity and/or lower yields of viral progeny which is in line with the meaning [39] that the protein crystals might be involved in at late steps of the virus life cycle ensuring correct capsid assembly, virus maturation and infectivity. Discussing the mode of action of abitylguanide on AdV 5 replication it has to stress on the full coincidence of the data obtained electron microscopically with the results of the timing-of-addition study demonstrating the highly-pronounced compound-sensitivity of the virus growth in the exponential phase. On the basis of the mentioned data, abitylguanide can be considered a ligand of AdV capsid protein(s) [38].
