Potentiation of poly I:C induced viral resistance by polycationic modified polypeptides.

The potentiation of polyI:C induced viral resistance by various side group modified polycationic polyglutamic acid derivatives was investigated. It was established that the efficacy of the various polycationic substances depends primarily on their macromolecular properties. Viscosity and the degree of cationic substitution have been found to be of paramount importance. The maximal potentiating efficacy, expressed as the minimum protective dose of polyI:C necessary for complete protection of cells in the presence of the polycations, was exerted by compounds of highest viscosity and degree of subsitution. The potentiating efficacy of the polycationic derivatives tested could only be observed in a relatively narrow range of concentration, depending on their viscosity and degree of substitution. In view of the extremely low minimal protective dose of polyI:C (10(-5) mug/ml) in the presence of our most effective compound it is assumed that the action of a few molecules of polyI:C may be sufficient to render a cell resistant against viral infection. Within the limits of the described experiments, the efficacy of polycationic derivatives did not seem to be influenced by the modification (e.g. quaternarization) of the cationic group.