Poly I:C/poly-L-lysine: potent inducer of interferons in primates.

A soluble complex of poly I:C and poly-L-lysine (poly I:C/poly-L-lysine) has been prepared that induces high titers of circulating interferon in monkeys. By limiting the molar ratio of lysine to nucleotide to 0.5, a complex was formed that was soluble up to 2.0 mg poly I:C/ml of phosphate-buffered saline. Complexes of poly I:C with poly-L-lysine of various molecular weights, and in a constant ratio (0.5) of lysine to nucleotide, were evaluated for capacity to induce serum interferon in grivet monkeys. Substantial enhancement (10- to 100-fold) of the capacity of poly I:C to induce interferon in grivet monkeys was observed using poly I:C complexed with poly-L-lysines of molecular weight 10(4) daltons or greater. The poly I:C/poly-L-lysine as an effective inducer of interferon in grivet monkeys, rhesus monkeys, chimpanzees and marmosets. A high interferon titer (greater than 100 units/ml blood) was maintained in grivet monkeys by repeated daily administration of the complex. No long-term hyporesponsiveness was noted following repeat inductions over a period of months. The serum interferon produced in monkeys in response to poly I:C/poly-L-lysine resembled human leukocyte interferon in its biological characteristics.