Modified polyriboinosinic-polyribocytidylic acid complex: modulation of toxicity for rabbits by alterations in components.

In an earlier study the physiological effects encountered in humans of a modified complex of polyriboinosinic acid-polyribocytidylic acid [poly(I)-poly(C)] with carboxymethylcellulose and poly-L-lysine [poly(ICLC) (9S)], namely, the induction of high titers of serum interferon along with fever and hypotension, were reproduced in rabbits. In the present studies, also in rabbits, we evaluated effects of complexes with homopolymer polyribonucleotide sedimentation coefficients decreasing from 9S to 6S and 4S. Modified complexes of carboxymethylcellulose and poly-L-lysine with decreasing molecular weights were also tested. In several studies diphenhydramine and indomethacin were administered concomitantly. These experiments showed that at a daily intravenous dose of 0.2 mg/kg the various preparations of poly(I)-poly(C) (9S) and poly(I)-poly(C) (6S) induced falls in blood pressure, but stabilized complexes of poly(I)-poly(C) (4S) did not. Alterations in the molecular weights of carboxymethylcellulose and poly-L-lysine n the modified complex and the concomitant administration of diphenhydramine did not influence the occurrence or severity of untoward reactions. In rabbits, poly(ICLC) (4S) along with indomethacin induced high titers of serum interferon without fever or hypotension.