Induction of interferon by polyribonucleotides containing thiopyrimidines

Abstract
The influence of thioketo substitution in pyrimidine bases of double-stranded polynucleotides on interferon induction was investigated. The stabilizing effect of 2-thioketo substitution was reflected in the increased interferon inducing activity of poly(A-s2u) over that of poly(A-U). Poly (A-s2u) and poly(I).poly(s2C) were as effective as poly(I). poly(C) in rabbit cells. Poly(I)·poly(C) and poly(I).poly (s2c) were compared in several animal species. No differences in biological effects were observed in rabbits and dogs. In rodents, poly(I)-poly(s2c) was less effective and less toxic. Poly(I).poly(s2c) was highly resistant against degradation by human serum. Further investigations seem to be justified to elucidate whether this property offers any advantages for the potential clinical utilization of poly(I).poly(s2c).