Relationship of Molecular Size of rI n :rC n (Poly I:C) to Induction of Interferon and Host Resistance

Summary

Preparations of high molecular weight rI_n:rC_n were exposed to sonic radiation. A decrease in the average molecular weight of the polynucleotide complexes after treatment was accompanied by an exponential decrease in viscosity of the preparation, an increase in the sensitivity of the polynucleotide complex to degradation by pancreatic ribonuclease, a decrease in the thermal transition midpoint, and a decrease in the hyperchromicity observed during thermal transition.

The lower molecular weight rI_n:rC_n complexes were tested for their capacity to induce interferon in rabbits and resistance against VSV infection in cell culture and PVM infection in mice. Sonic-treated preparations of rI_n:rC_n reduced to an average molecular weight of approximately 4.6 × 10⁵ were markedly reduced in capacity to protect mice against PVM infection, compared with untreated rI_n:rC_n preparations containing complexes having an average molecular weight of approximately 7.8 × 10⁶. The capacity of sonic-treated rI_n:rC_n to induce production of rabbit interferon and resistance to virus infection in cell culture was more resistant to molecular weight reduction. Significant decrease in activity was observed in rI_n:rC_n fractions with approximate molecular weights less than 1.2 × 10⁵.