Inhibition of HIV-1 Replication and Activation of RNase L by Phosphorothioate/Phosphodiester 2′,5′-Oligoadenylate Derivatives

2',5'-Oligoadenylate (2-5A) derivatives have been designed to act distal to the human immunodeficiency virus-1 (HIV-1)-induced blockade in the 2-5A synthetase/RNase L antiviral pathway. Stereochemical modification of individual internucleotide linkages of the 2-5A molecule was accomplished by phosphoramidite and phosphotriester chemical syntheses. Phosphorothioate/phosphodiester trimer and tetramer 2-5A derivatives revealed differences in the stereodynamics of activation of RNase L and inhibition of HIV-1 replication. The first and second internucleotide linkages are critical for activation of recombinant, human RNase L; A(R(p))ApA, A(S-p)ApA and ApA(R(p))A are agonists (IC50 = 2 x 10(-7), 2 x 10(-6), and 8 x 10(-6) M); ApA(S-p)A is an antagonist. The second and third internucleotide linkages are crucial for activation of murine RNase L; ApA(R(p))A, ApA(R(p))ApA, and ApApA(R(p))A are agonists (IC50 = 5 x 10(-7) M); ApA(S-p)A, ApA(S-p)ApA, and ApApA(S-p)A are antagonists. Inhibition of HIV-1-induced syncytia formation by the phosphorothioate/phosphodiester derivatives is specific for derivatives with substitution at the 2',3'-terminus. ApA(R(p))A, ApA(S-p)A, ApApA(R(p))A, and ApApA(S-p)A are potent inhibitors of HIV-1-induced syncytia formation (80-, 10-, 40-, and 15-fold more inhibitory, respectively, than solvent control). HIV-1 infection results in enhanced uptake and accumulation of ApA(R(p))A and ApA(S-p)A (7- and 10-fold, respectively). These stereochemically modified 2-5A derivatives are taken up preferentially by HIV-1-infected cells and show promise in anti-HIV-1 chemotherapy.