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(Rp)ApA, A(Sp)ApA and ApA(Rp)A are agonists (IC50 = 2 x 10(-7), 2 x 10(-6) and 8 x 10(-6) M); ApA(Sp)A is an antagonist. The second and third internucleotide linkages are crucial for activation of murine RNase L; ApA(Rp)A, ApA(Rp)ApA, and ApApA(Rp)A are agonists (IC50 = 5 x 10(-7) M); ApA(Sp)A, ApA(Sp)ApA, and ApApA(Sp)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(Rp)A, ApA(Sp)A, ApApA(Rp)A, and ApApA(Sp)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(Rp)A and ApA(Sp)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.

Changes in the 2-5A synthetase/RNase L antiviral pathway in a controlled clinical trial with poly(I)-poly(C12U) in chronic fatigue syndrome

Latent 2', 5'-oligoadenylate (2-5A) synthetase activity, bioactive 2-5A and RNase L activity were measured in extracts of peripheral blood mononuclear cells (PMBC) before and during a randomized, multicenter, placebo-controlled, double-blind study of poly(I)-poly(C12U) in individuals with chronic fatigue syndrome (CFS) as defined by the Centers for Disease Control and Prevention. The mean values for bioactive 2-5A and RNase L activity were significantly elevated at baseline compared to controls (p < .0001 and p = .001, respectively). In individuals that presented with elevated RNase L activity at baseline, therapy with poly(I)-poly(C12U) resulted in a significant decrease in both bioactive 2-5A and RNase L activity (p = .09 and p = .005, respectively). Decrease in RNase L activity in individuals treated with poly(I)-poly(C12U) correlated with cognitive improvement (p = .007). Poly(I)-poly(C12U) therapy resulted in a significant decrease in bioactive 2-5A and RNase L activity in agreement with clinical and neuropsychological improvements (Strayer DR, et al., Clin. Infectious Dis. 18:588-595, 1994). The results described show that poly(I)-poly(C12U) is a biologically active drug in CFS.

Upregulation of the 2-5A synthetase/RNase L antiviral pathway associated with chronic fatigue syndrome

Levels of 2',5'-oligoadenylate (2-5A) synthetase, bioactive 2-5A, and RNase L were measured in extracts of peripheral blood mononuclear cells (PBMCs) from 15 individuals with chronic fatigue syndrome (CFS) before and during therapy with the biological response modifier poly(I).poly(C12U) and were compared with levels in healthy controls. Patients differed significantly from controls in having a lower mean basal level of latent 2-5A synthetase (P < .0001), a higher pretreatment level of bioactive 2-5A (P = .002), and a higher level of pretherapy RNase L activity (P < .0001). PBMC extracts from 10 persons with CFS had a mean basal level of activated 2-5A synthetase higher than the corresponding control value (P = .009). All seven pretherapy PBMC extracts tested were positive for the replication of human herpesvirus 6 (HHV-6). Therapy with poly(I).poly(C12U) resulted in a significant decrease in HHV-6 activity (P < .01) and in downregulation of the 2-5A synthetase/RNase L pathway in temporal association with clinical and neuropsychological improvement. The upregulated 2-5A pathway in CFS before therapy is consistent with an activated immune state and a role for persistent viral infection in the pathogenesis of CFS. The response to therapy suggests direct or indirect antiviral activity of poly(I).poly(C12U) in this situation.