Mode of action of the anti-AIDS compound poly(I).poly(C12U) (Ampligen): activator of 2',5'-oligoadenylate synthetase and double-stranded RNA-dependent kinase.
The mismatched double-stranded RNA (dsRNA), poly(I).poly(C12U), also termed Ampligen, exhibits a strong antiviral and cytoprotective effect on cells (human T-lymphoblastoid CEM cells and human T-cell line H9) infected with the human immunodeficiency virus type 1 (HIV-1). Untreated H9 cells infected with HIV-1 start to release the virus 3 days post-infection, while in the presence of 40 micrograms/ml (80 micrograms/ml) of poly(I).poly(C12U) the onset of virus production and release is retarded and does not occur before day 5 (day 6). We demonstrate that poly(I).poly(C12U) markedly extends the duration of the transient increase of 2',5'-oligoadenylate (2-5A) synthetase mRNA level and activity preceding virus production after infection of cells with HIV-1. Treatment of HeLa cells with poly(I).poly(C12U) was found to cause a significant increase in total (activated plus latent) 2-5A synthetase activity; no evidence was obtained that the level of latent (nonactivated) 2-5A synthetase is changed in cells treated with dsRNA plus interferon (IFN). Poly(I).poly(C12U) is able to bind and to activate 2-5A synthetase(s) from HeLa cell extracts. Addition of poly(I).poly(C12U) to HeLa cell extracts results in production of longer 2-5A oligomers (> or = 3 adenylate residues), which are better activators of RNase L. Both free and immobilized poly(I).poly(C12U) also bind to the dsRNA-dependent protein kinase (p68 kinase), resulting in autophosphorylation of the enzyme. Activation of the kinase by the free RNA occurs within a limited concentration range (10(-7) to 10(-6) grams/ml). Addition of HIV-1 Tat protein does not affect binding and activation of p68 kinase to poly(I).poly(C12U)-cellulose but strongly reduces the binding of the kinase to immobilized TAR RNA of HIV-1. We conclude that poly(I).poly(C12U) may antagonize Tat-mediated down-regulation of dsRNA-dependent enzymes.
Ushijima
H
H
Division of AIDS Virus, AIDS Research Center, National Institute of Health, Tokyo, Japan.
Rytik
P G
PG
Schäcke
H
H
Scheffer
U
U
Müller
W E
WE
Schröder
H C
HC
D015088:2',5'-Oligoadenylate Synthetase / Q000187:drug effects*; D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy*; D000998:Antiviral Agents / Q000494:pharmacology*; D001704:Biopolymers; D002460:Cell Line; D004722:Endoribonucleases / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D011070:Poly I-C / Q000494:pharmacology*; D011072:Poly U / Q000494:pharmacology*; D011485:Protein Binding; D011494:Protein Kinases / Q000187:drug effects*; D012330:RNA, Double-Stranded / Q000494:pharmacology*; D019892:eIF-2 Kinase
D000998:Antiviral Agents; D001704:Biopolymers; D012330:RNA, Double-Stranded; D011072:Poly U; C047490:poly(I).poly(c12,U); D011494:Protein Kinases; D019892:eIF-2 Kinase; D015088:2',5'-Oligoadenylate Synthetase; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease; D011070:Poly I-C