Inhibition of HIV Type 1 Replication in CD4 + and CD14 + Cells Purified from HIV Type 1-Infected Individuals by the 2-5A Agonist Immunomodulator,2-5A N6B

Two major interferon (IFN)-mediated antiviral defense enzymes are double-stranded (ds)RNA-dependent 2′,5′-oligoadenylate (2-5A) synthetase (2-5OAS) and p68 kinase (PKR). When activated by dsRNA, 2-5OAS synthesizes 2-5A, which binds to and activates RNase L. Activated RNase L hydrolyzes single-stranded viral RNA, thereby inhibiting viral protein synthesis. HIV-1 inhibits the IFN-mediated intracellular antiviral pathways. We have reported the synthesis and characterization of a nuclease-resistant 2-5A agonist (2-5A^N6B) that overcomes the HIV-1 induced blockades by restoring the 2-5OAS/RNase L antiviral pathway (Homan JW, et al., J Acquir Immune Defic Syndr 2002;30:9–20). The objective of this study was to test the effect of 2-5A^N6B on chronically infected CD4⁺ T lymphocytes and CD14⁺ monocytes derived from HIV-1-seropositive individuals. Wild-type HIV-1 replication was effectively inhibited by 2-5A^N6B in CD4⁺ T lymphocytes and CD14⁺ monocytes purified from HIV-1 seropositive individuals (n = 18) compared to untreated cells. We also assessed the cytotoxicity of 2-5A^N6B and report that 2-5A^N6B exerts its anti-HIV-1 activity with no evidence of cytotoxicity (IC₉₀ > 100,000 nM). Furthermore, 2-5A^N6B did not alter the cellular RNA profile, affect CCR5 or CXCR4 coreceptor expression, or activate caspase-dependent apoptosis. Evidence is also provided to show that 2-5A^N6B, and naturally occurring 2-5A₄, act as ligands to activate human Toll-like receptor 4. These results indicate that the 2-5A agonist 2-5A^N6B has the potential to enhance host cell innate and acquired immune defense mechanisms against HIV-1 infection.