The present invention relates to antiviral compositions, agents, and methods of use. In particular, a phosphorothioate oligonucleotide with an optimized chain length is presented. Such phosphorothioate oligonucleotides have a chain length of at least 32 nucleotides and may be further optimized by having about 37 oligonucleotides. The phosphorothioate oligonucleotides of the present invention may be used in methods of inhibiting HIV activity, including the activity of HIV-1 and HIV-2.
