Inhibition of HIV-1 replication by anti-trans-activation responsive polyamide nucleotide analog.

Efficient replication and gene expression of human immunodeficiency virus-1 (HIV-1) involves specific interaction of the viral protein Tat, with its trans-activation responsive element (TAR) which forms a highly stable stem-loop structure. We have earlier shown that a 15-mer polyamide nucleotide analog (PNA) targeted to the loop and bulge region of TAR blocks Tat-mediated transactivation of the HIV-1 LTR both in vitro and in cell culture (Mayhood et al., Biochemistry 39 (2000) 11532). In this communication, we have designed four anti-TAR PNAs of different length such that they either complement the entire loop and bulge region (PNA(TAR-16) and PNA(TAR-15)) or are short of few sequences in the loop (PNA(TAR-13)) or in both the loop and bulge (PNA(TAR-12)), and examined their functional efficacy in vitro as well as in HIV-1 infected cell cultures. All four anti-TAR PNAs showed strong affinity for TAR RNA, while their ability to block in vitro reverse transcription was influenced by their length. In marked contrast to PNA(TAR-12) and PNA(TAR-13), the two longer PNA(TARs) were able to efficiently sequester the targeted site on TAR RNA, thereby substantially inhibiting Tat-mediated transactivation of the HIV-1 LTR. Further, a substantial inhibition of virus production was noted with all the four anti-TAR PNA, with PNA(TAR-16) exhibiting a dramatic reduction of HIV-1 production by nearly 99%. These results point to PNA(TAR-16) as a potential anti-HIV agent.