Self-inactivation of HIV by its own RT/RNase H

Reduction of gene expression by a hairpin-loop structured oligodeoxynucleotide: alternative to siRNA and antisense

BACKGROUND

We previously described the inhibition of HIV-1 replication by a 54-mer hairpin-loop structured oligodeoxynucleotide (ODN) A, which binds the polypurine tract (PPT) on HIV-1 RNA. ODN A was shown to lead to reduced viral RNA in virions or early during infection.

METHODS AND RESULTS

Here we demonstrated that ODN A was able to cause hydrolysis of viral RNA not only by retroviral RT-associated RNase H but also cellular RNase H1 and RNase H2 in vitro. Furthermore, ODN A reduced gene expression in a dose-dependent manner in a cell-based reporter assay where a PPT sequence was inserted in the 5' untranslated region of the reporter gene. The efficacy of ODN A was higher than that of its siRNA and antisense counterparts. By knocking down cellular RNases H, we showed that RNase H1 contributed to the gene silencing by ODN A but the possibility of a partial contribution of RNase H-independent mechanisms could not be ruled out.

GENERAL SIGNIFICANCE

Our findings highlight the potential application of hairpin-loop structured ODNs for reduction of gene expression in mammalian cells and underscore the possibility of using ODN A to trigger the hydrolysis of HIV RNA in infected cells by cellular RNases H.

Inhibition of influenza A virus replication by short double-stranded oligodeoxynucleotides

Influenza A virus causes prevalent respiratory tract infections in humans. Small interfering RNA (siRNA) and antisense oligonucleotides (asODNs) have been used previously for silencing the RNA genome of influenza virus. Here, we explored the use of partially double-stranded oligodeoxynucleotides (dsODNs) to suppress the production of influenza A virus in cell cultures and animal models. We were able to inhibit influenza A virus replication in cultured human lung cells as well as in the lungs of infected C57BL/6 mice by treatment with dsODN 3-h post-infection. In about 20% of the cases (15/77) the titer was reduced by 10- to 100-fold and in 10% up to 1,000-fold. The antiviral effects of dsODNs were dose-dependent, sequence-dependent and comparable to those of its antisense and siRNA analogues. Thus, dsODNs may be developed as an additional class of nucleic acids for the inhibition of influenza virus replication.