Retroviral inhibition by antisense oligonucleotides determined by intracellular stability

Development of a sustained-release biodegradable polymer delivery system for site-specific delivery of oligonucleotides: characterization of P(LA-GA) copolymer microspheres in vitro

Development of a Sustained-Release Biodegradable Polymer Delivery System for Site-Specific Delivery of Oligonucleotides: Characterization of P(LA-GA) Copolymer Microspheres In Vitro Antisense oligodeoxynucleotides (ODNs) can selectively inhibit individual gene expression provided they gain access to and remain stable at the target site for a sufficient period of time. Biodegradable sustained-release delivery systems may facilitate site-specific delivery and also prevent degradation of ODNs by nucleases whilst delivering the nucleic acid in a controlled manner to the desired site of action. In this study, we have characterized biodegradable poly (lactide-co-glycolide) (P(LA-GA)) 50:50 microspheres for the potential delivery of antisense oligonucleotides in vivo. Phosphodiester (PO) oligonucleotides complementary to either c-myc proto-oncogene or the tat gene in HIV-RNA were adequately incorporated within P(LA-GA) microspheres with entrapment efficiencies up to 60% depending on particles size. In vitro release profiles of antisense nucleic acids from 10-20 microm size microspheres over 56 days in physiological buffer were triphasic. Profiles were characterised by an initial burst effect during the first 48 hours (phase 1) of release followed by a more sustained release (phase 2) with an additional increased release (phase 3) being observed after 25 days which corresponded with bulk degradation of the copolymer matrix. The release profiles were influenced by microsphere size, copolymer molecular weight, ODN loading, ODN length and by the pH of release medium used. The serum stability of PO ODNs was significantly improved when entrapped within P(LA-GA) microspheres and the hybridization capability, as assessed by duplex melting (Tm) measurements, of released ODN was not impaired by the double-emulsion microsphere fabrication procedure used. Thus, P(LA-GA) microspheres appear to be promising candidates for improving site-specific delivery profiles for ODNs and are worthy of further evaluation in vivo.

Uptake and efflux of intact antisense phosphorothioate deoxyoligonucleotide directed against angiotensin receptors in bovine adrenal cells

Antisense oligonucleotide (AS-ODN) inhibition of angiotensin receptors (AT1-R) offers a potentially novel therapeutic approach for hypertension, left ventricular hypertrophy and other aspects of cardiovascular disease. To clarify questions concerning cellular uptake and retention of these oligos, we quantified the trafficking and stability of phosphorothioated modified AS-ODN to AT1 receptor mRNA in adrenal cells, using visual and chromatographic analysis. The AS-ODN to AT1 receptor mRNA was effective in significantly inhibiting AT1 receptor binding in a dose dependent manner. FITC-labeled ODNs were used to determine the cellular uptake in bovine adrena cortex cells; using confocal microscopy, rapid cellular uptake of 15-mer ODNs was observed. Uptake is initially rapid (30 min to 4 h) followed by a slower uptake process 24 h and after. The cellular accumulation of ODN involves a dynamic balance between influx and efflux processes. Efflux of FITC-ODN had a f1/2 = 4.6 days. Uptake was time and dose dependent. No obvious degradation of intracellular ODNs occurred as shown by intact peaks for 15-mer ODN on thin layer chromatography. The results suggest that the AS-ODN to AT1 receptor mRNA was resistant to cellular nucleases. The FITC-ODN accumulated mainly in the nucleus and remained there intact for up to 3 days. No significant change in target mRNA was observed by quantitative RT-PCR. Therefore the antisense inhibition mechanism of this ODN does not appear to stimulate RNase H or block transcription. Since the ODN accesses the nucleus, the results imply that the ODN inhibits specific mRNA transport into the cytoplasm. The data show that AS-ODN, for inhibition of AT1 receptors, is rapidly taken up and stable in cells and produces specific inhibition of AT1 receptors.

Inhibition of HIV replication by immunoliposomal antisense oligonucleotide

The sequence-specific suppression of HIV-1 replication using CD4 monoclonal-antibody-targeted liposomes, containing Rev antisense phosphorothioate oligonucleotides is described. Liposomes were prepared by encapsulating the 20-mer antisense DNA sequence of the rev HIV-1 regulatory gene, in the form of a phosphorothioate oligonucleotide. Specific targeting was accomplished by conjugating anti-CD4 mouse monoclonal antibody to the surface of the liposomes. HIV-1-infected H9 cells as well as peripheral blood T-lymphocytes were incubated with the immunoliposomes of antisense found to have potential antiviral effect. HIV-1 replication was reduced by 85% in antisense immunoliposome-treated H9 cells and peripheral blood lymphocytes, whereas the inhibition of HIV-1 replication was not observed using either empty immunoliposomes or immunoliposomes containing scrambled Rev phosphorothioate oligonucleotide sequences. The antiviral activity of both the free and the encapsulated oligonucleotides were assessed by p24, reverse transcriptase (RT) assays and polymerase chain reaction (PCR) analysis. Liposome preparations demonstrated minimal toxicity in H9 as well as in peripheral blood lymphocyte cell culture experiments. These in vitro culture results demonstrate the potential efficacy of immunoliposomes to inhibit HIV replication.