Antiviral activity of conjugates between poly(L-lysine) and synthetic oligodeoxyribonucleotides.

Short (14 to 20-mer range) synthetic oligodeoxyribonucleotides (oligos) allow to modulate specifically viral or cellular gene expression at various stages thus providing a versatile tool for fundamental studies and a rational approach to antiviral chemotherapy. Several problems, such as metabolic stability and efficient cell internalization of oligos, still limit this approach appreciably, as briefly discussed here. We demonstrate here that the conjugation of 15-mer (beta)-anomeric oligos to poly(L-lysine) allows a specific protection of various cell lines against vesicular stomatitis virus infection at concentrations lower than 1 microM. This can be achieved with oligos complementary to the viral N-protein mRNA initiation site or to viral intergenic sequences, i.e., to untranscribed regions. No antiviral activity can be obtained with (alpha)-anomeric oligos directed against the same targets, although such analogues are much more resistant to nuclease degradation and form stable hybrids, at least in cell-free experiments.

Alpha-DNA.IX: Parallel annealing of alpha-anomeric oligodeoxyribonucleotides to natural mRNA is required for interference in RNase H mediated hydrolysis and reverse transcription.

ps- and aps-alpha anomeric oligodeoxyribonucleotides were designed to recognize in parallel (ps) or antiparallel (aps) orientation two different sites of a 1000 base-long mRNA. Northern blots experiments indicate that only ps-alpha-oligonucleotides were able to hybridize to the mRNA target. Furthermore, only ps-alpha-oligonucleotides were able, in a sequence specific way, to protect the mRNA target against RNase H mediated hydrolysis or to inactivate the priming capacity of beta-oligodeoxynucleotide probes in reverse transcription. Formation of parallel-stranded mRNA alpha-oligonucleotide miniduplexes which prevents hybridization of beta-oligonucleotide probes is the most likely mechanism accounting for these results. Use of alpha-oligonucleotides as potential gene control agents is discussed.

Antiviral activity and possible mechanisms of action of oligonucleotides-poly(L-lysine) conjugates targeted to vesicular stomatitis virus mRNA and genomic RNA.

Synthetic oligonucleotides (oligomers) complementary to vesicular stomatitis virus (VSV) N protein mRNA have specific antiviral properties at concentrations lower than 1 microM when they are covalently linked to poly(L-lysine) (PLL). Since it is generally postulated that antisense oligomers act at the translational level, oligomers with potential targets on VSV viral mRNA and/or genomic RNA have been tested here. In vitro translation experiments in reticulocyte lysates, in vitro transcription experiments with permeabilized viruses, measurement of viral RNA transcription and accumulation in VSV infected cells, and antiviral experiments demonstrate in our model that antisense oligomers probably also act at other levels. Difficulties in the choice of the most effective antisense oligomer targets are also discussed.

Intracellular distribution of microinjected antisense oligonucleotides.

Antisense oligomers constitute an attractive class of specific tools for genetic analysis and for potential therapeutic applications. Targets with different cellular locations have been described, such as mRNA translation initiation sites, pre-mRNA splicing sites, or the genes themselves. However the mechanism(s) of action and the intracellular distribution of antisense oligomers remain poorly understood. Antisense oligomers conjugated with various fluorochromes or with BrdUrd were microinjected into the cytoplasm of somatic cells, and their cellular distribution was monitored by fluorescence microscopy in fixed and nonfixed cells. A fast translocation in the nuclei and a concentration on nuclear structures were observed whatever probe was used. Nuclear transport occurs by diffusion since it is not affected by depletion of the intracellular ATP pool, temperature, or excess unlabeled oligomer. Accumulation of the oligomers in the nuclei essentially takes place on a set of proteins preferentially extracted between 0.2 M and 0.4 M NaCl as revealed by crosslinking of photosensitive oligomers. The relationship between nuclear location of antisense oligomers and their mechanism of action remains to be ascertained and could be of major interest in the design of more efficient antisense molecules.

alpha-DNA. VI: Comparative study of alpha- and beta-anomeric oligodeoxyribonucleotides in hybridization to mRNA and in cell free translation inhibition.

alpha and beta-anomeric d(G2T12G2) oligodeoxyribonucleotides were compared for their hybridization to rA12: the observed melting temperatures are 27 degrees C for beta-oligodeoxyribonucleotide/RNA hybrid and 53 degrees C for alpha-oligodeoxyribonucleotide/RNA. alpha-oligonucleotides with the four bases, complementary to natural mRNAs, were synthesized for the first time, labeled at their 5'-end with [32P] and used as probes in Northern blot experiments. In spite of these higher affinities for their target RNA's, they were unable to block translation of natural or synthetic mRNA's in rabbit reticulocyte lysate. We have studied the RNase H activity on model rA12:alpha- or beta-d(G2T12G2) hybrids or on mRNA:alpha- or beta-oligonucleotides hybrids. Specific hybridization protects RNA strech when using alpha-oligonucleotides but not beta-oligonucleotides. Thus, our results show the inability of RNase H to degrade RNA in alpha-oligodeoxyribonucleotides:RNA duplexes.