Specific inhibition of human immunodeficiency virus type 1 replication by antisense oligonucleotides: an in vitro model for treatment.

We have developed a culture system, simulating in vivo conditions of human immunodeficiency virus type 1 (HIV-1) infection, to evaluate the long-term efficacy of antisense oligonucleotide treatment. Five oligonucleotide phosphorothioates (28-mers), complementary to different regions of HIV-1 RNA, blocked replication of the virus in a sequence-specific manner at 1 microM concentration. Variations in antiviral activity were seen among the different oligonucleotides, revealing an effect of target selection. Mismatched or random oligonucleotide phosphorothioates delayed, but did not completely inhibit, HIV-1 replication. In the case of inhibition by a splice-acceptor-site antisense oligodeoxynucleotide, a break-through phenomenon occurred after 25 days of treatment, suggesting the development of an "escape mutant." This result did not occur when the inhibitory oligodeoxynucleotides were complementary to the primary-sequence areas of the rev-responsive element and rev-1 genes. Sequential treatment of HIV-1-infected cells with a combination of different antisense oligonucleotides, each administered once, also prevented the development of escape mutants. Our results suggest that chemotherapy based on specifically targeted antisense-oligonucleotide phosphorothioates may be an effective method for reducing the viral burden in HIV-1-infected individuals at clinically achievable oligonucleotide concentrations.