Durable Knockdown and Protection From HIV Transmission in Humanized Mice Treated With Gel-formulated CD4 Aptamer-siRNA Chimeras

Abstract

The continued spread of HIV underscores the need to interrupt transmission. One attractive strategy, in the absence of an effective vaccine, is a topical microbicide, but the need for application around the time of sexual intercourse leads to poor patient compliance. Intravaginal (IVAG) application of CD4 aptamer-siRNA chimeras (CD4-AsiCs) targeting the HIV coreceptor CCR5, gag, and vif protected humanized mice from sexual transmission. In non-dividing cells and tissue, RNAi-mediated gene knockdown lasts for several weeks, providing an opportunity for infrequent dosing not temporally linked to sexual intercourse, when compliance is challenging. Here, we investigate the durability of gene knockdown and viral inhibition, protection afforded by CCR5 or HIV gene knockdown on their own, and effectiveness of CD4-AsiCs formulated in a gel in polarized human cervicovaginal explants and in humanized mice. CD4-AsiC-mediated gene knockdown persisted for several weeks. Cell-specific gene knockdown and protection were comparable in a hydroxyethylcellulose gel formulation. CD4-AsiCs against CCR5 or gag/vif performed as well as a cocktail in humanized mice. Transmission was completely blocked by CCR5 CD4-AsiCs applied 2 days before challenge. Significant, but incomplete, protection also occurred when exposure was delayed for 4 or 6 days. CD4-AsiCs targeting gag/vif provided some protection when administered only after exposure. These data suggest that CD4-AsiCs are a promising approach for developing an HIV microbicide.

Gene Knockdown by EpCAM Aptamer–siRNA Chimeras Suppresses Epithelial Breast Cancers and Their Tumor-Initiating Cells

“…Despite their promise, there is still considerable room to improve AsiCs, to optimize circulating t 1/2 , cellular uptake, and endosomal release and to reduce the needed dose (although it is currently acceptable: approximately 1-5 mg/kg; refs. 11,13,15,18). Recent studies have shown that the efficiency of GalNac-conjugated siRNAs in nonhuman primates can be improved by as much as 50-fold by optimizing the chemical modifications of the active strand to enhance stability and activity within the RNA-induced silencing complex (M. Manoharan, personal communication).…”

“…We deliver siRNAs into epithelial cancer cells by linking them to an RNA aptamer that binds to EpCAM, the first described tumor antigen, a cell surface receptor overexpressed on epithelial cancers, including basal-like TNBCs. Aptamer-linked siRNAs, known as aptamer-siRNA chimeras (AsiC), have been used in small animal models to treat prostate cancer and prevent HIV infection (10)(11)(12)(13)(14)(15)(16)(17)(18). We chose EpCAM for targeting basal-like TNBC because EpCAM is highly expressed on all epithelial cancers.…”

Targeted Delivery of Aptamers and siRNAs for HIV Prevention and Therapies in Humanized Mice

“…Using the NSG mouse, recent studies of Wheeler et al employed CD4 aptamers conjugated to siRNAs targeted to host cell and viral transcripts addressing prevention strategies [41,47]. It was shown that CD4 aptamer-CCR5, HIV vif, and gag siRNA conjugates were specifically taken up by CD4 + T cells and macrophages leading to HIV suppression in vitro.…”

CD4 aptamer–RORγt shRNA chimera inhibits IL-17 synthesis by human CD4+ T cells

“…Zhou et al [13] modified the aptamer-siRNA chimera with aptamer specific to HIV envelope protein expressed by viral infected T cells and siRNA to viral genes and successfully suppressed HIV replication in HIV infected human CD4 + T cells. Wheeler et al [14,15] developed a CD4 aptamer-siRNA chimera that targeted CCR5, gag and vif and delivered to infected human CD4 + T cells and suppressed the targeted gene expression and killed HIV.…”