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Carol Crowther

Bio: Carol Crowther is an academic researcher from University of the Witwatersrand. The author has contributed to research in topics: RNA interference & Hepatitis B virus. The author has an hindex of 15, co-authored 22 publications receiving 877 citations. Previous affiliations of Carol Crowther include National Health Laboratory Service.

Papers
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Journal ArticleDOI
TL;DR: A new hepatotropic nontoxic lipid-based vector system that is used to deliver chemically unmodified small interfering RNA (siRNA) sequences to the liver and repeated systemic administration of triggered PEGylated siRNA-nanoparticles to HBV transgenic mice results in the suppression of markers of HBV replication by up to 3-fold relative to controls over a 28 day period.
Abstract: Harnessing RNA interference (RNAi) to inhibit hepatitis B virus (HBV) gene expression has promising application to therapy. Here we describe a new hepatotropic nontoxic lipid-based vector system that is used to deliver chemically unmodified small interfering RNA (siRNA) sequences to the liver. Anti HBV formulations were generated by condensation of siRNA (A component) with cationic liposomes (B component) to form AB core particles. These core particles incorporate an aminoxy cholesteryl lipid for convenient surface postcoupling of polyethylene glycol (PEG; C component, stealth/biocompatibility polymer) to give triggered PEGylated siRNA-nanoparticles (also known as siRNA-ABC nanoparticles) with uniform small sizes of 80-100 nm in diameter. The oxime linkage that results from PEG coupling is pH sensitive and was included to facilitate acidic pH-triggered release of nucleic acids from endosomes. Nanoparticle-mediated siRNA delivery results in HBV replication knockdown in cell culture and in murine hydrodynamic injection models in vivo. Furthermore repeated systemic administration of triggered PEGylated siRNA-nanoparticles to HBV transgenic mice results in the suppression of markers of HBV replication by up to 3-fold relative to controls over a 28 day period. This compares favorably to silencing effects seen during lamivudine treatment. Collectively these observations indicate that our PEGylated siRNA-nanoparticles may have valuable applications in RNAi-based HBV therapy.

118 citations

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TL;DR: Observations indicate that U6 shRNA 5 and U6ShRNAs 6 are promising candidates for therapy of chronic HBV infection.

113 citations

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TL;DR: An approach that allows the use of a Pol II promoter to improve transcription regulation of expressed RNAi effecters is reported, and Employing Pol II-expressed pri-miR mimics may be useful in the treatment of HBV infection, and potentially also for generic application in RNAi-based therapy.

105 citations

Journal ArticleDOI
TL;DR: It is observed that DODAG alone forms lipoplex nanoparticles with small interfering RNA (siRNA) that are able to mediate the functional delivery of two previously validated anti-hepatitis B virus (HBV)--siRNAs to murine liver in vivo with minimal observable liver toxicity and immune stimulation.

104 citations

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TL;DR: Investigating pediatric infection, where AIDS typically develops more rapidly than in adults, found low immune activation levels were low despite high viremia, suggesting closer similarities with nonpathogenetic mechanisms evolved over thousands of years in natural SIV hosts than those operating in HIV-infected adults.
Abstract: Disease-free infection in HIV-infected adults is associated with human leukocyte antigen-mediated suppression of viremia, whereas in the sooty mangabey and other healthy natural hosts of simian immunodeficiency virus (SIV), viral replication continues unabated. To better understand factors preventing HIV disease, we investigated pediatric infection, where AIDS typically develops more rapidly than in adults. Among 170 nonprogressing antiretroviral therapy-naive children aged >5 years maintaining normal-for-age CD4 T cell counts, immune activation levels were low despite high viremia (median, 26,000 copies/ml). Potent, broadly neutralizing antibody responses in most of the subjects and strong virus-specific T cell activity were present but did not drive pediatric nonprogression. However, reduced CCR5 expression and low HIV infection in long-lived central memory CD4 T cells were observed in pediatric nonprogressors. These children therefore express two cardinal immunological features of nonpathogenic SIV infection in sooty mangabeys-low immune activation despite high viremia and low CCR5 expression on long-lived central memory CD4 T cells-suggesting closer similarities with nonpathogenetic mechanisms evolved over thousands of years in natural SIV hosts than those operating in HIV-infected adults.

102 citations


Cited by
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Journal ArticleDOI
TL;DR: This Commentary focuses on novel strategies designed to enhance endosomal escape and thereby increase the efficacy of siRNA-mediated gene silencing.
Abstract: RNA interference (RNAi)-based technologies offer an attractive strategy for the sequence-specific silencing of disease-causing genes. The application of small interfering (si)RNAs as potential therapeutic agents requires safe and effective methods for their delivery to the cytoplasm of the target cells and tissues. Recent studies have shown significant progress in the development of targeting reagents that facilitate the recognition of and siRNA delivery to specific cell types. However, most of these delivery approaches are not optimized to enable the intracellular trafficking of the siRNAs into the cytoplasm where they must associate with the RNA-induced silencing complex (RISC) to direct the cleavage of mRNAs bearing complementary binding sites. In particular, the trafficking of siRNAs from endosomes into the cytoplasm represents a major rate-limiting step for many delivery approaches. This Commentary focuses on novel strategies designed to enhance endosomal escape and thereby increase the efficacy of siRNA-mediated gene silencing.

572 citations

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TL;DR: This review provides an overview of the theory and practice of hydrodynamic gene delivery so as to aid researchers for the use of this method in their pre-clinical and translational gene therapy studies.

363 citations

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TL;DR: The biology of the most abundant miRNA in human liver, miR-122, is reviewed, and the diversity of its roles in the liver is considered, and some possible therapeutic opportunities for exploiting miRNAs in the different settings of liver diseases are considered.

361 citations

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TL;DR: It is clear that developing novel multifunctional nonviral vectors, which transform their physico-chemical properties in response to various stimuli in a timely and spatially controlled manner, is highly desired to translate the promise of gene therapy for the clinical success.

350 citations

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TL;DR: Development of several types of chemical methods for gene transfer in vitro and in vivo by means of nano-carriers like; calcium phosphates, lipids, and cationic polymers including chitosan, polyethylenimine, polyamidoamine dendrimers, and poly(lactide-co-glycolide).
Abstract: Gene transfer methods are promising in the field of gene therapy. Current methods for gene transfer include three major groups: viral, physical and chemical methods. This review mainly summarizes development of several types of chemical methods for gene transfer in vitro and in vivo by means of nano-carriers like; calcium phosphates, lipids, and cationic polymers including chitosan, polyethylenimine, polyamidoamine dendrimers, and poly(lactide-co-glycolide). This review also briefly introduces applications of these chemical methods for gene delivery.

330 citations