Society learned about the value of mRNA during the Covid-19 pandemic when scientists and medical professionals harnessed its power to deliver a vaccine for the virus within a year – and now scientists are using small RNAs they believe might offer hope in the fight against HIV.
University of Waterloo pharmacy associate professor Emmanuel Ho has developed a novel nano-medicine loaded with genetic material called small interfering RNAs (siRNA) to fight human immunodeficiency virus (HIV) using gene therapy. These siRNAs regulate which genes or proteins are turned on or off in our cells and showed a 73% reduction in HIV replication.
“This opens the door for new therapeutics in the fight against HIV,” said Ho, who is among Waterloo’s researchers and entrepreneurs leading health innovation in Canada.
Autophagy, also known as the body’s recycling process, plays an important role in our body to eliminate microbes like viruses and bacteria inside cells. HIV is quite smart and produces a protein, Nef, that prevents cells from activating autophagy.
News-Medical.Net reports that this is the first research to develop a combination nanomedicine that can reactivate autophagy and prevent HIV entry into cells, allowing our body to re-initiate its defence system.
Additionally, HIV has a gene, CCR5, that allows the virus to enter a cell. The siRNAs target both Nef and CCR5 to reduce HIV infection.
This nanomedicine is intended to be applied vaginally to protect against sexual transmission of HIV: it is designed to be stable without leakage of siRNAs in the acidic vaginal environment but release the siRNA once inside cells.
“Viruses are smart. They produce Nef proteins to prevent autophagy from occurring.Our process allows our body to fight the viral infection without needing additional drugs,” Ho said.
He added that the next steps include further optimising the process and improving understanding of how autophagy plays a role in how our cells protect us from viruses.
“We also hope this will shed some light to develop more alternative approaches to effectively reduce antimicrobial resistance,” he said.
The research was published in Journal of Controlled Release.
Study details
pH-sensitive dual-preventive siRNA-based nanomicrobicide reactivates autophagy and inhibits HIV infection in vaginal CD4+ cells
Sidi Yang, Yufei Chen, Jijin Gu, Angela Harris, Ruey-Chyi Su, Emmanuel Ho.
Published in Journal of Controlled Release in February 2024
Abstract
Women are more susceptible to HIV transmission through unprotected heterosexual intercourse due to biological and social vulnerabilities. Intravaginal delivery of siRNAs targeting viral genes, host genes, or in combination has shown promising outcomes against HSV, HPV and HIV. Therefore, in this study, we designed, developed and evaluated a pH-sensitive RNAi-based combination nanomicrobide for the prevention/reduction of vaginal transmission of HIV. The nanomicrobide was composed of siRNA-PEI encapsulated PLGA-PEG nanoparticles (siRNA NP) loaded in a HEC gel dosage form with siRNA targeting host gene CCR5 and the viral gene Nef as a dual preventive strategy. Knocking down CCR5, a co-receptor for HIV could prevent HIV from attaching to and entering host cells and knocking down Nef could reactivate autophagy that was inhibited by Nef to improve the elimination of intracellular virus that escaped the first line of defence. The siRNA NP showed a desirable particle size and zeta potential for intravaginal delivery and a pH-dependent release profile whereby low amounts of siRNA was released under acidic vaginal conditions (vaginal fluid simulant; VFS, pH 4.2) (6.0 ± 0.4% released over 15 days) but significantly higher amounts of siRNA was released under neutral pH conditions (phosphate buffered saline; PBS, pH 7.4) (22.9 ± 0.4% released over 15 days). The CCR5-Nef-specific siRNA NP efficiently knocked down CCR5 and Nef protein expression by 43% and 63%, respectively, reactivated Nef-blocked autophagy and inhibited the replication of HIV in vitro (71.8% reduction in p24 expression). After being formulated into a gel dosage form, siRNA NP could be readily released from the gel, penetrate the vaginal epithelial layer, get taken up into the target cells and knockdown Nef and CCR5 without causing cytotoxicity in a vaginal mucosal co-culture model. Functionalisation of siRNA NP with anti-CD4 antibody and loaded into a 0.5% HEC gel improved vaginal distribution and uptake of siRNA in a mouse model with distribution of siRNA restricted to the reproductive tract without any unwanted systemic uptake. The 0.5% HEC gel loaded with siRNA NP-(m)CD4 significantly down-regulated approximately 40% of CCR5 protein in the lower vagina and 36% of CCR5 protein in the upper vaginal and cervical region. In contrast, 0.5% HEC gel loaded with siRNA NP-IgG did not result in significant gene knockdown.
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