Mechanism for enhanced transduction of hematopoietic cells by recombinant adeno-associated virus serotype 6 vectors

Reactive oxygen species enhance rAAV transduction by promoting its escape from late endosomes

BACKGROUND

Recent seminal studies have revealed that endosomal reactive oxygen species (ROS) promote rather than inhibit viral infection. Some ROS generators, including shikonin and H₂O₂, have the potential to enhance recombinant adeno-associated virus (rAAV) transduction. However, the impact of ROS on rAAV intracellular trafficking remains unclear.

METHODS

To understand the effects of ROS on the transduction of rAAV vectors, especially the rAAV subcellular distribution profiles, this study systematically explored the effect of ROS on each step of rAAV intracellular trafficking pathway using fluorescently-labeled rAAV and qPCR quantification determination.

RESULTS

The results showed promoted in-vivo and in-vitro rAAV transduction by ROS exposure, regardless of vector serotype or cell type. ROS treatment directed rAAV intracellular trafficking towards a more productive pathway by upregulating the expression of cathepsins B and L, accelerating the rAAV transit in late endosomes, and increasing the rAAV nucleus entry.

CONCLUSIONS

These data support that ROS generative drugs, such as shikonin, have the potential to promote rAAV vector transduction by promoting rAAV's escape from late endosomes, and enhancing its productive trafficking to the nucleus.

Shikonin, a naphthalene ingredient: Therapeutic actions, pharmacokinetics, toxicology, clinical trials and pharmaceutical researches

BACKGROUND

Shikonin is one of the major phytochemical components of Lithospermum erythrorhizon (Purple Cromwell), which is a type of medicinal herb broadly utilized in traditional Chinese medicine. It is well established that shikonin possesses remarkable therapeutic actions on various diseases, with the underlying mechanisms, pharmacokinetics and toxicological effects elusive. Also, the clinical trial and pharmaceutical study of shikonin remain to be comprehensively delineated.

PURPOSE

The present review aimed to systematically summarize the updated knowledge regarding the therapeutic actions, pharmacokinetics, toxicological effects, clinical trial and pharmaceutical study of shikonin.

METHODS

The information contained in this review article were retrieved from some authoritative databases including Web of Science, PubMed, Google scholar, Chinese National Knowledge Infrastructure (CNKI), Wanfang Database and so on, till August 2021.

RESULTS

Shikonin exerts multiple therapeutic efficacies, such as anti-inflammation, anti-cancer, cardiovascular protection, anti-microbiomes, analgesia, anti-obesity, brain protection, and so on, mainly by regulating the NF-κB, PI3K/Akt/MAPKs, Akt/mTOR, TGF-β, GSK3β, TLR4/Akt signaling pathways, NLRP3 inflammasome, reactive oxygen stress, Bax/Bcl-2, etc. In terms of pharmacokinetics, shikonin has an unfavorable oral bioavailability, 64.6% of the binding rate of plasma protein, and enhances some metabolic enzymes, particularly including cytochrome P450. In regard to the toxicological effects, shikonin may potentially cause nephrotoxicity and skin allergy. The above pharmacodynamics and pharmacokinetics of shikonin have been validated by few clinical trials. In addition, pharmaceutical innovation of shikonin with novel drug delivery system such as nanoparticles, liposomes, microemulsions, nanogel, cyclodextrin complexes, micelles and polymers are beneficial to the development of shikonin-based drugs.

CONCLUSIONS

Shikonin is a promising phytochemical for drug candidates. Extensive and intensive explorations on shikonin are warranted to expedite the utilization of shikonin-based drugs in the clinical setting.

Low endotoxin E. coli strain-derived plasmids reduce rAAV vector-mediated immune responses both in vitro and in vivo

The major challenge of recombinant adeno-associated virus (rAAV) vectors is host immunological barriers. Compared to the neutralizing antibody and the cytotoxic T lymphocyte response, the host immune responses induced by unsatisfactory rAAV manufacturing were largely ignored previously. rAAV vector production usually requires large amounts of plasmid DNAs. The DNA are commonly isolated from the DH5α bacterial strain, which contains lipopolysaccharide (LPS) contamination. LPS, also named endotoxin, in plasmid DNA is intractable, and residual endotoxin in the subsequent rAAV vectors may result in substantial host immune response. Recently, a ClearColi K12 bacterial strain is commercially available, with genetically modified LPS that does not trigger endotoxic response in mammalian cells. Here, we produced rAAV-DJ vectors by plasmids yielded from either DH5α or ClearColi K12 bacterial strains. Our data indicated that the ClearColi K12 strain had satisfactory protection for the rAAV inverted terminal repeat (ITR) sequence. As expected, the ClearColi K12-derived rAAV-DJ vectors had lower endotoxin levels. The physical and biological equivalency of the purified viral stocks were confirmed by electron micrographs, Coomassie blue staining, and transduction assays. Most importantly, the ClearColi K12-derived rAAV-DJ vectors triggered reduced nuclear factor-kappa B (NF-κB) signaling pathway both in cell cultures in vitro and in C57BL/6 mice retinas in vivo. We believe that the use of the ClearColi K12 bacterial strain could eliminate the LPS in the purified vector stock at the source. Our data indicate its promising use in future clinical development.