A p21 reporter iPSC line for evaluating CRISPR-Cas9 and vector-induced stress responses.

CRISPR-Cas9 editing triggers activation of the TP53-p21 pathway, but the impacts of different editing components and delivery methods have not been fully explored. In this study, we introduce a p21-mNeonGreen reporter iPSC line to monitor TP53-p21 pathway activation. This reporter enables dynamic tracking of p21 expression via flow cytometry, revealing a strong correlation between p21 expression and indel frequencies, and highlighting its utility in guide RNA screening. Our findings show that p21 activation is significantly more pronounced with double-stranded oligodeoxynucleotides (ODNs) or adeno-associated viral vectors (AAVs) compared to their single-stranded counterparts. Lentiviral vectors (LVs) and integrase-defective lentiviral vectors induce notably lower p21 expression than AAVs, suggesting their suitability for gene therapy in sensitive cells such as hematopoietic stem cells or immune cells. Additionally, specific viral promoters like SFFV significantly amplify p21 activation, emphasizing the critical role of promoter selection in vector development. Thus, the p21-mNeonGreen reporter iPSC line is a valuable tool for assessing the potential adverse effects of gene editing methodologies and vectors. Highlights Established a p21-mNeonGreen reporter iPSC line to track activation of the TP53-p21 pathway. Found a direct correlation between p21-mNeonGreen expression and indel frequencies, aiding in gRNA screening. Showed that LVs are preferable over AAVs for certain cells due to lower p21 activation, with viral promoter choice impacting p21 response.

Gene therapy for Lafora disease in the Epm2a-/- mouse model.

Lafora disease is a rare and fatal form of progressive myoclonic epilepsy typically occurring early in adolescence. The disease results from mutations in the EPM2A gene, encoding laforin, or the EPM2B gene, encoding malin. Laforin and malin work together in a complex to control glycogen synthesis and prevent the toxicity produced by misfolded proteins via the ubiquitin-proteasome system. Disruptions in either protein cause alterations in this complex, leading to the formation of Lafora bodies containing abnormal, insoluble, and hyperphosphorylated forms of glycogen. We used the Epm2a-/- knockout mouse model of Lafora disease to apply gene therapy by administering intracerebroventricular injections of a recombinant adeno-associated virus carrying the human EPM2A gene. We evaluated the effects of this treatment through neuropathological studies, behavioral tests, video-electroencephalography, electrophysiological recordings, and proteomic/phosphoproteomic analysis. Gene therapy ameliorated neurological and histopathological alterations, reduced epileptic activity and neuronal hyperexcitability, and decreased the formation of Lafora bodies. Moreover, differential quantitative proteomics and phosphoproteomics revealed beneficial changes in various molecular pathways altered in Lafora disease. Our results represent proof of principle for gene therapy with the coding region of the human EPM2A gene as a treatment for EPM2A-related Lafora disease.

Cardiac-specific PFKFB3 overexpression prevents diabetic cardiomyopathy via enhancing OPA1 stabilization mediated by K6-linked ubiquitination.

Diabetic cardiomyopathy (DCM) is a prevalent complication of type 2 diabetes (T2D). 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) is a glycolysis regulator. However, the potential effects of PFKFB3 in the DCM remain unclear. In comparison to db/m mice, PFKFB3 levels decreased in the hearts of db/db mice. Cardiac-specific PFKFB3 overexpression inhibited myocardial oxidative stress and cardiomyocyte apoptosis, suppressed mitochondrial fragmentation, and partly restored mitochondrial function in db/db mice. Moreover, PFKFB3 overexpression stimulated glycolysis. Interestingly, based on the inhibition of glycolysis, PFKFB3 overexpression still suppressed oxidative stress and apoptosis of cardiomyocytes in vitro, which indicated that PFKFB3 overexpression could alleviate DCM independent of glycolysis. Using mass spectrometry combined with co-immunoprecipitation, we identified optic atrophy 1 (OPA1) interacting with PFKFB3. In db/db mice, the knockdown of OPA1 receded the effects of PFKFB3 overexpression in alleviating cardiac remodeling and dysfunction. Mechanistically, PFKFB3 stabilized OPA1 expression by promoting E3 ligase NEDD4L-mediated atypical K6-linked polyubiquitination and thus prevented the degradation of OPA1 by the proteasomal pathway. Our study indicates that PFKFB3/OPA1 could be potential therapeutic targets for DCM.

Identification of host essential factors for recombinant AAV transduction of the polarized human airway epithelium.

IMPORTANCE: The essential steps of successful gene delivery by recombinant adeno-associated viruses (rAAVs) include vector internalization, intracellular trafficking, nuclear import, uncoating, double-stranded (ds)DNA conversion, and transgene expression. rAAV2.5T has a chimeric capsid of AAV2 VP1u and AAV5 VP2 and VP3 with the mutation A581T. Our investigation revealed that KIAA0319L, the multiple AAV serotype receptor, is not essential for vector internalization but remains critical for efficient vector transduction to human airway epithelia. Additionally, we identified that a novel gene WDR63, whose cellular function is not well understood, plays an important role in vector transduction of human airway epithelia but not vector internalization and nuclear entry. Our study also discovered the substantial transduction potential of rAAV2.5T in basal stem cells of human airway epithelia, underscoring its utility in gene editing of human airways. Thus, the knowledge derived from this study holds promise for the advancement of gene therapy in the treatment of pulmonary genetic diseases.

rAAV-compatible human mini promoters enhance transgene expression in rat retinal ganglion cells.

Recombinant adeno-associated viral vectors (rAAV) are the safest and most effective gene delivery platform to drive the treatment of many inherited eye disorders in well-characterized animal models. The use in rAAV of ubiquitous promoters derived from viral sequences such as CMV/CBA (chicken ß-actin promoter with cytomegalovirus enhancer) can lead to unwanted side effects such as pro-inflammatory immune responses and retinal cytotoxicity, thus reducing therapy efficacy. Thus, an advance in gene therapy is the availability of small promoters, that potentiate and direct gene expression to the cell type of interest, with higher safety and efficacy. In this study, we used six human mini-promoters packaged in rAAV2 quadruple mutant (Y-F) to test for transduction of the rat retina after intravitreal injection. After four weeks, immunohistochemical analysis detected GFP-labeled cells in the ganglion cell layer (GCL) for all constructs tested. Among them, Ple25sh1, Ple25sh2 and Ple53 promoted a widespread reporter-transgene expression in the GCL, with an increased number of GFP-expressing retinal ganglion cells when compared with the CMV/CBA vector. Moreover, Ple53 provided the strongest levels of GFP fluorescence in both cell soma and axons of retinal ganglion cells (RGCs) without any detectable adverse effects in retina function. Remarkably, a nearly 50-fold reduction in the number of intravitreally injected vector particles containing Ple53 promoter, still attained levels of transgene expression similar to CMV/CBA. Thus, the tested MiniPs show great potential for protocols of retinal gene therapy in therapeutic applications for retinal degenerations, especially those involving RGC-related disorders such as glaucoma.

Recent advances in upstream process development for production of recombinant adeno-associated virus.

Recombinant adeno-associated virus (rAAV) is rapidly emerging as the preferred delivery vehicle for gene therapies, with promising advantages in safety and efficacy. Key challenges in systemic in-vivo rAAV gene therapy applications are the gap in production capabilities versus potential market demand and complex production process. This review summarizes current available information on rAAV upstream manufacturing processes and proposed optimizations for production. The advancements in rAAV production media were reviewed with proposals to speed up the cell culture process development. Furthermore, major methods for genetic element delivery to host cells were summarized with their advantages, limitations, and future directions for optimization. In addition, culture vessel selection criteria were listed based on production cell system, scale, and development stage. Process control at the production step was also outlined with an in-depth understanding of production kinetics and quality control.

Recombinant adeno-associated virus production evaluation in Chinese hamster ovary cells.

The gene therapy field has advanced in recent years with five recombinant adeno-associated virus (rAAV) based products winning Food and Drug Administration (FDA) approval. As the number of therapeutic applications and overall production demands for rAAV increase, it is valuable to evaluate rAAV production in different production cells. Chinese hamster ovary (CHO) cells have been a robust host for biomolecule manufacturing for more than 35 years. However, there is no report to our knowledge describing the use of CHO cells for rAAV production. In this study, we examined the ability of CHO cells to produce rAAV using a transient plasmid transfection approach. Our results demonstrated that CHO is capable of producing rAAV with detectable viral fundamental components including viral RNAs, proteins, and rAAV viral particles. We identified the expression of cap proteins as one of the limiting factors for rAAV production in CHO cells. We therefore added an additional cytomegalovirus (CMV)-Cap plasmid to the CHO transfection. After increasing cap protein expression, we detected rAAV titers as high as 3 × 108 viral genomes for every 2 × 109 capsids in CHO cells using a quintuple transfection method (standard AAV2 Rep/Cap, helper, gene of interest plasmids, plus CMV-E1, and CMV-Cap plasmids) with comparable full particle percent (average 15%) to that of human embryo kidney (HEK)-derived rAAV. Our study provides a foundation for potential rAAV production in CHO cells.

Commitment of human mesenchymal stromal cells towards ACL fibroblast differentiation upon rAAV-mediated FGF-2 and TGF-ß overexpression using pNaSS-grafted PCL films.

Despite various clinical options, human anterior cruciate ligament (ACL) lesions do not fully heal. Biomaterial-guided gene therapy using recombinant adeno-associated virus (rAAV) vectors may improve the intrinsic mechanisms of ACL repair. Here, we examined whether poly(sodium styrene sulfonate)-grafted poly(ε-caprolactone) (pNaSS-grafted PCL) films can deliver rAAV vectors coding for the reparative basic fibroblast growth factor (FGF-2) and transforming growth factor beta (TGF-ß) in human mesenchymal stromal cells (hMSCs) as a source of implantable cells in ACL lesions. Efficient and sustained rAAV-mediated reporter (red fluorescent protein) and therapeutic (FGF-2 and TGF-ß) gene overexpression was achieved in the cells for at least 21 days in particular with pNaSS-grafted PCL films relative to all other conditions (up to 5.2-fold difference). Expression of FGF-2 and TGF-ß mediated by rAAV using PCL films increased the levels of cell proliferation, the DNA contents, and the deposition of proteoglycans and of type-I and -III collagen (up to 2.9-fold difference) over time in the cells with higher levels of transcription factor expression (Mohawk, Scleraxis) (up to 1.9-fold difference), without activation of inflammatory tumor necrosis alpha especially when using pNaSS-grafted PCL films compared with the controls. Overall, the effects mediated by TGF-ß were higher than those promoted by FGF-2, possibly due to higher levels of gene expression achieved upon rAAV gene transfer. This study shows the potential of using functionalized PCL films to apply rAAV vectors for ACL repair.

Comparative transcriptomic and proteomic kinetic analysis of adeno-associated virus production systems.

Recombinant adeno-associated virus (rAAV) is a major gene delivery vehicle. We have constructed a stable rAAV producer cell line by integrating essential rAAV genome, viral and helper genes into the genome of HEK293 cell under the control of inducible promoters. Upon induction, the cell line produces transducing rAAV. To gain insight into enhancing rAAV productivity and vector quality, we performed a comparative transcriptomic and proteomic analysis of our synthetic cell line GX2 and two wild-type AAV (wtAAV) production systems, one by virus co-infection and the other by multi-plasmid transfection. The three systems had different kinetics in viral component synthesis but generated comparable copies of AAV genomes; however, the capsid titer of GX2 was an order of magnitude lower compared to those two wtAAV systems, indicating that its capsid production may be insufficient. The genome packaging efficiency was also lower in GX2 despite it produced higher levels of Rep52 proteins than either wtAAV systems, suggesting that Rep52 protein expression may not limit genome packaging. In the two wtAAV systems, VP were the most abundant AAV proteins and their levels continued to increase, while GX2 had high level of wasteful cargo gene expression. Furthermore, upregulated inflammation, innate immune responses, and MAPK signaling, as well as downregulated mitochondrial functions, were commonly observed in either rAAV or wtAAV systems. Overall, this comparative multi-omics study provided rich insights into host cell and viral factors that are potential targets for genetic and process intervention to enhance the productivity of synthetic rAAV producer cell lines. KEY POINTS: • wtAAV infection was more efficient in producing full viral particles than the synthetic cell GX2. • Capsid protein synthesis, genome replication, and packaging may limit rAAV production in GX2. • wtAAV infection and rAAV production in GX2 elicited similar host cell responses.

Stowaways in the cargo: Contaminating nucleic acids in rAAV preparations for gene therapy.

Recombinant AAV (rAAV) is the most used delivery vector for clinical gene therapy. However, many issues must be addressed before safer and more widespread implementation can be achieved. At present, efficacies are highly variable across trials and patients, and immune responses after treatment are widely reported. Although rAAV is capable of directly delivering gene-encoded therapeutic sequences, increased scrutiny of viral preparations for translational use have revealed contaminating nucleic acid species packaged within rAAV preparations. The introduction of non-therapeutic nucleic acids into a recipient patient adds to the risk burden, immunogenic or otherwise, of rAAV therapies. DNA from incomplete expression cassettes, portions of plasmids or vectors used to facilitate viral replication, and production cell line genomes all have the potential to be packaged within rAAV. Here, we review what is currently known about the profile, abundance, and post-treatment consequences of nucleic acid impurities within rAAV and cover strategies that have been developed to improve rAAV purity. Furthering our understanding of these aberrantly packaged DNA species will help to ensure the continued safe implementation of rAAV therapies as the number of patients treated with this modality increases.

WNT-modulating gene silencers as a gene therapy for osteoporosis, bone fracture, and critical-sized bone defects.

Treating osteoporosis and associated bone fractures remains challenging for drug development in part due to potential off-target side effects and the requirement for long-term treatment. Here, we identify recombinant adeno-associated virus (rAAV)-mediated gene therapy as a complementary approach to existing osteoporosis therapies, offering long-lasting targeting of multiple targets and/or previously undruggable intracellular non-enzymatic targets. Treatment with a bone-targeted rAAV carrying artificial microRNAs (miRNAs) silenced the expression of WNT antagonists, schnurri-3 (SHN3), and sclerostin (SOST), and enhanced WNT/ß-catenin signaling, osteoblast function, and bone formation. A single systemic administration of rAAVs effectively reversed bone loss in both postmenopausal and senile osteoporosis. Moreover, the healing of bone fracture and critical-sized bone defects was also markedly improved by systemic injection or transplantation of AAV-bound allograft bone to the osteotomy sites. Collectively, our data demonstrate the clinical potential of bone-specific gene silencers to treat skeletal disorders of low bone mass and impaired fracture repair.

Enhanced ER protein processing gene expression increases rAAV yield and full capsid ratio in HEK293 cells.

The recombinant adeno-associated virus (rAAV) vector is among the most promising viral vectors in gene therapy. However, the limited manufacturing capacity in human embryonic kidney (HEK) cells is a barrier to rAAV commercialization. We investigated the impact of endoplasmic reticulum (ER) protein processing and apoptotic genes on transient rAAV production in HEK293 cells. We selected four candidate genes based on prior transcriptomic studies: XBP1, GADD34 / PPP1R15A, HSPA6, and BCL2. These genes were stably integrated into HEK293 host cells. Traditional triple-plasmid transient transfection was used to assess the vector production capability and the quality of both the overexpressed stable pools and the parental cells. We show that the overexpression of XBP1, HSPA6, and GADD34 increases rAAV productivity by up to 100% and increases specific rAAV productivity by up to 78% in HEK293T cells. Additionally, more prominent improvement associated with ER protein processing gene overexpression was observed when parental cell productivity was high, but no substantial variation was detected under low-producing conditions. We also confirmed genome titer improvement across different serotypes (AAV2 and AAV8) and different cell lines (HEK293T and HEK293); however, the extent of improvement may vary. This study unveiled the importance of ER protein processing pathways in viral particle synthesis, capsid assembly, and vector production. KEY POINTS: • Upregulation of endoplasmic reticulum (ER) protein processing (XBP1, HSPA6, and GADD34) leads to a maximum 100% increase in rAAV productivity and a maximum 78% boost in specific rAAV productivity in HEK293T cells • The enhancement in productivity can be validated across different HEK293 cell lines and can be used for the production of various AAV serotypes, although the extent of the enhancement might vary slightly • The more pronounced improvements linked to overexpressing ER protein processing genes were observed when parental cell productivity was high, with minimal variation noted under low-producing conditions.

Factors affecting rAAV titers during triple-plasmid transient transfection in HEK-293 cells.

The efficiency of triple-plasmid transfection in recombinant Adeno-Associated Virus (rAAV) production was analyzed by examining two distinct HEK-293 cells lines. These were categorized as high producer (HP) and low producer (LP) based on their differing levels of productivity under identical conditions. Analysis of RNA expression levels of viral genes revealed disparities in plasmid derived gene expression between the cell lines. Further assessment of transfection efficiency utilizing labeled plasmids revealed lower plasmid uptake and less efficient nuclear transport in LP cell line. Additionally, we observed inferior translation activity in LP, contributing to its shortcomings in overall productivity. In our attempt to optimize plasmid ratios to enhance fully packaged rAAV particle yield, we discovered cell-line-specific optimization potential. The findings highlight the transfection's complexity, urging tailored strategies for improved rAAV production based on each cell line's characteristics, enhancing understanding and guiding further efficiency optimization in rAAV production.

Assessment of Key Factors Impacting Variability in AAV Vector Genome Titration by Digital PCR.

Recombinant adeno-associated virus (rAAV) has emerged as a prominent vector for in vivo gene therapy, owing to its distinct advantages. Accurate determination of the rAAV genome titer is crucial for ensuring the safe and effective administration of clinical doses. The evolution of the rAAV genome titer assay from quantitative PCR (qPCR) to digital PCR (dPCR) has enhanced accuracy and precision, yet practical challenges persist. This study systematically investigated the impact of various operational factors on genome titration in a single-factor manner, aiming to address potential sources of variability in the quantitative determination process. Our findings revealed that a pretreatment procedure without genome extraction exhibits superior precision compared with titration with genome extraction. Additionally, notable variations in titration results across different brands of dPCR instruments were documented, with relative standard deviation (RSD) reaching 23.47% for AAV5 and 11.57% for AAV8. Notably, optimal operations about DNase I digestion were identified; we thought treatment time exceeding 30 min was necessary, and there was no need for thermal inactivation after digestion. And we highlighted that thermal capsid disruption before serial dilution substantially affected AAV genome titers, causing a greater than ten-fold decrease. Conversely, this study found that additive components of dilution buffer are not significant contributors to titration variations. Furthermore, we found that repeated freeze-thaw cycles significantly compromised AAV genome titers. In conclusion, a comprehensive dPCR titration protocol, incorporating insights from these impact factors, was proposed and successfully tested across multiple serotypes of AAV. The results demonstrate acceptable variations, with the RSD consistently below 5.00% for all tested AAV samples. This study provides valuable insights to reduce variability and improve the reproducibility of AAV genome titration using dPCR.

MiR133b-mediated inhibition of EGFR-PTK pathway promotes rAAV2 transduction by facilitating intracellular trafficking and augmenting second-strand synthesis.

Recombinant adeno-associated virus (rAAV) is an extremely attractive vector in the in vivo delivery of gene therapy as it is safe and its genome is simple. However, challenges including low permissiveness to specific cells and restricted tissue specificity have hindered its clinical application. Based on the previous studies, epidermal growth factor receptor-protein tyrosine kinase (EGFR-PTK) negatively regulated rAAV transduction, and EGFR-positive cells were hardly permissive to rAAV transduction. We constructed a novel rAAV-miRNA133b vector, which co-expressed miRNA133b and transgene, and investigated its in vivo and in vitro transduction efficiency. Confocal microscopy, live-cell imaging, pharmacological reagents and labelled virion tracking were used to analyse the effect of miRNA133b on rAAV2 transduction and the underlying mechanisms. The results demonstrated that miRNA133b could promote rAAV2 transduction and the effects were limited to EGFR-positive cells. The increased transduction was found to be a direct result of decreased rAAV particles degradation in the cytoplasm and enhanced second-strand synthesis. ss-rAAV2-miRNA133b vector specifically increased rAAV2 transduction in EGFR-positive cells or tissues, while ss-rAAV2-Fluc-miRNA133b exerted an antitumor effect. rAAV-miRNA133b vector might emerge as a promising platform for delivering various transgene to treat EGFR-positive cell-related diseases, such as non-small-cell lung cancer.

Hyperthermia Enhances Adeno-Associated Virus Vector Transduction Efficiency in Melanoma Cells.

Gene therapy perfectly fits in the current needs of medicine for patients with melanoma. One of the major challenges of gene therapy is to increase gene transfer. The role of hyperthermia in the improvement of AAV (adeno-associated virus) transduction efficiency has been indicated. The aim of the present study was to assess the transduction efficacy of melanoma cell lines (A375, G-361, and SK-MEL-1) with the use of the rAAV/DJ mosaic vector under hyperthermia conditions. The analysis of changes in the transduction efficacy and expression of HSPs (heat shock proteins) and receptors for AAV was performed. The transduction was performed at 37 °C and at 43 °C (1 h). Hyperthermia enhanced gene transfer in all the tested cell lines. The most efficient transducing cell line under hyperthermia was A375 (increase by 17%). G361 and SK-MEL-1 cells showed an increase of 7%. The changes in the expression of the AAV receptors and HSPs after hyperthermia were observed. A key role in the improvement of gene transfer may be played by AAVR, HSPB1, HSP6, DNAJC4, HSPD1, HSPA8, HSPA9, HSP90AB1, and AHSA1. This study showed the possibility of the use of hyperthermia as a factor enabling the stimulation of cell transduction with rAAV vectors, thereby providing tools for the improvement in the efficacy of gene therapy based on rAAV.

Cryptic resolution sites in the vector plasmid lead to the heterogeneities in the rAAV vectors.

Recombinant adeno-associated virus (rAAV) vectors carry a cassette of interest retaining only the inverted terminal repeats (ITRs) from the wild-type virus. Conventional rAAV production primarily uses a vector plasmid as well as helper genes essential for AAV replication and packaging. Nevertheless, plasmid backbone related contaminants have been a major source of vector heterogeneity. The mechanism driving the contamination phenomenon has yet to be elucidated. Here we identified cryptic resolution sites in the plasmid backbone as a key source for producing snapback genomes, which leads to the increase of vector genome heterogeneity in encapsidated virions. By using a single ITR plasmid as a model molecule and mapping subgenomic particles, we found that there exist a few typical DNA break hotspots in the vector DNA plasmid backbone, for example, on the ampicillin DNA element, called aberrant rescue sites. DNA around these specific breakage sites may assume some typical secondary structures. Similar to normal AAV vectors, plasmid DNA with a single ITR was able to rescue and replicate efficiently. These subgenomic DNA species significantly compete for trans factors required for rAAV rescue, replication, and packaging. The replication of single ITR contaminants during AAV production is independent of size. Packaging of these species is greatly affected by its size. A single ITR and a cryptic resolution site in the plasmid work synergistically, likely causing a source of plasmid backbone contamination.

In vivo rAAV-mediated human TGF-ß overexpression reduces perifocal osteoarthritis and improves osteochondral repair in a large animal model at one year.

OBJECTIVE: Osteoarthritis (OA) is a serious consequence of focal osteochondral defects. Gene transfer of human transforming growth factor beta (hTGF-ß) with recombinant adeno-associated virus (rAAV) vectors offers a strategy to improve osteochondral repair. However, the long-term in vivo effects of such rAAV-mediated TGF-ß overexpression including its potential benefits on OA development remain unknown. METHOD: Focal osteochondral defects in minipig knees received rAAV-lacZ (control) or rAAV-hTGF-ß in vivo. After one year, osteochondral repair and perifocal OA were visualized using validated macroscopic scoring, ultra-high-field MRI at 9.4 T, and micro-CT. A quantitative estimation of the cellular densities and a validated semi-quantitative scoring of histological and immunohistological parameters completed the analysis of microarchitectural parameters. RESULTS: Direct rAAV-hTGF-ß application induced and maintained significantly improved defect filling and safranin O staining intensity and overall cartilage repair at one year in vivo. In addition, rAAV-hTGF-ß led to significantly higher chondrocyte densities within the cartilaginous repair tissue without affecting chondrocyte hypertrophy and minimized subarticular trabecular separation. Of note, rAAV-hTGF-ß significantly improved the adjacent cartilage structure and chondrocyte density and reduced overall perifocal OA development after one year in vivo. CONCLUSIONS: rAAV-hTGF-ß treatment improves long-term osteochondral repair and delays the progression of perifocal OA in a translational model. These findings have considerable potential for targeted molecular approaches to treat focal osteochondral defects.

Development and evaluation of a mouse model susceptible to severe fever with thrombocytopenia syndrome virus by rAAV-based exogenous human DC-SIGN expression.

Experimental animal model is indispensable to evaluate the prophylactic and therapeutic candidates against severe fever with thrombocytopenia syndrome virus (SFTSV). To develop a suitable mouse model for SFTSV infection, we delivered human dendritic cell-specific ICAM-3-grabbing non-integrin (hDC-SIGN) by adeno-associated virus (AAV2) and validated its susceptibility for SFTSV infection. Western blot and RT-PCR assays confirmed the expression of hDC-SIGN in transduced cell lines and a significantly increased viral infectivity was observed in cells expressing hDC-SIGN. The C57BL/6 mice transduced with AAV2 exhibited a stable hDC-SIGN expression in the organs for 7 days. Upon SFTSV challenge with 1 × 105 FAID50, the mice transduced with rAAV-hDC-SIGN showed a 12.5% mortality and reduced platelet and white blood cell count in accordance with higher viral titer than control group. Liver and spleen samples collected from the transduced mice had pathological signs similar to the IFNAR-/- mice with severe SFTSV infection. Collectively, the rAAV-hDC-SIGN transduced mouse model can be used as an accessible and promising tool for studying the SFTSV pathogenesis and pre-clinical evaluation of vaccines and therapeutics against the SFTSV infection.

Intra-articular injection of rAAV-hFGF-2 ameliorates monosodium iodoacetate-induced osteoarthritis in rats via inhibiting TLR-4 signaling and activating TIMP-1.

Osteoarthritis (OA) is a chronic debilitating degenerative disorder leading to structural, and functional anomaly of the joint. The present study tests the hypothesis that overexpression of the basic fibroblast growth factor (FGF-2) via direct rAAV-mediated gene transfer suppresses monosodium iodoacetate (MIA)-induced knee OA in rats relative to control (reporter rAAV-lacZ vector) gene transfer by intra-articular injection. Rats were treated with 20 µl rAAV-hFGF-2 on weekly basis; on days 7, 14, and 21 after single intra-articular injection of MIA (3 mg/50 µl saline). FGF-2 reduced knee joint swelling and improved motor performance and muscle coordination as evidenced by increased distance travelled, mean speed, rearing frequency in open field test (OFT) as well as fall-off latency in rotarod test together with reduced immobility time in OFT. Moreover, FGF-2 attenuated MIA-related radiological and histological alterations. Indeed, FGF-2 decreased knee joint inflammatory biomarker as demonstrated by reduced mRNA expression of toll like receptor (TLR)-4 and its downstream mediators such as tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1ß) and high motility group box (HMGB) 1. In parallel, FGF-2 attenuated knee joint degradation biomarkers as reflected by the downregulation of ADAMTS-5 mRNA expression and matrix metalloproteinase 13 (MMP-13) content together with the up-regulation of tissue inhibitor of metalloproteinase (TIMP)-1 mRNA expression. These findings suggest a potential therapeutic role for FGF-2 against MIA-induced knee OA in rats via inhibition of TLR4 signaling and activating TIMP-1, resulting in down-regulation of ADAMTS-5 and MMP-13.