Production, purification and immunogenicity of Gag virus-like particles carrying SARS-CoV-2 components.

The virus-like particle (VLP) platform is a robust inducer of humoral and cellular immune responses; hence, it has been used in vaccine development for several infectious diseases. In the current work, VLPs carrying SARS-CoV-2 Spike (S) protein (Wuhan strain) with an HIV-1 Gag core were produced using suspension HEK 293SF-3F6 cells by transient transfection. The Gag was fused with green fluorescent protein (GFP) for rapid quantification of the VLPs. Five different versions of Gag-Spike VLPs (Gag-S-VLPs) consisting of Gag-S alone or combined with other SARS-CoV-2 components, namely Gag-S-Nucleocapsid (N), Gag-S-Matrix (M), Gag-S-Envelope (E), Gag-S-MEN, along with Gag alone were produced and processed by clarification, nuclease treatment, concentration by tangential flow filtration (TFF) and diafiltration. A pilot mouse study was performed to evaluate the immunogenicity of the Gag-S-VLPs through the measurement of the humoral and/or cellular responses against all the mentioned SARS-CoV-2 components. Antibody response to Spike was observed in all variants. The highest number of Spike-specific IFN-γ + T cells was detected with Gag-S-VLPs. No induction of antigen-specific cellular responses to M, N or E proteins were detected with any of the Gag-S, M, E/or N VLPs tested. Therefore, the Gag-S-VLP, by reason of consistently eliciting strong antigen-specific cellular and antibody responses, was selected for further evaluation. The purification process was improved by replacing the conventional centrifugation by serial microfiltration in the clarification step, followed by Spike-affinity chromatography to get concentrated VLPs with higher purity. Three different doses of Gag-S-VLP in conjunction with two adjuvants (Quil-A or AddaVax) were used to assess the dose-dependent antigen-specific cellular and antibody responses in mice. The Gag-S-VLP adjuvanted with Quil-A resulted in a stronger Spike-specific cellular response compared to that adjuvanted with AddaVax. A strong spike neutralisation activity was observed for all doses, independent of the adjuvant combination.

Preclinical Development and Characterization of Novel Adeno-Associated Viral Vectors for the Treatment of Lipoprotein Lipase Deficiency.

Lipoprotein lipase deficiency (LPLD) results from mutations within the lipoprotein lipase (LPL) gene that lead to a complete lack of catalytically active LPL protein. Glybera was one of the first adeno-associated virus (AAV) gene replacement therapy to receive European Medicines Agency regulatory approval for the treatment of LPLD. However, Glybera is no longer marketed potentially due to a combination of economical, manufacturing, and vector-related issues. The aim of this study was to develop a more efficacious AAV gene therapy vector for LPLD. Following preclinical biodistribution, efficacy and non-Good Laboratory Practice toxicity studies with novel AAV1 and AAV8-based vectors in mice, we identified AAV8 pVR59. AAV8 pVR59 delivered a codon-optimized, human gain-of-function hLPLS447X transgene driven by a CAG promoter in an AAV8 capsid. AAV8 pVR59 was significantly more efficacious, at 10- to 100-fold lower doses, compared with an AAV1 vector based on Glybera, when delivered intramuscularly or intravenously, respectively, in mice with LPLD. Efficient gene transfer was observed within the injected skeletal muscle and liver following delivery of AAV8 pVR59, with long-term correction of LPLD phenotypes, including normalization of plasma triglycerides and lipid tolerance, for up to 6 months post-treatment. While intramuscular delivery of AAV8 pVR59 was well tolerated, intravenous administration augmented liver pathology. These results highlight the feasibility of developing a superior AAV vector for the treatment of LPLD and provide critical insight for initiating studies in larger animal models. The identification of an AAV gene therapy vector that is more efficacious at lower doses, when paired with recent advances in production and manufacturing technologies, will ultimately translate to increased safety and accessibility for patients.

Packaging cells for lentiviral vectors generated using the cumate and coumermycin gene induction systems and nanowell single-cell cloning.

Lentiviral vectors (LVs) are important for cell therapy because of their capacity to stably modify the genome after integration. This study describes a novel and relatively simple approach to generate packaging cells and producer clones for self-inactivating (SIN) LVs pseudotyped with the vesicular stomatitis virus glycoprotein (VSV-G). A novel gene regulation system, based on the combination of the cumate and coumermycin induction systems, was developed to ensure tight control for the expression of cytotoxic packaging elements. To accelerate clone isolation and ensure monoclonality, the packaging genes were transfected simultaneously into human embryonic kidney cells (293SF-3F6) previously engineered with the induction system, and clones were isolated after limiting dilution into nanowell arrays using a robotic cell picking instrument with scanning capability. The method's effectiveness to isolate colonies derived from single cells was demonstrated using mixed populations of cells labeled with two different fluorescent markers. Because the recipient cell line grew in suspension culture, and all the procedures were performed without serum, the resulting clones were readily adaptable to serum-free suspension culture. The best producer clone produced LVs expressing GFP at a titer of 2.3 × 108 transduction units (TU)/mL in the culture medium under batch mode without concentration.

Rapid In-Process Monitoring of Lentiviral Vector Particles by High-Performance Liquid Chromatography.

Lentiviral vectors (LVs) are a popular gene delivery tool in cell and gene therapy and they are a primary tool for ex vivo transduction of T cells for expression of chimeric antigen receptor (CAR) in CAR-T cell therapies. Extensive process and product characterization are required in manufacturing virus-based gene vectors to better control batch-to-batch variability. However, it has been an ongoing challenge to make quantitative assessments of LV product because current analytical tools often are low throughput and lack robustness and standardization is still required. This paper presents a high-throughput and robust physico-chemical characterization method that directly assesses total LV particles. With simple sample preparation and fast elution time (6.24 min) of the LV peak in 440 mM NaCl (in 20 mM Tris-HCl [pH 7.5]), this ion exchange high-performance liquid chromatography (IEX-HPLC) method is ideal for routine in-process monitoring to facilitate the development of scalable and robust LV manufacturing processes. Furthermore, this HPLC method is suitable for the analysis of all in-process samples, from crude samples such as LV supernatants to final purified products. The linearity range of the standard curve is 3.13 × 108 to 1.0 × 1010 total particles/mL, and both the intra- and inter-assay variabilities are less than 5%.

Discovery of MK-1439, an orally bioavailable non-nucleoside reverse transcriptase inhibitor potent against a wide range of resistant mutant HIV viruses.

The optimization of a novel series of non-nucleoside reverse transcriptase inhibitors (NNRTI) led to the identification of pyridone 36. In cell cultures, this new NNRTI shows a superior potency profile against a range of wild type and clinically relevant, resistant mutant HIV viruses. The overall favorable preclinical pharmacokinetic profile of 36 led to the prediction of a once daily low dose regimen in human. NNRTI 36, now known as MK-1439, is currently in clinical development for the treatment of HIV infection.

Pharmacological and genetic evidence that cathepsin B is not the physiological activator of rodent prorenin.

Renin is the first enzyme in the renin-angiotensin-aldosterone system which is the principal regulator of blood pressure and hydroelectrolyte balance. Previous studies suggest that cathepsin B is the activator of the prorenin zymogen. Here, we show no difference in plasma renin activity, or mean arterial blood pressure between wild-type and cathepsin B knockout mice. To account for potential gene compensation, a potent, selective, reversible cathepsin B inhibitor was developed to determine the role of cathepsin B on prorenin processing in rats. Pharmacological inhibition of cathepsin B in spontaneously hypertensive and double transgenic rats did not result in a reduction in renal mature renin protein levels or plasma renin activity. We conclude that cathepsin B does not play a significant role in this process in rodents.

Caspase-7 expanded function and intrinsic expression level underlies strain-specific brain phenotype of caspase-3-null mice.

Caspase-3-deficient mice of the 129S1/SvImJ (129) strain show severe brain development defects resulting in brain overgrowth and perinatal lethality, whereas on the C57BL/6J (B6) background, these mice develop normally. We therefore sought to identify the strain-dependent ameliorating gene. We biochemically isolated caspase-7 from B6-caspase-3-null (Casp3-/-) tissues as being the enzyme with caspase-3-like properties and capability of performing a caspase-3 surrogate function, apoptotic DNA fragmentation. Moreover, we show that, in contrast to the human enzymes, mouse caspase-7 is as efficient as caspase-3 at cleaving and thus inactivating ICAD (inhibitor of caspase-activated DNase), the inhibitor of apoptotic DNA fragmentation. Low levels of caspase-7 expression and activation correlate with lack of DNA fragmentation in 129-Casp3-/- apoptotic precursor neurons, whereas B6-Casp3-/- cells, which can fragment their DNA, show higher levels of caspase-7 expression and activation. The amount of caspase-7 activation in apoptotic precursor neurons is independent of the presence of caspase-3. Together, our findings demonstrate for the first time a strong correlation between caspase-7 activity, normal brain development, and apoptotic DNA fragmentation in Casp3-/- mice.

Differential efficacy of caspase inhibitors on apoptosis markers during sepsis in rats and implication for fractional inhibition requirements for therapeutics.

A rodent model of sepsis was used to establish the relationship between caspase inhibition and inhibition of apoptotic cell death in vivo. In this model, thymocyte cell death was blocked by Bcl-2 transgene, indicating that apoptosis was predominantly dependent on the mitochondrial pathway that culminates in caspase-3 activation. Caspase inhibitors, including the selective caspase-3 inhibitor M867, were able to block apoptotic manifestations both in vitro and in vivo but with strikingly different efficacy for different cell death markers. Inhibition of DNA fragmentation required substantially higher levels of caspase-3 attenuation than that required for blockade of other apoptotic events such as spectrin proteolysis and phosphatidylserine externalization. These data indicate a direct relationship between caspase inhibition and some apoptotic manifestations but that small quantities of uninhibited caspase-3 suffice to initiate genomic DNA breakdown, presumably through the escape of catalytic quantities of caspase-activated DNase. These findings suggest that putative caspase-independent apoptosis may be overestimated in some systems since blockade of spectrin proteolysis and other cell death markers does not accurately reflect the high degrees of caspase-3 inhibition needed to prevent DNA fragmentation. Furthermore, this requirement presents substantial therapeutic challenges owing to the need for persistent and complete caspase blockade.