Automated Mass Photometry of Adeno-Associated Virus Vectors from Crude Cell Extracts

Mass photometry (MP) is a fast and simple analysis method for the determination of the proportions of subpopulations in an AAV sample. It is label-free and requires minimal sample volumes between 5-10 µL, which makes it a promising candidate over orthogonal techniques such as analytical ultracentrifugation (AUC), cryo-transmission electron microscopy (Cryo-TEM) or charge-detection mass spectrometry (CDMS). However, these methods are limited in their application to purified samples only. Here we developed a purification step based on single-domain monospecific antibody fragments immobilised on either a poly(styrene-divinylbenzene) resin or on magnetic beads prior to MP analysis that allows the quantification of empty, partially filled, full and overfull AAV vectors in crude cell extracts. This is aimed at identifying potentially promising harvest conditions that yield large numbers of filled AAV vectors during the early stages of the viral vector development platform, e.g., the type of transfection reagent used. Furthermore, we provide a direct comparison of the automated and manual handling of the mass photometer with respect to the quantities of AAV subspecies, molar mass of the capsid and payload, and highlight the differences between the "buffer-free" sample measurement and the "buffer-dilution" mode. In addition, we provide information on which candidates to use for calibration and demonstrate the limitations of the mass photometer with respect to the estimation of the capsid titer.

Quantification of Empty, Partially Filled and Full Adeno-Associated Virus Vectors Using Mass Photometry

Adeno-associated viruses (AAV) are one of the most commonly used vehicles in gene therapies for the treatment of rare diseases. During the AAV manufacturing process, particles with little or no genetic material are co-produced alongside the desired AAV capsid containing the transgene of interest. Because of the potential adverse health effects of these byproducts, they are considered impurities and need to be monitored carefully. To date, analytical ultracentrifugation (AUC), transmission electron microscopy (TEM) and charge-detection mass spectrometry (CDMS) are used to quantify these subspecies. However, they are associated with long turnaround times, low sample throughput and complex data analysis. Mass photometry (MP) is a fast and label-free orthogonal technique which is applicable to multiple serotypes without the adaption of method parameters. Furthermore, it can be operated with capsid titers as low as 8 × 10¹⁰ cp mL^-1 with a CV < 5% using just 10 µL total sample volume. Here we demonstrate that mass photometry can be used as an orthogonal method to AUC to accurately quantify the proportions of empty, partially filled, full and overfull particles in AAV samples, especially in cases where ion-exchange chromatography yields no separation of the populations. In addition, it can be used to confirm the molar mass of the packaged genomic material in filled AAV particles.

Biophysical Characterization of Adeno-Associated Virus Vectors Using Ion-Exchange Chromatography Coupled to Light Scattering Detectors

Ion-exchange chromatography coupled to light scattering detectors represents a fast and simple analytical method for the assessment of multiple critical quality attributes (CQA) in one single measurement. The determination of CQAs play a crucial role in Adeno-Associated Virus (AAV)-based gene therapies and their applications in humans. Today, several different analytical techniques, including size-exclusion chromatography (SEC), analytical ultracentrifugation (AUC), qPCR or ELISA, are commonly used to characterize the gene therapy product regarding capsid titer, packaging efficiency, vector genome integrity, aggregation content and other process-related impurities. However, no universal method for the simultaneous determination of multiple CQAs is currently available. Here, we present a novel robust ion-exchange chromatography method coupled to multi-angle light scattering detectors (IEC-MALS) for the comprehensive characterization of empty and filled AAVs concerning capsid titer, full-to-total ratio, absolute molar mass of the protein and nucleic acid, and the size and polydispersity without baseline-separation of both species prior to data analysis. We demonstrate that the developed IEC-MALS assay is applicable to different serotypes and can be used as an orthogonal method to other established analytical techniques.

Prophylactic salpingectomy for prevention of ovarian cancer at the time of elective laparoscopic cholecystectomy

Background

Most serous ovarian cancers are now understood to originate in the fallopian tubes. Removing the tubes (salpingectomy) likely reduces the risk of developing high‐grade serous ovarian cancer. Numerous gynaecological societies now recommend prophylactic (or opportunistic) salpingectomy at the time of gynaecological surgery in appropriate women, and this is widely done. Salpingectomy at the time of non‐gynaecological surgery has not been explored and may present an opportunity for primary prevention of ovarian cancer.

Methods

This study investigated whether prophylactic salpingectomy with the intention of reducing the risk of developing ovarian cancer would be accepted and could be accomplished at the time of elective laparoscopic cholecystectomy. Women aged at least 45 years scheduled for elective laparoscopic cholecystectomy were recruited. They were counselled and offered prophylactic bilateral salpingectomy at the time of cholecystectomy. Outcome measures were rate of accomplishment of salpingectomy, time and procedural steps needed for salpingectomy, and complications.

Results

A total of 105 patients were included in the study. The rate of acceptance of salpingectomy was approximately 60 per cent. Salpingectomy was performed in 98 of 105 laparoscopic cholecystectomies (93·3 per cent) and not accomplished because of poor visibility or adhesions in seven (6·7 per cent). Median additional operating time was 13 (range 4–45) min. There were no complications attributable to salpingectomy. One patient presented with ovarian cancer 28 months after prophylactic salpingectomy; histological re‐evaluation of the tubes showed a previously undetected, focal serous tubal intraepithelial carcinoma.

Conclusion

Prophylactic salpingectomy can be done during elective laparoscopic cholecystectomy.

Decoupling of recombinant protein production from Escherichia coli cell growth enhances functional expression of plant Leloir glycosyltransferases

Sugar nucleotide‐dependent (Leloir) glycosyltransferases from plants are important catalysts for the glycosylation of small molecules and natural products. Limitations on their applicability for biocatalytic synthesis arise because of low protein expression (≤10 mg/L culture) in standard microbial hosts. Here, we showed two representative glycosyltransferases: sucrose synthase from soybean and UGT71A15 from apple. A synthetic biology‐based strategy of decoupling the enzyme expression from the Escherichia coli BL21(DE3) cell growth was effective in enhancing their individual (approximately fivefold) or combined (approximately twofold) production as correctly folded, biologically active proteins. The approach entails a synthetic host cell, which is able to shut down the production of host messenger RNA by inhibition of the E. coli RNA polymerase. Overexpression of the enzyme(s) of interest is induced by the orthogonal T7 RNA polymerase. Shutting down of the host RNA polymerase is achieved by l‐arabinose‐inducible expression of the T7 phage‐derived Gp2 protein from a genome‐integrated site. The glycosyltransferase genes are encoded on conventional pET‐based expression plasmids that allow T7 RNA polymerase‐driven inducible expression by isopropyl‐β‐ d‐galactoside. Laboratory batch and scaled‐up (20 L) fed‐batch bioreactor cultivations demonstrated improvements in an overall yield of active enzyme by up to 12‐fold as a result of production under growth‐decoupled conditions. In batch culture, sucrose synthase and UGT71A15 were obtained, respectively, at 115 and 2.30 U/g cell dry weight, corresponding to ∼5 and ∼1% of total intracellular protein. Fed‐batch production gave sucrose synthase in a yield of 2,300 U/L of culture (830 mg protein/L). Analyzing the isolated glycosyltransferase, we showed that the improvement in the enzyme production was due to the enhancement of both yield (5.3‐fold) and quality (2.3‐fold) of the soluble sucrose synthase. Enzyme preparation from the decoupled production comprised an increased portion (61% compared with 26%) of the active sucrose synthase homotetramer. In summary, therefore, we showed that the expression in growth‐arrested E. coli is promising for recombinant production of plant Leloir glycosyltransferases.

Glycosyltransferase cascades made fit for chemical production: Integrated biocatalytic process for the natural polyphenol C-glucoside nothofagin

Glycosyltransferase cascades are promising tools of biocatalysis for natural product glycosylation, but their suitability for actual production remains to be shown. Here, we demonstrate at a scale of 100 g isolated product the integrated biocatalytic production of nothofagin, the natural 3'-C-β-D-glucoside of the polyphenol phloretin. A parallel reaction cascade involving coupled C-glucosyltransferase and sucrose synthase was optimized for the one-pot glucosylation of phloretin from sucrose via an UDP/UDP-glucose shuttle. Inclusion complexation with the highly water soluble 2-hydroxypropyl-β-cyclodextrin pushed the phloretin solubility to its upper practical limit (∼120 mM) and so removed the main bottleneck on an efficient synthesis of nothofagin. The biotransformation thus intensified had excellent performance metrics of 97% yield and ∼50 gproduct /L at a space-time yield of 3 g/L/hr. The UDP-glucose was regenerated up to ∼220 times. A scalable downstream process for efficient recovery of nothofagin (≥95% purity; ≥65% yield) was developed. A tailored anion-exchange chromatography at pH 8.5 was used for capture and initial purification of the product. Recycling of the 2-hydroxypropyl-β-cyclodextrin would also be possible at this step. Product precipitation at a lowered pH of 6.0 and re-dissolution in acetone effectively replaced desalting by size exclusion chromatography in the final step of nothofagin purification. This study therefore, reveals the potential for process intensification in the glycosylation of polyphenol acceptors by glycosyltransferase cascades. It demonstrates that, with up- and downstream processing carefully optimized and suitably interconnected, a powerful biocatalytic technology becomes available for the production of an important class of glycosides difficult to prepare otherwise.

Integrated process design for biocatalytic synthesis by a Leloir Glycosyltransferase: UDP-glucose production with sucrose synthase

Nucleotide sugar-dependent ("Leloir") glycosyltransferases (GTs), represent a new paradigm for the application of biocatalytic glycosylations to the production of fine chemicals. However, it remains to be shown that GT processes meet the high efficiency targets of industrial biotransformations. We demonstrate in this study of uridine-5'-diphosphate glucose (UDP-glc) production by sucrose synthase (from Acidithiobacillus caldus) that a holistic process design, involving coordinated development of biocatalyst production, biotransformation, and downstream processing (DSP) was vital for target achievement at ∼100 g scale synthesis. Constitutive expression in Escherichia coli shifted the recombinant protein production mainly to the stationary phase and enhanced the specific enzyme activity to a level (∼480 U/g_{cell dry weight} ) suitable for whole-cell biotransformation. The UDP-glc production had excellent performance metrics of ∼100 g_product /L, 86% yield (based on UDP), and a total turnover number of 103 g_UDP-glc /g_{cell dry weight} at a space-time yield of 10 g/L/h. Using efficient chromatography-free DSP, the UDP-glc was isolated in a single batch with ≥90% purity and in 73% isolated yield. Overall, the process would allow production of ∼0.7 kg of isolated product/L E. coli bioreactor culture, thus demonstrating how integrated process design promotes the practical use of a GT conversion. Biotechnol. Bioeng. 2017;114: 924-928. © 2016 Wiley Periodicals, Inc.

Management of pancreatic trauma and its consequences--guidelines or individual therapy?

BACKGROUND/AIMS

Diagnosis of pancreatic trauma and its complications may be difficult due to non-specific signs and symptoms and treatment recommendations are not unequivocal.

METHODOLOGY

Clinical data of a series of 47 patients with pancreatic trauma were analyzed; most of them were polytraumatized and treated by an interdisciplinary team.

RESULTS

The most common causes were traffic accidents and sport injuries with 66% and 15%, respectively. Concomitant injuries were seen in 96% (nonpancreatic intra-abdominal injuries 85% including spleen 38% and liver 34%, extra-abdominal injuries 70%). Concomitant liver injuries were treated conservatively in 31% and operatively in 69% (including hepatic packing in 38%). Concomitant splenic injuries were usually very severe and could be managed conservatively in only 11%. All patients with pancreatic injuries grade III, IV or V (17%) according to the American Association of Surgical Trauma Classification required surgery, endoscopic treatment or interventional radiology. The most common posttraumatic complications were necrotizing pancreatitis (15%), pseudocyst formation (9%), abscesses (6%) and fistulas (4%).

CONCLUSIONS

The status of the pancreatic duct is the crucial point for management of pancreatic trauma and should be assessed as early as possible. Treatment has to be tailored to the individual situation, especially in patients with severe concomitant injuries or prolonged course.

Analysis of KIT (CD117) expression in gallbladder carcinomas by tissue microarray

AIMS

KIT (CD117) is a transmembrane tyrosinase-kinase receptor which has been related to cell proliferation, differentiation, adhesion and control of apoptosis. If present, KIT may provide a suitable target for tumour therapy. In this study, we report the presence of KIT in primary and metastatic gallbladder carcinomas.

METHODS

Formalin-fixed and paraffin-embedded specimens of 57 primary gallbladder carcinomas and 18 corresponding metastases were stained using a tissue microarray technique and two different antibodies.

RESULTS

Only three tumours stained for KIT. With a polyclonal antibody only one well differentiated papillary adenocarcinoma was immunoreactive. With a monoclonal antibody two additional poorly differentiated tubular adenocarcinoma showed weak and focal immunostaining.

CONCLUSIONS

KIT immunoreactivity is infrequent in gallbladder carcinoma. Thus, routine screening of tumour tissues for KIT by immunohistochemistry appears to be cost-ineffective and cannot be recommended. Moreover, the lack of substantial KIT immunoreactivity in both primary and metastatic gallbladder carcinoma tissues does not provide a rationale to investigate imatinib mesylate therapy in clinical trials including patients with advanced disease.

Post-methionine-load hyperhomocysteinemia and increased lipoprotein(a) are associated with renal metabolic dysfunction: a hypothesis

Previous studies have shown that homocysteine influences the structure of lipoprotein(a) [Lp(a)] and its affinity to fibrin, and that there is an increased risk of vascular disease when both homocysteine and Lp(a) are elevated. The aim of this study was to determine whether there is a correlation between increased total homocysteine (tHCY) and high Lp(a) concentrations, and whether increased concentrations of tHCY affect the concentration of unbound serum apolipoprotein(a) [Apo(a)]. Forty-seven male subjects recruited from a primary prevention screening program with normal serum creatinine and Lp(a) concentrations above 30 mg/dL were included and underwent a standardized oral methionine-loading test to increase the plasma tHCY concentration. This increase might lead to a modification of the Apo(a) structure, thus possibly influencing the serum concentration of unbound Apo(a). Fasting blood samples were taken before the tests and after 6 hours. The median values of tHCY increased about 4-fold after the methionine-loading test. Fasting tHCY did not show an association with Apo(a) and a post-methionine load increase of unbound Apo(a) was not observed. Backward multiple linear regression analysis, however, revealed that only post-load tHCY was independently and significantly influenced by Lp(a). Furthermore, Lp(a) correlated significantly with post-load tHCY, but not with fasting tHCY. Subdividing the subjects according to the Lp(a) concentration showed a significantly higher median concentration of tHCY after methionine load in subjects with Lp(a) over 50 mg/dL compared to subjects with Lp(a) under 50 mg/dL (P =.009). A similar cut-off was seen for post-load Apo(a) at 7.3 mg/dL (P =.04). Factors such as age, C677T-methylene-tetrahydrofolate-reductase (MTHFR) mutation, folate, vitamin B(12), and creatinine showed no significant influence on post-load tHCY in the different subgroups. The reasons for our findings remain partially unclear. However, considering our results and the current knowledge on the association of tHCY and Lp(a) concentration with the renal function, we hypothesize that both parameters may be linked by commencing renal metabolic dysfunction. It should be stressed that our hypothesis is speculative and that further studies will be necessary to improve the understanding of the interrelation of tHCY and Lp(a) concentration.