Development of a highly efficient purification process for recombinant adenoviral vectors for oral gene delivery

Oncolytic virus purification with periodic counter-current chromatography

Virus-based biologicals are one of the most promising biopharmaceuticals of the 21st century medicine and play a significant role in the development of innovative therapeutic, prophylactic, and clinical applications. Oncolytic virus manufacturing scale can range from 5 L in research and development up to 50 L for clinical studies and reach hundreds of liters for commercial scale. The inherent productivity and high integration potential of periodic counter-current chromatography (PCC) offer a transversal solution to decrease equipment footprint and the reduction of several non-value-added unit operations. We report on the design of an efficient PCC process applied to the intermediate purification of oncolytic adenovirus. The developed ion-exchange chromatographic purification method was carried out using a four-column setup for three different scenarios: (i) variation in the feedstock, (ii) potential use of a post-load washing step to improve virus recovery, and (iii) stability during extended operation. Obtained virus recoveries (57%-86%) and impurity reductions (>80% DNA, and >70% total protein) match or overcome batch purification. Regarding process stability and automation, our results show that not only the dynamic control strategy used is able to suppress perturbations in the sample inlet but also allows for unattended operation in the case of ion exchange capture.

A Flow-Through Chromatographic Strategy for Hepatitis C Virus-Like Particles Purification

Biopharmaceuticals are currently becoming one of the fastest growing segments of the global pharmaceutical industry, being used in practically all branches of medicine from disease treatment to prevention. Virus-like particles (VLP) hold tremendous potential as a vaccine candidate due to their anticipated immunogenicity and safety profile when compared to inactivated or live attenuated viral vaccines. Nevertheless, there are several challenges yet to be solved in the development and manufacturing of these products, which ultimately can increase time to market. Suchlike virus-based products, the development of a platform approach is often hindered due to diversity and inherent variability of physicochemical properties of the product. In the present work, a flow-through chromatographic purification strategy for hepatitis C VLP expressed using the baculovirus-insect cell expression system was developed. The impact of operational parameters, such as residence time and ionic strength were studied using scaled-down models and their influence on the purification performance was described. The flow-through strategy herein reported made use of radial-flow chromatography columns packed with an anion exchanger and was compared with a bind and elute approach using the same chromatography media. Overall, by selecting the optimal operational setpoints, we were able to achieve higher VLP recoveries in the flow-through process (66% versus 37%) with higher removal of DNA, baculovirus and host-cell protein (92%, 99% and 50% respectively).

The Role of Heparan Sulfate and Perlecan in Bone-regenerative Procedures

Tissue engineering, grafting procedures, regeneration, and tissue remodeling are developing therapeutic modalities with great potential medical value, but these regenerative modalities are not as effective or predictable as clinicians and patients would like. Greater understanding of growth factors, cytokines, extracellular matrix molecules, and their roles in cell-mediated healing processes have made these regenerative therapies more clinically viable and will continue advancing the fields of tissue engineering and grafting. However, millions of oral and non-oral bone-grafting procedures are performed annually, and only a small percentage yield the most desirable results. Here we review the heparan-sulfate-decorated extracellular biomolecule named perlecan and the research relating to its potential as an adjunct in bone-regenerative procedures. The review includes an overview of bone graft substitutes and biological adjuncts to bone-regenerative procedures in medicine as they apply to periodontal disease, alveolar ridge augmentation, and barrier membrane therapy. Perlecan is discussed as a potential biological adjunct in terms of growth factor sequestration and delivery, and promoting cell adhesion, proliferation, differentiation, and angiogenesis. Further, we propose delivery and application schemes for perlecan and/or its domains in bone-regenerative procedures, with particular emphasis on its heparan-sulfate-decorated domain I. The perlecan molecule, with its heparan sulfate glycosylation, may provide a multi-faceted approach for the delivery of a more comprehensive stimulus than other single potential adjuncts currently available for bone-regenerative procedures.

Current and emerging cell culture manufacturing technologies for influenza vaccines

Annually, influenza virus infects millions of people worldwide. Vaccination programs against seasonal influenza infections require the production of hundreds of million doses within a very short period of time. The influenza vaccine is currently produced using a technology developed in the 1940s that relies on replicating the virus in embryonated hens' eggs. The monovalent viral preparation is inactivated and purified before being formulated in trivalent or tetravalent influenza vaccines. The production process has depended on a continuous supply of eggs. In the case of pandemic outbreaks, this mode of production might be problematic because of a possible drastic reduction in the egg supply and the low flexibility of the manufacturing process resulting in a lack of supply of the required vaccine doses in a timely fashion. Novel production systems using mammalian or insect cell cultures have emerged to overcome the limitations of the egg-based production system. These industrially well-established production systems have been primarily selected for a faster and more flexible response to pandemic threats. Here, we review the most important cell culture manufacturing processes that have been developed in recent years for mass production of influenza vaccines.

Integrin β3 is required in infection and proliferation of classical swine fever virus

Classical Swine Fever (CSF) is a highly infectious fatal pig disease, resulting in huge economic loss to the swine industry. Integrins are membrane-bound signal mediators, expressed on a variety of cell surfaces and are known as receptors or co-receptors for many viruses. However, the role of integrin β3 in CSFV infection is unknown. Here, through quantitive PCR, immunofluorescence (IFC) and immunocytohistochemistry (ICC), we revealed that ST (swine testicles epithelial) cells have a prominent advantage in CSFV proliferation as compared to EC (swine umbilical vein endothelial cell), IEC (swine intestinal epithelial cell) and PK (porcine kidney epithelial) cells. Meanwhile, ST cells had remarkably more integrin β3 expression as compared to EC, IEC and PK cells, which was positively correlated with CSFV infection and proliferation. Integrin β3 was up-regulated post CSFV infection in all the four cell lines, while the CSFV proliferation rate was decreased in integrin β3 function-blocked cells. ShRNA1755 dramatically decreased integrin β3, with a deficiency of 96% at the mRNA level and 80% at the protein level. CSFV proliferation was dramatically reduced in integrin β3 constantly-defected cells (ICDC), with the deficiencies of 92.6%, 99% and 81.7% at 24 h, 48 h and 72 h post CSFV infection, respectively. These results demonstrate that integrin β3 is required in CSFV infection and proliferation, which provide a new insight into the mechanism of CSFV infection.

Production of adenovirus vectors and their use as a delivery system for influenza vaccines

IMPORTANCE OF THE FIELD

With the emergence of highly pathogenic avian influenza H5N1 viruses that have crossed species barriers and are responsible for lethal infections in humans in many countries, there is an urgent need for the development of effective vaccines which can be produced in large quantities at a short notice and confer broad protection against these H5N1 variants. In order to meet the potential global vaccine demand in a pandemic scenario, new vaccine-production strategies must be explored in addition to the currently used egg-based technology for seasonal influenza.

AREAS COVERED IN THIS REVIEW

Adenovirus (Ad) based influenza vaccines represent an attractive alternative/supplement to the currently licensed egg-based influenza vaccines. Ad-based vaccines are relatively inexpensive to manufacture, and their production process does not require either chicken eggs or labor-intensive and time-consuming processes necessitating enhanced biosafety facilities. Most importantly, in a pandemic situation, this vaccine strategy could offer a stockpiling option to reduce the response time before a strain-matched vaccine could be developed.

WHAT THE READER WILL GAIN

This review discusses Ad-vector technology and the current progress in the development of Ad-based influenza vaccines.

TAKE HOME MESSAGE

Ad vector-based influenza vaccines for pandemic preparedness are under development to meet global vaccine demand.

Adenoviral transduction of enterocytes and M-cells using in vitro models based on Caco-2 cells: the coxsackievirus and adenovirus receptor (CAR) mediates both apical and basolateral transduction

Understanding virus-cell interaction is a key to the design of successful gene delivery vectors. In the present study we investigated Ad5 transduction of enterocytes and M-cells utilizing differentiated Caco-2 cells and cocultures of Caco-2 cells with lymphocytes. Transduction inhibition studies showed that CAR is the major receptor mediating apical and basolateral virus entry in differentiated Caco-2 cells. Integrins and heparan sulfate glycosaminoglycans do not appear to play a significant role. Immunofluorescence localized CAR to sites of cell-cell contact, with staining mostly observed on the cell perimeter. Staining was observed even in nonpermeabilized monolayers, suggesting apical accessibility of the receptor. Cocultures with mouse Peyer's patch lymphocytes or Raji B human lymphocytes were more susceptible to transduction than Caco-2 cells, and the effects were dose-dependent. Similar to Caco-2 cells, CAR and not integrins mediated apical transduction. In conclusion, contrary to other epithelial cell lines, both apical and basolateral transduction of absorptive enterocytes and M-cells is mediated by binding to CAR. The coculture system can be used to study the interactions between M-cells and gene delivery vectors.

Right ventricular beneficial effects of beta adrenergic receptor kinase inhibitor (betaARKct) gene transfer in a rat model of severe pressure overload

Heart failure is associated with abnormalities in betaAR cascade regulation, calcium cycling, expression of inflammatory mediators and apoptosis. Adenoviral mediated gene transfer of betaARKct has beneficial indirect effects on these pathologic processes upon the left ventricular myocardium. The concomitant biochemical changes that occur in the right ventricle have not been well characterized. Sprague-Dawley rats underwent aortic banding and were followed by echocardiography. After a decrease in fractional shortening of 25% from baseline, intracoronary injection of adenoviral-betaARKct (n=14) or adenoviral-beta-galactosidase (control, n=13) was performed. Rats were randomly euthanized on post-operative day 7, 14 or 21. Protein analysis including RV myocardial levels of betaARKct, betaARK1, SERCA(2a), inflammatory tissue mediators (IL-1, IL-6 and TNF-alpha), apoptotic markers (bax and bak), and MAP kinases (jnk, p38 and erk) was performed. ANOVA was employed for group comparison. Adenoviral-betaARKct treated animals showed increased expression of betaARKct and decreased levels of betaARK1 compared with controls. This treatment group also demonstrated normalization of SERCA(2a) expression and decreased levels of the inflammatory markers IL-1, IL-6 and TNF-alpha. The pro-apoptotic markers bax and bak were similarly improved. Ventricular levels of the MAP kinase jnk were increased. Differences were most significant 7 days after gene transfer, but the majority of these changes persisted at 21 days. These results suggest that attenuation of the pathologic mechanisms of beta adrenergic receptor desensitization, SERCA(2a) expression, inflammation and apoptosis, not only occur in the left ventricle but also in the right ventricular myocardium after intracoronary gene transfer of betaARKct during heart failure.

Improved exercise capacity and reduced systemic inflammation after adenoviral-mediated SERCA-2a gene transfer

BACKGROUND

We hypothesized that sarcoplasmic reticulum Ca2+ ATPase pump (SERCA-2a) gene delivery would have beneficial effects upon exercise capacity and markers of inflammation in the setting of heart failure.

MATERIALS AND METHODS

A pressure-overload model of experimental heart failure was used in rats. Following a decrease in fractional shortening of >or=25%, animals underwent intracoronary adenoviral-mediated gene transfection using SERCA-2a. Heart failure animals were randomized to receive the SERCA-2a gene, the beta galactosidase (control) gene, or followed without any further intervention. Exercise and hemodynamic testing were performed, and myocardial and systemic markers of inflammation were assayed after 7 and 21 d.

RESULTS

Animals receiving Ad.SERCA-2a showed an increase in exercise tolerance (499.0 +/- 14.9 versus 312.8 +/- 10.5 s, P < 0.0001) relative to Ad.Gal group. Groups treated with Ad.SERCA-2a had significantly decreased serum levels of the inflammatory markers interleukin-1, interleukin-6, and tumor necrosis factor-alpha compared with Ad.Gal-treated animals. Serum levels of atrial natriuretic peptide were decreased in animals receiving Ad.SERCA-2a compared with animals receiving Ad.Gal at day 7 (0.35 +/- 0.03 versus 0.52 +/- 0.11 pg/mL, P = 0.001). Myocardial levels of the proapoptotic protein bax were reduced in Ad.SERCA-2a -treated animals compared with those receiving Ad.Gal at day 7 (protein level/actin: 0.24 +/- 0.05 versus 0.33 +/- 0.04, P = 0.04) and day 21 (protein level/actin: 0.61 +/- 0.04 versus 0.69 +/- 0.01, P = 0.001).

CONCLUSIONS

Genetic modulation of heart failure using the SERCA-2a gene was associated with improvement in cardiac function and exercise capacity as well as improvements in heart-failure associated inflammatory markers.

Controlled inactivation of recombinant viruses with vitamin B2

Inactivated viruses are important tools for vaccine development and gene transfer. 8-Methoxypsoralen (8-MOP) and long-wavelength ultraviolet irradiation (LWUVI) inactivates many viruses. Toxicity limits its use in animals and humans. Toxicological and photosensitizing properties of riboflavin make it suitable for virus inactivation in preparations for biological use. Viruses expressing beta-galactosidase were mixed with either 8-MOP (1.5mM) or riboflavin (50 microM) and exposed to LWUVI (365 nm) for 2 h. Virus activity was determined by limiting dilution. The half-life of the adenovirus preparation treated with 8-MOP was 8.28 ns(-1) and 36.5 ns(-1) after treatment with riboflavin. Despite the difference in half-life, both preparations were completely inactivated within 45 min. In contrast, the half-lives for adeno-associated virus (AAV) preparations were similar (63 ns(-1) 8-MOP vs. 67 ns(-1) riboflavin). Each AAV preparation was fully inactivated within 90 min. The half-life of lentivirus was 193.4 ns(-1) after treatment with 8-MOP and 208 ns(-1) after exposure to riboflavin. Virus treated with riboflavin was inactivated within 20 min. Virus exposed to 8-MOP was inactivated in 90 min. DNA and RNA viruses can be inactivated by riboflavin and LWUVI and used in physiological systems sensitive to other photochemicals.

Increased tumor localization and reduced immune response to adenoviral vector formulated with the liposome DDAB/DOPE

We aimed to increase the efficiency of adenoviral vectors by limiting adenoviral spread from the target site and reducing unwanted host immune responses to the vector. We complexed adenoviral vectors with DDAB-DOPE liposomes to form adenovirus-liposomal (AL) complexes. AL complexes were delivered by intratumoral injection in an immunocompetent subcutaneous rat tumor model and the immunogenicity of the AL complexes and the expression efficiency in the tumor and other organs was examined. Animals treated with the AL complexes had significantly lower levels of beta-galactosidase expression in systemic tissues compared to animals treated with the naked adenovirus (NA) (P<0.05). The tumor to non-tumor ratio of beta-galactosidase marker expression was significantly higher for the AL complex treated animals. NA induced significantly higher titers of adenoviral-specific antibodies compared to the AL complexes (P<0.05). The AL complexes provided protection (immunoshielding) to the adenovirus from neutralizing antibody. Forty-seven percent more beta-galactosidase expression was detected following intratumoral injection with AL complexes compared to the NA in animals pre-immunized with adenovirus.

CONCLUSIONS

Complexing of adenovirus with liposomes provides a simple method to enhance tumor localization of the vector, decrease the immunogenicity of adenovirus, and provide protection of the virus from pre-existing neutralizing antibodies.

Purification of adenoviral vectors using expanded bed chromatography

The increasing numbers of pre-clinical and clinical trials where recombinant adenoviral vectors are used for gene therapy and vaccination require the development of cost-effective and reproducible large scale purification strategies of the biologically active particles. Alternatives to the traditional laboratory scale CsCl density gradient ultracentrifugation method, such as fixed bed chromatography strategies, have been developed, but the yields of final recovery remain too low due mainly to the capture and concentration steps taking place before and between the chromatographic stages. In this study, a rapid and efficient scale-able purification protocol allowing to obtain concentrated, pure and bioactive adenoviral vectors was developed. This allows efficient levels of binding to the column media and vector purification without centrifugation or filtration steps. Expanded bed chromatography followed by hollow fiber concentration allows the capture of viral particles directly from cellular extracts with high efficiency and vector purification is achieved in less than one working day with a minimal amount of sample handling, thus presenting an improvement over existing processes. The overall process yield reached 32%, representing an eight-fold improvement over results reported previously, while the purity is comparable to that obtained with the CsCl method.

Modification of liposomal concentration in liposome/adenoviral complexes allows significant protection of adenoviral vectors from neutralising antibody, in vitro

Adenoviral vectors have been commonly used in gene therapy protocols, however the success of their use is often limited by the induction of host immunity to the vector. Following exposure to the adenoviral vector, adenoviral-specific neutralising antibodies are produced which limits further administration. This study examines the efficacy of complexing liposomes to adenovirus for the protection of the adenovirus from neutralising antibodies in an in vitro setting. Dimethyldioctadecylammonium bromide (DDAB)-dioleoyl-l-phosphatidylethanolamine (DOPE) liposomes were bound at varying concentrations to adenovirus to form AL complexes and tested these complexes' ability to prevent adenoviral neutralisation. It is shown that by increasing the concentration of liposomes in the adenoviral-liposome (AL) complexes we can increase the level of immuno-shielding afforded the adenovirus. It is also shown that the increase in liposomal concentration may lead to drawbacks such as increased cytotoxicity and reductions in expression levels.

Microsphere-liposome complexes protect adenoviral vectors from neutralising antibody without losses in transfection efficiency, in-vitro

Adenoviral vectors have been commonly used in gene therapy protocols but the success of their use is often limited by the induction of host immunity to the vector. Following exposure to the adenoviral vector, adenoviral-specific neutralising antibodies are produced, which limits further administration. This study examines the effectiveness of a novel combination of microspheres and liposomes for the shielding of adenovirus from neutralising antibodies in an in-vitro setting. We show that liposomes are effective in the protection of adenovirus from neutralising antibody and that the conjugation of these complexes to microspheres augments the level of protection. This study further reveals that previously neutralised adenovirus may still be transported into the cell via liposome-cell interactions and is still capable of expressing its genes, making this vector an effective tool for circumvention of the humoral immune response. We also looked at possible side effects of using the complexes, namely increases in cytotoxicity and reductions in transfection efficiency. Our results showed that varying the liposome:adenovirus ratio can reduce the cytotoxicity of the vector as well as increase the transfection efficiency. In addition, in cell lines that are adenoviral competent, transfection efficiencies on par with uncomplexed adenoviral vectors were achievable with the combination vector.

Effect of adenoviral-mediated transfer of transforming growth factor-beta1 on colonic anastomotic healing

PURPOSE

Transforming growth factor-beta1 plays a central role in colonic repair. We examined the temporal effect of vector-mediated transfer of transforming growth factor-beta1 on colonic anastomotic healing.

METHODS

Male Sprague-Dawley rats (n = 24) underwent transection of the distal colon and single-layer anastomosis. Proximal to the anastomosis, the colon was again transected and a colostomy was matured proximally. The distal colon was intubated with a silicone catheter, tunneled along subcutaneous tissues, and connected to a swivel apparatus for postoperative luminal infusion. Rats were randomized into four groups (n = 6 each). Two control groups received 10(10) plaque-forming units of a Type 5 E1-deleted adenovirus carrying the bacterial beta-galactosidase gene either immediately following surgery or on postoperative Day 3. The treatment groups received transforming growth factor-beta1 with the same viral construct at parallel time points. On postoperative Day 6, anastomotic bursting pressure and site were determined in situ with the anastomotic tissue subsequently harvested and analyzed by enzyme-linked immunosorbent assay for beta-galactosidase and transforming growth factor-beta1.

RESULTS

When compared with its corresponding control, the group that received the transforming growth factor-beta1 gene on postoperative day 3 had a significantly higher bursting pressure (mmHg; 119 +/- 16 vs. 160 +/- 12, mean +/- SD; P = 0.001). While the majority of colons (5/6) from the control group burst at the anastomosis, none of the colons in the group that received transforming growth factor-beta1 on day 3 burst at the anastomotic site (P = 0.007). Beta-Galactosidase levels (pg/ml) in anastomotic tissue were significantly increased in both control groups when compared with their respective treatment groups (101 +/- 43 vs. 38 +/- 30, P = 0.01 when infused the day of surgery and 243 +/- 92 vs. 50 +/- 30, P = 0.009 when infused on day 3). Anastomotic levels of transforming growth factor-beta1 were also increased in the group receiving the transforming growth factor-beta1 gene on day 3 (214 +/- 66 vs. 135 +/- 24, P = 0.02).

CONCLUSIONS

Gene transfer into the healing colonic anastomosis can be effectively achieved via intraluminal administration of adenoviral vectors. Transfer of transforming growth factor-beta1 increased the strength of colonic anastomoses when given at Day 3 but not at Day 0, demonstrating its diverse effects in the wound healing sequence. Thus, gene transfer of transforming growth factor-beta1 may avoid the need for a diverting stoma in cases of rectal surgery and impaired healing resulting from chemotherapy or radiation.

Adenoviral interleukin-3 gene-radiation therapy for prostate cancer in mouse model

PURPOSE

The radiosensitizing effect of IL-3 gene therapy was evaluated on the syngeneic mouse prostate cancer model.

METHODS AND MATERIALS

An adenoviral vector was used to deliver the mIL-3 alpha gene into syngeneic murine prostate (TRAMP-C1) cancer cells growing in a subcutaneous site and the tumor response to irradiation was assessed.

RESULTS

Ad-mIL-3 gene therapy showed no tumor growth delay without radiation. However, intratumoral Ad-mIL-3 injection with radiation therapy showed marked tumor growth delay that was significantly greater than that of radiation alone.

CONCLUSIONS

The combined intratumoral Ad-mIL-3 gene therapy and radiation therapy is a valuable option for further clinical evaluation.

Nonionic Polymeric Micelles for Oral Gene Delivery In Vivo

The main aim of this study was to investigate the feasibility of using nonionic polymeric micelles of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) as a carrier for oral DNA delivery in vivo. The size and appearance of DNA/PEO-PPO-PEO polymeric micelles were examined, respectively, by dynamic light scattering and atomic force microscopy, and their zeta potential was measured. Expression of the delivered lacZ gene in various tissues of nude mice was assessed qualitatively by 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside staining of sections and quantitatively by measuring enzyme activity in tissue extracts, using the substrate of beta-galactosidase, chlorophenol red-beta-D-galactopyranoside. In addition, the types of cells expressing the lacZ gene in the duodenum were identified by histological analysis. DNA/PEO-PPO-PEO polymeric micelles are a single population of rounded micelles with a mean diameter of 170 nm and a zeta potential of -4.3 mV. Duodenal penetration of DNA/PEO-PPO-PEO polymeric micelles was evaluated in vitro by calculating the apparent permeability coefficient. The results showed a dose-independent penetration rate of (5.75 +/- 0.37) x 10(-5) cm/sec at low DNA concentrations (0.026-0.26 microg/microl), but a decrease to (2.89 +/- 0.37) x 10(-5) cm/sec at a concentration of 1.3 microg/microl. Furthermore, when 10 mM RGD peptide or 10 mM EDTA was administered before and concurrent with the administration of DNA/PEO-PPO-PEO polymeric micelles, transport was inhibited ([0.95 +/- 0.57] x 10(-5) cm/sec) by blocking endocytosis or enhanced ([29.8 +/- 5.7] x 10(-5) cm/sec) by opening tight junctions, respectively. After oral administration of six doses at 8-hr intervals, the highest expression of transferred gene lacZ was seen 48 hr after administration of the first dose, with gene expression detected in the villi, crypts, and goblet cells of the duodenum and in the crypt cells of the stomach. Reporter gene activity was seen in the duodenum, stomach, and liver. Activity was also seen in the brain and testis when mice were administered 10 mM EDTA before and concurrent with DNA/PEO-PPO-PEO polymeric micelle administration. lacZ mRNA was detected in these five organs and in the blood by reverse transcription-polymerase chain reaction. Taken together, these results show efficient, stable gene transfer can be achieved in mice by oral delivery of PEO-PPO-PEO polymeric micelles.

In-vitro evaluation of ion-exchange microspheres for the sustained release of liposomal–adenoviral conjugates

This study looks at the development of a novel combination vector consisting of adenovirus conjugated to liposomes (AL complexes) bound to cation-exchanging microspheres (MAL complexes). With adenovirus having a net negative charge and the liposomes a net positive charge it was possible to modify the net charge of the AL complexes by varying the concentrations of adenovirus to liposomes. The modification of the net charge resulted in altered binding and release characteristics. Of the complexes tested, the 5:1 and 2:1 ratio AL complexes were able to be efficiently bound by the microspheres and exhibited sustained release over 24 h. The 1:1 and 1:2 AL complexes, however, bound poorly to the microspheres and were rapidly released. In addition the MAL complexes also were able to reduce the toxicity of the AL complexes, which was seen with the 10:1 ratio. The AL complexes showed considerably more toxicity alone than in combination with microspheres, highlighting a potential benefit of this vector.

Protection against tetanus by needle-free inoculation of adenovirus-vectored nasal and epicutaneous vaccines

The effectiveness of vaccination programs would be enhanced greatly through the availability of vaccines that can be administered simply and, preferably, painlessly without the need for timed booster injections. Tetanus is a prime example of a disease that is readily preventable by vaccination but remains a major threat to public health due to the problems associated with administration of the present vaccine. Here we show that a protective immune response against live Clostridium tetani infection in mice can be elicited by an adenovirus vector encoding the tetanus toxin C fragment when administered as a nasal or epicutaneous vaccine. The results suggest that these vaccination modalities would be effective needle-free alternatives. This is the first demonstration that absorption of a small number of vectored vaccines into the skin following topical application of a patch can provide protection against live bacteria in a disease setting.

Development of formulations that enhance physical stability of viral vectors for gene therapy

This study summarizes our initial efforts to address an issue that is critical to the success of any multicenter gene therapy clinical trial - maintenance of vector viability during shipping and storage at remote test sites. We have identified formulation and processing factors that influence stability of viral preparations such as selection of appropriate buffer systems, cryoprotectants, and storage conditions. Adenovirus and adeno-associated virus expressing E. coli beta-galactosidase (lacZ) were suspended in blends of complex carbohydrates, cyclodextrins and various surfactants. X-gal stains of 293 and 84-31 cells were used to determine infectious titer of all preparations. Potassium phosphate-buffered preparations consistently maintained high viral titers after storage at -20 and 4 degrees C. Blends of sucrose, mannitol, and surfactant showed negligible loss of titer for 35 days at 4 degrees C. Formulations of sucrose and cyclodextrin were stable for 2 years at -20 degrees C. Negligible loss in titer was observed in unit-dose viral preparations lyophilized in sucrose and stored at 4 degrees C for 1 year after an initial loss of 0.5 log due to processing. Studies with lyophilized sucrose/mannitol blends have shown that viral recovery after processing is directly related to the final moisture content of the dried product. Virus concentration also plays a significant role in recovery after processing with highly concentrated preparations showing minimal loss in titer after lyophilization. In summary, lyophilized preparations that can be shipped and stored at 25 degrees C offer a solution to the current problem of distribution of viral vectors for clinical trials.

Innovations in oral gene delivery: challenges and potentials

The oral delivery of peptide, protein, vaccine and nucleic acid-based biotechnology products is the greatest challenge facing the drug delivery industry. Oral delivery is attractive due to factors such as ease of administration, leading to improved patient convenience and compliance, thereby reducing overall healthcare costs. The realization that gene therapy will provide a tangible and potentially huge new therapeutic opportunity has stimulated interest in oral gene delivery. Here we summarize the oral gene delivery vehicles currently in use and highlight potential areas of application, along with the challenges that need to be overcome before this new technology enters the clinic.

Ammonium sulphate precipitation of recombinant adenovirus from culture medium: an easy method to increase the total virus yield

In the majority of the methods for purifying and concentrating recombinant adenoviruses (rAds) the virus that is associated with the helper cells is harvested, while the virus that is present in the cell-culture medium is discarded. During routine propagation of adenovirus type-5 vectors at optimised conditions we noted that, on average, 47% of the total amount of virus is present in the culture medium. To recover and concentrate these rAds from the medium, we devised a method, which is based on ammonium sulphate ((NH4)2SO4) precipitation. At 40% (NH4)2SO4 saturation, 95 +/- 6% of the available virus precipitates from the medium, while the majority of the protein (85%) remains in solution. In contrast to adenovirus precipitation with polyethylene glycol, the (NH4)2SO4 precipitation technique allows collection of precipitated rAds by filtration. We demonstrate here that (NH4)2SO4 precipitation of rAds from cell-culture medium is a simple and fast technique that can be used in combination with standard virus isolation methods to increase the yields of rAds.

Factors that influence stability of recombinant adenoviral preparations for human gene therapy

This report identifies formulation and processing factors that influence stability of viral preparations such as selection of appropriate buffer systems, cryoprotectants, and cooling rates. Adenovirus type 5 containing the lacZ marker gene was suspended in combinations of trehalose, sorbitol, sucrose, mannitol, glycine, CaCl2, and gelatin. X-gal stains of 293 cells were used to determine the lac-forming units (lfu)/ml of each preparation before and after treatments. Phosphate-buffered solutions (except those containing sucrose or trehalose) demonstrated a drop of 3 pH units upon freezing regardless of cryoprotectant used. Tris-buffered solutions demonstrated a variation in pH which was dependent upon chosen cryoprotectant, with 1 M trehalose exhibiting no change and a 5% mannitol/10 mM CaCl2 combination showing a 3-unit drop in pH. 4-[2-Hydroxyethyl]-1-piperazine ethanesulfonic acid (HEPES)-buffered solutions showed little change in initial pH when frozen regardless of cryoprotectant chosen. In solution, adenovirus was not affected by incubation for 24 hr in buffers ranging from pH 4 to 8. However, when the solutions were frozen, the number of remaining infectious virions was dependent upon the final pH of the suspending medium. Cryoprotectant solutions that significantly maintained viral stability during a single freeze--thaw cycle were 0.5 M sucrose, 0.5 M trehalose, and 10% sorbitol/0.4% gelatin. Long-term stability studies were performed at 4 degrees C with lyophilized sorbital/gelatin and sucrose preparations. Both formulations provided adequate stability for the adenovirus, with 2.6 and 5.6 x 10(11) lfu/ml detected 150 days after drying, respectively.