This work focuses on the development of a spray dried adenoviral vector for its application as a thermally stable and inhalable vaccine against tuberculosis. / As the global public health community continues to strive for more equitable vaccine access, thermal instability of liquid vaccines continues to be a significant challenge due to strict cold-chain temperature requirements. Dry powder vaccines offer a favourable alternative, with the ability to retain vaccine efficacy at ambient temperature conditions. In the form of dry powder, vaccines against respiratory diseases can also be administered via inhalation for targeted delivery to the lung tissue. A processing technique known as spray drying is particularly promising for the development of thermally stable and inhalable dry powder vaccines, offering a method of continuous and scalable production. Spray drying is widely used in the pharmaceutical industry and can effectively encapsulate and immobilize labile biologics, like adenoviral vectors, within a glassy carbohydrate matrix to help retain biologic function. However, pulmonary delivery of a thermally stable, viral vectored dry powder vaccine has yet to be demonstrated.
This thesis focuses on improving the formulation of a carbohydrate excipient blend of mannitol and dextran encapsulating a human serotype 5 adenovirus (AdHu5), with the goal of producing an inhalable vaccine with sufficient viral potency for in vivo murine testing. First, the impact of cryoprotective agents used for frozen storage of the stock adenovirus was investigated with respect to viral activity retention, thermal stability and inhalation properties of the dry powder after spray drying. Trehalose was considered a preferred cryoprotective agent, compared to glycerol traditionally used for adenoviral cryo-storage, allowing for the preparation of a high potency viral dry powder with 1.5 log loss of viral titre after processing and thermal aging. Further investigation of the dextran mass ratio and dextran molecular weight used within the excipient blend revealed that incorporating mannitol in a 1:3 ratio with 500 kDa dextran can further improve viral activity to achieve 0.8 log loss of viral titre after aging. Through controlled drying dynamics, this formulation led to improved activity retention and thermal stability, in addition to desirable aerosolization properties for pulmonary delivery. Using this optimized formulation, custom-made intratracheal dosator devices were evaluated for pulmonary powder delivery in mice. The method of powder loading in the device was found to be a significant factor of device performance in vivo when determining if the critical powder mass dosage could be delivered. Successful intratracheal delivery of the AdHu5-vectored dry powder was achieved with a pipette-tip loading dosator and led to a strong bioactive response. Overall, this work indicates the feasibility of murine pulmonary delivery and immunological testing of a thermally stable, adenoviral-vectored vaccine in dry powder form. / Thesis / Master of Applied Science (MASc) / Most vaccines currently available on the market must be stored and transported at temperatures ranging from 2-8 ⁰C to properly maintain their function, with some vaccine requiring temperatures as low as -80 ⁰C. The equipment required to maintain such temperatures is costly and is a significant limitation for developing nations trying to secure vaccine access. As an alternative to traditional liquid vaccine formulations, dry powder vaccines offer stability at room temperature without the need for expensive equipment and can also be administered through inhalation. Using a processing method called spray drying, an active vaccine component can be encapsulated in a carefully selected sugar formulation which forms a protective coating as the particles dry to provide stabilization. Since the efficacy of such dry powder vaccines must be first evaluated with mouse models, the focus of this work was to improve an existing blend of sugars to produce a dry vaccine powder that contains high enough dosage for mouse testing. Processing losses from spray drying were minimized through careful selection of vaccine cryoprotective agents, in addition to optimizing the blend ratio and molecular weight of sugars used for encapsulation. Successful delivery of the optimized powder to the lungs of mice was also accomplished after analyzing the suitability of a variety of custom-made handheld devices. This work shows that inhalable dry powder vaccine delivery is a promising solution to help improve temperature stability and achieve more equitable access to vaccines globally.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27560 |
| Date | January 2022 |
| Creators | Manser, Myla |
| Contributors | Thompson, Michael, Cranston, Emily, Chemical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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