This thesis work aims to improve the thermal stability of vesicular stomatitis virus (VSV) through spray drying and investigates differences in thermal stability in a matrix between enveloped and non-enveloped viral vectors. The spray drying process was used to dry and encapsulate the VSV vector within the glassy amorphous phase of a matrix of carbohydrate excipients, which imparted increased thermal stability. Viral activity was maintained when the powders were stored for 30 days at 37 °C, in contrast to the liquid control that lost all activity after 15 days. The best excipients for enhancing thermal stability of VSV were trehalose and a 3:1 blend of trehalose and dextran. Immunogenic response from the spray dried trehalose-VSV particles was detected through an in vivo study with Female BALB/c mice after storing the vaccine for 15 days at 37 °C.
Two enveloped viral vectors, VSV and influenza, and a non-enveloped viral vector, human type 5 adenoviral vector (AdHu5) were spray dried with the same formulations to observe how excipients enhance thermal stability and encapsulate the different groups of viruses. The thermal stability of both enveloped viral vectors was enhanced the most when spray dried with trehalose or a 3:1 trehalose/dextran blend, and exhibited the greatest activity loss when spray dried with a mannitol/dextran blend, determined by in vitro TCID50 assays measuring GFP expression. Conversely, the best performing excipient formulation for the non-enveloped viral vector was a mannitol/dextran blend. This led to the hypothesis that the encapsulation mechanism differs between the two groups of viruses. The glass transition temperature (Tg) of the spray dried formulations (without virus) stored at 37 °C for 10 days was measured to infer the potential molecular mobility of the viral vector within the primarily amorphous matrix. Formulations containing dextran exhibited the smallest depression in Tg after storage, indicating minimal increase in molecular mobility over time. RNA leakage from aged spray dried powders containing VSV was quantified to investigate the encapsulation mechanism of enveloped viral vectors and followed a similar trend to the in vitro activity tests. VSV with poor performing excipients yielded the least detectable RNA/pfu after three days of storage at 45°C, suggesting that the lipid envelopes ruptured and released viral RNA which denatured during storage. This work demonstrates that the VSV vector can be thermally stabilized through spray drying but highlights that different carbohydrates interact differently with enveloped versus non-enveloped viral vectors, providing a guideline for future work with the advent of new vaccines. / Thesis / Master of Applied Science (MASc) / Most vaccines lose their activity when stored at room temperature and therefore are required to be stored at temperatures between 4 °C and -80°C to maintain vaccine potency. The refrigeration required to meet these temperatures is costly and limits the distribution of vaccines to resource poor areas in the world where refrigeration technology is uncommon. Spray drying, a process that rapidly dries a solution to form a dry powder, was used to trap vaccines within a sugar matrix to protect the vaccine from heat and structural changes that would otherwise deactivate it. The spray dried powders demonstrated higher thermal stability than liquid samples, which decreases the need for refrigeration during transportation and storage. Thermal stability trends for spray dried powders produced with various sugars and categories of viruses are presented.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22844 |
| Date | 26 April 2018 |
| Creators | Toniolo, Steven |
| Contributors | Cranston, Emily, Chemical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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