Project Lead(s): Carlos Filipe
Although vaccinations are one of the great achievements in human health, many diseases are globally recalcitrant because vaccines must be refrigerated, adding significantly to their cost.
In resource-limited locations in developing countries, vaccine refrigeration is difficult and is one of the barriers to widespread deployment.
According to the World Health Organization, 2.5 million deaths could be prevented with additional diphtheria, tetanus, pertussis (DTP) and measles immunizations.
The goal of this project was to develop a technology to stabilize vaccines against thermal degradation resulting in cost savings in distribution.
Previous research has shown that, by coating powdered vaccines with the polymer pullulan, vaccine viruses can be kept stable at room temperature for months.
Pullulan is a safe, food-grade polysaccharide that has the unique ability to be a very good oxygen barrier, while readily dissolving in water.
In the first step of this project, several different phages were used as surrogates of virus-based vaccines, to identify the best composition of sugar-based films to protect phages against thermal degradation over a period of months.
The best results were obtained when entrapping the phage in sugar-based films containing a mixture of pullulan and trehalose. They subsequently tested the ability of these films to thermally stabilize HSV-2 (herpes simplex virus).
Mice that had been previously infected with HSV were immunized with the vaccine film after keeping the films at room temperature for one month.
The project clearly demonstrated the ability to preserve phages at room temperature for extended periods of time.
Long-term stability was clearly achieved, but an initial drop of particle counts was noted during the drying process in the first 24 hours.
Results of the animal study were mixed, with only 60% of the animals surviving. This was attributed to the initial drop in particle counts, meaning slightly less than the effective dose required for full immunization was delivered.
The team will not be pursuing further funding from Grand Challenges Canada until the initial loss of counts is resolved.