Currently, the need for cooled storage and the impossibility of terminal sterilisation are major drawbacks in
vaccine manufacturing and distribution. To overcome current restrictions a preclinical safety and efficacy study was conducted to evaluate new
influenza A
vaccine formulations regarding thermal resistance, resistance against irradiation-mediated damage and storage stability. We evaluated the efficacy of novel
antigen stabilizing and protecting solutions (SPS) to protect influenza A(H1N1)pdm09 split virus
antigen under experimental conditions in vitro and in vivo. Original or SPS re-buffered
vaccine (
Pandemrix) was spray-dried and terminally sterilised by irradiation with 25 kGy (e-beam).
Antigen integrity was monitored by SDS-PAGE, dynamic light scattering, size exclusion chromatography and functional haemagglutination assays. In vitro screening experiments revealed a number of highly stable compositions containing
glycyrrhizinic acid (GA) and/or
chitosan. The most stable composition was selected for storage tests and in vivo assessment of seroconversion in non-human primates (Macaca fascicularis) using a prime-boost strategy. Redispersed formulations with original adjuvant were administered intramuscularly. Storage data revealed high stability of protected
vaccines at 4°C and 25°C, 60% relative humidity, for at least three months. Animals receiving original
Pandemrix exhibited expected levels of seroconversion after 21 days (prime) and 48 days (boost) as assessed by haemagglutination inhibition and microneutralisation assays. Animals vaccinated with spray-dried and irradiated
Pandemrix failed to exhibit seroconversion after 21 days whereas spray-dried and irradiated, SPS-protected
vaccines elicited similar seroconversion levels to those vaccinated with original
Pandemrix. Boost immunisation with SPS-protected
vaccine resulted in a strong increase in seroconversion but had only minor effects in animals treated with non SPS-protected
vaccine. In conclusion, utilising the
SPS formulation technology, spray-drying and terminal sterilisation of influenza A(H1N1)pdm09 split virus
vaccine is feasible. Findings indicate the potential utility of such formulated
vaccines e.g. for needle-free vaccination routes and delivery to countries with uncertain cold chain facilities.