Structural Characterization and Formulation Development of a Trivalent Equine Encephalitis Virus-Like Particle...

Area of Science:

• Virology
• Vaccinology
• Biophysics

Background:

• Zoonotic equine encephalitis viruses (EEVs) pose significant health risks, necessitating effective vaccine development.
• Virus-like particles (VLPs) are a promising platform for EEVs vaccines, but their stability is a key challenge.

Purpose of the Study:

• To characterize the physical properties and stability of Eastern, Western, and Venezuelan equine encephalitis virus (EEE, WEE, VEE) VLPs.
• To identify and optimize pharmaceutical excipients for stabilizing EEV VLPs against thermal and freeze-thaw stress.
• To evaluate the stability of EEV VLP formulations under various storage conditions and their interaction with aluminum adjuvants.

Main Methods:

• Transmission electron microscopy and light scattering for VLP characterization.
• Biophysical studies to determine optimal pH and temperature stability ranges.
• Screening of pharmaceutical excipients (sucrose, sorbitol, sodium chloride, pluronic F-68) for stabilization.
• Incubation studies at temperatures from -80°C to 40°C to assess freeze-thaw and long-term stability.
• Analysis of VLP-adjuvant interactions.

Main Results:

• EEV VLPs are enveloped, spherical particles approximately 70 nm in size.
• Optimal VLP stability was observed at pH 7.5-8.5 and temperatures below 50°C, with notable differences between the three VLP strains.
• Sucrose, sorbitol, sodium chloride, and pluronic F-68 were identified as effective stabilizers.
• Formulations showed good stability across tested temperatures, except for instability at -20°C.
• VLP-adjuvant interactions were examined for antigen adsorption and desorption.

Conclusions:

• The identified stabilizers and optimized conditions provide a foundation for developing stable EEV VLP vaccines.
• Understanding the distinct stability profiles of EEE, WEE, and VEE VLPs is critical for formulation.
• Further research into storage conditions, particularly avoiding -20°C, and adjuvant interactions is warranted for successful vaccine development.