Anthrax Vaccine Adjuvant
Consisting of biodegradable polymer nanospheres using PNS technology for anthrax vaccines
Biodegradable Polymer Vaccine Adjuvant
Microspheres, comprised of biodegradable hydrophobic copolymers, appear to have an adjuvant effect on microencapsulated anthrax rPA, possibly caused by its controlled release and/or immune stimulation of the dendritic cells by the copolymer (Flick-Smith et al., 2002). While highly promising, the hydrophobic microspheres are manufactured from organic solvents.
Aphios has utilized PNS technology to produce a nanoencapsulated rPA vaccine using supercritical fluids in a bench-scale SuperFluids™ PNP apparatus. Preparations were made by varying the components and characterized for rPA content and mean particle size.
Particle sizes of the polymer nanospheres formed encapsulating rPA ranged from 370 nm to 1.54 µm. The data also shows that all three preparations contained rPA, indicating that the encapsulation process did not destroy the antigen. A photomicrograph of rPA-02 nanoparticles shows that the particles are mostly uniform in size with a few variants.
In Vivo Immunization and Efficacy Testing
rPA polymeric nanospheres (rPA-01) were lyophilized and stored at 5ºC during transportation and storage. Lyophilized rPA-01 was formulated with 20% alhydrogel (v/v) in PBS to produce a final rPA concentration of 200 µg/mL. Similarly, rPA alone was formulated with 20% alhydrogel (v/v) in PBS to produce a final rPA concentration of 200 µg/mL, as a control.
Female adult A/J mice (Harlan, UK) were immunized once with a 20 µg dose in 0.1 mL intra-muscularly for either preparation (groups of 5). Response to immunization was monitored by bleeding the mice on day 14 and measuring IgG titers to rPA in serum samples by standard ELISA.
Mice were then challenged on day 21 with 103 MLD equivalent to 106 colony forming units (cfu) of Bacillus anthracis STI strain spores intraperitoneally (i.p.). Survival was monitored over the subsequent 14 days.
The results of the preliminary study indicate the following:
All the vaccinated mice survived, indicating that the rPA-01 was fully protective and that immunogenicity for the encapsulated antigen was preserved. Since this is the first time that rPA has been encapsulated in biodegradable polymer nanospheres by the PNS process, we are encouraged by the successful results of this challenge.
Benefits and Advantages
We are seeking strategic corporate partners as well as partnerships with government and research institutions interested in developing a stable, effective anthrax vaccine adjuvant for anthrax vaccination.
The development of a nanoencapsulated anthrax vaccine adjuvant would lead to the development of adjuvants for HIV, influenza and other infectious animal and human diseases.