Vaccines are composed of three basic elements:
- Antigen—the disease protein designed to trigger the targeted immune response
- Adjuvant—a “booster” molecule that stimulates and adds to the immune response
- Delivery vehicle—the method for reaching the immune system. This can be vector-based—a “skeleton” upon which the other vaccine components are attached.
Vaxart has designed a vector-adjuvant combination that provides a vaccine delivery “platform,” which can be used with many different antigens to create vaccines for oral administration.
The foundation of Vaxart’s platform is a non-replicating adenovirus vector type 5 (Ad5). Adenoviruses, some types of which cause the common cold, have a long history of use in vaccines and a proven safety profile. However, their utility in vaccines was previously limited because once people had been exposed to an adenovirus, whether through catching a cold or receiving a vaccination, their bodies would mount an immune response which would neutralize any subsequent vaccines delivered into the muscle with that same adenovirus.
Vaxart has solved this problem by using the vector in a new way—delivering the Ad5-vectored vaccine via tablet directly to the gut, an organ that doesn’t induce the same sort of anti-vector immunity, thus avoiding any neutralization by blood- or muscle tissue-based immune cells.
This approach requires the use of an adjuvant, as protein vaccines are generally not effective in the gut. Vaxart has developed a patented adjuvant that works through a toll-like receptor (TLR). TLRs have been widely applied in vaccines and are well-accepted as effective immune stimulators. Vaxart uses the only TLR known to be fully effective in the gastrointestinal tract and has “coupled” the adjuvant to the target antigen. The end result is a selective, strong and reliable immune response when administered orally.
Modular Vaccine Creation
Vaxart has demonstrated the ability to use the same non-replicating Ad5 vector platform to vaccinate against multiple diseases, using a series of different oral vaccines.
By using the same vector to different antigens, Vaxart can pursue a modular, standardized approach to vaccine development. This approach supports rapid and low-cost development, key factors in the event of an emerging pathogen. Further, it reduces regulatory risk, as safety data from one vaccine will directly support others created with the same platform, allowing the FDA to evaluate a “master file” for the platform.