Immunopotentiator Testing
Dendritic cells are potent antigen presenting cells that are the sentinels of the immune system, sounding the alarm that a pathogen has invaded. Recent studies have shown that dendritic cells with a range of maturation states are naturally produced by the human immune system. In contrast, dendritic cells grown in 2D cell culture tend to have synchronized maturation states which are highly artificial and likely affect performance. VaxDesign’s vaccination site (VS) more closely models the human immune system as compared with existing in vitro methods.
We have shown that a main subpopulation of DCs from the VS have identical phenotypic markers as human dermal explants (13 different phenotype markers were studied).
Our studies have shown that the VS is significantly more sensitive than PBMC assays for simple toll-like receptor (TLR) immunopotentiators such as TLR-3, 4, and 9 that were activated using poly (I:C), LPS, and CpG, respectively.
Cytokine Concentration in Vaccination Site versus PBMCs. Click thumbnails to view larger versions of the charts.
Validation
Validation of the vaccination site construct via phenotype analysis has begun. We’re starting to examine the role of other immunomodulators and adjuvants on the VS to see if its response is predictive of normal human immunophysiology.
For our vaccination site, we hypothesize that antigens and/or vaccine formulations can be added to the VS module to induce a specific immune response. Two methods for antigen delivery are being actively explored:
- Diffusion: Bathing the VS module in the vaccine formulation.
- Injection: Injection of the Ag into the constructs using a microtines process.
Because of possible effects of solubility of the vaccine formulation and potential injection-associated inflammatory responses that may ensue if the microneedles penetrate the endothelium, we can incorporate both approaches.
It is possible that non-soluble vaccine formulations may not be efficiently introduced into the VS without some injection process. For some time, the pursuit of improved vaccine adjuvants, delivery systems and immunomodulators has served as a focal point of preclinical and early phase clinical research. However, the classical FDA-approved aluminum-containing adjuvants Aluminum hydroxide, Aluminum phosphate and Potassium aluminum sulfate (‘Alum’) remain the most commonly used formulations. US-licensed pediatric vaccines formulated with Aluminum salts include: DTP; DTaP; some of the HIB conjugates; Pneumococcal conjugates, Hepatitis B; Hepatitis A; Anthrax; Rabies. Non-Aluminum containing vaccines include: IPV; MMR; Varicella vaccine; influenza vaccine (trivalent inactivated). Furthermore, a number of experimental vaccine adjuvants and delivery systems rely on an array of particle, emulsion and molecular-based formulations demonstrating varied degrees of solubility designed to target specific elements of the immune system with resultant induction of varied effector functions.
The vast majority of current and potentially future vaccine formulations cannot be viewed as strictly ‘soluble’ entities although such formulations may confer enhanced solubility of certain vaccine components in tissues; this will need to be explored. These observations make it important to examine both approaches to vaccine delivery.