Y. Xu,, B. Brooks, Z. Zhou, M. Tsuji, X. Kong, C. Tison
Luna Innovations Inc,
United States
Keywords: nanoparticles, antigen, release, malaria vaccine
Summary:
Developing a safe and effective malaria vaccine is critical to reducing the spread and resurgence of the disease. In recent years, vaccine research has broadened with subunit protein and DNA vaccines seeing expanded development due to their inherent safety, simpler storage, and easier production at the expense of attenuated and inactivated organism-based approaches. However, due to their weak immunogenicity, they often necessitate advanced delivery vectors and/or the use of adjuvants. Recent progress in the design of synthetic micro- and nano-particles that can stimulate immune cells directly through their physical and chemical properties opened a new area of vaccine development. However, the complex ability of the Plasmodium organism to infect hosts at multiple stages of its life cycle with varying antigens present at the parasite surface must also be addressed. Luna Innovations is therefore developing a biocompatible chitosan-based layer-by-layer (LBL) “plug and play” nano-assembly vaccine platform that enables the delivery and LBL release of multiple malaria antigens in a controllable manner. A set of chitosan NPs were synthesized and characterized for LBL encapsulation and loading with pre-erythrocytic and erythrocytic stage antigens (full length CSP, AMA-1 and MSP-1). The loading efficiency was between 70%- 98% for each layer of protein. The LBL releases were controlled by tuning the charge and layer thickness of NP construction. The accumulated releases were demonstrated to be higher than 80% for the outer layer of proteins in 3-4 weeks and 15-60% for the inner layers of proteins over this same initial time period. Release continued for another 3-4 weeks until all protein released. Further, the released proteins were evaluated by ELISA and SDS-gel to prove that they maintained antigenicity and stability. Mouse immunogenicity studies demonstrated that Luna’s NP vector is a successful adjuvant. NP vaccine candidate group alone induced the highest PfCSP specific T-cell response. NP vector is extremely potent as a vaccine vector. Two doses of immunization with a longer interval between them, likely 4-5 weeks, should induce the highest humoral response against CSP. Several animal models for toxicity and efficacy are currently being performed for the novel malaria vaccine formulations. The controllable LBL release of different parasite life-stage antigens is expected to generate a stronger immune response and reduce or negate the need for multiple boosters for long term protection.