Sodium alginate is a crosslinkable polymer that has demonstrated uses in encapsulation of food, bacterial prebiotics, and small peptides for oral therapeutics delivery. However, existing research on alginate encapsulation of proteins remains scarce. Oral delivery of protein antigens can offer an easier route of administration for vaccines compared to intramuscular injections. Here, we sought to harness the properties of chitosan-coated alginate microdroplets to develop an oral vaccine delivery vehicle for controlled release of protein antigens in the gastrointestinal (GI) tract. We used standard molecular biology techniques including western blot, fluorescence microscopy, and animal models to examine protein-alginate microdroplet characteristics. Although alginate is classified as “Generally Regarded as Safe” by the US Food and Drug Administration, we confirmed that it does not cause acute inflammation in the GI tract. Furthermore, we encapsulated purified mCherry protein and evaluated its stability and release profile using simulated human gastric and intestinal fluids, as well as mouse GI extracts. We observed limited release in gastric conditions and rapid release after exposure to the intestinal environments. In vivo evaluation in orally gavaged mice using encapsulated 200nm fluorescent nanoparticles mirrored the in vitro results. To build on these promising results, we immunized mice using encapsulated recombinant Y. pestis type III secretion system protein, LcrV, and observed an antigen-specific immune response. To enhance the flexibility of this oral delivery system, we also adapted the encapsulation workflow to support cell-free protein synthesis, which has implications for the rapid and scalable production of a wide range of antigens for oral immunization. We envision that a further refined system would enable future decentralized point-of-use vaccine production. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
Merchant et al. (Sun,) studied this question.