Immunogenicity of antigen-conjugated biodegradable polydiacetylene liposomes administered mucosally.

In this work, we report a protocol for synthesizing nanosize ovalbumin-functionalized polydiacetylene (PDA) liposomes (LP-Ova). We show that LP-Ova administered per-orally (p.o.) and subcutaneously (s.c.), without the use of adjuvants, induces high serum IgG1 titers. As reported previously using polystyrene nanoparticles (NPs), p.o.-primed mice developed high titers of IgG2c and intestinal IgA following s.c. boosting immunization with LP-Ova. Mice that received a single s.c. immunization with LP-Ova did not develop serum IgG2c or intestinal IgA antibodies. Additionally, in s.c.-immunized mice serum IgG1 titers decreased significantly by 3 months after immunization. In contrast, in mice primed p.o. and boosted s.c. with LP-Ova, serum IgG1/IgG2c, and intestinal IgA antibody titers remained stable. Administration of LPs exerted no adverse effects on immunized mice as no morbidity or signs of toxicity were observed for the duration of the studies. These results indicate that antigen-conjugated liposomes are immunogenic and confirm a previous report that mucosal priming followed by a s.c. boosting immunization is the most effective strategy for inducing long-lasting mucosal IgA, as well as a polarized Th1/Th2 systemic response. In addition to being biodegradable and easily functionalized by conjugation, liposomes have a hollow core which can also be loaded with cargo, allowing for a targeted delivery of multiple antigens (or drugs) simultaneously. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 557-565, 2017.