GAS is a human pathogen that colonizes the oropharynx which may result to severe complications, such as rheumatic heart disease. As a first line of defence, an effective immune response is required at the mucosal surface where the infection occurs. Development of an oral vaccine delivery system that is capable of inducing both mucosal and systemic immune responses is therefore highly desirable. However, safe and efficient delivery of protein or peptide-based antigen by oral mucosal route is often challenging due to low gastric pH or enzymatic degradation in the gastrointestinal tract.
We developed polyelectrolytes-coated nanoliposomes as a novel oral delivery system for the lipopeptide vaccine against group A streptococcus (GAS). The lipid-core peptide (LCP-1) vaccine candidate was synthesized by the conjugation of lipoamino acids with B-cell epitope (J14) derived from GAS M-protein and universal CD4+ T-helper epitope (P25) using microwave-assisted solid-phase peptide synthesis. The vaccine candidate (LCP-1) was loaded into liposomes and their surfaces were covered with opposite-charged polyelectrolytes [sodium alginate and trimethyl chitosan (TMC)]. All produced liposomes formed nanoparticles in the 165-195 nm size range. TMC-coated positively-charged liposomes were promptly taken up by dendritic cells and macrophages while the uptake of negatively-charged liposomes was significantly lower. Developed formulations showed an enhanced stability of particles in simulated gastrointestinal fluids. In vivo oralimmunizationin Swiss outbred mice showed TMC-alginate-coated liposomes produced significantly higher J14 specific mucosal IgA and systemic IgG titres compared to vaccine formulated with a standard mucosal adjuvant. Moreover, high levels of antibody titres were retained even after 150 days following the last immunization. We have demonstrated, for the first time, an efficient oral delivery system for a GAS vaccine which was able to induce long-lasting systemic and mucosal response. Thus, layer-by-layer, engineered nano-structures based on polyelectrolytes-coated nanoliposomes are a promising oral delivery system for lipopeptide-based vaccines. Our findings are important steps towards the production of more feasible, cost-effective, patient-friendly and practical oral vaccines.