ABSTRACT
Vaccination has emerged as the most effective strategy to confront infectious diseases, among which is leishmaniasis, that threat public health. Despite laborious efforts there is still no vaccine for humans to confront leishmaniasis. Multi-epitope protein/peptide vaccines present a number of advantages, however their use along with appropriate adjuvants that may also act as antigen carriers is considered essential to overcome subunit vaccines' low immunogenicity. In the present study, a stable self-emulsified nanoemulsion was developed and double-adjuvanted with squalene and α-tocopherol. The prepared nanoemulsion droplets exhibited low cytotoxicity in a certain range of concentrations, while they were efficiently taken up by macrophages and dendritic cells in vitro as well as in vivo in secondary lymphoid organs. To further characterize nanoformulation's potent antigen delivery capability, three multi-epitope Leishmania peptides were incorporated into the nanoemulsion. Peptide encapsulation resulted in dendritic cells' functional differentiation characterized by elevated levels of maturation markers and intracellular cytokine production. Intramuscular administration of the nanoemulsion incorporating Leishmania peptides induced antigen-specific spleen cell proliferation as well as elicitation of CD4+ central memory cells, supporting the potential of the developed nanoformulation to successfully act also as an antigen delivery vehicle and thus encouraging further preclinical studies on its vaccine candidate potency.