Mucosal and systemic immune responses following mucosal immunisation of tetanus toxoid entrapped in lipid nanoparticles prepared by microwave reactor

Abstract

In this study, the use of a microwave reactor, which allowed high input of energy into a pressurised system in a short period of time, was investigated for preparation of lipid nanoparticles (LNPs). The aim was to optimise the formulation process by reducing manufacturing time. Two types of LNPs were prepared; non-ionic surfactant vesicles (NISV) and bilosomes (modified NISV incorporating bile salts), with a model antigen (tetanus toxoid, TT) and the immune response induced after mucosal (nasal and oral, respectively) administration was assessed. The TT loaded LNPs were characterised in terms of particle size, size distribution, morphology, and entrapment efficiency. Immunisation was evaluated by lethal challenge with tetanus toxin in an animal model. The efficiency of vaccination was evaluated by measuring the anti-TT IgG antibody levels in the vaccinated animals. Bilosomes formed by this method showed an immunogen entrapment efficiency of ∼30% which was significantly (p < 0.05) higher than entrapment efficiency in the NISV. The percentage of animals that survived when challenged with tetanus toxin correlated with the level of IgG determined in the serum of mice immunised with LNPs by the mucosal route. Moreover, there were significant (p < 0.05) differences between orally and nasally immunised groups. Animal groups immunised bilosomes via the oral route showed the highest level of IgG (1.2 ± 0.13) compared to the positive control, LN + Xn, and no immunised group. Similarly, groups immunised via the nasal route showed significantly (p < 0.0001) higher titres compared with the control group. Mucosal TT was capable of inducing systemic specific IgG anti-TT responses that were higher than the parenteral vaccine.