Alternative Methods of Vaccine Delivery: An Overview of Edible and Intradermal Vaccines

Criscuolo, E.; Caputo, V.; Diotti, R. A.; Sautto, G. A.; Kirchenbaum, G. A.; Clementi, N.

In the context of edible vaccines aimed at eliciting pathogen-specific responses, it will be necessary to overcome mucosal tolerance. Briefly, mucosal tolerance is achieved against certain foreign antigens, such as those contained in our food, and serves to prevent unnecessary and potentially detrimental immune responses in the gut mucosa. Due to this phenomenon, an erroneous mucosal vaccine formulation could induce a T reg -based tolerogenic response instead of Th17-mediated protective immunity [17] . This potential shortcoming can be circumvented using several strategies, including incorporation of an appropriate adjuvant in the vaccine formulation or using sufficiently high doses of antigen to promote induction of effector rather than regulatory cells [5, 11] . Moreover, in the context of edible-based vaccine immunizations, it will also be important to consider the characteristics of the GIT, in which several factors, including proteolytic enzymes, acidic pH, bile salts, and limited permeability, may hinder the induction of a protective immune response [10] . To this end, conjugation of the vaccine antigen with specific ligands that enhance their uptake by M cells represents a focus of ongoing studies aimed at improving immunogenicity [18] . Moreover, antigen bioencapsulation avoids degradation and conformational alterations [19] .