Formulation Design Considerations for Oral Vaccines

Abstract

Whilst oral vaccination is a potentially preferred route in terms of patient adherence and mass vaccination, the ability to formulate effective oral vaccines remains a challenge. The primary barrier to oral vaccination is effective delivery of the vaccine through the GI tract owing to the many obstacles it presents, including low pH, enzyme degradation and bile-salt solubilization, which can result in breakdown/deactivation of a vaccine. For effective immune responses after oral administration, particulates need to be taken up by the M cells however, these are few in number. To enhance M-cell uptake, particle characteristics can be optimized with particle size, surface charge, targeting groups and bioadhesive properties all being considerations. Yet improved uptake may not translate into enhanced immune responses and formulating particulates with inherent adjuvant properties can offer advantages. Within this article, we establish the options available for consideration when building effective oral particulate vaccines.

VLPs and particle strategies for cancer vaccines

“…To be effective as oral vaccine, antigens need to be protected from acidic and enzymatic denaturation before reaching their target site (i.e., epithelial M cells), where their uptake should be enhanced to increase immunogenicity [189,190]. A promising strategy to surmount these hurdles is the encapsulation of cancer vaccines in biodegradable particulate delivery systems.…”

Baited vaccines: A strategy to mitigate rodent‐borne viral zoonoses in humans

“…Bait‐style vaccines distributed in the environment for consumption by rodents must be highly immunogenic when consumed via the oral route (Wilkhu, McNeil, Kirby, & Perrie, ). The type of protective immunity induced will depend on the selected antigen and the vaccine platform chosen, but the vaccine should be able to induce both strong cell‐mediated and humoral immunity with consideration of pathogen‐specific correlates of protection.…”

Characterization and optimization of bilosomes for oral vaccine delivery

“…Furthermore due to its non-invasive nature and ease of administration, the oral route can circumvent the need for trained personnel to administer the vaccine. However, the ability of many vaccines to withstand the harsh journey through the gastrointestinal tract, and to be effectively taken up in the appropriate target site is limited (Wilkhu et al, 2011).…”

“…These studies all show that, by orally administering the bilosome vesicles with entrapped antigen, a mucosal immune response is elicited with specific IgA production increased. Therefore, bilosomes can aid vaccine technology by increasing the stability of the vaccine during transit through the GIT, preventing premature release and/or degradation of the antigen during oral transit (Wilkhu et al, 2011).…”