Oral vaccination using microdevices to deliver α-GalCer adjuvanted vaccine afford a mucosal immune response.

Oral vaccination has in the recent years gained a lot of attraction, mainly due to optimized patient compliance and logistics. However, the development of oral vaccines, especially oral subunit vaccines is challenging. Micro technology can be utilized to overcome some of these challenges, by facilitating protection and effective delivery of the vaccine components in the gastrointestinal tract (GI tract). One such technology is Microcontainers (MCs), which can be realized to be mucoadhesive and to target specific regions of the GI tract via oral delivery. Here, we test MCs, for oral delivery of the C. trachomatis vaccine candidate CTH522, in combination with effective mucosal adjuvants. The adjuvants alpha- galactosylceramide (α-GalCer), C-di-GMP and cholera toxin B were compared in vivo, to identify the most prominent adjuvant for formulation with CTH522. Formulations were administered both purely oral and as boosters following a subcutaneous (s.c.) prime with CTH522 in combination with the CAF®01 adjuvant. CTH522 formulated with α-GalCer showed to be the most efficient combination for the oral vaccine, based on the immunological analysis. Lyophilized formulation of CTH522 and α-GalCer was loaded into MCs and these were subsequently coated with Eudragit L100-55 and evaluated in vivo in mice for the ability of MCs to mediate intestinal vaccine delivery and increase immunogenicity of the vaccine. Mice receiving oral prime and boosters did show a significantly enhanced mucosal immune responses compared to naive mice. This indicates the MCs are indeed capable of delivering the vaccine formulation intact and able to stimulate the immune cells. Mice orally boosted with MCs following a s.c. prime with CAF01, demonstrated improved systemic and local Th17 responses, along with increased local IFN-γ and IgA levels compared to both the s.c. prime alone and the homologous oral prime-boost immunization. However, due to the relatively weak observed effect of the MC delivery on the immune responses, it was hypothesized that the MCs are proportionally too large for the GI tract of mice, and thus cleared before an effective immune response can be induced. To investigate this, MCs were loaded with BaSO4, and orally administered to mice. Analysis with X-ray and CT showed a transit time of approximately 1-1.5 h from the stomach to the cecum, corresponding to the standard transit time in mice, and an extremely narrow absorption window. This indicates that mice is not a suitable animal model for evaluation of MCs. These data should be taken into consideration in future in vivo trials with this and similar technologies, where larger animals might be a necessity for proof-of-concept studies.

The Immunogenicity of Capsid-Like Particle Vaccines in Combination with Different Adjuvants Using Different Routes of Administration.

Capsid-like particle (CLP) displays can be used to enhance the immunogenicity of vaccine antigens, but a better understanding of how CLP vaccines are best formulated and delivered is needed. This study compared the humoral immune responses in mice elicited against two different vaccine antigens (a bacterial protein and a viral peptide) delivered on an AP205 CLP platform using six different adjuvant formulations. In comparison to antibody responses obtained after immunization with the unadjuvanted CLP vaccine, three of the adjuvant systems (neutral liposomes/monophosphoryl lipid A/quillaja saponaria 21, squalene-in-water emulsion, and monophosphoryl lipid A) caused significantly increased antibody levels, whereas formulation with the three other adjuvants (aluminum hydroxide, cationic liposomes, and cationic microparticles) resulted in similar or even decreased antibody responses. When delivering the soluble bacterial protein in a squalene-in-water emulsion, 4-log lower IgG levels were obtained compared to when the protein was delivered on CLPs without the adjuvant. The AP205 CLP platform promoted induction of both IgG1 and IgG2 subclasses, which could be skewed towards a higher production of IgG1 (aluminum hydroxide). Compared to other routes, intramuscular administration elicited the highest IgG levels. These results indicate that the effect of the external adjuvant does not always synergize with the adjuvant effect of the CLP display, which underscores the need for empirical testing of different extrinsic adjuvants.