In collaboration with Jacques Terrettaz and François Tranquart, Bracco SA-Geneva
The use of well characterized recombinant or purified protein antigens (Ag) for vaccination is of interest for safety reasons and in the case where inactivated pathogens are not available (cancer, allergy). However it requires the addition of adjuvants such as Ag carrier or immune stimulators to potentiate their immunogenicity. In this research project, we have demonstrated that gas-filled microbubbles (MB) can serve as an efficient Ag delivery system to promote phagocytosis of the model Ag ovalbumin (OVA) without the need of ultrasound application. Once internalized by DC, OVA is processed and presented to both CD4 and CD8 T cells in vitro; such observations are coupled with the capacity of MB to activate DC. In vivo administration of MB-associated OVA in naïve wild-type Balb/c mice induces OVA-specific antibody and T cell responses. Further, the production of both IgG1 and IgG2a serum antibodies, as well as the secretion of IFN- and IL-10 by splenocytes is demonstrated. Therefore, the data presented here settle the proof of principle for the further evaluation of MB-based immunomodulation studies.
A, dendritic cells were incubated with Cy3:OVA-MB for 3 h and with fluorescent transferrin for the last hour (upper panels) or stained for intracellular LAMP-1 expression (lower panels). Slides were then observed by CLSM. Magnification 63x. Bars represent 5 ?m. N, nucleus; CM, cell membrane.
B, mouse serum immunized with OVA adsorbed on microbubbles or alum were analyzed for the presence of OVA-specific IgG1 Ab by ELISA. Data show the compilation of 8 immunized mice. Bars represent the median value of each mouse group.