Sublingual injection of microparticles containing glycolipid ligands for NKT cells and subunit vaccines induces antibody responses in oral cavity

• Alpha-galactosylceramide was used as adjuvant in microparticle vaccines.
• Microparticle vaccines containing glycolipid were sublingually injected.
• A 20 fold higher Th1-biased antibody response was induced.
• Induction of IgG and IgA antibody secretion in oral cavity was accomplished.

Natural Killer T (NKT) cells are a unique type of innate immune cells which exert paradoxical roles in animal models through producing either Th1 or Th2 cytokines and activating dendritic cells. Alpha-galactosylceramide (αGalCer), a synthetic antigen for NKT cells, was found to be safe and immune stimulatory in cancer and hepatitis patients. We recently developed microparticle-formulated αGalCer, which is selectively presented by dendritic cells and macrophages, but not B cells, and thus can avoid the anergy of NKT cells. In this study, we have examined the immunogenicity of microparticles containing αGalCer and protein vaccine components through sublingual injection in mice. The results showed that sublingual injection of microparticles containing αGalCer and ovalbumin triggered IgG responses in serum (titer >1:100,000), which persisted for more than 3 months. Microparticles containing ovalbumin alone also induced comparable level of IgG responses. However, immunoglobulin subclass analysis showed that sublingually injected microparticles containing αGalCer and ovalbumin induced 20 fold higher Th1 biased antibody (IgG2c) than microparticles containing OVA alone (1:20,000 as compared to 1:1000 titer). Sublingual injection of microparticles containing αGalCer and ovalbumin induced secretion of both IgG (titer >1:1000) and IgA (titer = 1:80) in saliva secretion, while microparticles containing ovalbumin alone only induced secretion of IgG in saliva. Our results suggest that sublingual injection of microparticles and their subsequent trafficking to draining lymph nodes may induce adaptive immune responses in mucosal compartments. Ongoing studies are focused on the mechanism of antigen presentation and lymphocyte biology in the oral cavity, as well as the toxicity and efficacy of these candidate microparticles for future applications.

Nanoparticles or microparticles are targeted to dendritic cells (step 1) which present αGalCer to NKT cells (step 2). The crosstalk between NKT cells and DCs causes activation of DCs (step 3), which subsequently prime CD4, CD8 and B cells to recognize subunit vaccines (step 4). The memory T cells and B cells enter circulation to survey cancer and pathogens (step 5).Figure optionsDownload as PowerPoint slide