Oral hepatitis B vaccine: chitosan or glucan based delivery systems for efficient HBsAg immunization following subcutaneous priming
The World Health Organization encourages “the development of oral formulations to simplify their transport, storage and administration in poor countries”, and to “facilitate an effective immunization program to prevent sexually transmitted hepatitis B”. Thus, two distinct and promising delivery systems were developed: recombinant hepatitis B surface antigen (HBsAg) encapsulated into alginate-coated chitosan particles (AlgChiPs) and into glucan particles (GPs) mainly composed of β-1,3-d-glucan. In vitro preliminary studies showed that both could be internalized by peripheral blood mononuclear cells and murine Peyer's patches, an imperative aspect regarding oral immunization. Chitosan particles (ChiPs) have shown interesting immunostimulating properties as mast cells activators. Vaccination studies reveal that three oral immunizations induced serum anti-HBsAg Immunoglobulin G (IgG) in 60 % of the animals and anti-HBsAg secretory IgA in faeces for both formulations. When subcutaneous (SC) priming was done, followed by two oral boosts, all mice were responder and much higher serum anti-HBsAg IgG titers were observed, besides mucosal protective immunity.