RESUMO
Transcutaneous immunization (TI) has many practical merits compared to parenteral routes of administration. In the present study, non ionic surfactant vesicular carrier, i.e. niosomes, was evaluated for topical delivery of vaccines using hepatitis B surface protein as an antigen and cholera toxin B as an adjuvant. Niosomes were characterized for size, shape, entrapment efficiency and in process antigen stability. In vitro permeation and skin deposition studies of antigen were performed using human cadaver skin. Skin penetration efficiency of niosomes was assessed by confocal laser scanning microscopy. The immune stimulating activity of these vesicles was studied by measuring the serum IgG titer, isotype ratio IgG2a/IgG1 and mucosal immune responses following transcutaneous immunization in Balb/c mice and results were compared with the alum adsorbed HBsAg given intramuscularly and topically administered plain HBsAg solution. The result shows that optimal niosomal formulation could entrap 58.11 ± 0.71 of antigen with vesicle size range of 2.83 ± 0.29 µm. Serum IgG titers after three consecutive topical administrations were significantly better than single administration of hepatitis antigen with niosomal system, suggesting an effective stimulation of serum immune response; higher IgG1/IgG2a ratio revealed CTB mixed niosomes elicit both Th1 and Th2 responses. This study suggests that topical immunization with cholera toxin B is potential adjuvant for cutaneous immune responses when coadministered with the HBsAg encapsulated niosomes. Results also suggest that the investigated niosomes systems can be effective as topical delivery of vaccines.
