M-cell targeted biodegradable PLGA nanoparticles for oral immunization against hepatitis B

The transcytotic capability and expression of distinct carbohydrate receptors on the intestinal M-cells render it a potential portal for the targeted oral vaccine delivery. PLGA nanoparticles loaded with HBsAg were developed and antigen was stabilized by co-encapsulation of trehalose and Mg(OH)2. Additionally, Ulex europaeus 1 (UEA-1) lectin was anchored to the nanoparticles to target them to M-cells of the peye's patches. The developed systems was characterized for shape, size, polydispersity index and loading efficiency. Bovine submaxillary mucin (BSM) was used as a biological model for the in vitro determination of lectin activity and specificity. The targeting potential of the lectinized nanoparticles were determined by Confocal Laser Scanning Microscopy (CLSM) using dual staining technique. The immune stimulating potential was determined by measuring the anti-HBsAg titre in the serum of Balb/c mice orally immunized with various lectinized formulations and immune response was compared with the alum-HBsAg given intramuscularly. Induction of the mucosal immunity was assessed by estimating secretary IgA (sIgA) level in the salivary, intestinal and vaginal secretion. Additionally, cytokines (interleukin-2; IL-2 and interferon-γ; IFN-γ) level in the spleen homogenates was also determined. The results suggest that HBsAg can be successfully stabilized by co-encapsulation of protein stabilizers. The lectinized nanoparticles have demonstrated approximately 4-fold increase in the degree of interaction with the BSM as compared to plain nanoparticles and sugar specificity of the lectinized nanoparticles was also maintained. CLSM showed that lectinized nanoparticles were predominantly associated to M-cells. The serum anti-HBsAg titre obtained after oral immunization with HBsAg loaded stabilized lectinized nanoparticles was comparable with the titre recorded after alum-HBsAg given intramuscularly. The stabilized UEA-1 coupled nanopartilces exhibited enhanced immune response as compared to stabilized non-lectinized nanoparticles. Furthermore, the stabilized lectinized nanoparticles elicited sIgA in the mucosal secretion and IL-2 and IFN-γ in the spleen homogenates. These stabilized lectinized nanoparticles could be a promising carrier-adjuvant for the targeted oral-mucosal immunization.