Oral gavage delivery of PR8 antigen with β-glucan conjugated GRGDS carrier enhance M-cell targeting ability and induce immunity

Abstract

Oral gavage is known as one of most convenient routes for therapeutic administration in compared with other available routes such as intravenous, intra muscular, suppository etc. Oral vaccine delivery system has additional potential as it may provide a convenient way to prevent infectious diseases by introducing optimum immunization in mucus. Although oral vaccine delivery has attracted tremendous interests in vaccine delivery research but various limitations have prevented its rate of progress up to the level as was expected. However, the major problem of oral vaccine delivery is its instability and lack of absorbability resulted from degradation of the sophisticated antigens in acidic medium in stomach. In order to obtain adequate microfold-cell (M-cell) targeting and uptake, the therapeutics is required to pass through stomach and reach to small intestine without degradation. In this project, we have introduced a conjugate of $beta$ - glucan and glycine-arginine-glycine-aspartic acid-serine (GRGDS) that is effective for simultaneous protection of the antigen (PR8) and M-cell targeting efficacy. According to the experimental results, the cationic $beta$ - glucan-GRGDS conjugate can encapsulate a certain amount of anionic PR8 through electrostatic interaction that forms nanoparticles with a range of 200-250nm in diameter. Also, the PR8 incorporated nanoparticles showed high cell viabilities and stabilities in diverse environments. Finally, excellent M-cell targeting abilities were verified in an $in vitro$ M-cell model that shows excellent targeting efficiency. Most importantly the $in vivo$ test obviously demonstrate superiority of this system as it significantly increases antibody concentration in serum, intestine and mucus measured after 21 days of immunization.