Pollen Grains for Oral Vaccination

Oral vaccination continues to be one of the holy grails in vaccinology. Not only is oral vaccination needle-free, convenient, painless, amenable to self-administration, child-friendly, less expensive, safer because needle stick injuries are eliminated, but it can also induce mucosal immunity. Mucosal surfaces are a major portal of pathogen entry, and mucosal immunity has the potential to neutralize pathogens before they can cause infection. Oral vaccination is however difficult to achieve due to the acidic and harsh enzymatic environment of the stomach. We have recently developed pollen shells as a vehicle for oral vaccination. We did studies to evaluate (i) the ability of pollen shells from different plant species to induce a systemic and mucosal immune response in a mouse model using ovalbumin as an antigen, (ii) the durability of the immune response, and (iii) the cytokines secreted by mouse bone marrow derived dendritic cells (mBMDCs) and macrophages in the presence of pollen shells to better understand the mechanism of pollen shells for oral vaccination. Additionally, we also performed in vitro studies to evaluate cytotoxicity of pollen shells by incubating them with Caco-2 cells (to model human epithelial cells). Overall our studies show that pollen shells stimulate both systemic and mucosal immunity thus suggesting that they have good potential to be used for oral vaccination. The in vitro experiments show that pollen shells can activate macrophages and DCs, and thus provide critical information about the mechanism of the potential adjuvant property of pollen shells for oral vaccine delivery.