From allergen to oral vaccine carrier: A new face of ragweed pollen.

Oral delivery of vaccines is highly desirable, yet it has met with limited success. Previously we developed allergen-free pollen grains as a novel approach for oral vaccination. We showed that spores of Lycopodium clavatum can be used for oral vaccination. However, it is unknown if pollens of other species can be similarly used as an oral vaccine carrier. Therefore, in this study, we evaluated common ragweed (RW) pollen (Ambrosia elatior) for its oral vaccination potential. Allergen-free RW pollens were prepared from natural pollens through chemical treatment. Eight weekly oral doses of ovalbumin (OVA) formulated with treated RW generated strong systemic (anti-OVA IgG, IgG1, IgG2a, and IgA) and mucosal (anti-OVA IgA) immune responses that sustained for at least three months after vaccination. Mucosal IgA against OVA was found in the lung lavage, feces, saliva, and vaginal secretion. Moreover, three and half months after the last immunization OVA-specific plasma cells were found in the bone marrow that actively secreted IgG and IgG1 antibodies. No IgE against RW-specific proteins was detected in the serum. Overall, RW pollen demonstrated potential for oral vaccine delivery.