A novel M cell-specific carbohydrate-targeted mucosal vaccine effectively induces antigen-specific immune responses

Mucosally ingested and inhaled antigens are taken up by membranous or microfold cells (M cells) in the follicle-associated epithelium of Peyer's patches or nasopharynx-associated lymphoid tissue. We established a novel M cell-specific monoclonal antibody (mAb NKM 16-2-4) as a carrier for M cell-targeted mucosal vaccine. mAb NKM 16-2-4 also reacted with the recently discovered villous M cells, but not with epithelial cells or goblet cells. Oral administration of tetanus toxoid (TT)- or botulinum toxoid (BT)-conjugated NKM 16-2-4, together with the mucosal adjuvant cholera toxin, induced high-level, antigen-specific serum immunoglobulin (Ig) G and mucosal IgA responses. In addition, an oral vaccine formulation of BT-conjugated NKM 16-2-4 induced protective immunity against lethal challenge with botulinum toxin. An epitope analysis of NKM 16-2-4 revealed specificity to an alpha(1,2)-fucose-containing carbohydrate moiety, and reactivity was enhanced under sialic acid-lacking conditions. This suggests that NKM 16-2-4 distinguishes alpha(1,2)-fucosylated M cells from goblet cells containing abundant sialic acids neighboring the alpha(1,2) fucose moiety and from non-alpha(1,2)-fucosylated epithelial cells. The use of NKM 16-2-4 to target vaccine antigens to the M cell-specific carbohydrate moiety is a new strategy for developing highly effective mucosal vaccines.