Mucosal IgA response to rectally administered antigen formulated in IgA-coated liposomes

Ferritin, a soluble model antigen, was used to test whether liposomes can provide an effective delivery vehicle for mucosal immunization via the rectum, and whether the local colonic/rectal secretory immune response to antigen in liposomes can be enhanced by immunoadjuvants. The colonic/rectal IgA response to liposomal ferritin was significantly enhanced over the response to free ferritin but only when cholera toxin (CT) was present as adjuvant. The presence of IgA on the liposome surface increased the uptake of liposomes into Peyer's patch mucosa, and the local rectal/colonic immune response to ferritin about 5-fold over uncoated liposomes. These results show that (1) liposomes co-administered with immunoadjuvants can be used for mucosal immunization via the rectum. (2) Cholera toxin is an effective immunoadjuvant in the rectal/colonic mucosa. (3) IgA can enhance the local secretory immune response to antigen in liposomes, apparently by increasing liposome uptake via M cells.