Ganglioside GM1 Binding Peptides: A Potential Adjuvant for Transcutaneous Immunization

Cholera toxin (CT) binds ganglioside GM1 and has been used as an adjuvant in transcutaneous immunization. To determine if the adjuvant property of CT was merely due to binding to ganglioside GM1, mice were immunized by the transcutaneous route using hen egg lysozyme (HEL) as the antigen, and either CT or synthetic peptides that bind to ganglioside GM1 as the adjuvant, and the immune responses were evaluated. Both CT and GM1 binding peptides (GM1bp) induced HEL-specific antibodies and T-cell proliferation. However, the immune responses when GM1-bp was used as the adjuvant, was much lower when compared to CT as the adjuvant. GM1-bp maintained or enhanced the co-stimulatory molecules on antigen presenting cells, in particular on JAWS II dendritic cells. Overall, the data suggests that the binding of GM1-bp to ganglioside GM1 alone can induce immune responses to the co-administered antigen.