Transfollicular delivery takes root: the future for vaccine design?

The immunological environment of hair follicles has lately received the attention of researchers in the context of transfollicular drug delivery, particularly for improving needle-free transcutaneous immunization. Hair follicles represent shunt pathways across the stratum corneum barrier, which may facilitate the absorption of large or hydrophilic molecules such as vaccine antigens. Currently researchers have identified opportunities and challenges created by transfollicular vaccination. Nanotechnology may facilitate transfollicular delivery in several ways as nanoparticles penetrate deeper and to a higher extent into hair follicles than solutions. Also, nanoencapsulation can stabilize antigens and increase their antigenicity. This seems necessary as only a limited portion of topically applied antigen is available via the hair follicles and as the responsiveness of perifollicular Langerhans cells varies during hair cycle. These problems may be overcome by developing more efficient adjuvant-coupled nanocarriers with high antigen payload.