PADRE peptide (Pan-DR epitope) (PADRE)

The PADRE peptide (Pan DR-binding Epitope) is a synthetic 13-amino acid sequence designed as a universal helper T-cell epitope that binds with high affinity to most human MHC class II molecules—particularly HLA‑DR alleles—across diverse genetic backgrounds. Its primary function is to facilitate the recruitment and activation of CD4+ helper T cells by promoting efficient antigen presentation. This property makes it an effective tool for enhancing immune responses in various vaccine platforms—including those targeting cancer, infectious diseases such as influenza and HIV, allergies, and potentially autoimmune conditions. The broad applicability stems from its ability to overcome limitations posed by individual variability in MHC-II alleles. PADRE acts not only as an immunogenic carrier alternative but also serves directly as an adjuvant component in prophylactic and therapeutic vaccines. It can be conjugated with B cell epitopes or other antigens to induce strong antibody responses without requiring complex protein carriers like KLH or OVA. Its use has been shown to improve both cellular immunity (via CD4+ T cell help) and humoral immunity (antibody production), making it valuable for next-generation vaccine design. Note on target status: "CD4 helper T cell activation via PADRE epitope" does not refer directly to a molecular target such as a receptor or enzyme but rather describes an immunological process mediated by the synthetic PADRE peptide acting through endogenous MHC-II molecules on antigen-presenting cells. Therefore, this entry should not be considered a canonical druggable target but rather an engineered tool/epitope used within immunotherapeutic strategies.

Other names

Pan DR-binding epitopePan-DR helper T-cell epitopeAKFVAAWTLKAAA (common sequence)Universal MHC class II helper T-cell epitope

By binding broadly to human MHC class II molecules, especially HLA‑DR, the PADRE peptide facilitates the presentation of antigens to CD4+ helper T cells. This leads to robust activation and proliferation of these cells, enhancing both cellular and humoral immune responses. It is used as a universal helper T-cell epitope in vaccines to boost immune recognition of co-administered antigens.