Unlocking the Potency of Keyhole Limpet Hemocyanin: Structural Insights, Immunological Mechanisms, and Therapeutic Frontiers.

Keyhole limpet hemocyanin (KLH) is a large copper-containing glycoprotein derived from the marine gastropod Megathura crenulata. Originally functioning as an oxygen transport molecule, KLH has gained considerable attention in biomedical research due to its exceptional immunogenic and immunostimulatory properties. Its complex quaternary structure, extensive glycosylation, and xenogeneic origin contribute to its ability to induce robust humoral and cellular immune responses in mammals without significant toxicity. These characteristics have established KLH as one of the most widely used carrier proteins in vaccine development and as a valuable model antigen for the investigation of adaptive immune responses. This review summarizes current knowledge on the biological origin, molecular structure, biosynthesis, and post-translational processing of KLH, with particular emphasis on its unique glycan architecture and its contribution to immunogenicity. Advances in glycomic and structural analyses have revealed an extraordinary diversity of N-linked glycans that distinguish KLH from mammalian glycoproteins and play a central role in immune recognition. The review further discusses methods for KLH isolation, purification, and characterization, as well as its application in experimental and clinical immunology as a standardized tool for assessing antigen-specific immune responses. In addition, the therapeutic and translational potential of KLH is examined across multiple biomedical fields. Particular attention is given to its use as a carrier protein in conjugate vaccines, its role in cancer immunotherapy, and its emerging applications in the development of vaccines and immunotherapeutic strategies targeting neurodegenerative diseases, atherosclerosis, and substance use disorders. Collectively, the available evidence highlights KLH as a unique marine-derived biomolecule that bridges glycobiology, immunology, and translational medicine, and continues to serve as an important platform for the development of next-generation immunotherapeutics and vaccine technologies.