Marine-derived polysaccharides and peptides as next-generation immunomodulators: Molecular mechanisms, therapeutic...

Marine-derived polysaccharides and peptides have emerged as innovative immunomodulatory agents offering distinct structural features and multimodal biological activities not commonly found in terrestrial sources. Environmental pressures in marine ecosystems drive the evolution of diverse sulfated polysaccharides, antimicrobial peptides, and bioactive macromolecules capable of modulating both innate and adaptive immune responses. Polysaccharides such as fucoidan, carrageenan, ulvan, chitin, and chitosan demonstrate potent engagement of pattern recognition receptors, enhancement of antigen presentation, and immunological reprogramming of macrophages, dendritic cells, and natural killer cells. Marine peptides derived from fish, mollusks, and marine microbes combine direct antimicrobial effects with regulation of cytokine balance, T-cell differentiation, and tissue repair pathways. Synergistic strategies integrating polysaccharides and peptides in nanoscale delivery systems and conjugate vaccines show increased immunogenicity and therapeutic benefit across oncology, infectious diseases, and inflammatory disorders. Despite this promise, translation of marine immunomodulators into clinical practice is restricted by structural heterogeneity, limited bioavailability, and a lack of harmonized analytical and regulatory frameworks. Advances in multi-omics technologies, systems immunology, and machine learning, guided design are enabling deeper mechanistic understanding and rational optimization of marine bioactives. Concurrently, the development of sustainable aquaculture, biorefinery systems, and controlled bioprocessing supports scalable and environmentally responsible production. This chapter provides the recent molecular insights, therapeutic opportunities, and emerging translational strategies for marine-derived polysaccharides and peptides, while outlining key challenges and future priorities. Together, these innovations position marine immunomodulators as promising candidates for next-generation immunotherapy, vaccine adjuvant development, and global health applications.