Proteolysis of acute-phase proteins leads to generation of immunomodulatory and anti-inflammatory peptides. The possible involvement of these compounds and the parent proteins in the body's defense mechanisms are being investigated. Studies are directed toward isolation of bioactive peptides from physiological sources, structural elucidation, synthesis, scope and mode of function, structure-function relationships, antibacterial and antitumor activities, potential clinical implications, diagnoses of human diseases, and application to the preparation of synthetic vaccines. The investigation of biosynthesis, metabolism, application to human therapy, total synthesis, and structure-function studies of neuropeptides are in progress. Mechanisms of microbial killing, development of potent related drugs and isolation of novel antibacterial-antiviral peptides from natural sources are also being investigated.