New developments in the field of synthetic muramyl peptides, especially as adjuvants for synthetic vaccines.

MDP (N-acetylmuramyl-L-alanyl-D-isoglutamine), the first synthetic peptidoglycan derivative capable of replacing whole mycobacteria in Freund's complete adjuvant, is highly active in stimulating antibody production. It also produces delayed hypersensitivity and stimulates non-specific resistance. MDP itself is pyrogenic but murabutide (N-acetyl-muramyl-L-alanyl-D-glutamine-n-butyl ester) is not pyrogenic and is undergoing clinical trials. MDP and its derivatives will prove useful as adjuvants, especially for the "new generation" of synthetic vaccines, which will be discussed in detail. They are also interesting for increasing host resistance against various bacterial and parasitic infections and in experimental tumour immunotherapy. MDP and its derivatives, such as murabutide, will also prove useful in combination with chemotherapy, especially for immunodepressed and elderly patients. Some muramyl peptides are also active in prolonging slow wave sleep in rabbits, cats and monkeys. Muramyl peptides are typical bacterial metabolites, which are apparently essential for establishing a normal immune status and slow wave sleep; they thus represent a new category of vitamins.