Innate signaling by mycobacterial cell wall components and relevance for development of adjuvants for subunit vaccines.

Introduction: Pathogen recognition receptors (PRRs) recognize pathogen-associated molecular patterns, triggering the induction of inflammatory innate responses and contributing to the development of specific adaptive immune responses. Novel adjuvants have been developed based on agonists of PRRs. Areas covered: Lipid pathogen-associated molecular patterns (PAMPs) present in the cell wall of mycobacteria are revised, with emphasis on agonists of C-type lectin receptors, signaling pathways, and preclinical data supporting their use as novel adjuvants inducing cell-mediated immune responses. Their potential use as lipid antigens in novel tuberculosis subunit vaccines is also discussed. Expert commentary: Few adjuvants are licensed for human use and mainly favour antibody-mediated protective immunity. Use of lipid PAMPs that trigger cell-mediated immune responses could lead to the development of adjuvants for vaccines against intracellular pathogens and cancer.