Although it has been proposed that they exert their adjuvancity by generating a depot effect at the injection site, currently, other action mechanism have been found which better explain the modulation or improvement of the immune response. Carriers

can be passively directed and subsequently endocyted by APCs and deliver the antigen to the cytosol or intracellular organelles. In addition, they can interact with protein complexes, such as inflammasome, to activate immune response. Furthermore, they can incorporate other immunostimulatory molecules which may improve or modulate the immune response Inhibitors,research,lifescience,medical in order to develop not only humoral but also cellular immunity. Delivery systems also possess other advantages; they are safe, stable, and reproducible. Besides, they can be administered by several routes, which Inhibitors,research,lifescience,medical offer the possibility of developing both mucosal and systemic immune responses. All these features have led to the approval of some of these systems to clinical use, such as VLPs, IWP-2 in vitro virosomes, or traditional alum. Although these adjuvants are able to trigger appropriate immune responses against certain pathogens, the future in this field will be focused on the development of combined vaccines to better design the induction Inhibitors,research,lifescience,medical of an appropriate immune response. Acknowledgments This project was partially supported by the “Ministerio de Ciencia e Innovación” (SAF2007-66115)

and FEDER funds. A. Salvador thanks the “Universidad del País Vasco” for the Fellowship Grant. Abbreviations APCs: Antigen-presenting cells ASC: Apoptosis-associated speck-like protein BCG: Bacillus Calmette-Guerin BPV: Bovine papillomavirus BSA: Bovine serum albumin CoV: Coronavirus CpG: Cytosine-phosphorothioate-guanine

Inhibitors,research,lifescience,medical CTL: Cytolytic immune response DCs: Dendritic cells HBsAg: Hepatitis B surface antigen HIV: Human immunodeficiency virus HMGB1: High-mobility group box 1 IFN: Interferon IL: Interleukin IP: Inducible Inhibitors,research,lifescience,medical protein ISCOMs: Immunostimulatory complexes IUV: Intermediate unilamellar vesicles LCMV: Lymphocytic choriomeningitis virus LUV: Large unilamellar vesicles MHC: Major histocompatibility complex MLV: Multilamellar vesicles MPL: Monophosphoril lipid A MPs: Microparticles MUC1: Human mucin-1 NKT cells: Natural killer T cells NLR: Nod-like receptor NLRP3 or NALP3: NOD-like receptor protein 3 NPs: Nanoparticles o/w: Oil in water OVA: Ovalbumin Mannose-binding protein-associated serine protease PAMPs: Pathogen associated molecular patterns PLGA: Poly(D,L-lactic-co-glycolic) acid PLUSCOMs: Cationic immune stimulating complexes Poly(I:C): Poly(inosinic-cytidilic) acid PRRs: Pathogen recognition receptors RAD: arginine-alanine-aspartame RGD: arginine-glycine-aspartate RLR: Rig-like receptor RNA: Ribonucleic acid SARS: Severe acute respiratory syndrome SUV: Small unilamellar vesicles TLR: Toll like receptor TRP2: Tyrosinase-related protein 2 VLPs: Virus like particles w/o: Water in oil WGA: Lectin weat germ agglutinin.