Novel Vaccine Delivery Systems

Vaccine is a material that induces an immunologically mediated resistance to a disease but not necessarily an infection. Vaccines are generally composed of killed or attenuated organisms or subunits of organisms or DNA encoding antigenic proteins of pathogens. Vaccines though exceptionally selective and specific in reacting with antibodies often fail to show reactions in circumstances such as shifts in epitopic identification center of antibody and are poorly immunogenic. These vaccines require boosting with agents called adjuvants in order to induce an effective immunity. Adjuvants potentiate the immunostimulatory property of the antigen and are non-immunogenic, nontoxic, and biodegradable in nature.

Conventional immunization regimen involves prime doses and booster doses. Immunization failed as patients neglect the booster doses. These reasons necessitated the development of new generation of prophylactic and therapeutic vaccines to promote effective immunization. Vaccines allow for the incorporation of doses of antigens so that booster doses are no longer necessary as antigens are released slowly in a controlled manner. Attempts are being made to deliver vaccines through carriers as they control the spatial and temporal presentation of antigens to immune system thus leading to their sustained release and accurate targeting. Carrier systems such as liposomes, microspheres, nanoparticles, dendrimers, micellar systems, ISCOMs, plant-derived viruses are being investigated and developed as vaccine delivery systems