Editing DNA vaccine (section)

=== Enhancing immune responses ===

==== DNA ====

The efficiency of DNA immunization can be improved by stabilising DNA against degradation, and increasing the efficiency of delivery of DNA into [[antigen-presenting cell]]s.<ref name=Robinson2000 /> This has been demonstrated by coating biodegradable cationic microparticles (such as poly(lactide-co-glycolide) formulated with [[Cetrimonium bromide|cetyltrimethylammonium bromide]]) with DNA. Such DNA-coated microparticles can be as effective at raising CTL as recombinant viruses, especially when mixed with alum. Particles 300&nbsp;nm in diameter appear to be most efficient for uptake by antigen presenting cells.<ref name=Robinson2000 />

==== Alphavirus vectors ====

Recombinant alphavirus-based [[Viral vector vaccine|vectors]] have been used to improve DNA vaccination efficiency.<ref name=Robinson2000 /> The gene encoding the antigen of interest is inserted into the alphavirus replicon, replacing structural genes but leaving non-structural replicase genes intact. The [[Sindbis virus]] and [[Semliki Forest virus]] have been used to build recombinant [[alphavirus]] [[Replicon (genetics)|replicons]]. Unlike conventional DNA vaccinations alphavirus vectors kill transfected cells and are only transiently expressed. Alphavirus replicase genes are expressed in addition to the vaccine insert. It is not clear how alphavirus replicons raise an immune response, but it may be due to the high levels of protein expressed by this vector, replicon-induced cytokine responses, or replicon-induced apoptosis leading to enhanced antigen uptake by dendritic cells.