Recombinant vector vaccines for the prevention and treatment of HIV infection

A number of gene-based vectors have been tested to deliver HIV-1 antigens to immune systems as vaccines. While many challenges remain, a number of promising results have recently been observed to re-energize the HIV vaccine field. Naked DNA vaccines using plasmids as vectors have suffered from low efficiency, but have recently been improved using approaches such as electroporation to improve transfection. Another approach is to use viruses as gene delivery vehicles. These have the advantage of naturally evolved infection efficiency, but have issues with immune responses and being biohazards. Particularly promising viral vectors are those based on low seroprevalence adenovirus vectors and those based off of poxviruses. These naked and viral vectors have most effectively been applied as prime-boost strategies to avoid vector-induced immunity that occurs each time a virus vaccine is used. These immune evasion approaches include serotype switching, vector switching and shielding vectors with polymers like polyethylene glycol (PEG). Effective prophylactic HIV vaccines will likely need to provide barrier protection at mucosal sites of entry of the virus when there are fewer virions and they are at most risk from immune rejection. For mucosal protection to occur, better mucosal vaccines and challenge models will be needed.