DNA vaccines

This is an innovative approach to vaccination that has grown out of the concept of gene therapy; the expression of novel proteins within a host, from extraneous gene sequences. DNA sequences encoding antigenic portions of viruses (protective antigens) are inserted into a plasmid, which can be injected into the host as naked DNA free of protein or nucleoprotein complexes. The host cells can take up the DNA and may express the virally encoded proteins through their own transcription and translation procedures. Such vaccines theoretically stimulate strong cytotoxic T-cell responses as DNA derived from bacteria (i.e. the plasmid itself) promotes helper T-cell cytokine production. Experi- mental influenza vaccines in animals have proved effective in challenge experiments and clinical trials are underway with DNA vaccines for HIV, but as yet these are some way from approved clinical use.