Salvation in a Snippet of DNA?

Hopes are running high for vaccines made from nothing more than a bit of pathogen DNA. Often known as gene vaccines or "naked" DNA, DNA vaccines turned many heads in 1993, when researchers published the first reports about their ability to stimulate an immune response in mice. Instead of peptides, proteins, or viral vectors, DNA vaccines consist of nothing more than a gene from the pathogen, stitched into a circular stretch of bacterial DNA called a plasmid. In theory, these vaccines are simpler to make and can stimulate a broader immune response because they closely follow the cellular pathway traveled by the real pathogen. But how they work is still mysterious, and none has yet succeeded in a clinical trial.