The trouble is, B cells can detect invading pathogens only as long as they are outside of cells. Harnessing the killer T cells' power for vaccination has been difficult, says Starnbach, because they require that the antigens against which they act be displayed to them from inside infected cells. And delivering a vaccine into cells is much more complex than simply injecting it into a person's bloodstream. Armed with this technology, the researchers genetically fused a harmless snippet of the anthrax toxin to a snippet of their model pathogen required to stimulate T cells but unable to cause full-blown disease. Then they mixed this construct with the transporter component of the anthrax toxin and injected it into mice.
Much work remains to be done, however, before the researchers can claim victory.
For starters, they need to test if their vaccine can protect against death, not just reduce bacterial load, and whether it can do so in diverse strains of mice, not only the inbred strain that was studied. These are necessary steps toward testing a vaccine in humans. Next they need to apply their method to more medically important pathogens than the bacteria used in this study. First candidates could be the cytomegalovirus that causes retinitis in people with AIDS, and the bacterium that causes dysentery, says Starnbach. It may seem ironic to us that we should allow any part of Bacillus anthracis into our bodies to protect us from disease.