The strains of E. coli are part of a new class of biological "adjuvants" that is poised to transform vaccine design.
Adjuvants are substances added to vaccines to boost the human immune response.
"For 70 years the only adjuvants being used were aluminium salts," said Stephen Trent, associate professor of biology at the College of Natural Sciences, University of Texas-Austin, the journal Proceedings of the National Academy of Sciences reports.
"They worked, but we didn't fully understand why, and there were limitations. Then four years ago the first biological adjuvant was approved by the Food and Drug Administration (FDA).
"I think what we're doing is a step forward from that. It's going to allow us to design vaccines in a much more intentional way," said Trent, according to a Texas statement.
Adjuvants were discovered in the early years of commercial vaccine production, when it was noticed that batches of vaccine that were accidentally contaminated often seemed to be more effective than those that were pure.
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"They're called the 'dirty little secret' of immunology," said Trent.
"If the vials were dirty, they elicited a better immune response."
For about 70 years the adjuvant of choice, in nearly every vaccine worldwide, was an aluminium salt.
Then in 2009, the FDA approved a new vaccine for human papillomavirus (HPV). It included a new kind of adjuvant that's a modified version of an endotoxin molecule.
These molecules, which can be dangerous, appear on the cell surface of a wide range of bacteria.
As a result, humans have evolved over millions of years to detect and respond to them quickly. They trigger an immediate red alert.