Public healthDesigner bacteria show way for better vaccines

Researchers at the University of Texas at Austin have developed a menu of sixty-one new strains of genetically engineered bacteria that may improve the efficacy of vaccines for diseases such as flu, pertussis, cholera, and HPV.

A University of Texas at Austin release reports that the strains of E. coli, which were described in a paper published this month in the journal PNAS, 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 seventy years the only adjuvants being used were aluminum salts,” said Stephen Trent, associate professor of biology in the College of Natural Sciences. “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. 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.”

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.

“They’re called the ‘dirty little secret’ of immunology,” said Trent. “If the vials were dirty, they elicited a better immune response.”

What researchers eventually realized was that they could produce a one-two punch by intentionally adding their own dirt (adjuvant) to the mix. The main ingredient of the vaccine, which was a killed or inactivated version of the bacteria or virus that the vaccine was meant to protect against, did what it was supposed to do. It “taught” the body’s immune system to recognize it and produce antibodies in response to it.

The adjuvant amplifies that response by triggering a more general alarm, which puts more agents of the immune system in circulation in the bloodstream, where they can then learn to recognize the key antigen. The result is an immune system more heavily armed to fight the virus or bacteria when it encounters it in the future.

The release notes that for about seventy years the adjuvant of choice, in nearly every vaccine worldwide, was an aluminum 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