Tuesday, July 13, 2010

'Cool' vaccines

We all know the usefulness of certain thermophiles (I'm looking at you, Taq polymerase), but up here in Canada, with our vast arctic tundra, we should be looking for uses for cold-loving organisms - a resource we're more likely to have in abundance.

A group at the University of Victoria has done just that, using genes psychrophilic bacteria to develop temperature-sensitive vaccines.
One at a time, the team swapped out nine so-called essential genes—involved, for instance, in DNA repair or cell division—in F. novicida for their counterparts from Arctic bacteria, such as Colwellia psychrerythraea, a marine microbe that lives in polar waters and ice. Francisella normally dies at 45˚C; introducing the cold-loving genes lowered that threshold by up to 12˚C, depending on the gene and the species it was borrowed from.

When the researchers injected these altered strains into the relatively cool tails of rats, they found that the microbes reproduced locally but didn't spread to the warmer spleen and lungs, where they would normally replicate as well. The key test was whether the strains could act as vaccines. F. novicida is lethal to mice, but when the researchers injected the temperature-sensitive strains, the animals didn't get sick—and they were protected from an otherwise fatal dose of the unaltered F. novicida given 3 weeks later. [Source]
The idea for a temperature-sensitive vaccine is already out there, with a particular flu vaccine capable of replicating in the throat and nose, but not the lungs. The goal is to create safer live vaccines, but could be put to other uses such as study of dangerous pathogens by creating versions that can't replicate in the warm human body, possibly reducing the need for the strict containment measures to keep researchers safe.

The full research article is available free from PNAS.