Rehydration therapy

MAKING vaccines often involves growing bugs—and these days the bugs in question are frequently genetically modified. There are, with good reason, strict regulations about the use and transport of such modified organisms, for fear that something bad might escape and thrive in the wild. And this has led to vaccine-producing bugs being grown in secure, centralised “foundries”, whence their products are distributed to the wider world.

That works well when the relevant bits of the wider world have decent infrastructure for handling vaccines—particularly networks of reliable refrigerators, known as cold chains, to keep them stable. But this is not always so, especially in certain parts of the tropics, where vaccines are often needed most. So it would be nice to have a safe and robust way of making vaccines on site in such places, thereby shortening the cold chain. And, as he reports in Cell, James Collins of the Massachusetts Institute of Technology thinks that he may have developed one.

The fear of an engineered bug escaping and thriving does not extend to bits of bugs, since these cannot reproduce by themselves. Dr Collins therefore set himself the task of assembling a vaccine factory consisting only of the cellular components needed to synthesise the pertinent molecules, rather than of whole cells—and doing so in a way that could be freeze-dried for easy transport and storage.

He knew from previous work on these components that it was possible to isolate and freeze-dry them individually in ways that permitted them to be reactivated by the addition of water. What he did not know was whether they could then be assembled into something that would yield medically useful proteins if provided with the appropriate DNA.

Building on the previous work, he and his colleagues studied how solutions containing rehydrated protein-production machinery responded when given DNA templates that encoded (among other things) the antigens used to make vaccines against anthrax, botulism and diphtheria. All were readily turned out by the rehydrated cellular machinery.

In the case of diphtheria they also tried exposing their antigens to the antibodies which need to bind to them in order to let the immune system develop resistance. Such binding, they found, took place—meaning antigens produced this way might, in principle, be used as a vaccine. Given that diphtheria vaccine is extremely sensitive to temperature and is thus one of the most challenging to distribute to remote places, this is an encouraging result. If it can be commercialised, the process of vaccine manufacture and distribution might be greatly simplified.