An image of a bacteriophage, one of the viruses used in the research. Via Flickr/Carl Wirth
Biologists at Portland State University have discovered a way to make “zombie” or “fossilized” viruses that could potentially survive transport over long distances without a host. It might sound scary, but it's a good thing. Not only could it explain some puzzling data on virus distribution, it also has implications for the search for life on other planets, and could provide a new way to preserve vaccines.
In a new study in the Journal of Virology, the researchers looked at what happened when they coated known viruses with silica, effectively encasing them in a protective shell. The point was to investigate virus distribution. Of course, viruses are often transported by hosts (like humans spreading the flu virus around by sneezing all over each other), but that’s not necessarily always the case. "Interestingly, local hot spring virus dispersal can result from aerosolization by fumaroles, indicating at least one possible host-independent dispersal mech- anism," the authors wrote in the paper's introduction. Essentially, viruses that live in hot springs could be dispersed into new ecosystems by geysers or volcanic activity, without the need for a carrier.
The report went on to explain that while bacteria and fungi have been known to travel all the way from the Sahara Desert to the Caribbean Sea on the wind, this doesn’t happen that much with viruses, because they're too sensitive to drying out. “However, if viruses could be reversibly coated in a protective coat in addition to their capsid, they could potentially spread very widely,” they posited. Viruses can be naturally coated by silica in hot springs, so it was an obvious choice of compound to test the theory.
The scientists coated different types of virus in silica, and found that for the most part it made them inactive. When the silica coating was removed, however, they were once again capable of infecting cells; hence the "zombie" nickname. Additionally, when the viruses were “silicified” in their protective armour, they were more resistant to dehydration, which could explain how they might travel over long distances—such as when they're shot out of hot springs—without drying out.
A cartoon of a "zombie" bacteriophage T4, by Jennifer Kuo, one of Kenneth Stedman's undergraduate students.
It’s a cool bit of science, and it also has some pretty far-reaching (albeit also quite far-fetched) implications. The study was partly funded by NASA, and could ultimately help in the search for life on other planets. Take Mars: We know there was water on the red planet, but we don’t know if there were ever microbes living off it. Kenneth Stedman, one of the researchers on this study, has posited that there could be silica-coated viruses in the rock record on earth—and if that’s the case, it’s not too much of a leap to suggest that, just maybe, a record of viruses could be preserved in Martian rock too.
Stedman's currently working on how to actually look for viruses in the rock record. I asked him what implications this latest piece of research might have for the search for life on other planets. “Basically, this means that we could find possibly infectious viruses a long way away from their host organisms, so we need to look for viruses as well as hosts,” he said in an email. “This means that we have to develop techniques to identify probably unknown viruses remotely. We are working on the detection of these so-called virus biosignatures.”
Essentially, the idea is to find a way to look for biomarkers in rocks that could show a virus was once there. This is something that’s still in very early stages; we won’t be tracking down viruses on Mars any time soom. “NASA's interest in the project is that we need to develop the technology on Earth to conclusively detect viruses, both extant and extinct, i.e. in the rock record, before we can try and detect them elsewhere,” Stedman explained.
But closer to home, the zombie virus research lends itself to another potential application: vaccine preservation. Vaccines are notoriously tricky to transport, as they spoil if they get too cold or hot—which is a particular problem in developing countries, where they’re often most needed. Stedman's working on a way to use the silica coating technique to help preserve the vaccines until they're needed, and has a patent pending on the process. “If you can reversibly coat vaccines with silica this could protect the vaccines from inactivation,” he said.
The idea of a "zombie virus" has never sounded so appealing.