Imagine that you have a devastating heart infection that won’t respond to medication. For one 76-year-old man, that nightmare was his reality. Following surgery for an aortic aneurysm — which makes the heart’s main artery swell to almost twice its normal size — a nasty bacterial infection caused by the microbe Pseudomonas aeruginosa had taken over.
Beyond that, the bacteria in his body slowly became resistant to even massive doses of antibiotics. The septic infection became so bad that a cavity grew in the patient’s chest; drainage began to erode his aorta, making surgery highly risky. Desperate, the patient and his doctors tried an experimental treatment that would become known as “phage therapy.” In January 2016, doctors injected him with a mixture of antibiotics and hundreds of millions of viruses called OMKO1 that were found in a pond in Connecticut.
The idea was that this virus would target efflux pumps that P. aeruginosa had evolved to spit out bacteria-killing drugs. The bacteria would then evolve new resistance to the virus by deleting these pumps — but this selection would make the pathogen susceptible to antibiotics again.
It worked. Four weeks after the injection, the patient had unrelated surgery, and doctors found no trace of P. aeruginosa. A case study was published in 2018, and Paul Turner, an evolutionary biologist at Yale University who worked on the case, says he has since treated 13 patients using phage therapy. All 13 have recovered, although the results are still pending publication.
Phage therapy highlights just one of the many ways viruses can — and do — benefit humans. In the middle of the COVID-19 pandemic, people are understandably furious at the coronavirus responsible for such widespread destruction and death. It’s remarkable, and tragic, that something so tiny can gain such a tremendous foothold on our society. But not everything viruses do are inherently harmful.
The Good Ones
In many cases, we’ve been able to wrangle viruses to do our bidding. Thanks to their unique ability to worm into DNA, viruses can be used to inject genes into cells, which can reverse some genetic diseases. For example, some viruses have been able to cure hemophilia, a blood disorder that prevents clotting.
Viruses have also helped illuminate how the human mind works, using a technique called optogenetics. It involves the use of viruses that have been genetically modified with light-sensitive cell receptors lifted from green algae.
When injected into the brain, these viruses are able to modify the DNA of specific neurons, allowing them to be switched on or off by flashing those brain cells with blue light. By observing what happens when these switches are thrown, neuroscientists have developed new theories on how things like depression and addiction become ingrained in the brain.
The Next Generation of Drugs?
Phage therapy is actually protect against intestinal damage caused by antibiotics.
One day, this could lead to therapies or technology to help humans live in better harmony with viruses. “They’re not like these things that are conscious entities that are nefarious and trying to plot your demise,” Cadwell says. “They’re basically tiny robots that are trying to make copies of themselves. Whether or not the host gets sick is kind of more on us than them.”