Viruses pass notes to each other to decide if they should go for the kill, study finds

One of the strengths of a virus is that it can multiply dramatically using a living cell. But the growth of a virus is also tied to death: to produce more of itself, a virus usually must hijack the cell’s machinery until its host explodes.

Now a new study published in Nature suggests that viruses can talk to each other about whether to kill a host cell at all, using protein levels around them to indicate how many other host cells they’ve already killed off. Researchers at the Weizmann Institute of Science in Rehovot, Israel found that rising levels of a particular protein, released when those cells burst open, could halt a virus’ attack and cause it to temporarily lie dormant in those cells instead.

The discovery of such a communication system, the researchers suggested, could mean the development of a new type of anti-viral medication.

“If you had a molecule that could drive viruses into complete latency, it would be a good drug,” microbial geneticist Rotem Sorek, who led the research team, told Nature.

The researchers didn’t initially go looking for gossipy viruses. In fact, they were looking for the opposite: They thought bacteria might be communicating through similar chemicals about viral attacks. But in examining that behavior, Sorek’s team found that a type of virus, a bacteriophage called phi3T, which infects Bacillus subtilis bacteria, stopped killing the bacteria after many of the host cells had died.

At that point, the phages stopped multiplying inside those cells and inserted a copy of their genetic code into the cell’s own before going quiet.

According to Nature, Sorek’s team spent two and a half years trying to find the answer: As each phage multiplied inside a bacterium, the dying host cell released a protein they named arbitrium when it burst. Those proteins acted almost like notes from those phages to others inside still-intact host cells, stopping them from killing all their hosts at once.

Other scientists told Nature that the paper’s evidence of communication between viruses was “transformative.”

“It does make a lot of sense,” Peter Fineran, a microbial geneticist in New Zealand, told Nature. “If the phage is running out of hosts, it would try and limit its destruction, and sit quiet and wait for the host to re-establish growth.”

But the research into such viral communication is just beginning, Sorek said. “Phages broadcast in different frequencies. They speak in different languages and they can hear only the language that they speak,” he said.

This story was originally published January 23, 2017 at 6:36 AM with the headline "Viruses pass notes to each other to decide if they should go for the kill, study finds."