An Algae Virus Was Just Found in Humans, and It May Be Messing With Our Brains

A team of researchers was recently surprised to come across a virus that usually affects algae in the throats of humans. What's more, they found a potential link between people infected with the virus and a subtle change in cognitive function.

The virus known as ATCV-1 began popping up only recently. A number of years ago, it was found in some human brain tissue samples, according to an article in Science, though researchers then were unsure if it had infiltrated before or after the subject had died. More recently, a group of Johns Hopkins University researchers found traces of it in throat cultures taken from psychiatric patients. At first, they had no idea what it was.

It was only after consulting a viral database did they discover that it was ATCV-1, a peculiar find given that ATCV-1 is what's known as a chlorovirus. Chloroviruses are an unusual sort of plant virus typically targeting algae. For one thing, they're among the largest plant viruses known to humans, with up to 600 protein-encoding genes (vs. less than a dozen for most plant-targeting viruses). As such, they're known to act more like bacteria than proper viruses, forming large plaques around their unicelluar algal targets.

So what are they doing in human throats? The Hopkins researchers, led by virologist Robert Yolken (of cat mind-control parasite fame), immediately set about getting to the bottom of this unexpected viral mystery. They turned to another study in progress, this one investigating cognitive functioning in a group of 92 healthy subjects.

Forty-three percent of the group were found to be hosting the virus and, what's more, they showed about a 10 percent handicap in tests involving visual processing. Described in this week's edition of the Proceedings of the National Academy of Sciences, that's not in itself a huge finding, but the Hopkins team looked deeper.

Next, they injected the virus into the mouths of lab mice, and both infected and uninfected mice (as determined by the presence of antibodies to the virus) were subjected to an array of functioning tests.

As with the human group, the infected mice showed cognitive deficits, performing poorly on spatial and visual processing tasks and exhibiting behaviors associated with distractibility and shorter attention spans. They had created stupid mice, it seemed, or at least mice that had a harder time with some tasks.

"The similarity of our findings in mice and humans underscores the common mechanisms that many microbes use to affect cognitive function in both animals and people," noted co-investigator Mikhail Pletnikov in a statement provided by Johns Hopkins. "This commonality is precisely what allows us to study the pathologies that these microorganisms fuel and do so in a controlled systematic way."

Finally, the team looked at the mouse brain tissue itself. There were effects on multiple genes found in the hippocampus, particularly those responsible for memory and spatial orientation. Some changes overlapped with genes involved in immune system regulation and genes responsible for the production of the neurotransmitter dopamine. In all, 1,300 genes were affected.

It's unclear as to whether or not the virus actually infects humans (or mice) or if it just hangs out in a more parasitic mode. In this sense, it could be a bit more like the infamous cat-based parasite Toxoplasma gondii than what we'd usually associate with a virus invader. It's also unclear as to whether or not this infection or quasi-infection is common outside of Hopkins' Baltimore, Maryland base of operations.

In the meantime, there are plenty of other viruses loose in the world to worry about. While a superspecialized virus jumping from green algae to humans is a bit startling, it hardly seems dangerous, at worst the faintest nudge in neural development in a world of much, much larger forces.