Andes Hantavirus Attachment Mystery Solved by Scientists

The Andes hantavirus attachment mystery just got solved, and it matters because this is the only hantavirus known to spread from person to person. According to Phys.org, scientists have finally shown how the Andes hantavirus grabs onto human cells, a finding that could lead to the first real treatments.

Why this virus is back in the news

Earlier this year, an outbreak of Andes hantavirus on a cruise ship killed three passengers and sickened thirteen. That outbreak exposed a scary gap: there are no approved vaccines or treatments for the virus. The World Health Organization tracked the cluster in a series of outbreak reports, noting that human-to-human transmission happened on board.

Hantaviruses are a big family of viruses carried mostly by rodents. People usually catch them by breathing in airborne particles from rodent urine, droppings or saliva. They can cause hantavirus pulmonary syndrome, a severe respiratory illness that can quickly lead to breathing failure.

Of the more than twenty hantaviruses known to make people sick, Andes is the only one known to pass between people, typically through close and prolonged contact. That is why the cruise ship cluster felt like such a wake-up call for health officials.

The doorway the virus uses

The research team, from Albert Einstein College of Medicine, Institut Pasteur and LSU Health Shreveport, had already shown that the virus needs a protein on the cell surface called PCDH1. Think of it as a doorway: the virus latches on, enters the cell and then multiplies inside.

What nobody knew was exactly how the virus's spike protein grabbed that door handle. "Eight years ago, we discovered that Andes virus infects human cells by using a particular protein on the cell's surface, called a receptor, but we couldn't figure out exactly how the virus recognized it," said co-corresponding author Kartik Chandran, as quoted by Phys.org.

A square spike and a deep pocket

Here is the weird part. The spike on SARS-CoV-2 has three identical units forming a triangle, and each unit can bind its receptor on its own. The Andes spike is built from four identical units locked into a square, and a single unit cannot bind alone. The whole square is needed to catch PCDH1.

To see this, the team used cryo-electron microscopy, an imaging method that captures molecules in sharp detail. They also used an artificial intelligence designed scaffold so the square spike would hold together in a test tube. The published paper in Nature describes the structure of the receptor bound to the spike.

The pictures showed one PCDH1 molecule tucked into a deep pocket at the center of the spike. "The best way to prove a rare bird exists is to take a picture of it," said Pablo Guardado-Calvo of the Institut Pasteur, according to Phys.org.

How the virus dodges antibodies

The depth of the pocket helps the virus hide. PCDH1 is long and slender, so it can reach deep inside, but most antibodies are too bulky to follow. Rohit Jangra of LSU Health Shreveport explained that the same pocket can fit the receptor while restricting antibody access.

The team studied several antibodies taken from hantavirus patients. Some bind near the entrance of the pocket and block PCDH1, but none can fit as deep as the receptor does. Chandran described it as a kind of molecular friend-or-foe system: the virus can mutate to escape antibodies without changing how it binds its receptor.

What could come next

That escape trick is also a weakness. Human antibodies are limited to a certain shape, but scientists can design long and skinny molecules that slip into the pocket and block it. The researchers say this offers a blueprint for new antiviral medicines.

The approach could also help against Sin Nombre virus, a close relative found in the United States and Canada. The Nature paper notes that these New World hantaviruses can have case-fatality rates approaching forty percent, so the stakes are real.

None of this is a cure yet. It is a structural map, and turning it into a drug will take time and funding. Still, after a year when a cruise ship became a hantavirus hotspot, a clear picture of the virus's weak point is the kind of science news worth sharing. For more, browse our health coverage.