A furry black llama from Massachusetts named Wally has a very special ability.
Yi Shi, assistant professor of cell biology at Pitt, led a team that immunized Wally with a piece of SARS-CoV-2 spike protein. After waiting about two months, Wally’s immune system created minuscule, mature nanobodies that neutralize the virus that causes Covid-19.
Research published today in Science shows a new technique for extracting these tiny yet powerful antibody fragments from llama blood. These nanobodies could then be aerosolized into a mist and inhaled directly into the lungs to prevent and treat Covid-19.
They’re so effective because they’re so much smaller than human antibodies and more stable, scientists say.
“Nature is our best inventor,” said Shi. “The technology we developed surveys SARS-CoV-2 neutralizing nanobodies at an unprecedented scale, which allowed us to quickly discover thousands of nanobodies with unrivaled affinity and specificity.”
Yufei Xiang, a researcher at Shi’s lab, used a mass spectrometry-based technique that Shi has been perfecting for the last three years to identify the nanobodies in Wally’s blood that bind to SARS-CoV-2 most effectively.
Shi happens to have a lab right next door to Pitt’s Center for Vaccine Research.
“As we see each other, we chat about science often,” said Dr. Paul Duprex, director of the center. “And that’s why science works — by communicating and talking about new ideas. So we were really excited when we saw the potential of his discovery. And we got to work.”
Back in February, the Center for Vaccine Research was among the first in the nation to receive live samples of the SARS-CoV-2 virus, directly from the Centers for Disease Control and Prevention. They also received samples from from Munich from one of the first cases in Europe.
“We mixed a minuscule amount of his best nanobodies together with that live virus from that Munich patient, and then we added a few drops of that solution to the plate of cells,” said Duprex. “Eventually, after a couple of days, we measured how those antibodies neutralized the virus and how many cells survived.
“What we found was really remarkable. Just a minuscule fraction of those nanobodies could neutralize enough particles of SARS-CoV-2 to protect millions of cells.”
In fact, just a fraction of a nanogram could neutralize enough SARS-CoV-2 to keep a million cells from becoming infected.
This idea of using llamas didn’t come out of nowhere. There are actually others who have suspected that llama antibodies could help unlock the mystery of how to fight Covid-19. These particular antibodies, however, represent the most effective therapeutic candidates — and appear hundreds or even thousands of times more effective than the others, the researchers claim.
These nanobodies can stay stable at room temperature for six weeks, and be transformed into a mist that can be inhaled directly into the lungs, where it’s most needed. They find and latch onto the virus in the respiratory system, before it has a chance to do any damage.
Together with Cheng Zhang at Pitt, and Dina Schneidman-Duhovny at the Hebrew University of Jerusalem, the researchers found that their nanobodies use a number of mechanisms to block SARS-CoV-2. That makes them perfect for bioengineering. That will come in handy if the virus mutates or becomes drug resistant.
Most antibody treatments for Covid that are being developed require an IV, which, which in turn, requires a larger dose to dilute it throughout the body. They also typically costs $100,000 per treatment.
“Nanobodies could potentially cost much less,” said Shi. “They’re ideal for addressing the urgency and magnitude of the current crisis.”
“As a virologist, it’s incredible to see how harnessing the quirkiness of llama antibody generation can be translated into the creation of a potent nano weapon against clinical isolates of SARS-CoV-2,” said Duprex.