(CN) — Researchers in Sweden have identified a small neutralizing antibody that has the capacity to block the SARS-CoV-2 virus, which causes Covid-19, from entering human cells. In a paper published Friday in Nature Communications, the researchers propose that the nanobody has the potential to be developed as an antiviral treatment.
Single-domain antibodies, also known as nanobodies, are fragments of antibodies that occur naturally in camelids such as camels, alpacas and llamas. Unlike the antibody molecules in most species, camelid antibodies are very specific and can be broken down into nanobodies which target a specific molecule and bind to it. If the nanobody binds to a viral protein, it can be used as a drug to fight the virus.
Nanobodies span less than one-tenth the size of conventional antibodies and are typically easier to produce cost-effectively at scale. Critically, they can be adapted for humans with current protocols and have a proven record of inhibiting viral respiratory infections.
This is the case with the nanobody sequence that researchers from the Karolinska Institutet, Sweden’s largest center of medical academic research, call Ty1 — named after the alpaca Tyson. Ty1 efficiently neutralizes the virus by attaching itself to the part of the spike protein that binds to the receptor ACE2, which is used by SARS-CoV-2 to infect cells. This blocks the virus from slipping into the cells and thus prevents infection.
The team began seeking effective nanobodies in February when an alpaca was injected with the SARS-CoV-2’s spike protein, which is used to enter our cells. After 60 days, blood samples from the alpaca showed a strong immune response against the spike protein.
The team then cloned, enriched and analyzed nanobody sequences from the alpaca’s blood cells to determine which nanobodies should be examined. They found that Ty1 can bind to the SARS-CoV-2 spike protein and neutralize the virus, with no detectable off-target activity.
Preclinical animal studies have begun to investigate the neutralizing activity and therapeutic potential of Ty1 in living creatures.
“We hope our findings can contribute to the amelioration of the Covid-19 pandemic by encouraging further examination of this nanobody as a therapeutic candidate against this viral infection,” said Gerald McInerney, corresponding author and associate professor of virology at the Department of Microbiology, Tumor and Cell Biology at Karolinska Institutet.