No approved treatment or vaccine for SARS-CoV-2 exists yet. However, scientists at Germany's EMBL in Hamburg have identified a synthetic mini-antibody called a "sybody" that neutralizes the virus in lab tests, offering hope for new therapies.
Since the COVID-19 pandemic began, labs worldwide have raced to develop treatments and vaccines. In a study published in Nature Communications on November 4, 2020, researchers from the European Molecular Biology Laboratory (EMBL) in Hamburg, Germany, highlight a breakthrough: a small synthetic antibody, or "sybody," capable of neutralizing SARS-CoV-2 in the lab.
SARS-CoV-2 enters human cells via the ACE2 receptor, using its receptor-binding domain (RBD) protein as the key. The strategy is straightforward—develop a molecule that binds more tightly to RBD than to ACE2, blocking viral entry. Antibodies, produced by immune cells to neutralize pathogens, are a leading option in ongoing clinical trials.
Studies of antibodies from recovered patients show not all are equally effective, and producing them at scale is costly and complex. EMBL researchers turned to nanobodies—tiny antibodies found in camels and llamas. Prior work demonstrated nanobodies can block RBD-ACE2 binding and neutralize the virus.
Isolating nanobodies typically involves immunizing animals, but synthetic nanobody libraries (sybodies) enable faster, cheaper screening. The team identified a top candidate from one such library.
The researchers screened sybodies for RBD binding. From 85 candidates, sybody #23 (Sb23) showed exceptional stability and potency. Further tests on 36 sybodies revealed 11 that neutralized a pseudovirus (a harmless lentivirus with RBD). Sb23 excelled, binding effectively across all RBD conformations—'up,' 'down,' open, or closed.
This discovery took just three weeks. Traditional nanobody production via llamas or camels requires animal immunization (six weeks minimum) and totals four months. Next, the team plans to test Sb23's efficacy in humans.
