Airborne and potentially deadly, the virus that causes COVID-19 can only be studied safely under high-level biosafety conditions. Scientists handling the infectious virus must wear full-body biohazard suits with pressurized respirators, and work inside laboratories with multiple containment levels and specialized ventilation systems. While necessary to protect laboratory workers, these safety precautions slow down efforts to find drugs and vaccines for COVID-19 since many scientists lack access to the required biosafety facilities, according to a report from Washington University School of Medicine in St. Louis.
To help remedy that, researchers have developed a hybrid virus that will enable more scientists to enter the fight against the pandemic. The researchers genetically modified a mild virus by swapping one of its genes for one from SARS-CoV-2, the virus that causes COVID-19. The resulting hybrid virus infects cells and is recognized by antibodies just like SARS-CoV-2, but it can be handled under ordinary laboratory safety conditions. The study is available online in Cell Host & Microbe.
Viruses have proteins on their surfaces that they use to latch onto and infect cells. The researchers removed VSV’s surface-protein gene and replaced it with the one from SARS-CoV-2, known as spike. The switch created a new virus that targets cells like SARS-CoV-2 but lacks the other genes needed to cause severe disease. They dubbed the hybrid virus VSV-SARS-CoV-2.
Using serum from COVID-19 survivors and purified antibodies, the researchers showed that the hybrid virus was recognized by antibodies very much like a real SARS-CoV-2 virus that came from a COVID-19 patient. Antibodies or sera that prevented the hybrid virus from infecting cells also blocked the real SARS-CoV-2 virus from doing so; antibodies or sera that failed to stop the hybrid virus also failed to deter the real SARS-CoV-2. In addition, a decoy molecule was equally effective at misdirecting both viruses and preventing them from infecting cells.
The hybrid virus could help scientists evaluate a range of antibody-based preventives and treatments for COVID-19. The virus could be used to assess whether an experimental vaccine elicits neutralizing antibodies, to measure whether a COVID-19 survivor carries enough neutralizing antibodies to donate plasma to COVID-19 patients, or to identify antibodies with the potential to be developed into antiviral drugs.
