Model identical to natural
The highly contagious and potentially deadly SARS-CoV-2 virus that causes COVID-19 can only be safely studied under high-level biosafety conditions. Scientists working with the virus must wear personal protective equipment – suits that protect the whole body, and respirators, and work in laboratories with several levels of tightness and specialized ventilation systems. These precautions are necessary to protect laboratory workers and prevent the dangerous virus from entering the environment, but they hinder efforts to find drugs and vaccines for COVID-19, since many scientists do not have access to the necessary biosecurity tools.
To solve this problem, researchers from Washington University School of Medicine in St. Louis have created a hybrid virus that will allow more scientists to join the fight against the pandemic. To do this, they genetically modified a harmless virus by replacing one of its genes with the SARS-CoV-2 virus gene.
The vesicular stomatitis virus (VSV) was taken as the basis of the model. This virus is the workhorse of virological laboratories, because it is quite harmless and easy to manipulate genetically. VSV affects cattle, horses, pigs and sometimes humans, causing a mild, cold-like illness that lasts three to five days.
The resulting hybrid virus infects cells and is recognized by antibodies as SARS-CoV-2, but it is too weak to cause disease, so it can be worked with under normal laboratory conditions.
The authors have already shared the new virus with colleagues from the USA, Argentina, Brazil, Mexico, Canada. There were also requests from scientists from Great Britain and Germany.
Viruses have proteins on the surface that are needed to fix and infect cells. The researchers removed the VSV surface protein gene and replaced it with the SARS-CoV spike protein gene-2. Thus, a new VSV-SARS-CoV-2 virus was created, which has surface spikes characteristic of SARS-CoV-2, but lacks other proteins necessary for the occurrence of severe disease.
Using serum from COVID-19 patients and purified antibodies, the researchers showed that the hybrid virus is often recognized by antibodies as a real SARS-CoV-2 virus obtained from a patient with COVID-19. Antibodies or serums that prevented infection with the hybrid virus also blocked the original SARS-CoV-2 virus; antibodies or serums that failed to stop the hybrid virus also did not contain the real SARS-CoV-2. In addition, the decoy molecule was equally effective at misdirecting both viruses and preventing them from infecting cells.
Do not forget that the human immune system produces antibodies against various viral proteins SARS-CoV-2, but it is the antibodies against the thorn, apparently, that are most important for protection. Thus, if the virus has this spike protein, it is perceived by the immune system as SARS-CoV-2, even if it is not.
The hybrid virus will give scientists the opportunity to evaluate the effectiveness of antibody-based means of prevention and treatment of COVID-19: whether the experimental vaccine causes the production of neutralizing antibodies, whether a patient who has had COVID-19 carries a sufficient amount of neutralizing antibodies to donate plasma to patients with COVID-19, as well as to identify antibodies that can turn into antiviral drugs.
Since the hybrid virus is perceived by the immune system as SARS-CoV-2, but does not cause serious diseases, it is a potential candidate for a vaccine. Animal studies are currently being conducted to evaluate this possibility.
Article by J.B.Case et al. Neutralizing antibody and soluble ACE2 inhibition of a replication-competent VSV-SARS-CoV-2 and a clinical isolate of SARS-CoV-2 is published in the journal Cell Host and Microbe.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of Washington University School of Medicine in St. Louis: Lab-made virus mimics COVID-19 virus.