New experimental coronavirus vaccine imposes 90-fold antibody levels in mice

An experimental vaccine helped prevent serious illness in mice infected with the new coronavirus, a new study says.

Researchers found that five weeks after immunization, after the rodents were exposed to COVID-19, there were no detective virus particles in their lungs.

What’s more, after two doses, the levels of neutralizing antibodies in mice were boosted by 90-fold, the team, of Washington University School of Medicine in St. Louis, found.

Mice received one dose of an experimental jab that combined coronavirus and another virus had high levels of neutralizing antibodies, but those given two doses increased their levels 90-fold. Image: Leyda Valentine takes Lisa Taylor’s blood as she shares a COVID-19 vaccination study at Research Centers of America on August 7, in Hollywood, Florida

After injecting the virus into the noses of the mice, those who became immune did not develop pneumonia or had high levels of particles in their lungs. Image: Leyda Valentine (left) takes Lisa Taylor’s blood (right) during a trial of a coronavirus vaccine in Florida, August 7

‘Unlike many of the other vaccines that have been developed, this vaccine is made from a virus that can spread in a limited way in the human body, which means it is likely to generate a strong immune response,’ said co- senior author Dr. Michael Diamond, a professor of molecular microbiology, pathology and immunology.

‘Since the virus is able to replicate, it can grow to high levels in the lab, so it is easy to scale up and should be more cost effective than some of the other vaccine candidates. ‘

For the study, published in the journal Cell Host and Microbe, the team is genetically modified vesicular stomatitis virus (VSV), which causes a mild disease in animal husbandry.

Researchers removed one gene from VSV and inserted the spike protein of SARS-CoV-2, which uses the virus to infect human cells.

They named the hybrid virus VSV-SARS-CoV-2, which they hope to raise antibodies against the spike protein and protect against later infection.

This is the same strategy that was used to develop the Ebola vaccine – made from VSV and inserted with an Ebola gene – that was approved in 2019 by the US Food and Drug Administration.

Subsequently, mice were injected with the experimental vaccine, and a subgroup received a second jab four weeks later.

Three weeks after each injection, the researchers drew blood to test for antibodies.

Results showed high levels of antibodies after one dose, but the group receiving a second dose had their levels 90-fold.

The researchers then injected COVID-19 into the mice’s noses five weeks after their last shot.

Four days after the mice were exposed to the virus, after one or two doses there were no detectable particles in their lungs, nor any pneumonia.

In comparison, rodents given a placebo had high levels of the virus in their lungs and more signs of inflammation.

While the data are promising, this experimental vaccine is still in the early stages of development and much more testing for safety and effectiveness is needed.

“It will really depend on how successful the first vaccines that come for COVID are,” said co-senior author Dr. Sean Whelan, head of the Department of Molecular Microbiology, at Washington University School of Medicine.

‘If they do not produce a robust, sustained immune response when there are safety concerns, there may be a chance for a second-generation vaccine that can induce sterilizing immunity and stop the cycle of transmission.’