Express News Service

BENGALURU: US researchers from Washington University School of Medicine in St Louis are trying out a Covid-19 vaccine that can be delivered through drops or spray through the nasal cavity. It has already been successfully tested on mice which were found to be protected against the SARS-CoV-2 virus that causes the dreaded disease. Once successfully tested on humans and certified, the vaccine is likely to be delivered on the lines of the polio vaccine, but through nostrils. 

Researchers thought of the nasal route as the nose is the initial site of Covid-19 infection. It was found to create a strong immune response throughout the body and was also found to be the most effective in the nose and respiratory tract.The team carried out the vaccine tests on mice via intramuscular injections, too, but discovered that those induced an immune response to prevent only pneumonia. They found that the vaccine via injections only reduced the severity of the infection, but did not completely prevent it from spreading throughout the body.

However, the nasal delivery of vaccine via drops or spray was found to prevent infection in both the upper and lower respiratory tracts — the nose and lungs — suggesting that vaccinated individuals would not spread the virus or develop infections elsewhere in the body. The study has been posted online in the journal Cell.

While developing this new vaccine, researchers at Washington University School of Medicine in St Louis inserted the SARS-CoV-2’s spike protein in a tweaked virus, an adenovirus that causes common cold, according to the university’s website. The spike protein is the weapon SARS-CoV-2 virus uses to attach to human host cells to destroy them. But in this case, when only the virus’ spike protein is inserted in the adenovirus that has been rendered harmless to ensure it does not cause sickness, the very presence of the spike protein triggers an immune response without causing any overt reactions.

The new vaccine also induces mutations in the spike protein to modify its shape that is most conducive to forming antibodies against it. Senior author of the study, Prof Michael S Diamond, the Herbert S Gasser Professor of Medicine and a professor of molecular microbiology, pathology and immunology, at the university, explained to The New Indian Express via e-mail that his team introduced two proline mutations to change the shape of the spike protein in a way to faster alert the neutralizing antibodies, which keep the SARS-CoV-2 virus at bay. ‘Proline mutations’ bend the viral protein structure to alert and mobilize the antibodies.

“We were happily surprised to see a strong immune response in the cells of the inner lining of the nose and upper airway — and a profound protection from infection with this virus,” Prof Diamond said in a release on the varsity’s website. “These mice were well protected from the disease (Covid-19). And in some of the mice, we saw evidence of sterilising immunity, where there is no sign of infection whatsoever after the mouse is challenged with the virus.” Prof Diamond told TNIE: “We are hoping to start human trials in the next few months. Completion is hard to predict exactly at this stage…(We are) as confident as one can be at this early stage. In other words, the mouse data is very promising. Nonetheless, we need to see that it works in humans similarly. We will be licensing this vaccine (once tested successfully) to companies that have more experience…”