Nasal spray found to protect ferrets from Covid-19

NEW YORK • A nasal spray that blocks the absorption of the Sars-CoV-2 virus has completely protected ferrets it was tested on, according to a small study released on Thursday by a team of scientists.

The study, which was limited to animals and has not yet been peer-reviewed, was assessed by several health experts at the request of The New York Times.

If the spray, which the scientists described as non-toxic and stable, is proved to work in humans, it could provide a new way of fighting the pandemic. A daily spritz up the nose would act like a vaccine.

"Having something new that works against the coronavirus is exciting," said Dr Arturo Casadevall, chairman of immunology at the Johns Hopkins Bloomberg School of Public Health, who was not involved in the study. "I could imagine this being part of the arsenal."

The work has been under way for months by scientists from Columbia University Medical Centre in New York, Erasmus Medical Centre in the Netherlands, and Cornell University in Ithaca, New York. The team would require additional funding to pursue clinical trials in humans.

The spray attacks the virus directly. It contains a lipopeptide, a cholesterol particle linked to a chain of amino acids, the building blocks of proteins. This particular lipopeptide exactly matches a stretch of amino acids in the spike protein of the virus, which the pathogen uses to attach to a human airway or lung cell.

Before a virus can inject its RNA into a cell, the spike must effectively unzip, exposing two chains of amino acids, in order to fuse to the cell wall. As the spike zips back up to complete the process, the lipopeptide in the spray inserts itself, latching on to one of the spike's amino acid chains and preventing the virus from attaching.

"It is like you are zipping a zipper but you put another zipper inside, so the two sides cannot meet," said microbiologist Matteo Porotto from Columbia University and one of the paper's authors.

The work has been submitted to the journal Science for peer review.

In the study, the spray was given to six ferrets, which were then divided into pairs and placed in three cages.

Into each cage also went two ferrets that had been given a placebo spray and one ferret that had been deliberately infected with Sars-CoV-2 a day or two earlier.

Ferrets are used by scientists studying flu, severe acute respiratory syndrome (Sars) and other respiratory diseases because they can catch viruses through the nose like humans do, although they also infect each other by contact with faeces or by scratching and biting.

After 24 hours, none of the sprayed ferrets caught the disease; all the placebo-group ferrets did. "Virus replication was completely blocked," the authors wrote.

The protective spray attaches to cells in the nose and lungs and lasts about 24 hours, Dr Anne Moscona, a paediatrician and microbiologist at Columbia and co-author of the study, said.

"If it works this well in humans, you could sleep in a bed with someone infected or be with your infected kids and still be safe," she said.

The amino acids come from a stretch of the spike protein in coronaviruses that rarely mutates. The scientists tested it against four different variants of the virus, including both the well-known "Wuhan" and "Italian" strains, and also against the coronaviruses that cause Sars and the Middle East respiratory syndrome (Mers).

In cell cultures, it protected completely against all strains of the pandemic virus, fairly well against Sars and partially against Mers.

The lipoprotein can be inexpensively produced as a freeze-dried white powder that does not need refrigeration, Dr Moscona said. A doctor or pharmacist could mix the powder with sugar and water to produce a nasal spray.

Australian scientists have tested a nasal spray against Covid-19 in ferrets, but it works by enhancing the immune system, not by targeting the virus directly.

As lipopeptides can be shipped as a dry powder, they could be used even in rural areas in poor countries that lack refrigeration, Dr Moscona said.

NYTIMES