The nasal spray could prevent infections from any strain of the flu

An antibody nasal spray has shown promise for protection against the flu in preliminary human tests after first being tested in mice and monkeys. It may be useful in fighting future flu pandemics because it appears to neutralize any type of flu virus, including those transferred from non-human animals.

The main tool we have to stop the spread of the flu is the annual vaccine, which stimulates our immune system to make antibodies against recently circulating strains of the flu virus. However, because flu strains are constantly morphing, vaccines are only moderately effective.

To address this, the pharmaceutical company Johnson & Johnson has developed a special antibody called CR9114 that can neutralize any of these strains. It does this by recognizing and binding to a part of the virus that always remains the same, no matter how other parts of it change.

When CR9114 was initially injected into the bloodstream of animals, it failed to provide strong protection against influenza. This was because only a small fraction reached the nose, the main entry point for flu viruses. In 2022, Leyden Labs licensed CR9114 and developed a formulation that could be injected into the nose.

Since then, the company has shown that spraying CR9114 into the noses of mice and macaques prevents them from getting sick when exposed to different strains of influenza A and B, including one taken from a scientist’s throat during a bad flu season in 1933.

Preliminary tests were also carried out on 143 people between the ages of 18 and 55. The researchers found that administering the spray twice a day kept antibody levels stable in the participants’ noses and caused no major side effects. Samples of their nasal mucus taken afterwards also neutralized a number of flu strains, including the strain of bird flu that spread to humans in China in 2013.

The next step will be to directly expose people who have used the spray to a range of flu viruses to confirm that it actually prevents them from getting sick.

The spray may not be 100% effective because the virus can enter the body through routes other than the nose, such as the mouth, he says Linda Wakim at the University of Melbourne, Australia. “However, blocking entry into the nose would still trap the virus at the main access point for infection.”

It’s also likely to be less convenient than the flu vaccine because it requires twice-daily administration rather than a single jab, Wakim says. “However, it can be a game-changer for specific high-risk groups, such as immunocompromised individuals, frontline health care workers, or during a pandemic situation where rapid, short-term population protection is needed while vaccines are developed or introduced.”

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