Scientists have discovered why pregnant women are less likely to get the flu

Researchers from McGill University have found that pregnancy can trigger natural immunity, boosting the body's defences against severe forms of flu. Their work is published in the journal Science Advances.

The study on mice showed that pregnancy strengthens the immune system, preventing the influenza A virus from spreading to the lungs, where it can cause serious complications.

'Our results are surprising because they contradict conventional dogma, but from an evolutionary point of view it makes sense,' said study co-author Dr Maziar Diwangahi, a professor in the Faculty of Medicine and Health Sciences at McGill University. - The mother's body adapts to provide stronger defences to keep her baby healthy for development.

Scientists used a mouse model to study how a certain type of immune cells are activated in the nasal cavity during pregnancy. These cells produce a powerful molecule that boosts antiviral defences, especially in the nose and upper respiratory tract.

'The influenza A virus remains one of the deadliest threats to humanity,' emphasised the study's first author Julia Chronoulos, who conducted the research as part of her PhD thesis. - This natural immune enhancement during pregnancy may change the way we approach protecting expectant mothers from influenza.

Prospects for future vaccines and therapies

While Health Canada recommends that pregnant women get a flu shot because of the high risk of severe illness and complications, the new findings offer opportunities to develop more targeted vaccines against influenza, one of the top 10 leading causes of death in the country.

Study co-author Dr James Martin said: 'Our findings suggest that the immune response discovered can be replicated outside of pregnancy.

This could lead to new nasal vaccines or treatments that boost levels of protective molecules known as interleukin-17.

The team plans to focus on ways to reduce lung damage in viral infections such as influenza or COVID-19. Rather than directly fighting the virus, they aim to prevent the immune system from overreacting, which could reduce the risk of serious complications associated with the infection.

More details: Julia Chronopoulos et al, Pregnancy enhances antiviral immunity independent of type I IFN but dependent on IL-17-producing γδ + T cells in the nasal mucosa, Science Advances (2024). DOI: 10.1126/sciadv.ado7087