Influenza A virus (IAV) is a major global health threat, with pandemic strains appearing periodically. Pregnant women, especially in their second and third trimesters, are more vulnerable to severe illness during influenza outbreaks. This heightened risk is linked to the immunocompromised state induced by pregnancy, which is necessary for the body to tolerate a semi-allogeneic fetus.
Pregnancy causes significant changes in the immune system, but the effects of these immune adaptations on respiratory responses to influenza and their influence on disease severity are poorly understood.
A new study by McGill University suggests that pregnancy may trigger a natural immunity to boost protection against severe flu infection. The study contradicts the commonly held belief that pregnancy increases vulnerability to infections and instead suggests that it strengthens an immune defense in mice, blocking the Influenza A virus from spreading to the lungs, where it can cause severe infection.
Co-lead author Dr. Maziar Divangahi, a Professor in McGill’s Faculty of Medicine and Health Sciences and Senior Scientist at the Research Institute of the McGill University Health Centre (The Institute), said, “Our results are surprising because of the current dogma, but they make sense from an evolutionary perspective.”
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“A mother needs to stay healthy to protect her developing baby, so the immune system adapts to provide stronger defenses. This fascinating response in the nasal cavity is the body’s way of adding an extra layer of protection, which turns on during pregnancy.”
In this study, the researchers used a mouse model to investigate how a specific type of immune cell activates in the nasal cavity during pregnancy. This activation produces a potent molecule that enhances the body’s antiviral defenses, particularly in the nose and upper airways.
First author Julia Chronopoulos, who carried out the research while completing her PhD at McGill, said, “Influenza A virus remains among the deadliest threats to humanity. This natural immunity in pregnancy could change how we think about flu protection for expectant mothers.”
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The new findings offer potential for developing more targeted influenza vaccines, especially given that influenza is one of Canada’s top 10 leading causes of death. The research suggests that the immune response observed during pregnancy could be replicated in the broader population. This could lead to the creation of new nasal vaccines or treatments that boost protective molecules, such as Interleukin-17, to enhance antiviral defense.
Journal Reference:
- Julia Chronopolous, Erwan Pernet, Kim Tran 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. DOI: 10.1126/sciadv.ado7087