According to the CDC infants under six months face the highest risk of hospitalization from influenza A due to their immature immune systems. Infections at this age can lead to severe complications such as brain inflammation developmental delays and long-term conditions like diabetes asthma allergies and cognitive impairments.

Dr. Ying Fang a pathobiology professor at the University of Illinois Urbana-Champaign emphasized that vaccination during pregnancy is the most effective way to protect newborns. Alongside Dr. Christopher Gaulke who studies the microbiome’s role in health Dr. Fang is developing a new influenza A vaccine a version of which was used in pregnant sows during their study.

While earlier studies have linked disease-related changes in the gut microbiome to altered brain gene expression most of this research has focused on adults.

We’re the first to use a neonatal piglet model to explore how the microbiome interacts with brain gene function said Dr. Ying Fang. Pigs are ideal for studying human infections due to their physiological similarities and susceptibility to many of the same zoonotic viruses.

The team concentrated on the hippocampus drawing on the expertise of Dr. Adrienne Antonson an animal sciences professor who studies the prenatal origins of neurodevelopmental and behavioral disorders. Her previous work showed that viral infections during pregnancy can impair hippocampal development in piglets.

Dr. Christopher Gaulke added that the microbiome plays a crucial role in brain development. Studies have consistently shown its importance especially in early life. Disrupting the microbiome in animal models can lead to negative effects including neurocognitive issues he said.

In this new study researchers compared changes in the microbiome and hippocampal gene expression among piglets born to vaccinated and unvaccinated sows after exposure to the influenza A virus. A third group uninfected piglets whose mothers received a mock vaccine served as the control.

The results revealed clear differences in both nasal and gut microbiota as well as in hippocampal gene expression. Although health-promoting microbes increased in all groups following infection the rise was less pronounced in piglets from unvaccinated mothers. These piglets also showed a greater surge in potentially harmful microbes especially in the nasal passages. Notably nasal microbiome changes were most strongly linked to altered gene activity in the hippocampus.

We already knew that flu infections during pregnancy or early life can harm infant brain development and that the microbiome plays a key role in that process said Dr. Gaulke. But our study is the first to connect all these elements using a neonatal model.

The researchers concluded that maternal vaccination can help reduce the negative impact of influenza infection on both the microbiome and brain development in newborns. They emphasized the need for further research to uncover how flu-related microbiome changes may influence brain health.

Source: https://vetmed.illinois.edu/2025/07/01/influenza-microbiome-brain-gene-expression/