Lung Function of Pregnant Mice Is Unaffected Following Influenza Virus Infection

NIAID Now | January 25, 2019

Pregnant women are known to be more susceptible to infectious and non-infectious respiratory disease compared to non-pregnant women. Infection with influenza A (flu) viruses (IAV) in pregnant women results in more severe disease, especially in the third trimester of pregnancy, when pregnant women are more likely to be hospitalized and twice as likely to die from influenza-associated disease. Pregnancy is known to induce both anatomic and functional changes in pulmonary (lung) physiology, but little is known about how these changes affect the course of respiratory diseases.

NIAID-funded investigators used a mouse model to investigate how pregnancy affects the response to IAV infection. They examined the changes in pulmonary structure and function in pregnant and nonpregnant mice following IAV infection. Healthy pregnant mice had several features of enhanced pulmonary function compared with healthy nonpregnant mice. After IAV infection, both pregnant and non-pregnant mice showed reduced levels of the hormone progesterone. These lower progesterone levels were associated with features of reduced pulmonary function in nonpregnant mice. However, in pregnant mice the lower progesterone levels were associated with adverse pregnancy outcomes but did not significantly alter pulmonary function.

The mechanisms responsible for increased disease severity in pregnant women following IAV infection are unknown. This study showed that while pregnant mice display significant illness and death following IAV infection, there is no associated reduction in pulmonary function. Further, pregnant mice maintained the ability to mount sufficient antiviral responses to clear IAV infection. The findings suggest that lung-specific physiological and immune responses to IAV are not a major contributor to the increased disease severity seen during pregnancy.

Reference: Vermillion MS et al. Pregnancy preserves pulmonary function following influenza virus infection in C57BL/6 mice. American Journal of Physiology–Lung Cellular and Molecular Physiology. 2018 Oct 1;315(4):L517–L525.

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