New study reveals why flu can be devastating for pregnant women
Pre-clinical study suggests virus does not stay in the lungs but spreads throughout the mother's body

Date:
September 22, 2020
Source:
RMIT University
Summary:
New research overturns current scientific thinking on flu infection
in pregnancy. The study helps explain why influenza can lead to
life- threatening complications during pregnancy. The research
also has implications for our understanding of how COVID-19 may
be affecting the vascular system.



FULL STORY ==========================================================================
New research helps explain why flu can lead to life-threatening
complications during pregnancy, suggesting the virus does not stay in
the lungs but spreads throughout the mother's body.


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The pre-clinical study has overturned current scientific thinking on
the reasons why flu infections affect pregnant women and their babies
so severely.

The findings could also help researchers working to understand the
fundamental biology of how COVID-19 spreads from the lungs into the body.

The research, in animal models, showed that during pregnancy flu spreads
from the lungs through the blood vessels into the circulatory system, triggering a damaging hyperactive immune response.

Led by RMIT University in collaboration with researchers and clinicians
from Ireland and Australia, the new study is published in the Proceedings
of the National Academy of Sciences.

Lead author Dr Stella Liong said the research suggests the vascular
system is at the heart of the potentially devastating complications
caused by influenza during pregnancy.



========================================================================== "We've known for a long time that flu can cause serious maternal and fetal complications, but how this happens has not been clearly understood,"
Liong, a Vice-Chancellor's Postdoctoral Fellow at RMIT, said.

"Conventional thinking has blamed the suppressed immune system that
occurs in pregnancy but what we see is the opposite effect -- flu
infection leads to a drastically heightened immune response.

"The inflammation we found in the circulatory system is so overwhelming,
it's like a vascular storm wreaking havoc throughout the body.

"We need further research to clinically validate our findings but
the discovery of this new mechanism is a crucial step towards the
development of flu therapies designed specifically for pregnant women." Professor John O'Leary, Trinity College Dublin, said the study represented
a landmark advance in our understanding of viral infections and pregnancy.



==========================================================================
"The discovery of an influenza-induced 'vascular storm' is one of the
most significant developments in inflammatory infectious diseases over the
last 30 years and has significant implications for other viral infections, including COVID-19," he said.

Understanding flu and pregnancy Influenza is not directly passed from
mother to baby, but its potentially devastating effect on the mother is
closely connected to the complications suffered by the baby.

Pregnant women who develop influenza are at higher risk of hospitalisation
with pneumonia and other complications, while babies of mothers severely affected by flu are at increased risk of fetal growth restriction,
miscarriage and preterm births.

Scientists have previously thought the reason flu has such serious health impacts is because the immune system is suppressed during pregnancy to
enable the fetus to thrive, making it harder to fight infections.

But the new research on Influenza A shows the virus behaves very
differently in the bodies of pregnant and non-pregnant mice.

In non-pregnant mice, the flu infection remains localised to the
lungs. But in pregnant mice, the virus spreads into the circulatory
system via the blood vessels.

This leads to intense inflammation that drastically affects the function
of large blood vessels, which severely impacts on the health of the
mother and can also restrict blood flow to the growing fetus.

Flu-induced vascular storm In the new study, researchers found pregnant
mice with flu had severe inflammation in the large blood vessels and
the aorta, the major conduit artery from the heart.

While a healthy blood vessel dilates 90-100% to let blood flow freely,
the flu- infected blood vessels functioned at only 20-30% of capacity.

Lead investigator Associate Professor Stavros Selemidis, RMIT, said even
a small change in the diameter of a blood vessel could have profound
changes to blood flow.

"We found a dramatic difference in these inflamed blood vessels, which
can seriously affect how much blood makes it to the placenta and all
the organs that help support the growing baby," Selemidis said.

"We've known that flu infection in pregnancy results in an increased
risk of babies being smaller and suffering oxygen starvation.

"Our research shows the critical role that the vascular system could be
playing in this, with inflammation in the blood vessels reducing blood
flow and nutrient transfer from mum to baby." While the researchers
did not directly measure blood flow, the study found an increase in
biomarkers for oxygen starvation in the fetuses of the flu-infected mice.

Why pregnancy makes a difference During pregnancy, the placenta secretes proteins and releases fetal DNA into the mother's blood, which can cause underlying inflammation.

The new study suggests the influenza infection may tip that underlying inflammation in the mother's body over the edge, into a full-blown
systemic inflammatory event.

Selemidis said the research also revealed a new connection to
pre-eclampsia, a dangerous pregnancy complication characterised by high
blood pressure.

"We found the same protein that is elevated in pre-eclampsia is also significantly elevated with flu," he said.

"While it will take further research to unpack this link, it could mean
drugs targeting vascular inflammation that are currently being tested
could potentially be repurposed in future for flu infection in pregnancy." Coronavirus connection Liong said the research also has implications
for our understanding of how the COVID-19 virus may be affecting the
vascular system.

"Flu and coronavirus are different but there are parallels and we do
know that COVID-19 causes vascular dysfunction, which can lead to strokes
and other cardiovascular problems," she said.

"Our studies in pregnancy offer new insights into the fundamental biology
of how respiratory viruses can drive dysfunction in the vascular system.

"This could be valuable knowledge for those scientists working directly on treatments and vaccines for COVID-19." The new study is the culmination
of over 10 years' work by researchers in the School of Health and
Biomedical Sciences at RMIT, leading a global collaboration.

The research was supported by an Australian Research Council (ARC)
Future Fellowship and funding from the National Health and Medical
Research Council of Australia (NHMRC).


========================================================================== Story Source: Materials provided by RMIT_University. Original written
by Gosia Kaszubska.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Stella Liong, Osezua Oseghale, Eunice E. To, Kurt Brassington,
Jonathan
R. Erlich, Raymond Luong, Felicia Liong, Robert Brooks, Cara
Martin, Sharon O'Toole, Antony Vinh, Luke A. J. O'Neill, Steven
Bozinovski, Ross Vlahos, Paris C. Papagianis, John J. O'Leary, Doug
A. Brooks, Stavros Selemidis. Influenza A virus causes maternal and
fetal pathology via innate and adaptive vascular inflammation in
mice. Proceedings of the National Academy of Sciences, Sept. 21,
2020; DOI: 10.1073/ pnas.2006905117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200921151321.htm

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