32 SCIENCE NEWS | June 4, 2022
TOP ROW: KENZA ARABA; BOTTOM ROW: KENDALL SHAFFER; ALL: C.B. MORRISONET AL/PNAS2022SCIENCE VISUALIZED
Allergic asthma may have a small bright spot: The immune
system protein that triggers it may shield airway cells from
infection with SARS-CoV-2, the virus that causes COVID-19.
The finding helps explain why people with allergic asthma
seem less prone to the coronavirus than those with other
forms of asthma or related lung ailments.
Allergic asthma symptoms are triggered by allergens such
as pollen or pet dander. These allergens prompt a protein
called IL-13, which also helps the body fight off parasites,
to signal the lungs to churn out sticky mucus and constrict
airways. To see how IL-13 might help ward off SARS-CoV-2,
pathophysiologist Camille Ehre of the University of North
Carolina School of Medicine in Chapel Hill and colleagues
grew airway cells in lab dishes. Some cells were treated with
IL-13, and both treated and untreated cells were exposed to
the coronavirus.
Healthy cells resemble grasslands, with protrusions called
cilia sprouting from the cells’ tops. But after four days,
untreated cells exposed to the virus (top left) looked much
How allergic asthma helps protect against COVID-19
different. Infected cells inflated like a balloon, with bald spots
appearing as the cells died, the team reports in the April 19
Proceedings of the National Academy of Sciences. But cells
doused with IL-13 (top right) got infected less often, leaving
cilia lawns mostly intact, with far fewer balloons of dying cells.
IL-13 causes cells to churn out virus-trapping mucus. But
it also protects cells by altering gene activity. For instance, it
dials back production of the protein ACE2, which “makes it
much harder for the virus to find its door to enter the cells,”
Ehre says.
IL-13 also ramped up production of a protective carbohydrate
called keratan sulfate. Untreated cells (seen in cross section,
bottom left) made little keratan sulfate (pink) and got infiltrated
by the virus (green). Treated cells (bottom right) developed
a thick layer of the carbohydrate, armoring the cells so they
rarely got infected. In these images, cell nuclei are dark blue.
Which of these and other protective mechanisms is most
important, or if it’s a combination, is one of the many things
left to explore, Ehre says. — Tina Hesman Saey10 μm 10 μm10 μm 10 μm