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Zika Virus Exploits Pregnant Women's Immune Systems to Infect & Replicate

SEP 05, 2017 | KRISTI ROSA

New research from the Keck School of Medicine at University of Southern California (USC) has found that the Zika virus—known for causing devastating birth defects such as microcephaly in newborns—targets specific white blood cells to suppress pregnant women’s immune systems, which allows it to spread.

The virus works to “handicap” the immune system in a way comparable to HIV, senior study author Jae Jung, distinguished professor and chair of the Department of Molecular Microbiology and Immunology at the Keck School of Medicine, noted in a recent press release.

“Pregnant women are more susceptible to the Zika virus because pregnancy naturally suppresses a woman’s immune system so her body doesn’t reject the fetus—essentially it’s a foreign object,” Dr. Jung explained. “Our study shows pregnant women are more prone to immune suppression. Zika exploits that weakness to infect and replicate.”

Even though it is known that pregnant women have increased susceptibility to infection and the fear of microcephaly and other associated birth defects is what has researchers desperate to develop a vaccine, Dr. Jung pointed out that none of the phase 1 clinical trials for Zika vaccine candidates have included this population thus far.

“The Zika virus vaccines in development seem to be highly effective, but they’re being tested among non-pregnant women with different body chemistry compared to pregnant women,” Dr. Jung commented. “It’s feasible the recommended vaccine dose—thought effective for non-pregnant women—may not be potent enough for pregnant women because their bodies are more tolerant of viruses.”

In an experiment, they infected blood samples that had been collected from non-pregnant women and pregnant women with African and Asian strains of the virus. At peak infection, the researchers found that the virus targeted specific white blood cells known as CD14+ monocytes that go on to turn into macrophages, which are “trash bags that swallow viruses, bacteria, and cellular debris to make the body healthy,” according to the press release. Furthermore, they found that the Asian strain in particular “pushed” these white blood cells to become M2 macrophages that essentially deliver a false message to the immune system that the threat is over, which allows the virus to replicate.

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